OPEN HEART SURGERY: RESULTS IN 600 - Thorax · OPEN HEART SURGERY: RESULTS IN 600 CASES* BY HERBERT SLOAN, JOE D. MORRIS, JAMES MACKENZIE, AND AARON STERN From the Department of Surgery

Thorax (1962), 17. 128.

OPEN HEART SURGERY: RESULTS IN 600 CASES*BY

HERBERT SLOAN, JOE D. MORRIS, JAMES MACKENZIE, AND AARON STERN

From the Department of Surgery (Section of Thoracic Surgery) and the Department of Paediatrics,University of Michigan, Ann Arbor, Mich.

(RECEIVED FOR PUBLICATION FEBRUARY 24, 1962)

The use of extracorporeal circulation during thesurgical correction of heart lesions has becomegenerally accepted. Comprehensive discussions ofthe problems of open heart surgery have beenpublished (Clowes, 1960; Harley, 1960; Allen,1958). A variety of methods and techniques havebeen developed for operating on the heart underdirect vision, and those that are now in wide useachieve excellent results (DeWall and Lillehei,1962; Drew, 1961; Gerbode, Osborn, andJohnston, 1960; Molloy, 1961). By the end of1961 open heart operations for acquired andcongenital cardiac lesions had been performed on600 patients at the University of Michigan MedicalCenter. A safe, easily controlled procedure formaintaining extracorporeal circulation has beendeveloped which is based on a rotating discoxygenator and a means for inducing moderatesystemic hypothermia. The programme of openheart surgery began in 1957 (Sloan, Morris,vander Woude, Hewitt, and Long, 1959), and themethods now in use represent developmentthroughout the past four years. The risk in openheart surgery to-day is related almost entirely tothe severity of the cardiac lesion rather than to theuse of extracorporeal circulation. The mortalityrate for correction of uncomplicated cardiacdefects is less than 1 % in our hands.

PERFUSION TECHNIQUEThe equipment for extracorporeal circulationt

consists of a receiving chamber, a rotating discoxygenator, occlusive roller pumps for arterial per-fusion and aspiration of blood from the heart, a heatexchanger, and a bubble trap (Figs. 1 and 2). Thereis no filter in the circuit. Tygon tubing is used toconnect the elements of the extracorporeal circulationto each other and to the patient. All parts of theunit can be autoclaved. Blood is removed from thebody by gravity drainage with catheters or metalcannulae placed through the right atrium into thevenae cavae. The oxygenated blood is returned to*Supported by grants from the Michigan Heart Association.t Constructed by Edward A. Olson Co., Ashland, Mass., and

Sarns, Inc., Ann Arbor, Mich.

the body through a metal cannula in the leftsuperficial femoral artery.The disc oxygenator is the result of an effort to

develop an instrument combining efficiency withsimplicity of design (DeWall, Grage, McFee, andChiechi, 1962). A half cylinder seamless steel pan8 cm. in diameter serves as a reservoir for the blood.The pan is covered by an autoclavable plastic canopy(Lexan). The stainless steel discs, 12.5 cm. in diameterand 0.5 mm. in thickness, are mounted on a hexagonalshaft to prevent slipping of the discs and are separatedby spacers 4.5 mm. thick. The shaft rests onmovable outboard bearing mounts attached to theends of the oxygenator pan. Micrometer adjustmentof the bearings allows the clearance between discsand pan surface to be varied during operation inorder to avoid turbulence which may occur with highblood flows through the oxygenator. The outlet trapof the oxygenator is a 5 cm. cylinder extendingvertically below the pan surface; the outflow leadsoff at a right angle from this cylinder. A majoradvantage of the oxygenator design is the ease withwhich it can be dismantled and cleaned. Every partcan be reached without difficulty. All surfaces arehighly polished and both corners and seams havebeen eliminated.Three sizes of oxygenators with interchangeable

bearing mounts provide for adequate oxygenation inany clinical circumstance. A small oxygenator of32 discs is employed for infants up to 10 kg. in weight.This has been combined with a miniaturized receivingchamber and a heat exchanger having a total primingvolume of 1,500 ml. The medium oxygenator of 80discs for children and small adults is incorporated ina system having a priming volume of 3,200 ml. Theadult perfusion equipment, with an oxygenator of105 discs, requires 4,300 ml. for priming. Reservecapacity in the extracorporeal system is desirable inorder to meet the sudden demands for blood whichmay occur during heart-lung bypass. All these unitsare compatible with the basic pumping unit. Thesmall oxygenator will perform satisfactorily withflow rates up to 1.5 1. per minute, the medium unitat 3 1. of blood per minute, and the large unit at5 1. per minute.The gas mixture employed in the oxygenator is

98% oxygen and 2% carbon dioxide. Fluothane issupplied directly to the oxygenator during the per-

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FIG. 1

FIG. 1.-Top view of extracorporealcirculation.

FIG. 2.-Extracorporeal circulationassembled for perfusion in in-fants with miniaturized receivingchamber, rotating disc oxygena-tor, and combined heat ex-changer and bubble trap.

FIG. 2



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130 HERBERT SLOAN, JOE D. MORRIS, JAMES MACKENZIE, and AARON STERN

fusion from a vaporizer mounted on the side of thepumping unit. The discs are rotated at a rate of 100revolutions per minute, but may be slowed to 80revolutions per minute when hypothermic levels arereached.The receiving chamber is set 20 to 30 cm. below

the patient's heart and blood is delivered from thisinto the oxygenator. Blood aspirated from the heartis returned to the upper portion of the receivingchamber where bubbles are removed by allowing theblood to flow over plastic sponges coated lightly withAntifoam A. A torpedo-type heat exchanger is usedin the infant unit and a Brown-Harrison heatexchanger in the units for children and adults.Nylon rods are inserted in the channels of the Brown-Harrison heat exchanger when the medium unit isemployed to improve the efficiency of the unit and toreduce the priming volume.

Heparinized blood for the extracorporeal circuit isdrawn on the morning of operation whenever possible.Some use has been made of blood drawn the preced-ing afternoon to which 1 ml. of 50% glucose hadbeen added before use. Under emergency conditionsACD blood is converted for use in the extracorporealcirculation by adding 25 mg. of heparin followed by6 ml. of 10% calcium chloride to each 500 ml. ofblood (Foote, Trede, and Maloney, 1961).The heart is exposed through a median sternotomy

incision, although a right lateral thoracotomy isneeded if the mitral valve is to be exposed. Thevenae cavae and the aorta are isolated within thepericardium. The heart is examined and a searchmade for additional abnormalities. Heparin in adose of 3 mg. per kg. of body weight is injected intothe right atrium and during the perfusion anadditional one-third dose of heparin is injected intothe extracorporeal circuit at 45-minute intervals. Theheparin is neutralized at the end of the perfusion byan equivalent amount of Polybrene (hexadimethrine),and an additional half-dose of Polybrene is given 30minutes after the perfusion is completed.Cannulae are placed through the right atrium into

the venae cavae. The venous cannulae vary in sizefrom an internal diameter of 4.3 mm. for infantsto 9.4 mm. for adults. The cannula for arterial returnis directed centrally in the left superficial femoralartery. A 2 mm. arterial cannula is satisfactory forinfants and graded sizes up to a 5 mm. cannula foradults are employed. The appropriate connexionswith the extracorporeal circulation are made.

Perfusion is begun on parallel and soon shifted tototal heart-lung bypass. The cardiotomy is performedonly when the perfusion is stable and an adequateblood pressure is maintained. The majority of per-fusions are combined with moderate whole bodyhypothermia at oesophageal temperatures of 28' to300 C. Surface cooling is started with a watermattress at the beginning of the operation. The bodytemperature of most patients has reached 32' to 34'C. by the time preparations for heart-lung bypassare made. Additional cooling is accomplished easily

with the heat exchanger while the intracardiac lesionis exposed and examined. Intermittent aortic occlusionof not more than eight to ten minutes at a time isemployed when necessary to improve exposure of thelesion. For more difficult operations the oesophagealtemperature is lowered to 20' C. or below, allowingperiods of complete interruption of the circulation.Rewarming with both the heat exchanger and the

water mattress starts when the intracardiac repairis complete and the perfusion is discontinued atoesophageal temperatures of 35' to 37' C. and rectaltemperatures of 32' to 34' C. When ventricularfibrillation occurs during hypothermia, spontaneousdefibrillation is frequently seen when the blood per-fusing the heart reaches a temperature of 30' C. Asingle electric shock will defibrillate the heart whenspontaneous defibrillation does not occur.Moderate whole body hypothermia during perfusion

has resulted in improved exposure because thepulmonary venous and coronary sinus blood return-ing to the heart is greatly reduced. There is also lesstrauma to the blood in long perfusions and the post-operative condition of the patients is improved,although this may be the result of increased experi-ence with techniques rather than the use of hypo-thermia alone. Decompression of the left side ofthe heart has largely eliminated pulmonary congestionfollowing perfusion. This is accomplished throughan aspirating tip placed in the pulmonary artery whenthe right ventricle is opened, or by a sump placedin the left atrium or left ventricle. The lungs arekept half-inflated with oxygen during perfusion, butthey are not ventilated.Flow rates during perfusion are sufficient to

maintain a mixed venous oxygen saturation of 7000,although this may not be a valid indication ofadequate oxygenation under hypothermic conditions.Relatively high flow rates are considered important,and these are maintained at two-thirds to three-quarters of the minimum calculated flow rates atnormal temperatures (Gollan, 1959) (Fig. 3). In thepresence of aortic insufficiency or large bronchialflows, perfusion rates are increased. A mean bloodpressure of 80 to 100 mm. Hg is consistently main-tained. Most perfusions are continued for 30 minutesto one hour, but in some cases the perfusions have

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FIG. 3.-Flow rates in 50 perfusions with moderate hypothermiacompared with calculated adequate perfusion rates at 30' and38' C. (Gollan, 1959).

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OPEN HEART SURGERY

been successfully prolonged for more than threehours.

Careful monitoring of the patient's physiologicalcondition during the perfusion is considered essen-tial. The electrocardiogram and electroencephalo-gram are recorded. Arterial and venous pressuresare measured through small polyethylene cathetersplaced in the right femoral artery and saphenous vein.Oesophageal and rectal temperatures are recorded aswell as the temperature of the arterial blood enteringthe patient. Oxygen saturations of arterial and mixedvenous blood are determined intermittently duringthe perfusion.The amount of blood introduced into the extra-

corporeal circulation is measured accurately and theamount remaining at the end of the perfusion ismeasured again. Blood lost during operation iscalculated by collecting all blood aspirated by weigh-ing sponges and by estimating blood loss on thesurgical drapes. These values, together with theamount of blood administer2d intravenously, allowan immediate estimate of the patient's loss andreplacement. This method of determining bloodbalance has proved satisfactory, so patients need notbe weighed after operation. Venous pressures arefollowed carefully during and after perfusion, butcontinuing, accurate information about loss andreplacement and careful monitoring of blood levelsin the oxygenator provide more sensitive informationabout the blood volume of the patient before, during,and after perfusion. It is, of course, consideredextremely important that the perfusion be completedwith the patient's blood volume unchanged.A large number of acid-base studies were carried

out early in our experience during high flowperfusions at normal temperatures. The patientsdeveloped respiratory alkalosis combined with mildmetabolic acidosis. The degree of acidosis presentwas comparable to that found in patients undergoingthoracic operations without perfusion, and the returnto normal acid-base balance was prompt (Taylor,Theye, Devloo, and Kirklin, 1962). Similar studieshave been carried out during perfusion at the

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FIG. 4.-Comparison of acid-base changes during perfusions underconditions of normothermia and moderate hypothermia.

temperature levels employed now, 280 to 300 C. (Fig.4), and the results have been about the same whenthe values are corrected for the patient's temperature(Bradley, Stupfel, and Severinghaus, 1956; Trede,Foote, and Maloney, 1961). The present techniqueof perfusion supplies adequate amounts of oxygen tothe tissues. Metabolic acidosis of significant degreedoes not occur and it is not necessary to add baseduring the perfusions.

SELECTION OF PATIENI SCONGENITAL DEFECrS.-A congenital cardiac

lesion should be repaired, if possible, wheneverit poses an actual or potential threat to life whichis greater than the risk entailed in surgicalcorrection. Our experience indicates that opti-mum results may be expected if the patient isbetween 3 and 5 years old when the defect isinvestigated and corrected. In our series it hasproved safe to carry out open heart surgery atthis age. The child does not have to enter schoollabelled as a "cardiac " with the attendantlimitation of activity and psychological trauma.More important is the fact that the earlier thedefect can be corrected, the greater chance thechild has to achieve his full growth potential(Engle, Holswade, Goldberg, and Glenn, 1958).The debate about the advisability of operation

to correct congenital lesions in small children hascentred largely on the surgical closure of ventri-cular septal defects. There has been little doubtabout the necessity for operation in patients witha large ventricular defect associated with markedlyincreased pulmonary blood flow or significantpulmonary hypertension. Many physicians believesmaller defects may safely be left alone (Lancet,1961). Patients with little or no pulmonary hyper-tension in infancy do not tend to developincreasing pulmonary artery pressures duringchildhood, and the natural history of ventriculardefects in adult life is not completely defined(Lucas, Adams, Anderson, Meyne, Lillehei, andVarco, 1961). Spontaneous closure of ventriculardefects has been known to occur in rare cases, butevidence of probable closure is usually presentbefore the infant is 2 years old as shown by amarked diminution in the intensity of the murmurand size of the heart.

It is our practice to advise closure of anyventricular defect, just as we would advise closureof a patent ductus arteriosus, believing the risksof operation to be much less than the risk of theuncorrected defect.An important reason for correcting ventricular

septal defects is the danger of subacute bacterialendocarditis. Among approximately 380 patients

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with uncorrected ventricular defects seen at theUniversity of Michigan Medical Center, therewere 19 patients who developed bacterial endo-carditis. Fourteen of the patients recoveredfollowing antibiotic therapy, two patients died, andthree patients had increased damage to the heartfrom the infection. This is considered a minimalinfection rate since many of the patients werenot followed after the diagnosis of ventriculardefect had been established. As far as is known,there is no recorded instance of bacterial endo-carditis in a surgically closed ductus arteriosus,and examination of hearts after closure of aventricular defect has suggested that the endo-thelial covering of the sutures and prostheses willprovide the same protection. Patients with closedventricular defects, however, have not as yet beenfollowed long enough to warrant the conclusionthat a complicating bacterial endocarditis isimpossible.Complete heart block has not been a significant

hazard of operation for ventricular defects. Inour group of 194 patients with such defects, onechild has a permanent heart block followingclosure of a ventricular defect. The child hadsevere pulmonary hypertension for which a pre-vious banding procedure had been done. Asecond child with severe pulmonary hypertensionhad complete heart block and died suddenly themorning after operation. Residual left-to-rightshunts are now so rare that we do not considerthat the possibility of this complication shouldmilitate against a decision to close a ventriculardefect.A review of the growth patterns of children

one to two years after the closure of a smallventricular defect showed graphic improvement inboth height and weight in one-half of them,although the defects closed were only 3 mm. to6 mm. in diameter. This was apparent in children3 to 5 years old, but was more striking in children6 to 12 years old.

It is surprising to hear the comments of parentswhose children have undergone surgery for whatwas presumed to be an asymptomatic cardiaclesion. Although many of the children seemednormal before operation, the parents havedescribed enthusiastically the increased activitytheir children have shown after operation.The same indications for operation are observed

in patients with such lesions as atrial septal defectand pulmonary stenosis, although the dangers ofbacterial endocarditis are much less for patientswith atrial defects. The mortality rate fromoperation in such uncomplicated congenitalabnormalities has been less than I %.

It has seemed desirable to avoid operation, ifpossible, on children less than 2 years old.Perfusion has proved more difficult in theseinfants, although increasing experience has madeheart-lung bypass practicable for those whosecardiac lesions require operation in order that theymay survive. In our 600 patients undergoing openheart surgery, 56 were less than 2 years old.Surgery has always been considered for the childwith an operable cardiac lesion when it is believedthat otherwise he will not survive, but wheneverpossible the operation is postponed until the childhas grown to a more acceptable size. However,death has occurred in some patients waiting foroperation, while operation has salvaged many ofthese infants.

Successful open heart operations cannot becarried out on patients with severe pulmonaryhypertension in whom there is a right-to-left shuntand in whom systemic flow is greater thanpulmonary flow. The infant with tetralogy ofFallot who requires an operation is best treatedby a shunt procedure or by infundibular resection,complete correction being postponed until a laterdate. When the tiny infant with pulmonary valvestenosis requires operation, a transventricularvalvulotomy is done.

ACQUIRED DEFECTS.-The selection of casessuitable for surgical treatment of acquired heartdisease presents a greater problem. All sympto-matic valvular lesions, which are multiple in manypatients, deserve to be considered for correctionby the open heart technique. Success or failurewill be determined by the myocardial reservepresent, provided improvement in valve functioncan be obtained by operation. The majority ofthese patients have mitral or aortic valve disease.Correction of all complicated mitral valve lesionsunder direct vision with extracorporeal circulationis now indicated, particularly when mitralinsufficiency is present (Morris, Sloan, Wilson,and Brandt, 1962). Most second operations formitral stenosis are performed with the help ofheart-lung bypass. It is still our practice to employtransventricular dilatation of the mitral valve inall patients with pure, uncomplicated mitralstenosis. The use of coronary perfusion and localhypothermia during operation on the aortic valvehas made careful, planned repair of aortic valvelesions possible (Kay, Nogueira, Suzuki, Postigo,and Mendelsohn, 1961).While techniques for supporting the circulation

and exposing the aortic, mitral, and tricuspidvalves are available, correction of acquired heartdisease is frequently more difficult than correction



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of congenital cardiac lesions. It follows that theresults of operation for acquired heart diseasehave not been as dramatic as those for congenitalheart disease. Despite this, the use of heart-lungbypass has significantly improved the results ofoperation for acquired heart disease, andcontinuing progress is being made.

PROBLEMS IN POST-OPERATIVE CAREThe successful correction of cardiac defects with

the aid of extracorporeal circulation depends asmuch on the care the patients receive after theoperation as on the skill employed during theperfusion. In our hospital post-operative care iscarried out in a unit equipped and staffed to meetthe special problems of patients who haveundergone a cardiac operation. A pattern of carehas been developed which offers maximumsupport to the patient and gives prompt warningof impending complications. The problemsencountered in our patients after open heartsurgery have been concerned with ventilation andtracheobronchial secretions; blood and fluidreplacement; circulatory failure; disturbances ofheart rhythm; cerebral damage; disturbancesof the acid-base balance; and infection andunexplained fever.VENTILATION AND TRACHEOBRONCHIAL SECRE-

TIONS.-Pulmonary secretions increase after openheart surgery, although pulmonary complicationshave become less frequent since the importanceof decompressing the left side of the hearthas been recognized. Recognition of retainedbronchial secretions by physical examination isdifficult. Portable chest radiographs, however,supply information which cannot be obtained byphysical examination, and such examinations aremade in the operating room and during theevening on the day of operation. Additionalexaminations are made on each of the next threedays.

Patients are placed in an oxygen tent with highhumidity. Assisted voluntary coughing is carriedout at regular intervals; this has seemed moreeffective since the technique of median sternotomywas adopted. Intratracheal suction is a valuableaid in clearing the tracheobronchial tree. In asmall child it is not possible to enter the trachearoutinely, but pharyngeal stimulation usuallyproduces effective involuntary coughing. Persis-tent but unsuccessful attempts to aspirate thetrachea are tiring to both patient and staff andit is necessary to balance the use of this valuableadjunct against the patient's need for adequaterest. Bronchoscopy has not been employed inour cases. In infants, exposure of the larnyx and

direct aspiration of the trachea with a rubber-tipped sucker has been of value. Most infantsand small children prefer to sleep prone or inthe knee-chest position and will tolerate thisprocedure quite well. Every effort is made topromote bronchial drainage by this means.Tracheostomy is seldom necessary but is resortedto when secretions are not well controlled byroutine means or when mechanical ventilationis necessary to maintain adequate respiratoryexchange.

BLOOD AND FLUID REPLACEMENT.-Restorationof the clotting mechanism is a fundamentalrequirement for successful perfusion. Polybrene(hexadimethrine) has proved a satisfactory drugfor this purpose; post-operative bleeding as aresult of clotting defects has been rare even afterprolonged perfusions. Pre-operative bleeding,clotting, and prothrombin times are determinedroutinely; no other evaluation of the clottingmechanism has been necessary in this series whenthese values have been normal and there has beenno history of bleeding.To establish drainage the pericardium is closed

loosely, the right pleural cavity opened widely, anda thoracotomy tube placed in the right pleuralcavity. In some cases the pleural cavities have beenleft intact, the mediastinum alone being drained.When the patient is returned from the operatingroom his blood volume is approximately normal.Thereafter the amount of drainage from the chestis measured each half-hour; calibration of thethoracotomy jugs facilitates this measurement.The drainage fluid is replaced volume for volumeby fresh whole blood. Continued rapid blood loss,particularly if undrained blood collects in thechest, is an indication for re-exploration if theclotting mechanism is normal. In the few patientswho have required re-exploration inadequatehaemostasis has been the most frequent cause ofthe bleeding. Immediate exploration of the chestwith evacuation of the haematoma and controlof the bleeding has been followed by astonishingimprovement in the patient's condition. Drainagefluid from the chest becomes serous in 12 hoursin most patients; the volume corresponds to thedrainage from a thoracic operation without aperfusion.

In our series significant anaemia has not beenobserved in the post-operative period. There isslight haemoconcentration in the first 48 hourswhich is diluted as fluid intake increases. Thishaemoglobin level is maintained until the patient'sdischarge ten days to two weeks after operation.Some adult cardiac patients with complicated

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defects have had abnormalities of blood volumebefore and after operation. Measurements ofblood volume are helpful in the post-operativecare of such patients (Carr, Sloan, and Tovar,1960). Daily recording of the patient's weightassures recognition of fluid retention andimpending heart failure in patients who areconsidered liable to such complications.

After operation the patient's blood pressure,pulse rate, and respiratory rate are recorded at15-minute intervals for the first eight hours andthen at decreasing intervals until the patient hasreturned to the open ward. Most patients haverequired no other special observation.

Limitation of fluid intake has contributed to thereduction in pulmonary complications (Sturtz,Kirklin, Burke, and Power, 1957). Fluid intakeis based on weight rather than surface areabecause surface-area standards in children are notreliable (Oliver, Graham, and Wilson, 1958). Thepatient is allowed 40 to 55 ml. of fluid per kg. ofbody weight during each of the first two 24-hourperiods after the operation. The ACD solutionin the citrated blood administered during and afterthe operation is included as part of the fluidrequirement. Ice chips and small amounts offluid are allowed by mouth on the day of operationand as much of the total fluid as the patient cantolerate is given by mouth on the day after theoperation. Any deficit in fluid intake is madeup by the intravenous administration of 5%glucose in 0.2% sodium chloride solution. Fluidrestrictions are removed on the third post-operative day unless pre-existing heart failuremakes continued limitation advisable.Most patients void a small amount of concen-

trated urine on the day of operation. Diuresisoccurs on the day after the operation and there-after the urine output is normal. In our seriestemporary renal shutdown as a result of perfusionhas been seen in three patients only.CIRCULATORY FAILURE.-The state of the

patient's peripheral circulation is considered themost sensitive index of his condition after acardiac operation. The oxygen tent, desirable asit is for providing moisture and oxygen, interfereswith careful observation of the patient. A nasalcatheter or face mask seems undesirable sincethese methods of oxygen administration makehandling of pulmonary secretions more difficultand children tolerate them poorly. " Foot rounds,"however, have proved to be a simple, accuratemeans of observing the peripheral circulation.When the feet are pink and warm and the dorsalveins of the feet filled, it seems likely that adequate

oxygenation and cardiac output are beingmaintained by the patient. The use of indwellingcatheters to follow arterial, central venous, andpulmonary artery pressures and to measure mixedvenous oxygen saturation provides helpful data inpatients with precarious circulatory status afteroperation. The measurement of central venouspressure is a sensitive index of hypovolaemia andof heart failure but is not always helpful inproblems of inadequate circulation after operation.

Inadequate peripheral circulation, even withrelatively good central arterial pressure, is a verygrave sign. Poor circulation caused by hypo-volaemia may be corrected by the administrationof blood when the central venous pressure islow. Poor ventilation is occasionally the causeof failing circulation; aspiration of tracheo-bronchial secretions improves circulation dramati-cally in such cases. Inadequate peripheralcirculation among our patients has usually resultedfrom obstruction to the flow of blood throughthe lungs, due either to severe pulmonaryhypertension or to a mechanical block in theoutflow tract of the right ventricle or in thepulmonary arteries.Hypoxia resulting from poor peripheral circula-

tion is followed by increasing metabolic acidosiswhich potentiates the circulatory failure. Assistedventilation with the respirator and vasopressoragents may bring temporary improvement, butevery effort must be made to correct the under-lying abnormality. The catastrophe of suddendeath after open heart surgery has occurred onlyin those patients with inadequate cardiac outputand failing peripheral circulation.

Digitalis is not required by the majority of ourpatients undergoing open heart surgery. Patientswith heart failure and those with severe pulmonaryhypertension customarily receive digitalis beforeoperation and the drug is always continuedafterwards.DISTURBANCES OF HEART RHYTHM.-Complete

heart block is a rare sequel to the repair of cardiacdefects. In our experience it has never been aserious problem but has occasionally happenedwhen cardiac arrest has been induced during theoperation. In such cases the block seemed to berelated to hypoxia of the heart rather than toplacement of sutures close to the conductionbundle. Temporary atrioventricular dissociationhas been seen frequently during bypass withhypothermia and at times has occurred before anymanipulation of the heart has taken place. Thecondition has always cleared before completionof the operation.



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In our procedure a myocardial electrode isalways inserted if complete heart block is presentat the end of the operation and if the ventricularrate is too slow to maintain an adequate peripheralcirculation. A transistor pacemaker maintains anadequate heart rate and circulation for thesepatients. Isuprel (isopropylarterenol) administeredintravenously, with a change to the sublingual orrectal route of administration later, has maintainedan adequate heart rate in some of these patients.In most of the few patients with complete heartblock at the time of discharge cardiac rhythm hasbecome normal within a month. In four casesthe heart block continued beyond this time,resulting in the death of two of these patients.

Partial or complete right bundle branch blockhas been seen more frequently but has notinfluenced the post-operative course of ourpatients. In rare cases a patient with acquiredheart disease has developed atrial flutter, paroxys-mal atrial tachycardia, or atrial fibrillation afteroperation. Such disturbances of rhythm yieldedto vagal stimulation, elevation of blood pressure,and administration of digitalis.CEREBRAL DAMAGE.-Air embolism as the cause

of post-operative cerebral injuries in our patientshas occurred only when the left side of the hearthas been opened, either directly or through aseptal defect. Air has thus been trapped in theleft ventricle and ejected into the circulation. Theperfusion apparatus itself has not been a sourceof air embolism.

Air embolism can be prevented by the routineaspiration of the left ventricle as soon as air canno longer enter the left side of the heart.Evacuation of the trapped air is most easilyaccomplished by elevating the tip of the leftventricle and aspirating the air with a syringe andneedle. The patient is placed in the Trendelenburgposition during perfusion so that air collects inthe apex of the ventricle and cannot enter theaorta.

Neurological manifestations range from hyper-excitability and mild hallucinations immediatelyafter operation to serious cerebral damage withfocal neurological symptoms. The mild symptomsclear in a day or two; the severe symptomspersist for a week or two, but clearing has beengratifyingly complete and no patient has been leftwith recognized permanent damage.The use of hypothermia in the treatment of

patients with severe cerebral depression isadvisable and rectal temperatures are kept at 30°to 340 C. for 72 hours by means of a watermattress.

DISTURBANCES OF THE ACID-BASE BALANCE.-The changes in acid-base balance after open heartsurgery are similar to those seen after any thoracicoperation. During operation there is respiratoryalkalosis and metabolic acidosis, which change inthe post-operative period when the patient is nolonger overventilated to a combined respiratoryand metabolic acidosis. These changes have notbeen of clinical importance in our series ; thebalance usually becomes normal within 24 hours.

If hypoxia is present or if the peripheralcirculation fails, increasing metabolic acidosisoccurs. Administration of sodium bicarbonateintravenously corrects the trend temporarily, butimprovement can continue only when the basiccause of the acidosis is found and corrected.

INFECTION AND UNEXPLAINED FEVER.-Withregard to bacterial infections, we found early inour experience that cold-sterilization of perfusionequipment was not adequate; several infectionsdue to Pseudomnonas aeruginosa occurred amongour patients. All parts of the perfusion equipmentthat come in contact with blood are now sterilizedby autoclaving, and in our last 500 open heartoperations there has been only one case ofinfection, an overwhelming staphylococcal septi-caemia. Prophylactic antimicrobial agents havebeen administered to all patients. The largewounds, extensive dissections, and the use ofprostheses make this procedure advisable, despiteconflicting opinion about the value of suchprophylaxis (Linton, 1961). No serious compli-cations accompanying the use of antimicrobialagents have been observed. No antimicrobialsare applied locally during the operation, butpenicillin and streptomycin are administered to thepatient on the night before the operation, and thisregimen, with erythromycin added, is continuedfor five to seven days after the operation.Many patients are febrile for three or four days

after operation with rectal temperatures rangingfrom 380 to 390 C. The cause of the fever hasnot become clear beyond the fact that it is notthe result of bacterial infection. The febrileresponse is more prolonged in patients withlarge prostheses. In our post-operative care ofthese patients, rectal temperatures are recordedconstantly. Aspirin is used freely and the oxygentent is kept cool. For patients with temperaturesof 390 C. or higher, cooling is assisted by meansof a water mattress.

RESULTSSix hundred patients have undergone correction

of congenital and acquired cardiac defects with

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the aid of extracorporeal circulation (Table I).The majority of the patients have been youngchildren. The smallest patient successfullyperfused weighed 2.5 kg. and the largest 97 kg.Among 311 patients with uncomplicated intra-cardiac defects, there were two operative deathsand one late death related to operation, for a

TABLE IRESULTS OF EXTRACORPOREAL CIRCULATION IN

600 PATIENTSDefect

Ventricular septal defectNo pulmonary hypertensionPulmonary .,

Pulmonary stenosisAtrial septal defectTetralogy ef FallotAortic lesions*Mitral ,Miscellaneous

Patients

19414153

749886564844

Totals 600

418

* Pure uncomplicated mitral stenosis is treated by transventrizulardilatation without extracorporeal circulation.

mortality rate of less than 1 %. It should benoted that these deaths occurred in the first halfof the group; no deaths have occurred in thelast 180 of these patients.VENTRICULAR SEPTAL DEFECTS.-In 194 patients

a ventricular defect was closed. Repair is custom-arily carried out by direct suture, although largedefects are closed with a knitted Teflon prosthesiscut to the size of the defect. The ventriculardefect is exposed through a longitudinal incisionin the outflow tract of the right ventricle, althoughdefects low in the muscular septum are approachedmore easily through an incision at the apex ofthe right ventricle.Among 141 patients without serious pulmonary

hypertension (75% of the systemic pressure) therewere two early deaths and two late deaths. Inone patient the cause of death was aortic regurgi-tation which had not been recognized beforeoperation. In the second patient death resultedfrom perfusion difficulties; venous abnormalitiesinterfered with proper cannulation. Of the twolate deaths, one was due to increasing hydro-cephalus, which apparently was arrested at thetime of operation, and the other was due to anautomobile accident.

Fifty-three of these patients had severepulmonary hypertension with pulmonary arterypressure 75% or more of the systemic pressures.Seventeen of the patients died in the immediatepost-operative period and one died later. Thehighest mortality occurred in patients who were2 years of age or less and in those withinsignificant left-to-right shunts or with some

peripheral desaturation. The problem of caringfor the patient with serious pulmonary hyper-tension has presented a major challenge toproponents of open heart surgery. The use of themedian sternotomy, the avoidance of musclerelaxants, and the use of systemic hypothermiaduring perfusion, as well as fanatical attention tothe avoidance of pulmonary venous congestion,have been responsible for recent improved results.Tracheostomy and assisted ventilation have beenrequired less and less frequently.Ten patients have had a second operation for

a persistent ventricular defect. A number ofpatients, most of them infants, have residualmurmurs of uncertain significance. In a fewchildren with faint murmurs suggesting possibleresidual defects, the murmurs have disappearedin the year after operation.ATRIAL SEPTAL DEFECTS.-Atrial septal defects

of the secundum type were repaired in 84 patients.The two operative deaths in this group occurredin adult patients with severe pulmonary hyper-tension and peripheral arterial desaturation,conditions that are now presumed to contra-indicate open heart surgery. One late deathoccurred when a boy who had been a patientin this group committed suicide because he wasnot accepted in the Armed Services.

Atrial defects are repaired by direct suture,except for large defects in adults with fragile septaltissue, which are closed with a prosthesis of knittedTeflon. Fourteen patients had partial anomalousvenous drainage from the right lung entering theright atrium. In 13 it was possible to correctthe defect and direct the anomalous drainage intothe left atrium. In one patient a small upper lobevein draining into the superior vena cava wasallowed to remain uncorrected. In four patientspulmonic stenosis, a less important associatedlesion, was corrected at the same time as theatrial defect, and in one mitral stenosis wascorrected. In another patient unrecognized mitralinsufficiency was repaired at a second operation.

Preliminary palpation of the atrium frequentlyfailed to disclose the extent and the complexity ofthe lesions present. It was difficult to recognizeby palpation the fenestrated and multiple defects.The use of heart-lung bypass enabled us to closethese lesions under direct vision. It is believedthat this method of closing atrial defects is superiorboth to blind closure and to the brief periods ofexposure afforded by hypothermia.PULMONIC STENOSIs.-Pulmonary valve stenosis

was corrected in 68 patients and isolated infundi-bular stenosis in six patients. One child was



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OPEN HEART SURGERY

readmitted to the hospital eight months afteroperation because of a Ps. aeruginosa endocarditisof the pulmonary valve; death occurred after aprolonged hospital course. The child had beendischarged from the hospital after an uneventfulrecovery from the operation, but since Ps.aeruginosa was the organism found in the rareinfections occurring early in our experience, theoperation must be implicated in this child's death.A second patient died of pseudomembranousenterocolitis in a sanatorium where she wasconvalescing from resection of the left upper lobefor tuberculosis.

In the operative procedure carried out in thisgroup, the pulmonary valve is exposed by anincision in the pulmonary artery above the valve.An attempt is made to construct a three-cuspvalve by incising the stenotic valve along itscommissures. Great care is taken to keep theline of incision in the commissure. Incision iscarried to the annulus of the valve. Dilatationof the annulus is avoided, since this producespulmonary valve insufficiency. No effort is madeto resect the hypertrophied muscle of the outflowtract because it is believed this functionalobstruction of the right ventricle graduallydisappears after the pulmonary valve stenosis hasbeen corrected (Brock, 1961). In none of thepatients was there an unsuspected ventriculardefect. An atrial defect was present in 18 patientsand was corrected together with the pulmonicstenosis.

TETRALOGY OF FALLoT.-Correction of tetralogyof Fallot was accomplished in 86 patients. Thediagnosis of tetralogy was made when bothpulmonary stenosis and a ventricular defect werepresent. In most cases the ventricular septaldefect is closed with a prosthesis of knitted Teflonsutured in place with running sutures of 3-0 silk.The infundibular stenosis usually present isresected as widely as possible. In the majorityof patients the outflow tract is increased in sizewith a rectangular gusset of woven, crimped Teflonfashioned from an aortic graft (Barnard andSchrire, 1961). This is extended across thepulmonary valve as far as the left pulmonaryartery whenever necessary to construct anadequate outflow tract. Twenty-two patients hadprevious shunts which were interrupted at the timeof operation. The subclavian-pulmonary arteryanastomoses were all interrupted without seriousdifficulty. The aorto-pulmonary artery anasto-moses were more difficult to interrupt. In themajority it was possible to isolate the anastomosisand to occlude it. A procedure including deep

K

hypothermia and circulatory arrest, with closureof the anastomosis from within the pulmonaryartery, has been employed, but technical difficultiesin carrying out the manceuvre were responsiblefor two deaths.There were nine early deaths and three late

deaths among the 64 patients without a previousshunt who underwent correction of tetralogy ofFallot. The early deaths were most frequentlythe result of inability to establish an adequateoutflow tract. One of the late deaths was dueto heart block and another to a large residual left-to-right shunt. The third death occurred suddenlyand was unexplained. Among the 22 patients witha previous shunt there were four post-operativedeaths.AoRTIc VALVE LEsIoNs.-Correction of con-

genital aortic stenosis was accomplished in 22patients; three deaths occurred in this group, oneat the time of a second operation for congenitalmitral insufficiency. Congenital aortic insuffi-ciency has been corrected in three patients withouta death. Surgical correction of acquired aorticvalve lesions has been much more difficultand clinical improvement after operation lesssatisfactory. Among nine patients operated uponfor pure aortic stenosis there were two deaths.Acquired aortic insufficiency was repaired in 17patients with six deaths. There was one deathamong five patients operated on for mixed aorticstenosis and insufficiency.The heart is supported by perfusion of the left

coronary artery or both coronary arteries atlevels of moderate hypothermia. More recentlycoronary perfusion is being combined with localhypothermia by means of saline slush applied tothe heart. Success in attempts to correct aorticvalve lesions depends upon the protection to theheart provided during operation and upon themyocardial reserve. A second complicatingproblem has been the frequent presence of mitralor tricuspid valve disease which has also requiredcorrection.MITRAL VALVE LESIONS.-Correction of mitral

valve abnormalities has been carried out througha right lateral approach in 48 patients with eightdeaths. There were no deaths among the eightpatients operated on for congenital mitral insuffi-ciency. Thirteen patients underwent correctionof mitral stenosis with one death. There werethree deaths among the patients undergoingcorrection of acquired mitral insufficiency.Fourteen patients had correction of mixedstenosis and insufficiency; there were four deathsin this group. The association of aortic valve

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disease and, particularly, tricuspid valve diseasehas complicated correction in these patients.MISCELLANEOUS LESIONS. -The remaining

lesions were more complicated and the mortalityrate was higher. There were 44 such patients and15 did not survive operation. The lesions includedtransposition of the great vessels, endocardialcushion defects, and total anomalous pulmonaryvenous drainage.

SUMMARYAt the University of Michigan Medical Center

600 patients have undergone correction ofcongenital or acquired intracardiac defects witha safe, easily controlled extracorporeal circulationemploying a rotating disc oxygenator andmoderate systemic hypothermia. Seventy-eightearly and late deaths occurred in this group ofpatients.Among 311 patients with uncomplicated con-

genital abnormalities there have been threeoperative deaths, a mortality rate of less than1 %. One hundred and eighty of these patientshave been operated upon consecutively withouta death.

Early correction of most congenital intracardiacabnormalities can be accomplished safely. Webelieve that the threat to the patient's life fromsuch lesions outweighs the risk of operation.

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Springfield, Ill.Barnard, C. N., and Schrire, V. (1961). Thorax, 16, 346.Bradley, A. F., Stupfel, M., and Severinghaus, J. W. (1956). J. appl.

Physiol., 9, 201.Brock, R. (1961). Brit. Heart J., 23, 337.Carr, E. A., Jr., Sloan, H., and Tovar, E. (1960). J. nucl. Med., 1, 165.Clowes, G. H. A., Jr. (1960). Physiol. Rev., 40, 826.DeWall, R. A.. Grage, T. B., McFee, A. S., and Chiechi, M. A. (1962).

Surgery, 51, 251.and Lillehei, C. W. (1962). J. Amer. med. Ass., 179, 430.

Drew, C. E. (1961). Brit. med. Bull., 17, 37.Engle, M. A., Holswade, G. R., Goldberg, H. P., and Glenn, F.

(1958). Pediatrics, 21, 70.Foote, A. V., Trede, M., and Maloney, J. V., Jr. (1961). J. thorac.

cardiovasc. Surg., 42, 93.Gerbode, F., Osborn, J. J., and Johnston, J. B. (1960). Thorax, 15,

185.Gollan, F. (1959). Physiology of Cardiac Surgery. Thomas, Spring-

field, Ill.Harley, H. R. S., ed. (1960). Modern Trends in Cardiac Surgery.

Butterworths, London.Kay, E. B., Nogueira, C., Suzuki, A., Postigo, J., and Mendelsohn, D.

(1961). Ann. Surg., 154, Suppl., p. 159.Lancet (1961). "Ventricular septal defect" (leading article), 2,

1074.Linton, R. R. (1961). Surg. Gynec. Obstet., 112, 218.Lucas, R. V., Jr., Adams, P., Jr., Anderson, R. C., Meyne, N. G.,

Lillehei, C. W., and Varco, R. L. (1961). Circulation, 24, 1372.Molloy, P. J. (1961). Thorax, 16, 335.Morris, J. D., Sloan, H., Wilson, W. S., and Brandt, R. L. (1962).

J. thorac. cardiovasc. Surg., 43, 17.Oliver, W. J., Graham. B. D., and Wilson, J. L. (1958). J. Amer.

med. Ass., 167, 1211.Sloan, H.. Morris, J. D., vander Woude, R., Hewitt, H., and Long, G.

(1959). Surgery, 45, 138.Sturtz, G. S., Kirklin, J. W., Burke, E. C., and Power, M. H. (1957).

Circulation, 16, 988.Taylor, L. M., Theye, R. A., Devloo, R. A., and Kirklin, J. W. (1962).

Surg. Gvnec. Obstet., 114, 97.Trede, M., Foote, A. V., and Maloney, J. V., Jr. (1961). Ann. Surg.,

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OPEN HEART SURGERY: RESULTS IN 600 - Thorax · OPEN HEART SURGERY: RESULTS IN 600 CASES* BY HERBERT SLOAN, JOE D. MORRIS, JAMES MACKENZIE, AND AARON STERN From the Department of Surgery