Journal, Relations pressure in pulmonary artery, atrium, special to ... · in the left atrium wasmeasuredfromthe zpoint whichis thefoot ofthecwave. Inabsenceofthe cwaveit wasjudgedontheleftatriumcurve,from

British Heart Journal, I97I, 33, 494-499.

Relations between pressure in pulmonaryartery, left atrium, and left ventricle withspecial reference to events at end diastole

S. A. Forsberg'From the Medical Department I, Sahlgren's Hospital, University of Gdteborg, Sweden

Results were extracted from I58 patients who have undergone diagnostic heart catheterizationat rest. Seventeen were considered normal. Simultaneous pressure records from the pulmonaryartery and left atrium were always made and often also from the left atrium and ventricle. Someof the main conclusions are as follows.I) There is normally at rest left atrioventricular diastolic pressure congruence.2) The z point, that is thefoot of the left atrial c wave, is normally identical with the end-diastolicventricular pressure.3) Normally the pulmonary arterial diastolic pressure is approximately identical with the end-diastolic pressure of the left ventricle.4) At the end of diastole, theflow and pressure gradient across the pulmonary vascular bed seem

to be in phase and both are close to zero.

_5) Patients with different cardiovascular diseases, the majority with mitral valvular disease,were compared with the normal group. With moderate mitral stenosis without much raised pul-monary vascular resistance, the relation between pulmonary arterial diastolic pressure and end-diastolic pressure in the left atrium is similar to that in normal patients.

Pulmonary arterial diastolic pressure hasreceived relatively less attention than othermeasured entities in the pulmonary circulationsuch as the arterial systolic or mean pressureor pulmonary capillary venous pressure. Themain purpose of the present study was toinvestigate factors determining the pulmonarydiastolic pressure and its relation to events inthe left ventricle and left atrium.

Methods and materialResults were extracted from the material of 158patients who have undergone diagnostic right andleft heart catheterization with measurement of thepulmonary blood volume. Details of the methodswere described by Forsberg (1964).

Catheters were placed in the pulmonary arteryand left atrium, and pressures were simultane-ously recorded. In about one-third of the materialthe two pressures were recorded with the samezero and calibration pressure on congruent levelson the recording paper, giving a direct visualpicture of the instantaneous pressure differenceduring the heart cycles. A similar technique wasroutinely used when left atrial and ventricularpressures were simultaneously recorded.

Received 23 September I970.1 Present address: Medicinska kliniken, Boras lasarett,50i I5 Boris, Sweden.

The undamped natural frequency of the wholemeasuring system is of the order of I5-40 Herz,the pulmonary arterial catheter usually givingvalues in the lower half of the range and the leftatrial or left ventricular catheter rather more inthe upper half. The degree of damping is aroundOi. An empirical comparison of the two recordingsystems is seen in Fig. x. In all figures the timebetween two thick lines equals OI sec.

Calculations of average pressures were madeout of I0 heart cycles. The end-diastolic pressurein the left atrium was measured from the z pointwhich is the foot of the c wave. In absence of thec wave it was judged on the left atrium curve, fromthe left ventricular curve, or from the R wavein the electrocardiogram. All results refer toinvestigations of patients at rest in the supineposition.The diagnoses in the total material were as

follows: normal haemodynamics without heart orlung vascular disease (I5); obstructive lung diseasewith normal haemodynamics (2); left atrialmyxoma (2); mitral valvular disease (8i); mitraland aortic valvular disease (I3); aortic valvulardisease (23); aortic coarctation (6); systemichypertensive disease (i); cardiomyopathy (5);pulmonary stenosis (2); primary pulmonaryhypertension (7); hyperkinetic heart syndrome (i).Absence of heart disease mostly implies patientswith a systolic murmur where no pathology couldbe found.

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Relations between pressure in pulmonary artery, left atrium, and left ventricle 495

a b

FIG. I (a) Two catheters in the left ventricle: diagnosis, a physiological murmur. (b) Twocatheters in the right atrium: diagnosis, mitral stenosis.

ResultsRelations between left atrial and left ven-tricular pressure during diastole andaround end-diastolic point The atrio-ventricular gradient could be visually in-spected in 8 patients without mitral obstruc-tion: 7 had sinus rhythm (2 with normal heartsand 5 with some heart disease) and one hadatrial fibrillation. With due regard to minorartefacts there was diastolic congruence in allpatients (Fig. 2).As the shape of the left atrial pressure

curves generally agrees with that previouslyreported, only some points of interest shouldbe stressed. The upstroke of the c wave isconsistently congruent with the upstroke ofventricular systole in patients with sinusrhythm and normal haemodynamics or some

ventricular or aortic disease (Fig. 2). This factserves as a test of validity of our recordingsand verifies the atrial z point as an indicatorof the end-diastolic ventricular pressure.The c wave is, however, not consistent. In

I7 haemodynamically normal patients withoutheart disease, 6 lacked a c wave and 2 had a

c wave in one recording but not in another(Fig. 2b).

In patients with mitral valvular disease andatrial fibrillation a c wave is always present,beginning at the point of equilibration of leftatrial and ventricular pressure during theisovolumetric ventricular contraction phase(Fig. 3).

Relations between pulmonary arterialdiastolic and left atrial pressure The I7patients with normal haemodynamics withoutsigns of heart disease were studied separately.The mean left atrial pressure varied from 3 to

I2 mmHg with a mean of 6-4 mm. Thedifference between pulmonary arterial diasto-lic and mean left atrial pressure is 14 ± 2-0mmHg. Pulmonary arterial diastolic pressureminus left atrial end-diastolic pressure is-04 ± PI5 mmHg. The pulmonary arterialpressure decreases during diastole and reachesits minimum at a level equal to the peak of theleft atrial a wave or slightly below this peak,constituting a pressure gradient from theatrium to the pulmonary artery for a moment(Fig. 4).A selection was made of patients having

heart disease, atrial fibrillation, and a meanleft atrial pressure at rest of I2 mm or lessand a pulmonary vascular resistance less than2 units. It happened that all i5 such patientshad mitral valvular disease. Pulmonaryarterial diastolic pressure minus left atrialmean pressure is i o ± 2-o mmHg. Pulmonaryarterial diastolic pressure minus left atrialend-diastolic pressure is 2-5 ± i.5 mmHg.These results are close to those in the normalpatients (Fig. 5).During long systolic intervals, the pulmon-

ary arterial pressure can become congruentwith the left atrial pressure (Fig. 5b), butthe left atrial pressure was never high-est at the end of diastole with atrial fibrilla-tion.The Table shows the difference between

pulmonary arterial diastolic pressure and leftatrial mean pressure related to the pulmonaryvascular resistance in all patients with sinusrhythm or atrial fibrillation. These two groupsbehaved similarly and were thereforecombined.For each increment of pulmonary vascular

resistance the average pressure differenceincreased but not more than 4 mmHg with

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496 S. A. Forsberg

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FIG. 2 Simultaneous records from the left atrium and left ventricle in 2 normal patients(a and b) and patients with cardiovascular disease but normal mitral orifice (c, d, and e).

TABLE r55 patients with sinus rhythm oratrial fibrillation (i7 without and I38 withsome cardiovascular disease)

Puilm. vasc. No. of Pulm. art. diast. -resist. (units)* patients left atrial mean

(mmHg)

00-09 27 ±0 (-4; +4)10I-19 83 +2 (-3; +9)2-0-29 22 +4(-I; +I6)30-39 8 +4(-I; +8)40-49 4 +5 (+I; +8)5 0-59 I +7 ((-)6-o-69 2 + 27 (+ 26; + 27)70-7°9 2 +9(0; +I8)>8-o 6 +36 (+I9; +63)

* Pulmonary vascular resistance expressed in units(pressure difference mmHg, cardiac output in l./min).Within brackets are the extreme values in each group,and outside are the mean values.

resistance as high as 4 units. Individual varia-tions exist among those with heart disease,some with a low resistance and large pressuregradient, others with a high resistance and asmall gradient.

In the 24 patients with pulmonary vascularresistance between I-o and I19 units, thoseI2 with the largest pressure gradient (pul-monary diastolic minus left atrial mean pres-sure) were compared with those I2 with thelowest gradient. On an average the largestdifference was associated with a higher heartrate and lower mean left atrial pressure,whereas the stroke volume and pulmonarydiastolic pressure were similar in the twogroups.



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a DFIG. 3 Simultaneous records from the left atrium and left ventricle in patients with mitralstenosis and atrial fibrillation.

DiscussionA review of normal pressure curves from thepulmonary artery, left atrium, and left ven-tricle, and their interrelations and connexionsto haemodynamic events was presented byBrecher and Galletti (I963). Left atrioven-tricular pressure events in mitral valvulardisease have been repeatedly reported (Braun-wald et al., I955; Gordon, Kirschner andMoscovits, I96I; Wooley et al., I968). Ourrecordings in patients with normal as well asabnormal haemodynamics agree with thosepreviously described. Pertinent to this studyis the conclusion that in the resting conditionthere is normally congruence during the

whole of diastole between the left atrial andventricular pressure. In mitral valvular diseasewith moderate or slight stenosis it also comesto a congruence if the gradient disappearsbefore the end of diastole.Our results show that the end-diastolic left

ventricular pressure normally is the factorwhich sets the pulmonary arterial diastolicpressure at rest. In about 95 per cent thepressure difference should be less than 3mmHg. Recently, Bouchard, Gault, and Ross(I969) presented similar data at a meeting.In our patients with mitral valvular diseaseand normal to slightly increased pulmonaryvascular resistance the figures were close to

FIG. 4 Records from patients with normal hearts. Only the tracings from the pulmonaryartery and left atrium should be considered.

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FIG . 5 Records from patients with mitral stenosis and atrial fibrillation. Only the tracingsfrom the pulmonary artery and left atrium should be considered.

those in normal patients. From our data onthe normal patients, it can be calculated thatthe difference between mean and end-diastolicleft atrial pressure is i -8 mm. Braunwald etal. (I96I) found o-3 mm and Samet et al.

(I965) I *0 mm.These facts have important implications for

patients where the pulmonary arterial pressureis continually monitored in order to discloseleft ventricular insufficiency and the wedgedpressure cannot be easily recorded. This isnow becoming more common in coronarycare units. It is necessary to do future studiessimilar to the present one and to includepatients with a relatively normal vascularbed afflicted by acute ventricular failure.Our unpublished observations have failed

to show any significant phase shift of thepressure curve, withdrawing the catheter fromthe peripheral lung vessels to the pulmonaryarterial stem or to the left atrium by the trans-septal route. Identity of pressure in the pul-monary artery and left atrium means absenceof flow-driving force across the pulmonaryvascular bed at the end of diastole and themomentary reversed pressure difference foundin some normal patients at the peak of thea wave means a force driving blood backwards.Presumably no waterfall effect is present inthe lungs of normal patients at rest in thesupine position (Permutt and Riley, I963).The pulmonary venous pressure is then sup-posedly higher than the alveolar pressure.What normal flow pattern there is in the

pulmonary capillaries does not seem to besettled yet. From Fishman's review (I963), itis evident that some plethysmographic studiesand investigations including direct inspectionof the pulmonary microcirculation in vivosupport an intermittent type of flow whereas

other plethysmographic studies support acontinuous but pulsatile flow.

Cineradiographic observations of radio-paque droplets in the pulmonary veins and leftatrium of dogs have demonstrated flow witha small momentary backward componentoccurring close to the end-diastolic point(Ferrario, Nordenstrom, and Paulin, I968).Direct flow measurements from the pulmon-ary vein and left atrium are in accordancewith these results (Morkin et al., i965).The sum of evidence is consistent with the

idea that the flow through the pulmonaryveins and the pressure gradient across thewhole pulmonary vascular bed are in approxi-mate phase at the end of diastole. Both areminimal and at least sometimes momentarilyreversed.Our patients with pulmonary vascular re-

sistance between i and 2 units had normal aswell as abnormal pulmonary vascular beds.The end-diastolic pulmonary arterial to leftatrial mean pressure difference was positivelycorrelated to heart rate and negatively to meanleft atrial pressure. High heart rate implies a

short time for equilibration of pressures, anda low left atrial pressure means that thepulmonary arterial pressure has to fall deeperfor equilibration with the left atrium.

ReferencesBouchard, R. J., Gault, J. H., and Ross, J., Jr. (I969).

Comparison of pulmonary arterial end-diastolicpressures in patients with and without left ven-

tricular disease. Circulation, 40, Suppi. 3, p. 49.

Braunwald, E., Brockenbrough, E. C., Frahm, C. J.,and Ross, J. (I96I). Left atrial and left ventricularpressures in subjects without cardiovascular disease.Circulation, 24, 267.

498 S. A. Forsberg



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Braunwald, E., Moscovitz, H. L., Amram, S. S.,Lasser, R. P., Sapin, S. O., Himmelstein, A.,Ravitch, M. M., and Gordon, A. J. (I955). Thehemodynamics ofthe left side of the heart as studiedby simultaneous left atrial, left ventricular, andaortic pressures; particular reference to mitralstenosis. Circulation, I2, 69.

Brecher, G. A., and Galletti, P. M. (I963). Functionalanatomy of cardiac pumping. In Handbook ofPhysiology, Section 2: Circulation, Vol. 2, pp. 759-798. American Physiology Society, Washington,D.C.

Ferrario, C. M., Nordenstrom, B., and Paulin, S.(I968). Flow velocity variations in the pulmonaryveins of the dog. Investigative Radiology, 3, 73.

Fishman, A. P. (I963). Dynamics of the pulmonarycirculation. In Handbook of Physiology, Section 2:Circulation, Vol. 2, pp. I667-I743. AmericanPhysiology Society, Washington, D.C.

Forsberg, S. A. (I964). Pulmonary blood volume inman. Acta Medica Scandinavica, 175, Suppl. 4I0.

Gordon, A. J., Kirschner, P. A., and Moscovits, H. L.(I96I). Hemodynamics of Aortic and Mitral ValveDisease. Grune and Stratton, New York.

Morkin, E., Collins, J. A., Goldman, H. S., and Fish-man, A. P. (I965). Pattern of blood flow in thepulmonary veins of the dog. Journal of AppliedPhysiology, 20, iii8.

Permutt, S., and Riley, R. L. (1963). Hemodynamicsof collapsible vessels with tone: the vascular water-fall. Journal of Applied Physiology, I8, 924.

Samet, P., Bernstein, W. H., Medow, A., and Levine,S. (I965). Transseptal left heart dynamics in thirty-two normal subjects. Diseases of the Chest, 47, 632.

Wooley, C. F., Klassen, K. P., Leighton, R. F., Good-win, R. S., and Ryan, J. M. (I968). Left atrial andleft ventricular sound and pressure in mitral steno-sis. Circulation, 38,'295.



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Journal, Relations pressure in pulmonary artery, atrium, special to ... · in the left atrium wasmeasuredfromthe zpoint whichis thefoot ofthecwave. Inabsenceofthe cwaveit wasjudgedontheleftatriumcurve,from