Experience with “cardioversion” of atrial fibrillation and flutter

Report on Therapy

Experience with “Cardioversion” of

Atria1 Fibrillation and Flutter*

JAMES J. MORRIS, JR., M.D., t YIHONG KONG, M.D., WILLIAM C. NORTH, M.D. and HENRY D. MCINTOSH, M.D.

Durham, North Carolina

T HE introduction of direct current countershock by Lown et al.‘-cardioversion-re-

quires that a new chapter be written in the treatment of cardiac arrhythmias. This technic con- sists of delivering an electrical impulse of high energy level through the*intact chest wall, pro- ducing a synchronized depolarization of all myocardial cells, and the subsequent sponta- neous resumption of a more orderly impulse propagation.

This report describes our experience with the technic in 70 patients with atria1 fibrillation or flutter. The clinical status and etiologic classification of these patients are discussed, as well as the success of attaining and maintaining normal sinus rhythm during the follow-up period of 1 to 9 months.

METHODS

External D.C. cardioversion was attempted in 70 patients with atria1 fibrillation or flutter. The onset of the arrhythmia was determined by a reliable history from the patient or the earliest documentation from the referring physician or hospital records. In the patients with paroxysmal arrhythmias only the duration of the rhythm disturbance that was treated by cardioversion is reported.

All patients were hospitalized. Digitalis was used for adequate control of the ventricular rate, and other therapeutic measures were employed to obtain the best clinical status and optimal cardiac compensa- tion. Anticoagulation was not specifically instituted for this procedure. However, 4 patients who had

been taking anticoagulants were continued on such therapy.

The nature of the procedure was carefully explained to the patient. Nothing by mouth was allowed for 12 hours before anesthesia. No premeditation was employed. The anterior chest wall was shaved when indicated to insure adequate contact of the electrodes. Intravenous thiobarbiturates were employed as the anesthetic agent. The electrocardiogram was continuously monitored during the procedure. Follow- ing the procedure, the patient was observed until stable (15 to 30 min.) and then returned to the ward for two to three hours of bed rest. Thereafter, the patients were allowed activity as dictated by their basic condition and were kept under observation for two to eight days in the hospital.

A Lown D.C. cardioverter (American Optical Co.) was programed to discharge a synchronized D.C. countershock during the downstroke of the R wave. In the initial 26 patients external electrodes three and a half inches in diameter were used. The electrodes were positioned at the apex and base of the heart (Fig. 1, A and B). In the remaining patients the larger electrodes,1 five inches in diameter, were employed and positioned on the anterior and posterior chest wall. The initial countershock was usually begun at 50 w.-sec. and advanced 50 or 100 w.-sec. with each attempt until the patient reverted to regular sinus rhythm or the. reversion was not accomplished with an energy level of 400 w.-sec.

Intravenous thiobarbiturates, either sodium methohexital (BrevitaP) or sodium thiamylal (Surital@), were employed in all patients for induction of light

$ Designed by Dr. Bernard Lown and supplied by American Optical Company, Buffalo, N. Y.

* From the Cardiovascular Laboratory, Department of Medicine and the Department of Anesthesiology, Duke University Medical Center, Durham, N. C. This study was supported in part by Research Grant HE-07563-02 of the National Heart Institute of the National Institutes of Health, U. S. Public Health Service and by a grant-in-aid from the North Carolina Heart Association and the Wynn Pharmacal Corporation, Philadelphia, Pa.

t Work completed during tenure of U. S. Public Health Service Postdoctoral Research Fellowships.

94 THE AMERICAN JOURNAL OF CARDIOLOGY

“Cardioversion” of Atria1 Fibrillation and Flutter

FIN. 1. The types of external electrodes used in cardioversion are shown, as well as their manner of application. In a and b, the conventional 3.5 in. electrodes are shown. In c and d, the larger anterior-posterior electrodes with their proper positioning are demonstrated. In actual use, with both types of paddles, the patient is in the supine position; the patient is erect in this illustration only to show the application.

anesthesia. Maintenance of the desired level of anesthesia was accomplished with nitrous oxide and occasionally with supplemental doses of thiobarbiturates. A nasopharyngeal airway was used in all cases. Succinylcholine was also used in the initial 22 patients. To evaluate the influence of succinylcholine, the anesthetic records of the first 38 patients were reviewed in detail. There were no differences in the anesthetic time or complicatio IS nor adequacy of the anesthesia with either sodium methohexital or sodium thiamylal. When succinylcholine was employed in addition to thiobarbiturates, there was no significant change in the adequacy of the anesthesia nor a significant decrease in the degree of muscular activity associated with the electrical discharge. The only discernible difference was a significant prolonga- tion of the time of anesthesia from an average of 22 to 39 minutes. With further experience, in the remaining 32 patients, the anesthetic time with a thiobar- biturate alone was reduced to less than 15 minutes.

In the initial 50 patients maintenance quinidine gluconate (Quinaglute@) was not instituted until the patient had reverted to regular sinus rhythm, except for the test dose administered for one to two days before the procedure to determine if the drug could be employed for maintenance therapy. In the last 20 patients quinidine gluconate, 0.33 gm. every eight hours, was begun three days prior to cardioversion. In one instance in which the patient was allergic to quinidine, procaine amide, 0.5 gm. every eight hours, was employed. Serum quinidine levels were determined fluorometrically.*

After discharge, all patients were seen by one of the authors at periodic outpatient visits, the last being at least within one month of preparing this paper.

MATERIAL

Reversion of atria1 fibrillation or flutter to regular sinus rhythm with direct current countershock was attempted 94 times in 70 patients. Atria1 flutter was present in 7 and the remaining 63 had atria1 fibrillation. Twenty-seven of these patients had had cardiac surgery. Except in one case, cardioversion was not attempted until at least six weeks postoperatively. The age of the patients ranged from 19 to 79; 36 per cent were over 50 years old. The arrhythmia was due to a number of causes. Forty-six patients (66%) had rheumatic heart disease, 14 had ischemic heart disease and 3, hypertensive cardiovascular disease; 7 formed a miscellaneous group. Half of the patients had atria1 fibrillation one year or longer. Sixty-four per cent of the patients were included in the New York Heart Association functional classes I and II, 36 per cent in class III and 10 per cent in class IV. The first 25 patients had failed to revert to regular sinus rhythm during an adequate trial of quinidine therapy which required that the drug be administered in this hospital until the appearance of electrocardiographic signs of toxicity, severe hypotension, nausea, vomit- ing or diarrhea. Only 16 of the last 45 patients had undergone previous attempts at reversion with quinidine.

RESULTS

Fifty-nine of 63 patients with atria1 fibrilla-

tion and all patients with atria1 flutter were suc-

cessfully reverted to regular sinus rhythm by

direct current countershock (94%). The num-

ber of discharges used during cardioversion

varied from one to five with an average of three.

The energy level needed for reversion ranged

from 50 to 400 w.-sec. With the large anterior-

posterior electrodes, less energy was needed for

the reversion than with the small electrodes

placed at the apex and the base of the heart

(Table I). For example, at an energy level of

TABLE I

Energy Level for Successful Reversion of Arrhythmias

Watt- With Small Base- Sec. Apex Electrode

With Large Anterior-Posterior

Electrode

No. of Cumulative No. of Cumulative Cardio- Frequency Cardio- Frequency versions ($&J versions (%I

50 or less 1 3 13 26 75 3 13 5 37 100 4 26 19 75 150 I1 61 0 75 200 6 80 5 86 250 3 90 1 88 300 2 97 0 88 350 0 97 2 92 400 1 100 4 100

Total 31 49

JULY 1964

Morris, Kong, North and McIntosh

‘f-ABLE 11

Follow-up of 70 Patients After Cardioversion

outcome No. of

Patients ‘;/is .~-

Remained in RSR* 52 74 Remained in RSR after

initial reversion 45 64 Required repeated reversion

to maintain RSR 7 10 Reverted to AFt following

successful cardioversion 14 20 Failed to revert to RSR 4 6

Totals 70 100

* RSR = regular sinus rhythm. t AF = atria1 fibrillation.

TABLE III

Follow-up of Patients Remaining in Regular Sinus Rhythm

Maintenance of RSR in

Follow-Up No. of Cumulative Period (mo.) Patients % Frequency ( % )

>8 2 4 4 7-8 3 6 10 5-6 9 17 37 3-4 11 21 48 >2 19 37 85 >1 8 15 100

Total 52

100 w.-sec. or less, 75 per cent of the patients could be reverted with the anterior-posterior electrodes, whereas only 26 per cent could be reverted with the small electrodes. This difference was further demonstrated in 5 patients

in whom both types of electrodes were used successfully on two different occasions; the large anterior-posterior electrodes required only one-half to one-quarter the energy needed with the small electrodes.

The result of follow-up of these 70 patients is shown in Table II. Fifty-two patients (74%) were in regular sinus rhythm at the last follow- up visit. Forty-five of this group have been continuously in regular sinus rhythm since the initial cardioversion. The follow-up period (Table III) varies from one to nine months, de- pending upon the time of the cardioversion, but about half of this group have maintained regular sinus rhythm longer than three months. Two patients not placed on maintenance quinidine gluconate therapy were still in regular sinus rhythm at the last follow-up visit, five and nine months, respectively, after reversion. Seven other patients of this group had reverted to atria1 fibrillation once and 1 patient, twice; but as they had maintained sinus rhythm for at least one month, a second or third cardioversion was performed. At the last follow-up visits, they continued in sinus rhythm. The reversions of these 7 patients from regular sinus rhythm to atria1 fibrillation were all coincident with a reduced dose of quinidine gluconate or a low serum quinidine level.

Of the original 70 patients reverted to sinus rhythm on one occasion, 14 (200/,) were in atria1 fibrillation at the time of the last fohow-up; 11 reverted to atria1 fibrillation within four weeks. Nine of these 14 patients underwent multiple attempts at maintenance of sinus rhythm with from two to six successful cardioversions; however, sinus rhythm could not be maintained despite maximally tolerated doses of quinidine, and in some cases, multiple drug

TABLE 1"

Etiology of Atria1 Fibrillation or Flutter and Its Influence on the Maintenance of Regular Sinus Rhythm

No. of Patients No. of Patients % of

% Remaining in RSR Success

Rheumatic heart disease 46 66 34 74 Mitral stenosis 19 27 16 84 Mitral insufficiency 8 12 5 63 Mitral stenosis and insufficiency 5 7 4 80 Combined valvular lesions 14 20 9 64

Ischemic heart disease 14 20 11 79 Hypertensive vascular disease 3 4 2 67 Congenital heart disease 1 1 1 100 Miscellaneous 6 9 4 67

Total 70 52

THE AMERICAN JOURNAL OF CARDIOLOGY


combinations. Five patients had single successful cardioversions followed by recurrence of atria1 fibrillation. Cardioversion was not attempted a second time for a number of reasons in this group. Two patients reverted to atria1 fibrillation while taking the maximally tolerated dose of quinidine, and further attempts were not felt justified. In 1 patient urticaria developed after he was placed on quinidine maintenance, and when the drug was discontinued, he reverted to atria1 fibrillation. Another patient reverted to atria1 fibrillation at a low level of maintenance quinidine (serum quinidine 2.0 to 2.8 mg./L.); however, he was lost to follow- up, and another attempt with higher maintenance levels has not been tried. The remaining patient reverted despite adequate quinidine therapy (3.8 mg./L.). Another attempt is anticipated in the near future after maintaining a higher quinidine level.

Failures: There were 4 patients (6%) who failed to revert to regular sinus rhythm, even when the maximal energy level of 400 w.-sec. was applied. These patients all had rheumatic heart disease with atria1 fibrillation for more than one year and were in functional classes III and IV. All but 1 had had a previous mitral valvulotomy.

The age of the patients and the cause of the atria1 fibrillation seemed to have no significant influence on the immediate success of reversion or the maintenance of the regular sinus rhythm after reversion. However, patients with pure mitral stenosis or mitral stenosis with mitral insufficiency seemed to have a better rate of success in maintaining regular sinus rhythm after reversion than those with pure mitral insufficiency or multiple valvular lesions (Table IV). The patients in functional classes I and II

could be more easily maintained in regular sinus rhythm than those in classes III and IV (Table v). The influence of the duration of atria1 fibrillation upon successful maintenance is shown in Table VI.

Comjdications: In most patients mild erythema developed at the sites of electrode application. This was transient, 24 to 96 hours, and asymptomatic. Mild residual upper chest discomfort and muscle soreness occurred in about 50 per cent of the patients. The discomfort lasted 1 to 6 hours and was rapidly relieved by mild analgesics. Both the erythema and the chest soreness were related to the number and energy level of the discharge and were less ap- parent when the large anterior-posterior elec-

JULY 1964

TABLE v

Functional Classification and Its Influence on Maintenance of Regular Sinus Rhythm

Functional Patients Remained % of Classification No. % in RSR Success

I 14 20 12 86 ,I 24 34 19 79

III 25 36 16 64 IV 7 10 5 71

Total 70 100 52

TABLE VI

Duration of Arrhythmia and Its Influence on Maintenance of Regular Sinus Rhythm

Duration of Patients Remained % of Arrhythmia No. % in RSR Success

O-6 mo. 24 34 21 88 7-12 mo. 11 16 10 90 l-2 yr. 18 26 13 72 3-5 yr. 9 13 5 56 >5 yr. 8 11 3 38

Total 70 100 52

trodes were used. Transient electrocardiographic changes-occasional premature ventricular contractions and premature atria1 and nodal beats-were noted in about 50 per cent of the patients during the first few minutes of the immediate postconversion period ; on occasion, the atria1 premature beats persisted for as long as 24 hours. Three patients developed mild laryngospasm during the anesthesia.

There were five complications noted during these 94 cardioversions and in the follow-up period (50/,). One patient experienced a mild

TABLE WI

Comparison of Quinidine and Cardioversion in Reverting Supraventricular Arrhythmias

Criterion Quinidine Cardioversion

Effective 45-80% 90-95 % Safe (mortality) l-4% 0% Speed l-7 days Minutes Patient discomfort Moderate Minimal Myocardial depression Yes No Peripheral effect Yes No Physician’s time required Days Hours Duration of hospitalization 4-10 days 2-3 days*

* Can be safely done for outpatient.

98 Morris, !Lic/lq, North and McIntosh

febrile illness with cough, leukocytosis, fe\.er and a slight pneumonitis probably related to anesthesia. Ventricular fibrillation was in- duced in 1 patient coincident with an unex- pected capacitor discharge, which fell during the upstroke of the T wave. This event was trig- gered by an artificial upward displacement of the electrocardiographic baseline due to a sud- den movement of the patient. The arrhythmia persisted for approximately 15 seconds and was promptly terminated by a second electrical discharge with restoration of regular sinus rhythm; no residual effects were noted. Sys- temic embolization occurred in 3 patients, an incidence of 3.3 per cent (3 of 90 successful cardioversions). One patient sustained an immediate cerebral embolism at the time of cardioversion. In the other 2 patients cerebral embolization occurred on the third and the tenth days after cardioversion. All were transient and left no residual neurological deficit. Two of these 3 patients had a previous history of embolization, which had occurred at least one year prior to cardioversion. None of these patients were on anticoagulants. Eighteen other patients with a past history of systemic embolization experienced no difficulty following cardioversion.

DISCUSSION

From our data and those reported by other

groups, 3,4 it appears that over 90 per cent of all patients with atria1 fibrillation or flutter can safely and effectively be reverted to regular sinus rhythm by this method. Table VII com- pares the advantages of cardioversion with quinidine reversion. The successful maintenance of regular sinus rhythm after reversion depends mainly on quinidine or procaine amide. In the present study, we have attempted to maintain the patients on quinidine gluconate with a quinidine blood level of approximately 4 mg./L. (dosage has generally been between 0.33 to 0.50 gm. of quinidine gluconate every six to eight hours).j Fifty-two of 66 patients reverted to regular sinus rhythm (79%) have been successfully maintained with this regimen from one to nine months.

In the first 50 patients quinidine was not employed before reversion, the drug being started immediately following the procedure. In the last 20 patients we have instituted quinidine therapy two to three days prior to the procedure with no untoward effect noted at cardioversion. Such therapy appears to avoid early recurrence

of atria1 fibrillation in the immediate post- cardioversion period.

In this study, digitalization was employed for optimal control of rapid ventricular rates prior to cardioversion. However, it is not necessary if restoration of normal sinus rhythm is immediately indicated for other reasons. After the patient was reverted to regular sinus rhythm, maintenance digitalization was continued in the eventuality of recurrence of atria1 fibrillation (21 y0 in this series).

The anticipated gains from the restoration of normal sinus rhythm are: (1) a lessening of the incidence of systemic embolization; (2) control of in- appropriate response of the ventricular rate to exercise;6 (3) improvement in cardiac function;’ and (4) removal of subjective awareness of palpitation.

The last point needs no clarification. That embolization might be decreased is suggested by the statistical difference in embolic episodes occurring in patients with regular sinus rhythm and those in atria1 fibriI1ation.s The change of cardiac function rests on the well known clinical observation of improvement of cardiac com- pensation following restoration of sinus rhythm in some patients and a 26 per cent increase in cardiac output observed in this laboratory in a small series of patients after cardioversion.g

Selection of patients for cardioversion is a problem which will require experience to define cor- rectly. Some of the former criteria for selecting patients for restorationsa’0 and maintenance of sinus rhythm are no longer applicable. In this series there are patients with long term fibrillation (over 15 yr.), severe cardiac decompensation (class IV), and severe valvular disease (aortic and mitral) who were restored to and maintained in sinus rhythm. A previous history of quinidine failure in reversion of arrhythmias is not a contraindication for cardioversion. As demonstrated in this study, 38 of 41 quinidine failures (93%) were successfully reverted to regular sinus rhythm, and 26 (649i’,) have been maintained in regular sinus rhythm after reversion. These observations demonstrated that the ability of quinidine to maintain regular sinus rhythm, once it is established, does not appear to be related to its ability to revert the arrhythmia.

Several situations do not appear to indicate the immediate use of cardioversion. Atria1 fibrillation occurring in the course of acute myocardial infarction tends to be self-limiting and, unless there are other considerations, cardio-



version is not indicated in the first several weeks. Because of the danger of dislodging an atria1 thromhus, we have avoided cardioversion within eight weeks of a known episode of embolization. Atria1 fibrillation occurring in the course of digitalis intoxication is treated by removal of the drug. However, if the rapid rate is contributing to decompensation, cardioversion does not appear contraindicated. In patients with thyrotoxicosis the ventricular rate is controlled with digitalis and antithyroid medication until the patient is euthyroid. When surgical intervention is anticipated in the immediate future for patients with mitral stenosis, cardioversion is deferred until at least six weeks after surgery. Some patients with ischemic heart disease are actually benefited by atria1 fibrillation because of the slow ventricular rate associated with it which cannot be obtained when they are in sinus rhythm.

Emergency Indications: Cardioversion for atria1 arrhythmias is helpful in three emergency situations. First, supraventricular tachycardia associated with acute myocardial infarction may not always be controlled with digitalization and other supportive measures; in this case cardioversion may reverse the worsening clinical situation. We have encountered two such occasions. In both instances cardioversion successfully and promptly restored the cardiac rhythm and blood pressure to normal with dramatic improvement of the clinical status. Secondly, when the electrocardiographic dif- ferentiation of supraventricular versus ventricular tachycardia is difficult or impossible, cardioversion instead of drug therapy can be employed with safety, since it is effective in either rhythm disturbance. Third, during the treatment of supraventricular tachycardia, when the difficulty arises of determining if the patient is under- or overdigitalized, cardioversion can be used, and the error of further intoxicating an already overdigitalized patient can be avoided.

The serious complications encountered have been small in number. One of the major risks is that due to anesthesia. We attribute the in- frequent complications to adhering to periods of brief and light anesthesia. With experience we have found it possible to use even lighter anesthesia (analgesia) of brief duration (less than 5 min.). The second major danger is that of embolization. The 3 per cent incidence in this series is comparable to or higher than that encountered with quinidine conversion of atria1 fibrillation.lo The value of anticoagula-

JULY 1964

tion in reducing this figure is unsettled. This problem is currently under investigation.

For predicting the success of maintain&< regular sinus rhythm after cardioversion, certain observations seem worthy of comment. Age of the patients, 19 years to 80 years, does not seem to be important in determining whether regular sinus rhythm may be maintained. The type of cardiac disease does not appear to be an important determinant. Successful maintenance of regular sinus rhythm is not significantly different for rheumatic heart disease (74$&,), ischemic heart disease (79oj,) and hypertensive cardiovascular disease (67%). The type of valvular disease does appear to be important. Maintenance is more successful in pure mitral stenosis (84%) than in mitral insufficiency or multiple valvular involvement (647&). The duration of atria1 fibrillation also seems to influence the results of successful maintenance of sinus rhythm. For example, when atria1 fibrillation was less than two years in duration reversion and maintenance of regular sinus rhythm was possible in 83 per cent of cases, while in those with atria1 fibrillation for more than three years, only 47 per cent were maintained in regular sinus rhythm. The most reliable sign indicating ultimate failure of maintenance of sinus rhythm has been the prompt recurrence of atria1 fibrillation in the first month following successful cardioversion despite adequate quinidine therapy. Multiple attempts at maintaining sinus rhythm are not indicated once a patient has on two occasions reverted to atria1 fibrillation in the early postconversion period.

&MMARY

Synchronized direct current countershock, “cardioversion,” was used in 70 patients on 94 occasions for reversion of atria1 fibrillation or flutter. The method and anesthetic technics are described. A modification of the size and location of the electrode has decreased the incidence of minor discomfort resulting from the procedure and lowered the amount of energy necessary for successful cardioversion.

In 90 of 94 episodes, or in 66 of 70 patients, the arrhythmia was restored to sinus rhythm. With a follow-up period of from 1 to 9 months, 52 of 66 patients (79%) remained in sinus rhythm. Fourteen patients (21%) reverted to atria1 fibrillation despite multiple cardioversions and maximally tolerated quinidine therapy.

Certain factors appear to decrease the chances of maintaining sinus rhythm: duration of

100 Morris, Kong, North and McIntosh

fibrillation, type of valvular lesion, functional classification and previous quinidine failure.

The advantages anticipated with the restoration of sinus rhythm are discussed. The emergency indication and contraindications are out- lined. A broad policy of selection of patients for cardioversion is suggested. The reasons for this approach are the high degree of acute success (94%), the low incidence of complications (5ojo) and SUCCESS in maintaining sinus rhythm (79yO) for a short follow-up period.

REFERENCES

1. LOWN, B.; AMARASINGHAM, R., NEUMAN, J. and BERKOVITZ, B. U. Use of synchronized direct current countershock in treatment of cardiac arrhythmias. Presented at 54th Annual Meeting of American Society for Clinical Investigation, Atlantic City, N. J., April 30, 1962.

2. LINENTHAL, A. J., ULICK, S. and PATTERSON, L. A. Fluorometric measurement of plasma quinidine aid its coIrzlation with clinical effects in man. J. C/in. Invest., 26: 1188, 1947.

3. LOWN, B., PERLROTH, M. G., KAIDBAY, S., ABE, T. and HARKEN, D. E. “Cardioversion” of atria1 fibrillation. New En,&md J. Med., 269: 325,

1963.

4. ( )K.AN. S.. DAVIES. J. P., WEINBKEN, I. and TAGGAR.I., P. Conversion of atria1 fibrillation to sinus rhythm by direct current shock. Lancet, 2: 159, 1963.

.5. SOKOL.OM., M. and BALL, R. F. Factors influencing conversion of chronic atria1 fibrillation with special reference to serum quinidine concentration. Cwculation, 14: 568, 1956.

6. WETHERBEE, D. G., BROWN, M. G. and HOLEMAN, D. Ventricular rate response following exercise during atria1 fibrillation and after conversion to normal sinus rhythm. Am. J. M. SC., 223: 667, 1952.

7. GILBERT, R., EICH, R. H., SMULYAN, H., KEIGHLEY, J. and AUCHINCLOSS, J. H. Effect on circulation of conversion of atria1 fibrillation to sinus rhythm. Circulation, 21: 1079, 1963.

8. DALEY, R., MATTINGLY, T. W., HOLT, C. L., BLAND, E. F. and WHITE, P. D. Systemic arterial embolization in rheumatic heart disease. Am. Heart J., 42: 566, 1951.

9. MORRIS, J. J., JR., ENTMAN, M., THOMPSON, H. K.,

WORTH, W. C. and MCINTOSH, H. D. Cardiac output in atria1 fibrillation and sinus rhythm. Circulation, 28: 772, 1963.

10. GOLDMAN, M. J. Management of chronic atria1 fibrillation: Indications for and methods of conversion to sinus rhythm. Prog. Cardiovas. Dis., 2: 465, 1960.


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Experience with “cardioversion” of atrial fibrillation and flutter