Late Recovery of Conduction following Surgically Induced Atrioventricular Block Thomas W. Smith, M.D., James C. McFarland, M.D., Mortimer J. Buckley, M.D., and W. Gerald Austen, M.D. U se of long-term ventricular pacing devices has been advocated to improve the poor prognosis of patients suffering chronic complete heart block as a complication of cardiac surgery [8, 121. This report documents the rare occurrence of spontaneous return of normal atrioventricular (A-V) conduction more than eight months following onset of surgically induced complete heart block and emphasizes the resultant hazard from competition with a fixed-rate ventricular pacemaker by conducted sinus beats. The patient had been cyanotic from birth with typical physical findings of tetralogy of Fallot. At age 11, because of frequent squatting, exercise intolerance, and syncope, a left subclavian artery to pulmonary artery anastomosis was performed, with symptomatic improvement. She was admitted to Massachusetts General Hospital on June 1, 1965, at age 22, with right femoral arterial and right cerebral emboli. Ligation of the inferior vena cava was carried out for suspected paradoxical emboli from the lower extremities, and no further embolic episodes occurred. Cardiac catheterization and right ventricular angiography on April 15, 1966, confirmed the diagnosis of tetralogy of Fallot with severe infundibular pulmonic stenosis and a large high ventricular septal defect with 50 to 60% overriding of the aorta. The electrocardiogram at this time, as previously, showed normal sinus rhythm with incomplete right bundle-branch block (Fig. 1). Because of increasing exercise intolerance, polycythemia, and the history of systemic emboli, intracardiac correction was undertaken on January 17, 1967. At operation, after ligation of the left subclavian artery to pulmonary artery shunt, the patient was placed on total cardiopulmonary bypass. A longitudinal right ventriculotomy was made between coronary artery branches, paralleling the anterior descending artery and extending up to the pulmonary valve annulus. The infundibular obstruction was resected widely. The ventricular septal defect was then identified and the initial sutures were placed in the septal leaflet of the tricuspid valve, taking care to avoid the region of the main bundle. Normal sinus rhythm was present after all these sutures were placed. As the retractors were being moved about in order to place sutures along the anterior and superior From the Cardiac and Cardiac Catheterization Units, Department of Medicine, and the Surgical-Cardiovascular Unit, Department of Surgery, Massachusetts General Hospital, and the Departments of Medicine and Surgery, Harvard Medical School, Boston, Mass. Supported in part by U.S. Public Health Service Grant Nos. HE-5196-12 and HE-06664 (HEPP). Accepted for publication Oct. 16, 1969. Address reprint requests to Dr. Austen, Department of Surgery, Massachusetts General Hospital. Boston, Mass. 02114. 372 THE ANNALS OF THORACIC SURGERY
CASE REPORT: Late Recovery of Conduction 1-46-67 I m ovr avl OVF STD V3R V4R FIG. 1. Electrocardiogram recorded on day prior to operation. Normal atrzoventricular conduction and incomplete right bundle-branch block are present. margins of the ventricular septa1 defect, A-V block was noted to occur. No sutures were removed, since none could be identified as having caused the block. The remaining sutures were placed, a Teflon patch was inserted, and a pulmonic valvulotomy was performed to complete the correction. A-V block persisted from the time it was first noted, and temporary epicardial pacing wires were used in the early postoperative period to maintain an adequate ventricular rate. The spontaneous rhythm at this time (Fig. 2 4 was idioventricular (or possibly A-V junctional) at a rate of 45 beats per minute, with complete A-V block which persisted despite treatment with atropine and isoproterenol, and mild hypokalemia induced by oral diuretics. A permanent fixed-rate Cordis unipolar pervenous VOL. 9, NO. 4, APRIL, 1970 373
!--Kc+ccKcu-I SMITH, McFARLAND, BUCKLEY, AND AUSTEN +!!!!! I.!!!!!! :! ~ A 2-9-67 I D I- 12-68 FIG. 2. Postoperative rhythm strips: (A) 23 days after operation, complete A-V block; (B) following insertion of permanent pervenous endocardial fixed-rate pacemaker; (C) 8% months after operation, no evidence of A-V conduction; (D) 12 months after operation, first demonstration of intermittent sinus captures; (El 16 months after operation, emergency ward tracing showing ventricular tachycardia and dissociated pacemaker artifact. endocardial pacemaker (Model No. IIIC)+ was implanted prior to discharge (Fig. 2B) and was found to be pacing reliably on follow-up visits at intervals of one to three months, with no clinical or electrocardiographic evidence of spontaneous A-V conduction as late as September 29, 1967 (Fig. 2C). On January 12, 1968, 12 months after onset of complete A-V block, the patient's rhythm was noted to be irregular, and an ECG showed intermittent conduction of sinus beats with a PR interval of 0.20 second and left bundlebranch block (Fig. 20). She was followed without further intervention to determine stability of A-V conduction, but on May 20, 1968, she was brought to the emergency ward following an episode of collapse and cyanosis. An ECG showed ventricular tachycardia with pacemaker artifact present but not capturing (Fig. 2E). Treatment with lidocaine and procaine amide resulted in reversion to a predominantly paced rhythm with intermittent sinus captures. On removal of the fixed-rate pulse generator the spontaneous rhythm was normal sinus (PR interval 0.18 second) with left bundle-branch block. An American Optical demand pulse generator (Model No. 281001)t was substituted for the fixed-rate device. Thereafter, the patient has remained in normal sinus rhythm with left bundle-branch block and left atis deviation with no evidence of ectopic ventricular activity (Fig. 3). COMMENT The incidence of chronic complete heart block as a complication of cardiac surgery has been substantially reduced in recent years as a result of increased awareness of the surgical anatomy of the conduction system [3, 121. Nevertheless, disturbances of conduction during intracardiac repair of endocardial cushion defects or high ventricular septa1 defects with or without associated tetralogy of Fallot continue to occur [lo, 11, 14, 151. Fortunately, reliable temporary pacing techniques are 'Cordis Corp.. Miami, Fla. tamerican Optical Corp.. Medical Div., Bedford. Mass. 374 THE ANNALS OF THORACIC SURGERY
CASE REPORT: Late Recovery of Conduction I- ' I - I 12-2 6-60 II m avr avl av F Lead JI FIG. 3. Electrocardiogram recorded 7 months after replacement of fixed-rate pulse generator by demand unit. Normal sinus rhythm with left bundle-branch block and left axis deviation is present. now available [7], and the majority of patients regain normal A-V conduction within the first four weeks of the postoperative course 18, 16, 171. Later than this, first- or second-degree alternating with third-degree A-V block has been observed [8], but return of normal A-V conduction is rare [5, 8, 123. We have found in the literature only a single documented case of spontaneous restoration of normal sinus rhythm later than two months after onset of complete block during open cardiac surgery [l].
SMITH, McFARLAND, BUCKLEY, AND AUSTEN The mortality rate of patients with chronic surgically induced heart block was as high as 100% in early series [6, 8, 12, 141, but this rate would seem to have been decreased with advances in artificial pacing techniques [9]. Permanent pacing devices now are used routinely in many centers if A-V block persists beyond the third or fourth postoperative week [4, 8, 12, 131. The possibility of inducing ventricular arrhythmias when conducted beats compete with a fixed-rate ventricular pacing device has been well documented [2], but this hazard is not usually of concern in chronic surgically induced complete A-V block because of the rarity of late restoration of A-V conduction in this setting. The clinical course and serial electrocardiograms of the patient reported here indicate intraoperative damage to the left bundle branch, with complete A-V block resulting from additional damage to the main bundle or to the previously compromised right bundle branch. After more than eight months of fixed-rate ventricular pacing, resumption of A-V conduction resulted in competition between paced and conducted beats, followed by a life-threatening episode of ventricular tachycardia. Although not proved conclusively, the complete absence of ventricular arrhythmias before or since the period of competitive pacing strongly suggests a causal relationship. Despite the great rarity of resumption of A-V conduction this late after onset of complete block during cardiac surgery, the potentially grave consequences of competitive pacing should be kept in mind if a fixed-rate pacemaker is employed. SUMMARY The rare occurrence of spontaneous return of normal A-V conduction more than eight months after onset of complete A-V block during open surgical repair of tetralogy of Fallot is reported. Ventricular tachycardia occurred during the period when conducted sinus beats competed with a fixed-rate ventricular pacing device, suggesting that demand pacing may be preferable in the long-term management of surgically induced complete heart block. REFERENCES 1. Aytac, A., and Tuncali, T. The use of temporary external pacemaker to control surgically produced complete atrio-ventricular block during open heart surgery. Turk. J. Pediat. 9:65, 1967. 2. Bilitch, M., Cosby, R. S., and Cafferky, E. A. Ventricular fibrillation and competitive pacing. New Eng. J. Med. 276:598, 1967. 3. Gadboys, H. L., and Litwak, R. S. Experimental and clinical aspects of surgical heart block. Progr. Cardiovasc. Dis. 5:566, 1964. 4. Gannon, P. G., Sellers, R. D., and Kanjuh, V. I. Complete heart block following replacement of the aortic valve. Circulation 33 (Suppl. 1): 152, 1966. 5. Hurwitz, R. A., Riemenschneider, T. A., and Moss, A. J. Chronic postoperative heart block in children. Amer. J. Cardiol. 21:185, 1968. 376 THE ANNALS OF THORACIC SURGERY
CASE REPORT: Late Z2ecovel.y of Conduction 6. Lauer, R. M., Ongley, P. A., DuShane, J. W., and Kirklin, J. W. Heart block after repair of ventricular septa1 defect in children. Circulation 22: 526, 1960. 7. Lillehei, C. W., Levy, M. J., Bonnabeau, R., Long, D. M., and Sellers, R. D. Direct wire electrical stimulation for acute postsurgical and postinfarction complete heart block. Ann. N.Y. Acad. Sci. 111:938, 1964. 8. Lillehei, C. W., Sellers, R., Bonnabeau, R., and Eliot, R. Chronic postsurgical complete heart block. J. Thorac. Cardiovasc. Surg. 46:436, 1963. 9. Lillehei, C. W., Sellers, R. D., and Eliot, R. S. Implanted cardiac pacemakers: Experience with 100 consecutive patients. Amer. J. Surg. 114:69, 1967. 10. Lindesmith, G. G., Meyer, B. W., and Chapman, N. The surgical repair of endocardia1 cushion defects. Ann. Thorac. Surg. 2:399, 1966. 11. Liu, L., Griffiths, S. P., and Gerst, P. H. Implanted cardiac pacemakers in children. Amer. J. Cardiol. 20:639, 1967. 12. McGoon, D. C., Ongley, P. A., and Kirklin, J. W. Surgical heart block. Amer. J. Med. 37:749, 1964. 13. Ongley, P. A. Cyanotic congenital heart disease. Pediat. Clin. N. Amer. 11: 269, 1964. 14. Rastelli, G. C., Ongley, P. A., and Kirklin, J. W. Surgical repair of the complete form of persistent common atrio-ventricular canal. J. Thorac. Cardiovasc. Surg. 55:299, 1968. 15. Rengel, A., Garcia Cornejo, M., and Rotberg, T. The frequency of complete atrio-ventricular block as a complication of surgery in isolated interventricular communication. Arch. Znst. Cardiol. Mex. 37:439, 1967. 16. Sayed, H. M. Complete heart block following open heart surgery. J. Cardiovasc. Surg. (Torino) 6:426, 1965. 17. Taylor, D. E., and Hider, C. F. Myocardial ischemia and defects of atrioventricular conduction associated with cardiac surgery. Thorax 22:38, 1967.