Duration of complete atrioventricular block after congenital heart disease surgery

Abstract

Complete heart block (CHB) may complicate surgery for congenital heart disease and is a category I indication for pacemaker implantation when conduction does not recover.1Dreifus L.S. Fisch C. Griffin J.C. Gillette P.C. Mason J.W. Parsonnet V. Guidelines for implantation of cardiac pacemakers and antiarrhythmia devices.J Am Coll Cardiol. 1991; 18: 1-13Abstract Full Text PDF PubMed Scopus (134) Google Scholar The proper duration of observation before proceeding to permanent pacemaker implantation is still ill defined, but is broadly accepted as 10 to 14 days following surgery.1Dreifus L.S. Fisch C. Griffin J.C. Gillette P.C. Mason J.W. Parsonnet V. Guidelines for implantation of cardiac pacemakers and antiarrhythmia devices.J Am Coll Cardiol. 1991; 18: 1-13Abstract Full Text PDF PubMed Scopus (134) Google Scholar, 2Driscoll D.J. Gillette P.C. Hallman G.L. Cooley D.A. McNamara D.G. Management of surgical complete atrioventricular block in children.Am J Cardiol. 1979; 43: 1175-1180Abstract Full Text PDF PubMed Scopus (34) Google Scholar The timing of permanent pacemaker implantation for postoperative CHB is of considerable practical importance, because delayed implantation results in added cost for hospital observation in otherwise stable patients, whereas too early implantation may result in an unnecessary operation and implantation of expensive devices resulting in additional risks and expense. We prospectively followed patients with CHB to better establish the timing for recovery of atrioventricular (AV) conduction, and to determine if there were factors that reliably predict permanent CHB. This information may be helpful in deciding which patients should receive a permanent pacing system, and may refine the optimal timing of such implants. All patients undergoing cardiac surgery between January 1991 and January 1994 who had CHB lasting ≥4 hours were followed prospectively. Patients with preexisting second or third degree AV block, or a history of transient AV block at any prior operation, were excluded. Temporary pacemaker wires were routinely placed at the time of the operation. During the period of postoperative observation, temporary pacing was suspended briefly on at least a twice daily basis to determine the status of AV conduction. All patients were monitored in the cardiac intensive care unit until resolution of heart block or permanent pacemaker system implantation. The timing of permanent pacing system implantation was left to the discretion of the primary surgeon. For analysis of time to recovery of AV conduction, Kaplan-Meier survival curves were used (STATA statistical software, Version 3.0, Computing Resource Center, Santa Monica, California). Discrete variables were compared using the Fisher’s exact test and continuous variables were compared with the t test (SAS statistical software, version 6.04; SAS Institute Inc., Cary, North Carolina). Statistical significance was assessed by a p value of <0.05. During the 3-year study period, there were 2,698 total cardiac surgeries performed, with 1,964 (73%) involving cardiopulmonary bypass. Fifty-four operations were complicated by CHB, representing 2% of total cardiac operations and 3% of “pump” cases. The greatest risk for CHB occurred with surgery for left ventricular outflow tract obstruction (occurring in 8 of 46 procedures, 17%). Patients with l-transposition of the great arteries (L-TGA) also had a high risk of CHB (5 of 44 patients, 11%). The incidence was less, but still significant, after ventricular septal defect closures (18 of 474 procedures, 4%) or tetralogy of Fallot repair (6 of 206 operations, 3%). Fifty of the 54 patients (93%) were alive at follow-up through postoperative day 30. There were 4 early deaths due to hemodynamic problems: 2 patients still in CHB on postoperative days 1 and 11, and 2 patients who had recovered conduction ≥7 days before their deaths. One child, from outside the country, was lost to follow-up after his discharge on postoperative day 7; he still had CHB and a pacemaker. Patients were divided into 2 groups for analyses (Table I). Group 1 patients recovered AV conduction in the first 30 days following surgery; group 2 patients did not recover AV conduction, or did so at >30 days following surgery. The 2 patients who died after having recovered AV conduction were included in group 1. For statistical purposes, the 2 patients who died and still had CHB, and the 1 lost to follow-up were not included in either group.TABLE ICharacteristics of Patients Who Recovered Atrioventricular (AV) Conduction (group 1) and Did Not Recover AV Conduction (group 2) Within 30 Days of Congenital Heart Disease SurgeryGroup 1Group 2No. of patients3219Age (yrs)2.1 ± 0.54.6 ± 1.7Weight (kg)9.4 ± 1.315.9 ± 3.8DiagnosisVentricular septal defect135Tetralogy of Fallot52Left ventricular outflow tract obstruction44L-TGA32Other76Cardiopulmonary bypass time (min)163 ± 7134 ± 11Pre-op first degree AV block31Pre-op wide QRS44New post-op wide QRS escape114Ventricular escape rate81 ± 757 ± 11 Open table in a new tab Clinical and surgical parameters were compared between these 2 groups, but there was no significant difference in any variable tested (Table I). Although those who recovered AV conduction tended to have higher ventricular escape rates on postoperatiave day 1, the difference was not statistically significant (p = 0.08). The timing of recovery of AV conduction is shown in Figure 1. The 2 patients who died, and the 1 lost to follow-up, and still with CHB, were censored at the time when no further data were available. AV conduction returned within 30 days of surgery in 32 of the 51 study patients (63%), with 50% of all patients having recovered AV conduction by postoperative day 7. Of those patients who regained AV conduction within the first month of surgery, 42% did so by postoperative day 2, 81% by postoperative day 7, and 97% by postoperative day 9. All patients whose AV conduction recovered in the first month following surgery did so by postoperative day 21. Importantly, 3 of the 32 patients (9%) who had initial recovery of AV conduction also had some subsequent deterioration of AV conduction with second degree AV block; however, none of these patients reverted to complete block. One patient “recovered” normal AV conduction on postoperative day 9 following tetralogy of Fallot repair, but developed persistent Mobitz type II AV block by postoperative day 57. Another patient, who underwent patch closure of a posterior malalignment ventricular septal defect, regained AV conduction on postoperative day 1 (with a normal PR interval, complete right bundle branch block, and a left anterior hemiblock), but developed Mobitz type II AV block 2 years after surgery. A third patient, who regained AV conduction on day 8 following patch closure of a subpulmonary ventricular septal defect, had intermittent Mobitz type II AV conduction and intermittent CHB 7 months after surgery. Permanent pacemakers were implanted in 31 patients (57%) between postoperative days 2 and 32 (mean ± SD; 10 ± 12 days; median 7). Permanent pacemakers did not have to be implanted because of failure or unacceptable pacing thresholds of the temporary transcutaneous ventricular pacing systems. Of the patients who received a permanent pacemaker system, 11 (39%) had recovery of AV conduction after the pacemaker implantation. CHB is an uncommon complication of congenital heart disease surgery, occurring in about 3% of operations involving cardiopulmonary bypass. The operations in this series complicated by CHB were similar to prior studies,2Driscoll D.J. Gillette P.C. Hallman G.L. Cooley D.A. McNamara D.G. Management of surgical complete atrioventricular block in children.Am J Cardiol. 1979; 43: 1175-1180Abstract Full Text PDF PubMed Scopus (34) Google Scholar, 3Hurwitz R.A. Riemenschneider T.A. Moss A.J. Chronic postoperative heart block in children.Am J Cardiol. 1968; 21: 185-189Abstract Full Text PDF PubMed Scopus (21) Google Scholar, 4Liu L. Griffeths S.P. Gerst P.H. Implanted cardiac pacemakers in children a report of their application in five patients.Am J Cardiol. 1967; 20: 639-647Abstract Full Text PDF PubMed Scopus (18) Google Scholar, 5Murphy D.A. Tynan M. Graham G.R. Bonham-Carter R.E. Prognosis of complete atrioventricular dissociation in children after open-heart surgery.Lancet. 1970; i: 750-752Abstract Scopus (36) Google Scholar, 6Squarcia U. Merideth J. McGoon D.C. Weidman W.H. Prognosis of transient atrioventricular conduction disturbances complicating open heart surgery for congenital heart defects.Am J Cardiol. 1971; 28: 648-652Abstract Full Text PDF PubMed Scopus (34) Google Scholar, 7Lillehei C.W. Sellers R.D. Bonnabeau R.C. Eliot R.S. Chronic post-surgical complete heart block.J Thorac Cardiovasc Surg. 1963; 46: 436-456PubMed Google Scholar with the highest incidence after repair of left ventricular outflow tract obstruction and ventricular inversion (L-TGA). Most patients with CHB regain normal AV conduction; 63% of our patients did so in the first postoperative month. Others have reported recovery of AV conduction in 55% to 100% of children with CHB.3Hurwitz R.A. Riemenschneider T.A. Moss A.J. Chronic postoperative heart block in children.Am J Cardiol. 1968; 21: 185-189Abstract Full Text PDF PubMed Scopus (21) Google Scholar, 5Murphy D.A. Tynan M. Graham G.R. Bonham-Carter R.E. Prognosis of complete atrioventricular dissociation in children after open-heart surgery.Lancet. 1970; i: 750-752Abstract Scopus (36) Google Scholar, 6Squarcia U. Merideth J. McGoon D.C. Weidman W.H. Prognosis of transient atrioventricular conduction disturbances complicating open heart surgery for congenital heart defects.Am J Cardiol. 1971; 28: 648-652Abstract Full Text PDF PubMed Scopus (34) Google Scholar, 7Lillehei C.W. Sellers R.D. Bonnabeau R.C. Eliot R.S. Chronic post-surgical complete heart block.J Thorac Cardiovasc Surg. 1963; 46: 436-456PubMed Google Scholar Our findings indicated that while late recovery of AV conduction can occur,5Murphy D.A. Tynan M. Graham G.R. Bonham-Carter R.E. Prognosis of complete atrioventricular dissociation in children after open-heart surgery.Lancet. 1970; i: 750-752Abstract Scopus (36) Google Scholar, 6Squarcia U. Merideth J. McGoon D.C. Weidman W.H. Prognosis of transient atrioventricular conduction disturbances complicating open heart surgery for congenital heart defects.Am J Cardiol. 1971; 28: 648-652Abstract Full Text PDF PubMed Scopus (34) Google Scholar, 8Averill KH, Vogel JHK, Pryor R, Blount SG, Jr. Complete heart block following intracardiac surgery: reversion to normal sinus rhythm after twenty-five months.Google Scholar >95% of patients who regain AV conduction do so by postoperative day 9. Thus, there seems to be minimal benefit in delaying permanent pacemaker implantation >9 days following surgery. Of note, this study was unable to identify any clinical variables that could reliably predict which patients were most likely to recover AV conduction. Finally, it is important to note that even patients who appear to recover from CHB early have the potential for late development of AV conduction abnormalities, such as Mobitz II AV block. This was seen in 3 of our patients, 9% of those with transient CHB, and has been reported by others.7Lillehei C.W. Sellers R.D. Bonnabeau R.C. Eliot R.S. Chronic post-surgical complete heart block.J Thorac Cardiovasc Surg. 1963; 46: 436-456PubMed Google Scholar, 9Moss A.J. Klyman G. Emmanouilides G.C. Late onset complete heart block newly recognized sequela of cardiac surgery.Am J Cardiol. 1972; 30: 884-887Abstract Full Text PDF PubMed Scopus (61) Google Scholar, 10Krongrad E. Prognosis for patients with congenital heart disease and postoperative intraventricular conduction defects.Circulation. 1978; 57: 867-870Crossref PubMed Scopus (97) Google Scholar This might particularly be the case for patients with transient CHB who regain AV conduction but have a residual intraventricular conduction abnormality.10Krongrad E. Prognosis for patients with congenital heart disease and postoperative intraventricular conduction defects.Circulation. 1978; 57: 867-870Crossref PubMed Scopus (97) Google Scholar Thus, patients who have had transient CHB should have routine evaluations with electrocardiograms during extended follow-up to assess AV conduction. In summary, heart block following surgery for congenital heart disease resolves in 2/3 of patients, usually by the ninth postoperative day. Patients with transient postoperative CHB should be followed for potential development of late AV conduction abnormalities.