Occurrence Of Complete Heart Block Research Articles

Transcatheter Closure of Perimembranous Ventricular Septal Defect Using KONAR-MF™: A Multicenter Experience.

Transcatheter closure of perimembranous ventricular septal defect (PmVSD) is an established procedure. However, the occurrence of complete heart block limits its scope. The newer KONAR-MF™ occluder has specific design characteristics that may improve the safety of PmVSD closure. The objective of the studywas to describe the efficacy and mid-term follow-up of transcatheter closure of PmVSD using KONAR-MF™. The study was conducted prospectively in 3 Indian centers (January 2018-December 2022). PmVSD closure was done by both antegrade and retrograde methods, and patients were followed up at 1, 3, 6, 12months, and annually after that. 121 out of 123 patients were included with the following characteristics: median age 4.4 (0.18-40) years; weight 15 (2.1-88) kg; mean Qp/Qs ratio 1.87 ± 0.52 and pulmonary artery mean pressure: 22 ± 6.9mmHg. The procedure was successful in all but 3; the device was removed due to significant residual shunt (n = 2) and new development of aortic regurgitation (AR) (≥ mild) in 1. The median defect size was 5.2 (2.5-12) mm. Device sizes from 6/4 to 14/12 were deployed (median fluoroscopy time 13.3min; range 3.6-47.8). Shunt occlusion rates were 90%-Immediate, 95%-pre-discharge, and 97%-1month, with no instances of complete heart block after the procedure and during follow-up. Six had new onset AR (mild: 2, trivial 4), and one had increased tricuspid regurgitation. All patients were well during follow-up (median: 20months; range: 6-46). The new KONAR-MF™ occluder appears to be a promising and safe alternative for the closure of the PmVSD; further long-term follow is merited.

Frequency of Complete Heart Block (CHB) and Its Association with Hypertension and Diabetes Mellitus in Patients with Anterior Wall Myocardial Infarction (AWMI)

Background: The presence of conduction defects complicates AMI frequently and is associated with increased short and long term mortality rates. The occurrence of complete heart block in anterior wall myocardial infarction is important because it indicates that infarction is extensive and may result in cardiac failure or death.
 Objective: To determine the frequency of complete heart block (CHB) in patients presented with anterior wall myocardial infarction (AWMI).
 Material and Methods: Total 152 patients with AWMI were included. The history of the patients was taken regarding hypertension, diabetes mellitus, smoking, family history of CAD, and chronic kidney disease. Study outcome, complete heart block, was assessed and recorded.
 Results: There were 81.6% male and 18.4% female patients. Mean age was 56.25±9.81 years. Total 9.2% patients were found with chronic kidney disease. In our study, 12.5% patients were found with complete heart block. Significant association of complete heart block was observed with hypertension and diabetes mellitus while no significant association was observed with gender, age, smoking, CAD family history, and chronic kidney disease.
 Conclusion: Our study results showed 12.5% patients observed complete heart block. Hypertension and diabetes mellitus are found as the significant risk factors of complete heart block.

Complete heart block in patients infected with SARS-CoV-2: A case series from a developing country

Coronavirus Disease 19 (COVID-19) has led to a global pandemic and has been the center of attention across the entire medical community. This novel virus was initially thought to affect primarily the respiratory system, but now it is evident that it has a multitude of effects on the human body. Our point of interest is to establish the effect of COVID-19 infection on the conducting system of the heart. We present a case series of four patients who developed complete heart block (CHB) shortly after being infected with COVID-19 without any previous known risk factors of complete heart block. There have only been a few previous case reports on the occurrence of CHB in COVID-19 patients highlighting the importance and the need of our case series to the literature of cardiovascular outcomes in COVID-19 patients. Our case series highlight that COVID-19 can indeed affect the conduction system of the heart and cause CHB in patients who then recovered spontaneously further elucidating the transient nature of cardiovascular effects caused by the novel virus.

Progressive involvement of cardiac conduction system in paediatric patients with Kearns-Sayre syndrome: how to predict occurrence of complete heart block and sudden cardiac death?

The aims of this study are to evaluate the progressive involvement of the cardiac conduction system in the Kearn-Sayre syndrome (KSS) and to establish criteria for the prevention of episodes of syncope or sudden cardiac death. This is a prospective monocentric study including KSS patients, with diagnosis based on clinical manifestations, muscle biopsy, and genetic tests, before the age of 18. All patients underwent cardiac screening examination with 12-lead electrocardiogram (ECG), 24-h Holter monitoring, and pacemaker (PM) interrogation twice a year. Fifteen patients (nine males, mean age 16.6 ± 3.9 years) with a sporadic KSS were recruited. All subjects manifested at least one of the intraventricular conduction defects (IVDs): 1 right bundle branch block (RBBB), 2 left anterior fascicular block (LAFB), 11 a bi-fascicular block (RBBB + LAFB), and 1 left posterior fascicular block. Most children with bi-fascicular block developed LAFB before the RBBB (P = 0.0049). In six patients, IVD degenerated into atrioventricular block (AVB). Endocavitary PM was implanted in 11 patients (6 with AVB and 5 with a bi-fascicular block), while an implantable cardioverter-defibrillator only in one patient with a non-sustained ventricular tachycardia. Four died at mean age of 14.7 ± 2.6 years, but none of them suddenly. Even a 'simple' ECG can predict the arrhythmic risk and the occurrence of catastrophic events in young patients with KSS. Left anterior fascicular block precedes RBBB in determining the bi-fascicular block and this can predict an inexorable progression of the conduction defects even in a short time. Pacemaker implantation may be indicated in these patients since the first bi-fascicular block manifestation.

Temporal Occurrence of Arrhythmic Complications After Alcohol Septal Ablation.

The temporal occurrence of arrhythmic complications after alcohol septal ablation (ASA) is unclear. As a result, the appropriate time to monitor patients after ASA is controversial. The purpose of this study is to determine the temporal occurrence of complete heart block (CHB) and ventricular tachyarrhythmia (VT) after ASA to better understand when patients can be safely discharged. Consecutive patients treated with ASA for hypertrophic cardiomyopathy from 2003 to 2019 at a tertiary referral center were reviewed retrospectively. The incidence and timing of CHB or sustained VT within 30 days post-ASA were assessed. A total of 243 patients were included in this study. Mean maximal septal thickness was 19.0±3.9 mm, and total volume of ethanol injected was 1.7±0.6 mL. CHB occurred in 59 (24.3%) patients, including transient CHB in 33 (13.6%) and permanent in 26 (10.7%). The initial episode of CHB occurred within 24 hours post-ASA in 51 (21.0%) patients, between 24 and 48 hours in 3 (1.2%), between 48 and 72 hours in 3 (1.2%), and after 72 hours in 2 (0.8%). New permanent pacemaker was placed in 46 (18.3%). Presence of baseline bundle branch block and age ≥70 were significantly associated with CHB but not CHB presenting after 24 hours. VT occurred in 3 (1.2%) patients, including 1 (0.4%) within 24 hours, 1 (0.4%) between 24 and 48 hours, and 1 (0.4%) after 72 hours. VT required cardioversion in 2 patients and new implantable cardioverter-defibrillator placement in 2. The incidence of CHB or VT presenting after 72 hours post-ASA was low. These findings suggest that timely discharge of patients without evidence of early conduction disturbances after ASA can be considered as a potentially safe management strategy, especially in patients without preexisting conduction abnormalities.

Predictive role of ventricular repolarization parameters for the occurrence of complete heart block in patients undergoing transcatheter aortic valve implantation.

BackgroundWe investigated the role of ventricular repolarization parameters to predict complete atrioventricular block in patients undergoing transcatheter aortic valve implantation (TAVI).MethodsA total of 150 patients undergoing TAVI due to severe aortic stenosis were included in this retrospective cohort study. Patients were assigned in two groups based on the presence (n: 49) or absence (n: 101) of complete atrioventricular block after TAVI. Ventricular repolarization intervals (QT, QTc, JT, JTc, TP‐E), indices (QT dispersion), and ratios (TP‐E/QT, TP‐E/QTc, TP‐E/JTc) were measured.ResultsElectrocardiographic repolarization parameters such as Tp‐e interval: 74.2 ± 5.1 versus 59.2 ± 6.1 ms, p < .001; QTc interval: 397.6 ± 3.4 versus 368.1 ± 7.8 ms, p < .001; JTc interval: 317.4 ± 11.3 versus 291.1 ± 6.7 ms, p < .001; Tp‐e/QT ratio: 0.28 ± 0.04 versus 0.20 ± 0.04, p < .001; Tp‐e/QTc ratio: 0.29 ± 0.04 versus 0.19 ± 0.03, p < .001; Tp‐e/JT ratio: 0.32 ± 0.03 versus 0.23 ± 0.03, p < .001; Tp‐e/JTc ratio: 0.30 ± 0.02 versus 0.2 ± 0.03, p < .001; and QT dispersion: 34.4 ± 3.0 versus 17.8 ± 3.6 ms, p < .01 were significantly higher in post‐TAVI permanent pacemaker group. In a univariate regression analysis, pulmonary artery pressure, heart rate, coronary artery disease, Tp‐e/QTc, Tp‐e/JTc, and PR interval were significantly associated with complete heart block. Tp‐e/JTc (OR 0.373, p = .067) and PR interval (OR 0.898, p = .079) were found to be independent predictors of these type of arrhythmias in a multivariate analysis. But it is not statistically significant.ConclusionOur results suggest that repolarization parameters may play a role in predicting complete atrioventricular block. Tp‐e/JTc was found to be potential independent risk marker for this setting.

A New Coated Nitinol Occluder for Transcatheter Closure of Ventricular Septal Defects in a Canine Model

Aims. This study evaluated feasibility and safety of implanting the polyester-coated nitinol ventricular septal defect occluder (pcVSDO) in the canine model. Methods and Results. VSD models were successfully established by transseptal ventricular septal puncture via the right jugular vein in 15 out of 18 canines. Two types of VSDOs were implanted, either with pcVSDOs (n = 8) as the new type occluder group or with the commercial ventricular septal defect occluders (VSDOs, n = 7, Shanghai Sharp Memory Alloy Co. Ltd.) as the control group. Sheath size was 10 French (10 Fr) in two groups. Then the general state of the canines was observed after implantation. ECG and TTE were performed, respectively, at 7, 30, 90 days of follow-up. The canines were sacrificed at these time points for pathological and scanning electron microscopy examination. The devices were successfully implanted in all 15 canines and were retrievable and repositionable. There was no thrombus formation on the device or occurrence of complete heart block. The pcVSDO surface implanted at day 7 was already covered with neotissue by gross examination, and it completed endothelialization at day 30, while the commercial VSDO was covered with the neotissue in 30th day and the complete endothelialization in 90th day. Conclusion. The study shows that pcVSDO is feasible and safe to close canine VSD model and has good biocompatibility and shorter time of endothelialization.

Transcatheter closure of the perimembranous ventricular septal defect—preclinical trial of a new amplatzer device

This study assessed the feasibility and efficacy of implanting a new nitinol device for closure of perimembranous ventricular septal defects in a swine model. Perimembranous ventricular septal defect occurs in 80% of patients requiring treatment for congenital heart disease. The Amplatzer perimembranous ventricular septal occluder device (pmVSO2 device, AGA Medical Company, Plymouth MN) is a new transcatheter Nitinol device containing polyester fabric designed to close the perimembranous ventricular septal defect (VSD). The device has 75% reduction in radial force, 45% reduction in clamping force, and increased stability as compared to the previous version. The device was implanted in six swine with naturally occurring perimembranous VSD with immediate, 1, 7, ∼30, and ∼90 day followup by echocardiography, angiography, and final pathological examination. The device was successfully implanted in all animals and was retrievable and repositionable. There was complete occlusion of the VSD in five of six cases without embolization. There was no thrombus formation on the device or occurrence of complete heart block. A single instance of a tiny residual shunt was attributed to capture of tricuspid valve apparatus. The success of this animal study confirms safety and feasibility of the Amplatzer pmVSO2 device. Human trials are planned.

Delayed occurrence of complete heart block after ethanol septal ablation for hypertrophic obstructive cardiomyopathy

Ethanol septal ablation has emerged as a less invasive alternative to surgical myomectomy for treatment of hypertrophic obstructive cardiomyopathy (HOCM). The procedure has very low mortality, but complete heart block (CHB) is a common complication. Prior studies suggested existence of baseline characteristics, ECG features and procedural risk factors, which are highly predictor of CHB requiring permanent pacemaker after ethanol septal ablation. CHB is often preceded by postprocedure conduction abnormalities and generally develops within 48 h after ethanol ablation. We present a unique case of a patient with HOCM who developed a CHB on 8th day postprocedure without preceding conduction abnormalities or other classic risk factors.

Predictors of Complete Heart Block After Transcoronary Ablation of Septal Hypertrophy: Results of a Prospective Electrophysiological Investigation in 172 Patients With Hypertrophic Obstructive Cardiomyopathy

This study analyzed changes in intracardiac conduction during transcoronary ablation of septal hypertrophy (TASH) to identify predictors for pacemaker dependency after TASH. Transcoronary ablation of septal hypertrophy is an accepted therapeutic option in hypertrophic obstructive cardiomyopathy (HOCM). However, atrioventricular conduction disorders, requiring permanent pacemaker implantation, remain a major adverse effect. This study measured changes in intracardiac conduction in 172 consecutive patients during TASH by simultaneously recording electrophysiological parameters and correlated these parameters with the occurrence of complete heart block during continuous electrocardiographic monitoring for 8 days. Intraprocedural complete heart block occurred in 36 patients (20.1%) and was associated with a pre-existing bundle branch block (p = 0.010) or advanced age (p = 0.023). All patients with delayed complete heart block during follow-up (n = 15, 8.7%), occurring 1 to 6 days after TASH, showed lack of retrograde atrioventricular nodal conduction after TASH (p = 0.018). None of the patients with intact retrograde conduction after TASH developed delayed complete heart block. Further risk factors for delayed block were advanced age, intraprocedural complete heart block, and prolonged QRS duration before or after TASH (p < 0.05 for all). Permanent pacemaker implantation was performed in 20 patients. Measurement of intracardiac conduction during TASH improves the safety of the procedure by enabling identification of patients who are at risk of complete heart block after TASH. The duration of prophylactic temporary pacemaker backup should be prolonged up to day 6 after TASH in patients at increased risk (patients with retrograde atrioventricular block and at least 1 additional risk factor).

Acute Predictors of Subacute Complete Heart Block After Alcohol Septal Ablation for Obstructive Hypertrophic Cardiomyopathy

Acute and subacute complete heart block (CHB) are sequelae of alcohol septal ablation (ASA) for obstructive hypertrophic cardiomyopathy. Temporary pacemakers are routinely placed at the time of ASA, but there are no widely accepted guidelines for their management. This study examined acute predictors of subacute CHB in 52 consecutive ASA procedures in 48 patients without preexisting permanent pacemakers. Acute CHB occurred during 32 ASA procedures (62%), with the return of atrioventricular conduction on the day of ASA in all cases. New intraventricular conduction defects (IVCDs) were noted after 32 procedures (62%); in 9 of these, there was new first-degree atrioventricular block as well. CHB recurred subacutely 36 +/- 22 hours after 13 ASA procedures (25%). In 5 of these cases, there was absent or inconsistent ventricular escape rhythm. Subacute CHB did not occur in 9 cases without acute CHB during ASA or new IVCDs after ASA. Acute CHB during ASA, new IVCDs after ASA, and new first-degree atrioventricular block after ASA incrementally increased the risk for subacute CHB. In conclusion, patients with acute CHB during ASA or new IVCDs after ASA are at high risk for developing subacute CHB, sometimes without a reliable escape rhythm; these patients should therefore have temporary pacing support for > or = 48 hours after ASA or the last occurrence of CHB. Patients without acute CHB during ASA or new IVCDs after ASA are at low risk for subacute CHB.

Two-decade-long trends (1975-1997) in the incidence, hospitalization, and long-term death rates associated with complete heart block complicating acute myocardial infarction: A community-wide perspective

Background The purpose of this community-wide study was to describe a >2-decade-long experience (1975-97) in the incidence and death rates associated with complete heart block (CHB) in patients with acute myocardial infarction (AMI). Limited population-based data exist describing recent, and changes with time therein, incidence and case-fatality rates associated with CHB complicating AMI. Methods We conducted an observational study of 9082 metropolitan Worcester, Mass, residents (1990 census = 437,000) hospitalized with validated AMI in all greater Worcester hospitals during 11 1-year periods between 1975 and 1997. Results Overall, CHB developed in 5.0% of patients with AMI. The incidence rates of CHB declined in the periods studied (6.0% in 1975/78 vs 3.1% in 1997). Declines in the occurrence of CHB were noted in patients with anterior or inferior/posterior MI. These trends remained after adjustment for other factors that might affect the risk of CHB. Patients in whom CHB developed experienced significantly higher hospital death rates than patients in whom CHB did not develop (46.8% vs 14.6%). However, improving trends in the hospital survival rate of patients with CHB were observed between 1975/78 (47.4% surviving) and 1997 (61.3% surviving). Patients in whom CHB developed during hospitalization were not at increased risk for dying after hospital discharge. Conclusions Our findings indicate that the incidence of CHB complicating AMI has declined with time. The hospital prognosis of patients in whom CHB developed has improved, but these patients remain at an increased risk of hospital mortality. The long-term prognosis of patients with inferior MI and CHB is similar to that of patients in whom CHB did not develop. Patients with anterior MI and CHB may be at an increased risk of long-term mortality. (Am Heart J 2003;145:500-7.)

Safety of slow pathway ablation in patients with long PR interval: further evidence of fast and slow pathway interaction.

Whether the presence of abnormal PR before selective slow pathway ablation for AV node reentrant tachycardia increased the risk of complete heart block remains controversial. We report our experience in seven patients with prolonged PR intervals undergoing catheter ablation for AV reentry tachycardia. Their mean age was 66 +/- 12 years; four patients were female and three were male. RF ablation was performed using an anatomically guided stepwise approach. In six patients, common type AV node reentry was induced and uncommon type was observed in the remaining patient. In all seven patients, successful selective slow pathway ablation was associated with no occurrence of complete heart block and was followed by shortening of the AH interval in five patients. In all seven patients, successful ablation was achieved at anterior sites (M1 in two patients and M2 in five patients). Despite AH shortening after ablation, the 1:1 AV conduction was prolonged after elimination of the slow pathway, excluding either sympathetic tone activation or parasympathetic denervation. In conclusion, selective slow pathway ablation can be performed safely in the majority of patients with prolonged PR interval before the procedure. Because successful ablation is achieved at anterior sites in most patients, careful selection and monitoring of catheter position is required.

Development of complete heart block in an adult patient with Sjögren's syndrome and anti‐Ro/SS‐A autoantibodies

We describe the occurrence of complete heart block in a patient with Sjögren's syndrome. The patient's serum contained antibodies to both the 60-kd and 52-kd Ro proteins. This case indicates that although the adult atrioventricular node may be relatively resistant to the development of anti-Ro-associated heart block, it can nevertheless be affected.

Tetralogy of Fallot: Intracardiac Repair in 840 Subjects

Since 1967, when the first intracardiac repair was performed in this centre, until 1991, 840 symptomatic subjects with tetralogy of Fallot have undergone corrective surgery. Cardiac catheterization and angiocardiography were carried out in all patients. Cardinal findings on the clinical status of these subjects are outlined. A substantial number of patients (244; 29.0%) were > 15 years of age. Historically, a transannular pericardial gusset has been utilized in 578 (68.8%), and in 423 (93.0%) during the past decade. The incidence of residual interventricular septal defects has been 0.68% and occurrence of complete heart block after surgery 0.4%. Death occurred in 86 patients (10.2%) within 30 days of operation and later in 40 subjects (4.8%). Long-term results have been excellent with good haemodynamic status in > 90% of subjects in the follow-up period. Associated features including absent pulmonary valve, absent left pulmonary artery, and previous palliative shunts did not alter the outcome; however, a raised haematocrit (> 0.65) was associated with an increased mortality rate.

Long-Term Outcome in Patients With Inferior Myocardial Infarction and Complete Atrioventricular Block

Some studies have reported increased short-term mortality and higher incidence of multivessel coronary artery disease in patients with inferior myocardial infarction and complete heart block, but information is lacking on clinical outcome after hospital discharge. Therefore, data were obtained and analyzed in 749 patients who were admitted with inferior myocardial infarction to four different centers and followed up for 1 year. Six hundred fifty-four patients (Group 1) did not have complete heart block and 95 (Group 2) had complete heart block during their hospital stay (incidence rate 12.8%).Compared with Group 1, Group 2 patients were older (66 versus 61 years, p < 0.01), more often had signs of left ventricular failure (p < 0.001) and had higher peak creatine kinase values (1,840 versus 1,322 IU/liter, p < 0.001). The in-hospital mortality rate was higher in Group 2 than in Group 1 (24.2 versus 6.3%, p < 0.001). However, at discharge there was no difference between Group 1 andGroup 2 in clinical characteristics, left ventricular ejection fraction (0.52 ± 0.12 versus 0.52 ± 0.11) or incidence of complex ventricular arrhythmias on ambulatory electrocardiographic monitoring. Furthermore, during the year after hospital discharge, patients in Groups 1 and 2 did not have significantly different mortality rates (6.4 versus 10.1%, p = NS). The incidence rate of reinfarction (4%) was the same in Groups 1 and 2. The incidence of coronary artery bypass surgery was slightly but not significantly higher in Group I compared with Group 2 (11 versus 4%).It is concluded that patients with inferior myocardial infarction and complete heart block have a high in-hospital mortality. However, by multivariate analysis, the occurrence of complete heart block is no longer an independent predictor of poor prognosis after hospital discharge. Patients with complete heart block who survive to leave the hospital have a favorable clinical outcome.

A simplified method to predict occurrence of complete heart block during acute myocardial infarction

A simplified method to predict occurrence of complete heart block during acute myocardial infarction

A simplified method to predict occurrence of complete heart block during acute myocardial infarction

Data were analyzed from 698 patients with proved acute myocardial infarction (AMI) to develop a method to predict the occurrence of complete heart block (CHB). The presence of electrocardiographic abnormalities of atrioventricular or intraventricular conduction during hospitalization was determined for each patient. The electrocardiographs risk factors considered were: first-degree atrioventricular block, Mobitz type I atrioventricular block, Mobitz type II atrioventricuiar block, left anterior hemiblock, left posterior hemiblock, right bundle branch block and left bundle branch block. A CHB risk score was developed that consisted of the sum of each patient's individual risk factors. CHB risk scores of 0, 1, 2 or 3 or more were associated with incidences of CHB of 1.2, 7.8, 25.0 and 36.4%, respectively. When applied to an independent AMI data base, as well as to the summed results of 6 previously reported series that identified predictors of CHB during AMI, a similar incremental risk of CHB as predicted by the risk score method was demonstrated.

Atrioventricular conduction abnormalities in patients undergoing isolated aortic or mitral valve replacement.

Cardiac conduction defects are common in patients with aortic valve disease. Several studies have suggested that the spontaneous occurrence of complete heart block in these patients is related to the extent of calcium deposits in the aortic valve and adjacent structures. No studies have been done to relate the occurrence of complete heart block at the time of valve replacement to predictive factors. We evaluated 102 consecutive patients undergoing isolated aortic valve replacement and 100 patients undergoing isolated mitral valve replacement. Although transient complete heart block was relatively common in each group (17.6% and 13%, respectively), we were not able to identify any factors predictive of its occurrence. There was a very low incidence of late heart block in a follow-up period of over four years. Thus, the capability for temporary pacing is mandatory in patients undergoing valve replacement. However, transient complete AV block during the perioperative period does not predict late recurrence of AV block and, therefore, prophylactic pacemaker or electrode implantation during or following transient block appears unnecessary.

The Risk of Cardiac Complications in Surgical Patients with Bifascicular Block: A Clinical and Electrophysiologic Study in 98 Patients

Ninety-eight patients with ECG evidence of bifascicular block who had undergone general anesthesia and surgery have been followed up. His bundle electrogram was recorded in all patients prior to the surgery. On the basis of electrophysiologic studies, patients were classified in two groups: normal H-V group (47 patients) and prolonged H-V group (51 patients). The prolonged H-V group presented a significantly greater incidence of organic heart disease and cardiac symptoms. Correspondingly, there was a significantly higher incidence of cardiac intra- and postoperative complications in patients with prolonged H-V interval, but none of the patients developed complete heart block. Ventricular fibrillation and not the occurrence of complete heart block, was the cause of sudden cardiac death in three patients who had a prolonged H-V interval and severe organic heart disease. Patients with bifascicular block, undergoing anesthesia and surgery, even in the presence of presumable risk factors, do not require prophylactic pacing. The H-V duration represents a more accurate predictor of major cardiac intra- and postoperative complications than the surface recordings, but only in patients with symptomatic heart disease. These data support the concept that high-risk patients can be identified clinically and thus preoperative determinations of H-V intervals should not be recommended. Ninety-eight patients with ECG evidence of bifascicular block who had undergone general anesthesia and surgery have been followed up. His bundle electrogram was recorded in all patients prior to the surgery. On the basis of electrophysiologic studies, patients were classified in two groups: normal H-V group (47 patients) and prolonged H-V group (51 patients). The prolonged H-V group presented a significantly greater incidence of organic heart disease and cardiac symptoms. Correspondingly, there was a significantly higher incidence of cardiac intra- and postoperative complications in patients with prolonged H-V interval, but none of the patients developed complete heart block. Ventricular fibrillation and not the occurrence of complete heart block, was the cause of sudden cardiac death in three patients who had a prolonged H-V interval and severe organic heart disease. Patients with bifascicular block, undergoing anesthesia and surgery, even in the presence of presumable risk factors, do not require prophylactic pacing. The H-V duration represents a more accurate predictor of major cardiac intra- and postoperative complications than the surface recordings, but only in patients with symptomatic heart disease. These data support the concept that high-risk patients can be identified clinically and thus preoperative determinations of H-V intervals should not be recommended.