Etiology of right bundle branch block pattern following surgical repair of atrioventricular cushion defects

Electrocardiograms and surgical data from 12 patients with complete atrioventricular canal defects and 24 patients with ostium primum defects were evaluated before and after open heart surgery in order to document the incidence of postoperative right bundle branch block. The use and precise location of septal sutures utilized for repair were specifically noted in order to assess their possible role in the genesis of the postoperative right bundle branch block pattern. Septal sutures were placed in all patients with atrioventricular canal defects, and ten (83 percent) of these 12 patients developed right bundle branch block. Seven (29 percent) of the 24 patients with ostium primum defects developed a postoperative right bundle branch block, and in all seven patients, septal sutures were utilized. None of the patients with an ostium primum defect without septal sutures developed a right bundle branch block, and none of the patients in this series developed complete heart block.     

Fascicular conduction disturbances and ischemic heart disease: adverse prognosis despite coronary revascularization

In patients with ischemic heart disease, fascicular conduction disturbances are associated with increased mortality. This study reveals that increased mortality also exists for certain types of fascicular conduction disturbances after myocardial revascularization. In 227 consecutive patients undergoing bypass surgery, 24 had preoperative and an additional 52 developed at surgery a fascicular conduction disturbance. At 66 +/- 14 months of follow-up, 6 (4%) of 148 control patients without pre- or postoperative fascicular conduction disturbances had died from cardiac causes. Although right bundle branch block and left hemifascicular block were the most common form of fascicular conduction disturbance, only 1 of 55 of these patients died (p = NS). Mortality rates were much higher for patients with left bundle branch block or an intraventricular conduction defect; 8 (38%) of 21 died from cardiac causes (p less than 0.05). A high risk subgroup was identified by comparing 14 consecutive patients with left bundle branch block or an intraventricular conduction defect who survived more than 1 year postoperatively with 21 consecutive patients with these same conduction defects who died within 1 year of surgery. The following variables were significantly (p less than 0.05) different (survivors versus nonsurvivors): age (58 +/- 7 versus 65 +/- 9 years); class IV angina (2 of 14 versus 16 of 21), prior myocardial infarction (9 of 14 versus 21 of 21), left ventricular ejection fraction (53 +/- 18 versus 41 +/- 15%), three vessel disease (9 of 14 versus 20 of 21) and left ventricular aneurysm (2 of 14 versus 13 of 21).(ABSTRACT TRUNCATED AT 250 WORDS)     

Histologic observations of the cardiac conduction system in a patient with postoperative bilateral bundle branch block

It has been suggested that the postoperative development of a right bundle branch block pattern is due to injury of peripheral rather than proximal parts of the right bundle branch and does not affect the prognosis for the later development of complete heart block. However, the occurrence of complete heart block in a patient with postoperative right bundle branch block who later has left bundle branch block has not previously been documented. The entire specialized cardiac conduction system of a patient who had two operations for repair of double outlet right ventricle and multiple ventricular septal defects was serially sectioned. In the first operation, which resulted in a right branch block pattern, a subaortic ventricular septal defect was repaired through a right ventriculotomy. In the second operation complete heart block occurred after multiple muscular ventricular septal defects were repaired with a patch inserted through a left ventriculotomy. Examination of the conduction system showed that the right bundle branch was completely interrupted by the patch used to repair the subaortic ventricular septal defect and the left bundle branch was completely severed by the patch used to repair the muscular ventricular septal defects.     

Fascicular conduction distrubances after coronary bypass surgery.

Two hundred patients underogoing coronary bypass graft surgery were studied to determine the frequency and significance fo new fascicular conduction distrubances. The follow-up period ranged from 13 to 39 months. New disturbances developed in 39 patients (20 percent). Isolated right bundle branch block (6 percent) and left anterior hemiblock (6 percent) were the most common disturbances. Righ bundle branch block was usually transient and was not associated with further complications in the follow-up period. However, patients with either transient or persistent left bundle branch block or left anterior hemiblock, or both, had (1) increased later mortality compared with patients without new fascicular conduction disturbances (5 of 26 versus 11 of 161; P less than 0.02), and (2) increased late myocardial infarction (2 of 26 versus 2 of 161; P less than 0.05). New left fascicular conduction disturbances after coronary surgery identified a subset of patients with more extensive ischemic heart disease, suggesting that these patients require close follow-up care.     

Hidden intracardiac conduction disturbances and their spontaneous course in patients with progressive muscular dystrophy

In patients with progressive muscular dystrophy (PMD) invasive electrophysiologic studies can detect hidden intracardiac conduction disturbances. The aim of this study was a long-term follow-up of these patients. Twelve consecutive patients (9 m, 3 f, age 28 +/- 4 yrs) without cardiac symptoms and with normal echocardiographic findings were included in the study. They suffered from different stages of PMD type Erb (n = 4), Becker-Kiener (n = 4), Duchenne (n = 2) and Landouzy-Déjerine (n = 2). At the beginning of the study all patients underwent an invasive electrophysiologic study (EPS). The follow-up of 5.5 yrs included regular clinical visits, ECGs, and Holter recordings (every 3 months) as well as an echocardiography every 6 months. In 4 patients the EPS revealed a hidden interatrial conduction disturbance (AHRS-ACS 120 +/- 18 ms), and in 10 pts an infrahisian conduction disturbance was found (HV max. 156 +/- 4 ms). Conduction defects were seen independently from the type of PMD and the stage of the disease. During the follow-up the initially hidden interatrial conduction disturbance became evident in the surface ECG in 2 of 4 pts. One of them developed paroxysmal atrial fibrillation. Five of 10 pts with an initially hidden infrahisian conduction disturbance developed an AV block grade I-III and in one case additionally a bundle branch block. Four of these pts--whose PMD showed progression or who developed congestive cardiomyopathy--needed pacemaker implantation because of a first-degree AV block + bifascicular bundle branch block (n = 1), a Mobitz II second-degree AV block (n = 1) or a third-degree AV block (n = 2). None of the pts with normal findings at the EPS showed abnormal p-waves, an AV block, or an intraventricular conduction disturbance during the follow-up. We conclude that intracardiac conduction disturbances, especially infrahisian defects including high-degree AV blocks, are a common finding in pts with PMD. Therefore a regular cardiological screening including an ECG and a Holter recording is reasonable in these patients.     

Transient atrioventricular block after open-heart surgery for congenital heart disease

The records of 22 patients with transient atrioventricular (AV) block after open-heart surgery for congenital heart disease from 1972 to 1978 were reviewed to determine the natural history of this entity. Preoperatively, no patient had AV block; 3 had right bundle branch block (BBB), 1 had left BBB and 5 had nonspecific intraventricular conduction delay. Complete AV block developed in 20 patients and Mobitz II AV block in 2. Transient AV block occurred intraoperatively in 14 patients and within 48 hours postoperatively in 8; AV block persisted for greater than or equal to 48 hours postoperatively in all patients, for a mean of 7.3 days (range 2 to 28). During a follow-up of 5.5 years (range 2.5 to 10), late AV block developed in 2 patients. None of the 18 patients whose escape QRS complex morphology during AV block was similar to the final QRS complex during normal sinus rhythm or atrial fibrillation with AV conduction had late AV block, whereas 2 of the 4 in whom it differed did (p less than 0.01). There was no difference in the escape rate between the 2 groups. Thus, late development of high-grade AV block is infrequent among patients with transient postoperative AV block. An escape QRS complex during postoperative AV block that differs from the QRS complex seen on recovery of normal sinus rhythm or atrial fibrillation with anterograde conduction may identify those at high risk of late AV block.     

Bradyarrhythmias, abnormalities of conduction, and indications for pacing in acute myocardial infarction

Bradyarrhythmias and conduction disturbances are not infrequently observed in association with acute MI. The sinus node artery is supplied by the right coronary circulation only slightly more often than the left. As a result of concomitant vagotonia, however, sinus node dysfunction is more common with inferior infarction. This influence, as well as a predominantly right-sided circulation, also makes AV nodal block more frequent with such infarctions. Bradyarrhythmias due to sinus or AV nodal dysfunction often require only observation. If symptomatic, they are usually responsive to vagolytic or chronotropic drugs, but may necessitate pacemaker therapy often only on a temporary basis. The distal conduction system including the bundle branches is supplied mainly, but not exclusively, by the left anterior descending artery. Thus, acute bundle branch block is often associated with anterior MI. The indications for both temporary and permanent prophylactic pacing in this situation remain controversial. Several authors have made recommendations based on risk stratification. We would temporarily pace patients with anterior or indeterminate infarctions and new right or left bundle branch block, and probably those with bilateral bundle branch block of indeterminate age. All patients with new bilateral or alternating bundle branch block should be paced, regardless of infarct site. Permanent prophylactic pacing would appear indicated in patients exhibiting alternating bundle branch block or perhaps new right bundle branch block and left posterior hemiblock. In contrast to this group, the treatment of patients who develop sudden complete heart block, whether transient or permanent, is clear-cut. These patients require continuous (temporary followed without interruption by permanent) pacemaker therapy (Table 3).     

Predictors of complete heart block after alcohol septal ablation for hypertrophic cardiomyopathy and the timing of pacemaker implantation

Catheter-based alcohol septal ablation has recently been introduced for the treatment of left ventricular outflow tract obstruction in hypertrophic obstructive cardiomyopathy. It is associated with various conduction disturbances and may lead to transient or persistent complete heart block (CHB). Electrocardiographic (ECG) changes and predictors of developing CHB and the timing of permanent pacemaker implantation have been variable among the different studies. Among 50 patients studied, we found that a new right bundle branch pattern was the most common new ECG change after septal ablation and that baseline left bundle branch block was strongly associated with the development of CHB (P = 0.004); 9 patients (18%) required permanent pacemaker implantation of whom 7 (78%) remained pacemaker dependent at 14 days with no delayed recovery of atrioventricular conduction. This favors an early pacemaker implantation strategy.     

The incidence and mortality of intraventricular conduction defects in acute myocardial infarction

The incidence of intraventricular conduction defects during sinus mechanism was 24 percent in 212 consecutive cases of acute myocardial infarction observed in a coronary care unit. Patients with intraventricular conduction defects had a higher mean age than that for the entire series (P < 0.01), and death occurred at a younger age than in patients without such defects (P < 0.1). The most common isolated defect was left anterior hemiblock (incidence of 9.4 percent). The next most common conduction defect was incomplete bilateral bundle branch block (incidence 7.5 percent); more than half of these patients had right bundle branch block with left anterior hemiblock. Far less frequent were isolated complete right bundle branch block and complete left bundle branch block. Left posterior hemiblock was rare and was not seen in patients without other intraventricular conduction defects either transient or permanent. The hospital mortality rate of the entire series was 21.2 percent. The mortality rate among patients with intraventricular conduction defects was 47 percent which is significantly different from that for the entire series (P < 0.01) and from a series matched by sex and age (P < 0.01). The most innocuous intraventricular conduction defect was left anterior hemiblock (in-hospital mortality rate 25 percent). This was statistically not different from the mortality rate in the total series. Higher mortality rates were associated with other conduction defects which produced QRS prolongation and bifascicular block.     

Ventricular arrhythmias after correction of ventricular septal defects: importance of surgical approach

To compare the prevalence of conduction disturbances and ventricular arrhythmias in cases of postoperative ventricular septal defect, 100 patients (50 with repair by right atriotomy, group 1; and 50 with repair by right ventriculotomy, group 2) underwent complete evaluation including an electrocardiogram (ECG) and 24 h ambulatory ECG monitoring. The two groups were comparable except for a shorter follow-up duration (7 +/- 3 versus 12.4 +/- 7 years) and a younger age at evaluation (12.4 +/- 5 versus 16.9 +/- 7 years) in group 1. Complete right bundle branch block was less frequent in group 1 than in group 2 (20% versus 50%, p less than 0.05) but three of the four patients with complete atrioventricular (AV) block detected on ambulatory monitoring were in group 1. Six patients had significant supraventricular arrhythmias, all well tolerated. Ambulatory monitoring revealed significant ventricular arrhythmias (modified Lown grade 2 or higher) in 39 patients, with a lower prevalence in group 1 (30% versus 48%, p = 0.05). No correlation was found between prevalence of ventricular arrhythmias and right ventricular systolic pressure, cardiopulmonary bypass duration, presence of a synthetic patch, previous pulmonary artery banding, presence of complete right bundle branch block and cardiomegaly on chest X-ray film. Prevalence of ventricular arrhythmias increased with follow-up duration, age at evaluation and age at surgery. These were always well tolerated and did not warrant treatment. Thus, right atriotomy reduces the prevalence of right bundle branch block but does not prevent late AV block. Ventricular arrhythmias are frequent after surgical closure of ventricular septal defect whatever the surgical approach and their prevalence is not statistically different from that in postoperative tetralogy of Fallot.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cardiac Arrhythmias in Chagas'Heart Disease

Chagas’ Heart Disease. Chagas’ disease is a chronic parasitosis affecting most LatinAmerican countries, Its most important clinical manifestation is a late developing chronicmyocarditis and, much less frequently, an early acute myocarditis, Chagasic myocardial damage is microfocal and disseminated throughout the heart, In most cases, the coexistence ofareas of myocytic degeneration, inflammatory infiltration, and fibrosis suggests a permanentevolving process. Commonly, chronic chagasic myocarditis resemhies a dilated cardiomyopa–thy, with characteristic ECG abnormalities (atrial and ventricular extrasystoles, intraventricular and/or AV conduction disturbances, and primary ST-T wave changes), Since myocardialdamage is scattered throughout the heart, the ECG abnormalities (arrhythmias, conductiondisturbances, and repolarization changes) are also representative of the widespread cardiacinvolvement. Thus, sick sinus syndrome, atrial extrasystoles, intraatrial conduction disturbances, and atrial fibrillation or flutter are common findings in different stages of the disease, At the ventricular level, both conduction disturbances and arrhythmias are conspicuousexpressions of the myocardial damage. Right bundle branch block alone or in combinationwith left anterior hemiblock are the most common conduction defects, Further compromise ofthe conduction system can lead to different degrees of AV block, Chagas’ disease is the maincause of bundle branch block and AV block in endemic areas, In advanced cases of Chagas'heart disease, ventricular premature contractions are extremely frequent, multiforM. andrepetitive (couplets and runs of ventricular tachycardia), and show R on T phenomenon, Thesearrhythmias are usually aggravated by increased sympathetic tone, implying an enbanced riskof cardiac sudden death among chagasic patients, which is sometimes the first manifestation ofthe illness, Chronic chagasic myocarditis is the leading cause of cardiovascular death, mostly asa consequence of heart failure and sudden death, in areas where the disease is endemic.     

Severe postoperative heart blocks appearing late. 16 cases

Sixteen patients, aged 4 to 42 years, operated for congenital heart disease, presented, months or years after surgery, complete atrioventricular (11 cases) or sinoatrial block (5 cases). Six patients had transient complete atrioventricular block in the immediate postoperative period, the maximum duration of which was less than 30 days. The late postoperative period was defined as at least 6 months after surgery. The period between surgery and the implantation of a pacemaker varied from 9 months to 19 years, average 6,3 years. Analysis of long term electrocardiographic studies distinguished three types of progression: --group I: alternation of sinus rhythm and conduction defect until definitive block, sometimes presenting with syncope; --group II: sudden, severe conduction defect after a long period of sinus rhythm; --group III: progressive lengthening of the PR interval. Seven patients developed syncope; 4 had dizziness, 2 were short of breath; only 3 were asymptomatic. All underwent permanent pacing. The incidence of late conduction defects appears to be 1 to 2% of operated patients. The causes include progressive fibrosis, slow sclerosis extending over conduction pathways which are congenitally fragile. Most late blocks are of an advanced degree. Some may be responsible for unexplained sudden death. It is therefore desirable to avoid this complication by the judicious and considered implantation of a cardiac pacemaker. Some authors mention the following factors in deciding on the indications for pacing: --complete, transient atrioventricular block during the operation or the immediate postoperative period; --ECG appearances of right bundle branch block and left anterior hemiblock, or trifascicular block; --His bundle studies.(ABSTRACT TRUNCATED AT 250 WORDS)     

Incidence and prognostic significance of intraventricular conduction abnormalities after coronary bypass surgery

To determine the incidence and prognostic significance of new postoperative conduction disturbances, 2,000 consecutive patients who underwent primary elective coronary bypass surgery were evaluated. One hundred eleven (5.5%) of the 2,000 patients developed a new intraventricular conduction defect that persisted to hospital discharge. Right bundle branch block occurred in 86 (85%), left bundle branch block in 5 (4%) and nonspecific intraventricular conduction defect in 9 (11%). One hundred of these 111 patients were successfully matched with others in the study population who had maintained normal intraventricular conduction during the operative period. Patients were matched on the basis of age, gender, absence of preoperative conduction disturbances, left ventricular function and bypass grafts to the same vessels. Follow-up of the two groups for a period of 1 to 76 months (mean 60 months) failed to show any difference in survival or cardiac events such as myocardial infarction, repeat coronary bypass surgery, coronary angioplasty and permanent pacemaker implantation. The appearance of right or left bundle branch block or a nonspecific intraventricular conduction defect after coronary bypass surgery does not appear to have an unfavorable impact on the long-term prognosis of these patients.     

Correction of tetrad of fallot with reduced incidence of right bundle branch block

In 20 patients who underwent a modified surgical repair of tetrad of Fallot complete right bundle branch block developed in only 8 (40 percent). Standard and intraoperative conduction studies indicated that in these patients the right bundle branch block was due to injury of the right bundle branch near the ventricular septal defect (proximal right bundle branch block). The modified operative technique is aimed at minimizing the injury to the right ventricle and it includes a significantly shorter than usual ventriculotomy incision and avoidance of the septal (moderator) band during infundibulectomy. Intra- and postoperative hemodynamic studies of these patients revealed that relief of the right ventricular outflow obstruction was optimal.     

Alcohol septal ablation versus surgical septal myectomy: comparison of effects on atrioventricular conduction tissue

OBJECTIVES: This study was designed to evaluate the effect of septal reduction therapies on the conduction system for patients with hypertrophic cardiomyopathy (HCM). BACKGROUND: Heart block is a potential complication of both catheter-based and surgical procedures to relieve left ventricular outflow tract obstruction in HCM, but it is important to understand the different effects of these treatments on the conduction system. METHODS: The electrocardiograms and postoperative course of patients who underwent percutaneous alcohol septal ablation or surgical myectomy at Mayo Clinic between 1999 and 2003 were reviewed. RESULTS: For the 58 patients who underwent alcohol septal ablation, 21 (36%) developed right bundle branch block. Six patients (12%) developed complete heart block requiring permanent pacing, three of whom had left bundle branch block before the procedure. Among the 117 patients who underwent surgical septal myectomy, 47 (40%) developed left bundle branch block. Four patients (3%) developed heart block requiring permanent pacing after the procedure, three of whom had right bundle branch block preoperatively. CONCLUSIONS: Percutaneous septal ablation selectively produces transmural infarction of the basal mid-septum and adjacent right bundle tissue, whereas surgical myectomy affects the endocardial portion of the basal anterior septum and adjacent left bundle tissue. These observations may help identify patients at risk for complete heart block after septal reduction procedures for HCM.     

Herzrhythmusst?rungen bei Erwachsenen mit angeborenen Herzfehlern

The occurrence of arrhythmia represents the most important comorbidity in patients with congenital heart disease (CHD). Arrhythmia mechanisms vary according to the underlying anatomic defect and method of surgical repair. The incidence of arrhythmia is highest in patients with moderate and severe CHD. The most common arrhythmia mechanism in CHD patients involves a macroreentry circuit within the atria and is referred to as intra-atrial reentrant tachycardia (IART). Usually, IART, or sinus node dysfunction appear many years after an atriotomy or other surgical manipulation of the right atrium. Atrial fibrillation is not common in CHD. Patients at greatest risk for developing ventricular tachycardia appear to be those who have undergone ventriculotomy or patching of a ventricular septal defect, but it also occurs in patients with left ventricular hypertrophy or reduced ventricular function. Disorders of atrioventricular (AV) conduction can arise in patients with congenitally corrected transposition of the great arteries (ccTGA) or AV canal defects. Surgically induced heart block may occur after closure of ventricular septal defects, surgery for left-heart outflow obstruction, or AV valve replacement.     

Ischemia-associated intraventricular conduction disturbances during exercise testing as a predictor of proximal left anterior descending coronary artery disease

To determine the incidence and significance of transient intraventricular conduction abnormalities occurring in association with myocardial ischemia during exercise testing, the recordings of 2,200 consecutive exercise tests were reviewed. Ten patients (0.45%) were identified as having both ischemia and intraventricular conduction abnormalities that developed transiently during the exercise test. In all 10 patients both typical angina and electrocardiographic evidence of ischemia developed during exercise. Among the 10 patients, left anterior hemiblock developed in 4, left posterior hemiblock in 2, right bundle branch block (RBBB) in 2, RBBB with left axis deviation in 1, and left anterior hemiblock progressing to complete left bundle branch block (LBBB) in 1. All 10 patients had cardiac catheterization showing significant obstruction of the left anterior descending (LAD) coronary artery at or before the origin of the first septal branch. Eight patients were treated surgically and 2 medically, all with relief of ischemic symptoms. Nine of the 10 had repeat exercise stress testing without angina or electrocardiographic evidence of ischemia and without recurrence of the transient intraventricular conduction disturbance.It is concluded that the development of transient intraventricular conduction abnormalities associated with myocardial ischemia during exercise testing is an uncommon occurrence (0.45%). When such conduction disturbances do develop, the existence of significant disease in the proximal portion of the LAD coronary artery is strongly suggested. With control of myocardial ischemia, the transient conduction disturbances during exercise are ameliorated.     

Prognosis for patients with congenital heart disease and postoperative intraventricular conduction defects.

Intraventricular conduction defects are common following repair of various forms of congenital heart disease. Such defects may affect adversely the long-term prognosis of patients in whom cardiac hemodynamics were adequately restored. Review of previously published studies suggests that the site of the conduction defect may be the reason for the different prognoses reported for patients from different institutions. The so-called "trifascicular block" pattern which sometimes occurs following open heart surgery is probably due to a more extensive lesion to the branching and penetrating parts of the His bundle rather than additional injury to the posterior left bundle branch fibers. Transient complete heart block in the immediate postoperative period seems to be a predictor for late development of complete heart block or sudden death at least as powerful as right bundle branch block and left anterior hemiblock.     

The Amplatzer Membranous VSD Occluder and the vulnerability of the atrioventricular conduction system

Transcatheter closure of ventricular septal defects with the Amplatzer Membranous VSD Occluder has yielded promising initial results, but disturbances of conduction, including complete heart block, have been reported. We report our experience with the Amplatzer occluder in 35 patients with a median age 4.5 years, the defects being sized angiographically at 4.4 plus or minus 1.1 millimetres, with a range from 3 to 8 millimetres, and the size of the occluder varying from 4 to 12 millimetres. Over a median follow-up of 2.5 years, the rate of complete closure was 87% and 91%, at 1 and 2 years respectively, while 2 patients required surgical closure of the defect subsequent to the insertion of the device. Persistent regurgitation across the tricuspid valve related to the occluder was observed in 3 patients, and in 6 patients across the aortic valve. Abnormalities of conduction related to the procedure were noted in 7 patients, one-fifth of the cohort. The disturbances were transient in 1 patient, but permanent in 6, in one of the latter progressing after 6 months from left bundle branch block to intermittent Mobitz II second-degree atrioventricular block in association with expansion of the occluder. We conclude that transcatheter closure of perimembranous ventricular septal defects with the Amplatzer occluder is effective with limited complications, but the incidence of immediate and progressive disturbances of conduction related to the proximity of conduction tissues to the rims of the occluder stress the importance of larger and longer studies to assess the safety of this procedure.