Left bundle branch block and coronary artery disease

This study tries the concept that left bundle-branch block (LBBB) connotes coronary artery disease (CAD). The findings indicate that prior studies both supporting of and in contradiction to the premise of a positive correlation have been biased by pre-selection of the patients reviewed. The data indicate, therefore, that LBBB is related to multiple entities. The major categories are CAD and/or hypertension myocardiopathy and aortic valvular disease. In addition, LBBB may develop during the acute phase of myocardial infarction. Its existence as a wholly benign entity has been documented as well. Further, this study adds still another group with LBBB. Six of the nine LBBB patients were female. Five of these, in spite of typical anginal histories, had no arteriographically demonstrable CAD. The absence of disease was surprising and the incidence of women with LBBB was greater than anticipated, thus providing some basis for suggesting that these women may be representative of still another group with LBBB. Further, this study supports the findings of Lewis et al by confirming an association between LBBB and a statistically shorter LCA mainstem (p less than 0.001).     

Prophylactic permanent pacemakers for patients with chronic bundle branch block.

His bundle recordings were obtained in 189 patients with chronic bundle branch block, and the patients were followed for a mean of approximately 20 months. Forty patients underwent prophylactic pacemaker insertion (group II) and 149 did not (group I). There was no significant difference between the two groups at the time of entry into the study with regard to mean age, serum cholesterol or the incidence of smoking, diabetes, hypertension, coronary artery disease or congestive heart failure. The patients in group II had a significantly higher incidence of transient neurologic symptoms (30 of 40,75 per cent, versus 79 of 149, 53 per cent, p < 0.05) and longer mean infranodal conduction time (79 ± 25 versus 61 ± 20 msec, p < 0.001). Eleven patients died before symptom relief could be assessed. More paced patients (group II) had relief of neurologic symptoms compared with the unpaced group (18 of 25, 72 per cent, versus 36 of 73, 49 per cent), but the difference was not quite statistically significant (0.1 <p > 0.05). There was no significant difference between the two groups in the total mortality or the incidence of sudden death. Nineteen of 21 sudden deaths occurred in patients with coronary artery disease and/or congestive heart failure.In conclusion, (1) prophylactic pacemaker insertion in a subset of largely symptomatic patients with chronic bundle branch block and long H-Q time did not protect against sudden death; the incidence of this complication appears to be related to the type and severity of underlying heart disease; (2) presenting neurologic symptoms may be an inadequate guide to assess the need for permanent pacing in bundle branch block.     

The use of temporary transvenous pacing catheters during percutaneous transluminal coronary angioplasty

The use of temporary transvenous pacemakers during percutaneous transluminal coronary angioplasty (PTCA) over a 7(1/2)-month period at our institution was studied retrospectively. During that time, 379 patients underwent PTCA with temporary prophylactic pacemakers in place; 398 patients underwent PTCA without prophylactic pacemakers. We examined factors such as the necessity for emergent pacemaker placement, frequency of pacing during angioplasty, indications for pacing, effectiveness of the type of pacemaker inserted, and complications associated with pacemaker placement. Pacing was indicated in 40 of the 379 patients with prophylactic pacemakers; in only 1 of the 398 patients without prophylactic pacemakers was emergent pacing required for hemodynamic instability. In the patients with prophylactic pacemakers, pacing was initiated during the procedure for 32 patients with transient hemodynamically insignificant bradycardia, 3 patients with sustained bradycardia or heart block, and 5 patients with acute vessel occlusion and associated hypotension or bradycardia, or other episodes of hemodynamic instability. Thus, in only 8 of the 379 patients was pacing instituted for something other than hemodynamically insignificant bradycardia, and in only 5 of the 379 patients was it initiated for hemodynamic instability. The overall incidence of pacing for hemodynamic instability was 6 of 777 (0.8%). The pacing catheters inserted (379 prophylactic and 1 emergent) include #7 Pacewedge (42%), #6 bipolar (29%), #7 Myler (18%), and #7 Zucker (11%). Pacing thresholds were tested in 300 patients. The Pacewedge balloon-tipped pacing catheters had a significantly higher (p < 0.001) pacing threshold for right ventricular capture than the other (non-balloon) pacing catheters used. Two cases of sustained ventricular dysrhythmia were attributed to placement of stiff pacing catheters. No other pacemaker-related complications occurred. From these data we conclude that although there are few complications associated with the prophylactic placement of pacing catheters for PTCA, the need for cardiac pacing for hemodynamic instability during PTCA is low.     

Complete bundle branch block during exercise test. Clinical and coronary angiographic data

Thirty-two complete bundle branch blocks were observed during 16,500 exercise stress tests between 1973 and 1988: there were 7 right bundle branch blocks and 25 left bundle branch blocks. Exercise stress testing was indicated in 15 cases for stable angina, in 15 cases for different functional disturbances and in 2 cases as a systematic investigation. All patients underwent coronary angiography and selective left ventriculography. Right bundle branch block occurring at a heart rate of 105 +/- 25/mn were associated with typical anginal pain at the time of apparition in 5 patients. Coronary angiography showed triple vessel disease in 3 cases, double vessel disease in 2 cases and an isolated proximal lesion of the left anterior descending artery in 2 cases. Left bundle branch block occurring at a heart rate of 125 +/- 12/mn was associated with normal coronary angiography in 7 cases. Eighteen patients had pathological coronary angiogrammes with severe lesions of the left anterior descending artery. Two women suffered from chest pain when the block developed and coronary angiography was normal in one of them. During follow-up (average 62 months), 16 coronary events were observed including 2 infarcts, and 6 patients developed cardiac failure. In conclusion, complete right bundle branch block appearing during exercise stress testing was constantly associated with atherosclerotic coronary artery disease. The predictive value of complete left bundle branch block on effort was 72%. Complete left bundle branch block occurring at heart rates of less than 120/mn was frequently associated with a proximal stenosis of the left anterior descending artery.     

Unmasking of left bundle branch potential in left bundle branch block during physiological pacing

Journal of Interventional Cardiac Electrophysiology -     

完全性左束支阻滞和右束支阻滞心电图结果分析

目的 了解完全性左束支阻滞和右束支阻滞不同性别、不同年龄的发生率情况.方法 分析108 610例常规心电图检测结果,分别统计完全性左束支阻滞和右束支阻滞不同性别、不同年龄的发生率情况.结果 108 610例门诊及住院患者资料,完全性左束支阻滞19例,占0.18％;右束支阻滞3 794例,占3.49％;完全性左束支阻滞发生率在不同性别之间差异无统计学意义（Х^2=1.707,P=0.191）,不同年龄之间比较差异有统计学意义（Х^2=209.874,P＜0.05）;右束支阻滞发生率在不同性别之间、不同年龄之间比较,差异均有统计学意义（Х^2=986.046,P＜0.05;Х^2=1 483.286,P＜0.05）.结论 60岁以上老年人的完全性左束支阻滞和右束支阻滞发生率较高,应定期进行常规心电图检查,及时发现异常情况并进行相应的处理.     

Hemodynamic studies during intermittent left bundle branch block

A patient with intermittent left bundle branch block and moderate aortic insufficiency, presumably due to rheumatic heart disease, is presented.

At retrograde left heart catheterization, left bundle branch block recurred repeatedly and was always converted to normal conduction and left ventricular hypertrophy by administration of oxygen. Electrocardiograms, intracardiac pressures and indicator-dilution curves for cardiac output were recorded with both types of conduction.

The following hemodynamic alterations consistently accompanied intermittent left bundle branch block:

1. 1. There was a significant fall in the systolic pressures in the left ventricle, central aorta and radial artery, a decreased stroke volume and an increased heart rate. These findings suggest that the force and intensity of left ventricular contraction and, consequently, systolic ejection are significantly decreased with the onset of delayed conduction.

2. 2. A prolonged phase of isometric contraction was the most important alteration in the time relationships of the hemodynamic events of ventricular contraction. This resulted in delay in onset and termination of systolic ejection, with a normal duration of the ejection phase. Isometric relaxation was also prolonged proportionately, but duration of diastole shortened as the cardiac rate increased. Prolonged isometric contraction of the left ventricle is probably responsible for the delayed closure of the aortic valve and paradoxic or fixed splitting of the second heart sound very often seen with left bundle branch block.

     

Alternating bundle branch block

Mechanisms postulated for alternating bundle branch block are incomplete-and cycle-length-dependent-block in both the right and left bundle branches. A patient with severe longstanding cardiac conduction disease who developed alternating bundle branch block during treatment for advanced ischemic heart disease and malignant ventricular arrhythmia is presented. In this patient alternation was induced by atrial premature beats as well as spontaneous and pacemaker induced premature ventricular beats. Right bundle branch block which followed a premature atrial beat resulted from the longer refractory period of the right bundle. The maintenance of right bundle branch block at long cycle lengths was presumed to be due to continuous retrograde reentry. This was terminated when a pause following a premature beat allowed functional recovery of the right bundle branch. This patient died suddenly at home with a functioning pacemaker, demonstrating the high risk of death from ventricular dysrhythmia in the post myocardial infarction patient with a new conduction defect.     

Exercise-induced bundle branch block

Exercise-induced bundle branch block (BBB) is poorly understood. An investigation was made of its clinical, electrocardiographic, coronary angiographic, and myocardial scintigraphic characteristics, with follow-up data in 16 patients, aged 59 ±9 (mean ± standard deviation) years, 11 who had left BBB and 5 who had right BBB. Fourteen had a preexisting baseline electrocardiographic abnormality; 11 had either incomplete BBB or nonspecific intraventricular conduction delay. Heart rates at onset of exercise BBB varied from 70 to 166 beats/min and in 9 patients the rates at BBB onset and offset appeared to be related, occurring within 8 beats/min of each other. Coronary artery disease (CAD) was diagnosed in 10 patients, cardiomyopathy in 2, and probable coronary spasm in 2. One patient had ventricular arrhythmias of uncertain origin, and 1 appeared to have no cardiac disease. Three patients had reversible thallium perfusion defects consistent with ischemia concurrent with developing BBB. The 3 patients in whom exercise BBB persisted all had CAD. Over a mean of 28 months of follow-up, only 1 patient had a morbid cardiac event—nonfatal myocardial infarction—and 2 died from noncardiac causes. Thus, exercise BBB primarily occurs in the context of cardiac disease, most commonly CAD, and concurrent ischemia may be demonstrable; the presence of “rate relation” does not militate against CAD.     

Quantification of ST-segment changes during coronary angioplasty in patients with left bundle branch block

Electrocardiographic manifestations of ischemia are difficult to interpret in the presence of left bundle branch block (LBBB). Recently developed techniques allow continuous computerized digital analysis of ST segments that can be zeroed to the patient's own baseline electrocardiogram even if that baseline is abnormal conduction. With use of this technology, ST-segment changes during balloon coronary occlusion were compared in 10 patients with LBBB versus an age-, sex-, and coronary anatomy-matched population of 20 control subjects with normal baseline conduction. ST-segment deviation of greater than or equal to 1 mm from baseline was present in 80% of patients with LBBB and in 75% of control patients (difference not significant). There was no significant difference between patients with LBBB versus control patients in maximal ST-segment deviation (2.6 +/- 1.7 vs 2.0 +/- 1.0 mm) or in ST-segment deviation measured after 60 seconds of occlusion (2.4 +/- 1.3 vs 1.8 +/- 1.1 mm). ST-segment deviation reached 1 mm more quickly in patients with LBBB (33 +/- 11 seconds) than in control subjects (60 +/- 36 seconds) (p = 0.003). It is concluded that ST-segment analysis is feasible in patients with LBBB using digital self-referenced ST analysis and may provide important clinical information regarding the presence of myocardial ischemia.