Bundle-branch block and in-hospital mortality in acute myocardial infarction. National Registry of Myocardial Infarction 2 Investigators

BACKGROUND

Left bundle-branch block (BBB) is considered an important predictor of poor outcome in patients with acute myocardial infarction, but the consequences of right BBB are not well understood.

OBJECTIVES

To 1) estimate the prevalence of left and right BBB in patients with myocardial infarction; 2) compare the clinical characteristics of and treatments received by patients with left, right, or no BBB; and 3) determine the independent association of left BBB and right BBB with in-hospital death.

DESIGN

Retrospective cohort study.

SETTING

Multicenter registry of 1571 U.S. hospitals.

PATIENTS

297,832 patients with acute myocardial infarction who had left, right, or no BBB on initial electrocardiography.

MEASUREMENTS

Presence and type of BBB, clinical characteristics of patients, therapies given, and in-hospital death.

RESULTS

Patients with left BBB (n = 19,967; 6.7%) or right BBB (n = 18,354; 6.2%) were older and had more comorbid illness and congestive heart failure than patients with no BBB. Among patients for whom thrombolytic therapy was clearly indicated, fewer patients with left or right BBB (16.6% and 32.0%, respectively) than patients with no BBB (66.5%) received this therapy (P < 0.001). Fewer patients with left or right BBB (60.6% and 67.3%, respectively) than patients with no BBB (75.6%) received aspirin within the first 24 hours (P < 0.001), and fewer patients with left or right BBB (23.9% and 31.8%, respectively) than patients with no BBB (40.4%) received beta-blockers within the first 24 hours (P < 0.001). Unadjusted in-hospital mortality rates were almost twice as high for patients with left or right BBB (22.6% and 23.0%, respectively) as for patients with no BBB (13.1%) (P < 0.001). Compared with no BBB and no ST-segment elevation, left BBB was associated with a 34% increase (odds ratio, 1.34 [95% CI, 1.28 to 1.39]) and right BBB was associated with a 64% increase (odds ratio, 1.64 [CI, 1.57 to 1.71]) in the risk for in-hospital death, after adjustment for potential confounders.

CONCLUSIONS

In patients with acute myocardial infarction, prevalences of right and left BBB are similar. Patients with BBB have more comorbid conditions, are less likely to receive therapy, and have an increased risk for in-hospital death compared with patients with no BBB. Compared with left BBB, right BBB seems to be a stronger independent predictor of in-hospital death.

Predictors of in-hospital bundle branch block reversion after presenting with acute myocardial infarction and bundle branch block. GUSTO-I Investigators. Global Utilization of Streptokinase and t-PA for Occluded Coronary Arteries

Patients with acute myocardial infarction and bundle branch block have a higher mortality rate and more in-hospital complications than patients with normal intraventricular conduction. Patients whose conduction defects revert have an improved prognosis (with outcomes similar to patients who never develop bundle branch block); thus, we analyzed potential predictors of bundle branch block reversion.

Frequency and prognostic implications of conduction defects in acute myocardial infarction since the introduction of thrombolytic therapy

OBJECTIVE

To document the frequency of conduction defects and their influence on prognosis in a large series of patients with acute myocardial infarction who underwent coronary care during a period when thrombolytic therapy was in common usage.

BACKGROUND

Conduction defects have been associated with an adverse prognosis following acute myocardial infarction, but there are few data on the incidence and outcome of conduction defects since the introduction of thrombolytic therapy.

PATIENTS AND METHODS

The study group comprised 1225 consecutive patients with acute myocardial infarction treated in the coronary care unit from 1 January 1988 to 31 December 1994. Conduction defects were recorded prospectively and were classified as follows: complete atrioventricular node block associated with narrow complex escape rhythms; left or right bundle branch block; bifascicular block; complete heart block involving both bundle branches.

RESULTS

Electrocardiographic data were available in 1220 patients. Complete atrioventricular node block occurred in 65 (5.3%), left and right bundle branch block in 29 (2.4%) and 44 (3.6%) bifascicular block in 36 (2.9%) and complete heart block involving both bundle branches in 20 (1.6%). The more advanced degrees of block in the bundle branches occurred more commonly in patients with diabetes, previous infarction. Q-wave infarction, anterior infarction and left ventricular failure. Survival analysis showed an increased short- and long-term cardiac mortality in patients with conduction defects, prognosis worsening as the severity of the conduction defect increased.

CONCLUSION

Conduction defects complicated acute myocardial infarction in 16% of cases and had a graded impact on the short- and long-term prognosis, patients with advanced bundle branch involvement faring worst. The data showed a small decline in the rate of severe conduction defects compared with previous studies, possibly reflecting the beneficial effects of thrombolytic therapy on infarct size.

Prognostic value of myocardial perfusion imaging with exercise and/or dipyridamole hyperemia in patients with preexisting left bundle branch block

The detection of myocardial ischemia in patients with preexisting left bundle branch block (LBBB) remains problematic. Pharmacologic hyperemia with dipyridamole is now used routinely in such patients for detection of significant coronary artery disease. Little data exists on the prognostic value of cardiac nuclear scintigraphy in patients with preexisting LBBB. The purpose of our study was to determine the prognostic value of cardiac nuclear scintigraphy in patients with preexisting LBBB.

METHODS

Ninety-six patients with preexisting LBBB underwent perfusion imaging between July 1987 and June 1995. Thirty-seven underwent planar 201Tl imaging, and 59 underwent SPECT sestamibi imaging. Images were interpreted by consensus of two experienced observers and classified as normal, abnormal low risk and abnormal high risk. Outcomes measured were survival, cardiac and noncardiac death. The final study group included 43 women and 53 men, aged 42-83 (mean 66 +/- 9). Average follow-up was 3.4 +/- 2.1 yr.

RESULTS

Of the 96 patients examined, 31 had normal scans, 39 had low-risk scans and 26 had high-risk scans. At the end of the study period, 27 patients with normal scans were still alive while 2 suffered cardiac death and 2 suffered noncardiac death. Of those with low-risk scans, 36 survived while 2 suffered cardiac death and 1 suffered noncardiac death. Finally, of those with high-risk scans, 17 survived while 8 suffered cardiac death and 1 suffered noncardiac death (chi-square test, p = 0.020).

CONCLUSION

Dipyridamole imaging is an important prognostic tool for predicting future cardiac events in patients with preexisting LBBB and aids in their risk stratification for coronary artery disease.

Prognostic significance of exercise-induced left bundle-branch block

CONTEXT

Approximately 0.5% of all patients who undergo exercise testing develop a transient left bundle-branch block (LBBB) during exercise, but its prognostic significance is unclear.

OBJECTIVE

To determine whether exercise-induced LBBB is an independent predictor of mortality and cardiac morbidity.

DESIGN

Matched control cohort study. Between September 1990 and February 10, 1994, 17277 exercise stress tests were performed on patients.

SETTING

Tertiary care, academic medical center.

PATIENTS

From the cohort, 70 cases of exercise-induced LBBB were identified. The controls comprised 70 individuals without LBBB at rest or during exercise that matched the 70 cases based on age, test date, sex, prior history of coronary artery disease, hypertension, diabetes, smoking, and beta-blocker use.

MAIN OUTCOME MEASURES

All-cause mortality, percutaneous coronary intervention, open heart surgery, nonfatal myocardial infarction, documented symptomatic or sustained ventricular tachydysrhythmia, or implantation of a permanent pacemaker or an implantable cardiac defibrillator.

RESULTS

A total of 37 events (28 events from the exercise-induced LBBB cases and 9 from the control cohort) occurred in 25 patients (17 exercise-induced LBBB patients and 8 control patients) during a mean follow-up period of 3.7 (0.9 years) (median, 3.8 years [range, 0.9-5.2 years]). There were 7 deaths, of which 5 occurred among patients with exercise-induced LBBB. Four-year Kaplan-Meier event rates were 19% among exercise-induced LBBB patients and 10% among controls (log-rank chi2, 5.2; P=.02). After further adjusting for small differences in age, exercise-induced LBBB remained associated with a higher risk of primary events (adjusted relative risk, 2.78; 95% confidence interval, 1.16-6.65; P=.02).

CONCLUSION

Exercise-induced LBBB independently predicts a higher risk of death and major cardiac events.

Acute myocardial infarction and complete bundle branch block at hospital admission: clinical characteristics and outcome in the thrombolytic era. GUSTO-I Investigators. Global Utilization of Streptokinase and t-PA [tissue-type plasminogen activator] for Occluded Coronary Arteries

OBJECTIVES

We sought to assess the outcome of patients with acute myocardial infarction (MI) and bundle branch block in the thrombolytic era.

BACKGROUND

Studies of patients with acute MI and bundle branch block have reported high mortality rates and poor overall prognosis.

METHODS

The North American population with acute MI and bundle branch block enrolled in the Global Utilization of Streptokinase and t-PA [tissue-type plasminogen activator] for Occluded Coronary Arteries (GUSTO-I) trial was matched by age and Killip class with an equal number of GUSTO-I patients without conduction defects.

RESULTS

Of all 26,003 North American patients in GUSTO-I, 420 (1.6%) had left (n = 131) or right (n = 289) bundle branch block. These patients had higher 30-day mortality rates than matched control subjects (18% vs. 11%, p = 0.003, odds ratio [OR] 1.8) and were more likely to experience cardiogenic shock (19% vs. 11%, p = 0.008, OR 1.78) or atrioventricular block/asystole (30% vs. 19%, p < 0.012, OR 1.57) and to require ventricular pacing (18% vs. 11%, p = 0.006, OR 1.73). Bundle branch block also carried an independent 53% higher risk for 30-day mortality. Thirty-day mortality rates for patients with complete, partial and no reversion of the bundle branch block were 8%, 12% and 20%, respectively (two-tailed chi-square test for trend 5.61, p = 0.02, OR 0.34 for complete reversion, OR 0.55 for partial reversion).

CONCLUSIONS

Bundle branch block at hospital admission in patients with acute MI predicts in-hospital complications and poor short-term survival.

Incidence, clinical characteristics, and prognostic significance of right bundle-branch block in acute myocardial infarction: a study in the thrombolytic era

BACKGROUND

Whereas the significance of right bundle-branch block (RBBB) in acute myocardial infarction was extensively studied in the prethrombolytic era, a possible change in the overall incidence and meaning of RBBB as a consequence of thrombolytic therapy is not well known.

METHODS AND RESULTS

A multicenter, prospective study of 1238 patients consecutively diagnosed with acute myocardial infarction and admitted to three coronary care units was conducted. ECGs during the acute phase and clinical events until discharge and 1-year follow-up were monitored. In the 135 (10.9%) patients in whom RBBB was found, there were 51 (37.8%) new cases, 46 (34.1%) old cases, and 38 (28.1%) cases with an indeterminate time of origin. New RBBB was permanent in 26 and transient in 25 patients. RBBB was isolated in 76 (56%) and bifascicular in the remaining 59 (44%) patients. The following complications were more frequently associated with RBBB than non-RBBB patients: heart failure, 24% versus 46% (P<.001); use of pacemaker because of atrioventricular block, 3.6% versus 11% (P<.001); and 1-year mortality, 17.6% versus 40.7% (P<.001). Early mortality was significantly higher for new RBBB (43.1%, P<.001) than for old (15.5%) and indeterminate (15.3%) RBBB. These figures for 1-year mortality were 58.8% (P<.001), 35.5 (P<.01), and 23% (NS), respectively. Permanent and transient RBBB had different mortality rates: early mortality, 76% versus 8%, and 1-year mortality, 84% versus 32% (P<.001 for both). For isolated RBBB versus bifascicular block, early mortality was 14.4% versus 40.6%, and 1-year mortality was 30.2% versus 54.2% (P<.05 for both). Multivariate analysis showed an independent prognostic value of RBBB for early and 1-year mortality.

CONCLUSIONS

The overall meaning of RBBB in acute myocardial infarction has not changed in the thrombolytic era, although a higher rate of new and transient RBBB and a lower rate of bifascicular block may represent a beneficial effect of thrombolytic therapy.

Mortality analysis of complete right and left bundle branch block in a selected community population

A twenty year follow up of a selected, community population with complete right and left bundle branch block is reviewed by comparative mortality analysis. In this population, where cases and controls were free of hypertension and heart disease at entry, the presence of complete right bundle branch block does not have excess mortality. Complete left bundle branch block exhibits excess total and cardiac mortality.

Incidence and clinical relevance of the occurrence of bundle-branch block in patients treated with thrombolytic therapy

BACKGROUND

Whether thrombolytic therapy alters the incidence and clinical outcome of bundle-branch block is unclear.

METHODS AND RESULTS

We examined the occurrence of new-onset bundle-branch block, both transient and persistent, in 681 patients with acute myocardial infarction enrolled in the Thrombolysis and Angioplasty in Myocardial Infarction 9 and Global Utilization of Streptokinase and t-PA for Occluded Arteries 1 protocols. Each patient underwent continuous 12-lead ECG monitoring for 36 to 72 hours with the Mortara ST monitoring system. Bundle-branch block was characterized as right, left, alternating, transient, or persistent. The overall incidence of bundle-branch block was 23.6% (n = 161), with transient block in 18.4% (n = 125) and persistent block in 5.3% (n = 36). Right bundle-branch block was found in 13% (n = 89) of the population; left bundle-branch block was found in 7% (n = 48). Alternating bundle-branch block was seen in 3.5% (n = 24) of patients. Left anterior descending artery infarcts accounted for most bundles (54%, n = 79). Patients with bundle-branch block had lower ejection fractions, higher peak creatine phosphokinase levels (P < .0001), and more diseased vessels (P < .019). Mortality rates in patients with and without bundle-branch block were 8.7% and 3.5%, respectively (P < .007). A higher mortality rate was observed in the presence of persistent (19.4%) versus transient (5.6%) or no (3.5%) bundle-branch block (P < .001).

CONCLUSIONS

Thrombolytic therapy reduces the overall mortality rate associated with persistent bundle-branch block. However, persistent bundle-branch block remains predictive of a higher mortality rate than either transient or no bundle-branch block. Continuous 12-lead ECG monitoring provides an accurate characterization of the incidence and type of conduction disturbances after acute myocardial infarction.

Natural history of isolated bundle branch block

The purpose of this study was to determine the long-term outcome of patients with bundle branch block (BBB) who have no clinical evidence of cardiovascular disease. Among 110,000 participants in a screening program, 310 subjects with BBB without apparent of suspected heart disease were identified. Their outcome after a mean follow-up of 9.5 years was compared with that of 310 similarly screened age- and sex-matched controls. Among the screened population, isolated right BBB was more prevalent than isolated left BBB (0.18% vs 0.1%, respectively; p<0.001), and the prevalence of each abnormality increased with age (p<0.001). Total actuarial survival was no different for those with left BBB or right BBB and their respective controls. Cardiac mortality, however, was increased in the left BBB group when compared with their controls (p=0.01, log rank test). Left BBB, but not right BBB, was associated with an increased prevalence of cardiovascular disease at the follow-up (21% vs 11%; p=0.04). In the absence of clinically overt cardiac disease, the presence of left BBB or right BB is not associated with increased overall mortality. Isolated left BBB is associated with an increased risk of developing overt cardiovascular disease and increased cardiac mortality.

[2-year survival in persons with bundle branch block]

A group of 335 patients was examined. There were 172 men (average age 60.2 +/- 13.3 years) and 163 women (average age 59.3 +/- 11.3 years) with bundle branch block. In the period of two years 21 patients (6.26%) died. The greatest mortality was noted in patients with complete left bundle branch block (15.3%), especially in men (24.1%). The difference between complete left bundle branch block and complete right bundle branch block (chi 2 = 6.73; p < 0.01) was statistically significant. There was no significant difference in the mortality of patients with bifascicular heart block and trifascicular heart block in relation to the mortality of patients with complete right bundle branch block (chi 2 = 0.81; p > 0.05).

Clinical significance of complete left bundle branch block in dilated cardiomyopathy

Clinical, electrocardiographic and echocardiographic findings in 64 patients with dilated cardiomyopathy were restrospectively studied. Compared with 51 patients without complete left bundle branch block (CLBBB), 13 patients with CLBBB had higher New York Heart Association (NYHA) functional class (P < 0.05), increased left ventricular end-diastolic and end-systolic diameters (P < 0.002) and myocardial mass (P < 0.02), severe mitral regurgitation (P < 0.01) and higher mortality rate (P < 0.04). Multivariate stepwise regression analysis revealed that the presence of CLBBB was an independent prognostic factor for patients with dilated cardiomyopathy.

Bundle branch block in acute Q wave inferior wall myocardial infarction. A high risk subgroup of inferior myocardial infarction patients. The SPRINT Study Group. Secondary Prevention Reinfarction Israeli Nifedipine Trial

The aim of this study was to determine the incidence and impact of right and left bundle branch block on the in-hospital, 5-year and 10-year mortality of patients with acute inferior Q wave myocardial infarction. A retrospective analysis of clinical characteristics, hospital, 1-, 5-, and 10-year mortality of 2215 consecutive patients with acute inferior Q wave myocardial infarction hospitalized in 13 coronary care units in Israel was performed. Bundle branch block during acute Q wave inferior wall myocardial infarction was present in 108 patients (4.9%), 85 of whom had right and 23 left bundle branch block. Patients with bundle branch block had more in-hospital complications than those without, irrespective of the site and time of appearance of the block. In addition, atrial fibrillation (19%), complete atrioventricular block (21%) and congestive heart failure (45%) appeared more frequently in patients with, than in those without, bundle branch block (11%, 9% and 31%, respectively), and in-hospital and 5-year mortality were higher in patients with the block (22%, 33%) than in those without it (13% and 23%, respectively). Bundle branch block emerged as an independent predictor of death only among patients with new right bundle branch block, and right bundle branch block emerged as an independent predictor for the development of complete atrioventricular block (odds ratio 2.13; 90% confidence interval 1.39-3.28). However, hospital mortality among patients with inferior myocardial infarction and complete atrioventricular block was virtually independent of bundle branch block (39% with vs 36% without bundle branch block, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Diagnostic and prognostic accuracy of the exercise electrocardiogram in patients with preexisting right bundle branch block

The value of exercise testing in patients with right bundle branch block (RBBB) is uncertain. A retrospective review of 3609 patients who underwent exercise testing identified 163 (4.5%) with preexisting RBBB. After excluding those with coronary artery bypass graft(s), 133 patients remained and 48 (36%) had a prior myocardial infarction. Angiograms were available for 30 (23%) patients. After a mean follow-up of 33 +/- 23 months, seven patients had a fatal or nonfatal myocardial infarction. Twenty five (19%) patients had > or = 1 mm of non-upsloping ST depression in leads V5 or V6. With angiographic disease or previous myocardial infarction used as endpoints of coronary artery disease, the exercise test had a sensitivity of 27% (15/56), a specificity of 87% (67/77), and a predictive accuracy of 62% (82/133), (chi 2 = 4.04, p = 0.04). There were 24 deaths, a 10% annual mortality rate. Univariate analysis of clinical, exercise, and angiographic data revealed that nonsurvivors had a lower peak systolic blood pressure, a lower exercise capacity in METS, and a higher prevalence of coronary artery disease (p = 0.0001, p = 0.02, p = 0.03, respectively). Left ventricular ejection fraction and the amount of additional ST depression during exercise did not differ significantly (p = NS). Receiver operating characteristic curve analysis revealed that systolic blood pressure (area = 0.741, z = 5.22, p < 0.001) and exercise capacity (area = 0.66, z = 3.12, p = 0.009) were predictive of mortality, whereas additional ST depression during exercise (area = 0.588, z = 0.70, p = 0.24) was not.(ABSTRACT TRUNCATED AT 250 WORDS)

Long-term results of primary closure for ventricular septal defects in the first year of life

The long-term results of primary closure for large ventricular septal defects (VSDs) in infants under 1 year of age with severe symptoms were studied over a period of more than 10 years. Between January, 1971 and March, 1982, 49 infants underwent primary closure of a VSD through a right ventriculotomy using complete cardiopulmonary bypass with mild hypothermia. There were four hospital deaths but no late deaths. Two of four infants with residual shunts had a left ventricular-right atrial shunt which necessitated reoperation. Surgical heart block occurred in two infants who recovered sinus rhythm in the late period. The cardiothoracic ratio decreased from 60.5% preoperatively to 50.6% in the late postoperative period. Examination by cardiac catheterization revealed that the pulmonary-to-systemic pressure ratio (Pp/Ps) of 23 patients with a Pp/Ps of over 0.75 fell from 0.89 +/- 0.09 preoperatively to 0.42 +/- 0.12 by 1 month postoperatively, then to 0.27 +/- 0.05 in the late postoperative period. The latest values for the cardiac index and left ventricular ejection fraction were 3.4 l/min per m2 and 64.4%, respectively. More than 10 years after their operation, all the survivors were growing normally and maintaining a good quality of life, which supports our recommendation that primary repair should be performed in the first year of life for infants with large VSDs.

Initial clinical results of myocardial revascularization with the internal mammary artery for evolving myocardial infarction

In 25 patients undergoing emergency revascularization for an evolving myocardial infarction, the internal mammary artery (IMA) was used as graft. To bridge the time needed for harvesting the IMA, the left ventricle was totally decompressed by means of the extracorporeal circulation. Cardioplegia was delivered retrogradely, in order to achieve a good distribution in the jeopardized area. One patient died postoperatively, and eight patients showed a postoperative myocardial infarction. These initial results suggest that, with an adapted operative strategy, the IMA can be used as graft even in emergency revascularization.

The role of arrhythmia and left ventricular dysfunction in patients with acute myocardial infarction and bundle branch block

To determine the immediate and remote prognostic significance of bundle branch block (BBB) associated with acute myocardial infarction (AMI), 40 patients with AMI and BBB were studied. One hundred forty-four patients with AMI but without BBB were evaluated during the in-hospital phase and 45 of them were taken as a control group. These patients were followed for an average of 15 months (3-28 months). Arrhythmias and left ventricular function were investigated with 24-hr Holter monitoring and echocardiography, respectively. The hospital mortality was significantly greater in patients with BBB than in the control group (32.5% vs 10.4%, p < 0.001). The main cause of mortality was pump failure in the group with BBB (76.9%) and ventricular fibrillation in the control group (53.3%). The peak creatine kinase level was significantly higher in the group with BBB than in the control group (2094.8 +/- 288.4 IU/L vs 416.7 +/- 30.5 IU/L, p < 0.001). In patients with BBB prophylactic temporary pacemaker insertion was not found to improve the hospital mortality rate. In the hospital phase, although 32% of the patients with BBB had complicated arrhythmias (multiform, paired VPB, runs, R-on-T) the cause of death in 10 of the 13 patients who died was pump failure but not arrhythmia. In patients with BBB the wall motion index and the number of patients who had a left ventricular aneurysm were greater than in patients without BBB (9.5 +/- 0.9 vs 6.3 +/- 0.6, p < 0.01 and 52.0% vs 14.3%, p < 0.01, respectively). In patients with BBB follow-up mortality (12.0%) was lower than hospital mortality (32.5%). During the follow-up period there was no significant difference between patients with BBB and those without with regard to complicated arrhythmias (14.8% vs 15.6%). These results indicate that the main cause of poor prognosis during the hospital period in patients with AMI and BBB was not arrhythmia or conduction disturbance but severe pump failure due to extensive myocardial necrosis. Prophylactic temporary pacemaker insertion did not improve the hospital mortality rate of these patients, and patients with AMI and BBB who survive the in-hospital phase after infarction have a good prognosis during the following 15 months.

Impact on survival of a decade of change in the management of patients who have sustained a myocardial infarction

The survival of 906 consecutive patients who had sustained an acute myocardial infarction was monitored between the beginning of week 2 and the end of week 52. Deaths which occurred during this period were successfully predicted in terms of just 6 features; namely the value of left ventricular systolic time intervals measured during the 1st week, the occurrence of a myocardial infarction prior to the current hospitalisation, the patient's age, the coexistence of diabetes mellitus, the presence of left or right bundle branch blocks, and the administration of a diuretic agent while the patient was in hospital. By means of stepwise linear discriminant analysis predictions of mortality among the first 302 patients based upon these 6 features were 80% specific and 63% sensitive. Prognostic features derived from the first 302 patients were then used to predict mortality among the remaining 604 patients. Observed and predicted mortalities were similar for both sets of patients. Although mortality was similar, the 604 latter patients had received a considerably more interventional style of management than patients in the former group. Possible reasons for this failure of a change of management to improve prognosis are discussed.

Clinical and electrophysiologic findings in acute ischemic intraHisian bundle-branch block

Clinical and electrophysiologic features of acute ischemic right bundle-branch block (RBBB) that are reversible by His bundle pacing were analyzed in nine patients. All had large anterior myocardial infarctions (mean peak CK-MB = 185 +/- 71 IU/l), and six showed increased pulmonary capillary pressures. The RBBB occurred within 48 hours of infarction, and in six patients it was associated with left fascicular block. The HV intervals that were measured 1 to 4 days after infarction were normal in all patients. Progression to complete atrioventricular (AV) block occurred in three patients, and one patient required permanent cardiac pacing. Sustained ventricular tachycardia developed in two patients, and ventricular fibrillation developed in five. During a mean follow-up period of 26 months, four patients died (three of them suddenly). The RBBB disappeared in only one case. Acute ischemic intraHisian RBBB occurred in the setting of massive myocardial infarctions complicated by ventricular tachycardia or fibrillation and by a high mortality rate during the follow-up period. The RBBB rarely reverted spontaneously, and the His-Purkinje conduction time was frequently normal.

Characteristics associated with early (less than or equal to 3 months) versus late (greater than 3 months to less than or equal to 3 years) mortality after acute myocardial infarction

To define the independent variables predictive of early versus late mortality after acute myocardial infarction (AMI), 420 consecutive patients were studied and divided into 3 groups: the 45 patients who died within the initial 3 months (group 1), the 45 patients who died greater than 3 months and less than or equal to 3 years after AMI (group 2) and the 330 greater than 3-year survivors (group 3). The stepwise logistic discrimination method was applied to clinical and laboratory variables recorded during hospitalization to distinguish among the 3 groups. Six independent variables were found to be predictive of early mortality: left ventricular function score (chi-square 26.2; p less than 0.00001), ventricular fibrillation (chi-square 9.3; p = 0.002), bundle branch block (chi-square 9.0; p = 0.003), history of previous AMI (chi-square 8.7; p = 0.003), age (chi-square 5.8; p = 0.02) and atrioventricular block (chi-square 3.8; p = 0.05). Three independent variables were found predictive of late mortality: age (chi-square 13.8; p = 0.0002), anterior location of the AMI (chi-square 4.0; p = 0.04) and a low peak creatine kinase-MB level (chi-square 3.8; p = 0.05). Only 2 variables were able to distinguish between early and late nonsurvivors: peak creatine kinase-MB level (chi-square 8.7; p = 0.003) and ventricular fibrillation (chi-square 4.6; p = 0.03). Thus, the sets of independent risk factors for early and late mortality after AMI are substantially different--suggesting that differing mechanisms are responsible for outcome.

Atrial fibrillation and mortality in an elderly population

Prospective data from Busselton, Western Australia, collected during triennial surveys from 1966-81 with follow-up of subjects to 1983, showed that atrial fibrillation (AF) was frequent in elderly people and associated with increased mortality. Of 1770 people aged over 60 years, 40 were in atrial fibrillation when first seen and a further 47 developed it during follow-up. Atrial fibrillation was positively associated with angina, history of a myocardial infarction and left bundle branch block. Relative mortality in those with atrial fibrillation compared with those without it, was 1.92 for all causes, 1.82 for death from cardiovascular causes (excluding stroke) and 3.78 for deaths from stroke, after adjustment by proportional hazards regression for confounding effects of age, sex, history of a myocardial infarction, an abnormal electrocardiogram, angina, cholesterol level systolic blood pressure and Quetelet's Index (weight/height2). The excess relative mortality declined with increasing age for both women and men. This raised relative mortality remained constant with time from the first detection of AF for all causes and cardiovascular causes but appeared to increase with time from detection for stroke death. The risk of death from stroke was greatest in the younger women. The observed risk of death from stroke in patients with AF suggests that anticoagulant use should be considered in selected patients.

Clinical implications of electrophysiology study findings in patients with chronic bifascicular block and syncope

Electrophysiology study was performed in 93 patients with bifascicular block and unexplained syncope. Clinical evidence of organic heart disease was present in 33 (35%). Electrophysiological abnormalities were detected in 45 patients (48%). Of these, 36 had distal conduction disease, including 28 with an HV interval greater than 55 ms (mean 76.4 ms), and eight who developed infraHisian block following either intravenous procainamide (four) or atrial pacing (four). Sick sinus syndrome was evident in six patients and a further two had carotid sinus hypersensitivity. Sustained monomorphic ventricular tachycardia (VT) was induced in only three patients, two of whom also had prolonged HV interval. Among the 93 patients, 45 had therapy which was guided by positive findings at electrophysiology study (Group 1). Of these, 42 received permanent pacemakers, two were treated with combined permanent pacing and antiarrhythmic drug therapy, and one was treated with antiarrhythmic drug alone. In addition, eight patients without electrophysiologic abnormalities were treated empirically by pacing (Group 2). Finally, 40 patients without electrophysiologic abnormalities received no specific therapy (group 3). At a mean follow-up of 39 months (range two-125 months), recurrence of syncope had occurred in 4% of Group 1 patients, and 25% of Group 3 patients (p less than 0.05). No patient in Group 2 had had recurrence. Total mortality was 40%, including 47% of patients in Group 1, 25% of Group 2, and 35% of Group 3. Death was sudden in seven patients. We concluded that among patients with bifascicular block and syncope, therapy directed by findings at electrophysiology study was associated with symptomatic improvement, but mortality was not significantly influenced.(ABSTRACT TRUNCATED AT 250 WORDS)

Ischemic blocks during early phase of anterior myocardial infarction: correlation with ST-segment shift

Of 760 consecutive cases with anterior acute myocardial infarction (AMI), 55 developed acute bundle-branch block (BBB), fascicular block, or high-degree atrioventricular block during the hyperacute ECG stage of AMI. According to the direction of the ST segment during the acute ischemic episode, patients were divided into two groups. Group A consisted of 32 patients who developed BBB during ST-segment elevation, positive T wave, and absent or minimal Q wave. Group B consisted of 23 patients who developed BBB during ST-segment depression and evolved into anterior AMI. Group A was characterized by a higher incidence of right BBB and left anterior hemiblock [91% vs. 26% and 56% vs. 13%, respectively (p less than 0.005)]. Group B was characterized by a higher incidence of left BBB and left posterior hemiblock [57% vs. 9% and 26% vs. 12%, respectively (p less than 0.001)]. The BBB was transient (disappearing within hours to one day) in 14 patients in Group A and in 5 patients in Group B. The incidence of progression to high-degree atrioventricular block was almost equal in the two groups (25% and 26%). The mortality rate was very high in both groups, but higher in Group B [74% vs. 59% (p = NS)] especially in those with LBBB (85%). Most patients died on the day of occurrence of BBB [Group A, 50% vs. Group B, 70% (p = NS)]. The causes of death in both groups were cardiogenic shock and/or electromechanical dissociation.(ABSTRACT TRUNCATED AT 250 WORDS)