Intraventricular conduction defects in acute myocardial infarction

Relation of New Permanent Right or Left Bundle Branch Block on Short- and Long-Term Mortality in Acute Myocardial Infarction Bundle Branch Block and Myocardial Infarction

The aim of this study was to investigate the prognosis associated with bundle branch block (BBB) depending on location, time of appearance, and duration in patients with myocardial infarction (MI). From January 1998 to January 2008, we recruited 5,570 patients with acute MI. Thirty-day and 7-year all-cause mortality, according to BBB location, time of appearance, and duration were analyzed by multivariable analyses. BBB was present in 964 patients (17.3%); right BBB (RBBB) 10.6% and left BBB (LBBB) 6.7%. Overall mortality rate at 30 days was 13.2% (n = 738) and 7 years was 6.34 deaths per 100 patient-year. Both RBBB and LBBB were more frequently previous, 42.9% and 58.8%. Compared with non-BBB, all BBB groups showed higher prevalence of co-morbidities, especially rates of diabetes (49.0% vs 34.3%, p <0.001) and more often heart failure during hospitalization (54.5% vs 26.6%, p <0.001). Compared with RBBB, patients with LBBB had a higher prevalence of co-morbidities and a higher mortality, especially the new BBB, 30 days: 52.5% versus 31.6% and 7 years (incident rate): 27.2 versus 13.3 per 100 patient-year. New transient BBB had lower heart failure on admission (42.6% vs 58.3%, p = 0.008) and 30-day mortality (20.3% vs 69.6%, p <0.001) compared with permanent in both locations. New permanent RBBB was independently associated with 30-day (hazard ratio [HR] 2.01, 95% confidence interval [CI] 1.45 to 2.79) and 7-year mortality (HR 3.12, 95% CI 2.38 to 4.09). New-permanent LBBB was independently associated with 30-day (HR 2.15, 95% CI 1.47 to 3.15) and 7-year mortality (HR 2.91, 95% CI 2.08 to 4.08). In conclusion, in patients with acute MI, the appearance of a new BBB was independently associated with a higher 30-day and 7-year all-cause mortality.

Right bundle-branch block in acute coronary syndrome: diagnostic and therapeutic implications for the emergency physician

Right bundle-branch block (RBBB) in the patient with acute coronary syndrome is a marker of significant potential cardiovascular risk; the RBBB pattern in the patient with acute coronary syndrome identifies a subgroup of patients with quite high short- and long-term morbidity and mortality. Right bundle-branch block is not an uncommon finding on an electrocardiogram in the emergency department patient, noted incidentally and thus without clinical import or, conversely, encountered in the early phase of significant cardiovascular dysfunction. This review will address RBBB in the acute coronary syndrome setting.

Prognostic significance of acute bundle branch block in patients with acute myocardial infarction

Background/Aim. Acute bundle branch block (ABBB) presence is associated with the increasing mortality of patients with acute myocardial infarction (AMI). The aim of this study was investigate ABBB influence with respect to in-hospital (IN) and long-term mortality in patients with AIM, as well as total mortality in follow-up, the presence of in-hospital congestive cardiac insufficiency (CCI) and the presence of CCI at follow-up. Methods. This study included 606 consecutive patients with AMI. A total of 415 (68.5%) were males and 191 (31.5%) females, mean age 64.0?11.9. After the dismissal the patients underwent 18-month follow-up period. Results. Acute bundle branch block was registered in 44 patients (7.2%), out of which 15 patients (2.4%) had the left (L) ABBB and 29 patients (4.8%) had the right (R) ABBB. The patients with ABBB showed higher proportion of IH CCI (Killip III and IV) and hypotension compared with the control group (patients without ABBB). In the group of patients with ABBB ?-blockers, statins, aspirin and ACE-inhibitors were less applied. All the three ABBB groups exhibited an increased IH mortality (ABBB 47.7% vs 11.2%, p < 0.01, ARBBB 55.1% vs 11.2% p < 0.01, ALBBB 33.3% vs 11.2%, p < 0.01). Follow-up mortality of the patients with ABBB and ALBBB was higher in comparison with the control group (log-rank p = 0.046 and log-rank p = 0.01, respectively), whereas the group with ARBBB did not show any differences (log-rank, p = 0.59). Conclusion. The patients with ABBB AMI are a risk group of patients that commonly exhibit both early and remote CCI accompanied by high mortality. That is the reason why this sub-group of AMI patients should receive an urgent diagnostics followed by aggressive therapeutic treatment. <br><br><font color="red"><b> This article has been retracted. Link to the retraction <u><a href="http://dx.doi.org/10.2298/VSP0901074U">10.2298/VSP0901074U</a></u></b></font>

Hemiblocks Revisited

The trifascicular nature of the intraventricular conduction system and the concept of trifascicular block and hemiblock were described by Rosenbaum and his coworkers in 1968. Since then, anatomic, pathological, electrophysiological, and clinical studies have confirmed the original description and scarce advances have been developed on the subject. In the present study, we attempt to review and redefine reliable criteria for the electrocardiographic and vectorcardiographic diagnosis of left anterior and posterior hemiblock. One of the most important problems related to hemiblocks is that they may simulate or conceal the electrocardiographic signs of myocardial infarction or myocardial ischemia and may mask or simulate ventricular hypertrophy. Illustrative examples of these associations are shown to help the interpretation of electrocardiograms. The incidence and prevalence of the hemiblocks is presented based on studies performed in hospital patients and general populations. One of the most common causes of hemiblocks is coronary artery disease, and there is a particularly frequent association between anteroseptal myocardial infarction and left anterior hemiblock. The second most important cause is arterial hypertension, followed by cardiomyopathies and Lev and Lenègre diseases. The hemiblocks may also occur in aortic heart disease and congenital cardiopathies. Left anterior hemiblock is more common in men and increases in frequency with advancing age. Evidence is presented regarding the relationship of spontaneous closure of ventricular septal defects, which may explain the finding of this and other conduction defects in young populations. Isolated left anterior hemiblock is a relatively frequent finding in subjects devoid of evidence of structural heart disease. Conversely, isolated left posterior hemiblock is a very rare finding; its prognostic significance is unknown and is commonly associated with right bundle-branch block. The most remarkable feature of this association is that the prognosis is much more serious with a great propensity to develop complete atrioventricular block and Adams-Stoke seizures.

Influence of conduction disturbances on clinical outcome in patients with acute myocardial infarction receiving thrombolysis (results from the ARGAMI-2 study)

Right bundle branch block and complete atrioventricular (AV) block are conduction disorders (CDs) that have been observed in 14% of patients admitted with ST-elevation acute myocardial infarction. CDs carry a poor prognosis, with a threefold increase in the mortality rate, mainly due to cardiogenic shock and recurrent fatal myocardial infarction at 1-year follow-up. According to multivariable analysis, CD was the second strongest predictor of death, after high Killip class. Compared with patients without CD, the 1-year outcome of patients with CD was identically worse, irrespective of whether CD appeared during admission, disappeared, or remained constant. Similar adverse outcomes were seen in patients with complete AV block and right bundle branch block.

[The incidence, clinical characteristics and prognostic significance of a left bundle-branch block associated with an acute myocardial infarct]

To assess the current incidence and meaning of left bundle-branch block associated with acute myocardial infarction we studied 1,239 patients consecutively admitted in three hospitals. Left bundle branch block was present in 42 cases (3.3%). Compared to the patients without left bundle-branch block, those with left bundle-branch block were older (70 +/- 8.8 versus 63.9 +/- 11.4 years; p < 0.001), and had a more prevalent history of diabetes, angina, myocardial infarction and heart failure. Left bundle-branch block was associated more frequently with female gender and poor left ventricular ejection fraction. Patients with left bundle branch block were admitted with a longer interval from the onset of the symptoms (7.8 +/- 6.3 versus 5.4 +/- 6.7 hours; p < 0.01) and received in a lesser rate thrombolytics agents (21% versus 56%; p < 0.001), than those without left bundle-branch block. Complications significatively associated with left bundle-branch block were: complete AV block; heart failure and one-year mortality (40.4% versus 19.5%, p < 0.01). Female gender, age and heart failure were independent predictors of mortality whereas left bundle-branch block was not. In conclusion, current incidence of left bundle-branch block in acute myocardial infarction is lower than that referred in the pre-thrombolytic era. Left bundle-branch block is accompanied by a low rate of thrombolysis, whereas a higher mortality rate of these patients seems to depend on their clinical characteristics.

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.

Incidence and prognostic significance of right bundle branch block in patients with acute myocardial infarction receiving thrombolytic therapy

We assessed the incidence and prognostic significance of right bundle branch block (RBBB) in patients with acute myocardial infarction (AMI) receiving thrombolytic therapy. A prospective, one-year follow-up study involving 681 consecutive patients treated with thrombolytic agents for AMI was performed. Seventy-four patients developed RBBB (46% new-onset, 24% old and 30% indeterminate). RBBB was more common in older patients with large anterior AMI. New-onset RBBB were often transient (56%) and 84% of them resolved within 12 h after admission. Complicating events during the hospital phase, such as ventricular arrhythmias and development of heart failure, were more frequent in patients with RBBB. In-hospital and one-year mortality were higher in patients with RBBB (22.9 and 40.5% compared to 7.9 and 12.3% respectively in patients without block, both p<0.001). New-onset, non-transient RBBB were associated with the highest mortality rates (73% at one-year follow-up). By multivariate analysis, RBBB was retained as independent predictor of in-hospital and one-year mortality. We conclude that new-onset RBBB in patients receiving thrombolytic therapy for AMI is often transient. The development of RBBB has a negative and independent prognostic impact on the survival during the hospital phase and at one-year follow-up.

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.

Isolated left posterior fascicular block: a reliable marker for inferior myocardial infarction and associated severe coronary artery disease

The electrocardiographic (ECG) pattern of isolated left posterior fascicular block (LPFB) is a rare condition. It seems that true LPFB is often not recognized, whereas in cases of simple QRS axis of +60 degrees to +100 degrees in the frontal plane, the diagnosis of LPFB is made erroneously. Both facts rely on controversial and partially misleading opinions in the literature. Therefore, a retrospective and prospective study was performed in order to determine the prevalence of LPFB and to correlate its presence to the underlying disease. Retrospective study: Of a cohort of 830 patients referred in 1988 to a cardiologic laboratory for invasive investigation of certain or suspected coronary artery disease (CAD), 163 patients had an old inferior myocardial infarction (IMI). Nine patients (5.5%) showed the typical pattern of LPFB; eight of these had three-vessel disease. The diagnosis of IMI had been made only in one case before entry of the patient into the hospital, since LPFB generally masks IMI. Prospective study: 2502 ECGs were investigated, 1710 from a department of cardiology and 792 from two departments of internal medicine. Six LPFBs were detected (0.24%), all associated with IMI and four of them with three-vessel CAD. It is concluded that LPFB is a rare but clinically important intraventricular conduction disturbance. Its appearance is reliably connected with IMI and generally reflects severe three-vessel CAD, requiring invasive investigation.

Influence of right bundle branch block on short- and long-term survival after acute anterior myocardial infarction

The impact of right bundle branch block on long-term prognosis after anterior wall myocardial infarction is unclear. In 932 patients with Q wave anterior infarction, the short- and long-term prognostic significance of the presence of right bundle branch block was analyzed. Compared with 754 patients without block, 178 patients with right bundle branch block after myocardial infarction showed an increased incidence of left ventricular failure (72% versus 52%, p less than 0.001) and increased in-hospital (32% versus 8%, p less than 0.001) and 1 year after hospital discharge (17% versus 7%, p less than 0.001) cardiac mortality rates. The presence of right bundle branch block was an independent predictor of increased in-hospital and 1-year mortality when entered in a multivariate analysis. However, the absence of left ventricular failure identified a subgroup of patients with right bundle branch block with low in-hospital (4%) and 1 year postdischarge (5%) cardiac mortality rates comparable with those of patients with neither failure nor right bundle branch block (1.7% and 4.8%, respectively). In the presence of left ventricular failure, patients with associated right bundle branch block had higher in-hospital (43% versus 14%, p less than 0.01) and 1 year postdischarge (24% versus 9%, p less than 0.01) cardiac mortality rates than those of patients with failure but no right bundle branch block. Thus, the presence of right bundle branch block after anterior myocardial infarction is an independent marker of poor prognosis.(ABSTRACT TRUNCATED AT 250 WORDS)

An ECG marker of underlying right ventricular conduction delay in the hyperacute phase of right ventricular infarction or ischemia

Patients with extensive right ventricular (RV) infarction or ischemia often have an accompanying RV conduction delay. Such patients frequently show precordial ST-T wave elevation, which hides the late r' wave in lead V1, making it difficult to recognize the RV conduction delay during the hyperacute phase. We noted that such patients occasionally exhibited a "cove"-shaped ST-T elevation in lead V1, which strongly suggested the presence of this complication even in the hyperacute stage. This report describes three instances of RV infarction or ischemia with this characteristic electrocardiographic sign. This sign appears to be a marker of RV conduction delay during the hyperacute stage of RV infarction or ischemia.

Conduction defects in acute myocardial infarction in the Chinese in Hong Kong

In order to delineate the conduction defects complicating acute myocardial infarction in the Chinese, 636 Chinese patients admitted into one of the three medical units of a general hospital in Hong Kong in the period 1973-80 were reviewed. A relatively high incidence of conduction defects was observed, including atrioventricular block (11.3%), right bundle branch block (12.7%) and left bundle branch block (3.3%). Right bundle branch block (whether isolated or combined with left fascicular block) and atrioventricular block complicating anterior Q-wave infarction were ominous, with a high incidence of pump failure, cardiogenic shock and cardiac arrhythmias. These are markers of massive infarction. Atrioventricular and bundle branch blocks complicating inferior Q-wave infarction were benign. Left bundle branch block appeared to be a more chronic lesion, with moderate mortality, and isolated left anterior hemiblock did not adversely affect the short-term outcome. These results conform well to the patterns seen in Western series. The high incidence of conduction defects, in particular right bundle branch block and atrioventricular block complicating anteroseptal infarction, indicates a more serious clinical spectrum of acute myocardial infarction in the Chinese, and could have contributed to a higher hospital mortality in the Chinese series.

Factors associated with persistent and transient fascicular blocks in anterior wall acute myocardial infarction

To determine the factors associated with persistent and transient fascicular blocks, 144 patients with Q-wave anterior wall acute myocardial infarction (AMI) were studied. Thirty-three patients had new onset of fascicular block considered to be a consequence of AMI. Multivariate analysis using 16 clinical variables revealed that the number of asynergic segments, serum potassium level and pericardial rub were significant factors related to the occurrence of fascicular block. Among the 33 patients with fascicular block, 18 had persistent (group 1) and 15 had transient (group 2) fascicular blocks. When the 2 groups with fascicular block were compared, group 1 had significantly more asynergic segments than group 2 (4.7 +/- 1.2 vs 3.7 +/- 1.6, respectively), whereas pericardial rubs were observed significantly more in group 2 (67%) than in group 1 (28%). Therefore, the inflammatory process of AMI was 1 of the mechanisms related to the occurrence of a transient fascicular block and a more extensive myocardial necrosis was associated with a persistent fascicular block.

Long-term prognostic significance and electrophysiological evolution of intraventricular conduction disturbances complicating acute myocardial infarction

Fifty-nine patients with post-infarctional, isolated intraventricular conduction disturbances (IVCD) who survived the acute stage of myocardial infarction were followed up after hospital discharge for a mean period of 11.4 +/- 4.8 months. Fourteen patients (24%) had HV interval prolongation (greater than 55 ms) during AMI (group A), and 45 patients had normal HV intervals (76%, group B). His bundle recordings were repeated during follow-up in 48 survivors after a mean period of 7.2 +/- 0.7 months. Infranodal conduction delay in the acute stage of infarction was correlated with a higher incidence of heart failure during AMI (78% of patients in group A vs 22% in group B, p less than 0.001), and with higher rate of cardiac mortality during follow-up (50% in group A vs 13% in group B, p less than 0.01). Survivors of group A showed a higher functional NYHA class, a higher incidence of CHF, and a higher prevalence of complex ventricular arrhythmias at Holter monitoring. No statistically significant difference in late sudden death was evident between the two groups of patients, and the global incidence of late AV block was 2%. At repeat His bundle recording no significant change (greater than 5 ms) in HV interval could be demonstrated in comparison to the acute phase recording, neither in patients with prolonged nor in patients with normal HV time. We conclude that HV prolongation in patients with isolated, post-infarctional IVCD is correlated with a worse prognosis, both during acute infarction and during the follow-up period, which presumably reflects wider anatomic damage in comparison to patients with normal HV time. The low incidence of late AV block and the electrophysiological demonstration of the stability of infranodal conduction several months after AMI indicate that these patients do not require permanent prophylactic pacing after acute myocardial infarction.

Isolated left posterior fascicular block associated with acquired ventricular septal defect

Isolated left posterior fascicular block in the absence of associated right bundle-branch block is a rare electrocardiographic finding. In view of its anatomy and the fact that it receives a dual blood supply, the posterior fascicle of the left bundle branch appears to be less vulnerable than the anterior fascicle or the right bundle. Mechanical disruption of the posterior fascicle can produce isolated left posterior fascicular block. This has been demonstrated in animal models. However, such occurrence has not been noted in humans. We present two cases of inferior wall myocardial infarction, complicated by rupture of the inferior septum, resulting in isolated left posterior fascicular block. The development of isolated left posterior fascicular block complicating myocardial infarction may, therefore, serve to alert to the possible underlying septal rupture.

Right axis deviation in acute myocardial infarction. Clinical significance, hospital evolution, and long-term follow-up

The incidence, in-hospital evolution, and long-term follow-up were studied in patients who developed acute deviation of the mean (frontal) QRS axis to the right during an acute myocardial infarction (AMI). Among 3,160 patients evaluated, 13 (0.41 percent) developed left posterior hemiblock (LPHB) and 57 (1.8 percent) developed an incomplete form of LPHB, the right axis deviation group (RAD). Patients in the LPHB group had a statistically significant higher incidence of in-hospital morbidity (69 percent incidence of congestive heart failure) and mortality (38.5 percent). Follow-up revealed a statistically significant higher incidence of cardiac symptomatology (angina pectoris and congestive heart failure) in the RAD group than in the control group, mainly in patients in whom RAD persisted for more than 24 hours. Patients developing LPHB during AMI constitute a high risk population with a high incidence of morbidity and mortality. Patients developing RAD constitute an intermediate group (between the LPHB and the control group) characterized by a high incidence of cardiac symptoms at the time of follow-up.

Bundle branch block in acute myocardial infarction

The management of patients with acute myocardial infarction complicated by bundle branch block is a significant clinical problem and represents 8% to 13% of patients with acute infarction. This study reviews the records of 606 patients with myocardial infarction admitted to our coronary care unit. Forty-seven (8%) had complete bundle branch block. The risk of developing high-degree AV block in these 47 patients was reviewed. There are no established therapeutic guidelines for patients with pre-existing bundle branch block and left bundle branch block in acute myocardial infarction. We found a high risk of progression in patients with pre-existing bifascicular block in the presence of anterior wall infarction (25%) as well as in patients with left bundle branch block with acute anterior wall infarction (100%). On the basis of our data and careful review of the literature, we recommend prophylactic pacemaker insertion in these high-risk groups.

Bundle branch block after myocardial infarction--a long term follow-up

Fifty-two patients with myocardial infraction complicated by bundle branch block (27 RBBB and 25 LBBB) survived the hospital period (1967--1972), and were followed up to December 1976. Actuarial survival curves revealed a worse mortality up to five years (P less than 0.05) for LBBB (68%) than for RBBB (33%). All deaths occurred in the first four years. In RBBB, additional hemiblock (seven patients) did not increase the risk of heart block nor worsen the prognosis--one death in seven patients (14%) compared to eight in 20 patients with isolated RBBB (40%). The previous literature on long term survival of BBB was reviewed. Recommended treatment for BBB, a marker of severe myocardial damage, includes antiarrhythmic prophylaxis for anteroseptal infarction with RBBB, aneurysmectomy in selected subsets of patients, and possibly prevention of RBBB or its complications by treatment for reduction of infarct size during the very early phase after onset of infarction.

The clinical significance of bundle branch block complicating acute myocardial infarction. 1. Clinical characteristics, hospital mortality, and one-year follow-up

To provide an understanding of the clinical characteristics of patients with acute myocardial infarction (MI) and bundle branch block, experience from five centers was accumulated. Patients in whom bundle branch block first appeared after the onset of cardiogenic shock were excluded. In 432 patients, the most common types of block were left (38%) and right with left anterior fascicular block (34%). In 42% of the patients, bundle branch block was new. Progression to high degree (second or third degree) atrioventricular (AV) block via a Type II pattern occurred in 22% of the patients. Hospital and first year follow-up mortality rates were 28% and 28%, respectively. Only 46% of the patients developed pulmonary edema or shock (Killip Class III or IV), and hospital mortality was related to the amount of heart failure (8%, 7%, 27%, 83% for Killip Classes I-IV, respectively). Patients with progression to second degree or third degree AV block via a Type II pattern had increased hospital mortality compared with patients without this complication (47% vs 23%, P less than 0.001). In the absence of pulmonary edema or shock, patients with Type II second degree or third degree AV block still had a higher mortality rate than patients without advanced AV block (31% vs 2%, P less than 0.005), with nearly all the deaths due to abrupt development of AV block. Thus, in many patients MI with bundle branch block is associated with severe heart failure. However, this was not true for a majority of the patients, in whom therapy aimed at preventing morbidity and mortality due to the bradyarrhythmia of advanced AV block might be beneficial.

The clinical significance of bundle branch block complicating acute myocardial infarction. 2. Indications for temporary and permanent pacemaker insertion

The indication for prophylactic temporary and permanent pacing during acute myocardial infarction (MI) complicated by bundle branch block is high risk of progression via a Type II pattern to second or third degree (high degree) AV block during hospitalization or follow-up. In this study, determinants of high degree AV block during hospitalization and sudden death or recurrent high degree block during the first year of follow-up were examined in 432 patients with MI and bundle branch block. Timing of onset of bundle branch block, the involved fascicles, and the PR interval were examined as determinants of risk of progression to high degree AV block during MI. At highest risk were 186 patients with blocks involving the right bundle and at least one fascicle of the left bundle which were not documented on prior electrocardiograms. Risk was similar with (38%) or without (31%) accompanying first degree AV block. Patients with transient high degree AV block during MI had a 28% incidence of sudden death or recurrent high degree block during the first year of follow-up. Patients not continuously paced had a higher incidence of sudden death or recurrent high degree block than patients continuously paced (65% vs 10%, P less than 0.001). Sudden death during follow-up also occurred in 13% of patients without high degree block during MI. A subgroup with 1) documented prior MI, 2) anterior or indeterminant acute MI, and 3) no symptoms of cardiac failure had a 35% risk of sudden death. The role of permanent pacing in this group is unknown. Thus, patients at high risk of high degree AV block should receive prophylactic temporary pacing. Patients who survive high degree block with MI should receive temporary and then permanent pacing. Patients without high degree AV block during MI who nervertheless have a high risk of sudden death may benefit from permanent pacing.

The prognostic value of the HV interval in patients with acute myocardial infarction and bundle branch block

HV intervals were measured in 42 of 119 patients in the acute phase of myocardial infarction associated with bundle branch block (BBB). The mean HV intervals of patients with right, left and incomplete bilateral BBB were similar. The hospital and subsequent mortality of patients with prolonged HV intervals did not differ significantly from that of patients with normal HV intervals. The HV interval appeared to remain stable over the following months in most patients in whom it was remeasured. We conclude that the HV interval cannot be used to select patients who might benefit from prophylactic long term pacing.

Frequency and significance of conduction defects in acute myocardial infarction

The frequency of intraventricular conduction defects was determined in 556 consecutive patients with proven acute myocardial infarction. Complete left bundle branch block was present in 23 patients and carried a high mortality rate (61 per cent). Complete right buldle branch block was the rarest defect to be seen in isolation (8 patients) and carried a lower mortality rate (38%). Lone left anterior hemiblock was present in 72 patients and was associated with a low mortality rate (13 per cent); left posterior hemiblock occurred in 32 patients (mortality rate 19 per cent). In a further 59 patients right bundle branch block with left anterior or posterior hemiblock in addition was present and these patients had a high mortality rate which was greater than isolated right bundle branch block or hemiblock alone. Complete atrioventricular block developed in 51 patients, 26 of whom had prior evidence of intraventricular conduction defect. Despite the use of temporary transvenous pacing, mortality in patients who developed complete heart block was significantly increased whether or not an intraventricular conduction defect was already present. The significance of these findings for the management of patients with myocardial infarction is discussed.

Incidence and significance of left anterior hemiblock complicating acute inferior wall myocardial infarction

The hospital course and serial vectorcardiograms of 56 consecutive patients with acute inferior wall myocardial infarction were reviewed. Left anterior hemiblock (LAH) complicating inferior wall myocardial infarction was diagnosed by vectorcardiographic criteria. Seven patients (12.5%) developed LAH between the first and third hospital day, while 49 patients did not. There was no significant difference between these two groups when compared for age, sex, incidence of congestive heart failure, atrial and ventricular arrhythmias, atrioventricular (A-V) block, hospital mortality, and previous hypertension, diabetes mellitus, and myocardial infarction. We conclude that LAH is a relatively common complication of acute inferior wall myocardial infarction, with no apparent effect on the clinical course.