Bundle branch block and sudden death

It is clear from the available data that the prognosis for patients with chronic BBB depends to a large extent on the presence and etiology, as well as the severity, of the associated heart disease. In most patients, the terminal event is usually one of heart failure or the complication of coronary artery disease. In the absence of clinically detectable heart disease, the long-term prognosis for this group of patients is good.Patients with chronic bundle branch block Have been shown to have an incidence of ventricular arrhythmias greater than that found in a normal population. The mechanism of sudden death in any single unmonitored patient is speculative. Most patients dying suddenly, especially those with coronary artery disease, probably do so from ventricular fibrillation. Patients with documented transient high-degree AV block are at a substantial risk of sudden death.No clinical variable (such as age, syncope, angina, shortness of breath), or physical finding (such as S₃ gallop, cardiomegaly, heart failure), or electrocardiographic finding (such as RBBB with LAD, RBBB with RAD, P-R interval prolongation), or electrophysiologic variable (such as A-H or H-V interval prolongation) is useful in predicting progression to complete heart block. All the above variables occur frequently in patients with BBB and yet the progression to CHB is relatively infrequent. One might single out His-Purkinje block with normal AV nodal conduction during atrial pacing as a possible marker for development of complete heart block. However, the opposite, namely a normal H-V interval, does not rule out progression to complete heart block.The data available on the use of pacing in patients with unexplained recurrent syncope or dizziness suggests that this approach is reasonable provided an effort has been made to exclude noncardiac cause for the symptoms. Some suggest that documentation of bradyarrhythmia or measurement of H-V interval is essential prior to institution of pacing. Further studies are needed to clarify this point.BBB complicating acute myocardial infarction places the individual at significant risk of developing congestive heart failure, with mortality usually secondary to myocardial failure or refractory ventricular arrhythmias. The pressence of high-degree AV block per se does appear to increase the mortality in patients without pump failure. Recent data suggest that immediate survival may be enhanced by prophylactic pacing in patients at high risk for abrupt complete heart block complicating acute myocardial infarction, but who do not manifest evidence of heart failure. The assumption that prophylactic pacing will improve survival of patients with bundle branch block and significant heart failure complicating acute myocardial infarction is purely speculative.Insufficient and conflicting data prevent a definitive statement regarding the usefulness of the P-R and H-V intervals as guidelines for the management of patients with recent-onset bundle branch block and acute myocardial infarction.Permanent pacing appears to benefit survivors of acute myocardial infarction complicated by BBB and transient high-degree AV block. However, the evidence is far from convincing.Little information is available on the influence of antiarrhythmic therapy on sudden death in patients with BBB. All currently used antiarrhythmic agents have a potentially high risk when administered to patients with BBB. Since there is no convincing prospective study as to the efficacy of drugs in preventing sudden death in patients with BBB, drug selection and its use in this group of patients remains at the discretion of the individual physician. It is based on the individual physician's experience with the drug in question and his perception of the benefit-to-risk ratio of the agent to be used.