LOS ANGELES – The most common intraventricular conduction block following a myocardial infarction is a right bundle branch block, but it is also the least deadly and pathogenic. Left bundle branch blocks produced the most morbidity and mortality in a review of more than 25,000 myocardial infarction survivors from throughout New Jersey during 1994-2009.
The findings also showed that left anterior hemiblocks (LAHB) put post-MI patients in nearly as much jeopardy as did left bundle branch blocks (LBBB), Dr. John S. Pantazopoulos and his associates reported in a poster at the annual scientific sessions of the American Heart Association.
The researchers reviewed 16-year follow-up data from 25,026 patients enrolled in the Myocardial Infarction Data Acquisition System (MIDAS) run by the Cardiovascular Institute of New Jersey in New Brunswick. They excluded post-MI patients with congenital heart disease, a history of mitral regurgitation, atrial fibrillation, heart failure, a pacemaker, coronary bypass surgery, or a percutaneous coronary intervention prior to the first appearance of their intraventricular conduction block.
The most common conduction abnormality was a right bundle branch block (RBBB), in 13,454 patients (54%). LBBB occurred in 27%, 15% had LAHB, and 4% had LAHB plus RBBB. Dr. Pantazopoulos and his associates performed multivariate analyses to determine the morbidity and mortality risk faced by LBBB, LAHB, and LAHB plus RBBB patients compared with patients who only had RBBB. Their analysis controlled for several demographic and clinical confounders, including hypertension, diabetes, and renal failure.
The analysis showed that compared with patients with RBBB, those with LBBB had a 2.7-fold increased risk of cardiovascular death and a 48% increased rate of all-cause death, reported Dr. Pantazopoulos, a cardiologist at the Cardiovascular Institute of the University of Medicine and Dentistry of New Jersey in New Brunswick. Patients with LAHB had a 2.6-fold increased risk of cardiovascular death and 59% increased rate of all-cause death compared with RBBB patients, and those with LAHB plus RBBB had a 2.6-fold higher cardiovascular death rate and a 62% increased all-cause death rate. All these increases were statistically significant.
Patients with LBBB also had a 3.8-fold increased rate of developing heart failure during follow-up, a 68% increased rate of incident mitral regurgitation, and a 34% increased rate of atrial fibrillation compared with patients with RBBB. Patients with LAHB had a 2.6-fold increased rate of new-onset heart failure and a 15% higher rate of atrial fibrillation, and patients with both LAHB and RBBB had a 2.4-fold increased rate of heart failure. All of these increased rates were statistically significant.
Dr. Pantazopoulos said that he had no disclosures. The senior researcher on the study, Dr. John B. Kostis, has been a speaker for Merck, has received honoraria from Sanofi, and has received a research grant from Novartis.