Infranodal conduction abnormalities, including right or left bundle branch block bifascicular block, and nonspecific intraventricular conduction block are common electrocardiogram (ECG) abnormalities with uncertain persistence and prognostic significance. We evaluated their trajectory and prognostic significance in patients undergoing coronary angiography.
We linked an institutional ECG repository with the provincial coronary angiography registry and administrative databases. We included patients without severe left ventricular dysfunction who had an ECG within 180 days of angiography. Multivariable Cox models were used to assess associations between conduction abnormalities and a composite outcome, including all-cause mortality, heart failure hospitalizations, placement of a permanent pacemaker, and placement of an implantable cardiac defibrillator or cardiac resynchronization therapy defibrillator. Serial ECGs were used to model conduction disease as a time-dependent repeated measure.
We included 10,786 patients (mean age, 62.3 ± 12.4 years; 70.3% were male), of whom 2530 (23.4%) had baseline conduction abnormality. During a median follow-up of 3.5 years, conduction normalized in 885 patients (34.9%) and the composite outcome occurred in 1541 patients (14.3%). After multivariable adjustment, intraventricular conduction block (adjusted hazard ratio, 1.42; P = 0.001) and bifascicular block (adjusted hazard ratio, 1.59; P = 0.003) were associated with increased risk of the composite outcome. Left bundle branch block was not associated with the composite outcome.
Regression of conduction abnormalities was frequent among patients undergoing coronary angiography, primarily for suspected acute coronary syndrome. After adjustment for important confounders including extent of coronary artery disease, infranodal conduction abnormalities were associated with a modest increase in cardiovascular risk.

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