BACKGROUND: Atrioventricular conduction delay (AVCD) impairs left ventricular (LV) filling and consequently leads to a reduction of cardiac output. We hypothesized that in patients with severely depressed LV function and coexisting intraventricular conduction disturbances (IVCD), AVCD can affect exercise performance. Therefore, we evaluated the association of AVCD and exercise capacity in patients with heart failure (HFREF) and coexisting IVCD.

MATERIAL AND METHODS: We included patients with stable, chronic HFREF, LVEF <35%, sinus rhythm, and QRS ≥120 ms. PR interval and peak oxygen consumption (VO2 peak) were specifically investigated. Multiple regression analysis was used to adjust the association between PR interval and VO2 peak for possible confounders.

RESULTS: Most (57.5%) of the 40 included patients [20% female, aged 63±12, 47.5% of ischemic etiology (IHD)] were in NYHA class III. Mean PR interval was 196±38.1 ms. There were 26 (65%) patients with PR interval ≤200 ms and 14 (35%) with >200 ms. Groups were similar in clinical, laboratory, echocardiographic parameters, QRS morphology, and treatment regimens. VO2 peak was lower in patients with longer PR interval group as compared to shorter PR interval group (12.3±4.1 vs. 17.06±4.4, p=0.002). In the regression model, PR interval, female sex, and IHD remained important predictors of VO2 peak (partial=–0.50, p=0.003; rpartial=–0.48, p=0.005; rpartial=–0.44, p=0.01; R2=0.61).

CONCLUSIONS: Delayed AV conduction contributes to decreased exercise capacity in patients with HFREF and coexisting IVCD.

Keywords: atrioventricular block, Exercise Test, Heart Conduction System