Atrial enlargement in symptomatic heart block patients with preserved left ventricular function: Possibly related to atrioventricular dyssynchrony

Background: Right ventricular apical pacing may possibly induce atrial dilatation as a consequence of atrioventricular dyssynchrony. However, atrial enlargement associated with atrioventricular dyssynchrony due to atrioventricular block has never been studied. Methods: This case-control survey involved 90 patients with symptomatic atrioventricular block [29 patients with Mobitz type 2 atrioventricular block, 22 patients with high degree of atrioventricular block and 39 patients with complete atrioventricular block]. The control group comprised 54 age- and sex-matched patients with sick sinus syndrome and intact intrinsic atrioventricular conduction. The M-mode measurements were obtained before implant and the left and right atrial areas were measured by planimetry. Results: The peri-implant right atrial area (17.4 ± 3.7 vs. 15.3 ± 3.4 cm ², p = 0.002), left atrial area (24.9 ± 4.2 vs. 21.0 ± 3.7 cm ², p < 0.001) and left atrial diameter (36.4 ± 5.5 vs. 33.3 ± 4.8 mm, p = 0.001) were significantly greater in atrioventricular block patients than in sick sinus syndrome patients. The two groups had similar left ventricular ejection fraction. The right atrial area (p = 0.01) and left atrial area (p = 0.006) remained significantly greater in atrioventricular block patients than in sick sinus syndrome patients after adjustments for age, gender, body surface area, left ventricular dimension and left ventricular ejection fraction in multiple logistic regression analysis. Conclusions: Atrial enlargement occurs in patients with symptomatic atrioventricular block. This phenomenon is possibly related to atrioventricular dyssynchrony.