Background: In patients with congestive heart failure, QRS duration (QRSd) is correlated with left ventricular (LV) ejection fraction (LVEF), ventricular dyssynchrony and patients' prognosis. However, little is known about the relationships between paced QRS duration (pQRSd) to cardiac structures and function and ventricular dyssynchrony in patients with chronic right ventricular apical (RVA) pacing, which were investigated in this study.
Methods: Seventy patients implanted with DDD(R) pacemaker for high- or third-degree atrioventricular block were enrolled to study pQRSd and echocardiographic variables, including aortic root dimension (AO), left atrial dimension (LAD), LV end-systolic dimension (LVDs), LV end-diastolic dimension (LVDd), interventricular septum thickness (IVST), LV posterior wall thickness (LVPWT), LVEF, interventricular mechanical delay (IVMD), systolic asynchrony index (Ts-SD) and septal-to-lateral delay.The relationships between pQRSd and such variables were examined.
Results: The pQRSd correlated positively with LVDd (r = 0.3166, P < 0.05), LVDs (r = 0.3741, P < 0.05), LAD (r = 0.5848, P < 0.01), IVST (r = 0.2925, P < 0.05), and negatively with LVEF (r = -0.3037, P < 0.05). No significant correlations were found between pQRSd and AO, LVPWT, IVMD, Ts-SD and septal-to-lateral delay (all P > 0.05). There was no significant correlation between LVEF and IVMD, Ts-SD, septal-to-lateral delay (P > 0.05). However, IVMD, Ts-SD and septal-to-lateral delay were greater in patients with low LVEF than in patients with normal LVEF (P < 0.05). A cut-off value for pQRSd of 180 ms had a sensitivity of 85.71% and a specificity of 66.67% to detect left atrial dilation.
Conclusion: pQRSd is correlated with left cardiac structures and LV systolic function. pQRSd > or =180 ms indicates left atrial dilation. There is no correlation between pQRSd and ventricular dyssynchrony.