Association between right ventricular systolic function and electromechanical delay in patients with right bundle branch block.

Background: Elevated right ventricle (RV) pressure and/or volume can place stress on the right bundle branch block (RBBB) and its associated Purkinje network, which can affect its electrical properties, resulting in conduction delay or block. We hypothesized that prolonged R' wave duration in lead V1 would extend the later portion of the QRS complex and can act as an indicator of reduced RV function in patients with RBBB.

Method: Kosin University Gospel Hospital echocardiography and electrocardiography (ECG) database was reviewed to identify patients with complete RBBB between 2013 and 2015. ECGs recorded closest to the time of the echocardiography were carefully reviewed, and QRS and R' wave duration were measured. RV systolic dysfunction was defined as an RV fractional area change (FAC) less than 35%, as indicated by echocardiography guidelines.

Results: Compared to patients with normal RV function (n=241), patients with RV dysfunction (n=123) showed prolonged QRS duration (145.3±19.3ms vs. 132.2±13.4ms, p<0.001), predominantly due to R' prolongation (84.8±13.0ms vs. 102.9±12.0ms, p<0.001). R' duration was significantly associated with RV FAC (r=-0.609, p<0.001), RV systolic pressure (r=0.142, p=0.008), RV dimension (r=0.193, p<0.001), and RV myocardial performance index (r=0.199, p<0.001). On receiving operator characteristic curve analysis, V1 R' duration ≥93ms was associated with RV dysfunction with 90% sensitivity and 87% specificity (area under the curve: 0.883, 95% confidence interval=0.845-0.914, p<0.001).

Conclusion: Prolonged R' wave duration in lead V1 is an indicator of RV dysfunction and pressure and/or volume overload in patients with RBBB.