Aims: Interventricular (VV) delay optimization for cardiac resynchronization therapy (CRT) is recommended by current guidelines and several algorithms have been proposed. So far, however, no gold standard has been established in the clinical routine. We hypothesized that dyssynchrony parameter assessment might guide VV delay optimization and investigated whether dyssynchrony parameter changes induced by sequential biventricular pacing follow a predictable pattern.
Methods and results: We determined intra- and interventricular dyssynchrony in 80 CRT patients by echocardiographic quantification of the interventricular mechanical delay and the septal-lateral time to peak systolic velocity delay. Dyssynchrony parameters were assessed during simultaneous biventricular pacing as well as during sequential biventricular pacing with a right ventricular (RV) or left ventricular (LV) preactivation of 40 ms. Simultaneous biventricular pacing significantly improved inter- and intraventricular dyssynchrony parameters compared with preoperative baseline measurements. In general, dyssynchrony parameter changes induced by sequential biventricular pacing showed high interindividual variance and did not follow a predictable pattern. Intra- or interventricular dyssynchrony persisted during simultaneous biventricular pacing in 39 and 19% of our patients, respectively. Neither RV nor LV preactivation significantly decreased the number of patients with persistent intraventricular dyssynchrony. In contrast, LV preactivation significantly reduced the prevalence of interventricular dyssynchrony by 80%.
Conclusions: Left ventricular preactivation effectively ameliorates interventricular dyssynchrony, which persists in almost one in five CRT patients. Assessment of interventricular dyssynchrony and consecutive programming of LV preactivation in patients with persistent interventricular dyssynchrony may represent a pragmatic and time-effective approach to improve CRT in patients with inferior response.