Relationship between left ventricular stimulation characteristics at implantation and echocardiographic response after 6 months of cardiac resynchronization therapy.

Objective: Although the electrical stimulation of an ischaemic tissue adversely affects the left ventricular (LV) systolic function, the optimal stimulation site in patients with non-ischaemic cardiomyopathy has not been systematically studied. We hypothesized that the local stimulation characteristics at the time of device implantation predict the response to cardiac resynchronization therapy (CRT).

Results: We measured the impedance, sensing, and capture threshold of a bipolar LV lead in 138 patients with non-ischaemic cardiomyopathy undergoing first implantation of CRT device for drug refractory heart failure. All patients underwent echocardiography at baseline and at 6 months post-implantation. An absence of favourable response to CRT was defined as <15% decrease in echocardiographic LV end-systolic volume (LVESV) at 6 months. Echocardiographic response to CRT was observed in 70% of patients. The LV lead measurements predicted neither the optimal stimulation site nor the response to CRT. Left ventricular capture threshold (1.50 ± 1.1 vs. 1.32 ± 0.8 V) and impedance (725 ± 287 vs. 720 ± 261 Ω) were similar between the responders and the non-responders. Independent of baseline LV ejection fraction or ESV, the LV R-wave amplitude at implantation was significantly higher (P = 0.0038) in responders (12.7 ± 5.2 mV) than in non-responders (9.7 ± 6.3 mV), with an area under the receiver operating characteristic curve of 0.7.

Conclusions: Response to CRT, as determined by decrease in LVESV at 6 months, was associated with significantly higher LV R-wave amplitude at the time of device implantation.