More information is required on the relationship between electrical and structural reverse remodeling in patients treated with cardiac resynchronization therapy.
QRS and JT intervals were investigated during different pacing modes before and 3 months after implantation of a device for biventricular (BiV) pacing in 20 patients with severe drug-refractory heart failure (with left ventricular ejection fraction < 40% and QRS > 120 ms); structural remodeling was evaluated by echocardiography.
QRS interval was significantly shortened by BiV pacing both acutely (p=0.002) and at 3 months (p=0.007). No significant change was found in the JT interval. The extent of QRS shortening obtained by BiV pacing showed moderate correlations with the reduction of end-systolic and end-diastolic volumes (r=0.53, p=0.016 and r=0.45, p=0.045, respectively) as well as with increase of left ventricular ejection fraction (r=0.49, p=0.028) at 3 months. The widening of QRS observed during right ventricular (RV) pacing was greater after 3 months of BiV pacing (with respect to acute assessments), suggesting accentuation of pacing-induced electrical dyssynchrony after a period of pacing-induced resynchronization.
The extent of QRS shortening induced by BiV pacing appears to correlate with the reverse structural remodeling (in terms of reduction in end-systolic volume). The acute changes and the remodeling process occurring at mid-term in the overall population of CRT-treated patients do not appear to involve the JT interval. A period of pacing-induced resynchronization appears to accentuate the potential for RV pacing-driven electrical dyssynchrony.