Postero-lateral scar tissue resulting in nonresponse to cardiac resynchronization therapy

In large cardiac resynchronization therapy (CRT) trials, approximately 20-30% of patients did not respond to CRT. Recent studies indicated that left ventricular (LV) dyssynchrony is needed for response to CRT. However, the presence of LV dyssynchrony may not be the only determinant of response, because some patients with LV dyssynchrony do not benefit from CRT. In the current case report, we present a patient with ischemic cardiomyopathy, NYHA class III heart failure symptoms, and substantial LV dyssynchrony on tissue Doppler imaging who underwent CRT implantation but did not respond. Following CRT, LV dyssynchrony was not reduced and the patient did not improve in clinical symptoms or LV function. The lack of LV resynchronization was explained by the presence of extensive scar tissue in the region of the tip of the LV pacing lead resulting in ineffective LV pacing. In patients with ischemic cardiomyopathy and history of previous infarction, assessment of scar tissue should be considered before CRT implantation.