Effect of Left Ventricular Dyssynchrony on Cardiac Sympathetic Activity in Heart Failure Patients With Wide QRS Duration

Background: Dyssynchrony has various detrimental effects on cardiac function, but its effect on cardiac sympathetic activity is not fully understood. Methods and Results: We studied 50 heart failure patients who underwent cardiac resynchronization therapy (CRT). Cardiac sympathetic activity was assessed by I-123-metaiodobenzylguanidine (I-123-MIBG) scintigraphy as the delayed heart-to-mediastinum ratio (H/M ratio). Echocardiography was performed before and 7 months after CRT, and response was defined as a >= 15% decrease in end-systolic volume. Dyssynchrony was determined by the time difference between the anteroseptal-to-posterior wall using speckle-tracking radial strain (>= 130 ms predefined as significant). H/M ratio in patients with dyssynchrony was less than that in patients without dyssynchrony (1.62 +/- 0.31 vs. 1.82 +/- 0.36, P<0.05), even though ejection fraction was not significantly different (24 +/- 6% vs. 25 +/- 7%). Patients with dyssynchrony and H/M ratio >= 1.6 had a higher frequency of response to CRT (94%) and favorable long-term outcome over 3.0 years. In contrast, patients without dyssynchrony and H/M ratio <1.6 were more likely to show a lower frequency of response to CRT (0%) and unfavorable long-term outcome after CRT. Conclusions: Dyssynchrony is associated with cardiac sympathetic activity, and I-123-MIBG scintigraphy may be valuable for predicting the response to CRT. (Circ J 2012; 76: 382-389)