Cardiac sympathetic nerve activity in patients with hypertrophic cardiomyopathy with malignant ventricular tachyarrhythmias

Background. Malignant ventricular tachyarrhythmia (VT) and sudden death are serious events in hypertrophic cardiomyopathy (HCM). However, the pathophysiology of this condition is not well understood. The objective of this study was to evaluate the relationship between cardiac sympathetic nerve activity and the occurrence of VT in HCM patients. Methods and Results. We studied iodine 123 metaiodobenzylguanidine scintigraphy and 24-hour ambulatory electrocardiographic monitoring in 44 HCM patients, 15 with VT (group A) and 29 without VT (group B). With planar I-123 metaiodobenzylguanidine imaging, the heart-to-mediastinum ratio for early and delayed acquisition and washout rate were calculated. Polar maps of left ventricular myocardium were divided into 20 segments, and the SD of uptake and washout rate in 20 segments were calculated as indices of regional variation. The global washout rate was significantly higher in group A than in group B (26.8 +/- 6.4% vs 17.4 +/- 5.7%, P < .0001), although other parameters including heterogeneity indices did not differ. The logistic multiple regression analysis also determined that washout rate was the most powerful predictor of VT in patients with HCM. Conclusions. The occurrence of malignant VT in HCM may be associated with global cardiac sympathetic nerve activity rather than with the heterogeneity of this activity.