Impaired cardiac sympathetic innervation and myocardial perfusion are related to lethal arrhythmia: quantification of cardiac tracers in patients with ICDs

Abstract

Despite widespread prophylactic use of implantable cardi-overter defibrillator (ICD) therapy, sudden cardiac death and refractory arrhythmia events are still important clinical issues to be overcome. We examined whether the impairment of cardiac sympathetic innervation and myocardial perfusion is respon-sible for lethal arrhythmic events and has prognostic value by comparing conventional clinical indices. Methods: In con-secutive ICDs implanted in 60 patients, cardiac uptake of 123I-metaiodobenzylguanidine and 99mTc-tetrofosmin at rest was quantified, and then patients were prospectively followed with endpoints of appropriate ICD shocks or cardiac death. Cardiac metaiodobenzylguanidine activity was quantified as a heart-to-mediastinum ratio (HMR), and impaired tetrofosmin uptake was graded as a summed score (SS) using a computerized techni-que with a percentage of tracer uptake. Results: During a mea