Abstract 3359: Sympathetic Myocardial Innervation and Prognosis in Hypertrophic Cardiomyopathy: A Prospective, Long-term Study in a Tertiary Center
The role of cardiac sympathetic activity in hypertrophic cardiomyopathy (HCM) patients remains unclear. Regional myocardial sympathetic innervation can be studied using single-photon emission computed tomography (SPECT) after administration of iodine-123 metaiodobenzyl-guanidine (I-123 MIBG). We prospectively evaluated a cohort of patients after they had undergone SPECT I-123 MIBG scintigraphy.
Methods: Twenty patients were followed for a mean (±SD) of 10±1 years after SPECT. Ten subjects served as controls. The difference in cardiac I-123 MIBG uptake was estimated as the heart to lung activity ratio (H/L). With regard to SPECT we used a semiquantitative method: the left ventricular wall was divided into 16 segments and each segment was scored with a 3-point scoring color scale (0=normal uptake or >75%; 1=moderate defect 50 –70%; 2=severe defect <50%). A score index (SI) was then calculated for 5-hours uptake study adding the single scores of all the 16 segments.
Results: H/L ratio for I-123 MIBG uptake was significantly reduced in HCM patients in comparison with normal subjects (1.29±0.1 vs.1.61±0.1, P<0.0001). Likewise, HCM patients showed higher degree of sympathetic dysinnervation compared with controls (8.5±2.9 vs. 2.2±2.1, P<0.0001). Ten patients (50%) had an unfavorable outcome (death from cardiovascular causes, heart transplantation, progression to heart failure, severe ventricular arrhythmias requiring ICD implantation) 2.1 to 6.1 years after SPECT. Of note, the patients with sudden cardiac death or ICD discharge (5 pts) showed a nearly normal sympathetic innervation (SI-MIBG=2.5±1.7), while patients with heart failure progression (5 pts) had a significantly sympathetic dysinnervation (SI-MIBG=16.2±3.6). Specifically, all 5 patients with heart failure had severe denervation and 3 of 5 with lifethreatening ventricular arrhythmias showed nearly normal innervation.
Conclusions: In HCM patients, normal sympathetic innervation is detectable in patients with lifethreatening ventricular arrhythmias, while remarkable denervation is correlated with ventricular myocardial dysfunction. These findings may entail potential impact on diagnostic and prognostic approach of HCM patients.