MYOCARDIAL SYMPATHETIC NERVOUS DYSFUNCTION DETECTED WITH IODINE-123-MIBG IS ASSOCIATED WITH LOW HEART-RATE-VARIABILITY AFTER MYOCARDIAL-INFARCTION

The association between myocardial sympathetic innervation and heart r ate variability after myocardial infarction was studied in a group of 12 men (aged 30-65 yr) 3 mo after their first myocardial infarction. M ethods: Viable myocardium was imaged using I-123-phenylpentadecanoic a cid (pPPA). Functioning myocardial sympathetic nervous tissue was imag ed using [I-123]-metaiodobenzylguanidine (MIBG). Heart rate variabilit y was measured as the ratio of maximum-to-minimum RR intervals in ECG during deep breathing. Results: The patients were divided into normal (n = 6) and low (n = 6) heart rate variability groups. Myocardial infa rction size (pPPA defect) was comparable in the normal and low heart r ate variability groups. Even the MIBG defect size was not significantl y different in the normal and low groups, the portion of viable myocar dium with impaired sympathetic innervation (MIBG defect minus pPPA def ect) was significantly greater in the low heart rate variability group than in the normal group. Conclusion: The extent of viable myocardium with disturbed sympathetic innervation was greater in patients with l ow heart rate variability as compared to those with normal heart rate variability 3 mo after myocardial infarction.