Arrhythmogenic Marker for the Sudden Unexplained Death Syndrome in Thai Men

Abstract

Background Between 1981 and 1988, the Centers for Disease Control and Prevention reported a very high incidence of sudden death among young male Southeast Asians who died unexpectedly during sleep. The pattern of death has long been prevalent in Southeast Asia. We carried out a study to identify the clinical markers for patients at high risk of developing sudden unexplained death syndrome (SUDS) and long-term outcomes. Methods and Results We studied 27 Thai men (mean age, 39.7±11 years) referred because they had cardiac arrest due to ventricular fibrillation, usually occurring at night while asleep (n=17), or were suspected to have had symptoms similar to the clinical presentation of SUDS (n=10). We performed cardiac testing, including EPS and cardiac catheterization. The patients were then followed at ≈3-month intervals; our primary end points were death, ventricular fibrillation, or cardiac arrest. A distinct ECG abnormality divided our patients who had no structural heart disease (except 3 patients with mild left ventricular hypertrophy) into two groups: group 1 (n=16) patients had right bundle-branch block and ST-segment elevation in V 1 through V 3 , and group 2 (n=11) had a normal ECG. Group 1 patients had well-defined electrophysiological abnormalities: group 1 had an abnormally prolonged His-Purkinje conduction time (HV interval, 63±11 versus 49±6 ms; P =.007). Group 1 had a higher incidence of inducible ventricular fibrillation (93% for group 1 versus 11% for group 2; P =.0002) and a positive signal-averaged ECG (92% for group 1 versus 11% for group 2; P =.002), which was associated with a higher incidence of ventricular fibrillation or death ( P =.047). The life-table analysis showed that the group 1 patients had a much greater risk of dying suddenly ( P =.05). Conclusions Right bundle-branch block and precordial injury pattern in V 1 through V 3 is common in SUDS patients and represents an arrhythmogenic marker that identifies patients who face an inordinate risk of ventricular fibrillation or sudden death.