DIMINISHED SHORT-TERM HEART-RATE-VARIABILITY PREDICTS INDUCIBLE VENTRICULAR-TACHYCARDIA

Purpose: The purpose of this study is to determine whether short-term heart rate variability (HRV) can be used successfully to predict induc ible ventricular tachycardia (VT). Methods: A high-speed (300 mm/s) el ectrocardiographic recording was obtained in 32 patients in the supine position prior to programmed ventricular stimulation. Beat-to-beat RR intervals (in milliseconds) were derived from an 11-beat strip (10 RR intervals). Logistic regression was used to study the relationship be tween several variables and a dichotomous dependent variable (inducibl e, clinical, or electrocardiographic evidence of VT). Results: Of 32 p atients, 12 had inducible VT (inducible VT group) and 20 had no clinic al or electrocardiographic evidence of VT (control group). Mean short- term HRV values were significantly lower in those with inducible VT th an in the control group in all patients (25+/-15 ms, n=12 vs 67+/-22 m s, n=20; p<0.0001 and in patients with coronary artery disease or cong estive heart failure or both (22+/-13 ms, n=11 vs 63+/-23 ms, n=11; p< 0.0001. For the group as a whole, short-term HRV was less than or equa l to 50 ms in 11 of 12 patients (92%) with inducible VT, but was less than or equal to 50 ms in only 3 of 20 control subjects (15%; p<0.001) . As a result of a stepwise selection procedure conducted within the l ogistic regression, only the short-term HRV was found to be predictive of inducible VT (p<0.0001). Conclusion: Short-term HRV is significant ly lower in subjects with inducible VT than in those without clinical or electrocardiographic evidence of VT. The probability of developing sudden death increases substantially when short-term HRV decreases bel ow 50 ms.