Diminished short-term heart rate variability predicts inducible ventricular tachycardia

The purpose of this study is to determine whether short-term heart rate variability (HRV) can be used successfully to predict inducible ventricular tachycardia (VT).

A high-speed (300 mm/s) electrocardiographic 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 between several variables and a dichotomous dependent variable (inducible, clinical, or electrocardiographic evidence of VT).

Of 32 patients, 12 had inducible VT (inducible VT group) and 20 had no clinical or electrocardiographic evidence of VT (control group). Mean short-term HRV values were significantly lower in those with inducible VT than in the control group in all patients (25+/-15 ms, n=12 vs 67+/-22 ms, n=20; p<0.0001) and in patients with coronary artery disease or congestive 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 < or =50 ms in 11 of 12 patients (92%) with inducible VT, but was < or =50 ms in only 3 of 20 control subjects (15%; p<0.001). As a result of a stepwise selection procedure conducted within the logistic regression, only the short-term HRV was found to be predictive of inducible VT (p<0.0001).

Short-term HRV is significantly 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 below 50 ms.