Heart rate-dependent alteration of the frequency and coupling interval of ventricular arrhythmias as measured by 24-hour ECG monitoring.

Twenty-four hour ECG recordings of 132 patients with frequent (greater than 1000/day) ventricular premature contractions (VPCs) were analyzed using a computerized system, designed to evaluate the relationships between 1) the VPC frequency and heart rate (HR) (VPC-HR relation), 2) the coupling interval (CI) of VPCs and HR (CI-HR relation), and 3) the incidence of ventricular tachycardia (VT) and HR (VT-HR relation). The patterns of the VPC-HR relation included: 1) an increase in VPCs with increasing HR (positive correlation, 43 patients), 2) an increase in VPCs at low HR range and a decrease at high HR range, with increasing HR (bidirectional correlation, 74 patients), 3) a decrease in VPCs with increasing HR (negative correlation, 7 patients) and 4) constant VPCs over all HRs (flat correlation, 8 patients). Patients were divided into 2 broad categories according to whether they had a positive correlation (P group, 43 patients) or the other correlations (non-positive or NP group, 89 patients). Of 132 patients, the CI-HR relation was negative in 129 (98%) and positive in only 3 (2%). Patients with frequent VTs (10 or more events over 24h) were significantly more frequent in the P (9 patients, 21%) than in the NP group (7 patients, 8%, p less than 0.05). However, mean HR, mean CI, total VPC counts and the slope of CI-HR relation were not significantly different between the groups. The VT-HR relation observed in 16 patients with frequent VTs were positive in 9 of the P group and in 2 of the NP group and non-positive in 5 of the NP group.(ABSTRACT TRUNCATED AT 250 WORDS)