Effects of left ventricular dysfunction on the circadian variation of ventricular premature complexes in healed myocardial infarction

Circadian variation in the onset of cardiovascular events including sudden cardiac death, myocardial infarction and ventricular arrhythmias has been described. The effect of left ventricular (LV) dysfunction on the circadian variation of ventricular premature complex (VPC) frequency was evaluated in 132 patients with frequent VPCs and reduced LV function after myocardial infarction. Patients were prospectively divided in 2 groups based on LV ejection fraction (EF) (those with LVEF 0.30, a distinct circadian variation of VPCs, and the expected morning increase in VPC frequency were present. In contrast, a distinct circadian variation of VPCs was absent in patients with LVEF ≤0.30. A circadian variation of VPC frequency was also absent in patients with severe symptomatic congestive heart failure (New York Heart Association class III–IV). Treatment with β-adrenoceptor blocking agents was associated with a loss of the circadian variation of VPC frequency. The circadian variation of heart rate was also blunted in the group treated with β-adrenoceptor blocking agents. The proportion of subjects manifesting a positive correlation between heart rate and VPC frequency was tower in subjects with LVEF 0.30 (46%) (p < 0.05). Thus, circadian variation of VPC frequency is absent in patients with severe LV dysfunction.