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 less than or equal to 0.30, and those with LVEF between 0.30 and 0.45). Median hourly VPC frequencies and heart rates were compared between the 2 groups. Subgroup analyses based on treatment with beta-adrenoceptor blocking agents and on New York Heart Association functional class were also performed. In patients with LVEF greater than 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 less than or equal to 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 beta-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 beta-adrenoceptor blocking agents. The proportion of subjects manifesting a positive correlation between heart rate and VPC frequency was lower in subjects with LVEF less than or equal to 0.30 (26%) than in those with LVEF greater than 0.30 (46%) (p less than 0.05). Thus, circadian variation of VPC frequency is absent in patients with severe LV dysfunction.