Relationship Between Calcium Channel Antagonists and Nocturnal Hypotension and Autonomic Imbalance in Patients With a Previous Myocardial Infarction

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The present study was conducted to evaluate the effect of calcium channel antagonists on diurnal changes in blood pressure and on autonomic function in 71 patients who were receiving a calcium channel antagonist because they had previously suffered a myocardial infarction. Ambulatory blood pressures and Holter ECGs were recorded simultaneously for 24 h. Autonomic function was assessed by heart rate variability, Nocturnal systolic pressure was ≥ 90 mmHg in 63 patients (group I) and <90 mmHg in 8 patients (group II). Significant day to night changes in high-frequency power (from 4.3±1.2 to 4.5±1.0/m ²) as well as in the ratio of low-frequency power to high-frequency power (from 1.3±0.1 to 1.1±0.2) were observed in group I, whereas such changes were blunted in group II. When the calcium antagonist was discontinued or the dose was reduced in group II, the autonomic imbalance improved along with elevation of nocturnal systolic blood pressure. Thus, nocturnal blood pressure should be monitored when such drugs are administered for the treatment of ischemic heart disease to a patient with a previous myocardial infarction. If nocturnal hypotension occurs, the dose should be reduced or the drug should be discontinued. (Jpn Circ J 1998; 62: 21-28)