Purpose: To show a possible relation between heart rate and silent myocardial ischemia.
Methods: Forty-nine ischemic episodes were registered in six patients during a total period of 576-hour Holter monitoring. Those patients were selected from a group of 40 asymptomatic individuals after a first uncomplicated myocardial infarction; 11 (27.5%) showed ischemia during daily activities or exercise, the six selected patients had myocardial ischemia on Holter monitoring.
Results: The silent episodes consisted 92% of the total ischemic burden; they lasted from 1 min 30 s to 20 min and the ST-segment depression varied from -1.1 mm to 3.3 mm. Thirty-five (72%) episodes occurred at rest or during light physical activities; nine (18.5%) occurred between 7:00 AM and 12:00 PM; eight (16.5%), between 12:00 PM and 6:00 PM; 17 (35%) between 6:00 PM and 12:00 AM and 15 (30%), between 12:00 AM and 7:00 AM. There was no significant change (more than 20%) in heart rate at the onset of ischemic episodes in relation to the heart rate 1 minute before (94.63 +/- 9.79 bpm and 99.47 +/- 10.99 bpm, respectively). Complex ventricular arrhythmias occurred in all patients and only one of them had an episode of nonsustained ventricular tachycardia related to silent ischemia.
Conclusion: Our results suggest that there is no relation between heart rate, arrhythmias and silent ischemia.