Heart rate variability during the acute phase of myocardial infarction.

BACKGROUNDAfter acute myocardial infarction (AMI), several abnormalities of the autonomic control to the heart have been described. Heart rate (HR) variability has been used to explore the neural control to the heart. A low HR variability count measured 7-13 days after AMI is significantly related to a poor outcome. Little information is available on HR variability early after AMI and its relation to clinical and hemodynamic data.METHODS AND RESULTSWe studied 54 consecutive patients (42 men and 12 women; mean age, 60.4 +/- 11 years) with evidence of AMI by collecting the 24-hour HR SD from Holter tapes recorded on day 2 or 3. We also measured HR variability in 15 patients with unstable angina and in 35 age-matched normal subjects. HR variability was lower in AMI than in unstable angina patients (57.6 +/- 21.3 versus 92 +/- 19 msec; p less than 0.001) and controls (105 +/- 12 msec; p less than 0.001). Also, HR variability was greater in non-Q-wave than in Q-wave AMI (p less than 0.0001) and in recombinant ...