Heart Rate Variability after Acute Myocardial Infarction

ABSTRACT

BACKGROUND: Several abnormalities of the autonomic regulation of the heart have been noted after acute myocardial infarction(AMI). Measurement of heart rate(HR) variability has been reported to provide indirect, noninvasive estimate of the cardiac efferent parasympathetic activity. The purposes of this study were to get the information on heart rate variability after AMI and to determine its relation to clinical and hemodynamic data. METHODS: We measured HR variability in 28 patients(23 men and 5 women mean age, 56.6+/-10.4 years) 3-15days after AMI, in 25 patients with unstable angina and in 21 normal subjects by using triangular interpolation of the frequency distribution histogram om normalto-normal RR intervals from Holter tapes. RESULTS: HR variability was lower in AMI than unstable angina patients(357.9+/-118.6 versus 426.1+/-122.5 msec p<0.05) and normal subjects(525.1+/-137.4 msec p<0.025). There was no difference for infarct site, thrombolytic therapy, presence of Q-wave. HR variability was significantly related to mean 24-hour HR, left ventricular ejection fraction(all p<0.0001), left ventricular end diastolic diameter(p<0.05). HR varability was lower in patients belonging to Killip class 2-4 and who reqired the use of diuretics or digitalis(all p<0.05). CONCLUSION: After AMI, HR variabillity was reduced and significantly related to clinical and hemodynamic indexes of severity. Measurement of HR variability early after AMI may offer important clinical information for the early high stratification of patients.