Heart Rate Variability after Acute Myocardial Infarction

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.

A Relation between Transient Myocardial Ischemia and Ventricular Arrhythmias on Holter Monitoring after Acute Myocardial Infarction

BACKGROUND: Transient myocardial ischemia that is recorded on Holter monitoring after a myocardial infarction is known to be a risk factor of myocardial reinfarction or death. However, it is still uncertain whether transient myocardial ischemia is a cause of ventricular arrhythmias or is simply an indicator of severe coronary artery disease. Therefore, we have studied the relation of ventricular arrhythmias to transient myocardial ischemia detected on Holter monitoring after a myocardial infarction. METHOD: We studied 40 patients with acute myocardial infarction who were performed Holter monitoring, 7 to 14 days after an attack. On Holter monitoring, we analyzed the prevalence, characteristics of transient myocardial ischemia and its relation to ventricular arrhythmias. RESULTS: 1) Among 40 patients(32 men, 8 women, mean age 53+/-13), transient myocardial ischemia was recorded in 13 patients(33%). ST elevation was observed in 2 patients, and ST depression, in 11 patients. Total episodes of transient myocardial ischemia were 65, of which only one episode was accompanied by chest pain, and total daily episodes were 4.8+/-1.4. Total daily duration of transient myocardial ischemia was 61.4+/-15.5 minutes and the duration of each transient myocardial ischemia was 15.8+/-2.1 minutes. 2) There were no significant differences in frequencies of single ventricular premature beast, bigeminy, trigeminy, ventricular couplets, and ventricular tachycardias between two groups with and without transient myocardial ischemia. CONCLUSION: It is concluded that transient myocardial ischemia on Holter monitoring after myocardial infarction is not a cause of ventricular arrhythmias.