الفهرس 
SUMMARY AND CONCLUSIONSOnly 14 pages are availabe for public view
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Abstract
Heart rate variability has been recently recognized as an important independent prognostic factor after an acute myocardial infarction. Survivors of acute myocardial infarction with low heart rate variability at the time of discharge have a higher mortality rate than patients with high heart rate variability. The aim of the present study was to evaluate the correlation of heart rate variability with the extent of coronary artery disease and clinical variables including electrocardiographic changes in patients with acute myocardial infarction. Twenty patients (19 males and one female) with a mean age of 52.7 ± 7.44 years admitted with acute myocardial infarction were included in the present study. In addition, 10 age-matched healthy volunteers (6 males and 4 females) with a mean age of 50.7 ± 6.88 years served as a control group. All patients were subjected to 24-hours Holter monitoring during the first 24-48 hours of admission. No patient was on beta-blockers or calcium antagonists. There was significant difference between patient group and control group as regard all HRV arameters which were lower in patient group than control group (P<0.05). We found also that there was a difference in HRV parameters between anterior infarction group and inferior infarction group as regard time domain (SDANN and PNN50) and frequency domain (LF and HF), the difference was statistically significant (P<0.05). Furthermore, patients with multivessel disease detected by coronary angiography had lower HRV parameters as regard time domain and frequency domain compared with patients with single vessel disease, the difference between the two groups was statistically significant (P<0.05). Diabetic and hypertensive patients had lower HRV parameters as regard both time domain and frequency domain compared with patients with no diabetes nor hypertension, the difference between the two groups was statistically significant (P<0.05). We found that there was a significant relationship between HRV and other variables such as EF, extent of coronary artery disease, there was a positive correlation between HRV parameters and EF, while there was a negative correlation between HRV parameters and the extent of coronary artery disease. Based on the results of the present study, it can be concluded that heart rate variability during the early phase of acute myocardial infarction is decreased and significantly related to the extent of coronary artery disease, site of infarction and other variables such as left ventricular function. The cause of the observed changes in heart rate variability during acute myocardial infarction may be reduced vagal and/or increased sympathetic outflow to the heart. It is suggested that early measurements of heart rate variability during acute myocardial infarction may offer important clinical infarction and contribute to the early risk stratification of the patients.