Findings from long-term electrocardiographic monitoring of patients with variant angina in a coronary care unit

Early assessment of heart rate variability is predictive of in-hospital death and major complications after acute myocardial infarction

BACKGROUND

Depressed heart rate variability at acute myocardial infarction discharge is associated with poor long-term prognosis. However, its early (<48 h) predictive value has not been extensively investigated. Aim of this Multicenter Italian Study was to investigate, during acute myocardial infarction, in-hospital prognostic value of heart rate variability and its short-term evolution.

METHODS

Twenty-four hour ECG monitoring was prospectively obtained on admission in 413 patients with new-onset acute myocardial infarction and repeated in 349 at discharge. Heart rate variability statistical and frequency domain indices, peak creatine kinase, echocardiographic wall motion score index and risk factors were obtained. The occurrence of cardiac death and resuscitated ventricular fibrillation were the primary end-points; cardiogenic shock, ventricular tachycardia, post-infarction angina and heart failure the secondary end-points.

RESULTS

At admission, a marked reduction in heart rate variability indices was evident. Nine patients died during hospitalization and 13 were resuscitated from ventricular fibrillation. Secondary endpoints occurred in other 91 patients. At univariate analysis, low frequencies (LF), mean time interval between consecutive heart beats (RR), wall motion score index and family history of ischemic heart disease were predictive of combined primary and secondary end-points. At multivariate analysis, only LF and family history were predictive with a relative risk of 2.01 and 1.84, respectively (P<0.003). In survivors, heart rate variability indices significantly increased during hospitalization, still remaining below reference values.

CONCLUSIONS

A depressed heart rate variability was present in the early phase of infarction and improved at discharge. LF power was an independent predictor of the combined unfavorable short-term events.

Circadian and septadian variation in the occurrence of acute myocardial infarction in a Chinese population

To investigate whether circadian or any other temporal pattern(s) exist in the occurrence of acute myocardial infarction (AMI) in a Chinese population, we analyzed 428 patients with confirmed AMI for temporal patterns of AMI occurrence. The patients admitted to the Affiliated Hospital of Shandong Medical University during 1991-95 were from Jinan, the capital city of Shandong Province of China, which has a population of 2.5 million. The chi-square test for goodness of fit was used to test the difference among the frequencies of AMI occurrence in 4 equal intervals (01.00-07.00 h, 07.00-13.00 h, 13.00-19.00 h, 19.00-01.00 h) during the day and among those on 7 days during the week. The results showed that AMI occurrence exhibited significant circadian (p<0.001) and septadian (day of the week) (p=0.046) periodicity, with a peak at 01.00-07.00 h and a trough at 13.00-19.00 h during the day, and a peak on Saturday and a trough on Wednesday during the week. The peak to trough ratio of risk was 2.7 during the day and 2.1 during the week. It is concluded that there were circadian and septadian biorhythms in AMI occurrence in the Chinese population and that these were different from those observed in Western populations. Further investigation of the underlying mechanisms may shed further light on the trigger mechanisms of AMI and thus be helpful in the prevention and treatment of AMI.