Prognostic role of heart rate variability in patients with a recent acute myocardial infarction.

A low heart rate variability (HRV) has been shown to be a powerful predictor of cardiac events in patients surviving an acute myocardial infarction (MI), but it is not clear yet which among the HRV parameters has the best predictive value. Time domain and frequency domain HRV was assessed on 24-hour predischarge Holter recording of 239 patients with a recent MI. Patients were followed up for 6 to 54 months (median 28), during which 26 deaths (11%) occurred, 19 of which were cardiac in origin and 12 were sudden. Most HRVs did not show any difference between patients with or without mortality end points, but the average low-frequency and low-frequency/high-frequency ratio was lower in patients with events. However, when dichotomized according to cut points that maximized the risk of sudden death, several HRVs were significantly predictive of clinical end points. Overall, the mean of the standard deviations of all RR intervals for all 5-minute segments and the standard deviation of the mean RR intervals for all 5-minute segments were the time domain variables most significantly associated with mortality end points, whereas very low frequency was the most predictive frequency domain variable. Compared with the best time domain variables, very low frequency showed a better sensitivity (0.27 to 0.42 vs 0.19 to 0.33) for end points with only a small loss in specificity (0.92 vs 0.96). On multivariate Cox proportional analysis, a left ventricular ejection fraction <40% and a number of ventricular premature beats > or = 10/hour were the most powerful independent predictors for all end points, whereas no HRV was independently associated with the events. A low frequency/high frequency ratio < 1.05 only had a borderline association with sudden death (RR = 2.86, p = 0.076). Our data show a strong association between HRV and mortality in patients surviving a recent MI, with a slight better sensitivity of frequency domain analysis. In our study, however, HRV did not add independent prognostic information to more classic prognostic variables (e.g., left ventricular function and ventricular arrhythmias).

[Atherosclerosis and simvastatin: new questions for the new millennium]. / Aterosclerosi e simvastatina: nuovi interrogativi per il nuovo millennio.

Coronary artery disease is still associated with high morbidity and mortality in Western countries. Lipid blood levels have a tight correlation with the risk of coronary events, and the results of many trials on lipid-lowering therapy (and particularly on simvastatin) demonstrated a significant reduction in total and cardiac mortality, and in the incidence of myocardial infarction and coronary events; even the progression of coronary stenosis has been reduced by treatment with statins. Beyond cholesterol reduction, simvastatin exerts many favorable effects on endothelial function, inflammatory activity, expression of pro-thrombotic factors and oxidative stress, yielding a rational basis for its important clinical positive effects, both in primary and secondary prevention of coronary disease. Future developments, which are the subjects of many planned or ongoing clinical trials, are related to the treatment of high-risk patients, the evaluation of the efficacy of elevated simvastatin dosages and of a deep reduction in cholesterol blood levels, the interaction between simvastatin and other drugs (antioxidant compounds, vitamins, antiplatelet drugs) or interventional procedures (percutaneous transluminal coronary angioplasty). Particularly, the Heart Protection Study, the A to Z trial, and the SEARCH and SMART studies will provide important data on a wider, earlier and greater use of simvastatin, which has been demonstrated effective both in the prevention and treatment of acute coronary syndromes.

Diagnostic and prognostic value of ST segment depression limited to the recovery phase of exercise stress test.

OBJECTIVES: To investigate the diagnostic and prognostic value of ST segment depression limited to the recovery phase of an exercise stress test, as compared with that of ST segment depression appearing during exercise. SETTING: Exercise stress test laboratory of a university hospital. PATIENTS AND DESIGN: Clinical and angiographic data were compared for 574 consecutive patients who developed ST segment depression during the active phase of an exercise test (group 1) and for 79 patients who developed ST segment depression only during the recovery phase of the exercise test (group 2). RESULTS: There were no differences between the two groups in major clinical features. Significant coronary artery stenoses were found in 488 group 1 patients (85%) and in 62 group 2 patients (78%, p = 0.14). Three vessel or left main disease was found in 166 (29%) group 1 and in 14 (18%) group 2 patients (p = 0.045). At a median follow up of 55.3 months of 321 group 1 and 54 group 2 patients, there were no significant differences in major cardiac events between the groups (univariate relative risk 0.81, 95% confidence interval 0.25 to 2.68, p = 0.72). CONCLUSION: The diagnostic and prognostic power of ST segment depression limited to the recovery phase of an exercise test is largely similar to that of ST segment depression induced during effort; thus, assessing ST segment depression during recovery can significantly improve the clinical information derived from exercise stress tests.