Role of Electrophysiologic Studies, Signal‐Averaged Electrocardiography, Heart Rate Variability, T‐Wave Alternans, and Loop Recorders for Risk Stratification of Ventricular Arrhythmias

Lack of predictability at work and risk of acute myocardial infarction: an 18-year prospective study of industrial employees

OBJECTIVES

We examined whether the distinctive components of job control-decision authority, skill discretion, and predictability-were related to subsequent acute myocardial infarction (MI) events in a large population of initially heart disease-free industrial employees.

METHODS

We prospectively examined the relation between the components of job control and acute MI among private-sector industrial employees. During an 18-year follow-up, 56 fatal and 316 nonfatal events of acute MI were documented among 7663 employees with no recorded history of cardiovascular disease at baseline (i.e., 1986).

RESULTS

After adjustment for demographics, psychological distress, prevalent medical conditions, lifestyle risk factors, and socioeconomic characteristics, low decision autonomy (P < .53) and skill discretion (P < .10) were not significantly related to subsequent acute MI. By contrast, low predictability at work was associated with elevated risk of acute MI (P = .02). This association was driven by the strong effect of predictability on acute MI among employees aged 45 to 54 years.

CONCLUSIONS

Prospective evidence suggests that low predictability at work is an important component of job control, increasing long-term risk of acute MI among middle-aged employees.

Temporal variations in microvolt T-wave alternans testing after acute myocardial infarction

BACKGROUND

Microvolt T-wave alternans (TWA) have been accepted as a tool for assessing vulnerability to ventricular tachyarrhythmias. There is lack of data concerning prospective temporal variations in TWA measurements after acute myocardial infarction (AMI). We analysed the temporal patterns of TWA in post-AMI patients.

METHODS AND RESULTS

TWA tests were performed <1 month (TWA_early) and 6 months (TWA_late) after AMI in 51 consecutive patients treated with successful percutaneous coronary intervention (PCI). Twenty seven patients (53%) had anterior wall infarctions and 24 (47%) had inferior/lateral wall infarctions. TWA was measured during a treadmill manual exercise protocol and defined as positive, negative and indeterminate. Group A included patients with TWA negative in both tests and Group B included those with TWA abnormal (positive or indeterminate) at first or second determinations. TWA_early was negative, positive and indeterminate in 38 (74.6%), 8 (15.6%) and 5 (9.8%) patients, respectively, whereas TWA_late was negative, positive and indeterminate in 30 (58.9%), 14 (27.4%) and 7 (13.7%) patients, respectively. TWA_early was classified as normal in 74.6% and abnormal in 25.4% of the cases, and TWA_late was normal in 58.9% and abnormal in 41.1%. TWA tests were concordant in 36 patients (70.6%) and discordant 15 patients (29.4%). At TWA_late, 10 patients (19.6%) changed from TWA negative to TWA abnormal and 4 patients (7.8%) from TWA abnormal to TWA negative. After TWA_early+TWA_late, 45% of the patients had 1 test classified as abnormal. Left ventricular ejection fraction was <50% in 22% of Group A and 52% of Group B (P = 0.037).

CONCLUSIONS

In the era of primary PCI, temporal changes in TWA measurements may occur frequently during the first 6 months post-AMI. These findings should be considered in risk stratification strategies following AMI.

Heart rate variability in myocardial infarction and heart failure

The need to refine the identification of patients who might benefit from implantation of an implantable cardioverter defibrillator has been risen by the results of many clinical trials on ICD therapy. Traditional parameters such as left ventricular ejection fraction and the presence of non-sustained ventricular tachycardia were not strong enough to achieve this goal with reasonable cost-effectiveness. Heart rate variability (HRV) is one of the most popular parameters used to assess the autonomic tone. HRV has been reported as a strong predictor of cardiovascular mortality. Currently, three different categories of methods in HRV analysis are being used; the time domain, frequency domain, and non-linear dynamic analysis. Both time domain and frequency domain analyses of HRV have been investigated extensively regarding their use as a prognostic marker for cardiovascular mortality. The non-linear dynamic analysis is the latest tool that has shown to have an even higher predictive value than any of the traditional parameters. However, standardized and supporting evidence on this new technique is still lacking. In this article, the current role of HRV in the prediction of cardiovascular mortality in myocardial infarction and heart failure patients has been reviewed.