Aims: It is as yet undefined whether simple indexes of autonomic balance such as heart rate (HR) may play a role in risk stratification in patients with acute myocardial infarction (MI). The aim of this study was to quantify the prognostic significance of HR from the surface ECG obtained both at entry and at discharge, in a large population of patients all treated with fibrinolysis during the acute phase and having confirmed acute MI.
Methods and results: Surface ECGs obtained at entry and at discharge in patients with confirmed MI enrolled in the GISSI-2 study, a large multicentre trial of different thrombolytic agents, were retrieved. Heart rhythm was evaluated and HR was measured; these data were then added to the main database of GISSI-2 allowing a complete evaluation of the prognostic significance of HR. Patients not in sinus rhythm or with grade 2-3 atrioventricular block were excluded. The prognostic significance of HR (cut-offs predefined at 60, 80, 100 beats.min-1) at entry for in-hospital mortality and at discharge for 6-month mortality was evaluated in the general population and in predefined subgroups. Multivariate analyses were used to assess the independent prognostic value of HR. A total of 8915 patients (more than 70% of the original population) were suitable for the analysis. There was a progressive increase in mortality with increasing HR in the general population (from 7.1% for HR < 60 beats.min-1) to 23.4% for HR > 100 beats.min-1) and in the predefined subgroups. Multivariate analysis showed that HR exerted an independent prognostic significance. Data for analysis of HR at discharge were available for 7831 patients. Consistent with the data observed at entry, a progressive increase of 6-month mortality with increasing HR was present in the general population (from 0.8% for HR < 60 beats.min-1) to 14.3% for HR > 100 beats.min-1) and for the different predefined subgroups. Multivariate analysis confirmed the independent prognostic significance of HR. There was no relation between HR and the incidence of fatal and non-fatal reinfarction.
Conclusion: The present study indicates that HR values from a standard 12-lead ECG independently predict mortality in patients with acute MI during the in-hospital phase and after discharge. This simple index appears very useful for risk stratification in clinical practice.