PROGNOSTIC-SIGNIFICANCE OF HEART-RATE-VARIABILITY IN POSTMYOCARDIAL INFARCTION PATIENTS IN THE FIBRINOLYTIC ERA - THE GISSI-2 RESULTS

Background Studies performed before the introduction of fibrinolysis s howed that a low heart rate variability (HRV) is associated with highe r mortality in post-myocardial infarction (MI) patient. We evaluated w hether HRV adds information relevant to risk stratification in patient s treated with fibrinolysis as well. Methods and Results From 24-hour ECG recordings obtained at discharge in patients treated with recombin ant tissue-type plasminogen activator or streptokinase, we measured se veral time-domain indexes of HRV: standard deviation (SDNN), root-mean -square of successive differences (RMSSD), and number of RR interval i ncreases > 50 ms (''NN50+''). The prognostic value of HRV for total an d cardiovascular mortality was assessed. Of 567 patients with valid re cordings, 52 (9.1%) died during the 1000 days of follow-up, 44 (7.8%) of cardiovascular causes. All indexes of low HRV were able to identify patients (16% to 18% of total population) with a higher total mortali ty (20.8% to 24.2% versus (6.0% to 6.8%, depending on index, used), Th e independent predictive value of low HRV was confirmed by the adjuste d analysis with the following relative risks: NN50+, 3.5 (95% CI, 1.9 to 6.7); SDNN, 3.0 (95% CI, 1.55 to 5.9): and RMSSD, 2.8 (95% CI, 1.5 to 5.3). Advanced age, previous MI, Killip class at entry, and use of digitalis were also independent predictors. Similar data were obtained for cardiovascular mortality. Conclusions Time-domain indexes of HRV retain their independent prognostic significance even in post-MI patie nts of all ages treated with fibrinolysis.