Force-interval relationship predicts mortality in survivors of myocardial infarction with atrial fibrillation

Background: RR interval variations lead to beat-to-beat blood pressure differences through the myocardial force-interval relationship (FIR). In sinus rhythm, an altered FIR leads to post-extrasystolic potentiation (PESP) of systolic blood pressure, which has been shown to predict adverse outcome in survivors of acute myocardial infarction (MI). The purpose of this study was (1) to develop a parameter to assess the FIR in patients with atrial fibrillation (AF) and (2) to investigate its association with mortality in MI survivors suffering from AF. Methods and results: Thirty-two patients with acute MI and AF underwent 30-min recordings of ECG and continuous blood pressure. Episodes of a short RR interval (< 80% of mean interval, RR_i) preceding a long interval (> 140%, RR_{i + 1}) were identified. The systolic pressures of the pulse waves following RR_i and RR_{i + 1} were labeled P_i and P_{i + 1}. PESP_Afib was calculated as (P_{i + 1} - P_i) / (RR_{i + 1} - RR_i). During 5 years of follow-up, 13 patients died. When PESP_Afib was dichotomized at the median, mortality rates were 63% and 19% in patients with high and low PESP_Afib. Hazard ratio for mortality was 4.88 for patients with high PESP_Afib (1.33-17.84, p = 0.004). The association of PESP_Afib and mortality was independent from LVEF, age, diabetes mellitus or mean heart rate. Conclusions: PESP_Afib, a measure for the FIR in patients with AF, can be derived from simultaneous ECG and blood pressure recordings. The results of this pilot study indicate that PESP_Afib may be useful to predict adverse outcome in survivors of myocardial infarction suffering from AF. 2015 Elsevier Ireland Ltd. All rights reserved.