Prediction of SYNTAX score Ⅱ improvement by temporal heart rate changes between discharge and fist preceding visit on long-term clinical outcomes in patients with acute myocardial infarction

Background : Studies of the prognostic ability of the temporal changes in resting heart rate (ΔHR) regarding cardiovascular (CV) mortality and clinical outcomes in patients with acute myocardial infarction (AMI) are scarce. The aim of this study was to investigate the predictive value of ΔHR using models including the SYNTAX score Ⅱ (SxS-Ⅱ) on the long-term prognosis of patients with AMI. Methods : A total of 605 AMI subjects with vital signs recorded at the first outpatient visit (2–4 weeks after discharge) was retrospectively recruited into this study. The changes between discharge and outpatient resting heart rate (D-O ΔHR) were calculated by subtracting the HR at first post-discharge visit from the value recorded at discharge. The major adverse cardiovascular events (MACE) were cardiovascular death, recurrent myocardial infarction, revascularization, and nonfatal stroke. The predictive values and reclassification ability of the different models were assessed using a likelihood ratio test, Akaike’s information criteria (AIC), receiver operating characteristic (ROC) curves, net reclassification improvement (NRI), and integrated discrimination improvement (IDI). Results : During the follow-up period, the D-O ΔHR was independently associated with CV mortality [hazards ratio (HR) = 0.97, 95% CI = 0.958–0.985, P < 0.001] and MACE (HR = 1.02, 95% CI = 1.011–1.039, p = 0.001). The likelihood test indicated that the combined model of SxS-Ⅱ and D-O ΔHR yielded the lowest AIC regarding MACE and CV death ( P < 0.001). Moreover, D-O ΔHR alone significantly improved the net reclassification and integrated discrimination of the models containing SxS-Ⅱ regarding both CV mortality and MACE (CV mortality: NRI = 0.5600, P = 0.001 and IDI = 0.0759, P = 0.03; MACE: NRI = 0.2231, P < 0.05 and IDI = 0.0107, P < 0.05). Conclusions : The D-O ΔHR was an independent predictor of long-term CV mortality and MACE. The additive value of D-O ΔHR combined with SxS-Ⅱ could significantly enhance its predictive probability.