Background: Prompt identification of higher risk patients presenting with ST-elevation myocardial infarction (STEMI) and undergoing primary percutaneous coronary intervention will allow a more assertive strategy and approach.
Aim: To evaluate the modified shock index (MSI) - a ratio of heart rate (HR) to mean blood pressure (MAP), as a predictor of in hospital and 6-month mortality among patients (pts) admitted with STEMI.
Methods: We analyzed retrospectively 2389 pts admitted consecutively in our coronary care unit with acute coronary syndrome, from July of 2009 to June 2014 and we selected those who presented with STEMI (n=1140). They were divided in two groups: group 1 – pts with MSI <1.3, n=1076, 94.4%); group 2 – pts with MSI ≥1.3 (n=64, 5.6%). For each group we compared clinical and laboratory features and adverse events. Primary endpoint was the occurrence of death at 6 months; follow-up was completed in 99% of patients.
Results: Patients of group 2 were older (62±14 vs 67±14; p=0.003), more frequent women (19% vs 37.5%; p1 (18.0% vs 56.3%; p<0.001), Killip=4 (2.9% vs 28.1%; p<0.001), anaemia (20.9% vs 48.4%; p<0.001) and renal insufficiency (eGFR<60 ml/min) (21.8% vs 42.6%; p<0,001). They also presented more severe coronary disease - left main coronary artery or 3 vessels disease (16.3% vs 31.3%; p=0.005) and higher prevalence of moderate to severe systolic dysfunction (48.3% vs 68.9%; p=0.009). They required more often aminergic support (7.4% vs 50%; p<0.001), intra-aortic balloon pump (2.9% vs 38.3%; p<0.001) and mechanical ventilation (2.6% vs 17.4%; p<0.001). They also had higher prevalence of malignant arrhythmias (6.1% vs 15.6%; p= 0.008) and mechanical complications (1.7 vs 6.3%; p=0.031). Compared with 1st group, the 2nd group had 6.42 times higher in hospital mortality [OR 6.42; 95% CI (4.07 – 12.67)]; p <0.001] and 7.18 times higher 6-month mortality [OR 7.18; 95% CI (3.30 - 12.46)]; p <0.001]. After adjusting for different baseline characteristics in multivariate analysis, MSI ≥1.3 remained as independent predictor of overall 6-month mortality [OR 3.81, 95% CI (1.81-8.03), p<0.001].
Conclusion: Modified shock index ≥1.3 is a stronger predictor of in hospital and 6 month mortality among patients with STEMI
