Shock Index as a Predictor of Myocardial Injury in ST-segment Elevation Myocardial Infarction
Jin Kyung Hwang1, Woo Jin Jang2, Young Bin Song1
1Department of Medicine, Heart Vascular Stroke Institute, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea.
Insights
The initial shock index, a simple vital sign ratio, can predict myocardial injury in ST-elevation myocardial infarction (STEMI) patients undergoing primary percutaneous coronary intervention (PCI). A higher shock index indicates a greater risk of significant heart muscle damage.
Area of Science:
- Cardiology
- Cardiovascular Research
- Medical Diagnostics
Background:
- Limited understanding of the relationship between shock index and myocardial injury in ST-elevation myocardial infarction (STEMI) patients undergoing primary percutaneous coronary intervention (PCI).
- Shock index, calculated as heart rate divided by systolic blood pressure, is a readily available clinical metric.
Purpose of the Study:
- To investigate the association between initial shock index and myocardial infarct size in STEMI patients treated with primary PCI.
- To determine if shock index can serve as a predictor of myocardial injury in this patient population.
Main Methods:
- Analysis of cardiac magnetic resonance imaging data from 306 STEMI patients who underwent primary PCI.
- Patients were stratified into two groups based on initial shock index: >0.7 and ≤0.7.
- Myocardial infarct size was assessed as the primary endpoint.
Main Results:
- The group with an initial shock index >0.7 demonstrated significantly larger infarct sizes compared to the ≤0.7 group (22.9% vs. 19.2%, P < 0.01).
- Patients with a higher shock index also showed lower ejection fraction, elevated N-terminal prohormone of brain natriuretic peptide, higher Killip class, and increased prevalence of diabetes.
- Multivariate analysis confirmed that an initial shock index >0.7 was independently associated with large myocardial infarctions (OR = 3.02, P < 0.01).
Conclusions:
- Initial shock index is a potentially reliable and easily obtainable predictor of myocardial injury in STEMI patients undergoing primary PCI.
- This finding suggests that shock index can aid in risk stratification and early identification of patients at higher risk for extensive myocardial damage.
Background:
Little is known about the association between shock index and myocardial injury in patients with ST-segment elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PCI).
Methods:
We analyzed cardiac magnetic resonance imaging from 306 consecutive patients treated with primary PCI for STEMI. The patients were divided into the following 2 groups: initial shock index >0.7 (n = 88) and ≤0.7 (n = 218). Shock index was calculated as the ratio of heart rate to systolic blood pressure based on the first recorded vital signs upon arrival. The primary end point was myocardial infarct size.
Results:
The shock index >0.7 group, exhibited a lower baseline left ventricular ejection fraction (P = 0.01), higher N-terminal prohormone of brain natriuretic peptide level (P = 0.01), higher Killip class (P < 0.01) and higher prevalence of diabetes (P = 0.02) than the shock index ≤0.7 group. There were no significant differences in the angiographic or procedural characteristics between the 2 groups. In cardiac magnetic resonance imaging analysis, the shock index >0.7 group had a larger infarct size than did the shock index ≤0.7 group (22.9 ± 11.2% versus 19.2 ± 11.5%, P < 0.01). According to multivariate analysis, shock index >0.7 was associated with large myocardial infarctions (odds ratio = 3.02; 95% CI: 1.62-5.65; P < 0.01).
Conclusions:
Initial shock index is a potentially reliable predictor of myocardial injury in patients with STEMI undergoing primary PCI.
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