A total of 221 patients with NSTEMI were included, out of which 76.9% (170) were male and mean age was 57.63 ± 10.48 years with 20.4% (45) above 60 years of age. A majority (84.6%) of patients were in killip class I at presentation and only 2.7% (6) patients were in killip class III and no patients was in killip class IV. The commonest co-morbid condition was hypertension (82.4%) followed by diabetes (41.6%) and smoking (26.2%). Sedentary lifestyle was reported by 24.9% (55) of the patients. The most frequent finding on presentation ECG was ST depression – anterior (27.6%) followed by T wave inversion – anterior (14%), 12.2% (27) patient had non-specific changes, and 16.3% (36) patients had normal ECG. Median troponin I at presentation was 3.2 ng/dL [7.3 - 1.2 ng/dL] ranging over 0.06 to 50 ng/dL. Median ejection fraction was 45% [55 – 35%] with range of 15 to 70%. Demographic characteristics, baseline troponin I level, ECG changes, echocardiographic findings are presented in Table 1.
Distribution of troponin I by various ECG changes are presented in Figure 1. Proportion of patients in 4th quartile (>7.30 ng/dL) was more prominent for the patients with baseline ECG findings of poor R-wave, ST depression – generalized, and ST-depression inferior, while, lower quartile distribution of troponin I was more commonly observed with non-specific ECG changes, normal ECG, T-wave inversion – inferior, ST-depression lateral, and ST-depression – anterior.
Distribution of ejection fraction by various ECG changes are presented in Figure 2. Poor LVEF (%) can be seen with ECG finding of Afib, poor R-wave, ST-depression – anterior, and ST-depression inferior. LEVF was in normal range for most of the patients with normal ECG and ST-depression –lateral.
Correlation between troponin I and left ventricular ejection fraction against various ECG changes are presented in Figure 3. High troponin I levels and low LVEF was found to be related with ECG changes of ST-depression – generalized, poor R-wave, and Afib. While, low troponin I levels and high LVEF were observed against ECG changes of ST-depression – lateral, T-wave inversion – anterior, - inferior, and –lateral, Wellens sign, and normal ECG.
Adverse cardiac event rate at 6-months for various ECG changes, troponin I quartiles, and ejection fraction categories are presented in Table 2. Overall all-cause mortality rate at 6-months was observed to be 8.6%, re-infarction rate of 5%, re-hospitalization in 16.3%, and heart failure rate of 25.3% was observed. All-cause mortality rate was relatively higher for patients with baseline ECG findings of Afib, ST-depression – generalized, poor R-wave, Wellens sign, and T-wave inversion – inferior also mortality rate was relatively higher among patients with poor (<30%) LVEF. The relationship between mortality rate and troponin I level is non-conclusive.
Re-infarction rate was also relatively higher for the patients with ECG findings of Afib, Wellens sign, and ST-depression generalized. Re-infarction rates are surprisingly tends to remain higher for lower quartile of troponin I. Poor LVEF was also observed to be associated with higher re-infarction rate. Heart failure rate was observed to be related to poor LVEF and baseline ECG findings of Afib, ST-depression – generalized, poor R-wave, T-wave inversion inferior. However, relationship of troponin I and heart failure rate remain in-conclusive.