Introduction: Electrocardiogram (ECG) is the simplest tool for diagnosing ST Elevation Myocardial Infarction (STEMI). We can use a12 lead ECG for prognostication purposes also.
Aim: The aim of the study was to find out the role of ECG as a prognostic marker in terms of clinical outcome and wall motion abnormality.
Materials and methods: It was a prospective study done in PSG Institute of Medical Sciences and Research, Coimbatore, Tamil Nadu, India, from January 2014 to September 2014. Patients aged above 18 years admitted with first episode of ST EMI as per the inclusion and exclusion criteria were recruited for the study. Presence of reciprocal changes and QRS amplitude was measured from ECG. Presence of Left Ventricular Dysfunction (LVD) and wall motion score were calculated from ECG along with clinical outcome during first follow up visit. Statistical analysis was done using SPSS software. Probability was calculated using chi-square test, independent t-test and ANOVA analysis.
Results: A total of 120 patients were recruited for the study of which six were excluded based on the exclusion criteria. Among 114 patients analysed, 55 had reciprocal changes; 38 of them developed LVD which was statistically significant (p=0.002). Of the 78 patients with Anterior Wall Myocardial Infarction (AWMI), 35 had reciprocal changes; 15 (42.9%) of them had NYHA Class 1 symptoms, 14 (40%) had Class II and 4 (11%) had class III symptoms at follow up. The association was statistically significant (p=0.001). Similar statistically significant association was found in patients with Inferior Wall Myocardial Infarction (IWMI) who had reciprocal changes and NYHA symptoms at follow up (p=0.004). The mean wall motion score in patients with AWMI and reciprocal changes was 24.83 ± 4.1; whereas, without reciprocal changes was 23.98 ± 3.6; the association was not statistically significant. The mean QRS amplitude of all patients with LVD was 33.25 ±16.34. The association between QRS amplitude and LVD was not statistically significant. The overall mean wall motion score was 24.86 ± 3.91. The association between QRS amplitude and wall motion score was statistically significant (r value = 0.210). The association between QRS amplitude and wall motion score was statistically significant when we analysed AWMI (r= -0.147, p=0.199) and IWMI (r= -0.359, p=0.031) separately.
Conclusion: ECG can be used as a tool for prognostication in acute STEMI. The presence of reciprocal changes in the ECG can signify poorer outcome on follow up. Lower QRS amplitude can be used as a predictor of larger infarct.
Keywords: Coronary artery disease; Heart failure; Prognostic marker.