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QRS scores correlate well with the final infarct size and post MI left ventricular function .Tc99m-Sistamibi scan, despite the radiation hazard , is the gold standard for assessing the infarction size before and after reperfusion and it is considered a reliable method for assess myocardial salvage.
To assess the ability of modified Selvester QRS score to predict myocardial salvage index measured by Tc99m-Sestamibi scan in patients with acute ST-elevation myocardial infarction after primary coronary intervention.
Thirty patients presented to by acute STEMI, eligible for reperfusion therapy, underwent primary PCI after injection of Tc-99m sestamibi then within 6 hours the 1st SPECT image was take (myocardium at risk). A follow up SPECT image was taken before discharge (final infarction size) and the myocardial salvage index was calculated. Modified Selvester QRS score (based on 37 criteria capable of generating a total of 29 points) was calculated on admission ECG and 90 minutes after primary PCI.
The modified Sylvester QRS score calculated before 1yr PCI significantly correlated with myocardium at risk (r = 0.737, P<0.0001), and modified Sylvester QRS score calculated after 1ry PCI also significantly correlated with final infarction size (r = 0.641, P=0.0001) The percent of change in QRS score from before to after the procedure significantly correlated significantly with the myocardial salvage index (r = 0.764, P<0.0001). Multiple regression analysis showed that post procedure TIMI flow grade and changes in QRS score are independent predictors of myocardial salvage index (P = 0.03, <0.0001 respectively), while the QRS score before procedure, anterior location of the infarction and the presence of diabetes are independent predictors of the myocardium at risk (p = 0.0001, 0.0001, 0.036 respectively), and the QRS score after procedure, anterior location of the infarction and post procedure TIMI flow grade are independent predictors for the final size of infarction(p = 0.001, 0.021, 0.041 respectively). Receiver-operating characteristic (ROC) curve analysis for the value of change in QRS score in prediction of myocardial salvage revealed a sensitivity and specificity of 88.89% and 66.67% respectively, a positive predictive value and a negative predictive value of 96% and 40% respectively.
The percent of change in modified Selvester QRS score before and after 1ry PCI in patients with acute STEMI significantly correlated with the myocardial salvage index measured by Tc99m scan.