Background. A sizeable proportion of ST Elevation in Myocardial Infarction (STEMI) patients treated with Primary Percutaneous Coronary Intervention (PPCI) demonstrate inadequate perfusion of the infarcted myocardium after successful restoration of epicardial coronary blood flow resulting to adverse angiographic and clinical outcomes. We sought to determine the association of ischemia grade on admission electrocardiogram (ECG) with the clinical and angiographic outcomes of patients with STEMI who will undergo PPCI.
Methods. This is a single-centre, prospective cohort study, conducted on April to December 2011 among patients presenting with acute STEMI and underwent PCI in the Philippine Heart Center. They were classified into two groups based on the absence [34 patients without Grade 3 ischemia (non-GI3)] or presence [34 patients with Grade 3 ischemia (GI3)] of distortion of the terminal portion of the QRS complex on the admission ECG (ECG Ischemia Grade). In-hospital outcomes were determined during the course of the study. It included death and a composite secondary end point comprising of heart failure, malignant arrhythmia, hemodynamic instability, and stroke.
Results. There were no significant differences in the baseline characteristics in terms of age, gender, and coronary artery risk factors between patients with GI3 and non-GI3. Myocardial infarction presenting as Killip Class 3 and 4 occurred more frequently in patients with GI3 (p=0.001) as they have Significantly lower mean systolic and diastolic blood pressures (p=0.001 and p=0.000,respectively) and unexpectedly lower use of ACE inhibitors (p=0.003). Incidence of cardiogenic shock was also higher among these patients (11 out of 12 cases) which subsequently necessitated use of IABP (p = 0.006). Baseline angiography showed that patients with GI3 had longer lesion lengths (p=0.053) and insignificantly more likely to have multivessel coronary disease and poor collateral flow to the infarct-related artery (p=0.084 and p=0.061, respectively). The incidence of pre-revascularization TIMI :5 1 in the infarct related artery (IRA) and high-burden thrombus formation was comparable between the two patient groups. Failure to gain re-flow in the IRA after PPCI occurred in 58.8% (40 patients), including a combined 39.7% with TIMI:5 2 flow and 19.1% with TIMI 3 flow but myocardial blush grade (MBG) :51. Grade 3 ischemia is associated with a higher incidence of angiographic no re-flow post- PPCI (p = 0.000). This translated to a higher in-hospital mortality among these patients compared with non-Gl3 (26.5% vs. 2.9%, p=0.013). More cardiac complications were also observed in patients with GI3 than did those withnon-GI3, particularly heart failure (p = 0.000), malignant arrhythmia (p=0.000),hemodynamic instability (p = 0.000),and stroke (p=0.001).
Conclusion. ECG ischemia grade on admission can be a predictive tool of adverse clinical and angiographic outcomes associated with abnormalities of myocardial reperfusion. It is possible that patients with GI3 who will undergo PPCI will benefit further if angiographic no re-flow can be prevented and treated.