Estimation of infarct size using transthoracic Doppler echocardiographic measurement of coronary flow reserve in infarct related and reference coronary artery

Background: Patients in chronic phase of myocardial infarction (MI) have decreased coronary flow reserve (CFR) in infarct related artery (IRA) that is proportional to the extent of microvascular/myocardial damage. We proposed a novel model for the assessment of microvascular damage and infarct size using Doppler echocardiography evaluation of CFRs of the IRA (LAD) and reference artery (RCA). Methods: Our study included 34 consecutive patients (28 men, mean age 50 ± 11 years) with first anterior STEMI and single vessel disease successfully treated with primary PCI. All patients underwent SPECT MPI for the assessment of infarct size (expressed as a percentage of myocardium with fixed perfusion abnormalities) and CFR evaluation of LAD and RCA. CFR derived percentage of microvascular damage (CFR PMD) was calculated as: CFR PMD = (CFR RCA ― CFR LAD)/(CFR RCA ― 1) × 100 (%). Results: CFR PMD correlated significantly with all parameters evaluating the severity of myocardial damage including: peak CK activity (r = 0.632, p<0.001), WMSI (r = 0.857, p<0.001), ejection fraction (r = ―0.820, p<0.001), left ventricular end diastolic (r = 0.757, p<0.001) and end systolic volume (r = 0.794, p<0.001). Most importantly, CFR PMD (22 ± 17%) correlated significantly with infarct size by SPECT MPI (21 ±17%) (r = 0.874, p<0.001). Conclusions: CFR PMD derived from the proposed model was significantly related to echocardiographic and enzymatic parameters of infarct size, as well as to myocardial damage assessed by SPECT MPI in patients with successfully reperfused first anterior STEMI.