Prolonged QT and myocardium recovery after primary PCI: a cMRI study

Background: The presence of viable stunned myocardium recovering after primary angioplasty is not easy to identify in the early phase of acute myocardial infarction (AMI) by noninvasive bed-side methods. We therefore aimed to assess whether a simple electrocardiogram parameter may be of help in identifying the presence of stunned viable myocardium recovering after reperfusion with primary angioplasty. Materials and methods: A total of 14 consecutive patients with ST-elevation AMI (STEMI) were enrolled in the study and underwent QT duration assessment after admission: the difference between QT corrected (QTc) in the ischaemic areas and QTc values in nonischaemic areas was therefore calculated and compared with the presence and the extension of viable stunned myocardium, assessed by comparing akinetic/dyskinetic areas at admission echocardiography with akinetic/dyskinetic areas and extension of scar at 6-month cardiac magnetic resonance imaging (cMRI). Results: In subjects with viable recovering myocardium, 75% had a QTc max > 440 ms (vs. 17%, P = 0·03); higher differential QTc values and smaller scar areas were found (33 ms vs. −17 ms, 14% vs. 27%, P = 0·03, 0·06 respectively). Differential QTc values > 0 were able to identify the presence of viable myocardium with an odds ratio of 35 (P < 0·05, sensitivity 88%, specificity 83%, positive predictive power 88%, negative predictive power of 83%). Differential QTc values were related to the extension of viable recovering myocardium (P < 0·001). Conclusion: Viable myocardium recovering after primary angioplasty in STEMI may be predicted by the presence of increased QTc values in ischaemic areas in comparison with nonischaemic areas.