Correlation of ST changes in leads V4-V6 to area of ischemia by CMR in inferior STEMI

OBJECTIVE

We aim to determine the correlation between ST-segment changes in leads V4-V6 and the extent of myocardial injury by cardiac magnetic resonance (CMR) in patients with inferior ST elevation (STE) myocardial infarction (iSTEMI).

DESIGN

Admission electrocardiogram and CMR data from the MITOCARE trial were used. Differences in mean myocardium at risk, infarct size, ejection fraction and myocardial segment involvement by CMR were compared in patients with first iSTEMI with STE, ST depression (STD) or no ST changes (NST) in V4-V6. Myocardial segment involvement was further evaluated by comparing proportion of patients in each group with ≥25% and ≥50% segment involvement.

RESULTS

Fifty-four patients were included. Patients with STE (n = 22) and STD (n = 16) in V4-V6 had significantly lower ejection fraction compared to NST (n = 16) (48% vs 48% vs 54%, p = .02). STE showed more apical, apical lateral and mid-inferolateral involvement but less basal inferior involvement than NST. STD exhibited greater basal inferoseptal involvement compared to STE. There were more patients with STE that had ≥25% and ≥50% apical lateral involvement compared with STD and NST groups. Patients with STD were more likely to have ≥25% and ≥50% basal inferoseptal involvement compared with STE and NST groups.

CONCLUSION

Our study suggests that in iSTEMI, ST changes in the precordial leads V4-V6 correlates with greater myocardial injury and distribution of myocardium at risk.

Electrocardiographic scores of severity and acuteness of myocardial ischemia predict myocardial salvage in patients with anterior ST-segment elevation myocardial infarction

BACKGROUND

Terminal "QRS distortion" on the electrocardiogram (ECG) (based on Sclarovsky-Birnbaum's Grades of Ischemia Score) is a sign of severe ischemia, associated with adverse cardiovascular outcome in ST-segment elevation myocardial infarction (STEMI). In addition, ECG indices of the acuteness of ischemia (based on Anderson-Wilkins Acuteness Score) indicate myocardial salvage potential. We assessed whether severe ischemia with or without acute ischemia is predictive of infarct size (IS), myocardial salvage index (MSI) and left ventricular ejection fraction (LVEF) in anterior versus inferior infarct locations.

METHODS

In STEMI patients, the severity and acuteness scores were obtained from the admission ECG. Based on the ECG patients were assigned with severe or non-severe ischemia and acute or non-acute ischemia. Cardiac magnetic resonance (CMR) was performed 2-6days after primary percutaneous coronary intervention (pPCI). LVEF was measured by echocardiography 30days after pPCI.

RESULTS

ECG analysis of 85 patients with available CMR resulted in 20 (23%) cases with severe and non-acute ischemia, 43 (51%) with non-severe and non-acute ischemia, 17 (20%) with non-severe and acute ischemia, and 5 (6%) patients with severe and acute ischemia. In patients with anterior STEMI (n=35), ECG measures of severity and acuteness of ischemia identified significant and stepwise differences in myocardial damage and function. Patients with severe and non-acute ischemia had the largest IS, smallest MSI and lowest LVEF. In contrast, no difference was observed in patients with inferior STEMI (n=50).

CONCLUSIONS

The applicability of ECG indices of severity and acuteness of myocardial ischemia to estimate myocardial damage and salvage potential in STEMI patients treated with pPCI, is confined to anterior myocardial infarction.

Critical Issues for the Translation of Cardioprotection

The translation from numerous successful animal experiments on cardioprotection beyond that by reperfusion to clinical practice has to date been disappointing. Animal experiments often use reductionist approaches and are mostly performed in young and healthy animals which lack the risk factors, comorbidities, and comedications which are characteristics of patients suffering an acute myocardial infarction or undergoing cardiovascular surgery. Conceptually, it is still unclear by how much the time window for successful reperfusion is extended by preconditioning, and how long the duration of ischemia can be so that adjunct cardioprotection by postconditioning at reperfusion still protects. Experimental studies addressing long-term effects of adjunct cardioprotection beyond infarct size reduction, that is, on repair, remodeling, and mortality, are lacking. Technically, reproducibility and robustness of experimental studies are often limited. Grave faults in design and conduct of clinical trials have also substantially contributed to the failure of translation of cardioprotection to clinical practice. Cardiovascular surgery with ischemic cardioplegic arrest is only a surrogate of acute myocardial infarction and confounded by the choice of anesthesia, hypothermia, cardioplegia, and traumatic myocardial injury. Trials in patients with acute myocardial infarction have been performed on agents/interventions with no or inconsistent previous animal data and in patients who had either some reperfusion already at admission or were reperfused too late to expect any myocardial salvage. Of greatest concern is the lack of adequate phase II dosing and timing studies when rushing from promising proof-of-concept trials with surrogate end points such as infarct size to larger clinical outcome trials. Future trials must focus on interventions/agents with robust preclinical evidence, have solid phase II dosing and timing data, and recruit patients who have truly a chance to benefit from adjunct cardioprotection.