Fiabilidad de los índices de viabilidad miocárdica por resonancia magnética para predecir la mejoría de la función sistólica en pacientes con un primer infarto reciente y arteria abierta

P2Y12 antagonists and cardiac repair post-myocardial infarction: global and regional heart function analysis and molecular assessments in pigs

Aims

P2Y12 antagonists are the standard in antiplatelet therapy but their potential effects on functional myocardial recovery and cardioprotection post-myocardial infarction (MI) are unknown. We investigated in a preclinical model of MI whether ticagrelor and clopidogrel differently affect cardiac repair post-MI.

Methods and results

Pigs either received: (i) clopidogrel (600 mg; 75 mg/qd); (ii) ticagrelor (180 mg; 90 mg/bid); and (iii) placebo control. MI was induced by mid-left anterior descending coronary artery balloon occlusion (60 min) and animals received the maintenance doses for the following 42 days. Serial cardiac magnetic resonance was performed at Day 3 and Day 42 for the assessment of global and regional cardiac parameters. We determined cardiac AMP-activated protein kinase (AMPK), Akt/PKB, aquaporin-4, vascular density, and fibrosis. In comparison to controls, both P2Y12 antagonists limited infarct expansion at Day 3, although ticagrelor induced a further 5% reduction (P < 0.05 vs. clopidogrel) whereas oedema was only reduced by ticagrelor (≈23% P < 0.05). Scar size decreased at Day 42 in ticagrelor-treated pigs vs. controls but not in clopidogrel-treated pigs. Left ventricular ejection fraction was higher 3 days post-MI in ticagrelor-treated pigs and persisted up to Day 42 (P < 0.05 vs. post-MI). Regional analysis revealed that control and clopidogrel-treated pigs had severe and extensive wall motion abnormalities in the jeopardized myocardium and a reduced myocardial viability that was not as evident in ticagrelor-treated pigs (χ2P < 0.05 vs. ticagrelor). Only ticagrelor enhanced myocardial AMPK and Akt/PKB activation and reduced aquaporin-4 levels (P < 0.05 vs. control and clopidogrel). No differences were observed in vessel density and fibrosis markers among groups.

Conclusions

Ticagrelor is more efficient than clopidogrel in attenuating myocardial structural and functional alterations post-MI and in improving cardiac healing. These benefits are associated with persistent AMPK and Akt/PKB activation.

Cardiac magnetic resonance evaluation of edema after ST-elevation acute myocardial infarction

INTRODUCTION AND OBJECTIVES

The aims of the study were to characterize myocardial edema after ST-elevation acute myocardial infarction using cardiac magnetic resonance imaging and to investigate its impact on ventricular function and its subsequent evolution.

METHODS

In total, 134 patients admitted to hospital for a first ST-elevation myocardial infarction who had a patent infarct-related artery underwent cardiac magnetic resonance imaging. Cine images (at rest and with low-dose dobutamine) and edema, perfusion and viability images were acquired. Imaging was repeated after 6 months.

RESULTS

In the first week after infarction, edema was detected in at least one segment in 96.6% of patients (4+/-2.1 segments per patient). Extensive edema (> or = 4 segments) was associated with large ventricular end-diastolic and end-systolic volumes (P< .0001), a small left ventricular ejection fraction at rest (P=.001) and with low-dose dobutamine (P=.006), a large number of segments showing hypoperfusion (P=.001) or microvascular obstruction (P=.009), a more extensive infarct (P=.017) and greater transmural extent of the infarct (P=.003). The association between the presence and extent of edema during the first week and functional, perfusion and viability variables was still observable after 6 months. No patient exhibited edema at 6 months.

CONCLUSIONS

Cardiac magnetic resonance imaging was useful for characterizing the myocardial edema that occurred after ST-elevation acute myocardial infarction. Extensive edema was associated with poor left ventricular characteristics. Edema was a transitory phenomenon that vanished within 6 months.

Usefulness of a Comprehensive Cardiovascular Magnetic Resonance Imaging Assessment for Predicting Recovery of Left Ventricular Wall Motion in the Setting of Myocardial Stunning

OBJECTIVES

We sought to evaluate the usefulness of a comprehensive assessment of four cardiovascular magnetic resonance imaging (CMR)-derived myocardial viability indexes in the setting of myocardial stunning.

BACKGROUND

Cardiovascular magnetic resonance imaging allows the simultaneous assessment of several viability indexes.

METHODS

We studied 40 patients with a first ST-segment elevation myocardial infarction (MI) and an open infarct-related artery. At the first week, using CMR, wall motion (WM), and four viability indexes were determined: wall thickness, WM improvement with low-dose dobutamine, perfusion, and transmural extent of necrosis. We created a comprehensive score based on the presence and the relative power of these viability indexes for predicting normal WM at the sixth month.

RESULTS

Of 153 dysfunctional segments at the first week, 59 (39%) exhibited normal WM at the sixth month. According to the odds ratio of viability indexes for predicting normal WM, we developed a five-level predictive score. The proportions of segments showing normal WM at sixth month were as follows; Level 1 (0 indexes): 0 of 13 (0%); Level 2 (normal thickness and/or perfusion): 14 of 82 (17%); Level 3 (dobutamine response): 5 of 11 (45%); Level 4 (non-transmural necrosis): 20 of 26 (77%); Level 5 (non-transmural necrosis and dobutamine response): 20 of 21 (95%), p < 0.0001 for the trend. These proportions were similar in a matched prospective validation group comprising 16 patients (0%, 18%, 62%, 77%, and 90% for levels 1 to 5, respectively, p < 0.0001 for the trend).

CONCLUSIONS

A comprehensive analysis of the four more widely used CMR-derived viability indexes is useful for predicting late systolic function after myocardial infarction.