Coronary Wave Energy: A Novel Predictor of Functional Recovery After Myocardial Infarction

Study Questions:

What is the predictive ability of early wave intensity analysis-derived microcirculatory (backward) expansion wave energy in detecting late viability, as defined by functional recovery?

Methods:

Thirty-one patients (58 ± 11 years) were enrolled after non–ST-segment elevation myocardial infarction (NSTEMI). Regional left ventricular function and late-gadolinium enhancement were assessed by cardiac magnetic resonance imaging, before and 3 months after revascularization. The backward-traveling (microcirculatory) expansion wave was derived from wave intensity analysis of phasic coronary pressure and velocity in the infarct-related artery, whereas mean values were used to calculate hyperemic microvascular resistance. Receiver-operator characteristic analysis was performed to determine a cutoff value with maximal diagnostic accuracy for diastolic microcirculatory wave intensity (BEW) and hMR, in predicting regional recovery in function, with the difference between the two indices assessed using the Delong receiver-operator characteristic comparison analysis.

Results:

Twelve-hour troponin T, left ventricular ejection fraction, and percentage late-gadolinium enhancement mass were 1.35 ± 1.21 µg/L, 56 ± 11%, and 8.4 ± 6.0%, respectively. The infarct-related artery backward-traveling (microcirculatory) expansion wave was inversely correlated with late-gadolinium enhancement infarct mass (r = –0.81; p < 0.0001) and strongly predicted regional left ventricular recovery (r = 0.68; p = 0.001). By receiver operating characteristic analysis, a backward-traveling (microcirculatory) expansion wave threshold of 2.8 W m–2 s–2 × 105 predicted functional recovery, with sensitivity and specificity of 0.91 and 0.82 (AUC 0.88). Hyperemic microvascular resistance correlated with late-gadolinium enhancement mass (r = 0.48; p = 0.03), but not left ventricular recovery (r = –0.34; p = 0.07).

Conclusions:

The authors concluded that the microcirculation-derived backward expansion wave is a new index that correlates with the magnitude and location of infarction, which may allow for the prediction of functional myocardial recovery.

Perspective:

This study indicates that the magnitude of the backward expansion wave energy in the infarct-related artery is strongly predictive of myocardial recovery after an NSTEMI, highlighting its potential use as an index of myocardial viability that can be obtained during cardiac catheterization. Furthermore, it appears that the backward traveling (microcirculatory) expansion wave (BEW) is reduced after acute coronary syndrome, in proportion to the magnitude of infarction. Coronary wave intensity analysis may potentially provide an accurate adjunctive method of assessing myocardial viability during cardiac catheterization after acute coronary syndrome, but additional prospective validation is needed.

Clinical Topics: Noninvasive Imaging, Magnetic Resonance Imaging

Keywords: Myocardial Infarction, Recovery of Function, Ventricular Function, Left, Gadolinium, Troponin T, Magnetic Resonance Imaging


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