Myocardial perfusion in real-time using power modulation: In vivo evidence for microcirculatory damage after acute myocardial infarction

Background and objectives: In addition to the myocardium, the microvasculature may be also damaged in acute myocardial infarction. The aim was to evaluate the capability of myocardial contrast echocardiography in the detection of microvasculature damage after myocardial infarction. Patients and methods: Twelve patients with recent acute myocardial infarction and five control subjects with normal coronary arteries and without history of myocardial infarction were studied. Myocardial contrast echocardiography with power modulation was performed, and quantitative data were measured off-line. Power modulation uses a combination of low (0.1) and high (1.7) mechanical indexes, allowing a real-time evaluation of myocardial perfusion. Contrast agent was administered as a 3-min bolus. The quantitative analysis was performed off-line by a different blinded investigator. The refilling velocity was calculated as the difference between the peak myocardial refilling value and the value at 1 s after the impulse divided by the time from the first second after the impulse to the peak refilling value. Results: Eighty-one myocardial segments (75%) were analysed qualitatively and quantitatively in AMI patients, and 18 (60%) in control subjects (P=NS). The peak refilling intensity was not significantly different in patients and control subjects (6.62±5.85 vs. 7.53±4.06 dB, respectively). However, time to peak refilling intensity was significantly longer (5.25±1.57 vs. 4.00±0.53, P=0.004) and the velocity of refilling was significantly lower (2.74±5.34 vs. 6.58±8.02, P=0.028) in patients with myocardial infarction. Conclusion: There is microvasculature damage after myocardial infarction that is reflected as a delayed velocity of refilling in myocardial contrast echocardiography.