Prediction of viability with harmonic integrated backscatter in patients with acute myocardial infarction

We examined if tissue harmonic imaging contributes to integrated backscatter (IB) analysis for assessment of myocardial viability after reperfusion therapy. We studied 20 patients with first acute myocardial infarction. Short-axis IB images were recorded 3 days after reperfusion with both fundamental imaging (3 MHz central frequency) and second harmonic imaging (4.2 MHz receive) using 2-D format IB system (Hewlett Packard SONOS-5500). The cardiac cycle-dependent variation (CV) of IB in the risk area was analyzed and was defined to be positive when the magnitude of CV was more than 3 dB and nadir of CV was in end-systole. Risk area was considered viable when improvement of regional wall motion was observed at follow-up echocardiography 1 month later. The presence of CV on day-3 after reperfusion was used to predict myocardial viability. Results: Risk area was viable in 12 and not viable in 8 of 20 pts as assessed with wall motion recovery in the chronic stage. CV was positive in 8 pts (40%) assessed with fundamental IB and in 11 pts (55%) assessed with harmonic IB. Fundamental IB predicted myocardial viability with sensitivity of 50% and specificity of 75% using CV of 3 dB as a cut off value. In contrast, harmonic IB values provided higher sensitivity (71%) and specificity (83%) if the same cut off value was used. Fundamental IB showed many false negative cases possibly due to low signal-to-noise ratio. Conclusion: Harmonic IB is useful to detect CV more sensitively than fundamental IB and thus reduced false negative values in detecting myocardial viability.