We have developed a novel calibration technique applicable for myocardial contrast echocardiography (MCE). We assessed the value of this technique in the recognition of myocardial infarction (MI) and its spatial extent, and we also performed a validation study in normal subjects.
Background
The heterogeneity of contrast intensity (CI) among myocardial segments limits the clinical use of MCE.
Methods
We performed MCE with a slow-bolus injection of Levovist and recorded end-systolic harmonic power Doppler images at intervals of four heart beats in 15 normal volunteers and 30 patients with MI. We divided the left ventricular (LV) wall into 12 segments and placed the region of interest in the subendocardial region in each segment and in the adjacent LV cavity. We measured calibrated CI (dB) by subtracting the cavity CI from myocardial CI.
Results
The mean intersegmental difference in myocardial CI was 15.8 dB at baseline, whereas it was reduced to 6.3 dB after calibration (p < 0.01). Calibrated CI was higher in the kinetic segments than in the akinetic segments (−14.5 ± 2.3 dB [range −18.7 to −9.9 dB] vs. −22.5 ± 2.6 dB [−27.8 to −17.7 dB], p < 0.001), and −18.0 dB was the optimal cutoff point to discriminate these from each other. Color-coded mapping of calibrated CI may identify the spatial extent of persistently akinetic myocardium as areas of calibrated CI of ≤−18.0 dB.
Conclusions
This new calibration method reduces the intersegmental difference in CI in normal subjects. Calibrated CI provides an estimate of persistently akinetic myocardium in patients with MI, and its color-coded mapping is comprehensive and identifies the spatial extent of MI.
