Impact of the coronary flow reduction at rest on myocardial perfusion and functional indices derived from myocardial contrast and strain echocardiography.

Background: The severity of the coronary flow reduction that corresponds to myocardial perfusion and functional abnormalities remains unclear. We estimated the impact of various severities of flow-limiting coronary stenosis at rest on myocardial perfusion and functional indices from myocardial contrast echocardiography and tissue strain imaging and characterized the relationship between both the indices.

Methods: Four levels of flow-limiting stenoses (slight, mild, moderate, severe) of the left circumflex coronary artery were examined in 10 open-chest dogs. In the left circumflex coronary artery area, plateau videointensity and time to plateau (TP) of the replenishment curve from myocardial contrast echocardiography were calculated for perfusion analysis, and peak systolic strain and postsystolic strain index (PSI) from tissue strain imaging were measured for functional analysis.

Results: Plateau videointensity and peak systolic strain tended to decrease with increased severity of stenosis, although these differences did not reach the level of statistical significance. TP and PSI were significantly increased in the context of moderate (>or=30-<50%) and severe (>or=50%) flow reduction when compared to baseline values (TP, moderate 1.69 +/- 0.20 and severe 1.77 +/- 0.25 vs baseline 0.93 +/- 0.17, P < .01, respectively; PSI, moderate 0.96 +/- 0.15 and severe 1.28 +/- 0.32 vs baseline 0.59 +/- 0.18, P < .05 and P < .01, respectively). Further, TP and PSI were positively correlated with flow reduction (r = 0.81 and r = 0.84, P < .0001, respectively), and PSI was positively correlated with TP (r = 0.72, P < .0001).

Conclusions: In contrast to conventional indices, such as plateau videointensity and peak systolic strain, novel indices, such as TP and PSI, were both able to detect 30% or greater coronary flow reduction at rest.