Incremental value of contrast myocardial perfusion to detect intermediate versus severe coronary artery stenosis during stress-echocardiography

Abstract

Background: We aimed to compare the incremental value of contrast myocardial perfusion imaging (MPI) for the detection of intermediate versus severe coronary artery stenosis during dipyridamole-atropine echocardiography (DASE).Wall motion (WM) assessment during stress-echocardiography demonstrates suboptimal sensitivity to detect coronary artery disease (CAD), particularly in patients with isolated intermediate (50%-70%) coronary stenosis.

Methods: We performed DASE with MPI in 150 patients with a suspected chest pain syndrome who were given clinical indication to coronary angiography.

Results and discussion: When CAD was defined as the presence of a >or=50% stenosis, the addition of MPI increased sensitivity (+30%) and decreased specificity (-14%), with a final increase in total diagnostic accuracy (+16%, p < 0.001). The addition of MPI data substantially increased the sensitivity to detect patients with isolated intermediate stenosis from 37% to 98% (p < 0.001); the incremental sensitivity was much lower in patients with severe stenosis, from 85% to 96% (p < 0.05), at the expense of a higher decrease in specificity and a final decrease in total diagnostic accuracy (-18%, p < 0.001).

Conclusions: The addition of MPI on top of WM analysis during DASE increases the diagnostic sensitivity to detect obstructive CAD, whatever its definition (>or=50% or > 70% stenosis), but it is mainly driven by the sensitivity increase in the intermediate group (50%-70% stenosis).The total diagnostic accuracy increased only when defining CAD as >or=50% stenosis, since in patients with severe stenosis (> 70%) the decrease in specificity is not counterbalanced by the minor sensitivity increase.

Figure 1

Stress echocardiography protocol. Abbreviations as in table 1.

Figure 2

Sensitivity, specificity and accuracy for each subgroup. Accuracy data with corresponding 95% confidence intervals for wall motion and wall motion+myocardial perfusion imaging to detect patients with coronary artery stenosis between 50% and 70%, ≥ 50%, or > 70%. In the intermediate (50%-70% stenosis) group only sensitivity can be calculated, since in this case patients with a > 70% stenosis cannot be classified, although key to specificity and accuracy measurement. In the CAD > 70% an abnormal test with angiographic 50%-70% stenosis is considered a false positive. * p < 0.001, † p < 0.05 compared to wall motion criteria.

Figure 3

Average stenosis diameter. Average stenosis diameter in patients who underwent QCA, classified into three subgroups based on SE results: MPI-/WM-, MPI+/WM-, MPI+/WM+. Abbreviations as defined in table 1.

Figure 4

Flash replenishment sequence. Assessment of myocardial perfusion after dipyridamole. From left to right: uniform transmural perfusion seen in apical 4-chamber before flash, then images taken 1, 3, 4 and 8 cardiac cycles after microbubbles destruction. Perfusion defects become apparent after flashing (flash icon in the figure) both in the anterior descending and circumflex coronary arteries perfusion territories, still detectable after 8 cycles; the patient had no clear WM abnormality, even if mild tardokinesia of the septum was suspected. Angiography confirmed obstructive two-vessel disease with both stenosis ranging between 50% and 70%. Abbreviations as defined in table 1.