Left ventricular dysfunction during dobutamine stress echocardiography in patients with syndrome X and positive myocardial perfusion scintigraphy.

Aims: A sizeable proportion of patients with angina, angiographically smooth coronary arteries and positive exercise test (syndrome X) have stress/rest myocardial perfusion defects. The aim of the study was to assess whether perfusion defects are dependent upon a reduction in coronary flow reserve causing regional left ventricular dysfunction in syndrome X patients.
Methods and Results: Twenty-two syndrome X patients underwent dobutamine stress echocardiography (DSE). All had stress-induced perfusion defects documented by 99m-Tc-MIBI scintigraphy. Resting and peak DSE wall motion score index (WMSI) were evaluated. Six patients exhibited resting wall motion abnormalities in 10 segments (WMSI 1.05 +/- 0.11). DSE was positive in 12 patients (53%), in whom 16 myocardial segments were involved: of these, 12 were normokinetic and 4 hypokinetic at rest. Peak WMSI was 1.17 +/- 0.17 (p < 0.05 vs rest). Of the 12 patients with a positive DSE, 9 also showed diagnostic ECG changes and 6 complained of angina. Of the 10 patients with negative DSE, 5 had angina and 5 (one with angina) showed ECG changes. In 7 patients (7 segments) (32%), the location of dobutamine-induced wall motion abnormalities coincided with the area where exercise-induced hypoperfusion was observed with MIBI.
Conclusions: More than a half of syndrome X patients with myocardial perfusion abnormalities also develop regional LV dysfunction during DSE. However, the site of perfusion defects and wall motion abnormalities can be different. Reversible ischemia, defined as a parallel limitation of flow reserve and inducible dysfunction, could be identified as the cause of chest pain in almost one-third of patients.