Coronary artery disease
Noninvasive Evaluation of Flow Reserve in the Left Anterior Descending Coronary Artery in Patients With Cardiac Syndrome X

https://doi.org/10.1016/j.amjcard.2006.12.070Get rights and content

Data on coronary flow reserve (CFR) in patients with syndrome X are still controversial. Further, noninvasive evaluation of epicardial and microvascular flow reserves in these patients has never been performed. In 17 patients with syndrome X and in 17 age- and gender-matched control subjects, CFR in the mid left anterior descending coronary artery (LAD) was evaluated by transthoracic color and pulse-wave Doppler using a 7-mHz probe (Sequoia, Siemens). Peak diastolic LAD flow was calculated at rest and at peak adenosine (140 μg/kg/min intravenously in 90 seconds). Myocardial contrast echocardiography (MCE) was performed at rest and during adenosine use by real-time cadence pulse sequencing and intravenous SonoVue (Bracco; 5 ml at 1 ml/min) and microvascular blood volume (A), velocity (β), and flow (A×β) by replenishing curves (y = A[1 − eβt]). CFR was measured by Doppler echocardiography as an adenosine/rest velocity ratio and by MCE as a microvascular volume, velocity, and flow adenosine/rest ratio. Compared with controls, patients with syndrome X demonstrated lower LAD CFR and velocity and flow microvascular flow reserves (p <0.01, <0.005, and <0.005, respectively). In patients with syndrome X, those with angina and ST-segment depression during adenosine testing had even lower LAD CFR and velocity and flow microvascular flow reserves compared with those with no symptoms (p <0.0001, <0.0001, and <0.005, respectively). LAD CFR demonstrated a significant linear correlation with velocity microvascular flow reserve (r = 0.92, p <0.0001) and flow microvascular flow reserve (r = 0.77, p <0.0001). In conclusion, CFR in the LAD, successfully evaluated by transthoracic Doppler echocardiography and MCE, is significantly decreased in patients with syndrome X and even more in those with angina pectoris and ST-segment depression during adenosine testing. Thus, noninvasive evaluation of CFR by echocardiography is feasible and provides information on the severity of microvascular impairment.

Section snippets

Methods

We enrolled 17 patients with typical cardiac syndrome X in the study (8 men; mean 55 ± 10 years of age). Cardiac syndrome X was diagnosed according to the presence of typical effort angina, ST-segment depression ≥1 mm on exercise stress testing, and angiographically normal coronary arteries. As a control group, we studied 17 healthy control subjects who were comparable to patients with regard to age and gender (7 men; mean 55 ± 10 years of age).

Patients and controls were excluded in cases of

Results

The main clinical characteristics of patients with cardiac syndrome X and healthy control subjects are presented in Table 1. The 2 groups were similar with respect to age, gender, and cardiovascular risk factors. The mid-distal LAD was correctly visualized by transthoracic echocardiographic color Doppler and myocardial contrast echocardiographic evaluation was effectively performed in all subjects without clinical side effect. Adenosine was also infused in all patients without significant side

Discussion

This is the first study showing an impairment of coronary microvascular function in patients with cardiac syndrome X by combined assessment of CFR by transthoracic Doppler echocardiography of the LAD and by MCE. The results obtained with the 2 methods were highly correlated, thus lending further support to the importance of abnormalities in coronary microvascular function as a cause of the syndrome. Further, in this study, we were able to identify a subgroup of patients with syndrome X in whom

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