Relation between cardiovascular risk factors and coronary microvascular dysfunction in cardiac syndrome X.
BACKGROUND
The causes of coronary microvascular dysfunction (CMVD) in patients with cardiac syndrome X (CSX) are largely unknown. Common cardiovascular risk factors (CVRFs) and increased markers of inflammation have been associated with CMVD in some studies, but their role in determining CMVD in CSX patients remains poorly known.


METHODS AND RESULTS
We studied 71 CSX patients (56 ± 9 years, 23 men) and 20 healthy volunteers (52 ± 7 years, nine men). Using transthoracic Doppler echocardiography, coronary microvascular vasodilator function was assessed in the left anterior descending coronary artery as the ratio of diastolic coronary blood flow (CBF) velocity at peak intravenous adenosine administration and during cold pressor test (CPT) to the respective basal CBF velocity values. Common CVRFs tended to be more frequent and C-reactive protein (CRP) levels were higher (P < 0.001) in CSX patients than in controls. Both CBF responses to adenosine (2.05 ± 0.6 vs. 2.92 ± 0.9, P < 0.001) and to CPT (1.71 ± 0.6 vs. 2.42 ± 0.7, P < 0.001) were lower in CSX patients than in controls. The differences between the two groups in CBF response to adenosine and in CBF response to CPT remained highly significant (P < 0.01 for both) after adjustment for all CVRFs, including serum CRP levels.


CONCLUSION
In CSX patients, both endothelium-dependent and endothelium-independent CMVD cannot be reliably predicted by CVRFs (including serum CRP levels), alone or in combination.