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LETTERS TO THE EDITOR
Second Department of Medicine and Cardiology Center
University of Szeged
Szeged, Hungary
e-mail: nemes{at}in2nd.szote.u-szeged.hu
ABSTRACT
We examined the hypothesis that a stiff aorta is associated with reduced coronary blood flow (CBF) and CBF response to percutaneous coronary intervention (PCI). Aortic mechanical properties are thought to affect CBF, with increased stiffness associated with decreased coronary perfusion. Animal studies are conflicting, and human evidence is lacking. Even less is known about the effects of aortic stiffness on the CBF response to successful PCI. In 18 subjects undergoing elective PCI, a Doppler velocity guidewire was positioned proximal to a severe coronary stenosis to measure resting and adenosine-induced hyperemic CBF before and after PCI. Stenosis severity was assessed with Doppler velocity and pressure guidewires. Aortic mechanical indexes measured included central pulse-wave velocity (cPWV) and central pulse pressure (cPP). PCI was successful in all subjects (diameter stenosis: 88 ± 9% to 2 ± 7%; coronary flow velocity reserve: 1.8 ± 0.6 to 3.0 ± 0.8; fractional flow reserve: 0.57 ± 0.19 to 0.92 ± 0.06; all P < 0.001). With the adjustment for age and gender, resting and hyperemic CBF were inversely related to cPWV irrespective of the presence of stenosis (resting: before PCI, r2 = 0.452, P < 0.01; after PCI, r2 = 0.261, P = 0.043; hyperemic: before PCI r2 = 0.503, P = 0.005; after PCI r2 = 0.500, P = 0.002), whereas they were related to cPP in absence of stenosis (resting: r2 = 0.368, P = 0.022; hyperemic: r2 = 0.370, P = 0.016). Hyperemic CBF response (P = 0.005) and hyperemic CBF improvement from PCI (P = 0.025) were less marked in a stiff aorta than a compliant aorta. A stiff aorta is associated with a reduction in CBF, a lower hyperemic CBF response, and may reduce the improvement in hyperemic CBF after successful PCI.
To the Editor: We read with great interest and congratulate Leung et al. (1) on their study entitled "Aortic stiffness affects the coronary blood flow response to percutaneous coronary intervention." They concluded in this intriguing study that a stiff aorta is associated with a reduction in coronary blood flow (CBF), a lower hyperemic CBF response, and may reduce the improvement in hyperemic CBF after successful percutaneous coronary intervention. However, we feel that a few additional comments are necessary.
To characterize aortic stiffness, different elastic properties of descending aorta can be assessed by transoesophageal echocardiography (TEE) as elastic modulus (Ep) and Young’s circumferential static elastic modulus (Es). Coronary flow velocity reserve (CFVR), evaluated by means of stress TEE, provides physiological information regarding the function of the left anterior descending coronary artery (LAD). Previous clinical studies (2–8) verified that stress TEE is a useful method for simultaneous evaluation of aortic elastic properties (Ep and Es) and CFVR.
Evident from previous TEE work, we have demonstrated reduced CFVR and increased Ep and Es (increased aortic stiffness) in patients with LAD disease compared with patients with normal epicardial coronary arteries (2). No further changes in these parameters were found in cases with multivessel disease (MVD), regardless of the extent of the disease (2, 3), whereas in patients with nonsignificant coronary artery disease, CFVR and aortic distensibility were better than those in LAD disease/MVD patients and worse than those in patients with normal epicardial coronary arteries (2).
The aortic distensibility and LAD-CFVR were similarly reduced in Type 2 diabetic patients with normal epicardial coronary arteries and in LAD disease patients compared with nondiabetic subjects with a normal coronary angiogram. These results have suggested the overall effect of diabetes mellitus on the function and structure of the descending aorta and coronary arteries (4).
A reduced CFVR has additionally been demonstrated in aortic stenosis (AS) patients with normal epicardial coronary arteries, characterizing diminished reserve capacity of the LAD, and an altered aortic stiffness (increased Ep and Es) compared with subjects without valvular or coronary artery disease (5). These findings have supported the suggestion that increased aortic stiffness (and, partially, the reduced CFVR) can be the early manifestations of the atherosclerosis process. Our initial results have suggested that there are no differences in these values if mitral stenosis is associated with AS (6).
The reduction in CFVR was detected in patients with aortic intimal thickening [grade 1 aortic atherosclerosis (AA)] compared with subjects without AA (7). No further decrease was observed in patients with higher grades of AA (in the presence of different grades of aortic plaque). Ep and Es increased continuously in parallel with the aortic grade, and significant differences were found between patients with grade 2–3 and those with grade 0 or 1 AA. Furthermore, it was also demonstrated that CFVR, Ep, and Es predict patients with aortic plaque (8).
Overall, these studies confirmed that there is a strong relationship between the aortic stiffness (Ep and Es) and coronary vasoreactivity (LAD-CFVR) in different patient populations. However, further investigations are warranted, mainly on the effects of different risk factors on these parameters.
REFERENCES
This article has been cited by other articles:
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  A. Nemes Relationship between coronary microcirculatory function and aortic stiffness in diabetes. J. Am. Coll. Cardiol., February 5, 2008; 51(5): 597 - 598. [Full Text] [PDF]
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