2nd Department of Cardiology
Jagiellonian University School of
Medicine, 17 Kopernika Str.,
31-501 Cracow, Poland
E-mail address: dimitrow{at}mp.pl
Department of Medicine, Jagiellonian
University School of Medicine,
8 Skawinska Str., 31-066 Cracow,
Poland
We would like to add some comments to an interesting paper of Voci et al.1 Apart from the anterior and posterior descending coronary artery, it is possible to visualize transthoracically proximal and middle segments of the circumflex coronary artery and all three segments of the right coronary artery.25 The images other than from the apical windows are obtainable.4
Reduction of coronary flow reserve (CFR) depends not only on severity of stenoses in epicardial arteries but also on a number of microvascular factors which either limit maximal vasodilatation or increase baseline coronary blood flow.2,6 In the absence of stenosis in the epicardial coronary artery, decreased CFR enables the detection of impaired microvascular vasodilatation in left ventricular hypertrophy (hypertension, aortic stenosis, and hypertrophic cardiomyopathy) diabetes mellitus, hypercholesterolaemia, smoking, and syndrome X.2,6 Importantly, epicardial coronary artery stenosis and microcirculation abnormalities may co-exist and cumulatively decrease the CFR. It is possible to distinguish the haemodynamic effect of stenosis of epicardial coronary artery from microcirculation abnormalities in order to identify cases with moderate stenosis in which coronary intervention can correct the abnormalities of blood flow. For this purpose, a stenosis-specific parameter, i.e. the accelerated coronary flow velocity at the site of stenosis, is measurable.36 Voci et al. reasonably stated that acceleration at the site of stenosis depends not only on the severity of stenosis but also on other factors altering the velocity gradient. Accordingly, we suspected that universal borderline velocity discriminating non-stenosed from stenosed arteries probably does not exist and rather a method of standardization of velocity assessment should be used. Our data3,5 support suggestions that, in stenosis detection, a velocity ratio (i.e. a ratio of maximal velocity within the stenosis and immediately proximal to it) is more reliable than any single velocity measurement. We successfully used the criteria valid for peripheral arteries where local velocity increase with at least doubling of velocity within the stenosis is regarded as a sign of haemodynamically significant stenosis.
Finally, we would like to mention that coronary endothelium-dependent vasodilatation is also measurable by transthoracic Doppler echocardiography.7
References
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