Coronary flow reserve assessment: reply: the ghost of microcirculation

P. Voci, F. Pizzuto and F. Romeo

Section of Cardiology II
University of Rome ‘Tor Vergata’
Via San Giovanni Eudes, 27
Rome
Italy
Tel: +39 06 6615 8122
Fax: +39 06 2090 0382
E-mail address: voci{at}uniroma1.it

The possibility to directly image the coronary arteries and to measure the stenotic gradient was foreseen by Hozumi et al.1 in patients with left anterior descending (LAD) coronary artery stent, but unfortunately it could not be reproduced by others. We agree that scanning along the LAD to measure velocity gradients may be the future, but it is unfortunately not feasible today. Regarding coronary segmentation, by definition, the circumflex coronary artery (Cx) is divided into a proximal and a distal segment, but the middle segment does not exist.2 By transthoracic ultrasound it is theoretically possible to image only the proximal segment, but neither the marginal branches nor the distal Cx. Similarly, it is very hard to image the course of the right coronary artery. Both our findings and the literature data on transthoracic coronary Doppler ultrasound consistently show that the impact of smoke, hormonal changes, remote coronary artery disease,3 hypertrophy (Figure 1), and even diabetes (unpublished personal data) on coronary flow reserve (CFR) is minimal when compared with that of an epicardial stenosis, and that microcirculation alone (if we exclude the very first days of acute myocardial infarction4) almost never reduces CFR to less than two. Noteworthy, if CFR is reduced because baseline flow is increased, this only means that part of the reserve is ‘burned’ at ‘rest’, which should never be interpreted as any microvascular dysfunction. Figure 1 works better than the 500 words allowed for this reply letter, to remove from our dreams the ghost of microcirculation.



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Figure 1 Hypertrophic cardiomyopathy with mid-ventricular obstruction.

 

References

  1. Hozumi T, Yoshida K, Akasaka T et al. Value of acceleration flow and the prestenotic to stenotic coronary flow velocity ratio by transthoracic color Doppler echocardiography in noninvasive diagnosis of restenosis after percutaneous transluminal coronary angioplasty. J Am Coll Cardiol 2000;35:164–168.[CrossRef][ISI][Medline]
  2. Rogers WJ, Alderman EL, Chaitman BR et al. Bypass angioplasty revascularization investigation (BARI): baseline clinical and angiographic data. Am J Cardiol 1995;75:9C–17C.[CrossRef][Medline]
  3. Pizzuto F, Voci P, Mariano E et al. Coronary flow reserve of the angiographically normal left anterior descending coronary artery in patients with remote coronary artery disease. Am J Cardiol 2004;94:577–582.[CrossRef][ISI][Medline]
  4. Lepper W, Hoffmann R, Kamp O et al. Assessment of myocardial reperfusion by intravenous myocardial contrast echocardiography and coronary flow reserve after primary percutaneous transluminal coronary angiography in patients with acute myocardial infarction. Circulation 2000;101:2368–2374.[Abstract/Free Full Text]




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