European Heart Journal Advance Access originally published online on May 25, 2006
European Heart Journal 2006 27(13):1627-1628; doi:10.1093/eurheartj/ehl030
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Is myocardial contrast echocardiography ready to assume ‘gold standard’ status for quantification of collateral flow in humans?: reply
Department of Cardiology
University Hospital Bern
Switzerland
E-mail address: rolf.vogel{at}insel.ch
Department of Cardiology
University Hospital Bern
Switzerland
Department of Cardiology
University Hospital Bern
Switzerland
Department of Cardiology
University Hospital Bern
Switzerland
Department of Cardiology
University Hospital Bern
Switzerland
Department of Cardiology
University Hospital Bern
Switzerland
We agree with the comment of Spaan and Siebes that blood vessels are not rigid and thus allow blood volumes to vary dynamically with perfusion pressure.1 Constant resistances in the coronary circulation are the core assumption of the theory describing the pressure-derived collateral flow index (CFIp).2 In contrast to that, the collateral perfusion index (CPI), reflecting collateral relative to normal myocardial blood flow (MBF),3 does not rely on assumptions regarding myocardial resistances or blood volumes.
The constituents of MBF (mL/min/g) as determined by myocardial contrast echocardiography (MCE), i.e. the relative blood volume (rBV, mL/mL) and its exchange frequency (ß,1/min),4 were assessed each during angioplasty and after successful revascularization.4 Therefore, the CPI accounts for dynamic changes of blood volumes, provided that they reach steady state prior to their measurement. Although steady-state conditions after revascularization can be guaranteed,3 the time to stable myocardial blood volumes after onset of coronary occlusion is not known in humans. In our study, coronary arteries were occluded during 60 s. The acquisition of perfusion sequences took 15 s: the first two to three heart cycles were used to measure the plateau signal intensity A and rBV, respectively, followed by the contrast destruction during one to two heart cycles and the contrast refill during the remaining acquisition time. Perfusion sequences were acquired towards the end of the 1-min occlusion, thus allowing blood volumes to stabilize during 45 s prior to the measurement. From an ex vivo, non-contracting canine model, Spaan et al.5 suggested a time constant of ‘several seconds’ for intramural blood volume changes. This value most likely represents an upper limit, as myocardial blood volumes were measured by an indirect technique that added further dynamics to the entire system. The period between the onset of the coronary occlusion and the start of the perfusion sequence is sufficiently long to guarantee steady blood volumes, i.e. more than five time constants, provided that mechanical properties of the contracting human myocardium and the aforementioned model are similar.
We are aware that animal data may have limited significance for humans. However, these are the best data available, and in our opinion, they emphasize the gold standard status of MCE in conjunction with our protocol to assess collateral flow of the beating human heart.
References
- Spaan J and Siebes M. (2006) Is myocardial contrast echocardiography ready to assume ‘gold standard’ status for quantification of collateral flow in humans? Eur Heart J in press. doi: 10.1093/eurheartj/ehl030.
- Pijls NH, van Son JA, Kirkeeide RL, De Bruyne B, Gould KL. (1993) Experimental basis of determining maximum coronary, myocardial, and collateral blood flow by pressure measurements for assessing functional stenosis severity before and after percutaneous transluminal coronary angioplasty. Circulation 87:1354–1367.
[Abstract/Free Full Text] - Vogel R, Zbinden R, Indermühle A, Windecker S, Meier B, Seiler C. (2006) Collateral flow measurements in humans by myocardial contrast echocardiography: validation of coronary pressure derived collateral flow assessment. Eur Heart J 27:157–165.
[Abstract/Free Full Text] - Vogel R, Indermühle A, Reinhardt J, Meier P, Siegrist P, Namdar M, Kaufmann P, Seiler C. (2005) The quantification of absolute myocardial perfusion in humans by contrast echocardiography: algorithm and validation. J Am Coll Cardiol 45:754–762.
[Abstract/Free Full Text] - Spaan JA, Cornelissen AJ, Chan C, Dankelman J, Yin FC. (2000) Dynamics of flow, resistance, and intramural vascular volume in canine coronary circulation. Am J Physiol Heart Circ Physiol 278:H383–H403.
[Abstract/Free Full Text]
CiteULike 
Connotea 
Del.icio.us What's this?
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||