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Coronary flow: clinical considerations
  1. D V Cokkinos1,
  2. A Manginas2,
  3. V Voudris2
  1. 1University of Athens, Onassis Cardiac Surgery Center, Athens, Greece
  2. 2Onassis Cardiac Surgery Center
  1. Correspondence to:
    Professor Dennis V Cokkinos, Onassis Cardiac Surgery Center, 1st Cardiology Department, 356 Sygrou Avenue, 174 74 Athens, Greece;

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In the measurement of coronary blood flow to determine the success of percutaneous coronary intervention, invasive techniques, coupled with plaque characterisation and other intracoronary imaging modalities, may prove invaluable

The measurement of coronary blood flow (CBF) has transcended the realm of observational curiosity through the emergence of two developments:

  • Firstly, the application of easier methods to measure it, which have replaced the older cumbersome inert gas and thermodilution techniques. Two notable examples are the non-invasive positron emission tomography (PET) calculations and the intracoronary Doppler measurements of flow velocity. Formerly, Doppler catheters were used, which could not measure flow distally to a stenosis. This problem was overcome by the use of the Flowire, which with a diameter of 0.014 inches can be placed across the stenosis during the course of invasive procedures. Because of its small diameter, this wire does not cause significant flow disturbances, as was the case with the previously used Doppler catheters. The Doppler wire actually measures flow velocity. For the velocity values to be equivalent to CBF, the cross sectional area of the vessel must be measured.

  • Secondly, the realisation that diminution of flow distally to a significant stenosis is reliably correlated to manifestations of ischaemia.

Concomitantly with the measurement of CBF, the importance of the coronary flow reserve (CFR) was appreciated. This term signifies the difference between CBF under maximal hyperaemia, produced by various interventions, and basal flow. Basal CBF amounts to approximately 1 ml/g of myocardial tissue/min; at maximal hyperaemia it can increase by 3–4 times, according to the technique employed.

Many factors influence the CFR values. Because of the use of CFR in the assessment of coronary artery stenosis, the degree of stenosis has attained major importance. However, the actual coronary resistance is determined to a far greater degree by microvascular resistance. Since the …

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