Comparison of three different principles in the assessment of coronary flow reserve from digital angiograms

Abstract

In 70 patients without coronary disease we have compared three different principles to assess coronary flow reserve during diagnostic heart catheterization. Digital angiograms with ECG-triggered bolus injections of 4 to 8 ml of contrast medium at rest and after stimulation by dipyridamole (0,5 mg/kg i.v.) or papaverine (12,5 mg i.c.) were acquired in a 512 x 512 matrix at 8 bit resolution (ADAC 4100) and stored on a digital disk at 25 frames/sec. or 2 frames/cardiac cycle (PPR-mode). Angiograms were processed by cyclic R-wave-gated mask mode subtraction and coronary flow in the LAD area was assessed by three different approaches: 1. A traditional densitometric principle. 2. The 'CMAP' principle. 3. A modification of the Stewart-Hamilton principle comparing the total amount of contrast medium that enters the coronary circulation to the area of the contrast dilution curve in a fixed portion of the LAD. Flow was measured simultaneously during angiography using the thermodilution technique for coronary sinus/great cardiac vein flow. Drug stimulation resulted in an increased coronary blood flow up to five times of resting flow. Regression analysis revealed the following results for the assessment of the coronary flow reserved by digital angiography (y) when compared to thermodilution (x): [table: see text] Method 2 could be improved by replacing the density factor by morphometrically measured proximal LAD volume (y = 0.77x + 0.55; r = 0.78; SEE = +/- 0.43). In conclusion, our data suggest that the Stewart-Hamilton principle may be advantageous over time parameter-dependent approaches in the assessment of coronary flow reserve by digital angiography.