Assessment of coronary artery bypass graft disease using cardiovascular magnetic resonance determination of flow reserve.

OBJECTIVES: The purpose of this study was to assess the value of cardiovascular magnetic resonance (CMR)-determined graft flow and flow reserve in differentiating significant from non-significant vein graft disease. BACKGROUND: In patients after coronary artery bypass grafting (CABG), non-invasive testing may be helpful in the detection of recurrent graft disease. METHODS: Randomly selected patients (n = 21) scheduled for X-ray angiography because of recurrent chest complaints after CABG were included for evaluation of vein grafts (n = 40) by CMR. Three-dimensional contrast-enhanced CMR angiography was performed and followed by flow measurements at rest and during hyperemia in patent grafts only. Flow reserve was calculated when resting flow exceeded 20 ml/min. Analysis was based on four categories defined by X-ray angiography: occluded grafts (n = 3), grafts with stenosis >50% (n = 19), grafts with stenosis <50% with diseased graft run-off (n = 8), and grafts with stenosis <50% and normal run-off (n = 10). RESULTS: The CMR angiography demonstrated occlusion of three grafts. In nine of the 37 patent grafts, basal blood flow was <20 ml/min, all demonstrating significant stenosis at X-ray angiography. In grafts with resting flow >20 ml/min (n = 28), flow reserve significantly differed between grafts without stenosis and grafts with significant stenosis or with diseased run-off (2.5 +/- 0.7 vs. 1.8 +/- 0.9, p = 0.04). An algorithm combining basal volume flow <20 ml/min and graft flow reserve <2 had a sensitivity and specificity of 78% and 80% respectively for detecting grafts with significant stenosis or diseased run-off. CONCLUSIONS: This feasibility study showed that quantification of flow and flow reserve by CMR may serve as a non-invasive adjunct to differentiate between vein grafts without stenosis and grafts with significant stenosis or diseased run-off.

Magnetic resonance imaging versus Doppler guide wire in the assessment of coronary flow reserve in patients with coronary artery disease.

BACKGROUND: Coronary flow velocity reserve (CFVR), defined as the ratio of maximal hyperaemic to baseline flow velocity, has been validated as a marker of physiological significance of a coronary lesion. Clinically, this parameter is measured invasively during X-ray angiography using the Doppler guide wire. With magnetic resonance (MR) imaging it is possible to quantify CFVR non-invasively. DESIGN: The purpose of the study was to compare CFVR, acquired with MR imaging and the Doppler guide wire in patients with coronary artery disease. METHODS: Twenty-two patients suffering from one- or two-vessel coronary artery disease as derived from diagnostic X-ray coronary angiography were included. Coronary flow velocity reserve was measured at baseline and during maximal hyperaemia, obtained by intravenous administration of adenosine using MR phase contrast velocity quantification. Within 2 weeks CFVR was measured invasively with a Doppler guide wire. RESULTS: In 26 coronary arteries CFVR was acquired with both techniques. Mean CFVR in the stenosed and healthy reference arteries was 1.5 +/- 0.7 and 2.7 +/- 1.0 (P < 0.01) respectively for MR measurements and 1.9 +/- 0.7 and 3.1 +/- 0.6 (P < 0.01) respectively for Doppler measurements. Bland-Altman analysis revealed a non-significant mean difference between the two techniques of 0.4 +/- 1.2. CONCLUSION: In a selected group of stable patients with coronary artery disease MR flow velocity quantification provides non-invasive data equivalent to the invasive Doppler guide wire data. Variability in both the MR and Doppler ultrasound measurement resulted in a significant scatter of data without systematic difference.

Three-dimensional magnetic resonance coronary angiography using a new blood pool contrast agent: initial experience.

OBJECTIVE: The aim of this feasibility study was to assess the effect of a new blood pool contrast agent on magnetic resonance coronary angiography (MRCA) in patients suspected of having coronary artery disease. METHODS: Nine patients referred for diagnostic x-ray coronary angiography in the evaluation of chest pain underwent MRCA using a thin-slab three-dimensional (3D) breath-hold segmented gradient echo technique at 1.5 T before and after intravenous administration of feruglose, a new blood pool contrast agent. RESULTS: A total of 36 coronary arteries, including 15 stenoses were evaluated. Overall agreement of visually assessed stenoses > 50% was 86%. The mean signal-to-noise ratio in the left anterior descending artery (LAD) did not change significantly after contrast administration, a relative improvement of 1.2 +/- 0.4 (p = 0.1), whereas the mean contrast-to-noise ratio of blood to myocardium improved by 3 +/- 2 (p = 0.01). CONCLUSION: A thin-slab 3D breath-hold scan combined with feruglose allows rapid localization and coverage of the proximal coronary arteries.