technetium-tc-99m-tetrofosmin and Transposition-of-Great-Vessels

Recent studies performed with positron emission tomography have suggested that coronary flow reserve (CFR) is moderately to severely reduced after the arterial switch operation (ASO). These findings are of great concern but have not been confirmed by other methods.. Eleven symptom-free children were studied between 4 and 11 (median 6.0) years after the ASO. Flow velocity in the left anterior descending (LAD) and right coronary arteries (RCA) was measured with a 0.014-inch Doppler FloWire (Cardiometrics) before and after intracoronary injection of adenosine (0.5 microg/kg) and nitroglycerin (5 microg/kg). CFR was defined as the ratio of hyperemic to basal average peak velocity (APV). The median (range) CFR in the LAD was 3.7 (3.0 to 4.8) and 3.4 (2.9 to 4.8) in the RCA. The increase in APV after intracoronary injection of nitroglycerin was 300% (240% to 420%) in the LAD and 260% (190% to 460%) in the RCA. APV at rest was 15.0 (14.0 to 21.0) cm/s in the LAD and 16.0 (9.6 to 30.0) cm/s in the RCA. A linear relation was found between right ventricular systolic pressure and resting APV in the RCA (r=0.77, P=0.0056), and between resting APV and CFR (r=-0.61, P<0.05) in the RCA.. The CFR and coronary vasoreactivity to nitroglycerin in children treated for transposition of the great arteries with the ASO was within normal limits. Increased right ventricular pressure and myocardial hypertrophy can cause increased resting coronary flow velocity in the RCA and affect CFR negatively.

Topics: Adenosine; Blood Flow Velocity; Cardiac Catheterization; Child; Child, Preschool; Coronary Angiography; Coronary Circulation; Coronary Disease; Coronary Vessels; Echocardiography; Electrocardiography; Humans; Laser-Doppler Flowmetry; Linear Models; Nitroglycerin; Organophosphorus Compounds; Organotechnetium Compounds; Pulmonary Valve Stenosis; Tomography, Emission-Computed, Single-Photon; Transposition of Great Vessels; Vasodilator Agents; Vasomotor System; Ventricular Function, Left

Transposition of the great arteries is a congenital heart defect defined by an abnormal connection between the aorta, pulmonary artery, and the ventricles, resulting in parallel systemic and pulmonary circulations. Long-term follow-up data of patients who underwent correction via an arterial switch operation have recently shown that as a result of re-implantation of the coronary arteries in the neo-aorta, coronary stenosis and occlusion are relatively common complications. In this report, we discuss two cases illustrating the added value of myocardial perfusion imaging (MPI) and cardiac CT for the assessment of these patients. Based on the available literature we conclude that MPI and cardiac CT are excellent non-invasive methods to evaluate coronary anatomy and myocardial function also in this specific group of patients.

Topics: Adolescent; Coronary Angiography; Coronary Stenosis; Coronary Vessels; Exercise; Heart; Heart Ventricles; Humans; Male; Myocardial Ischemia; Myocardial Perfusion Imaging; Organophosphorus Compounds; Organotechnetium Compounds; Radionuclide Imaging; Risk; Tomography, Emission-Computed, Single-Photon; Tomography, X-Ray Computed; Transposition of Great Vessels