Technical Development of Cardiovascular Magnetic Resonance Imaging

This study will explore new ways of using magnetic resonance imaging (MRI) to evaluate the heart and blood vessels of patients with cardiovascular disease, including better detection of myocardial infarction (heart attack) and blockage of heart and leg arteries. Patients 18 years of age and older with cardiovascular disease may be eligible for this study. All participants will have magnetic resonance imaging of the heart. MRI uses a magnetic field and radio waves to show structural and chemical changes in tissues. For the procedure, the patient lies on a table surrounded by a metal cylinder (the scanner). A 'gadolinium contrast' material may be injected into the patient s vein during part of the study to brighten the images. Patients wear earplugs during the scan to muffle loud knocking sounds caused by the electrical switching of the magnetic fields. They will be asked to hold their breath intermittently for 5 to 20 seconds during the scan. They will be monitored with an electrocardiogram (EKG) during the procedure and will be in contact by intercom at all times with the person performing the scan. Patients can request to stop the study and come out of the scanner at any time. The procedure may last from 30 to 90 minutes. An echocardiogram a test that uses sound waves to produce pictures of the heart and blood vessels-may be done to confirm the MRI findings. In addition, patients may undergo one or more of the following optional studies:

• Dobutamine stress MRI - This test uses dobutamine-a medicine that simulates exercise by increasing heart rate and heart function-to detect blockages in the coronary arteries (vessels that supply oxygen and nutrients to the heart) and locate areas of the heart that are permanently damaged, perhaps by a previous heart attack. For this test, MRI pictures of the heart are taken before, during and after administration of dobutamine. Gadolinium may be injected during part of the study to brighten the images. An EKG will be used to monitor the heart during the procedure.
• Vasodilator MRI - The procedure and objectives of this test are the same as those described for dobutamine stress MRI, except that this study uses dipyridamole or adenosine. These drugs dilate blood vessels, causing increased blood flow to the heart.
• Plethysmography MRI - This test determines the presence and severity of narrowing in arteries that supply blood to the leg. Blockage of these vessels often causes pain while walking. This study will compare plethysmography MRI with venous occlusion plethysmography, an older method of measuring blood flow in the legs. For venous occlusion plethysmography, a large blood pressure cuff is placed around the upper leg and a strain gauge (thin elastic band) is placed around the calf. The pressure cuff is inflated very tightly for 5 minutes to block blood flow to the leg, and another pressure cuff over the ankle is also inflated. When the large cuff is deflated, blood rushes to the leg, a smaller cuff is inflated to a low pressure, and the strain gauge measures the maximum blood flow to the leg for 1 or 2 more minutes. This procedure is done once or twice outside the MRI scanner and once or twice inside the scanner. The scans are performed as described above for the dobutamine and vasodilator studies. The strain gauge is not used for plethysmography MRI the MRI pictures are used to measure flow.