ORLANDO, Fla., March 7, 2005 - Cardiac magnetic resonance imaging (CMR) is an effective tool for evaluating endothelial dysfunction - functional abnormalities within the lining of coronary arteries - one of the earliest warning signs of heart disease, according to a study presented today at the 54th Annual Meeting of the American College of Cardiology. The promising results show for the first time that CMR offers a direct, noninvasive method for detection of the earliest abnormalities in the walls of the coronary arteries.

The endothelium is a thin layer of cells that lines blood vessels in the body and regulates blood flow. Endothelial dysfunction prevents arteries that supply blood to the heart from expanding normally, contributing to the formation of blockages and raising the risk for heart attacks. As the earliest measurable functional abnormality of vessel walls, the assessment of endothelial dysfunction has also been shown to predict cardiovascular events even before any narrowing or blockage of the coronary arteries has developed. 

“St. Francis Hospital, the Heart Center®, is proud to share the first data that shows CMR may allow physicians to identify and treat patients - even those who are asymptomatic - much earlier than in the past,” said lead study author Nathaniel Reichek, MD, FACC, FAHA, Director of Research and Education at St. Francis Hospital in Roslyn, New York and Professor of Medicine and Biomedical Engineering at the State University of New York (SUNY) at Stony Brook. “As the leading cause of death in the United States, it is very important to identify the warning signs of heart disease as early as possible.”

Study Design
The endothelium has the capacity to regulate blood flow in response to pharmacological or mechanical stimuli. In patients with endothelial dysfunction, a stimulus that would normally cause vessels to expand and increase blood flow cannot obtain this response. 

In this study, MRI and phase-contrast velocimetry were used to assess changes in coronary artery cross sectional area, coronary blood flow and flow velocity during cold pressor testing (CPT) and following sublingual nitroglycerin (NTG). CPT was selected because this stimulus normally increases blood flow, while ED impairs this increase. NTG causes endothelial-independent increase in coronary blood flow.

Methodology
The study was a single-site controlled clinical trial of 23 patients (control group: n=7, ages 52±11 yrs.; risk group: n=16, ages 64±5 yrs.) Risk factors associated with coronary artery disease in the risk group included hypertension (7 patients), hyperlipidemia (11), diabetes mellitus (2) and smoking. Coronary artery cross-sectional area (CSA), mean diastolic coronary blood flow (CBF) and mean diastolic flow velocity (V) of the proximal left anterior descending coronary artery (LAD) were measured using a Siemens Sonata at baseline 1; 90 seconds of cold pressor testing (CPT); baseline 2 (30 minutes after CPT); and serially after nitroglycerin (NTG) 0.4 mg sublingually. 

Measurement of coronary CSA, CBF and V was performed by a single, blinded observer, after magnification of each image, using Argus software. A cross-section of the proximal LAD was imaged using breath-hold turbo spin echo imaging to assess coronary CSA. Segmented phase contrast TurboFLASH CMR velocimetry was used to assess CBF and V.

Results
CMR showed an increase in mean diastolic coronary blood flow and mean diastolic flow velocity during cold pressor testing in control subjects, but not in patients with risk factors for coronary artery disease.  No change in coronary artery cross sectional area was detected in either group. MRI also depicted endothelium-independent vasodilation with increased mean diastolic coronary blood flow and diastolic flow velocity, as well as increased coronary artery cross sectional area following nitroglycerin. 

“Thus, cardiac magnetic resonance imaging permits direct, noninvasive assessment of coronary endothelial dysfunction,” said Dr. Reichek. “This easy-to-perform technique is a valuable tool to identify patients at risk for cardiovascular events before they have significant symptoms or even asymptomatic coronary narrowing.”

About St. Francis Hospital, The Heart Center®
St. Francis Hospital, The Heart Center® is New York State’s only specialty designated cardiac center and is one of the five busiest heart centers in the United States.  A recognized national leader in the diagnosis, treatment and prevention of cardiac disease, St. Francis Hospital, The Heart Center is one of only two hospitals in the metropolitan area with risk-adjusted mortality rates significantly below the statewide average for heart valve surgery and/or coronary artery bypass surgery.1

Physicians at St. Francis Hospital, The Heart Center offer unparalleled experience in the most innovative medical and surgical techniques and non-invasive imaging, including cardiac magnetic resonance and nuclear imaging, three-dimensional echocardiography, catheter-based treatment of congenital heart defects, radiofrequency cardiac ablation, pacemaker and defibrillator implantation, and a broad array of coronary, carotid and peripheral arterial angioplasty.

A leader in cardiovascular care for more than 50 years, St. Francis Hospital, The Heart Center is a member of Catholic Health Services of Long Island (CHS), an integrated healthcare delivery system that includes some of the region's finest health and human services agencies. As stewards of the Catholic Health Services vision of the dignity of every person, St. Francis Hospital’s mission is to provide compassionate, humanistic care to those in need.

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