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CLINICAL RESEARCH: CARDIAC MAGNETIC RESONANCE

Noninvasive assessment of coronary vasodilation using magnetic resonance angiography

Masahiro Terashima, MD, PhD^*, Craig H. Meyer, PhD, Brian G. Keeffe, MD^*, Eric J. Putz, MD^*, Erasmo de la Pena-Almaguer, MD^*, Phillip C. Yang, MD^*, Bob S. Hu, MD^*,, Dwight G. Nishimura, PhD and Michael V. McConnell, MD, MSEE^*,,*

^* Division of Cardiovascular Medicine
Department of Electrical Engineering, Stanford University, Stanford, California

Manuscript received June 23, 2004; revised manuscript received September 16, 2004, accepted September 21, 2004.

^* Reprint requests and correspondence: Dr. Michael V. McConnell, Cardiovascular Medicine, Stanford University School of Medicine, 300 Pasteur Drive, Room H-2157, Stanford, California 94305 (Email: mcconnell{at}stanford.edu).

OBJECTIVES: The purpose of this study was to investigate the use of coronary magnetic resonance angiography (MRA) for assessing human epicardial coronary artery vasodilation.

BACKGROUND: Coronary vasodilation plays a vital role in the human coronary circulation. Previous studies of epicardial coronary vasodilation have used invasive coronary angiography. Coronary MRA may provide an alternative noninvasive method to directly assess changes in coronary size.

METHODS: Thirty-two subjects were studied: 12 patients (age 55 ± 18 years) and 20 healthy subjects (age 34 ± 4 years). High-resolution multi-slice spiral coronary MRA (in-plane resolution of 0.52 to 0.75 mm) was performed before and after sublingual nitroglycerin (NTG). Quantitative analysis of coronary vasodilation was performed on cross-sectional images of the right coronary artery (RCA). A time-course analysis of coronary vasodilation was performed in a subset of eight subjects for 30 min after NTG. Signal-to-noise ratio was also measured on the in-plane RCA images.

RESULTS: Coronary MRA demonstrated a 23% increase in cross-sectional area after NTG (16.9 ± 7.8 mm² to 20.8 ± 8.9 mm², p < 0.0001), with significant vasodilation between 3 and 15 min after NTG on time-course analysis. The MRA measurements had low interobserver variability (5%) and good correlation with X-ray angiography (r = 0.98). The magnitude of vasodilation correlated with baseline cross-sectional area (r = 0.52, p = 0.03) and age (r = 0.40, p = 0.019). Post-NTG images also demonstrated a 31% improvement in coronary signal-to-noise ratio (p = 0.002).

CONCLUSIONS: Nitroglycerin-enhanced coronary MRA can noninvasively measure coronary artery vasodilation and is a promising noninvasive technique to study coronary vasomotor function.

Abbreviations and Acronyms   CAD = coronary artery disease   MRA = magnetic resonance angiography   MRI = magnetic resonance imaging   NTG = nitroglycerin   RCA = right coronary artery   ROI = region of interest   SNR = signal-to-noise ratio   Tx = post-transplant   XRA = X-ray coronary angiography

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