Assessment of myocardial perfusion-CMR in left main stem disease (LMS) in the CEMARC study
© Zaman et al; licensee BioMed Central Ltd. 2011
Published: 2 February 2011
Left main stem (LMS) disease is found in approximately 5% of patients with stable angina and in approximately 7% of patients presenting with an acute myocardial infarction. Accurate assessment of the degree of left main stem stenosis has important prognostic and therapeutic implications. Clinically, angiographic LMS stenosis of 50% or more is considered significant. However, it is not known how accurately myocardial perfusion imaging detects LMS disease at this severity threshold.
To measure myocardial blood flow by CMR in patients with LMS stenosis of more than 50% on quantitative angiography in the CEMARC study (a large prospective evaluation of CMR against SPECT and coronary angiography1).
To correlate hyperaemic myocardial blood flow (MBF) and blood flow reserve between territories supplied by the LMS and remote territories.
Nine patients from the CEMARC study who were found to have significant LMS disease on quantitative coronary angiography underwent perfusion-CMR on a Philips 1.5 T Intera system. Myocaridal perfusion imaging was performed every heartbeat during the first pass of 0.05 mmol/kg gadolinium chelate using a T1-weighted fast (spoiled) GE sequence. Stress perfusion imaging was performed using intravenous adenosine infused for 4 minutes (140mcg/kg/min). Perfusion-CMR data were post-processed off-line using the software PMI2. Following motion correction a circular ROI was selected in the left ventricle to measure the arterial input function. MBF maps were created by model-free analysis; myocardial ROIs were drawn on these maps, one in the LMS territory (ROI1: LAD+LCX) and one in a remote region (ROI2:RCA). MBF for these ROIs was calculated using the Fermi model3. Statistical calculations were performed using SPSS.
This study demonstrates reduced myocardial blood flow reserve in patients with LMS stenosis of 50% or more, although reductions are subtle.
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