Author: Patricia Bandettini
Publish Date: 11/1/2017
Indications and purpose of the scan
- In patients with need for assessment of left ventricular ejection fraction, cardiovascular magnetic resonance (CMR) provides an accurate and reproducible test for measuring left ventricular masses, volumes, and ejection fraction.
- Some common indications include:
- New onset heart failure
- Acute myocardial infarction
- Assessment for implantable cardioverter defibrillator
- Evaluation of regurgitant valvular lesions
- Able to be performed without contrast, a simple CMR exam to assess for left ventricular mass, volumes, and ejection fraction can be performed quickly in less than 10 minutes. Often using a series of short breath-holds, gated cardiac images are acquired over multiple phases of the cardiac cycle and reconstructed into a “cine” movie. Images are typically acquired volumetrically in short-axis through the entire left ventricle, as well as in long-axis views. Left ventricular ejection fraction is calculated using the Simpson’s method of multiple disk-derived measurements. While left ventricular size and systolic function assessment may be performed alone, left ventricular cine images may also be combined with additional CMR imaging components like pharmacologic stress testing or late gadolinium enhancement to provide additional information such as ischemic burden, myocardial viability, or location of scar for cardiac resynchronization therapy planning.
WHY CMR (Specific Advantages)
- A standard CMR-derived left ventricular ejection fraction is calculated using volumetric coverage of the left ventricular chamber and is not dependent on geometric models, resulting in highly accurate and reproducible data of not just the ejection fraction but also left ventricular volumes and masses1-4; the diagnostic accuracy and reproducibility performance of CMR is superior to that of echocardiography. The low inter- and intraobserver variability of left ventricular ejection fraction calculation allows for confidence in comparison of serial studies.
- The procedure is non-invasive, involves no exposure to ionizing radiation, and can be easily performed without contrast.
- The issues of poor image quality due to poor echocardiographic windows is not an issue in CMR in which high quality images may be obtained in patients of diverse body habitussen.
- In patients with decreased left ventricular systolic function of unknown etiology, other components of a CMR exam may be helpful in elucidating the cause.
Evidence examples from the literature
- Bellenger and colleagues examined the reproducibility of CMR-derived left ventricular masses, volumes, and ejection fraction in 20 heart failure patients and 20 controls and compared them to published echocardiography values, finding that the use of CMR demonstrated low inter and intra-observer variability and significantly decreased the sample size number required to treat to see a 10-mL difference5.
- Joshi and colleagues demonstrated the potential clinical impact of using CMR to calculate ejection fraction when they compared ejection fraction calculated by CMR and by echocardiography in 52 patients undergoing assessment for implantable cardioverter defibrillator placement. CMR resulted in 11 of 52 (21%) and 5 of 52 (10%) of patients being reclassified from the echocardiographic-determined categories regarding implantable cardioverter debrillator eligibility at the ejection fraction thresholds of 35 and 30% respectively3.
- Any implanted device that is not MRI conditional
Inability to lie flat
- Inability to tolerate the scan
- Altered mental status/ inability to follow verbal commands in scanner
- Severe arrhythmias
- From the 2006 consensus document of appropriate use criteria:
- Bellenger NG, Burgess MI, Ray SG, Lahiri A, Coats AJ, Cleland JG, Pennell DJ: Comparison of left ventricular ejection fraction and volumes in heart failure by echocardiography, radionuclide ventriculography and cardiovascular magnetic resonance; are they interchangeable?. Eur Heart J. 2000, 21: 1387-1396.
- Grothues F, Smith GC, Moon JC, Bellenger NG, Collins P, Klein HU, Pennell DJ: Comparison of interstudy reproducibility of cardiovascular magnetic resonance with two-dimensional echocardiography in normal subjects and in patients with heart failure or left ventricular hypertrophy. Am J Cardiol. 2002, 90: 29-34.
- Hoffmann R, von Bardeleben S, ten Cate F, Borges AC, Kasprzak J, Firschke C, Lafitte S, Al-Saadi N, Kuntz-Hehner S, Engelhardt M: Assessment of systolic left ventricular function: a multi-centre comparison of cine ventriculography, cardiac magnetic resonance imaging, unenhanced and contrast-enhanced echocardiography. Eur Heart J. 2005, 26: 607-616.
- Myerson SG, Bellenger NG, Pennell DJ: Assessment of left ventricular mass by cardiovascular magnetic resonance. Hypertension. 2002,39:750-755
- Bellenger NG, Davies LC, Francis JM, Coats AJS, Pennell DJ. Reduction in sample size for studies of remodelling in heart failure by the use of cardiovascular magnetic resonance. JCMR. 2000, 2:271-278.
- Joshi SB, Connelly KA, Jimenez-Juan L, Hansen M, Kirpalani A, Dorian P, Mangat I, Al-Hesayen A, Crean AM, Wright GA, Tan AT, Leong-Po H: Potential clinical impact of cardiovascular magnetic resonance assessment of ejection fraction on eligibility for cardioverter defibrillator implantation. JCMR. 2012,14:69.
- ACCF/ACR/SCCT/SCMR/ASNC/NASCI/SCAI/SIR 2006 Appropriateness Criteria for Cardiac Computed Tomography and Cardiac Magnetic Resonance Imaging. JACC. 2006, 48:1475-97.