CVUS: Cardiac MR bests echo for post-heart attack patients

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Cardiac MR showed a large, systematic improvement over transthoracic echocardiography in measuring volumes, left ventricular ejection fraction (LVEF) and wall motion abnormality despite moderate inter-modality correlations after a myocardial infarction (MI), according to a study published Aug. 18 in Cardiovascular Ultrasound.

The primary study objective was to compare metrics of LV volumes and global and regional function determined by cardiac MR and echocardiography in patients with recent MI, according to Blake I. Gardner, MD, cardiovascular department at Intermountain Medical Center, Intermountain Healthcare in Murray, Utah, and colleagues.

Their study comprised 47 consecutive patients (70 percent male; mean age, 66 years) with MI within the previous six weeks and scheduled for imaging evaluation that were studied by both echo and cardiac MR within 60 minutes of one another.

Readers were blinded to patient information and investigators compared cardiac MR and echo measures. The researchers made further comparisons between patients and 30 normal controls for cardiac MR as well as between patients and published normal ranges for echo.

The authors reported that measures of volume and function correlated moderately well between cardiac MR and echo (r=0.54 to 0.75), but large and systematic differences were noted in absolute measurements. Echo underestimated LV volumes (by 69 ml for end-diastolic and 35 ml for end-systolic volume), stroke volume (by 34 ml) and LVEF (by 4 percentage points).

Cardiac MR was much more sensitive to detection of segmental wall motion abnormalities, according to Gardner and colleagues. Cardiac MR comparisons with normal controls confirmed an increase in LV volumes, a decrease in LVEF and preservation of stroke volume after MI.

The authors found that cardiac MR also provided superior detection and quantification of segmental function after MI. Serial studies of LV function in individual patients should use the same modality.