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Procedure May Fix Thin Ventricle Walls

Mon, 03/11/2013 - 11:29am

Revascularization may resolve thinning of left ventricular walls in patients with coronary artery disease (CAD) who have only limited scarring, researchers found.

The extent of scarring along thinned walls was inversely associated with regional (r=-0.72, P<0.001) and global (r=-0.53, P<0.001) contractile improvement among CAD patients who underwent revascularization surgery, according to Raymond Kim, MD, of Duke Cardiovascular MRI Center, and colleagues.

Scar extent was most strongly associated with contractile improvement and reversal of thinning (P<0.001 for both), they wrote online in the March 6 issue of the Journal of the American Medical Association.

Prior research had shown that left ventricular wall thinning was "synonymous with scar tissue" and was likely to lead to chronic myocardial infarction (MI). However, these assumptions were contradicted by "recent case reports incorporating the use of delayed-enhancement cardiovascular magnetic resonance imaging," which showed that even severely thinning walls "may have minimal or no scarring."

To evaluate this contrasting information, researchers measured prevalence of regional myocardial thinning, how often limited scarring occurs in patients with myocardial thinning, and whether the thinned region would see functional improvement following revascularization in patients with limited scarring. Participants included 201 patients with CAD who underwent delayed-enhancement coronary magnetic resonance.

The population consisted of mostly men (79%) with a mean 2.3 CAD risk factors and significant left ventricular dysfunction. Most patients had a history of MI (71%) and electrocardiographic Q waves (67%).

Regional thinning was defined as "the sector in which end-diastolic wall thickness was ≤5.5 mm on the end-diastolic cine frame for each short-axis slice" as seen under imaging. Limited scar burden was defined as scarring of 50% or less of a thinned region.

Regional functional improvement was measured in patients who underwent follow-up imaging after revascularization to measure end-diastolic and -systolic wall thickness.

Mean thinning encompassed 34% of total left ventricular surface area. Scarring among patients with thinning took up a mean 72% of the affected area. Roughly 20% of patients had a limited scar burden and patient characteristics between patients with limited and extensive scar burdens were similar, they wrote.

However, limited scar burden was significantly associated with Selvester score (OR 0.87, 95% CI 0.78 to 0.97, P=0.01), degree of coronary stenosis (OR 1.03, 95% CI 1.00 to 1.06, P=0.03), and end-diastolic wall thickness (OR 1.86, 95% CI 1.12 to 3.12, P=0.02).

Of the total population, 72 patients received revascularization, "which included the coronary artery supplying the thinned region." Of those, 42 received follow-up imaging. Between initial and follow-up imaging, no patient experienced a cardiac event over the mean 116 days.

Among revascularized patients, "only the group with limited scar burden demonstrated contractile improvement in the thinned region" at a mean 2.3 mm (P<0.001) in absolute systolic wall thickening.

An inverse and significant relationship between scar burden and improvement in left ventricular ejection fraction, and scarring and increase in end-diastolic wall thickness, was also seen (P<0.001 for both). End-diastolic wall thickness did not change significantly after revascularization in patients with extensive scarring.

"On a multivariable analysis, scar extent had the strongest association with regional contractile improvement (P<0.001), global contractile improvement (P<0.001), and reversal of thinning (P<0.001)," they noted.

They concluded that these improvements indicated that "myocardial thinning is potentially reversible and therefore should not be considered a permanent state," cautioning that "common clinical characteristics will not be useful in predicting whether thinned regions have limited scar tissue" due to similarities between extensive and low-burden scarring groups.

In an accompanying editorial, Deepak Gupta, MD, Raymond Y. Kwong, MD, and Marc A. Pfeffer, MD, PhD, all of Brigham and Women's Hospital in Boston, noted that the study showed that non-invasive imaging was useful in determining the extent of myocardial scarring, but also pointed out that the study was limited by a lack of clarity regarding whether thinned walls were akinetic. In addition, they said the study was limited by referral and selection bias.

The authors also said their study was limited by missing outcome data.

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