Ventricular Restraint Prevents Infarct Expansion and Improves Borderzone Function After Myocardial Infarction: A Study Using Magnetic Resonance Imaging, Three-Dimensional Surface Modeling, and Myocardial Tagging

Abstract

Infarct expansion is associated with impaired borderzone function, adverse remodeling, and poor long-term prognosis. We hypothesized that left ventricular restraint early after myocardial infarction limits infarct expansion, preserves borderzone function, and reduces remodeling. We used an ovine model as well as high spatial and temporal resolution cardiac magnetic resonance imaging to quantify total and infarcted left ventricular epicardial surface area at baseline and 1 week and 12 weeks after anterior wall infarction in 10 animals. Five animals were randomly assigned to treatment with left ventricular restraint (Acorn cardiac support device) 1 week after infarction. Five animals were untreated controls. Total left ventricular surface area was measured by importing the end-diastolic magnetic resonance imaging-derived epicardial contours into custom software, which creates a three-dimensional surface from the two-dimensional magnetic resonance imaging contours. Infarct area was calculated from magnetic resonance imaging-detectable titanium markers placed at the infarct border. Borderzone radial and circumferential strains during systole were also assessed using myocardial tagging techniques as a measure of contractile function. The infarct area 1 week after infarction was 1,177 +/- 386 mm(2) in the control group and 1,124 +/- 427 mm(2) in the cardiac support device group. After 12 weeks, infarct area was 3,666 +/- 1,013 mm(2) in the control group and 1,227 +/- 301 mm(2) in the cardiac support device group. Borderzone systolic radial strain decreased from 12.6% +/- 0.77% to 3.6% +/- 0.3% after infarction in the control group and 13.7% +/- 0.87% to 4.7% +/- 0.3% in the cardiac support device group. At 12 weeks after infarction, radial strain was 3.4% +/- 0.5% in the control group and 6.7% +/- 0.4% in the cardiac support device group. Early postinfarction left ventricular restraint limits infarct expansion and improves borderzone contractile function.