Cardiac Unloading With An Implantable Interatrial Shunt In Heart Failure: Serial Observations In An Ovine Model Of Ischemic Cardiomyopathy

Background: Patients with dilated cardiomyopathy often have progressive heart failure with systolic dysfunction, ventricular remodeling and clinical decompensation heralded by elevations of filling pressures. Our hypothesis is that an interatrial shunt device can regulate left atrial pressure and stabilize left ventricular function without overloading the right heart. Methods: Sheep (N = 21) were subjected to repeat coronary microembolization until left ventricular dysfunction with reduced LVEF was documented. After study group assignment, animals were chronically instrumented during thoracotomy. Shunts were implanted in n = 14 and n = 7 were sham controls. Hemodynamic and echocardiographic responses were serially evaluated for 12 weeks. Results: Comparisons at study termination showed improved outcomes with interatrial shunting (LVEF 46 +/- 11% vs. 18 +/- 3%; fractional shortening 19 +/- 6% vs. 6 +/- 1%; ventricular septal thickness 1.2 +/- 0.2 cm vs. 1.0 +/- 0.3 cm; left atrial pressure 14 +/- 3 mmHg vs. 25 +/- 5 mmHg; mean pulmonary artery pressure 24 +/- 4 mmHg vs. 37 +/- 8 mmHg; right atrial pressure 8 +/- 4 mmHg vs. 15 +/- 4 mmHg; LV dP/dt(max) 1515 +/- 391 mmHg center dot s(-1) vs. 879 +/- 333 mmHg-s(-1); LV dP/dt(min) -2116 +/- 569 mmHg center dot s(-1) vs. -1138 +/- 545 mmHg center dot s(-1); p <= 0.03 for all comparisons). These findings were supported by gross pathological observations and there was a survival advantage with shunting (13/14 vs. 4/7 at 12 weeks, p = 0.047). Shunts were small with Qp:Qs 1.2 +/- 0.1 and all devices were patent at necropsy. Conclusion: In an animal model of ischemic cardiomyopathy, interatrial shunting selectively unloaded the left-heart leading to sustained reductions in left-atrial pressure, improved left ventricular performance, preserved inotropic and lusitropic function with blunted remodeling. Secondary pulmonary hypertension was absent and right-sided cardiac pressures and function were preserved.