Circulatory benefits of diastolic counterpulsation in an ischemic heart failure model after aortomyoplasty

Objective: Aortomyoplasty is an experimental surgical procedure in which the latissimus dorsi muscle is wrapped around the thoracic aorta and stimulated to contract during diastole, providing diastolic counterpulsation. We hypothesized that aortomyoplasty could improve cardiac function in a chronic ischemic heart failure model, similar to the improvement seen with the intra-aortic balloon pump. Methods: Six dogs (25-30 kg) successfully underwent aortomyoplasty followed by serial coronary microembolization. Ejection fraction decreased from 63.5% to 36.5%. Two weeks after the final microembolization, the muscle was conditioned for 4 months to achieve fatigue resistance. One year after aortomyoplasty, hemodynamic studies during 1 hour of aortomyoplasty and 1 hour of intra-aortic balloon counterpulsation determined mean diastolic aortic pressure, peak left ventricular pressure, and endocardial viability ratio for assisted and unassisted beats. Cardiac output, stroke volume, and parameters of cardiac function were also measured. Results: Endocardial viability ratio increased by 23.8% ± 7.9% (P = .001) with aortomyoplasty counterpulsation and by 22.7% ± 12.9% (P = .021) with the intra-aortic balloon pump. Both aortomyoplasty and the intra-aortic balloon pump significantly increased mean diastolic aortic pressure and reduced peak left ventricular pressure. Improvements in cardiac function with aortomyoplasty and the intra-aortic balloon pump were similar. Cardiac output increased from 2.61 ± 0.88 to 3.07 ± 1.06 L/min (P = .006), and index of afterload decreased from 5.4 ± 1.4 to 4.8 ± 1.4 mm Hg/mL (P = .02) during 1 hour of aortomyoplasty counterpulsation. Conclusion: One year after the procedure, aortomyoplasty counterpulsation provided diastolic augmentation and improved cardiac performance similar to the improvement provided by the intra-aortic balloon pump in a chronic ischemic heart failure model. Aortomyoplasty has the potential to benefit patients with ischemic heart disease refractory to current therapies.