Aortic Valve Replacement with a Homograft Valve
Aortic regurgitation (AR) is the diastolic reflux of blood from the aorta into the left ventricle due to failure of coaptation of the valve leaflets at the onset of diastole. In terms of the cause of aortic regurgitation, is often due to the aortic root dilation, which is idiopathic in over 80% of cases. Aortic root dilation is the most common cause of aortic insufficiency in developed countries. AR can be also caused by primary disease of the aortic leaflets, such as calcific degeneration, myxomatous degeneration, infective endocarditis, rheumatic disease, a bicuspid AV, or some medications. Its presentation varies depending on the acuity of onset, severity of regurgitation, compliance of the ventricle and aorta, and hemodynamic conditions present at the time. The pathophysiology and clinical presentation of AR varies according to the onset and duration of the disease process. Acute AR can be debilitating and life threatening if not treated urgently,, whereas chronic AR is usually well tolerated for years. Patients with chronic, compensated AR remain asymptomatic for prolonged periods of time while the left ventricle gradually enlarges. Symptoms of heart failure usually develop gradually only after considerable ventricular hypertrophy and decompensation. Echocardiography is the most useful diagnostic modality in both the initial diagnosis and continued monitoring of patients with AR. A common test for the evaluation of severity is transthoracic echocardiography, which can provide two-dimensional views of the regurgitant jet, allow measurement of velocity, and estimate jet volume. Aortic insufficiency or aortic regurgitation can be treated either medically or surgically, depending on the acuteness of presentation, the symptoms and signs associated with the disease process, and the degree of left ventricular dysfunction. Surgical options for AR are AV repair and AV replacement. 65,000 aortic valve replacements (AVR) are performed in Europe every year to treat acquired and congenital aortic valve disease (both AS and AR). Current AVR options are, however, limited for young patients - especially female patients - and those unwilling to accept life-long medical anticoagulation with its inherent risks. The ARISE project is a European multi-center study evaluating the safety and efficacy of decelullarized aortic valve homografts produced through a novel decellularization protocol, and funded by the European Commission within the Horizon-2020 initiative. ARISE will bridge this therapeutic gap in a clinical study to determine the feasibility, safety and efficacy of regenerative heart valves for aortic valve replacement. The aortic valve or the full aortic root can be replaced using an aortic homograft. Tissue engineering concepts have led to decellularization which lyses cells and “rinses” out antigenic proteins, leaving an inert matrix and intact structural framework, which preserves its mechanical properties. In addition, the empty matrix seems to attract circulating recipient stem cells which repopulates the framework and differentiates into appropriate cell lines capable of maintaining the matrix. The initial use of the decellularized aortic homograft in humans demonstrated that structural integrity could be maintained with low, stable gradients and minimal regurgitation similar to standard cryopreserved homografts. Long-term studies are needed to determine if native cell ingrowth occurs reliably.
