Homograft

An aortic homograft is a human donor aorta complete with its aortic valve. Pulmonary homografts are the pulmonic equivalent. The first aortic homografts used as true aortic valve replacements were implanted in 1962 by Donald Ross in London and Sir Brian Barrett-Boyes in New Zealand.

In terms of structure and compatibility, the homograft is the intuitive choice when looking for the next best thing to the living human valve. The homograft opens fully, closes tightly, and does not affect the blood cells. Initially, there were problems with quality assurance, sterility, measuring, storing, and protecting donor valves from deterioration as well as the obvious problem of a limited supply. In addition to these “logistical” problems, the challenge for surgeons was to implant the valves safely (without excessive bleeding) and so they would function properly (without regurgitation).

Initially, Ross and Barrett-Boyes described what is called the freehand subcoronary technique. This trims the aortic wall from around the valve leaflets leaving just a little edge allowing the valve to be sewn in with two rows of stitches. The first row was on the inflow (left ventricular) side at or below the level of the native annulus. The second was just above the leaflets tacking the edge of residual donor aortic wall into the patient’s aortic wall in a triple parabola fashion running underneath the coronary artery openings and up over the native commissures.

The subcoronary technique proved a geometrical challenge to many surgeons, often resulting in a high rate of regurgitation. Replacing the aortic root, substituting the donor aorta and valve for the patient’s, was proposed and used by Donald Ross and Sir Magdi Yacoub as early as 1972. They used this technique in patients whose aortic roots were too diseased to leave behind. Serendipitously, this turned out to have a distinct advantage in preventing regurgitation but raised the risk of bleeding from the exposed suture lines under high pressure.

Long term studies have shown the full root replacement technique to demonstrate better durability  than the subcoronary with less regurgitation.  This technique also lends itself to treatment of serious infections (endocarditis) of the aortic root.

The data from Mark O’Brien from Brisbane, Australia, show an actuarial freedom from reoperation of 62% at 20 years with the cryo-preserved aortic homograft.