When conventional valve surgery is too high risk
Date: June 13, 2011
Revival of an apical conduit fills a rare niche
Patients who are unable to have conventional valve repair or replacement surgery are left with few options. Michael Junker, 34, a former postal carrier from Pittsburgh, Pa., faced that dilemma. He had rheumatic fever as a child that damaged his aortic valve. It was replaced with a homograft valve in 1996. Eight years later, that valve became blocked and Junker had to have his aortic root enlarged and replaced entirely with a mechanical valve conduit.
However, in 2008, valve stenosis developed once again and Junker was referred to Hopkins cardiac surgeon John Conte. “We knew that a third conventional valve replacement surgery was out of the question because it would be too risky,” says Conte. “So we offered him an apical aortic conduit in which we attach a Dacron tube graft that contains a mechanical valve. The conduit is attached from the tip of the left ventricle to the descending thoracic aorta to provide an alternative route for blood to leave the heart.”
Junker is doing fine and says he is grateful that there was another option for him.
“With the development of routine aortic valve replacements that give good results for our patients, we stopped using the apical aortic conduit approach that was developed in the early days of cardiac surgery. It was revived about 10 years ago when we started to see patients who could not safely undergo standard valve replacements, mainly because of their anatomy,” says Conte.
Apical conduit surgery is now considered only for patients in special circumstances, like Junker’s, or those who previously had bypass surgery and were left with bypasses close behind the breastbone that would be at risk of injury with the conventional valve replacement. Other potential candidates include patients who had an infection after previous heart operations, as well as some patients who have so much calcification in their aorta that it would be too risky to clamp it for the operation.
However, these same patients may one day benefit from a minimally invasive approach that is used widely in Europe and is being studied in the United States. Transcatheter aortic valve implantation (TAVI) is an approach for placing an aortic valve without opening the chest. Conte and his Hopkins cardiology colleague Jon Resar are taking part in one of the two major TAVI studies. Their trial involves the use of a porcine valve encased in a stent that is fed through the femoral artery to the heart. Before the new valve is deployed at the site of the existing diseased valve, a balloon is opened inside the old valve to push away the blockage and make room for the replacement valve.
Patients are eligible for the study if they are at high risk for conventional surgery because of advanced age, previous procedures or comorbidities. They are randomized to receive either the transcatheter approach or surgical valve replacement. A second group of patients for whom surgery is totally ruled out will receive the percutaneous approach.