SAN DIEGO – Patients younger than age 60 who undergo aortic valve replacement may have a worse rate of survival with a pericardial bioprosthesis as opposed to a mechanical aortic valve replacement, results from a single-center study showed.
"There is insufficient evidence to recommend bioprosthetic valves other than in exceptional situations for patients who require AVR [aortic valve replacement] and are younger than age 60," Dr. Alberto Weber said at the annual meeting of the Society of Thoracic Surgeons. "A prospective strict randomization between valve types only, in isolated AVR, and a longer continued echocardiographic analysis of the prosthetic valve areas would help to clarify this conflict," said.
Dr. Alberto Weber
Current American College of Cardiology/American Heart Association guidelines recommend a bioprosthesis (BP) for AVR in patients of any age who will not take warfarin or who have major medical contraindications to warfarin therapy. "In the past decade, there has been a shift toward bioprosthetic use, to the detriment of mechanical valves, but the data on survival are conflicting," said Dr. Weber, a cardiovascular surgeon at Bern (Switzerland) University Hospital.
He and his associates compared overall survival, cardiac-related mortality, and structural valve deterioration in 110 patients who underwent AVR with the Carpentier-Edwards Perimount pericardial bioprosthesis (Edwards) and 110 patients who underwent AVR with a bileaflet mechanical prosthetic (MP) valve (either St. Jude Medical or ATS) at Bern Hospital between 2000 and 2009. All patients were younger than age 60.
The only statistically significant baseline differences between the two groups were age (a mean of 51 years for BP patients vs. 50 years for MP patients) and the need for acute aortic dissection (1.8% vs. 10.9%, respectively).
During the first 30 days of follow-up, the researchers observed a trend toward more interventions for pericardial effusion or bleeding in the MP group, compared with the BP group, but this did not reach significance. There was also a trend toward more atrial fibrillation in the BP group.
During a mean follow-up of 33 months, 13 patients in the BP group died (11.8%), compared with 3 in the MP group (2.7%), a significant difference. After adjusting for potential confounders in multivariate analysis, the researchers determined that patients in the BP group were five times more likely to die, compared with patients in the MP group.
Overall, "most patients died from cardiac-related causes based on medical records," Dr. Weber said. "There was no autopsy data, unfortunately, and one patient in the MP group committed suicide."
The two groups were similar in the rate of bleeding, stroke, reoperation, and endocarditis, but there were significantly more cases of atrial fibrillation in the BP group than in the MP group (12 vs. 2, respectively).
Echocardiography results at 22 months suggested an early onset of structural valve deterioration in the BP group, leading to accelerated occurrence of moderate prosthesis-patient mismatch. "The groups were similar in ventricular remodeling and left ventricular ejection fraction, but results of the effective orifice area index demonstrated that the BP group showed worse results," Dr. Weber said.
Results from a questionnaire that patients filled out postoperatively indicated that 81% had a preference for valve type before surgery, 57% of patients in the BP group were on aspirin, 14% of patients in the BP group were on warfarin, and 96% of patients in the MP group were on warfarin.
Dr. Weber acknowledged certain limitations of the study, including its relatively short follow-up period and the fact that no autopsy data were available. "We wonder if surgeons preferred a biological AVR in patients who looked somewhat sicker," he said. "It could also be that more physically active patients prefer a bioprosthesis."
While survival might be impaired with a bioprosthetic valve as opposed to a mechanical one, he described the rates of morbidity and mortality observed in the BP group as "very acceptable. They were actually comparable with the literature. In fact, the good news is the excellent results of mechanical prostheses in these young patients. This is remarkable."
Dr. Weber said that he had no relevant financial conflicts to disclose.