Keywords
aortic valve - heart valve replacement - transapical - transcatheter aortic valve
implantation
Introduction
Bioprosthetic heart valves have been used since the early 1970s with excellent hemodynamic
results. However, it is commonly known that the durability of bioprosthetic valves
decreases with time, particularly when implanted in younger patients.[1] The need for long-term anticoagulation is minimized, and although the durability
of bioprostheses is a limiting factor in long-term evaluation, tissue degeneration
is usually progressive and symptomatic, thereby permitting detection during proper
annual follow-up examinations. In the present case, a Carpentier − Edwards bioprosthesis,
model 2650, was used. The prosthesis was made of porcine aortic valves that have been
preserved in buffered glutaraldehyde and then mounted on flexible frames.
Case Description
We report on a 47-year-old man, who underwent aortic valve replacement in 1984 at
the age of 21 years due to aortic isthmus stenosis combined with a valve insufficiency.
First, the aortic isthmus stenosis was corrected by a patch plasty via a posterolateral
thoracotomy and then the aortic valve was replaced with a 25-mm Carpentier − Edwards
bioprosthesis via a median sternotomy. Postoperatively, the patient was put on oral
anticoagulation with phenprocoumon for 3 months.
Twenty-six years later, in 2010, the patient developed increasing angina pectoris
and progressive exercise distress. Echocardiography revealed high-grade stenosis of
the implanted bioprosthesis. Using coronary angiography, relevant coronary artery
disease could be precluded. Although there was a strong adhesion between the heart
and the posterior sternal lamina, the reoperation was performed without complications
by replacing the stenotic bioprosthesis with a 23-mm mechanical valve prosthesis.
The patient left intensive care unit on day 1 after surgery and was discharged from
hospital on day 10 after surgery.
After explantation, the highly degenerated bioprosthesis was sent to Edwards Lifesciences
Product Evaluation Laboratory (Irvine, California, United States) for thorough investigation.
The evaluation involved gross visual examination and X-ray ([Fig. 1]).
Fig. 1 Half of the noncoronary and half of the left coronary leaflet were missing due to
tissue cut. Calcification was heavy in the rest of the left coronary leaflet, moderate
in the right coronary leaflet, and minimal in the remaining tissue of the noncoronary
leaflet. Calcification restricted the leaflets mobility and led to stenosis. Host
tissue overgrowth was heavy at the stent outflow. The X-ray demonstrated calcification.
Calcification is a well-recognized failure mode of bioprosthetic valves. The mechanisms
of calcification are not fully understood. Host tissue/pannus growth is a complex
process triggered by the interaction between the host and the device and is highly
variable among patients. It is not currently possible to predict the occurrence and
severity for any given patient with a bioprosthetic heart valve. However, abnormal
or severe pannus growth can eventually affect the function of the valve.
Discussion
Although reoperations for aortic valve replacement do not have higher mortality than
first operations, the valve of choice for young patients with degenerative aortic
valve disease is usually a mechanical type.[2] According to the valve guidelines of the ACC/AHA of 2010, mechanical valves must
be treated with phenprocoumon for the rest of the life. Side effects of permanent
anticoagulation involve increased risk for serious bleeding (0.4–2.4%/patient/year)
or thromboembolic events (0.5–4.4%/patient/year).[3]
[4]
[5] Patient's age at the time of implantation is still the most important determinant
of structural prosthetic valve deterioration[1]
[6]: for patients 60 years and older, event-free life expectancy is superior with a
bioprosthesis. While the chance of reoperation is greater, the lifetime risk of bleeding
is lower compared with a mechanical prosthesis.[7]
[8]
[9]
Our patient had no valve-associated complication and was free of symptoms for 26 years,
in which he could live without the risks of a permanent anticoagulation therapy. Especially
in young patients, with an active lifestyle or in woman planning pregnancy, the decision
about the best replacement procedure and therapy concept is still matter of debate.
As an alternative to prosthetic heart valve replacement (biological or mechanical)
in young patients, in the Ross operation, the diseased aortic valve is replaced with
the patient's own pulmonary valve and a pulmonary homograft is used to replace the
patient's own pulmonary valve. One of the advantages of this procedure is the freedom
from thromboembolism without the need for anticoagulation. Moreover, the valve seems
to grow while the younger patient grows and has favorable hemodynamics in the absence
of foreign valve material. Sievers et al achieved excellent midterm and long-term
results after Ross procedures, including normal survival and low risk of valve-related
morbidity.[10]
[11] Further long-term follow-up studies are needed to get more certainty in this question.
It is noteworthy that autologous heart valve replacement is not a curative procedure
being associated with several complications. Patients have to understand and accept
the risks, and honest and open explanations should be provided to them because at
the end, the patients are taking all the risks. Hence, bioprosthetic valves feature
an effective and reasonable alternative to allografts and pulmonary autografts in
aortic position implanted in carefully selected patients.[12]
[13]
The concept of implanting bioprostheses is supported by techniques such as the transcatheter
aortic valve implantation, which provides a lower risk for reoperation via a transfemoral,
transapical, or transaortic approach (valve-in-valve technique) using the metal ring
of the implanted bioprosthesis as an anchor. It is conceivable that this concept is
a good alternative even in young and middle-aged patients, especially when bioprostheses
with a low risk of structural valve deterioration are employed.
When propagating long lasting bioprosthetic heart valve types, the question arises
why we did not do this in this patient? On the one hand, in case of future reoperation,
the minimal invasive valve-in-valve technique is highly promising and could justify
implanting another bioprosthesis, but on the other hand, choosing a mechanical valve
might help to prevent future surgical procedures. Our patient decided for a mechanical
valve accepting its pros and cons.
