Successful Percutaneous Implantation of an Aortic Valve Stent Prosthesis in a Patient with a Mechanical Mitral Valve

Case Report. A 70-year-old female patient with symptomatic aortic stenosis (jet velocity, 5.8 m/sec; aortic valve area, 0.6 cm²) presented for aortic valve replacement. Ventricular function was normal (ejection fraction, 62%) and the aortic annulus had a diameter of 20.5 mm as assessed in transesophageal echocardiography. The patient had undergone open commissurotomy for treatment of rheumatic mitral stenosis in 1969. Due to valve insufficiency in combination with restenosis, she had received a mechanical mitral valve replacement (Björk-Shiley-Prosthesis 25 mm) in 1983. Actual cardiac catheterization proved absence of coronary artery disease, but revealed significant pulmonary hypertension (mean pulmonary artery pressure, 68 mmHg). Operative aortic valve replacement was discussed between the responsible cardiologists and cardiac surgeons. The patient was rejected by the surgeons due to a high perioperative risk (Log. EuroSCORE = 20.63%) and the patient’s refusal to accept blood transfusions as one of Jehovah’s Witnesses, and in consensus a decision for an interventional approach was made. Oral anticoagulation was discontinued and replaced by intravenous weight-based unfractioned heparin for prevention of valve thrombosis. General anesthesia was induced to ensure immobility during the intervention.

A 24 French sheath was placed in the right femoral artery. Special attention was paid to secure placement of the ultra-stiff guidewire (Amplatz) in the left ventricle, avoiding any interaction with the mechanical valve prosthesis. During rapid pacing, a 23 mm Edwards-Sapien stent bioprosthesis was implanted in aortic position with special attention to the coronary ostia and the ring of the mechanical mitral valve after previous valvuloplasty with a 20 mm balloon. Correct positioning was controlled by biplane fluoroscopy and transesophageal echocardiography. The angiographic result was excellent (Figure 1).

The patient was extubated without complication 12 hours post-intervention. There was no access-site hematoma, aneurysm, or any other complications. Post-interventional echocardiography showed the implanted aortic valve with a good functional result (peak gradient, 32 mmHg), although there was a central aortic regurgitation. Figure 2 shows the position of the valve in transesophageal echocardiography.

Function of the mitral valve prosthesis was unaltered. The patient developed a HIT syndrome (heparin-induced thrombocytopenia) after the intervention; therefore, lepirudin was used as an alternative anticoagulant until platelet counts were normalized and oral anticoagulation with coumadin had reached effective levels again. The patient was discharged from our clinic with a very good functional result. New York Heart Association class had improved from Class III to I, and the patient no longer complained of chest pain.

Discussion. Valvular aortic stenosis is present in 2–4% of elderly patients in Western countries, and a further increase can be predicted because of the aging population.¹ National registries show that aortic valve disease is the second most common indication for cardiac surgery after coronary artery bypass grafting, and that by now almost half of the patients submitted to cardiac surgery are older than 70 years of age.² An increasing number of reoperations in elderly and high-risk patients can be expected in the forthcoming years, but redo operations still present a relevant risk factor in cardiac surgery.^3,4 Percutaneous aortic valve replacement represents an attractive alternative to operative valve replacement in high-risk patients.⁵ However, patients with mechanical valves so far have been excluded from this procedure, as there are concerns regarding a possible interference between the percutaneous aortic valve and the mitral valve prosthesis. We chose an Edwards valve because of the relatively short stent segment to minimize this risk. Apart from this reason, as in mechanical mitral valves a strict anticoagulation is needed anyway, normally another mechanical valve, and not a transcatheter bioprosthesis would be chosen.

In our case, the bleeding risk of a third open-heart operation was estimated to be extremely high, and as the patient refused any kind of blood transfusion, a decision for transcatheter aortic valve implantation was made by the treating surgeons and cardiologists. Percutaneous aortic valve implantation may mechanically alter the mitral ring by eccentric compression, which may result in aggravation of mitral insufficiency in native mitral valves. This patient had a 25 mm Björk-Shiley-Prosthesis that can only work properly in the absence of any mechanical compression of the ring which would otherwise alter the opening forces. The hinges are relatively sensitive to any mechanical interaction (like wire during implant, or stent frame). Thus, not only the type but also the geometric position of the mitral valve prosthesis has to be taken into account for this kind of intervention.

The placement of the aortic valve was performed with special attention to the mitral valve position and function. Regarding the sizing of the aortic valve, in spite of an annulus diameter of 20.5 mm, a relatively small 23 mm Edwards Sapien prosthesis was chosen, which is not only smaller in diameter but also in height. The lower height is preferable for prevention of mechanical interaction of the mechanical leaflet and the stent frame. In case of diameter undersizing, a better expansion might be achieved by adding 1 cc in the indeflator syringe. For these reasons, slightly smaller valves might be more suitable for this special indication.

The good result in our case encourages percutaneous valve replacement as an option even in patients with mechanical valves, if there are special high-risk situations present.

References

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