One-hundred and twenty patients undergoing elective aortic valve replacement were entered in this prospective evaluation. Dependent on their age, they were allocated into tree groups. Patients in group I were less than 55 years of age and were randomized to receive either a mechanical (Edwards Mira, n = 20) or a pulmonary autograft (n = 20). Patients in group II were between 55-75 years old and were randomized for a stentless bioprosthesis (CE Prima Plus, n = 20) or a mechanical valve (Edwards Mira, n = 20). Patients in group III were above the age of 75 years and were randomly assigned to a stentless bioprosthesis (CE Prima Plus, n = 20) or a stented bioprosthesis (CE Perimount, n = 20). All patients underwent preoperative and postoperative transthoracic echocardiography (at discharge, 6 and 12 months) for functional and structural assessment. All clinical and echocardiographic data describing this population were prespecified and collected postoperatively. A valvular database, provided by Edwards Lifesciences, was used to collect preoperative, perioperative and postoperative patient information. The study protocol was approved by our institutional ethics review board. All patients provided written informed consent before entering the study.
The choice of valve prosthesis was made preoperatively and feasibility of implantation was confirmed intraoperatively. Severe calcification of the aortic root diagnosed intraoperatively, very low position of coronary ostia in relation to the annulus and atypical insertion of the coronary ostia made it impossible to implant stentless valves or pulmonary autografts.
Preoperative transthoracic echocardiography was used to identify patients in whom the use of stentless valves and pulmonary autografts seemed safe. The sizes of both the native aorta and at the level of the sinotubular junction and the annulus were measured. If the diameter of the annulus was found to be larger than or less than the size of the sinotubular junction by more than 2 valve sizes (i.e. 4 mm), patients were excluded from the study. Patients with a subvalvular pressure gradient, active endocarditis and the need for concomitant valvular surgery were similarly excluded from enrolment.(Figure 1)
Access to the heart was gained via median sternotomy. Standard extracorporeal circulation with moderate hypothermia (28°C) was used. All patients had antegrade and retrograde cold blood cardioplegia and carbon dioxide insufflation of the open thorax for organ protection.
All pulmonary autograft procedures were performed as root replacements with implantation of the coronary arteries on the graft. Reconstruction of the right ventricular outflow tract was performed with cryopreserved pulmonary valve homografts in all patients.
The Prima Plus stentless bioprosthesis were implanted in the subcoronary position. The aortic valve was exposed via a transverse aortotomy. After resection of the native aortic valve and debridement of the aortic annulus, accurate sizing was carried out using the respective seizers. The commissures were positioned 120° apart with the muscular shelf corresponding to the right coronary sinus. Single interrupted unpledgeted 4-0 Ethibond sutures were used for the proximal end and the rims of the valve commissures were sutured to the native aorta using 4-0 polypropylene running sutures.
For the Mira mechanical aortic valves and the Perimount stented bioprosthesis access to the aortic valve was gained via a hockeystick aortotomy. The valves were implanted in the supraannular position. Interrupted mattressed pledgeted 2-0 Ethibond sutures were placed circumferentially from below the annulus. Mechanical valves were oriented in the antianatomical position.
Two experienced operators performed all echocardiograms for the study on a standard machine (System Five, Sonotron Vingmed). Cardiac morphology and function as well as hemodynamic parameters were assessed. All hemodynamic measurements were performed with patients in stable conditions. Aortic valve flow velocities were assessed with continuous wave Doppler. End diastolic left ventricular posterior wall thickness > 12 mm was considered hypertrophied. Aortic valve incompetence was judged as transvalvular or paravalvular and graded according to the regurgitant jet area in relation to left ventricle as mild, moderate or severe. Apart from standard imaging views, preoperative echocardiography also included the measurement of the diameter of the native aortic annulus and the sinotubular junction as well as the assessment of subvalvular gradients, in order to identify a possible mismatch between annulus and sinotubular junction or excessive subvalvular hypertrophy. Both conditions would render the patient unsuitable for the study.
Follow up examinations were scheduled for discharge from the hospital, at six and 12 months postoperatively. All patients were subject to detailed clinical and echocardiographic follow-up. This included the New York Heart Association functional class (NYHA), blood data including signs of haemolysis, anticoagulation profile, assessment of cardiac rhythm and blood pressure and documentation of occurrence of early and late complications.
In echocardiography follow-up, our special attention was focused on the regression of LV-hypertrophy. Both completeness and rate of LV-mass regression ware assessed. In addition, changes in LV-function and hemodynamics including effective orifice area (EOA), as well as changes in postoperative transvalvular gradients were analyzed.
Our anticoagulation regime was as follows. Patients with pulmonary autografts did not receive oral anticoagulation. Patients with bioprosthesis had oral anticoagulation for 3 months and patients with mechanical valves had lifelong anticoagulation.
Our protocol included subcutaneous low molecular heparin for the first day and parallel oral anticoagulation with vitamin K antagonists. As soon as the International Normalized Ration (INR) levels reached the therapeutic target range of 2.5 - 3.5, the heparin was discontinued. Initially, oral anticoagulation was monitored by the patient's general practitioners. However, most patients who received mechanical valves soon attended a structured course on oral anticoagulation self management, and henceforth monitored their own INR levels, using the portable CoaguCheck™ (Roche Diagnostics) device.
All data were compiled and analyzed using Microsoft Access, Microsoft Excel (Redmont WA) and StatView (Cary, NC). The baseline characteristics and hospital outcomes for the two groups were compared using chi-square or Fisher's exact test for categorical data and unpaired t-tests for continuous variables. Results are reported as mean ± standard deviation in text and tables. Statistical significance was defined as a p value less than 0.05.