Background and aim of the study: The in-vivo performance of the Triflo trileaflet mechanical valve was evaluated in an ovine model. The aim of long-term follow up was to gather site-specific performance data demonstrating device safety, as required for regulatory approval of this new valve design, prior to its use in clinical trials.
Methods: The Triflo trileaflet valve was implanted in 26 sheep using 29-mm mitral (n=8; animal body weight 63.3 +/- 10.3 kg, age 112.0 +/- 30.7 weeks) or 21-mm aortic mechanical valves (n=19; body weight 73.0 +/- 4.36 kg, age 112.6 +/- 23.6 weeks) using standard techniques. Animals were allocated to 150- or 365-day survival cohorts. The 150-day cohort was further subdivided into mitral valve (n=6) and aortic valve (n=11) implants. The 365-day cohort was organized into aortic (n=7) and mitral (n=2) implants. Angiography, echocardiography, and pathology were performed to assess valve performance.
Results: Angiographically monitored pressure measurements for the trileaflet mitral valve at 150 and 365 days were within established ranges in terms of mean aortic pressure, systolic and diastolic aortic pressure, and left ventricular end-diastolic pressure. In animals receiving a mitral valve the transvalvular gradient was 3.5 +/- 0.71 mmHg at 365 days, and 0.2 +/- 0.4 mmHg at 150 days. The Triflo mitral valve had only mild (physiologic) regurgitation. Cardiac output was within normal limits in animals receiving the Triflo valve in the aortic position. Laboratory values reflected no ongoing infection or destruction of blood cells as a result of device implantation. No significant abnormality was noted at necropsy in any animal, except for evidence of thromboembolic events in the kidneys (4-20%). Pathological evaluation was reflected by mild to moderate fibrous tissue formation at the inflow orifice (n=15), and minimal growth was observed in the outflow tract of one valve. This was consistent with that seen in sheep implanted with a standard St. Jude Medical bileaflet valve.
Conclusion: The study results showed the Triflo valve to perform to safety levels comparable with those of the standard St. Jude Medical bileaflet design, when implanted in the aortic and mitral positions. Additional analysis of historic control data suggested that the trileaflet valve design may offer a reduction in outflow tract obstruction by allowing for a greater effective orifice area index when compared to an equal-sized-orifice bileaflet valve. Notably, the Triflo valve was associated with a statistically significant reduction in myocardial hypertrophy, further reducing the potential for patient-prosthesis mismatch. Overall, the Triflo valve appeared to more closely emulate the hemodynamic properties of the native tissue valve than the traditional bileaflet design. Hence, the trileaflet design may offer the function of a tissue valve while retaining the durability of the mechanical valve.