Fast sutureless implantation of mechanical aortic valve prostheses using Nitinol attachment rings: feasibility in acute pig experiments

Objective: There is a need for fast sutureless implantation of valve prostheses with a better outcome than that of current valved stents. Methods: The suture ring of a St Jude mechanical valve prosthesis (St Jude Medical, Minneapolis, Minn) was replaced by a proprietary non-stent-based attachment ring C made of Nitinol memory metal (Endosmart, Stutensee, Germany) and covered with textile. In acute pig experiments, the aortic valve was removed and the device was introduced in a temporary stretched shape and activated by removing constrainers and heating to reach its final attachment shape. Results: The devices could be actuated within seconds. Echocardiography showed normal prosthetic valve and heart function. No paradevice leakage was demonstrated by supravalvular angiography. At autopsy, no abnormalities were found in the surrounding structures or valve prostheses. Pulling tests showed the strong adhesive power of Nitinol attachment rings withstanding up to 5 kg of pulling force. Conclusion: Nitinol memory metal attachment rings, covered with textile, around suture ring-denuded St Jude mechanical aortic valve prostheses enabled fast and strong sutureless implantation in acute pig experiments. Further studies in chronic animal models and humans are needed to determine long-term safety

Perioperative assessment of left ventricular function by pressure-volume loops using the conductance catheter method

Interpretation of perioperative measurements of cardiac function during cardiac surgery is complicated by changes in loading conditions induced by anesthesia, cardiopulmonary bypass (CPB), and the surgical procedure itself. Quantification of left ventricular (LV) function by pressure-volume relations as obtained by the conductance catheter would be advantageous because load-independent indices can be determined. Accordingly, we evaluated methodological aspects of the conductance-catheter technique and documented LV function before and after CPB in eight patients undergoing coronary artery bypass grafting. LV pressure-volume loops by transesophageal echocardiography-guided transaortic application of the conductance catheter were obtained at steady-state and during preload reduction by temporary occlusion of the inferior cava. All patients remained hemodynamically stable, and no complications occurred. Complete data were acquired within 15 min before and after CPB, Cardiac output (5.2 ± 1.3 L/min to 6.0 ± 1.4 L/min) and LV ejection fraction (46% ± 17% to 48% ± 19%) did not change, but end-diastolic pressure increased significantly after CPB (8 ± 2 mm Hg to 16 ± 7 mm Hg; P < 0.05). Load-independent systolic indices remained constant (end-systolic elastance: 1.31 ± 1.20 mm Hg/mL to 1.13 ± 0.59 mm Hg/mL). Diastolic function changed significantly after CPB, as the relaxation time constant decreased from 64 ± 6 ms to 52 ± 5 ms (P < 0.05) and the chamber stiffness constant increased from 0.016 ± 0.014/mL to 0.038 ± 0.016/mL (P < 0.05). We conclude that the conductance catheter method provides detailed data on perioperative myocardial function and may be useful for evaluating the effects of new surgical and anesthetic procedures