Permanent pacemaker implantation after On-X surgical aortic valve replacement: SWEDEHEART observational study

ObjectiveBioprosthetic aortic valves with an extended subannular component, such as transcatheter valves, exert increased compression on the cardiac conduction system and increase the risk for permanent pacemaker implantation. It is unknown if the On-X mechanical prosthetic valve, which has an elongated subannular valve housing, increases the risk of permanent pacemaker implantation following aortic valve replacement.DesignObservational nationwide cohort study.SettingSwedish population-based study.ParticipantsAll patients aged 18–65 years who underwent primary mechanical aortic valve replacement in Sweden between 2005 and 2018. We used the Swedish Web system for Enhancement and Development of Evidence-based care in Heart disease Evaluated According to Recommended Therapies register and other Swedish national health-data registers.ExposurePatients implanted with an On-X valve versus patients implanted with other bileaflet mechanical valves.Primary and secondary outcome measuresPrimary outcome measure was permanent pacemaker implantation within 30 days of surgery.ResultsA total of 2602 patients were included, and 581 patients received an On-X valve and 2021 patients received a St Jude Masters/Regent (n=945) or Carbomedics Reduced valve (n=1076). In the total study population, 115 (4.4%) permanent pacemaker implantations were performed within 30 days after aortic valve replacement. In the propensity score matched population, there was no significant difference in the rate of permanent pacemaker implantation in the On-X group compared with the control group: 3.6% (95% CI: 2.4% to 5.5%) vs 4.0% (95% CI: 2.7% to 5.9%), p=0.877.ConclusionsThe On-X prosthetic heart valve was associated with a similarly low risk for permanent pacemaker implantation after aortic valve replacement compared with other conventional bileaflet mechanical valves. The On-X elongated subannular valve housing does not interfere with the cardiac conduction system.

Influence of Transvalvar Pressure Gradient on Hinge Washing in Closed Mechanical Prosthetic Cardiac Valves Under Pulmonary Pressure Conditions: A Comparative In Vitro Study

Objective: Hinge washing is a crucial factor in the prevention of mechanical prosthetic valvar thrombosis, especially in the pulmonary valve position. The aim of this laboratory study was to determine the relationship between pressure difference and the amount of hinge washing in the closed position, using the pressures that are normal for the right ventricle and pulmonary artery. Methods: In an in vitro setting, four different bileaflet mechanical valves were tested for hinge washing in closed position. Based on similarity in inner diameter (range: 20.5-21.4 mm), the following valves were tested: Abbott SJM Regent size 23, Cryolife On-X size 23, LivaNova Carbomedics-R size 25, Medtronic Open Pivot (M-OP)-A size 25. Tests were carried out in a range between 3 and 100 mm Hg pressure difference, using water as a test fluid. The amount of leakage per minute through the closed valve was measured. Results: All four valves showed an increase in leakage with increasing transvalvar gradient, and the relationship between pressure and leakage behaves in logarithmic fashion. Leakage under normal pulmonary diastolic pressure conditions (10 mm Hg) was between 23.3% and 29.3% of the leakage under aortic diastolic pressure conditions (80 mm Hg). The Cryolife On-X valve showed the highest closed leakage volume under pulmonary conditions (10 mm Hg) 0.254 ± 0.01 (L/min), where the Medtronic M-OP showed the lowest leakage volume with 0.125 ± 0.014 (mL/min). Conclusion: Hinge washing is related to transvalvar pressure difference in closed position. Valve brands differed significantly from each other in the amount of hinge washing.

The Inertia of the Anterior Leaflet of the Heart’s Mitral Valve

Virtual mass effects generate forces that act on any object accelerating in a fluid medium. While there have been computational models of bileaflet mechanical valves that include virtual mass effects [1], current computational models of fluid structure interaction of native mitral valves do not consider virtual mass effects, resulting in an incomplete measure of the forces acting on the valve. As far as the authors aware no closed-form relationship for the virtual mass coefficient, Cm, of the native mitral valve has been determined. Integrating the effects of virtual mass into computational models of the mitral valve would result in a more complete model, and could yield more accurate and relevant results from computational models of the mitral valve.

Results of Isolated Valve Replacement in Hemodialysis Patients

Frequent bleeding complications and poor long-term results have been reported after valve replacement in hemodialysis patients. We use mainly bileaflet mechanical valves with low-dose warfarin therapy (target international normalized ratio, 1.8–2.0) in such cases. Data of 27 hemodialysis patients undergoing isolated valve replacement from 1993 to 2002 were retrospectively analyzed. Bileaflet mechanical valves were selected in 23 patients and bioprostheses in 4. Those with mechanical valves were treated with mild anticoagulation therapy. There were 3 (11.1%) early deaths due to ischemic colitis, interstitial pneumonia, and ventricular arrhythmia. There were 3 late deaths and 5 bleeding complications during follow-up. The overall survival rate was 85.2% at 3 years and 72.9% at 5 years. The survival rate of patients with mechanical valves was 82.6% at 3 years and 76.7% at 5 years. One patient with a bioprosthesis experienced structural valvular deterioration after 3 years. The results demonstrate an acceptable long-term outcome. A bileaflet mechanical valve managed with mild anticoagulation therapy is a reasonable strategy for hemodialysis patients.