A randomized comparison of the MCRI On-X and CarboMedics Top Hat bileaflet mechanical replacement aortic valves: Early postoperative hemodynamic function and clinical events

Hemodynamic Comparison of the On-X and Top Hat Mechanical Aortic Valve Prostheses

BACKGROUND

There are limited data comparing hemodynamic valve function in mechanical aortic valve prostheses. This study compared the hemodynamic function of 2 commonly used mechanical aortic valve (AV) prostheses, the On-X (Artivion) and Top Hat (CarboMedics Inc) valves.

METHODS

This study was a retrospective analysis of 512 patients who underwent AV replacement with the On-X (n = 252; 49%) or Top Hat (n = 260; 51%) mechanical valves between 2011 and 2019. Patients were matched on the basis of selected variables. Echocardiographic data were collected preoperatively and postoperatively over a median follow-up of 1.39 years.

RESULTS

A total of 320 patients were matched, 160 patients in each group. Despite being matched for left ventricular outflow tract diameter, patients in the Top Hat group received a greater prevalence of smaller tissue annulus diameter valves (≤21 mm) (83% vs 38%; P < .001). Patients in the On-X group had longer aortic cross-clamp times (78 minutes vs 64 minutes; P < .001) during isolated aortic valve replacement. Discharge echocardiography showed no difference in the AV area index between both groups (1.00 cm2/m2 vs 1.02 cm2/m2; P = .377). During longer-term echocardiographic follow-up, the AV area index remained stable for both valves within their respective tissue annulus diameter groups (P = .060).

CONCLUSIONS

There was no difference between the 2 valves with respect to the AV area index at discharge, and hemodynamic function was stable during longer-term follow-up. The longer aortic cross-clamp time observed in the On-X group may indicate increased complexity of implantation compared with the Top Hat group.

Valvular and ascending aortic hemodynamics of the On-X aortic valved conduit by same-day echocardiography and 4D flow MRI

This study aims to assess whether the On-X aortic valved conduit better restores normal valvular and ascending aortic hemodynamics than other commonly used bileaflet mechanical valved conduit prostheses from St. Jude Medical and Carbomedics by using same-day transthoracic echocardiography (TTE) and 4D flow magnetic resonance imaging (MRI) examinations. TTE and 4D flow MRI were performed back-to-back in 10 patients with On-X, six patients with St. Jude (two) and Carbomedics (four) prostheses, and 36 healthy volunteers. TTE evaluated valvular hemodynamic parameters: transvalvular peak velocity (TPV), mean and peak transvalvular pressure gradient (TPG), and effective orifice area (EOA). 4D flow MRI evaluated the peak systolic 3D viscous energy loss rate (VELR) density and mean vorticity magnitude in the ascending aorta (AAo). While higher TPV and mean and peak TPG were recorded in all patients compared to healthy subjects, the values in On-X patients were closer to those in healthy subjects (TPV 1.9 ± 0.3 vs. 2.2 ± 0.3 vs. 1.2 ± 0.2 m/s, mean TPG 7.4 ± 1.9 vs. 9.2 ± 2.3 vs. 3.1 ± 0.9 mmHg, peak TPG 15.3 ± 5.2 vs. 18.9 ± 5.2 vs. 6.1 ± 1.8 mmHg, p < 0.001). Likewise, while higher VELR density and mean vorticity magnitude were recorded in all patients than in healthy subjects, the values in On-X patients were closer to those in healthy subjects (VELR: 50.6 ± 20.1 vs. 89.8 ± 35.2 vs. 21.4 ± 9.2 W/m3, p < 0.001) and vorticity (147.6 ± 30.0 vs. 191.2 ± 26.0 vs. 84.6 ± 20.5 s-1, p < 0.001). This study demonstrates that the On-X aortic valved conduit may produce less aberrant hemodynamics in the AAo while maintaining similar valvular hemodynamics to St. Jude Medical and Carbomedics alternatives.

The role of mechanical valves in the aortic position in the era of bioprostheses and TAVR: Evidence-based appraisal and focus on the On-X valve

Patients who need a prosthetic aortic heart valve may decide, working with their cardiologist and cardiac surgeon, among a variety of options: surgical or transcatheter approach, bioprosthetic or mechanical valve, or a Ross procedure if suitable to their age and anatomy. This review article examines the evidence for survival benefit with mechanical aortic valves, discusses bioprosthetic structural valve degeneration and its consequences, and considers the risks of redo aortic valve surgery or subsequent valve-in-valve (ViV) transcatheter intervention. It highlights the unique characteristics of the On-X aortic valve, including the US Food and Drug Administration approved and American College of Cardiology/American Heart Association guideline supported reduced anticoagulation target INR of 1.5 to 2.0, and discusses the PROACT Xa trial comparing apixaban vs warfarin anticoagulation. The choice of prosthetic valve should be individualized, carefully considering each patient's unique circumstances. In that context, the On-X aortic valve offers a potential lifetime solution without need for a repeat operation, while minimizing the risks of long-term anticoagulation. In an era of enthusiasm for bioprosthetic and transcatheter-based approaches, the option of a second-generation bileaflet mechanical valve with optimized hemodynamics-the On-X aortic valve-may well align with patient expectations.

Optimal Intensity of Warfarin Therapy in Patients With Mechanical Aortic Valves

OBJECTIVE:

To review the current guidelines and published literature in order to identify the evidence-based international normalized ratio (INR) goal in patients with a mechanical aortic valve.

DATA SOURCES:

Medline/PubMed, Cochrane and Google Scholar database searches for relevant articles from 1946 through March 2017 were executed using the key words "mechanical aortic valve" and "antithrombotic therapy or anticoagulation therapy or warfarin."

STUDY SELECTION AND DATA EXTRACTION:

All English-language observational and interventional studies assessing INR goals in patients with a mechanical aortic valve were evaluated.

RESULTS:

After low thrombogenic valves became standard in the practice, the INR goal decreased to 2 to 3 in low-risk recipients with most of bileaflet mechanical aortic valves. There is a paucity of data to justify the INR goal of 2 to 3 in high-risk patients. Until further higher evidence is available, it is reasonable to target an INR range of 2.5 to 3.5 in patients with risk factors for thromboembolism with low thrombogenic valves, except for On-X valve. The INR goal in high-risk On-X aortic valve recipients can be managed at 1.5 to 2.5 with low-dose aspirin 3 months after valve implantation.

CONCLUSION:

The INR goals of 2 to 3 for low risk and 2.5 to 3.5 for high risk should be considered for bileaflet mechanical aortic valve recipients. Additionally, a lower INR goal of 2 to 3 for the first 3 months after valve replacement followed by an INR goal of 1.5 to 2.5 in both low- and high-risk aortic On-X valve recipients may be considered.

Anticoagulation dilemma in a high-risk patient with On-X valves

Thromboembolism continues to be a major concern in patients with mechanical heart valves, especially in those with unsatisfactory anticoagulation levels. The new On-X valve (On-X Life Technologies, Austin, TX, USA) has been reported as having unique structural characteristics that offer lower thrombogenicity to the valve. We report a case where the patient received no or minimal systemic anticoagulation after placement of On-X mitral and aortic valves due to development of severe mucosal arterio-venous malformations yet did not show any evidence of thromboembolism. This case report reinforces the findings of recent studies that lower anticoagulation levels may be acceptable in patients with On-X valves and suggests this valve may be particularly useful in those in whom therapeutic levels of anticoagulation cannot be achieved due to increased risk of bleeding.

Impact of patient-prosthesis mismatch on 30-day outcomes in young and middle-aged patients undergoing aortic valve replacement

Background

The impact of patient-prosthesis mismatch (PPM) on early outcomes in young and middle-aged patients undergoing conventional aortic valve replacement for severe aortic stenosis remains unknown. Our objective was to evaluate the incidence of some degree of PPM and its influence on early mortality and morbidity.

Methods

We analyzed our single center experience in all patients <70 years undergoing first-time isolated aortic valve replacement for severe stenosis in our center from September 2007 to September 2011. PPM was defined as an indexed effective orifice area ≤ 0,85 cm²/m². The influence of PPM on early mortality and postoperative complications was studied using propensity score analysis. Follow up at 30 postoperative days was 100% complete.

Results

Of 199 patients studied, 61 (30,7%) had some degree of PPM. PPM was associated with an increased postoperative mortality (OR = 8,71; 95% CI = 1,67–45,29; p = 0,04) and major postoperative complications (OR = 2,96; CI = 1,03–8,55; p = 0,044). However, no association between PPM and prolonged hospital or ICU stay was demonstrated.

Conclusions

Moderate PPM is a common finding in young and middle-aged patients undergoing surgery for aortic valve replacement due to severe stenosis. In addition, its influence on early outcomes may be relevant.

Left coronary ostial obstruction after aortic valve replacement with a supra-annular aortic valve

We report a rare case of left coronary ostial obstruction after aortic valve replacement with a Top Hat supra-annular aortic valve, which was diagnosed with intraoperative transesophageal echocardiography and successfully treated with an unplanned coronary bypass. The patient was a 76-year-old woman (height 143 cm, weight 44 kg) with aortic stenosis and regurgitation. A 19-mm Top Hat valve was implanted in the supra-annular position because of a small aortic annulus. There was a possibility that the high profile of this prosthesis might block the left coronary ostium. There may be a problem with the use of this prosthesis in patients with small and rigid aortic roots with little compliance. Although the Top Hat valve has a great advantage for small aortic annuli, care in its use should be taken due to possible interference with the coronary ostia.

Heart valve replacement: which valve for which patient?

The ideal heart valve substitute would show no deterioration or thrombogenicity, offer no resistance to blood flow, and be easy to implant. However, such a valve does not exist and we must accept compromises in some of these qualities based on our patients' needs. In selection of cardiac valve prosthesis, valve-related factors such as durability, thrombogenicity, and fluid dynamics should be carefully matched to patient-related factors such as age, size, life expectancy, comorbidities, plans for pregnancy, and lifestyle. In addition, surgeon- or operation-related factors should be considered. Technical aspects of implantation, ease of reoperation, and operative mortalities may tip the risk and benefit balance in a particular direction. We review currently available heart valve prostheses and the clinical factors that are involved in selection of a heart valve substitute.