Early changes in bioprosthetic heart valves following ventricular assist device implantation

Aortic Thrombosis in Patients on Mechanical Circulatory Support: A Systematic Literature Review

BACKGROUND

Aortic valve (AV) thrombosis is an uncommon but ominous complication in patients managed with mechanical circulatory support (MCS) devices. In this systematic review, we summarised the data on clinical presentations and outcomes in such patients.

METHODS

We searched articles on PubMed and Google Scholar, reporting at least one adult patient with aortic thrombosis on MCS support and where the individual patient data could be extracted. We grouped the patients by the type of MCS (temporary or durable), and the type of the AV (prosthetic, surgically modified, or native) RESULTS: We identified reports on six patients with aortic thrombus on short-term MCS, and on 41 patients on durable left ventricular assist devices (LVADs). On temporary MCS, AV thrombus typically causes no symptoms and is found incidentally pre- or intra-operatively. For those with durable MCS, the occurrence of aortic thrombus forming on prosthetic or surgically modified valves appears to be more related to the intervention on the valve, rather than from the presence of LVAD. The mortality in this group was 18%. In patients with native AV on durable LVAD support, 60% of patients presented with acute myocardial infarction, acute stroke, or acute heart failure, and mortality in this cohort was 45%. In terms of management, heart transplantation was most successful.

CONCLUSIONS

While the outcomes of aortic thrombosis were good in patients where temporary MCS was used in the setting of aortic valve surgery, patients with native AV who develop this complication on durable LVAD have high morbidity and mortality. Cardiac transplantation should be strongly considered in eligible candidates because other therapies provide inconsistent results.

Guidelines for the Use of Transesophageal Echocardiography to Assist with Surgical Decision-Making in the Operating Room: A Surgery-Based Approach: From the American Society of Echocardiography in Collaboration with the Society of Cardiovascular Anesthesiologists and the Society of Thoracic Surgeons

Intraoperative transesophageal echocardiography is a standard diagnostic and monitoring tool employed in the management of patients undergoing an entire spectrum of cardiac surgical procedures, ranging from "routine" surgical coronary revascularization to complex valve repair, combined procedures, and organ transplantation. Utilizing a protocol as a starting point for imaging in all procedures and all patients enables standardization of image acquisition, reduction in variability in quality of imaging and reporting, and ultimately better patient care. Clear communication of the echocardiographic findings to the surgical team, as well as understanding the impact of new findings on the surgical plan, are paramount. Equally important is the need for complete understanding of the technical steps of the surgical procedures being performed and the complications that may occur, in order to direct the postprocedure evaluation toward aspects directly related to the surgical procedure and to provide pertinent echocardiographic information. The rationale for this document is to outline a systematic approach describing how to apply the existing guidelines to questions on cardiac structure and function specific to the intraoperative environment in open, minimally invasive, or hybrid cardiac surgery procedures.

Aortic Valve Repair Versus Replacement Associated With Durable Left Ventricular Assist Devices

BACKGROUND

Aortic valve (AV) repair (AVr) using a central coaptation stitch or bioprosthetic AV replacement (AVR) are most commonly performed at the time of durable left ventricular assist device implant to address AV insufficiency (AI).

METHODS

Prospective data collection on 46 patients undergoing left ventricular assist device implant from 2007 through 2018 who received concomitant AVr (n = 40) or AVR (n = 6) was retrospectively analyzed to assess freedom from recurrent aortic insufficiency. Paired Wilcoxon rank-sum test was used to compare echocardiographic findings. Mantel-Cox statistics were used to analyze survival.

RESULTS

For AVr, central coaptation led to a mean decrease in AI severity by 2.1 ± 1.0 grades (P < .001). Three patients (7.5%) had recurrence of at least moderate AI by 3 years. In comparison, all patients in the AVR group had mild or less AI on subsequent follow-up. Success of AVr in downgrading AI severity was associated with a smaller aortic root diameter (P = .011) and sinotubular junction diameter (P = .003). An aortic root diameter greater than 3.5 cm was predictive of less improvement in AI severity compared with 3.5 cm or less (1.83 ± 1.03 versus 2.47 ± 0.80 grades of improvement; P = .038). Duration of cardiopulmonary bypass was 32 minutes longer and duration of aortic cross-clamp was 38 minutes longer for AVR versus AVr cohorts. No difference in 30-day (P = .418) or overall survival (P = .572) between the AVr and AVR groups was seen.

CONCLUSIONS

Aortic valve repair for addressing AI has a recurrence rate of 7.5% at 3 years. Success in downgrading AI is more likely with a smaller aortic root. No difference in survival was observed between AVr and AVR.

Physical equivalency of wild type and galactose α 1,3 galactose free porcine pericardium; a new source material for bioprosthetic heart valves

Humans make high levels of antibody to carbohydrates with terminal galactose α 1,3 galactose (Gal) modifications. This Gal antigen is widely expressed in other mammals and is present on an array of current animal derived biomedical devices including bioprosthetic heart valves. There is growing interest in using Gal-free animal tissues from Gal knockout pigs (GTKO) as these tissues would not be affected by anti-Gal antibody mediated injury. In this study we compare the composition and biophysical characteristics of glutaraldehyde fixed porcine pericardium from standard and GTKO pigs. We show that with the exception of the Gal antigen which is only present in standard pig tissue both GTKO and standard pig tissue have the same general morphology and collagen content. Moreover uniaxial stress testing and suture retention testing indicate the tissues are equivalent in tensile strength. These studies indicate that genetic disruption of the α-galactosyltransferase (GGTA-1) which blocks synthesis of the Gal antigen has no significant impact on the structural integrity of porcine pericardium and suggest that this tissue could be directly substituted for standard pig pericardium in biomedical devices such as bioprosthetic heart valves.

STATEMENT OF SIGNIFICANCE

Surgical heart valve replacement is a proven life saving therapy to treat heart valve dysfunction due to birth defects, infection and the effects of aging. Bioprosthetic heart valves (BHV) made from glutaraldehyde fixed animal tissues are an effective durable therapy in older patients (>60years) but exhibit age-dependent structural valve degeneration (SVD) in younger patients (<60years). SVD is principally caused by BHV calcification. Immune injury contributes to age-dependent SVD through the interaction of galactose α 1,3 galactose (Gal) a dominant xenogeneic antigen present on commercial BHVs and universally abundant human anti-Gal antibody. This study measures the tissue equivalency between standard pig pericardium and Gal-free pericardium from genetically modified pigs as a first step towards making Gal-free BHVs.

Exertional Angina Due To Fused Aortic Bioprosthesis During Left Ventricular Assist Device Support: Two Cases and Review of the Literature

We present the case of two patients with idiopathic dilated cardiomyopathy and moderate aortic valve regurgitation that were treated with a bioprosthetic valve at the time of the left ventricular assist device (LVAD) implantation. A few months later, patients revealed partial recovery in the left ventricle systolic function. Both patients, during the LVAD turndown protocol, reported the onset of chest pain. The transthoracic echocardiography revealed the presence of a new transaortic pressure gradient. We confirmed the presence of a fused bioprosthetic valve by further performing a transesophageal echocardiogram and a left and right heart catheterization. Replacement of aortic valve at the time of an LVAD implantation constitutes a challenging case. Although a mechanical valve is contraindicated due to the increased thromboembolic risk, selecting a bioprosthetic valve increases the risk of valve leaflets fusion. The consequences of this phenomenon should be acknowledged in LVAD patients undergoing aortic valve replacement with a bioprosthetic, especially under the view of LVAD explantation for those revealing myocardial recovery under mechanical unloading.

Replacement of the aortic valve with a bioprosthesis at the time of continuous flow ventricular assist device implantation for preexisting aortic valve dysfunction

Left ventricular assist device (LVAD) implantation has become a mainstay of therapy for advanced heart failure patients who are either ineligible for, or awaiting, cardiac transplantation. Controversy remains over the optimal therapeutic strategy for preexisting aortic valvular dysfunction in these patients at the time of LVAD implant. In patients with moderate to severe aortic regurgitation, surgical approaches are center specific and range from variable leaflet closure techniques to concomitant aortic valve replacement (AVR) with a bioprosthesis. In the present study, we retrospectively analyzed our outcomes in patients who underwent simultaneous AVR and LVAD implantation secondary to antecedent aortic valve pathology. Between January 2004 and June 2010, 144 patients underwent LVAD implantation at a single institution. Of these, 7 patients (4.8%) required concomitant AVR. Five of the 7 patients (71%) survived to hospital discharge and suffered no adverse events in the perioperative period. One-year survival for the discharged patients was 80%, and no prosthetic valve-related adverse events were observed in long-term follow-up. Given our experience, we conclude that bioprosthetic AVR is a plausible alternative for end-stage heart failure patients at the time of LVAD implantation.

Long-term left ventricular support in patients with a mechanical aortic valve

OBJECTIVES

The presence of a mechanical prosthesis has been regarded as an increased risk of thromboembolic complications and as a relative contraindication for a left ventricular assist device (LVAD). Five patients in our center had a mechanical aortic valve at the time of device implantation and were studied regarding thromboembolic complications.

DESIGN

Five patients operated upon with an LVAD (1 HeartMate I™, 4 HeartMate II™) between 2002 and 2011 had a mechanical aortic valve at the time of implantation. The first patient had a patch closure of the aortic valve. In four patients, the prosthesis was left in place. Anticoagulants included aspirin, warfarin, and clopidogrel.

RESULTS

The average and accumulated treatment times were 150 and 752 days, respectively. Three of the five patients showed early signs of valve thrombosis on echo with concomitant valve dysfunction. Four patients were transplanted without thromboembolic events during pump treatment. One patient died from a hemorrhagic stroke after 90 days on the LVAD.

CONCLUSIONS

The strategy of leaving a mechanical heart valve in place at the time of LVAD implantation in five patients led to valvular thrombosis in three but did not provoke embolic events. It increased the complexity of postoperative anticoagulation.

Bioprosthetic aortic valve changes late after insertion of a left ventricular assist device

A 60-year-old man had his aortic valve replaced and a HeartMate II ventricular assist device (VAD) inserted; 18 months later, he received a heart transplant. The explanted heart had a grossly fibrotic appearance on the ventricular side, with scar tissue extending onto the cusps. VAD therapy can lead to both acute and chronic changes in the valves, which may be clinically significant.

Management of aortic valve insufficiency in patients supported by long-term continuous flow left ventricular assist devices

Continuous flow (CF) left ventricular assist devices (LVADs) have yielded improved outcomes in patient survival and quality of life compared with first-generation pulsatile pumps; however, they have been associated with an increased incidence of postimplant aortic valve insufficiency (AI), which can have can have serious clinical consequences if not diagnosed and treated expeditiously. We reviewed our experience with AI after LVAD since the start of our CF LVAD program. From March 2006 through July 2011, 94 patients with chronic heart failure underwent implantation of a HeartMate II (HM II) LVAD. Severe AI developed in three patients after CF LVAD implantation. The clinical records of these patients were reviewed to analyze the presenting signs and symptoms of AI, identify the duration of LVAD support when the AI occurred, how the AI was treated, and the outcomes.

Aortic valve procedures at the time of ventricular assist device placement

BACKGROUND

Placement of a ventricular assist device (VAD) may lead to reduced or absent opening of the aortic valve and thus increase risk of thrombus formation in the aortic root as well as on the valve itself. The outcome of additional procedures to the aortic valve at the time of VAD placement is unclear.

METHODS

A retrospective analysis of 712 VAD patients from 1995 to 2009 was performed.

RESULTS

Twenty-eight patients were identified who underwent aortic valve procedures in addition to VAD placement. Indication for VAD placement was bridge to transplant in 23 patients, destination therapy in 4, and postcardiotomy shock in 1. Aortic valve procedures were performed for preexisting mechanical aortic prosthesis in 8 (7 closure and 1 aortic valve replacement with biological prosthesis), and for moderate or severe aortic insufficiency in 20 patients (10 repair, 9 closure, and 1 aortic valve replacement with biological prosthesis). At the last follow-up, 16 patients had undergone heart transplant, 6 remained on VAD support, and 5 had died. While on VAD support, no adverse events related to the aortic valve procedures occurred. The 30-day operative mortality was 0.4%. No clinical thromboembolic events were observed. In 2 patients, there was evidence of thrombus formation in the explanted heart. Four patients had bleeding complications. Of the 9 patients who received aortic valve repair, 2 had recurrent aortic insufficiency on echocardiograms during an average follow-up of 118 days.

CONCLUSIONS

Additional procedures to the aortic valve at the time of VAD placement are feasible. Overall outcomes are comparable to those seen in patients without the need for aortic valve manipulation at the time of VAD placement.

Aortic valve pathophysiology during left ventricular assist device support

The increased applicability and excellent results with left ventricular assist devices (LVADs) have revolutionized the available treatment options for patients with advanced heart failure. Pre-existing valve abnormalities are common in this population, and subsequent development of valve abnormalities after LVAD placement is also often noted. Although native mitral and tricuspid valve disease is more common in heart failure patients before LVAD placement, aortic valves are much more likely to generate abnormal pathophysiology in the LVAD patient during as well as after LVAD placement. The aim of this comprehensive review is to review aortic valve function in LVAD patients and highlight the consideration of pre-existing valve disease on patient treatment at the time of LVAD implant. The basis for structural changes leading to valve pathophysiology during and after LVAD placement will be described, providing a basis for improved clinical understanding and new strategies to prevent these conditions.

Clinical management of continuous-flow left ventricular assist devices in advanced heart failure

Continuous-flow left ventricular assist devices (LVAD) have emerged as the standard of care for advanced heart failure patients requiring long-term mechanical circulatory support. Evidence-based clinical management of LVAD-supported patients is becoming increasingly important for optimizing outcomes. In this state-of-art review, we propose key elements in managing patients supported with the new continuous-flow LVADs. Although most of the presented information is largely based on investigator experience during the 1,300-patient HeartMate II clinical trial, many of the discussed principles can be applied to other emerging devices as well. Patient selection, pre-operative preparation, and the timing of LVAD implant are some of the most important elements critical to successful circulatory support and are principles universal to all devices. In addition, proper nutrition management and avoidance of infectious complications can significantly affect morbidity and mortality during LVAD support. Optimizing intraoperative and peri-operative care, and the monitoring and treatment of other organ system dysfunction as it relates to LVAD support, are discussed. A multidisciplinary heart failure team must be organized and charged with providing comprehensive care from initial referral until support is terminated. Preparing for hospital discharge requires detailed education for the patient and family or friends, with provisions for emergencies and routine care. Implantation techniques, troubleshooting device problems, and algorithms for outpatient management, including the diagnosis and treatment of related problems associated with the HeartMate II, are discussed as an example of a specific continuous-flow LVAD. Ongoing trials with other continuous-flow devices may produce additional information in the future for improving clinical management of patients with these devices.