Total left ventricular outflow tract obstruction due to left ventricular assist device-induced sub-aortic thrombosis in 2 patients with aortic valve bioprosthesis

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.

Long-Term Continuous-Flow Left Ventricular Assist Device Support After Left Ventricular Outflow Tract Closure

Aortic valve insufficiency can be addressed during continuous-flow left ventricular assist device (CF-LVAD) implantation by performing aortic valve repair or replacement, or patch closure of the left ventricular outflow tract (LVOT). However, few studies have examined the safety of long-term CF-LVAD support after LVOT closure. From November 2003 through March 2016, 16 patients with advanced chronic heart failure underwent CF-LVAD implantation and concomitant LVOT closure for severe aortic insufficiency. We compared their long-term outcomes with those of 510 CF-LVAD recipients without concomitant LVOT closure. Total support time was 26.1 patient-years in the LVOT-closure group and 938.6 patient-years in the CF-LVAD-only group. Survival at 30 days, 6 months, 1 year, and 2 years was similar for CF-LVAD-only patients (90.4%, 80.6%, 74.3%, 67.5%) and LVOT-closure patients (81.3%, 81.3%, 75.0%, 68.8%; p = 0.59). There were no deaths related to LVOT closure. The event rate per patient-year for neurologic dysfunction (ND) was 0.23 in the LVOT-closure group (6 ND events) and 0.20 in the CF-LVAD-only group (136 ND events; p = 0.97). We conclude that for select patients with aortic insufficiency who are undergoing CF-LVAD implantation, LVOT closure produces acceptable outcomes and, therefore, is a viable option.

Left ventricular outflow tract closure during LVAD implantation: 2 cases of patients supported for over 6 years

We previously reported a series of 5 patients with advanced heart failure and aortic insufficiency (AI) who underwent concomitant left ventricular outflow tract (LVOT) closure at the time of continuous-flow left ventricular assist device (CF-LVAD) implantation. Although this technique of treating AI has been shown to be effective in the short term, its long-term durability has not been well studied. Here, we report the long-term outcomes of two patients with severe AI who underwent LVOT closure at the time of CF-LVAD implantation. Each of the two patients survived for more than 6 years without any complications related to LVOT closure.

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 Mechanical Circulatory Support in Pediatric Patients

This retrospective study reviews our results regarding the long-term support in pediatric patients using two ventricular assist systems between January 2008 and April 2014. We implanted the Berlin Heart EXCOR in 29 patients (median age 3.4 years [interquartile range (IQR) 0.2-16.5], median weight 13 kg [IQR 4.2-67.2]). Twenty-two patients (75.8%) received a left ventricular assist device. Three patients (10.3%) had single-ventricle physiology. One patient (3.4%) had mechanical mitral valve prosthesis. The HeartWare System was implanted in nine patients. The median age was 15.6 years (IQR 12.2-17.9), and the median weight was 54.9 kg (IQR 27.7-66). In the Berlin Heart group, the median support time was 65 days (IQR 4-619), with 3647 days of cardiac support. Nineteen patients (65.5%) were transplanted, six patients (20.7%) recovered, one patient (3.4%) is on support, and three patients (10.3%) died on support. Survival rate was 89.7%. Fourteen blood pumps had been exchanged. Four patients (13.8%) had local signs of infection, and three patients (10.3%) had neurological complications. In the HeartWare group, the median support time was 180 days (IQR 1-1124), with 2839 days of cardiac support. Four patients (44.4%) had local signs of infection, and three (33.3%) had neurological complications. Eight patients (88.9%) have been transplanted, and one patient (11.1%) died on support. Survival rate was 88.9%. Excellent survival is possible after long-term mechanical circulatory support in patients with two- and single-ventricle physiology with a low rate of adverse events.

Pathological analysis of the aortic valve after long-term left ventricular assist device support

OBJECTIVES

Aortic insufficiency (AI) often develops during left ventricular assist device (LVAD) support and is related to a poor prognosis. As LVAD implantation and the support duration increase, the risk of acquired aortic valve lesions may increase. We investigated the pathological changes in the aortic valve and its function after long-term LVAD support.

METHODS

Thirty-five hearts removed at heart transplantation were investigated. Thirty-one patients were supported by extracorporeal pulsatile devices, and 4 were supported by implantable devices. We compared the histological changes in the aortic valve with the echocardiogram results.

RESULTS

The mean duration of LVAD support was 961 days. Before device implantation, all patients had a normal aortic valve opening, and only 5 had trivial AI. After LVAD support, trivial AI was observed in 18 patients, mild AI in 4 and mild-to-moderate AI in 2. Pathological examination revealed that the aortic valve had become thinner in all patients, ranging from 120 to 1400 µm. The aortic wall had also become thinner in most patients, ranging from 830 to 2220 µm. Left ventricular wall thickness was ranging from 4 to 13 mm, and aortic annular diameter was ranging from 17 to 27 mm. Partial aortic valve fusion was seen in 17 (48.6%) recipients, and curling with leaflet shortening was detected in 22 (62.9%) patients. Dense collagen accumulation in the spongiosa layer was also present. All aortic valves of the patients with mild and mild-to-moderate AI showed a scarce or no opening before explantation. Conversely, the AI grade of patients whose aortic valve frequently opened remained none or trivial. There was no close correlation between these pathological findings and the development of AI independently.

CONCLUSIONS

Degenerative aortic valve changes were recognized after long-term LVAD support. There was also an increasing prevalence of mild and mild-to-moderate AI, which may have been associated with continuous aortic valve closure. An optimal strategy to prevent AI development should be determined, and careful periodic echocardiographic follow-up is essential.

Can a Central Stitch over the Arantius' Nodules Provide a Solution for Pre-Operative Severe Native AI in LVAD Patients?

Purpose

To evaluate the evolution of aortic valve insufficiency (AI) after Park's central stitch in patients with severe, pre-operative, native aortic valve insufficiency.

Methods

We retrospectively studied 71 continuous flow LVAD patients between January 2004 and December 2010. Four patients with AI≥3/4 were treated with a central stitch. An intensive review of the literature was performed to debate the use of the central stitch in this population.

Results

The AI at baseline (AI = 2.75 ± 0.5) and AI at last measurement (AI = 0.75 ± 0.65) is statistically different after central stitch (p<0.05) with mean follow up of 198.25 (± 146.70) days. Total cross clamp-time during the placement of the stitch was 15.5 minutes (± 13.062). CVA was not diagnosed in our cohort.

Conclusions

Park's central stitch can be successfully performed on patients with severe native AI (≥3/4) with good long-term results. Short ischemic time and simple application of the stitch are the biggest advantages. Due to the progression of AI in longstanding LVAD, the central stitch may be beneficial for LVAD in destination therapy. Since this is a small group of patients and also an early experience, more cases will be necessary to confirm these positive results.

Simultaneous aortic valve replacement in left ventricular assist device recipients: single-center experience

INTRODUCTION

Aortic valve regurgitation or the presence of a mechanical aortic valve prosthesis is a relative contraindication for implantation of left ventricular assist devices (LVAD). However, concomitant aortic valve replacement by a biological prosthesis is one of the options in this situation. We analyzed our recent experience with left ventricular assist device implantation and concomitant aortic valve replacement.

METHODS

Between January 1, 2008 and January 15, 2012, 318 adult patients (>18 years old) were supported with a long-term implantable LVAD in our institution. In 19, simultaneous aortic valve replacement (6 redo and 13 primary procedures) was performed. Patients were divided into 2 groups according to INTERMACS (IM) level: Group 1 (n = 7) consisted of patients with IM level 1-2 and Group 2 (n = 12) of IM level 3-4 patients. As a control cohort we analyzed all LVAD recipients during the study period (n = 299, study group excluded). The control cohort was similarly divided into two groups according to the IM level: Group 3 (n = 162) consisted of patients with IM level 1-2 and Group 4 (n = 137) of those with IM level 3-5. Perioperative data and outcomes in all groups were retrospectively analyzed and compared (Group 1 compared to Group 3; and Group 2 to Group 4).

RESULTS

In study Groups 1 and 2 all patients were male; in Groups 3 and 4, 80% and 88% respectively were male. Median age distribution in Groups was 55, 61, 54, and 57 years respectively. Patients from Group 2 were significantly older than those from Group 4 (p = 0.039). Body mass index was significantly lower in Group 1 than in Group 3 (p = 0.033). Cardio-pulmonary bypass time was significantly longer in Groups 1 and 2 compared with Groups 3 and 4 respectively (p=0.001). Patients from Group 1 had a trend more often to develop right ventricular failure requiring a right ventricular assist device (RVAD) than those in Group 3 (p = 0.09). Intensive care unit stay duration of mechanical ventilation and in-hospital mortality in Group 1 were significantly higher than in Group 3 (p = 0.025, p = 0.005, p = 0.038). Patients from Group 2 had similar outcomes compared to those from Group 4.

CONCLUSIONS

In stable patients, simultaneous aortic valve replacement and LVAD implantation are not associated with an impaired outcome. In patients with cardiogenic shock an additional aortic valve replacement may impair outcome; therefore alternative techniques should be considered.

Numerical characterization of hemodynamics conditions near aortic valve after implantation of Left Ventricular Assist Device

Left Ventricular Assist Devices (LVADs) are implantable mechanical pumps that temporarily aid the function of the left ventricle. The use of LVADs has been associated with thrombus formation next to the aortic valve and close to the anastomosis region, especially in patients in which the native cardiac function is negligible and the aortic valve remains closed. Stagnation points and recirculation zones have been implicated as the main fluid dynamics factors contributing to thrombus formation. The purpose of the present study was to develop and use computer simulations based on a fluid-structure interaction (FSI) solver to study flow conditions corresponding to different strategies in LVAD ascending aortic anastomosis providing a scenario with the lowest likelihood of thrombus formation. A novel FSI algorithm was developed to deal with the presence of multiple structures corresponding to different elastic properties of the native aorta and of the LVAD cannula. A sensitivity analysis of different variables was performed to assess their impact of flow conditions potentially leading to thrombus formation. It was found that the location of the anastomosis closest to the aortic valve (within 4 cm away from the valve) and at the angle of 30 minimizes the likelihood of thrombus formation. Furthermore, it was shown that the rigidity of the dacron anastomosis cannula plays almost no role in generating pathological conditions downstream from the anastomosis. Additionally, the flow analysis presented in this manuscript indicates that compliance of the cardiovascular tissue acts as a natural inhibitor of pathological flow conditions conducive to thrombus formation and should not be neglected in computer simulations.

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.

Perioperative echocardiographic examination for ventricular assist device implantation

Ventricular assist devices (VADs) are systems for mechanical circulatory support of the patient with severe heart failure. Perioperative transesophageal echocardiography is a major component of patient management, and important for surgical and anesthetic decision making. In this review we present the rationale and available data for a comprehensive echocardiographic assessment of patients receiving a VAD. In addition to the standard examination, device-specific pre-, intra-, and postoperative considerations are essential to the echocardiographic evaluation. These include: (a) the pre-VAD insertion examination of the heart and large vessels to exclude significant aortic regurgitation, tricuspid regurgitation, mitral stenosis, patent foramen ovale, or other cardiac abnormality that could lead to right-to-left shunt after left VAD placement, intracardiac thrombi, ventricular scars, pulmonic regurgitation, pulmonary hypertension, pulmonary embolism, and atherosclerotic disease in the ascending aorta; and to assess right ventricular function; and (b) the post-VAD insertion examination of the device and reassessment of the heart and large vessels. The examination of the device aims to confirm completeness of device and heart deairing, cannulas alignment and patency, and competency of device valves using two-dimensional, and color, continuous and pulsed wave Doppler modalities. The goal for the heart examination after implantation should be to exclude aortic regurgitation, or an uncovered right-to-left shunt; and to assess right ventricular function, left ventricular unloading, and the effect of device settings on global heart function. The variety of VAD models with different basic and operation principles requires specific echocardiographic assessment targeted to the characteristics of the implanted device.

Native aortic valve insufficiency in patients with left ventricular assist devices

Management of mild to moderate aortic insufficiency in patients with a left ventricular assist device remains controversial. We report 3 patients with aortic insufficiency and pulsatile left ventricular assist devices treated with a central aortic valve coapting suture. Two of the repairs have been durable for more than 1 year and aspirin appears to be sufficient anticoagulation.

The Effect of Intermittent Low Speed Mode Upon Aortic Valve Opening in Calves Supported With a Jarvik 2000 Axial Flow Device

We assessed the effects of an axial flow left ventricular assist device (LVAD) upon aortic valve opening, pump outflow, and biologic and hematologic parameters when operated in intermittent low speed (ILS) mode. An ILS controller equipped Jarvik 2000 LVAD was implanted in six calves. Pump speed was maintained at 10,000 rpm, and pump outflow was measured throughout the study period (71 +/- 6 days [mean +/- SD]). Hematologic and biochemical parameters were analyzed daily for the first 10 days, weekly for the first month, and biweekly thereafter to monitor for kidney or liver dysfunction, hemolysis, bleeding, or infection. Before study termination, esmolol hydrochloride was infused to induce low cardiac output and totally impair aortic valve opening. Radiopaque cineaortography was performed over 30 second intervals (10 seconds before, 10 seconds during, and 10 seconds immediately after ILS controller activation) to assess the effect of ILS mode upon aortic valve opening. After study termination, major end organs and the major vascular tree were removed and examined macroscopically and histologically for thrombus formation and infarction; the aortic valve was examined for thickening and fusion. All pumps were explanted and examined for thrombus formation. All six calves recovered without surgical or mechanical complications. Hematologic and biochemical parameters did not change significantly between baseline and study termination. The aortic valve successfully opened when ILS mode was activated, even under low cardiac output conditions. No thrombus was detected in the major end organs and vascular tree, except for some small renal infarcts in three calves that did not affect renal function. These results indicate that operating an axial flow LVAD in ILS mode allows aortic valve opening and aortic root washout.

Pathology in patients with ventricular assist devices

BACKGROUND

Ventricular assist devices (VADs) are used as a bridge to cardiac transplantation or as a permanent or sometimes temporary treatment for end stage heart failure.

METHODS

Our autopsy and surgical pathology experience with VADs prior to August 2002 was reviewed. Noted were patient's age, sex, underlying (UCOD) and proximate causes of death (PCOD), duration of VAD implantation, presence of native or prosthetic valvar disease and organ complications. Myocardium from biopsies and explanted hearts were blindly assessed for coagulative necrosis (CN), contraction bands (CB), myocytolysis (MC), increased eosinophilia (IE), myocyte waviness (MW) and fibrosis (F). Each was graded as either mild (score 1), moderate (score 2) or severe (score 3).

RESULTS

Autopsy patients: Twenty-one patients, with mean age 55 years (range 10-73), comprised 10 women and 11 men. UCOD was ischemic disease in 16 patients, dilated cardiomyopathy in 4 and aortic valve disease in 1. The mean duration of VAD implantation was 125.7 days (range 1-1095 days, S.D.=253.6). Five patients had biventricular VADs, and 16 had LVAD only. Acquired aortic valve fusion was noted in three patients. PCOD was VAD related in six, donor heart problem in four, cerebrovascular accident in four, miscellaneous in three, pulmonary hypertension in two and aortic disease in two patients. Morbidity: local liver necrosis in seven, acquired aortic valve disease in four, gut infarction in three, abdominal aortic aneurysm in two and host cell assault against VAD porcine aortic valves in one case. Biopsies and explanted hearts: Twenty-four patients had a mean age of 53 years (range 38-68, S.D.=8.6). VADs were implanted for 177.8 days (range 7-593 days, S.D.=151.1). Comparison of histologic scores of biopsies with explanted hearts showed the following: CN 1.33 (S.D.=1.4)/0.21 (S.D.=0.66; P<.001); CB: 2.1 (S.D.=0.93)/0.83 (S.D.=0.28; NS); MC: 0.88 (S.D.=1.19)/0.13 (S.D.=0.34; P<.01); IE: 1.71 (S.D.=1.27)/0.38 (S.D.=0.65; NS); fibrosis: 1.08 (S.D.=1.35)/1.75 (S.D.=1.26; NS); and MW: 1.50 (S.D.=1.22)/0.59 (S.D.=0.73; P<.01). Acquired aortic stenosis developed in six hearts, and one heart showed thrombotic occlusion of the left ventricular outflow tract below an aortic bioprosthesis.

CONCLUSIONS

VAD significantly reduced the amount of CN, MC and MW in the left ventricle but may lead to acquired aortic stenosis of native aortic valves or total occlusive thrombosis of aortic prosthetic valves. Proximate cause of death was, most often, VAD related.