Development of de novo aortic valve incompetence in patients with the continuous-flow HeartWare ventricular assist device

Preoperative higher right ventricular stroke work index increases the risk of de novo aortic insufficiency after continuous-flow left ventricular assist device implantation

During continuous-flow left ventricular assist device (CF-LVAD) support, hemodynamic shear stress causes a burden on aortic valve (AV) leaflets, leading to de novo aortic insufficiency (AI). This study investigated the influence of preoperative hemodynamic parameters on de novo AI in CF-LVAD recipients. We reviewed 125 patients who underwent CF-LVAD implantation without concomitant AV surgery between 2005 and 2018. De novo AI was defined as moderate or severe AI in those with none or trivial preoperative AI. During mean 30 ± 16 months of CF-LVAD support, de novo AI-free rate was 86% and 67% at 1 and 2 years, respectively. Multivariable analysis showed that higher right ventricular stroke work index (RVSWI) (hazard ratio, 1.12 /g/m2/beat; 95% confidence interval, 1.00-1.20; p = 0.047) and trivial grade AI (hazard ratio, 2.8; 95% confidence interval, 1.2-6.4; p = 0.020) were independent preoperative risk factors for de novo AI. The longitudinal analysis using generalized mixed effects model showed that higher RVSWI was associated with continuous AV closure after LVAD implantation (Odd ratio, 1.20/g/m2/beat; 95% confidence interval, 1.00-1.43 /g/m2/beat; p = 0.047). Right heart catheterization revealed that preoperative RVSWI was positively correlated with postoperative pump flow index in patients with continuously closed AV (r = 0.44, p = 0.04, n = 22). Preoperative higher RVSWI was a significant risk factor for de novo AI following CF-LVAD implantation. In patients with preserved right ventricular function, postoperative higher pump flow may affect AI development via hemodynamic stress on the AV.

Incidence and clinical correlates of de-novo aortic regurgitation with a fully magnetically levitated left ventricular assist device: a MOMENTUM 3 trial portfolio analysis

AIMS

We assessed the incidence, predictors and clinical correlates of de-novo aortic regurgitation (AR), which physiologically reduces left ventricular assist device (LVAD) effectiveness due to recirculation syndrome, in the MOMENTUM 3 trial portfolio of the fully magnetically levitated HeartMate 3 (HM3) pump using the randomized pivotal trial (PT) and post-trial continued access protocol (CAP).

METHODS AND RESULTS

De-novo aortic regurgitation incidence at 2 years was analysed in the randomized PT and validated in the first 1000 implanted patients of the CAP. Patients with concomitant/prior aortic valve surgery or without baseline or post-implant echocardiograms were excluded from this analysis. AR severity was assessed qualitatively by site-adjudicated echocardiograms (significant AR was defined as moderate or severe grade on echocardiogram). Of 1028 patients enrolled in the PT, 918 were eligible for inclusion in this analysis (HM3, n = 465; HMII, n = 453). At 2 years of LVAD support, freedom from significant AR was greater in the HM3 (92%) than HMII (82%) (hazard ratio 0.45, 95% confidence interval 0.27-0.75, p < 0.01). Of 907 HM3 patients analysed from the first 1000 implanted CAP patients, the rate of freedom from significant AR was 90%, consistent with the PT (p = 0.3). In the combined HM3 group (n = 1372), multivariable Cox modelling identified increasing age and female sex as significant predictors. Survival free of urgent transplant or AR corrective procedure was similar between HM3 patients with and without significant de-novo AR.

CONCLUSIONS

The development of moderate or severe grade de-novo AR is reduced with the fully magnetically levitated HM3 LVAD compared to the axial-flow HMII pump. The occurrence of significant de-novo AR with the HM3 pump is not associated with a worse outcome at 2 years of follow-up.

Reciprocal interferences of the left ventricular assist device and the aortic valve competence

Patients suffering from end-stage heart failure tend to have high mortality rates. With growing numbers of patients progressing into severe heart failure, the shortage of available donors is a growing concern, with less than 10% of patients undergoing cardiac transplantation (CTx). Fortunately, the use of left ventricular assist devices (LVADs), a variant of mechanical circulatory support has been on the rise in recent years. The expansion of LVADs has led them to be incorporated into a variety of clinical settings, based on the goals of therapy for patients ailing from heart failure. However, with an increase in the use of LVADs, there are a host of complications that arise with it. One such complication is the development and progression of aortic regurgitation (AR) which is noted to adversely influence patient outcomes and compromise pump benefits leading to increased morbidity and mortality. The underlying mechanisms are likely multifactorial and involve the aortic root-aortic valve (AV) complex, as well as the LVAD device, patient, and other factors, all of them alter the physiological mechanics of the heart resulting in AV dysfunction. Thus, it is imperative to screen patients before LVAD implantation for AR, as moderate or greater AR requires a concurrent intervention at the time of LVADs implantation. No current strict guidelines were identified in the literature search on how to actively manage and limit the development and/or progression of AR, due to the limited information. However, some recommendations include medical management by targeting fluid overload and arterial blood pressure, along with adjusting the settings of the LVADs device itself. Surgical interventions are to be considered depending on patient factors, goals of care, and the underlying pathology. These interventions include the closure of the AV, replacement of the valve, and percutaneous approach via percutaneous occluding device or transcatheter aortic valve implantation. In the present review, we describe the interaction between AV and LVAD placement, in terms of patient management and prognosis. Also it is provided a comprehensive echocardiographic strategy for the precise assessment of AV regurgitation severity.

Concomitant or late aortic valve intervention and its efficacy for aortic insufficiency associated with continuous-flow left ventricular assist device implantation

Moderate to severe aortic insufficiency (AI) in patients who underwent continuous-flow left ventricular assist device (CF-LVAD) implantation is a significant complication. According to the INTERMACS registry analysis, at least mild AI occurs in 55% of patients at 6 months after CF-LVAD implantation and moderate to severe AI is significantly associated with higher rates of re-hospitalization and mortality. The clinical implications of these data may underscore consideration of prophylactic aortic valve replacement, or repair, at the time of CF-LVAD implantation, particularly with expected longer duration of support and in patients with preexisting AI that is more than mild. More crucially, even if a native aortic valve is seemingly competent at the time of VAD implantation, we frequently find de novo AI as time goes by, potentially due to commissural fusion in the setting of inconsistent aortic valve opening or persistent valve closure caused by CF-LVAD support, that alters morphological and functional properties of innately competent aortic valves. Therefore, close monitoring of AI is mandatory, as the prognostic nature of its longitudinal progression is still unclear. Clearly, significant AI during VAD support warrants surgical intervention at the appropriate timing, especially in patients of destination therapy. Nonetheless, such an uncertainty in the progression of AI translates to a lack of consensus regarding the management of this untoward complication. In practice, proposed surgical options are aortic valve replacement, repair, closure, and more recently transcatheter aortic valve implantation or closure. Transcatheter approach is of course less invasive, however, its efficacy in terms of long-term outcome is limited. In this review, we summarize the recent evidence related to the pathophysiology and surgical treatment of AI associated with CF-LVAD implantation.

Impact of progressive aortic regurgitation on outcomes after left ventricular assist device implantation

Aortic regurgitation (AR) following continuous flow left ventricular assist device implantation (cf-LVAD) may adversely impact outcomes. We aimed to assess the incidence and impact of progressive AR after cf-LVAD on prognosis, biomarkers, functional capacity and echocardiographic findings. In an analysis of the PCHF-VAD database encompassing 12 European heart failure centers, patients were dichotomized according to the progression of AR following LVAD implantation. Patients with de-novo AR or AR progression (AR_1) were compared to patients without worsening AR (AR_0). Among 396 patients (mean age 53 ± 12 years, 82% male), 153 (39%) experienced progression of AR over a median of 1.4 years on LVAD support. Before LVAD implantation, AR_1 patients were less frequently diabetic, had lower body mass indices and higher baseline NT-proBNP values. Progressive AR did not adversely impact mortality (26% in both groups, HR 0.91 [95% CI 0.61-1.36]; P = 0.65). No intergroup variability was observed in NT-proBNP values and 6-minute walk test results at index hospitalization discharge and at 6-month follow-up. However, AR_1 patients were more likely to remain in NYHA class III and had worse right ventricular function at 6-month follow-up. Lack of aortic valve opening was related to de-novo or worsening AR (P < 0.001), irrespective of systolic blood pressure (P = 0.67). Patients commonly experience de-novo or worsening AR when exposed to continuous flow of contemporary LVADs. While reducing effective forward flow, worsening AR did not influence survival. However, less complete functional recovery and worse RV performance among AR_1 patients were observed. Lack of aortic valve opening was associated with progressive AR.

Factors influencing the functional status of aortic valve in ovine models supported by continuous-flow left ventricular assist device

Objectives

An acute animal experiment was performed to observe factors influencing the functional status of the aortic valve functional status after continuous‐flow left ventricular assist device (CF‐LVAD) implantation in an ovine model, and a physiologic predictive model was established.

Methods

A CF‐LVAD model was established in Small Tail Han sheep. The initial heart rate (HR) was set to 60 beats/min, and grouping was performed at an interval of 20 beats/min. In all groups, the pump speed was started from 2000 rpm and was gradually increased by 50–100 rpm. A multi‐channel physiological recorder recorded the HR, aortic pressure, central venous pressure, and left ventricular systolic pressure (LVSP). A double‐channel ultrasonic flowmeter was used to obtain real‐time artificial vascular blood flow (ABF). A color Doppler ultrasound device was applied to assess the aortic valve functional status. Multivariate dichotomous logistic regression was used to screen significant variables for predicting the functional status of the aortic valve.

Results

Observational studies showed that ABF and the risk of aortic valve closure (AVC) were positively correlated with pump speed at the same HR. Meanwhile, the mean arterial pressure (MAP) was unaltered or slightly increased with increased pump speed. When the pump speed was constant, an increase in HR was associated with a decrease in the size of the aortic valve opening. This phenomenon was accompanied by an initial transient increase in the ABF and MAP, which subsequently decreased. Statistical analysis showed that the AVC was associated with increased pump speed (OR = 1.02, 95% CI = 1.01–1.04, p = 0.001), decreased LVSP (OR = 0.95, 95% CI = 0.91–0.98, p = 0.003), and decreased pulse pressure (OR = 0.82, 95% CI = 0.68–0.96, p = 0.026). ABF or MAP was negatively associated with the risk of AVC (OR < 1). The prediction model of AVC after CF‐LVAD implantation exhibited good differentiation (AUC = 0.973, 95% CI = 0.978–0.995) and calibration performance (Hosmer–Lemeshow χ² = 9.834, p = 0.277 > 0.05).

Conclusions

The pump speed, LVSP, ABF, MAP, and pulse pressure are significant predictors of the risk of AVC. Predictive models built from these predictors yielded good performance in differentiating aortic valve opening and closure after CF‐LVAD implantation.

Physiology of Continuous-Flow Left Ventricular Assist Device Therapy

The expanding use of continuous-flow left ventricular assist devices (CF-LVADs) for end-stage heart failure warrants familiarity with the physiologic interaction of the device with the native circulation. Contemporary devices utilize predominantly centrifugal flow and, to a lesser extent, axial flow rotors that vary with respect to their intrinsic flow characteristics. Flow can be manipulated with adjustments to preload and afterload as in the native heart, and ascertainment of the predicted effects is provided by differential pressure-flow (H-Q) curves or loops. Valvular heart disease, especially aortic regurgitation, may significantly affect adequacy of mechanical support. In contrast, atrioventricular and ventriculoventricular timing is of less certain significance. Although beneficial effects of device therapy are typically seen due to enhanced distal perfusion, unloading of the left ventricle and atrium, and amelioration of secondary pulmonary hypertension, negative effects of CF-LVAD therapy on right ventricular filling and function, through right-sided loading and septal interaction, can make optimization challenging. Additionally, a lack of pulsatile energy provided by CF-LVAD therapy has physiologic consequences for end-organ function and may be responsible for a series of adverse effects. Rheological effects of intravascular pumps, especially shear stress exposure, result in platelet activation and hemolysis, which may result in both thrombotic and hemorrhagic consequences. Development of novel solutions for untoward device-circulatory interactions will facilitate hemodynamic support while mitigating adverse events. © 2021 American Physiological Society. Compr Physiol 12:1-37, 2021.

Can the intermittent low-speed function of left ventricular assist device prevent aortic insufficiency?

Aortic insufficiency (AI) is known to associate with a persistently closed aortic valve during continuous-flow ventricular assist device support. Some devices carry an intermittent low-speed (ILS) function, which facilitates aortic valve opening, but whether this function prevents AI is unknown. In this study, the Jarvik 2000 device, which is programmed to reduce the pump speed each minute for 8 s, was chosen to examine this potential effect. Prospectively collected data of 85 heart transplant-eligible Jarvik 2000 recipients who met the study criteria (no pre-existing AI and aortic valve surgery) were retrospectively analyzed for the incidence, correlating factors, and clinical outcomes of de novo AI. All data were provided by the Japanese Registry for Mechanically Assisted Circulatory Support. De novo AI occurred in 58 patients, 23 of whom developed at least moderate AI during a median support duration of 23.5 months. Freedom from moderate or greater AI was 84.4%, 66.1% and 60.2% at 1, 2 and 3 years, respectively. Multivariate analyses revealed that progressive AI was correlated with decreased pulse pressure after implantation (hazard ratio 1.060, 95% confidence interval 1.001–1.127, p = 0.045). No correlation was found for mortality or other adverse events, including stroke, bleeding, infection, pump failure, hemolysis, and readmission. The benefit of the Jarvik 2000′s current ILS mode against AI appears to be minimal. However, in this limited cohort where all recipients underwent implantation as a bridge to transplantation, the impact of de novo progressive AI on other clinical adversities was also minimal.

Continuous-Flow Left Ventricular Assist Devices and Valvular Heart Disease: A Comprehensive Review

Mechanical circulatory support with implantable durable continuous-flow left ventricular assist devices (CF-LVADs) represents an established surgical treatment option for patients with advanced heart failure refractory to guideline-directed medical therapy. CF-LVAD therapy has been demonstrated to offer significant survival, functional, and quality-of-life benefits. However, nearly one-half of patients with advanced heart failure undergoing implantation of a CF-LVAD have important valvular heart disease (VHD) present at the time of device implantation or develop VHD during support that can lead to worsening right or left ventricular dysfunction and result in development of recurrent heart failure, more frequent adverse events, and higher mortality. In this review, we summarize the recent evidence related to the pathophysiology and treatment of VHD in the setting of CF-LAVD support and include a review of the specific valve pathologies of aortic insufficiency (AI), mitral regurgitation (MR), and tricuspid regurgitation (TR). Recent data demonstrate an increasing appreciation and understanding of how VHD may adversely affect the hemodynamic benefits of CF-LVAD support. This is particularly relevant for MR, where increasing evidence now demonstrates that persistent MR after CF-LVAD implantation can contribute to worsening right heart failure and recurrent heart failure symptoms. Standard surgical interventions and novel percutaneous approaches for treatment of VHD in the setting of CF-LVAD support, such as transcatheter aortic valve replacement or transcatheter mitral valve repair, are available, and indications to intervene for VHD in the setting of CF-LVAD support continue to evolve.

Practical valvular issues in patients requiring ventricular assist devices

PURPOSE OF REVIEW

As ventricular assist device (VAD) therapy in patients with advanced heart failure continues to grow, experience with concomitant valvular diseases present either before or after VAD implantation continues to accrue. In this review, we discuss recent data and current practice as it pertains to the subject of concomitant valvular disease in patients requiring VADs.

RECENT FINDINGS

Persistent aortic valve closure has been identified as a potential contributor to aortic valve 'disuse atrophy' resulting in valve degeneration. Dilation of the aortic root may be predictive of future development of aortic insufficiency. Novel echocardiographic parameters to identify the severity of aortic insufficiency following VAD implantation may be useful for risk stratification. Concomitant repair of significant mitral regurgitation may confer benefit to pulmonary vascular resistance and right ventricular function; however, this remains controversial. Concomitant repair of significant tricuspid regurgitation has not demonstrated early postoperative benefit nor survival benefit. Atrial fibrillation has emerged as a risk factor that may predict accelerated progression of postoperative tricuspid regurgitation.

SUMMARY

Management of aortic insufficiency, mitral regurgitation or tricuspid regurgitation in patients requiring VADs continues to be the source of controversy. As experience accrues with varying strategies to prevent or manage these valvular lesions, our understanding of the impact of these strategies continues to evolve.