Validation of non-invasive ramp testing for HeartMate 3

Preoperative anatomical landmarks and longitudinal HeartMate 3 pump position in X-rays: Relevance for adverse events

BACKGROUND

Left ventricular assist device (LVAD) malposition has been linked to hemocompatibility-related adverse events (HRAEs). This study aimed to identify preoperative anatomical landmarks and postoperative pump position, associated with HRAEs during LVAD support.

METHODS

Pre- and postoperative chest X-ray measures (≤14 days pre-implantation, first postoperative standing, 6, 12, 18, and 24 months post-implantation) were analyzed for their association with HRAEs over 24 months in 33 HeartMate 3 (HM3) patients (15.2% female, age 66 (9.5) years).

RESULTS

HM3 patients with any HRAE showed significantly lower preoperative distances between left ventricle and thoracic outline (dLVT) (25.3 ± 10.2 mm vs. 40.3 ± 15.5 mm, p = 0.004). A ROC-derived cutoff dLVT ≤ 29.2 mm provided 85.7% sensitivity and 72.2% specificity predicting any HRAE during HM3 support (76.2% (>29.2 mm) vs. 16.7% (≤29.2 mm) freedom from HRAE, p < 0.001) and significant differences in cardiothoracic ratio (0.58 ± 0.04 vs. 0.62 ± 0.04, p = 0.045). Postoperative X-rays indicated lower pump depths in patients with ischemic strokes (9.1 ± 16.2 mm vs. 38.0 ± 18.5 mm, p = 0.007), reduced freedom from any neurological event (pump depth ≤ 28.7 mm: 45.5% vs. 94.1%, p = 0.004), and a significant correlation between pump depth and inflow cannula angle (r = 0.66, p < 0.001). Longitudinal changes were observed in heart-pump width (F(4,60) = 5.61, p < 0.001).

CONCLUSION

Preoperative X-ray markers are associated with postoperative HRAE occurrence. Applying this knowledge in clinical practice may enhance risk stratification, guide therapy optimization, and improve HM3 recipient management.

Echocardiographic haemodynamic monitoring in the context of HeartMate 3™ therapy: a systematic review

AIMS

While echocardiography remains essential within haemodynamic monitoring of durable mechanical circulatory support, previous echocardiographic guidelines are missing scientific evidence for the novel HeartMate 3™ (HM3) system. Accordingly, this review aims to summarize available echocardiographic evidence including HM3.

METHODS AND RESULTS

This systematic review adhered to the PRISMA 2020 guidelines. Searches were conducted during August 2023 across PubMed, Embase, and Google Scholar using specific echocardiographic terms combined with system identifiers. Study quality was assessed using the Newcastle-Ottawa Scale (NOS) for cohort studies and Critical Appraisal Instrument (PCAI) for cross-sectional studies. Nine studies met the inclusion criteria, of which eight cohort studies and one cross-sectional study. Aortic regurgitation (AR) prevalence at approximately 12 months of support exhibited heterogenicity (33.5% (Δ 33%)) in a limited number of studies (n = 3). Several studies (n = 5) demonstrated an increasing prevalence and severity of AR during HM3 support, generating moderate to high level of evidence. One AR study showed a higher cumulative incidence of death and heart failure (HF) readmission compared with those without significant AR, hazard ratio 3.42 (95% CI 1.48-8.76). A second study showed that a worsening AR group had significantly lower survival-free from HF readmission (59% vs. 89%, P = 0.023) with a hazard ratio of 5.18 (95% CI 1.07-25.0), while a third study did not reveal any differences in cardiac-related hospitalizations in the 12 months follow-up or non-cardiac-related hospitalization. Mitral regurgitation (MR) prevalence at approximately 12 months of support exhibited good consistency 15.0% (Δ 0.8%) in both included studies, which did not reveal any significant pattern of changing prevalence over time. Tricuspid regurgitation (TR) prevalence at approximately 12 months of support exhibited fair consistency 28.5% (Δ 8.3%) in a limited number of studies (n = 2); both studies showed a statistically un-confirmed trend of increased TR prevalence over time. The evidence of general prevalence of right ventricular dysfunction (RVD) was insufficient due to lack of studies.

CONCLUSIONS

There are few methodologically consistent studies with focus on long-term haemodynamic effects. Aortic regurgitation still seems to be a prevalent and potentially significant finding. The available evidence concerning right heart function is limited despite clinical relevance and potential prognostic value. Potential interventricular and haemodynamic interplay are identified as a white field for future research.

Acute right ventricular geometric change predicts outcomes in HeartMate 3 patients

BACKGROUND

The physiological response of the right ventricle (RV) following left ventricular assist device (LVAD) implantation is difficult to predict. We aimed to investigate RV geometric and functional changes after LVAD insertion and their effects on clinical outcomes.

METHODS

We retrospectively reviewed 188 patients who underwent HeartMate 3 implantation at our center between November 2014 and September 2021. The RV end-diastolic diameter (RVEDD) and RV end-diastolic area (RVEDA) were measured on preoperative and predischarge transthoracic echocardiography. The nonadapted group included patients with increased RVEDD and RVEDA at discharge. The composite outcome was defined as death or readmission due to worsening right heart failure.

RESULTS

There were 82 patients (44%) who had a nonadapted and 106 patients (56%) who had an adapted RV. Preoperatively, the nonadapted group had smaller RVEDD (46 vs 49 mm, p < 0.001) and RVEDA (27 vs 31 cm2, p < 0.001). At discharge, the nonadapted group had larger RVEDD (51 vs 43 mm, p < 0.001) and RVEDA (33 vs 27 cm2, p < 0.001). Kaplan-Meier analysis demonstrated worse 3-year survival (77% vs 91%, p = 0.006) and freedom from composite outcome (58% vs 85%, p < 0.001) in the nonadapted group. A multivariable Cox proportional hazards model showed that nonadaption (hazard ratio [HR] 3.09, 95% confidence interval [CI] 1.29-7.40, p = 0.01) and age (HR 3.73, 95% CI 1.42-9.77, p = 0.007) were independent predictors of composite outcome.

CONCLUSIONS

Acute RV dimensional changes after LVAD insertion may represent intrinsic RV function and may be a useful prognostic marker.

HeartMate 3 Snoopy: Noninvasive cardiovascular diagnosis of patients with fully magnetically levitated blood pumps during echocardiographic speed ramp tests and Valsalva maneuvers

PURPOSE

The HeartMate 3 (HM3) left ventricular assist device (LVAD) has demonstrated excellent clinical outcomes; however, pump speed optimization is challenging with the available HM3 monitoring. Therefore, this study reports on clinical HM3 parameters collected with a noninvasive HM3 monitoring system (HM3 Snoopy) during echocardiographic speed ramp tests and Valsalva maneuvers.

METHODS

In this prospective, single-center study, the HM3 data communication between the controller and pump was recorded with a novel data acquisition system. Twelve pump parameters sampled every second (1 Hz) and clinical assessments (echocardiography, electrocardiogram (ECG), and blood pressure measurement) during speed ramp tests were analyzed using Pearson's correlation (r, median [IQR]). The cause for the occurrence of pulsatility index (PI)-events during ramp speed tests and valsalva maneuvers was investigated.

RESULTS

In 24 patients (age: 58.9 ± 8.8 years, body mass index: 28.1 ± 5.1 kg/m2, female: 20.8%), 35 speed ramp tests were performed with speed changes in the range of ±1000 rpm from a baseline speed of 5443 ± 244 rpm. Eight HM3 pump parameters from estimated flow, motor current, and LVAD speed together with blood pressure showed positive collinearities (r = 0.9 [0.1]). Negative collinearities were observed for pump flow pulsatility, pulsatility index, rotor noise, and left ventricular diameters (r = -0.8 [0.1]), whereas rotor displacement and heartrate showed absence of collinearities (r = -0.1 [0.08]).

CONCLUSIONS

In this study, the HM3 Snoopy was successfully used to acquire more parameters from the HM3 at a higher sampling rate. Analysis of HM3 per-second data provide additional clinical diagnostic information on heart-pump interactions and cause of PI-events.

The role of innovative modeling and imaging techniques in improving outcomes in patients with LVAD

Heart failure remains a significant cause of mortality in the United States and around the world. While organ transplantation is acknowledged as the gold standard treatment for end stage heart failure, supply is limited, and many patients are treated with left ventricular assist devices (LVADs). LVADs extend and improve patients' lives, but they are not without their own complications, particularly the hemocompatibility related adverse events (HRAE) including stroke, bleeding and pump thrombosis. Mainstream imaging techniques currently in use to assess appropriate device function and troubleshoot complications, such as echocardiography and cardiac computed tomography, provide some insight but do not provide a holistic understanding of pump induced flow alterations that leads to HRAEs. In contrast, there are technologies restricted to the benchtop-such as computational fluid dynamics and mock circulatory loops paired with methods like particle image velocimetry-that can assess flow metrics but have not been optimized for clinical care. In this review, we outline the potential role and current limitations of converging available technologies to produce novel imaging techniques, and the potential utility in evaluating hemodynamic flow to determine whether LVAD patients may be at higher risk of HRAEs. This addition to diagnostic and monitoring capabilities could improve prevention and treatment of LVAD-induced complications in heart failure patients.

Fuzzy-based modeling and speed optimization of a centrifugal blood pump using a modified and constrained Bees algorithm

BACKGROUND AND OBJECTIVE

Side effects that may occur when using blood pumps for treatment of patients are the main limitations on pump rotational speed determination. Efforts are being made to reduce side effects in both design and usage procedures. In determining the pump speed for treatment, decreasing the pressure on the main artery and preserving the valve functions are taken into consideration. In addition to these, the parameters considered for design which include pump efficiency and mechanical effects on blood cells, should also be taken into consideration. In this study, the aim is to obtain the optimum pump speed for the maximum hydraulic efficiency and minimum wall shear stresses that occur inside the pump.

METHODS

Blood pump modeling based on fuzzy logic is created on the hydraulic performance data of a centrifugal blood pump, whose design, CFD analysis, manufacture and experimental testing have been performed previously. Using this fuzzy logic model, the optimum pump speeds were determined using the Bees Algorithm, an intuitive optimization algorithm, in the operating range 1-7 L/min fluid flow rate. In the optimization process, the aim is to achieve minimum shear stress with maximal efficiency. Intravascular pressure limits (90-160 mm-Hg) were set as pressure constraints.

RESULTS

The optimum operating point is obtained as a 3350 rpm pump speed and a 4.35 L/min flow rate. At this operating point, CFD simulation is performed, and maximum wall shear stress was found to be 1458 Pa and its efficiency as 34.2%.

CONCLUSIONS

In addition to the parameters commonly used in the pump speed optimization of blood pumps, the use of wall shear stresses and pump efficiency can provide certain improvements.

Cardiac remodeling in patients with centrifugal left ventricular assist devices assessed by serial echocardiography

AIM

The aim of the study was to characterize the remodeling process in a large cohort of patients supported with a centrifugal left ventricular assist device (cfLVAD) by standardized serial echocardiography.

METHODS AND RESULTS

From 3/2018 all cfLVAD patients underwent transthoracic echocardiography at 6 and 12 months after implantation using a standardized protocol. A total of 512 echocardiograms were reviewed (216 preoperative, 156 at 6 months, 140 at 12 months). While on cfLVAD support, left ventricular (LV) diameter decreased (p < .001). LV ejection fraction (LVEF) and LV fractional area change improved (p < .001). Potential for cfLVAD explantation (as defined by an LVEF ≥45% and opening of the aortic valve [AV]) was seen in nine patients at 6 and 21 patients at 12 months. The tricuspid annular excursion decreased significantly, while the right ventricular fractional area change did not change. Tricuspid regurgitation (TR) and mitral regurgitation (MR) improved significantly during LVAD support. Opening of the AV was seen in >64% of the patients at 6 months and in 66% at 12 months. Moderate aortic regurgitation (AR) was rare with 3.8% at 6 months but increased with the duration of cfLVAD support (8.5% at 12 months). We found no significant difference in echocardiographic parameters between patients supported with a HeartWare HVAD™ or a HeartMate 3™ device.

CONCLUSION

LVAD therapy can lead to reverse LV remodeling and improvement of MR and TR. However, right ventricular function does not improve and prevalence of AR progressively increases during mechanical support.

Missing the blind spot in a HeartMate 3 outflow graft obstruction caused by fungal infection

A patient was admitted in cardiogenic shock and a constant decrease of pump flow requiring combined inotropic support. To evaluate the cause, echocardiography and a ramp test were performed. The results suggested a LVAD related problem - particularly a suspected outflow graft obstruction. Wether CT scan nor angiography confirmed the assumption. However, a post-mortem LVAD examination revealed an outflow obstruction caused by a fungal thrombus formation invisible for standard imaging procedures.

Influence of Atrial Fibrillation on Functional Tricuspid Regurgitation in Patients With HeartMate 3

Background

Functional tricuspid regurgitation (TR) can occur secondary to atrial fibrillation (AF). The impact of AF on functional TR and cardiovascular events is uncertain in patients with left ventricular assist devices. This study aimed to investigate the effect of AF on functional TR and cardiovascular events in patients with a HeartMate 3 left ventricular assist device.

Methods and Results

We retrospectively reviewed 133 patients who underwent HeartMate 3 implantation at our center between November 2014 and November 2018. We excluded patients who had undergone previous or concomitant tricuspid valve procedures and those whose echocardiographic images were of insufficient quality. The primary end point was death and the presence of a cardiovascular event at 1 year. We defined cardiovascular event as a composite of death, stroke, and hospital readmission due to recurrent heart failure and significant residual TR as vena contracta width ≥3 mm. In total, 110 patients were included in this analysis. Patients were divided into 3 groups: no AF (n=51), paroxysmal AF (n=40), and persistent AF (PeAF) (n=19). Kaplan‐Meier analysis showed that patients with PeAF had the worst survival (no AF 98%, paroxysmal AF 98%, PeAF 84%, log‐rank P=0.038) and event‐free rate (no AF 93%, paroxysmal AF 89%, PeAF 72%, log‐rank P=0.048) at 1 year. Thirty‐one (28%) patients had residual TR 1 month after left ventricular assist device implantation. Patients with residual TR had a significantly poor prognosis compared with those without residual TR (log‐rank P=0.014).

Conclusions

PeAF was associated with increased mortality, cardiovascular events, and residual TR compared with no AF and paroxysmal AF.

Implication of Hemodynamic Assessment during Durable Left Ventricular Assist Device Support

Durable left ventricular assist device therapy has improved survival in patients with advanced heart failure refractory to conventional medical therapy, although the readmission rates due to device-related comorbidities remain high. Left ventricular assist devices are designed to support a failing left ventricle through relief of congestion and improvement of cardiac output. However, many patients still have abnormal hemodynamics even though they may appear to be clinically stable. Furthermore, such abnormal hemodynamics are associated with an increased risk of future adverse events including recurrent heart failure, gastrointestinal bleeding, stroke, and pump thrombosis. Correction of residual hemodynamic derangements post-implantation may be a target in improving longitudinal clinical outcomes during left ventricular assist device support. Automatic and timely device speed adjustments considering a patients' hemodynamic status (i.e., with a smart pump) are potential improvements in forthcoming devices.

Validation of non-invasive ramp testing for HeartMate 3

Aims

Ramp testing in the postoperative period can be used to optimize left ventricular assist device (LVAD) speed for optimal left ventricular (LV) unloading. We tested the hypothesis that a non‐invasive echocardiographic ramp test post‐HeartMate 3 implantation improves LV unloading immediately after and 1–3 months after as compared with before the test. We also tested a secondary hypothesis that speed adjustments during echocardiography‐guided ramp testing do not worsen right ventricular (RV) function immediately after and 1–3 months after.

Methods and results

We retrospectively reviewed data from patients who underwent an echocardiographic ramp test. A total of 14 out of 19 patients were clinically stable and were enrolled. Adequate LV unloading was defined as no more than mild mitral regurgitation, and intermittent aortic valve (AV) opening or closed AV, and reduction of left ventricular end‐diastolic diameter (LVEDD); and for the follow‐up measurement, decreased NT‐proBNP. Median (interquartile range) time from implantation to ramp test was 27 (16; 56) days, and median time from ramp test to follow‐up echocardiography was 55 (47; 102) days. Median LVAD speed achieved during ramp testing was 5550 (5375; 6025) revolutions per minute (rpm), and median final LVAD speed was 5200 (5000; 5425) rpm. Ramp testing resulted in final LVAD speed increase in 11 (79%) patients and a median net change of 200 (200; 300) rpm. Speed adjustments after ramp testing resulted in improved LVAD unloading that was achieved in additional 3 (21%) patients who were not originally optimized. RV function did not worsen significantly during ramp testing or at final LVAD speed.

Conclusions

The echocardiographic ramp test allowed LVAD speed adjustment and optimization and improved LV unloading during ramp testing and at final speed with no evidence of worsening of RV function.