Left Atrial Circulatory Assistance in Simulated Diastolic Heart Failure Model: First in Vitro and in Vivo

Improving hydraulic performance of the left atrial assist device using computational fluid dynamics

BACKGROUND

The left atrial assist device (LAAD) is a novel continuous-flow pump designed to treat patients with heart failure with preserved ejection fraction, a growing type of heart failure, but with limited device-treatment options. The LAAD is implanted in the mitral plane and pumps blood from the left atrium into the left ventricle. The purpose of this study was to refine the initial design of the LAAD, using results from computational fluid dynamics (CFD) analyses to inform changes that could improve hydraulic performance and flow patterns within the LAAD.

METHODS

The initial design and three variations were simulated, exploring changes to the primary impeller blades, the housing shape, and the number, size, and curvature of the diffuser vanes. Several pump rotational speeds and flow rates spanning the intended range of use were modeled.

RESULTS

Guided by the insight gained from each design iteration, the final design incorporated impeller blades with improved alignment relative to the incoming flow and wider, more curved diffuser vanes that better aligned with the approaching flow from the volute. These design adjustments reduced flow separation within the impeller and diffuser regions. In vitro testing confirmed the CFD predicted improvement in the hydraulic performance of the revised LAAD flow path design.

CONCLUSIONS

The CFD results from this study provided insight into the key pump design-related parameters that can be adjusted to improve the LAAD's hydraulic performance and internal flow patterns. This work also provided a foundation for future studies assessing the LAAD's biocompatibility under clinical conditions.

Characterization of left atrial assist device implantation: Early results of ex vivo anatomical assessment

BACKGROUND

The left atrial assist device (LAAD) is a novel pump that was developed specifically for the treatment of heart failure with preserved ejection fraction. The device is surgically implanted in the mitral position. This study aimed to characterize the various device-fitting configurations in the mitral annular position.

METHODS

Rapidly prototyped LAAD models (n = 5) were fabricated with five different driveline configurations: (A) annulus level/intra-cuff running; (B) supra-cuff/below coronary sinus (CS); (C) infra-cuff; (D) supra-annulus/supra-CS; (E) left ventricular free wall level. The 3D-printed models were implanted in extracted fresh porcine hearts (80-100 kg, adult, healthy porcine) and the proximity of anatomical structures between the driveline and CS and coronary artery (CA) were measured.

RESULTS

All five device configurations were evaluated for fitting. For the purpose of preventing blood clot formation around the driveline, the mitral annulus (MA) as a driveline pass-way (configuration A) has been considered advantageous with the current device, in that the driveline exposure to blood has been avoided. The CS does not exist at exactly the same level as the MA, and there is less risk of injuring it than using the left atrial free wall. However, there is an inevitable risk of damaging the CA, so careful visual inspection before inserting the driveline is needed.

CONCLUSIONS

Several options of driveline exteriorization were demonstrated, and the safety of each configuration was evaluated. Using the MA as a pathway for the driveline exit is considered to be a reasonable and safe method.

New concepts in heart failure with preserved ejection fraction and hypertension

PURPOSE OF REVIEW

Hypertension (HTN) remains the most common and strongest contributing factor to the development of heart failure with preserved ejection fraction (HFpEF). In this review, we aim to summarize the pathophysiological processes linking HTN to HFpEF and highlight novel concepts in medical and device-based management of HFpEF and HTN.

RECENT FINDINGS

Despite the global increase in the prevalence of HFpEF, there has been limited benefit in current medication and device-based therapy for this complex syndrome. The hallmark of HFpEF is an elevated left intra-atrial and ventricular pressure and exertional dyspnea. Traditional medications used for treating HTN in patients with reduced left ventricular ejection fraction have unclear benefits in patients with HFpEF. Careful analysis of emerging medications such as angiotensin receptor-neprilysin inhibitor and sodium-glucose co-transporter-2 inhibitors showed benefit in reducing not only blood pressure but also hospitalizations in patients with HFpEF. Current data on device-based therapy aims to reduce left intra-atrial pressure, ventricular pressure and stimulate baroreceptors to lower blood pressure; however, needs further investigation.

SUMMARY

The nexus of HTN and HFpEF remains strong and complex. Although traditional medications for treating HFrEF did not affect long-term outcomes, novel therapies with angiotensin receptor neprilysin-inhibitor and sodium-glucose co-transporter-2 inhibitor offer promising results. Many device-based interventions in the HFpEF population are being developed with the aim to reduce left intra-atrial and ventricular pressure; however, their role in HFpEF hypertensive patients needs to be further investigated.

Novel approaches for left atrial pressure relief: Device-based monitoring and management in heart failure

The importance of the left atrium (LA) has been emphasized in recent years as the features of heart failure (HF), especially with regard to variability in patient and pathology phenotypes, continue to be uncovered. Of note, among the population with HF with preserved ejection fraction (HFpEF), pressure or size of the LA have become a target for advanced monitoring and a therapeutic approach. In the case of diastolic dysfunction or pulmonary hypertension, which are often observed in patients with HFpEF, a conventional approach with clinical symptoms and physical signs of decompensation turned out to have a poor correlation with LA pressure. Therefore, to optimize HF treatment for these populations, several devices that are applied directly to the LA have been developed. First, two LA pressure (LAP) sensors (Heart POD and V-LAP Device) were developed and may enable patient self-management remotely with LAP-guided and physician-directed style. Second, there are device-based approaches that aim to decompress the LA directly. These include: (1) interatrial shunt devices; (2) left ventricular assist devices with LA cannulation; and (3) the left atrial assist device. While these novel device-based therapies are not yet commercially available, there is expected to be a rise in the proposition and adoption of a wider range of choices for monitoring or treating LA using device-based options, based on LA dimensional reduction and optimization of the clinically significant pressure relief. Further development and evaluation are necessary to establish a more favorable management strategy for HF.