Axial and centrifugal continuous-flow rotary pumps: a translation from pump mechanics to clinical practice

Extracorporeal life support: updates and controversies

The use of Extracorporeal Life Support (ECLS) in children and adults has markedly increased during the past few years with over 4000 patients placed on ECLS every year in over 200 centers. This article focuses on updates to the physiology and mechanics of ECLS with use of magnetically levitated centrifugal pumps, hollow-fiber gas-exchange devices, and bi-caval dual-lumen catheters. We also explore controversies in management including indications, cannulation approaches, renal replacement, monitoring of anticoagulation, early ambulation, and termination of ECLS. Finally, we present changes in the systems that provide ECLS including the single-provider model and regionalization of care.

Mechanical circulatory support devices in the ICU

The medical community has used implantable mechanical circulatory support devices at increasing rates for patients dying from heart failure and cardiogenic shock. Newer-generation devices offer a more durable and compact option when compared with bulky early-generation devices. This article is a succinct introduction and overview of the hemodynamic principles and complications after device implantation for ICU clinicians. We review the concepts of device physiology, clinical pearls for perioperative management, and common medical complications after device implantation.

Mechanical circulatory support in univentricular hearts: current management

Failing single-ventricle patients have now come into focus as the next cohort where improvement in outcomes for mechanical circulatory support can be realized. There is a paucity of published patient reports or management protocols in this patient population. Increased interest exists in finding answers of how to bridge these patients to transplant. We review the current literature and describe our approach to the patient with univentricular heart needing mechanical circulatory support.

Aortic insufficiency in patients with sustained left ventricular systolic dysfunction after axial flow assist device implantation

BACKGROUND

Predicting the occurrence of aortic insufficiency (AI) during left ventricular assist device (LVAD) support has remained unsolved.

METHODS AND RESULTS

We enrolled 52 patients who had received continuous flow LVAD (14 axial and 38 centrifugal pumps) and who been followed for ≥6 months between Jun 2006 and Dec 2013. Native aortic valve (AV) opening was observed in 18 patients (35%) with improved LV systolic function, and none of them had AI. On multivariate logistic regression analysis preoperative shorter heart failure duration was the only independent predictor of postoperative native AV opening (P=0.042; odds ratio [OR], 0.999). Of the remaining 34 patients (65%) with closed AV, 11 had AI with enlargement of the aortic root and narrow pulse pressure. Among those with closed AV, axial pump use (n=13) was the only significant predictor of the development of AI (P=0.042; OR, 4.950). Patients with AI had lower exercise capacity and a higher readmission rate than those without AI during 2-year LVAD support (55% vs. 8%; P<0.001).

CONCLUSIONS

Native AV opening during LVAD support is profoundly associated with reversal of LV systolic function, especially in patients with preoperative shorter heart failure duration. Among those in whom the native AV remains closed, low pulsatility of axial flow pump may facilitate aortic root remodeling and post-LVAD AI development that results in worse clinical outcome.

Lessons learned from the first fully magnetically levitated centrifugal LVAD trial in the United States: the DuraHeart trial

BACKGROUND

The DuraHeart is a continuous centrifugal-flow left ventricular assist device that uses active magnetic levitation for impeller positioning designed for improved hemocompatibility and durability. This study reviews the results of the US trial with specific attention to hemolysis, thrombotic complications, and pump failure.

METHODS

The US SUSTAIN trial was a multicenter, prospective, single-arm observational study in advanced heart failure patients listed for transplantation. Follow-up was complete in 100% of the patients at 6 months.

RESULTS

Sixty-three patients were enrolled at 23 centers. Forty-six patients (73%) reached the primary end points of survival to transplantation, alive on the original device at 180 days and listed for transplantation, or explant for recovery. Median duration of support was 267 days (range, 10 to 952 days) with a total support time of 46 patient-years. There was no clinical hemolysis reported during the study. Mean lactate dehydrogenase values peaked at day 4 and significantly decreased during support (435±236 U/L and 297±142 U/L on day 3 and day 180, respectively). There were no cases of pump thrombosis reported, and 3 cases of pump thrombus "in transit" (0.06 events/patient-year) were observed. There were 6 (10%) cases of magnetic levitation system failure, all secondary to cable wire fractures (0.12 events/patient-year). All patients were hemodynamically stable with the backup hydrodynamic mode. Major adverse events included gastrointestinal bleeding (0.52 events/patient-year), ischemic and hemorrhagic strokes (0.17 events/patient-year and 0.09 events/patient-year, respectively), and driveline infections (0.67 events/patient-year).

CONCLUSIONS

The DuraHeart demonstrated good hemocompatibility; however, the reliability of full magnetic levitation systems should be a high priority in future pump designs.

Outcomes of continuous flow ventricular assist devices

Heart transplantation is commonplace, the supply is limited. Many exciting changes in the field of mechanical circulatory support have occurred in the past few years, including the axial flow pump. Left ventricular assist device (LVAD) therapy is ever evolving. As the use of LVAD therapy increases it is important to understand the indications, surgical considerations and outcomes.

A comparison study of haemolysis production in three contemporary centrifugal pumps

One challenge in providing extracorporeal circulation is to supply optimal flow while minimising adverse effects, such as haemolysis. To determine if the recent generation constrained vortex pumps with their inherent design improvements would lead to reduced red cell trauma, we undertook a study comparing three devices. Utilizing a simulated short-term ventricular assist circuit primed with whole human blood, we examined changes in plasma free haemoglobin values over a six-day period. The three pumps investigated were the Maquet Rotaflow, the Levitronix PediVAS and the Medos Deltastream DP3.This study demonstrated that all three pumps produced low levels of haemolysis and are suitable for use in a clinical environment. The Levitronix PediVAS was significantly less haemolytic than either the Rotaflow (p<0.05) or the DP3 (p<0.05). There was no significant difference in plasma free haemoglobin between the Rotaflow and the DP3 (p=0.71).