Implantable left ventricular assist system.

The first clinical application of the first-generation pulsatile implantable left ventricular assist system (LVAS) was in the mid 1980 s as a bridge to transplantation and contributed to an advancement of this field from a clinical experiment to an established therapeutic option for treating advanced heart failure patients. However, there have been technological limitations that have surfaced as longer-term experience has been gained. These include a high incidence of thromboembolic complications, infection, mechanical failures associated with moving parts, and the large size of both implantable pump and percutaneous cable. In order to overcome the limitations of the first-generation pulsatile LVAS, a smaller rotary blood pump LVAS emerged as a possible alternative in the 1990 s and these new generation LVAS are in various stages of development and clinical application. This article reviews the history and current status of the implantable LVAS.

Effect of pump flow mode of novel left ventricular assist device upon end organ perfusion in dogs with doxorubicin induced heart failure.

End organ effects of nonpulsatile (NP) and pulsatile (P) left ventricular assist device (LVAD) flow were compared in a canine model of doxorubicin-induced heart failure. After heart failure induction, a prototype bimodal LVAD was implanted. Hemodynamics, cardiac dimensions, and myocardial metabolism were monitored with the LVAD off (baseline) and on (in NP and P modes at 70% or 100% power). End organ perfusion was assessed by colored microsphere analysis. Seven dogs were used: two died before pump implantation and were excluded from analysis, and the remaining five survived to study termination. At 70% NP, ascending aortic flow and myocardial oxygen consumption (MVO2) decreased significantly. At 100% NP, LV dimensions decreased, aortic systolic, pulse, and LV pressures decreased but not significantly, and ascending aorta flow reversed. At 100% NP, coronary blood flow, MVO2, and LV free wall subepicardial and subendocardial blood flows decreased significantly. However, as NP support increased, the subepicardial/subendocardial blood flow ratio remained near baseline. At 100% NP, right ventricular perfusion decreased but not significantly, cerebral perfusion decreased significantly, and renal perfusion stayed constant. P mode results were similar, except that ascending aorta flow decreased significantly at 100% P instead of reversing as at 100% NP. These results suggest that end organ perfusion is not differentially affected by LVAD flow mode during chronic heart failure.

[Implantable artificial heart].

Heart transplants have been decreasing globally due to the lack of available donor hearts. As a result, the increased use of artificial hearts is anticipated as an alternative therapy. Although biocompatibility issues, such as thrombus formation/thromboembolism and infection, are still the main cause of mortality associated with artificial hearts, more than 20 different types are now clinically available after a half-century of development and experimental trials. These devices range from extracorporeal pneumatic to implantable battery-powered artificial hearts. The early development of artificial hearts logically focused on volumetric pump designs incorporating functions similar to the natural heart. Today, development has shifted toward designs that are significantly different from the natural heart. These pumps utilize axial or centrifugal flow allowing for a much simpler design, which is smaller in size and has very few moving parts. With rapid advances in technology, this new generation of artificial heart pumps is beginning to emerge as an alternative to heart transplants.

End-organ function during chronic nonpulsatile circulation.

BACKGROUND: Evolving blood pump technology has produced user-friendly continuous flow left ventricular assist devices, but uncertainty exists about the safety of chronic nonpulsatile circulation. We established consistently nonpulsatile blood flow in a sheep model using the Terumo magnetically suspended centrifugal pump. We then compared end-organ function between pulseless and control animals. METHODS: Fifteen healthy sheep (65 to 85 kg) were allocated to either left ventricular assist device (n = 9) or control (n = 6) groups. We implanted the device through a left thoracotomy and determined the flow rate at which pulse pressure was absent. The flow rate was then adjusted to exceed that rate (4.2 +/- 1.5 L/min), and all variables of pump function were continuously monitored by computer. Blood tests were taken serially for hepatic and renal function and plasma renin levels. The sheep were sacrificed electively at 30 (n = 3), 90 (n = 4), 180 (n = 1), and 340 (n = 1) days. Detailed histologic examination was made of the brain, liver, kidney, myocardium, and major arteries. RESULTS: All animals remained in good condition until sacrifice. All measures of end-organ function remained within normal limits for both groups. There were no histologic differences between the organs of pulsatile and nonpulsatile animals. Although there was no significant difference in mean blood pressure, plasma renin levels were substantially elevated in pulseless animals (1.4 +/- 0.3 pg/mL versus 2.9 +/- 0.3 pg/mL; p < 0.05). We also identified thinning of the medial layer of the ascending aorta in nonpulsatile sheep (1.8 +/- 0.4 mm in left ventricular assist device animals versus 2.6 +/- 0.6 mm in control sheep; p < 0.05). CONCLUSIONS: Chronic nonpulsatile circulation was well tolerated, and we found neither functional nor histologic changes in major end organs. The renin-angiotensin system was upregulated, but this did not provide a significant rise in blood pressure. The changes in the aortic wall merit further investigation. As a result of these findings, we consider that nonpulsatile devices can be used safely for long-term circulatory support.

[Left ventricular assist system with a magnetically levitated impeller technology].

After the accumulation of clinical experience with the current generation of pulsatile implantable left ventricular assist systems (LVAS), these devices have demonstrated major limitations: high incidence of thromboembolic complications; large size; high infection rate; and limited long-term durability. To address the limitations of current-generation LVAS, second- and third-generation LVAS utilizing rotary blood pump technology are currently undergoing clinical trials and the final stage of product development. Among them, the rotary blood pump with a magnetically levitated impeller is one of the most promising pumps for long-term circulatory assist. The Terumo DuraHeart LVAS is one of the third-generation LVAS using a centrifugal pump with a magnetically levitated impeller. This article describes the characteristics of the DuraHeart LVAS and its development status.

DuraHeart magnetically levitated centrifugal left ventricular assist system for advanced heart failure patients.

The implantable left ventricular assist system (LVAS) using pulsatile pump technology has become an established therapeutic option for advanced heart failure patients. However, there have been technological limitations in some older designs, including a high incidence of infection and mechanical failures associated with moving parts, and the large size of both implantable pump and percutaneous cable. A smaller rotary blood pump emerged as a possible alternative to a large pulsatile pump to overcome some of these limitations. The technological advancement that defines the third-generation LVAS was the elimination of all mechanical contacts between the impeller and the drive mechanism. The DuraHeart LVAS is the world's first third-generation implantable LVAS to obtain market approval (CE-mark), which combines a centrifugal pump and active magnetic levitation. The initial clinical experience with the DuraHeart LVAS in Europe demonstrated that it provided significantly improved survival (85% at 6 months and 79% at 1 year), reduced adverse event rates and long-term device reliability (freedom from device replacement at 2 years: 96 +/- 3%) over pulsatile LVAS.

European experience of DuraHeart magnetically levitated centrifugal left ventricular assist system.

OBJECTIVE: The DuraHeart (Terumo Heart, Inc., Ann Arbor, Michigan, USA) is the world's first approved magnetically levitated centrifugal left ventricular assist system designed for long-term circulatory support. We report the clinical outcomes of 68 patients implanted with the DuraHeart as a bridge to cardiac transplantation in Europe. METHODS: Sixty-eight patients with advanced heart failure (six females), who were eligible for cardiac transplantation were implanted with the DuraHeart between January 2004 and July 2008. Median age was 58 (range: 29-74) years with 31% over 65 years. Thirty-three of these patients received the device as a part of the European multi-center clinical trial. Survival analyses were conducted for 68 patients and other safety and performance data were analyzed based on 33 trial patients. RESULTS: Mean support duration was 242+/-243 days (range: 19-1148, median: 161) with a cumulative duration of 45 years. Thirty-five patients (51%) remain ongoing, 18 transplanted, 1 explanted, and 14 died during support with a median time to death of 62 days. The Kaplan-Meier survival rate during support was 81% at 6 months and 77% at 1 year. Of the 13 patients (21%) supported for >1 year, 4 supported for >2 years, 1 supported >3 years, 2 transplanted, 2 died, and 9 ongoing with a mean duration of 744+/-216 days (range: 537-1148, median: 651). Major adverse events included driveline/pocket infection, stroke, bleeding, and right heart failure. There was no incidence of pump mechanical failure, pump thrombosis, or hemolysis. CONCLUSIONS: The DuraHeart was able to provide safe and reliable long-term circulatory support with an improved survival and an acceptable adverse event rate in advanced heart failure patients who were eligible for transplantation.

Implantation technique for the DuraHeart left ventricular assist system.

The DuraHeart is a centrifugal pump with a magnetically levitated impeller. We implant the DuraHeart blood pump, which is 72 mm in external diameter and 45 mm in height, in a preperitoneal pocket in the left upper abdomen. An apical cuff is sutured to the apical hole in the left ventricular apex with 12 mattress sutures of 3-0 Prolene pledgeted with Dacron felt. In the first six mattress sutures, the needle is exited from the apical hole after a full-thickness bite of myocardium, and in six additional mattress sutures, the needle is exited from the epicardial edge of the apical hole. Next, a double purse-string suture with 3-0 Prolene is placed on the Dacron pledgets around the apical hole. After the inflow conduit has been connected to the inlet port of the blood pump, the inflow conduit is secured to the apical cuff. The graft portion of the outflow conduit, which was connected to the blood pump beforehand, is sewn end-to-side to the ascending aorta with a 4-0 Prolene suture. Gentle suture connection of the apical cuff to the left ventricular apex and optimal alignment of the inflow conduit, which is bent by 60 degrees, are crucial in the surgical procedure. A detailed description of the implantation technique is presented to facilitate the use of this system.

The DuraHeart VAD, a magnetically levitated centrifugal pump: the University of Vienna bridge-to-transplant experience.

BACKGROUND: The clinical application of the DuraHeart (Terumo Heart Inc, USA) has begun in Europe as a clinical trial of a third-generation implantable centrifugal blood pump. Four successful clinical implants are presented. METHODS AND RESULTS: Four male patients had end-stage left heart failure and received a DuraHeart VAD as a left ventricular assist device for bridge-to-transplantation. The pump showed good performance with flow rates of 4.9+/-0.5 L/min after gradual weaning of extracorporeal circulation. The pump flow was then maintained at 6.1+/-0.5, 5.5+/-0.3, 5.5+/-0.1, 5.7+/-0.1, 5.5, 6.4 and 6.5 L/min at the 1st, 4th, 8th, 12th, 16th, 20th and 24th postoperative week, respectively. No significant elevation of mean plasma-free hemoglobin was detected. The patients were discharged on the 18th, 42nd, 41st and 31st postoperative day, respectively, and all were successfully transplanted on the 202nd, 84th, 128th and 96th postoperative day, respectively. At the time of transplant surfaces of the removed pumps were free from thrombus formation, although intraventricular pannus growth was observed around the inflow cannulae in all patients. CONCLUSION: The DuraHeart VAD showed stable and sufficient circulatory support for the bridge-to-transplant procedure in this cohort of 4 patients.

Mechanical circulatory support devices (MCSD) in Japan: current status and future directions.

The current status and future directions of mechanical circulatory support devices (MCSDs) in Japan are reviewed. Currently used clinical MCSDs, both domestic and imported systems and continuous flow devices that are coming into the clinical arena are emphasized. Clinical MCSDs include the extracorporeal pulsatile Toyobo and Zeon systems and the implantable Novacor and HeartMate I VE. A thorough review is presented of single-ventricle continuous flow MCSDs such as the Terumo DuraHeart and the SunMedical EVAHEART and the biventricular Miwatec/Baylor systems that are on the horizon. The future directions in management of end-stage cardiac patients with MCSDs are discussed, focusing on (1) device selection - pulsatile versus continuous flow devices; (2) single-ventricle support, biventricular support, or replacement; (3) bridge to transplantation, destination therapy, or bridge to recovery; and (4) government regulatory processes and the medical industry. We hope to promote the quality of life (QOL) of end-stage cardiac patients as well as the medical industry in Japan.