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PubMed2002

Mechanical circulatory support: new advances, new pumps, new ideas.

Mechanical circulatory support (MCS) is a viable therapy for severe end-stage heart disease. Most obstacles to long-term MCS therapy have been overcome, and a number of clinical trials, including the recent REMATCH trial, have shown a clear benefit in terms of survival and improved quality of life. MCS should therefore no longer be considered as simply a temporary bridge to other therapies, but also a destination therapy whose potential should continue to expand through the development and use of newer, more innovative devices such as continuous flow pumps, next-generation centrifugal pumps, and total artificial hearts. The homebound heart failure patient and the patient facing imminent death from massive myocardial infarction receive little statistical benefit from current therapies, and the new and evolving MCS technologies offer the potential for effective therapy to these desperately ill patients.

Assisted Circulation↗
PubMed1991

Evolving experience with mechanical circulatory support.

Since 1985 total mechanical circulatory support for mortally ill transplant candidates has been progressively integrated into the authors' program. During this period 379 patients underwent transplantation. Of this group of patients, 62 required some form of mechanical support other than the intra-aortic balloon pump. Because intra-aortic balloon pump assist was limited in therapeutic effect and was associated with patient immobility and line-related sepsis, the next logical step toward support was the artificial heart. Of 20 patients implanted with the Jarvik heart, 17 underwent transplantation, but only 9 of these survived to discharge. In 1988, the authors abandoned the preferential use of the total artificial heart because of excessive cumulative probability of death from wound infection. They began to use the Novacor electrical assist device with the percutaneous power cord because they believed that univentricular support would be adequate for most patients, because its heterotopic position would reduce the likelihood of infection, and because it had the potential for chronic implantation. Twenty-three patients with biventricular failure (right ventricular ejection fraction less than 20%, 18/23) received the electrical assist device for an average of 50.4 days (range 1-193 days). All 17 transplanted patients survived until discharge. Only one of the five deaths that occurred after implantation, but without transplantation, was due to infection (candidiasis). Remarkably, all patients who survived the perioperative period ultimately survived with univentricular support alone. Based on this experience, survival of mechanically supported patients is now comparable to that of those less mortally ill.

Adolescent↗
PubMed1985

Anatomicomechanical study for the hydraulic line of a thermal left ventricular assist system.

A thermal left ventricular assist system currently under development consists of two separate major components, i.e., a pump/actuator module and an engine/thermal battery module. The possible implantation site of the engine/battery module is tentatively determined to be the iliac fossa, which requires a flexible interconnecting line to the pump/actuator module. A quantitative and biomechanical study was done on the effect of the implanted hydraulic line on the bendability of the torso. It revealed that the semirigid interconnecting line would not severely restrict the movement of the patient provided it has the proper prebend configuration. The cadaver fitting study proved the anatomical feasibility of the retroperitoneal iliac fossa as the implant site of the Thermal Ventricular Assist System 8 (TVAS 8) engine/battery module. The location and configuration of the interconnecting line of the TVAS 8 were determined using biomechanical analysis so that the restriction of the body movement due to the line could be minimized. The main route of the line was the left side of the trunk, and the line is W shaped in configuration. The line elongation is the most critical resistive factor and accordingly there may still be rigidity during lateral flexion.

Assisted Circulation↗
PubMed1997

Hydraulic assessment of the floating impeller phenomena in a centrifugal pump.

A compact eccentric inlet port centrifugal blood pump (C1E3) has been perfected for a long-term centrifugal ventricular assist device as well as a cardiopulmonary bypass pump. The C1E3 pump incorporates a sealless design and a blood stagnation free structure. The pump's impeller is magnetically coupled to the driver magnet in a sealless manner. The latest hemolysis study reveals that hemolysis is affected by the magnetic coupling distance between the driver and impeller magnet. Furthermore, a floating phenomenon can be observed in a pivot bearing supported pump. Attention was focused on the relationship between the floating phenomenon's characteristics and the magnetic coupling design in the C1E3 pump. Studies were conducted to evaluate the hydromechanical performance in the floating phenomenon. In this study, the relationship between the magnetic coupling design and the floating phenomenon was verified with a smooth spinning condition. The optimized magnetic coupling distance for the floating mode was estimated to be 12 mm for left ventricular assist device and 9 mm for cardiopulmonary bypass pump. Obtaining an optimal spinning condition is required for regulating the magnetic coupling force. To develop a double pivot bearing pump, it is necessary to establish an optimal spinning and/or floating condition and to determine the proper magnetic coupling and magnetic force between the impeller and driver.

Assisted Circulation↗
PubMed2002

Circulatory support for OPCAB procedures.

During off-pump coronary artery bypass grafting (OPCAB) which allows complete revascularization through a median sternotomy, revascularization of the lateral and posterior walls requires the verticalization of the heart, which may cause haemodynamic disturbance. This concern has stimulated the development of circulatory support with mini-pumps. Initially, these pumps were designed for the right side of the heart, which was found to be the main contributor to haemodynamic instability under experimental conditions. The three types of mini-pumps that have been developed so far - two for the right side of the heart and one for both sides - are reviewed as well as a new concept of integrated cardiopulmonary bypass (CPB) circuit with reduced surface and priming volume. However, with increasing experience and improved methods of exposition, OPCAB has become a procedure that can be performed without support in the majority of the cases. Nevertheless, the concept of miniaturization and the possibility to insert these devices through a peripheral access has opened the way to new indications, mainly short-term circulatory support for acute heart failure. This development is welcome in a field where available devices are invasive and plagued with a heavy morbidity.

Assisted Circulation↗
PubMed2000

[Circulatory support with the mechanical heart, "HeartMate"].

Treatment with the mechanical heart, HeartMate, has been introduced in Denmark. Short-term circulatory support can be obtained by intraaortic balloon counterpulsation, an external centrifugal pump and the total artificial heart. Long-term circulatory support can be established by treatment with the HeartMate. The principle of the mechanical heart is simple--a pump is implanted in parallel to the existing heart and connected to external, portable batteries. The patient quickly improves and is brought in an optimal state for transplantation. A few patients have been able to omit the subsequent heart transplantation. The patient's own heart improved during the treatment and the native heart functioned again after the system was explanted. The main complications during treatment are bleeding, infection, thromboembolic events and systemic failure. Permanent, fully implantable mechanical circulatory pumps are under development--which may herald the beginning of a whole new era for treatment of cardiac failure.

Assisted Circulation↗
PubMedDate not supplied

Percutaneous cardiopulmonary support in cardiac arrest.

Of 11 patients who underwent emergency resuscitation from cardiac arrest using a system of percutaneous cardiopulmonary support (CPS), two (18%) were long-term survivors. Percutaneous cardiopulmonary support was instituted without complication in all patients, with flows ranging from 1.8 to 5.5 L/min; the average duration of support was 304.3 min. All four patients who underwent emergency surgery (two coronary revascularization, one mitral valve revascularization, one mitral valve replacement with coronary revascularization, and one primary left ventricular assist device insertion) died. One patient died while on CPS secondary to irreversible ventricular arrhythmias after a successful percutaneous transluminal coronary angioplasty (PTCA). Six patients were weaned from the support system, three of whom had undergone PTCA while on CPS. The two survivors were the youngest patients (33 and 24 years). One of them had severe hypothyroidism as the cause of cardiac arrest, and the second was a hypothermia patient who was in ventricular fibrillation for 2 hr before establishing CPS. In comparing survivors (two) to nonsurvivors (nine), a significant difference (p = 0.034) in age was found, with survivors being younger. There was also a difference in incidence of atherosclerotic cardiovascular disease (p = 0.018), with survivors having none. There was no difference in the time to CPS (p = 0.905) or time on CPS (p = 0.156). Cardiopulmonary support can be instituted, resulting in excellent stabilization in patients with cardiac arrest. Survivors tended to be young and not have atherosclerotic cardiovascular disease (ASCVD) as their primary diagnosis. Neither length of cardiac arrest before CPS nor time on support correlated with a poor outcome.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Stimulated preconditioned skeletal muscle cardiomyoplasty. An effective means of cardiac assist.

Skeletal muscle grafts can be used to mechanically assist the failing heart. In 13 mongrel dogs, latissimus dorsi muscle was preconditioned in situ for 6-8 weeks. Biopsy samples of the muscles were obtained for histochemical analysis. In seven dogs, muscle force and fatigue were compared in conditioned and contralateral unconditioned (controls) muscles. In six dogs, latissimus dorsi cardiomyoplasty was performed in propranolol-induced acute heart failure, and its effects were evaluated by hemodynamic and echocardiographic parameters. Muscle conditioning was responsible for latissimus dorsi transformation to a muscle with predominantly fatigue-resistant type I fibers. Conditioned muscles developed less initial force (-27 +/- 6%) and a longer contraction time (+32 +/- 4%) (p less than 0.05) but did not show fatigue for less than 15 minutes. With synchronous pulse-train stimulation of the muscle flap, cardiac output increased from 1.4 +/- 0.1 (mean +/- SD) to 2.0 +/- 0.2 l/min (p less than 0.05), pulmonary wedge pressure decreased from 16.3 +/- 0.9 to 12.1 +/- 1.4 mm Hg (p less than 0.05), and left ventricular end-diastolic pressure decreased from 18 +/- 2.0 to 13.5 +/- 1.4 mm Hg (p less than 0.05). Echocardiographically derived ejection fraction increased from 39.3 +/- 2.4% to 59.6 +/- 2.9% (p less than 0.05), and fractional shortening increased from 15.4 +/- 1.1% to 26.3 +/- 1.7% (p less than 0.05). Thus, chronic stimulation of skeletal muscles induces fiber transformation and increases resistance to fatigue and force development. Cardiomyoplasty, on the other hand, improves ventricular function in the presence of acute heart failure. This surgical technique represents an alternative method of treatment for advanced myocardial failure.

Animals↗
PubMed1988

Nursing care of the patient with a pneumatic ventricular assist device.

Recent technologic advances have led to the development of safe and effective mechanical ventricular assist devices for clinical use. Pneumatic assist devices are being used at an increasing rate at a limited number of institutions throughout the country. One of the major factors in influencing survival of these critically ill patients is establishing standards of nursing care. We recently reviewed our experience of 41 patients who received a Pierce-Donachy ventricular assist device to evaluate the effectiveness of nursing care being provided to these patients. This article includes our most recent protocols of nursing care, which have evolved over the past 6 years. Nursing interventions to prevent or treat common complications such as bleeding, renal failure, and infection are discussed.

Assisted Circulation↗