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At least 883 records · Page 49Linked to original sources
PubMed1998

Mechanical circulatory support for severe heart failure after operation.

To evaluate the clinical results of circulatory support for severe heart failure after operation, we examined 62 patients (39 males and 23 females) who underwent circulatory support for postoperative heart failure from 1984 to 1996. Their ages ranged from 22 to 78 (mean 52) years. In 62 patients, 35 had valvular, 25 had ischemic, and 2 had congenital heart disease. Postoperation, 29 patients underwent venoarterial bypass (VAB), 20 had biventricular bypass (BVB), and 8 had left ventricular bypass (LVB). The remaining 5 patients received a pulsatile left ventricular assist device (LVAD). The weaning and discharge rates of the patients by type of support were 51.7% and 31.0% with VAB, 75.0% and 55.0% with BVB, 87.5% and 37.5% with LVB, and 60.0% and 40.0% with LVAD, respectively. The complete results of this series (64.5% weaning rate and 40.3% discharge rate) were acceptable.

Adult↗
PubMed1987

Successful post-bypass ventricular assist with a centrifugal pump.

A 56 year old male with massive anterior wall infarction and development of a large aneurysm underwent aneurysmectomy and aorto-coronary bypass grafting to the RCA. Preoperative ejection fraction was 20%, LVedP was 30 mm Hg. During induction of anesthesia the patient sustained ventricular fibrillation and was successfully resuscitated. With the patient in progressive cardiogenic shock the operation was performed under emergency conditions. Despite adequate myocardial protection and cross-clamp time as well as prolonged reperfusion and balloon counterpulsation the patient could not be weaned off cardiopulmonary bypass. In this situation a centrifugal pump system was connected between the left atrium and the ascending aorta. With a pump flow of 5 l/min the patient was taken off cardiopulmonary bypass. After 20 hours of extracorporeal support without anticoagulation the device could be removed: explantation of the IABP followed 48 hours later. The patient gradually recovered and finally was discharged home in fair condition.

Assisted Circulation↗
PubMed2004

Computational fluid dynamics analysis of a maglev centrifugal left ventricular assist device.

The fluid dynamics of the Thoratec HeartMate III (Thoratec Corp., Pleasanton, CA, U.S.A.) left ventricular assist device are analyzed over a range of physiological operating conditions. The HeartMate III is a centrifugal flow pump with a magnetically suspended rotor. The complete pump was analyzed using computational fluid dynamics (CFD) analysis and experimental particle imaging flow visualization (PIFV). A comparison of CFD predictions to experimental imaging shows good agreement. Both CFD and experimental PIFV confirmed well-behaved flow fields in the main components of the HeartMate III pump: inlet, volute, and outlet. The HeartMate III is shown to exhibit clean flow features and good surface washing across its entire operating range.

Assisted Circulation↗
PubMed1993

The ventricular-synchronous, skeletal-muscle ventricle: preliminary feasibility studies.

The two requirements for the optimal use of skeletal muscle wrapped around a pouch used to pump blood are:(1) a low pouch diastolic pressure (to assure a high muscle capillary blood flow; and (2) a high pouch precontraction pressure (PCP) (to assure a forceful muscle contraction). Both requirements are satisfied with the pumping method described herein. This new type of skeletal-muscle ventricle (SMV) consists of a rectus abdominis muscle wrapped around a pouch connected to the left ventricular apex (with no valve) and to the aorta via a one-way valve. Consequently, the pressure in the SMV pouch is always equal to left ventricular pressure. The high PCP is obtained by stimulating the rectus muscle to contract at the desired left ventricular pressure. The R (or P) wave of the cardiac electrogram initiates a delayed train of stimuli to cause the rectus muscle to contract tetanically and expel blood from the pouch. We have designated this pumping configuration the ventricular-synchronous SMV (VS-SMV). In this study, eight acute anesthetized dogs were used. The muscles were unconditioned and among the items investigated were the importance of the delay (d) between the R (or P) wave and the onset of the stimulus train, the optimal stimulus frequency and train duration, the VS-SMV output with different ratios of VS-SMV to left ventricular contractions, unloading of the left ventricle, Frank-Starling curves for the VS-SMV, pressure-volume loops for the VS-SMV with and without contraction of the rectus muscle, and washout characteristics of the VS-SMV. It was found that a stimulus frequency of 40/sec, and a train duration of 250 msec is optimal. It was also found that choice of the proper delay from the R or P wave provided maximal augmentation in stroke volume, typically 20 to 40 mL. Pumping with a ratio of 1:2 provided VS-SMV outputs ranging from 20 to 140 mL/min per kg of body weight. With this same pumping ratio, cardiac output increased by 28% and the post-VS-SMV contraction, left ventricular stroke volume was reduced. The Frank-Starling curves showed that PCPs on the order of aortic pressure are needed for the most forceful muscle contraction. With this new pumping configuration, the left ventricle resembles an atrium which delivers blood to the VS-SMV that is stimulated to contract when the desired PCP is reached. Studies were also conducted in which the VS-SMV outlet (valve end) was closed and filling and emptying occurred through the left ventricle.(ABSTRACT TRUNCATED AT 400 WORDS)

Abdominal Muscles↗
PubMed2007

Percutaneous endocardial and epicardial ablation of hypotensive ventricular tachycardia with percutaneous left ventricular assist in the electrophysiology laboratory.

Ventricular tachycardia (VT) in the setting of structural heart disease is challenging to treat with percutaneous catheter ablation due to the presence of complex substrate, multiple morphologies, hemodynamic instability, and epicardial circuits. When substrate-based approaches fail, however, it may be impossible to map and ablate hemodynamically unstable arrhythmias. We describe a novel approach to endocardial and epicardial mapping and ablation of hypotensive VT using a percutaneous left ventricular assist device in the electrophysiology laboratory, permitting near-surgical access to cardiac structures.

Assisted Circulation↗
PubMed1992

Mechanical circulatory support in the 1990s.

The current experience in bridging patients to weaning (more than 965 implants) and to transplantation (more than 544 implants) has shown the feasibility of mechanical circulatory support in patients with major cardiac dysfunction, who are unresponsive to optimal medical management. The complications are mostly related to the patient's initial condition at the time of implantation. The rehabilitation of the patient is related to both the extent of recovery from organ dysfunction and the type of device. This analysis proposes some new orientations for research. Firstly, in clinical research, definition of precise indices of the patient condition, not exclusively related to the haemodynamic situation, should allow better patient and device selection. Secondly, in technological research, precise definition of the actual clinical objectives should help in the development of various systems: for resuscitation, for bridging purposes and for long-term or permanent implantation.

Assisted Circulation↗
PubMed2005

[Five years experience with non-pulsatile flow].

Mechanical circulatory assistances now belong to the therapeutic stock in case of advanced heart failure. Their mainspring lays on the substitution of the failing left and/or right ventricle function with a pump. The goal being to maintain or restore the system main functions. Their main indication is a bridge to transplant mechanical circulatory assistance, allowing the patient to await transplantation. However, indications for definitive implantation appear in case of transplantation counter indication, mechanical circulatory assistances already emerging as a possible alternative to transplantation. For over 10 years, we have used pulsatile flow assistances, either with pneumatic ventricles or electro-mechanic implantable left ventricles. We henceforth observe the development of a new generation of implantable assistance providing a non-pulsatile flow. These are axial pumps. We evaluated the first model, the DeBakey axial pump which became the most used axial pump worldwide. We now observe the development of other axial pumps as well as the development of new implantable centrifugal pumps.

Assisted Circulation↗
PubMed1989

Temporary mechanical ventricular support: Part 2.

Temporary mechanical circulatory support is currently indicated in postcardiotomy cardiogenic shock and if necessary as a bridge to transplantation where no ventricular recovery is expected. Which mechanical support system to employ as a bridge to transplantation remains debatable. Implantable devices presently used are prototypes of proposed permanent devices for the treatment of severe heart failure in patients for whom transplantation is not suitable or available.

Assisted Circulation↗
PubMed1989

[Clinical study on the effects of assist bypass on left ventricular contractility].

This study was undertaken to evaluate the effects of circulatory support on cardiac function in 7 patients. They were 2 men and 5 women with of age 34-54 years; Six patients underwent mitral valve replacement and one had mitral valve plasty. End-systolic pressure/volume (ESP/ESV) representing left ventricular contractility was measured just before ECC starting and after cardiac beating began in the process of rewarming. Measurements were repeated at every, interval of 10 minutes up to 60 minutes. ESP/ESV (mmHg/ml) [% of that before ECC] were as following; before ECC: 1.69 +/- 0.68 (mean +/- SD) [100], after 10 minutes; 0.40 +/- 0.24 [25.1 +/- 13.8], after 20 minutes; 0.52 +/- 0.26 [31.5 +/- 12.9], after 30 minutes; 0.77 +/- 0.28 [47.6 +/- 10.5], after 40 minutes; 0.97 +/- 0.26 [60.5 +/- 11.3], after 50 minutes; 1.18 +/- 0.46 [70.6]8.0], after 60 minutes; 1.36 +/- 0.56[80.4 +/- 12.7]. It took 39.6 minutes to recover up to 69% of that before ECC. These data suggested that the myocardial ischemia associated with aortic cross clamping continued for at least 60 minutes after cardiac beating resumed. We concluded that assist bypass should be applied to those who could not be weaned from ECC despite adequate use of catecholamine and volume loading.

Adult↗
PubMedDate not supplied

Nonpulsatile ventricular assist bridging to transplantation.

Six patients accepted into a cardiac transplantation program have been supported with a Biomedicus LVAD. Five of the six patients deteriorated while awaiting a donor organ; the sixth was being supported with a device following mitral valve surgery and showed no recovery of ventricular function. In all cases the device was used only after all other therapeutic modalities had failed. The periods of support ranged from 2.5 to 31 days, mean of 10 days. Three patients underwent cardiac transplantation and all three have been discharged and are well. The three survivors were supported for 2.5, 3, and 31 days. Three deaths occurred in the patients supported for 5, 9, and 15 days, the causes being sepsis, massive cerebral embolism, and respiratory failure. Patients were for the most part maintained with some degree of heparinization, and hemolysis was a significant problem in only one patient and associated with a very small arterial return cannula. Flows were routinely maintained above 2.4 L/min/m2, and all showed recovery of other organ functions while being supported. The patient supported for 31 days was capable of limited mobilization by use of the removable drive system. The Biomedicus LVAD represents a relatively inexpensive support modality for patients awaiting cardiac transplantation.

Adult↗
PubMedDate not supplied

Myocardial free fatty acid metabolism of the ischemic heart treated by left ventricular assist device.

Three-beta-methyl-iodophenyl-pentadecanoic acid (BMIPP), a newly developed radiographic probe of metabolic processes in tissue free fatty acid (FFA), was applied to a study analyzing the effect of a left ventricular assist device (LVAD) on impaired dog hearts. The radiographic image obtained with BMIPP was compared with 201thallium chloride (TL) imaging, which indicates tissue perfusion. In the myocardial infarction (MI) model, the BMIPP and TL uptake were equally increased with the use of LVAD in the marginal area of the MI. In another model using the reperfused myocardium after ischemia, the BMIPP and TL uptake were increased in the reperfused area by LVAD pumping. On the other hand, BMIPP uptake in the residual myocardium of both models was decreased by LVAD pumping when compared with TL uptake. This discrepancy between these radiographic tracers in the residual myocardium suggests that tissue metabolic processes may be suppressed as result of a decrease in the energy demand by the myocardium caused by LVAD pumping. The results of this study showed that use of LVADs for the impaired heart improved cell function of "stunned" myocardium and also unloaded the excess work from the residual myocardium as judged by FFA metabolism.

Animals↗
PubMedDate not supplied

A permanent arterial access system.

Now that long-term survival can be achieved in animals with mechanical circulatory devices, reliable permanent arterial access for physiologic and pharmacologic studies has become important. A novel approach has been developed eliminating the need for repeated arterial cannulation. The arterial access system (AAS) consists of a 7 Fr Silastic catheter, which is threaded into the internal mammary artery, and an attached access well, which is placed in the subcutaneous tissue over the sixth rib. The AAS is implanted during the initial operation. The access well is punctured percutaneously with a 23 gauge needle to obtain arterial blood or to measure arterial pressure, and patency is maintained by flushing the access well with 2,000 U of heparin each week. The AAS was implanted in six calves (three with a total artificial heart, three with a ventricular assist device) for a mean duration of 124 days (range, 20-323 days). There were no infections related to the AAS, and none of them thrombosed. All of the AAS had excellent arterial wave forms when punctured. The AAS is simple to implant, provides reliable long-term arterial access, and does not appear to increase the risk of infection.

Animals↗