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PubMedDate not supplied

Bridging to heart transplantation with circulatory support devices.

Several devices are currently available for bridging to cardiac transplantation, but the efficacy of each has not been established. From September 1983 to March 1988 we supported 17 transplant candidates with mechanical assist devices. Extracorporeal membrane oxygenation (ECMO) was used to bridge two patients, external ventricular assist devices (VADs) were used in 11 patients, internal left ventricular assist systems (LVAS) were used in three patients, and implantable prosthetic replacement ventricles (TAH) were used in one patient. The 14 men and three women, aged 24 to 59 years (mean 46 years), suffered cardiogenic shock caused by ischemic (13 patients), postpartum (two patients), viral (one patient), and drug-induced (one patient) cardiomyopathy. Five patients with isolated left ventricular failure (LVF) received only left VADs, three patients with severe LVF and moderate right ventricular failure received LVAS, and nine patients with severe biventricular failure received ECMO (two patients), biventricular assist devices (six patients), and TAH (one patient). Patients were supported for periods of 1/2 to 90 days (mean 22) with flows of 2.15 to 3.39 L/min/m2. Ten patients underwent transplantation (eight of whom were discharged) and seven patients died without transplants. The two patients who received ECMO died 1 and 30 days after transplantation, in part as a result of ECMO complications. Seven patients were denied transplants because of renal failure (five patients), infection (five patients), bleeding (four patients), and cerebrovascular accident (two patients). The seven survivors were supported with VADs (five patients) or LVAS (two patients). Three had driveline infections, two had bleeding complications, two developed mediastinitis, and one each had hemolysis, cerebrovascular accident, and mechanical failure.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Left ventricular assistance in dogs using a skeletal muscle powered device for diastolic augmentation.

A pulse train stimulator was developed for skeletal muscle stimulation synchronous to the myocardium. Left ventricle contraction was augmented by a stimulated rectus abdominis muscle pedicle grafted into the left ventricular wall. A miniaturized and programmable stimulator was built. The stimulation parameters for this device were optimized and the configuration of a skeletal muscle powered assist device for cardiac assistance was investigated in acute canine experiments. A hydraulic balloon preparation was used to characterize stimulation parameters and to compare rectus abdominis, latissimus dorsi and pectoralis major muscles as power sources. Assist devices evaluated included a left ventricle apico-aortic conduit with a central pumping chamber and an extra-aortic balloon pump. The pumping chambers were either wrapped by the rectus abdominis and latissimus dorsi pedicles, or placed deep into the pectoralis major. The optimal stimulation parameters were pulse trains of 200 msec duration containing pulses 240 mu wide at a frequency of 35 pulses/second. There was no fatigue over a ten hour period despite stimulation at a rate of 120 contractions/minute. Muscle dissection and selection were determinants of fatigability. However, counter-pulsation was possible regardless of the muscle selected. The most efficient device was an extra-aortic balloon pump. There was a consistent increase in subendocardial viability index (DPTI/TTI). The advantages in using a skeletal muscle power source for diastolic rather than systolic assistance were established.

Abdominal Muscles↗
PubMed1988

Seven years' experience with the Pierce-Donachy ventricular assist device.

Of currently available methods for mechanical circulatory support, the Pierce-Donachy external pneumatic ventricular assist device has proved to be one of the most versatile and effective. Since 1981, 48 patients, aged 15 to 71 years (mean 43.0), with profound cardiogenic shock refractory to conventional therapy with drugs and intra-aortic balloon support, were supported with the Pierce-Donachy ventricular assist device. There were four patient groups. The largest group consisted of 30 patients with cardiogenic shock after cardiac operations. Nine required left ventricular support, six needed right ventricular support plus an intraaortic balloon pump, and 15 had biventricular support. Duration of support ranged from 3 hours to 22 days (mean 3.6 days). Eight of the first 11 patients died in the operating room of bleeding and/or biventricular failure. However, 16 patients, (53%) had improved cardiac function, 15 (50%) were weaned, and 11 (36%) were discharged. Of the last 19 patients, 47% survived. Frequent factors in nonsurvivors were myocardial infarction (75%) and renal failure (90%). Common complications in all patients were bleeding (52%) and infection (27%). The second group consisted of 11 patients with end-stage cardiomyopathy or acute myocardial infarction in whom the Pierce-Donachy ventricular assist device was used as a bridge to transplantation (left ventricular support, four patients; biventricular support, seven patients). Renal failure, infection, or coagulopathy that precluded transplantation developed in five patients. Five patients were supported for 8 hours to 75 days (mean 20.7 days) before undergoing successful transplantation, with one late death (six months) from rejection owing to noncompliance. One has subsequently undergone successful transplantation after 84 days of support. The third group consisted of four patients, aged 40 to 56 years (means 47.2), who had refractory cardiogenic shock after cardiac transplantation caused by pulmonary hypertension (two patients), hyperacute rejection (one patient), or graft failure (one patient). Despite biventricular support in all four (biventricular assist devices, two patients; right ventricular assist device plus intraaortic balloon pump, two patients), all died of infection and/or renal failure after 12 hours to 6 days (mean 3.4 days) of support. The final group consisted of three patients, aged 36 to 51 years (mean 45), with cardiogenic shock caused by acute myocardial infarction. One patient was supported with biventricular assist devices (3.5 days) and two patients were supported with a left ventricular assist device (8.5 and 15 days).(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1988

Heat dissipation through the blood contacting surface of a thermally driven LVAS.

A heat exchanger for a totally implantable heat driven LVAD is an essential element in overall system thermal management. The heat exchange is accomplished by supplying cooling water from a pusher-plate driven water pump to the engine and then to the heat exchanger on the pump housing. The temperature of the interface between the blood and pump surface is of critical importance for clinically acceptable operation of the system. Temperatures were measured by instrumenting a pump housing with thermocouples and an electric heater on a mock circulatory loop. Flows were varied from 1 to 8 l/min and heat input was 20 watts. At 1.0 l/min pump flow the maximum inner surface temperature rise is 4.5 degrees C. In vitro tests were conducted to examine the effect of elevated temperature on platelete function. Both platelet aggregation and adhesion were reduced at elevated temperatures of 42 and 47 degrees C indicating a potential benefit of reduced thrombogenesis on the heated housing surface.

Assisted Circulation↗
PubMedDate not supplied

Antithrombogenicity of ventricular assist devices for postoperative myocardial dysfunction.

Antithrombogenicity of pneumatic ventricular assist devices (VAD) for postoperative ventricular failure was evaluated macroscopically and microscopically in relation to VAD flow, coagulation parameters, and other potentially thrombogenic factors. A total of 12 sack type pumps were used in nine cases after operations for ischemic heart diseases (4 cases), valvular diseases (3 cases), and congenital anomalies (2 cases). Durations of pumping of each device ranged from 18 hours to 37 days (mean, 10.9 days). The clinical protocol for antithrombogenicity of the device indicates maintenance of ACT around 150 sec and keeping VAD flow more than 2.0 L/min. In our clinical series, however, heparin was given only in most cases to maintain activated clotting times (ACT) at 120-140 sec for the first three postoperative days. Minute ringlike thrombi were noted at connectors of cannula in two pumps after low flow (1.5 L/min) pumping for 5 days or after frequent on/off studies for weaning. A small thrombus (2 X 2 mm) and fine granular thrombi were noted on actuating bladders in two pumps that were used with frequent on/off studies or in a patient with severe sepsis during VAD pumping. Other VAD pumps were macroscopically free of thrombus. SEM analyses on surfaces of actuating bladders demonstrated mild to moderate platelet adhesions, which were correlated with platelet count, but not with other coagulation parameters including platelet agglutination and pumping duration. In cases with leucocytosis during VAD uses, leucocyte adhesion was noted as well without correlation to the coagulation parameters.

Adolescent↗
PubMedDate not supplied

Chronic effect of left ventricular assist pumping on right ventricular function.

We evaluated right ventricular (RV) function during left ventricular assist device (LVAD) pumping during acute and chronic experiments in both normal hearts and hearts with left ventricular failure. An LVAD was implanted between the left atrium and the descending aorta of goats. The LVAD was pumped in a counterpulsation mode and at maximum bypass flow for 4-6 weeks in chronic experiments. The following results were obtained: 1) LVAD pumping itself did not affect RV function, even after 6 weeks of pumping, 2) the dimensions of the RV free-wall segments measured by sonomicrometers showed a gradual and small increase during the early postoperative days, which was due to an increase in volume returned to the RV and the deformity of the RV cavity derived from reduction in LV volume, and 3) the same tendencies were seen even with LV failure hearts. These results suggested that 1) LVADs can assist not only the LV but also the RV by reducing RV afterload, 2) excessive and prolonged assistance by an LVAD seems to dilate the RV free-wall, and 3) preexisting RV dysfunction is the main cause of signs of RV failure during LV pumping.

Animals↗
PubMedDate not supplied

[Analysis of control systems for artificial circulation devices].

A variant of a complex approach to solving the problem of ensuring the optimal perfusion, based on the separation of the ECA-organism system parameters into 4 subsystems, is proposed. An automatic control of the entire set of the extracorporeal circulation parameters is accomplished in the hierarchial order, with due consideration for the necessity to provide a fast response and physiological significance for the organism of the characteristics and factors subject to correction. The criteria for the adequacy of the extracorporeal circulation should be brought into a dynamic relation to the actual state of the organism. The composition of the blocks making up the system of the extracorporeal circulation regulation is discussed.

Assisted Circulation↗
PubMedDate not supplied

Methods of cardiopulmonary support: a review for radiologists.

Physicians are generally aware of the use of bypass pumps during open heart surgery and of the intraaortic balloon pump in treatment of cardiogenic shock. In selected research centers, other advanced methods of cardiopulmonary support are being introduced. Some devices such as the total artificial heart fail clinical trials and disappear from use. Others, like some of the partial artificial hearts, improve outcomes and gain wider clinical use. Some devices temporarily support the circulation in patients recovering from acute circulatory collapse, whereas others provide longer-term circulatory support for patients awaiting transplantation. Permanently implanted devices provide circulatory assistance in cases of chronic, debilitating heart failure. Technology to support lung function in the setting of acute respiratory failure, allowing healing to take place, is also under study. Radiologists should be familiar with the operating principles and radiographic appearances of these emerging techniques to maintain their role as consultants to cardiopulmonary specialists.

Assisted Circulation↗
PubMedDate not supplied

[Generation of a pulsatile flow in the arterial blood line of an artificial circulation apparatus].

A new type of a ventricle pump incorporated in an arterial blood line of the artificial circulation device has been designed. A poor pulsatile flow generated by the artificial circulation system is transformed by the pump into one characterized by marked fluctuations. It may be synchronized with heart cycle phases, if necessary. Basic principles of the method as well as the circuit of the device and its arrangement within the artificial circulation system are considered.

Arteries↗
PubMed1989

Use of the Pierce-Donachy ventricular assist device in patients with cardiogenic shock after cardiac operations.

In spite of recent improvements in cardiac surgery, a small percentage of patients have severe postcardiotomy ventricular failure refractory to drugs and the intraaortic balloon. In our experience, the Pierce-Donachy external pneumatic ventricular assist device has proved to be one of the most effective devices for these patients. Since 1981, 30 patients aged 15 to 71 years (mean age, 52 years) with profound cardiogenic shock refractory to conventional therapy after cardiotomy were supported with the Pierce-Donachy ventricular assist device. Fourteen required left ventricular support, 7 needed right ventricular support with an intraaortic balloon, and 9 had biventricular assistance. Duration of support ranged from three hours to 22 days (mean length, 3.6 days). Seven of the first 11 patients seen died in the operating room of bleeding, biventricular failure, or both. However, 16 patients (53%) had improved cardiac function, 15 (50%) were weaned, and 11 (37%) were discharged. Of the last 19 patients in the series, 47% survived. Factors affecting survival were myocardial infarction (75%) and renal failure (90%). Common complications were bleeding (73%) and biventricular failure (83%).

Adolescent↗
PubMed1993

Circulatory support in infants and children.

Although the last decade has brought dramatic improvement in patient selection and postoperative management of adults and children undergoing advanced mechanical circulatory support, technological advances have been largely limited to the adult population. Intraaortic balloon pumps are technically feasible, but their efficacy has been questioned and their use has been limited in children. Over the last decade, extracorporeal membrane oxygenation has become the most commonly used method of mechanical circulatory support in children who have severe cardiac failure after cardiac operations. Additionally, a small number of infants and children have been supported with extracorporeal membrane oxygenation as a bridge to cardiac transplantation or as temporary support during reversible myocardial failure due to lesions such as viral myocarditis. More recently, a small number of pediatric patients have been supported with centrifugal and pneumatic devices, particularly after cardiac operations. Surprisingly, many of these patients did well with left ventricular support only. The overall children's survival rates in the myocardial recovery group are better than those in adults. However, current pediatric devices do not provide support for greater than a few weeks, making bridging to transplantation less feasible than in adults.

Assisted Circulation↗