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PubMedDate not supplied

Predictors for weaning patients from ventricular assist devices.

In order to determine if hemodynamic parameters can accurately predict whether patients can be successfully weaned from ventricular assists devices (VADs), we studied 24 patients supported with Pierce-Donachy VADs (11 left VAD; 6 right VAD; 7 biventricular VAD) following cardiogenic shock for periods from 1.3 to 22 days (mean 5.4). Myocardial recovery was determined by daily measurements of "pump on/pump off" parameters, and the data from seven LVAD patients (64%) and three RVAD patients (50%) whose hearts recovered were compared to the data from those whose did not. Additionally, data from the five patients (71%) weaned from biventricular support were compared to those weaned from only a single LVAD or RVAD. In this study, daily pump on/pump off hemodynamic measurements were found to be predictive of success for weaning patients from VADs. The most significant predictors were increases in mixed venous oxygen saturation, cardiac index, mean arterial pressure and ventricular ejection fraction, as well as decreases in atrial pressures. Seventy percent of the patients weaned from VADs survived, indicating that patients appropriately weaned from VAD support have a reasonable chance of survival.

Assisted Circulation↗
PubMed1987

A technique for apex cannulation without extracorporeal circulation.

A simple, fast, and highly reliable technique for apex cannulation without extracorporeal circulation is presented as a result of more than 30 left ventricle assist device implants performed in calves in the last 4 years at the Cleveland Clinic Foundation. Minimal bleeding and reduced risk of ventricular fibrillation, air emboli, muscle flap, and trauma to the heart have made this technique very unique and highly applicable to any investigative laboratory, as no special tools or expensive apparatus are required. The practicality of the technique is immediately applicable to the clinical level to avoid potential complications with cannula insertion.

Animals↗
PubMed1988

Hot-film wall shear probe measurements inside a ventricular assist device.

Wall shear rates at eleven sites within the Penn State Electric Ventricular Assist Device (EVAD) were determined with the pump operating under conditions of 30 and 50 percent systolic duration and a mean flow rate of 5.8 L/min using a flush-mounted hot-film probe. Probe calibrations were performed with the hot-film in two orientations relative to the flow direction: a standard orientation and an orientation in which the hot-film was rotated by 90 deg from the standard orientation. The magnitude and direction of the wall shear stress at each site within the EVAD were estimated from ensemble averaged voltage data recorded for similar standard and rotated film orientations. The results indicate that, during diastole the wall shear stress direction around the pump's periphery for both operating conditions is predominantly perpendicular to the inflow-outflow plane (in the direction of the pusher plate motion) and reaches a peak value of approximately 350 dynes/cm2. The highest wall shear stresses were found near the prosthetic aortic valve (inside the EVAD) under the 30 percent systolic duration condition and are estimated to be as high as 2700 dynes/cm2. Peak shear stress values of 1400 dynes/cm2 were observed in the vicinity of the prosthetic mitral valve under both operating conditions. The results suggested that the valve regions are substantially more hemolytic than other wall regions of the EVAD; the magnitudes of the wall shear stresses are sensitive to operating conditions; and that wall shear in the direction of pusher plate motion can be significant.

Assisted Circulation↗
PubMed1989

[An experimental study of the construction of a new right ventricle].

This study was undertaken to design and estimate the method to construct a new right ventricle in single ventricle. Twenty five mongrel dogs were used. In this study three types of conduits were used. In Group A vinyl tube, in Group B Woven Dacron tube and in Group C organized Woven Dacron tube were used. Under total cardiopulmonary bypass right atrium was incised. The conduit was inserted through tricuspid annulus and right ventricle into pulmonary trunk. The conduit was fixed at pulmonary trunk and tricuspid annulus. Right ventricle was made closed cavity, and right ventricular pressure affected pulmonary arterial pressure through the conduit wall. In this study right ventricle was regarded as single ventricle. Hemodynamic investigation revealed that central venous pressure must be elevated to get the normal cardiac output. Effective pulse pressure was obtained in the pulmonary artery. Pulmonary vascular resistance decreased as increasing of the pulmonary pulse pressure. Pulmonary pulse pressure was significantly low in group C. It was considered that the intra-ventricular elastic conduit was new method to obtain the pulmonary pulse pressure.

Animals↗
PubMed1988

Surgical aspects of the implantation of a left ventricle assist device.

The authors have summarised their experience with short-term use of a left ventricle assist device (LVAD). Nine experiments were carried out in healthy calves. A polyurethane pump of their own design, placed extracorporeally, was used. Its in-flow cannula was placed in the left atrium, the outflow one in the initial segment of the descending aorta. The LVAD was operated for a period of 5 days. Fourteen days after its disconnection, the animal was sacrificed and both the bypass system and parenchymal organs were examined. No surgical complications were observed during the experiments. Macro- and microscopical pictures showed minor infarctions in the renal tissue which, however, did not impair renal function. The findings in other organs were related to anaesthesia, the operative procedure and way of animal sacrificing. The experiments have proved the safety of the bypass system used over a short period and, consequently, its potential for future clinical application.

Animals↗
PubMedDate not supplied

[Development of a technic and methodology of myoventriculoplasty using programmable cardio-synchronized electro-neurostimulation].

The present work provides the basis for the technique of myoventriculoplastics, first applied in this country, with the use of programmable cardiosynchronized electroneuropacing. The characteristics of a first Soviet implantable electroneuropacemaker, and original electrodes for electrostimulation of the neuromuscular tissue is presented and the surgical technique suggested. Data of 25 experiments on 8 dogs are included. The maximal follow-up period was 7.5 months.

Animals↗
PubMedDate not supplied

Venovenous extracorporeal life support for patients after cardiotomy.

Pulmonary edema and acute lung injury are common sequelae after cardiopulmonary bypass. Increased ventilatory support improves gas exchange, but may compromise ventricular function. From July 1994 to February 1997, nine patients were supported with veno-venous (V-V) extracorporeal life support (ECLS) for post cardiotomy respiratory failure. The mean age was 53 +/- 13 years (range: 37-80 years), and eight (89%) were men. Pre-operatively, five of nine (56%) were intubated, three (33%) were supported with an intra-aortic balloon pump, and five (56%) were on veno-arterial ECLS. Four patients were post left ventricular assist device (LVAD) implantation, one each after resection of an aortic aneurysm, mitral valve replacement and bypass grafting, aortic valve replacement, and pulmonary embolectomy and heart transplantation. Mean duration of support was 2 +/- 1 days (range: 1-4 days). Patients were intubated for a mean of 2 +/- 22 days (range: 4-71 days). One patient (11%) required mediastinal re-exploration secondary to bleeding, two patients underwent hemodialysis or ultrafiltration, and seven (77%) developed bacterial pneumonia. All patients were weaned from ECLS. Six patients (67%) survived to hospital discharge. Cause of death was multiple organ failure in two patients; one died from respiratory failure. V-V ECLS is a useful alternative to open sternotomy for ventilatory induced hemodynamic compromise post cardiotomy, especially in patients with LVADs.

Adult↗
PubMed1993

[Experimental study of ventricular assist device incorporated with a membrane oxygenator].

We designed a new device that incorporated a VAD out let with a membrane oxygenator, and examined the result. In the mock circulation study, a sufficient inlet flow from the membrane oxygenator for oxygenation and removal of carbon dioxide was obtained. Sufficient flow and pressure to maintain systemic circulation were also obtained. In the hypoventilation and heart failure models' study, with this device, hemodynamics were improved and recovered from heart failure. This device was also able to maintain systemic circulation. And the data of blood gas analysis were also improved. These results suggest that this new assisted-circulation system is possibly a superior circulation assist method which has circulatory assist effects and respiratory assistance capabilities. Moreover, we suspect that these findings can be put to use in clinical cases that include heart failure associated with respiratory failure.

Animals↗
PubMed1987

Augmentation of pulmonary blood flow by a right atrial balloon pump after the Fontan operation.

The Fontan principle of right ventricular exclusion is frequently applied to complex congenital lesions. Results are adversely affected by increases in pulmonary vascular resistance and/or ventricular end-diastolic pressure. Survival depends on means to increase pulmonary blood flow. To address this problem, we have developed a triple-balloon catheter that is passed via the femoral vein to the right atrium. Inflation is sequenced so that small balloons located at the junction of each vena cava with the atrium inflate first. Then the larger central balloon inflates, ejecting blood from the right atrium to the pulmonary arteries. The pump is timed to inflate during ventricular systole. In this study, we tested the catheter in vivo in eight dogs. Tricuspid atresia was created and right ventricular exclusion accomplished. Pulmonary blood flow was measured with a flow probe in the right atrium-to-pulmonary artery conduit, at central venous pressures of 15, 20, and 25 mm Hg. Pulmonary blood flow was increased by balloon pumping in every instance (p less than .05). Maximal augmentation of pulmonary blood flow (25.5%) was achieved at a central venous pressure of 15 mm Hg with a balloon ratio of 1:2. Less augmentation was achieved at a central venous pressures of 20 mm Hg (8.4% to 13.0%) and a 25 mm Hg (4.4% to 5.3%) and at balloon ratios of 1:4 and 1:8. We conclude that (1) a triple-balloon pump in the right atrium can significantly augment pulmonary blood flow after right ventricular exclusion and (2) most effective augmentation can be achieved without excessive volume loading. Pulsatile augmentation of pulmonary blood flow with this device should improve survival after Fontan operations.

Animals↗