PubMed Health⌕ Search

Biomedical subjects

J G Carr

Publications and source records attributed to J G Carr.

At least 19 recordsLinked to original sources
PubMed1991

Hemodynamic evaluation of a chronically implanted, electrically powered left ventricular assist system: responses to acute circulatory stress.

Hemodynamic stress testing was performed in four calves with a chronically implanted left ventricular assist device consisting of a double-valved pump interposed between the left ventricular apex and the descending thoracic aorta. The device was powered either pneumatically (n = 1) or with a transcutaneous energy transmission system (n = 3). Hemodynamic evaluation (cardiac output and right and left ventricular and pulmonary and carotid artery pressures) was carried out at baseline and during all hemodynamically stressed states. Atrial pacing and ventricular pacing to a heart rate of 140 beats/min resulted in no significant change in right or left heart filling pressures or cardiac output. Preload reduction with nitroprusside or transient inferior vena cava balloon occlusion resulted in a marked decrease in left ventricular pressure with preservation of mean arterial pressure. Phenylephrine administration resulted in a marked rise in mean arterial pressure with no change in cardiac output or filling pressure. Induction of ventricular fibrillation resulted in a decrease of mean left ventricular pressure to 11 +/- 8 mm Hg, but mean arterial pressure was maintained at greater than or equal to 50 mm Hg. It is concluded that a multicomponent, implantable, electrically powered assist system is capable of maintaining a normal cardiac output under a wide range of loading conditions and chronotropic states. Although this device is clearly preload dependent, it is capable of maintaining normal systemic pressures during conditions of severe left ventricular dysfunction and circulatory collapse.

Animals↗
PubMed1989

Prevalence and hemodynamic correlates of malnutrition in severe congestive heart failure secondary to ischemic or idiopathic dilated cardiomyopathy.

Whereas cardiac cachexia is well recognized, the frequency and hemodynamic correlates of malnutrition in severe congestive heart failure (CHF) have not been established. Anthropometric and serum albumin assessment of nutritional status was compared with hemodynamic, echocardiographic and serum chemistry evaluation in 48 patients with severe CHF (ejection fraction 0.17 +/- 0.05). Malnutrition, as defined by decreases in percent body fat determined from skinfold thicknesses, weight/height index or serum albumin, was present in 24 of 48 (50%) patients, who did not differ from the 24 well-nourished patients in cardiac index (1.9 +/- 0.6 vs 2.1 +/- 0.6 liters/min/m2) and pulmonary artery wedge pressure (30 +/- 6 vs 27 +/- 10 mm Hg), but had higher right atrial pressure (16 +/- 5 vs 9 +/- 6 mm Hg, p less than 0.01) and more severe tricuspid regurgitation by semiquantitative Doppler grading on a 0 to 3 scale (2.0 +/- 0.9 vs 0.9 +/- 0.8, p less than 0.01). Right atrial pressure was the only independent hemodynamic predictor of malnutrition (p less than 0.0002). Malnourished patients had lower serum sodium (134 +/- 4 vs 139 +/- 4 mEq/liter, p less than 0.01) and total triiodothyronine levels (89 +/- 30 vs 115 +/- 26 ng/dl, p less than 0.01) and higher creatinine levels (1.6 +/- 0.7 vs 1.2 +/- 0.4, p less than 0.03). None of the other biochemical markers of nutritional status differed between the groups except lower serum triglyceride levels (115 +/- 73 vs 186 +/- 97 mg/dl, p less than 0.05) in malnourished patients. Malnutrition is common in patients with severe CHF and is associated with increased right atrial pressure and tricuspid regurgitation.

Body Weight↗
PubMed1979

Temporary left ventricular bypass: factors affecting patient survival.

Circulatory support (range, 2 hours-8 days) was undertaken in eight cardiac surgical patients (with two survivors) exhibiting intractable cardiogenic shock. A paracorporeal, pneumatic, xenograft-valve pump was interposed between the left ventricular apex and ascending aorta. Pumping lowered left atrial and ventricular pressure while maintaining cardiac output (1.8--2.6 l/min/m2). Following implantation, plasma hemoglobin and erythrocyte mechanical fragility values were elevated but decreased to normal when renal function was not impaired. Mild thrombocytopenia was noted in three patients and was severe in five others with persistent hemorrhage. Anticoagulation agents were used during tapering of pump flow (three patients) after 100, 105 and 120 hours of bypass. Otherwise, for the major portion of the interval of mechanical circulatory support, anticoagulants were not administered. Despite this fact, no systemic embolization was detected in any of the patients. It appears that assist pump support can be life-saving in acute left ventricular failure in patients following cardiac surgery.

Adult↗
PubMed1975

A new method for temporary left ventricular bypass. Preclinical appraisal.

Surgical patients who cannot be weaned from cardiopulmonary bypass during operation or who develop balloon-dependent left ventricular failure postoperatively are now considered unsavable. However, in those with potentially reversible ventricular dysfunction, recovery might be possible if an improved means of temporary circulatory support were available. Towards this end, a pneumatically actuated, left ventricular assist pump was developed and evaluated in 20 consecutive calf experiments. The device, containing a flexible polyurethane pumping chamber, was positioned on the chest wall and connected to the left ventricular apex and descending thoracic aorta by two Dacron valved conduits (xenograft valves). All animals survived a 14 to 30 day pumping interval, and 7 underwent successful removal of the device by division of the Dacron conduits below skin level. As a prelude to human investigation, pumps were implanted during a series of routine autopsies through midline sternotomy incison. The device was positioned on the right anterolateral chest wall, with two valved conduits traversing the mediastinum to connect the pump to the left ventricular apex and ascending aorta.

Animals↗