Biomedical subjects

D R Trumble

Publications and source records attributed to D R Trumble.

22 records · Page 2Linked to original sources

PubMedDate not supplied

Development of an implantable centrifugal blood pump.

The efficacy of centrifugal pumps for short-term (0-30 days) ventricular support has been widely reported and favorably compared with pulsatile systems. A small, durable, implantable centrifugal blood pump is being developed for medium-term use (up to 6 months). The pump is based on the Medtronic Hemadyne system that has existed in multiple forms over the past 30 years. The pump is approximately the size of a tennis ball, weighs 240 g, and is comprised of a 2.5 cm plastic impeller driven by a radially coupled brushless DC motor. In vitro hydraulic performance was recorded over a wide range of flow conditions on a mock circulatory loop. The pump generated 7 L/min flow against an afterload of 100 mmHg pressure, with a maximum power draw of 10.4 watts. Pulsatile flow was preserved when placed in conjunction with a simulated left ventricle. In vivo testing was performed in 10 healthy sheep for 10-292 hr. Heparin was used to facilitate cannulation, and no anticoagulation was administered after pump implantation. Blood chemistries reflecting hematologic, pulmonary, renal, and hepatic functions were recorded and demonstrated no adverse effects with normal pump operation. Complications were related to kinking of blood conduits and thrombus formation within the cannulae. These results are encouraging and warrant further studies to prove feasibility of this pump as a medium-term implantable ventricular assist device.

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PubMedDate not supplied

Perineural leads and burst stimulation optimize contraction of skeletal muscle.

Electrode position and stimulation mode were hypothesized to be independent variables for the contractile response of skeletal muscle. Perineural and intramuscular electrodes were tested with single and burst pulse generators. Voltage requirements and muscle force generation were measured. Perineural leads improved the efficiency of stimulation for muscle contraction and yielded reduced threshold and plateau voltages compared to intramuscular leads. There were no differences between the different types of perineural leads. Burst stimulation had a wider range of voltage for muscle fiber recruitment and was confirmed to elicit greater maximal force than single stimulation.

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PubMedDate not supplied

Chronic counterpulsation with descending thoracic aortomyoplasty improved cardiac function in animals with heart failure.

Descending thoracic aortomyoplasty uses latissimus dorsi muscle for extraaortic diastolic counterpulsation. We hypothesized that descending thoracic aortomyoplasty could improve ventricular function in dogs (n = 5) with heart failure. The left latissimus dorsi muscle was wrapped around the descending aorta and conditioned for 4 weeks with a burst stimulator (five pulses, 33 Hz, 28 bursts/min). Heart failure was induced by rapid ventricular pacing after conditioning. Left ventricular volume was measured with a conductance catheter. Left ventricular and aortic pressures were measured with a micromanometer. Mean diastolic blood pressure, endocardial viability ratio, left ventricular peak pressure, left ventricular end-diastolic pressure, stroke work, isovolumic relaxation time constant, and the end-systolic pressure volume relation were measured at baseline (after heart failure) and with the descending thoracic aortomyoplasty stimulated at 1:1. Contraction of the descending thoracic aortomyoplasty augmented mean diastolic blood pressure (62 +/- 4 to 71 +/- 3 mm Hg) and endocardial viability ratio (1.0 +/- 0.30 to 1.5 +/- 0.13) (p < 0.05). Left ventricular peak pressure (98 +/- 4 to 88 +/- 3 mm Hg), left ventricular end-diastolic pressure (19 +/- 4 to 14 +/- 4 mm Hg), and stroke work (1048 +/- 124 to 743 +/- 80 mm Hg.cm3) (p < 0.05) were reduced. The end-systolic pressure volume relation increased with descending thoracic aortomyoplasty stimulation (3.7 +/- 0.7 to 4.5 +/- 0.8 mm Hg/mL), and the isovolumic diastolic relaxation time constant significantly decreased (54 +/- 6 to 49 +/- 7 msec) (p < 0.05). We conclude that descending thoracic aortomyoplasty can provide diastolic counterpulsation and reduce stroke work in animals with heart failure.(ABSTRACT TRUNCATED AT 250 WORDS)

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PubMedDate not supplied

Static left latissimus dorsi cardiomyoplasty: effect on left ventricular function.

When the latissimus dorsi is used for ventricular augmentation in cardiomyoplasty, a delay of several weeks occurs before the muscle revascularizes, adheres to the heart, and is transformed to fatigue-resistant status. This study analyzes the effect of static (unstimulated) cardiomyoplasty on left ventricular function. Four mongrel dogs underwent staged left latissimus dorsi cardiomyoplasty. Left ventricular pressure was measured with a micromanometer catheter. Left ventricular volume was measured by sonomicrometry. Cardiac output, heart rate, preload recruitable stroke work, maximum elastance, left ventricular end-diastolic volume, left ventricular end-diastolic pressure, stroke work, and the diastolic relaxation constant were measured before and immediately after cardiomyoplasty with the myoplasty static. Results, expressed as mean +/- standard error of the mean, showed no significant differences in indexes of systolic function (stroke work, 1017 +/- 223 gm.cm to 984 +/- 403 gm.cm; preload recruitable stroke work, 110 +/- 13 gm.cm/cm3 to 115 +/- 19.8 gm.cm/cm3; maximum elastance, 10.38 +/- 5.6 mm Hg/ml to 13.59 +/- 6.5 mm Hg/ml; cardiac output 4.51 +/- 0.43 L/min to 4.21 +/- 0.34 L/min) or diastolic function (left ventricular end-diastolic volume, 21 +/- 5.2 ml to 20 +/- 5.3 ml; left ventricular end-diastolic pressure, 13 +/- 3.5 mm Hg to 15 +/- 3 mm Hg; diastolic relaxation constant 42.8 +/- 5.2 msec to 42.5 +/- 4.5 msec). Heart rate also remained unchanged (131 +/- 8.9 beats/min to 140 +/- 9.8 beats/min). The static (unstimulated) left latissimus dorsi cardioplasty can be done with little effect on left ventricular systolic or diastolic function in the normal canine heart.

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