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Biomedical subjects

J S Garrett

Publications and source records attributed to J S Garrett.

13 recordsLinked to original sources
PubMed1992

Hemodynamic effects of dobutamine in an intact animal model.

BACKGROUND AND METHODS: Actions of dobutamine at the beta 1, beta 2, and alpha 1 adrenoreceptors were studied in anesthetized dogs. Six animals received dobutamine (at infusion rates of 0 to 160 micrograms/kg/min) with and without beta-adrenergic receptor blockade. Five animals received phenylephrine (0 to 16 micrograms/kg/min), with and without concurrent dobutamine (20 micrograms/kg/min); this procedure was repeated in five animals after beta-blockade. RESULTS: Dobutamine (10 to 160 micrograms/kg/min) increased heart rate (HR), cardiac output, and left ventricular change in pressure over time, and decreased systemic vascular resistance. beta-blockade prevented only dobutamine-induced changes in HR. Mean arterial pressure (MAP), unaffected by dobutamine alone, decreased with concurrent beta-blockade. Phenylephrine (1 to 16 micrograms/kg/min)-induced increases in MAP were unaffected by dobutamine; with beta-blockade, phenylephrine reduced MAP. Dobutamine prevented a phenylephrine-induced increase in systemic vascular resistance, an effect eliminated by beta-adrenergic receptor blockade. CONCLUSIONS: Dobutamine appeared to be an agonist at the beta 1- and beta 2-adrenoreceptors and at the myocardial alpha-adrenoreceptor. Dobutamine appeared to be an alpha-adrenergic receptor antagonist in the peripheral vasculature.

Adrenergic beta-Antagonists↗
PubMed1991

Efficacy of dopamine and norepinephrine for treatment of hemodynamic compromise in amitriptyline intoxication.

BACKGROUND AND METHODS: Dopamine and norepinephrine were evaluated for treatment of hemodynamic compromise in amitriptyline intoxication. Fifteen anesthetized dogs underwent hemodynamic monitoring and amitriptyline intoxication, and received three infusion rates of dopamine (5, 15, and 30 micrograms/kg.min) and three infusion rates of norepinephrine (0.25, 0.5, and 1.0 micrograms/kg.min), sequentially, with hemodynamic measurements at each dose. Data were analyzed using repeated-measures analysis of variance; p less than .05 was considered significant. RESULTS: Amitriptyline intoxication lowered cardiac output, peak left ventricular dP/dt, and mean arterial pressure (MAP). All doses of norepinephrine and the two higher doses of dopamine increased cardiac output, MAP, and peak left ventricular dP/dt during the intoxicated state. Both agents restored all variables to preintoxication values. Values obtained at the highest doses of the two drugs were not different for any variable. CONCLUSION: Dopamine and norepinephrine each appeared effective in reversing amitriptyline-induced hemodynamic alterations.

Amitriptyline↗
PubMed1987

Verapamil prevents the development of alcoholic dysfunction in hamster myocardium.

Ethanol causes depression of cardiac function. A new model in hamsters was developed for studying ethanol-induced myocardial dysfunction and the effects of verapamil in preventing the functional and metabolic derangements caused by ethanol ingestion were evaluated. Ethanol was added to the drinking water of hamsters in increasing amounts, reaching 50% from 5 weeks on. A control group received plain water only. A third group had verapamil (1.75 mg/cc) added to the ethanol-water mixture to evaluate its potential protective effect. After 5, 7 and 12 weeks, the animals were killed and the hearts perfused using a Langendorff heart preparation. Pressures were recorded and metabolic analysis was performed by the freeze-clamp technique. Compared with control hearts, the hearts from hamsters ingesting ethanol showed significant depression of developed pressure and maximal rate of rise in pressure. There was also significant depression of high energy phosphates and adenosine. The animals drinking the ethanol-verapamil mixture had preservation of left ventricular performance and high energy phosphates, with measurements indistinguishable from those of the control group. In summary, verapamil prevented the development of myocardial depression and preserved normal energy metabolism in hearts of hamsters drinking 50% ethanol.

Animals↗
PubMed1986

Right-sided cardiac transplantation: importance of functional valves.

An original surgical procedure had been developed entailing the implantation of a right-sided heterotrophic cardiac graft in 14 dogs. The benchwork preparation included creation of both atrial and ventricular septal defects which allowed transplantation with the avoidance of extracorporeal circulation and the utilization of all transplanted myocardium and parts. The structure and function of this graft were sequentially evaluated using rapid cine-computed tomograms which permitted assessment of forward graft flow, ventricular wall contraction, and diastolic thickness for both the native and grafted hearts. These parameters were followed during the early (E) (less than 3 days), intermediate (I) (4-21 days), and late (L) (greater than 21 days) postoperative periods. Forward flow (E: 3.0, I: 1.5, L: 2.6) through the transplant was maintained by the competence of the implanted valves despite a progressive decrease in the contraction (E: 3.0, I: 1.3, L: 1.0) and associated decrease in the wall thickness (E: 3.0, I: 2.6, L: 2.4). These findings were consistent with severe cardiac graft rejection without immunosuppression. In summary, long-term structural and functional forward flow of this configurated right-sided transplantation had been maintained by the competent valves on both sides of the graft despite severe rejection without immunosuppression as documented by rapid cine-computed tomograms.

Animals↗
PubMed1985

Measurement of cardiac output by cine computed tomography.

High-speed computed transmission tomography (cine CT) is a new noninvasive technique that may be useful for the rapid, accurate quantitation of cardiac function. The capability of cine CT to assess cardiac output was examined 10 mongrel dogs as an initial step in validating this method. After the dogs were anesthetized, femoral arterial pressure and pulmonary artery thermodilution catheters were inserted. After intravenous injection of a bolus of contrast medium, cine CT scans were performed in the flow mode, in which 50-ms scans were triggered electrocardiographically at end-diastole at 8 levels during sequential cardiac cycles. Scans and thermodilution measurements of cardiac output were obtained at rest and during altered hemodynamic states induced by separate infusions of dobutamine and phenylephrine. Time-density analysis was performed over the left ventricular cavity and curves were fitted to the CT flow data by gamma-variate analysis. Using the Stewart-Hamilton equation established for indicator dilution techniques, the cardiac output was calculated. The results established a direct linear correlation (r = 0.92) between cine CT cardiac output and thermodilution cardiac output over a wide range of cardiac outputs (1.5 to 6.3 liters/min). This study demonstrates that cine CT can provide a reliable estimate of cardiac output noninvasively using contrast medium as an indicator in dogs.

Cardiac Output↗
PubMed1985

Computed axial tomography of the heart.

CT scanning provides useful cardiac imaging but has not become a routine clinical tool for heart disease due to long exposure times (2-5 seconds) and the limitation of single slice acquisition. A revolutionary high speed (Cine) CT electron beam scanner was designed at UCSF, with multilevel millisecond scanning speed at rates of 17 scans per second. Table tilt and swivel permits direct imaging in various planes including the half axis view. Images can be analysed as closed loop movies, and quantitation of wall thickening, wall mass and ejection fractions are being validated. High resolution imaging without the need for gated acquisition is a significant advantage over nuclear medicine and magnetic resonance imaging, and physiology can be studied with exercise of other interventions. Fast CT can measure vessel blood flow and has great potential for estimating myocardial perfusion using indicator dilution theory and small peripheral intravenous injection of contrast medium. Cine CT could become the noninvasive modality of choice in cardiovascular diagnosis - the scanner has universal application for all organ systems.

Cineradiography↗
PubMedDate not supplied

Cine-computed tomography of arrhythmogenic right ventricular dysplasia.

The CT diagnostic features of arrhythmogenic right ventricular dysplasia (Uhl anomaly) are described in a 72-year-old man. High speed cine-CT was performed using millisecond exposures and multilevel scanning. Ventricular morphology and function were evaluated, and findings were compared with two-dimensional echocardiography and equilibrium gated blood pool imaging. Cine-CT showed a dilated hypokinetic right ventricle with a markedly thin anterior wall and normal left sided chambers. The clinical aspects of Uhl anomaly are reviewed.

Aged↗
PubMedDate not supplied

Cine-computed tomography of Ebstein anomaly.

A case of Ebstein anomaly is reported, and the diagnostic potential of cine-CT in assessing the magnitude of the anatomic changes and the presence of right to left intracardiac shunting is evaluated.

Cineradiography↗
PubMedDate not supplied

Quantitation of intracardiac shunts by cine-CT.

Quantitation of intracardiac shunts is important in the evaluation of congenital heart disease and ventricular septal defects postmyocardial infarction. Shunt detection and quantitation is currently performed by either oximetry or radionuclide angiography. Oximetry is an invasive technique and radionuclide angiography, although noninvasive, does not have sufficient spatial resolution to provide detailed anatomic information. The present study evaluated a new technique for quantitating right-to-left shunts by analysis of indicator dilution curves acquired noninvasively using cine-CT. This technique was evaluated in a phantom and in postoperative dogs with a surgically created variable shunt. The phantom model demonstrated the accuracy and reproducibility of the curve analysis algorithm, and the canine model permitted the comparison of oximetry with cine-CT for shunt quantitation. Cine-CT accurately estimated right-to-left shunt fraction when compared with oximetry (r = 0.91) and is more sensitive than oximetry in detecting small shunts. The results of this study suggest that contrast enhanced cine-CT provides a precise noninvasive technique for measuring shunt lesions in congenital and acquired heart diseases.

Animals↗