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Biomedical subjects

R R Fripp

Publications and source records attributed to R R Fripp.

35 records · Page 2Linked to original sources
PubMed1984

Pulsed Doppler and two-dimensional echocardiographic findings in aortico-left ventricular tunnel.

Two-dimensional echocardiography was used to make the anatomic diagnosis of aortico-left ventricular tunnel in a 1 day old infant. Pulsed Doppler echocardiography allowed directional flow to be determined within the tunnel. The findings were confirmed by cardiac catheterization and by direct visualization at the time of surgical repair. Aortic valve insufficiency was excluded before and after surgery using pulsed Doppler echocardiography. The anatomy and physiology of aortico-left ventricular tunnel can thus be documented using noninvasive techniques.

Aorta↗
PubMed1983

Evaluation of the pediatric surgical patient with congenital heart disease.

Children with cardiac disease who undergo noncardiac surgical procedures may encounter risks beyond those usually associated with surgical procedures. In this article, several complicating factors seen in children with heart disease are discussed, including arrhythmias, cyanosis, congestive heart failure, pulmonary hypertension, and subacute bacterial endocarditis.

Adult↗
PubMed1983

Fatty acid and glucose utilization in isolated, working newborn pig hearts.

The effects of exogenous fatty acids on glucose uptake were assessed in isolated, working newborn pig hearts in which great vessel pressures were controlled (mean 55 mmHg) and oxygenated nutrient buffer was recirculated through the heart for 30 or 60 min. When palmitate (1.5 mM) or octanoate (1.0 mM) were added to buffer containing 10 mM glucose and 100 mU insulin/ml, glucose uptake, as measured by 3H2O production from D-[2-3H]glucose, was suppressed to less than one-half that observed when glucose alone was present. Increased tissue levels of glucose 6-phosphate, fructose 6-phosphate, and citrate following perfusion in the presence of exogenous fatty acids were consistent with decreased glycolytic activity due to inhibition of phosphofructokinase. Measurements of carnitine in perfused and unperfused hearts indicated that total carnitine levels in neonatal hearts are similar to those of adult pigs. Increased tissue levels of long-chain acyl carnitine, acetyl carnitine, and citrate in hearts perfused with palmitate and glucose in combination with extensive fatty acid uptake and marked suppression of glycolysis indicated that the newborn pig heart is capable of utilizing fatty acids as a primary energy source.

Animals↗
PubMed1983

Fatty acid and glucose utilization in isolated, working fetal pig hearts.

Fatty acid uptake and the effects of long- and short-chain fatty acids on glucose utilization were assessed in isolated perfused fetal pig hearts (0.9 gestation) in which oxygenated nutrient buffer was pumped from both ventricles at controlled pressure (55 mmHg, mean arterial pressure) and heart rate (180 beats/min). When either 1.5 mM palmitate or 1.0 mM octanoate was added to buffer containing 10 mM glucose and insulin (100 microU/ml), glucose uptake, as measured by 3H2O production from D-[2-3H]glucose, was suppressed when compared with glucose uptake in the absence of fatty acid. Increased tissue concentrations of glucose 6-phosphate, fructose 6-phosphate, and citrate in hearts perfused with buffer containing octanoate indicated active beta-oxidation and inhibition of phosphofructokinase activity when compared with hearts perfused with glucose alone. In contrast, hearts perfused with buffer containing palmitate showed no increases in these metabolic intermediates. These results suggest that suppression of glucose uptake in the presence of long-chain fatty acid was not the result of phosphofructokinase inhibition but may result from inhibition of glucose transport by palmitate. Determinations of tissue concentrations of free carnitine and carnitine derivatives indicated that, although palmitate underwent esterification to long-chain acyl carnitine in the fetal heart, it failed to undergo extensive beta-oxidation.

Animals↗
PubMed1983

Enhanced sensitivity of diabetic hearts to alpha-adrenoceptor stimulation.

Inotropic responses to alpha-adrenergic stimulation with methoxamine were compared in 12 normal (N) and 12 diabetic (Db) lambs. Diabetes was produced by giving alloxan monohydrate (150 mg/kg iv). Measurements of maximal rate of rise of left ventricular pressure (dP/dtmax), left ventricular end-diastolic pressure (LVEDP), coronary flow, and myocardial O2 consumption were made simultaneously in hemodynamically controlled preparations. All animals were subjected to ganglionic blockade (tetraethylammonium chloride, 100 mg) and beta1-adrenergic blockade (practolol, 4 mg/kg). Methoxamine was given in incremental doses ranging from 0.4 to 6.0 mg/kg. dP/dtmax increased progressively to 126 +/- 4% of initial values in N. However, the increase was twice as large (150 +/- 4%) in the diabetics (P less than 0.005). LVEDP fell in both groups. These changes were abolished by phentolamine (2 mg/kg). Inotropic responses to methoxamine in lambs 2 and 3 wk after induction of diabetes did not differ from those with acute (2 days) diabetes. Dose-response curves obtained by infusing Ca2+ (2-8 mg X min-1 X kg-1) were identical in N and Db. It is concluded that lamb myocardium possesses an alpha-adrenergic receptor system that is stimulated by methoxamine in a dose-dependent manner and blocked by phentolamine. Db hearts are supersensitive to alpha-receptor activation. The mechanistic basis for this latter finding has not been examined but may relate to altered receptor density or nucleotide regulation.

Animals↗
PubMed1983

Blood pressure response to exercise in children following the subclavian flap procedure for coarctation of the aorta.

Eight patients who underwent repair of coarctation of the aorta as infants (mean age 4.6 months) by the subclavian flap procedure were evaluated by dynamic exercise. Their mean age at the time of exercise testing was 4.6 years. Resting upper to lower limb systolic blood pressure gradients were similar in the patients and control subjects (mean 17 +/- 12 and 2 +/- 14 mm Hg) (p greater than 0.05). Mean resting systolic blood pressures in the upper limb were 121 +/- 10 mm Hg in the patients and 107 +/- 14 mm Hg in the volunteers (p greater than 0.05). The mean gradient between the upper and lower limbs was 13 +/- 19 mm Hg in the patients on dynamic exercise testing. No patient became pathologically hypertensive in the upper limbs during dynamic exercise. These results indicate that the subclavian flap procedure is an effective form of treatment for the symptomatic infant with coarctation of the aorta and can be expected to result in a low incidence of subclinical residual obstruction or restenosis.

Aortic Coarctation↗
PubMed1982

Myocardial responses to alpha-adrenoceptor stimulation with methoxamine hydrochloride in lambs.

This study was undertaken to evaluate the effects of methoxamine on left ventricular performance, coronary blood flow (CBF), and myocardial oxygen consumption (MVO2) in lambs. Measurement of maximum rate of rise of left ventricular pressure (LV dP/dtmax), left ventricular end-diastolic pressure (LVEDP), CBF, and MVO2 were made in nine lambs using a hemodynamically controlled preparation. The lambs were given atropine sulfate (1 mg), tetraethylammonium chloride (100 mg), and practolol (4 mg/kg) to provide parasympathetic, ganglionic, and beta-adrenergic blockades. Aortic pressure and blood flow and heart rate were held constant in each lamb. Dose-related increases in LV dP/dtmax and decreases in LVEDP were observed after progressively larger doses of methoxamine ranging from 0.4 to 6.0 mg/kg were given. These positive inotropic responses were eliminated by giving phentolamine (2 mg/kg). CBF, myocardial O2 extraction, and MVO2 did not change significantly. A positive inotropic action of methoxamine was also demonstrated in five additional animals by obtaining ventricular function curves. Initially the mean stroke volume at LVEDP 10 cmH2O (SV10) was 4.11 +/- 0.16 (SE) ml. This value increased to 5.09 +/- 0.28 ml after methoxamine (P less than 0.01). After phentolamine, SV 10 fell to 4.37 +/- 0.08 ml (P less than 0.05). These observations support the hypothesis that alpha-adrenergic receptors are present and mediate a substantial positive inotropic action on neonatal lamb myocardium.

Animals↗
PubMed1981

Inotropic responsiveness of the heart in catecholamine cardiomyopathy.

Inotropic responsiveness to norepinephrine (NE) or Ca2+ was studied in 15 rabbits with catecholamine cardiomyopathy (CM) and the results were compared with 11 controls. The former group was prepared by infusing NE (2 micrograms/min/kg) for 90 minutes, 2 to 3 days prior to study, and injury was confirmed and quantified histologically. Comparison of NE dose-response curves relating percent increase of left ventricular (LV) dP/dt max to NE dose in six controls and 10 CM hearts revealed significant depression of CM contractility. Responses to graded infusions of Ca2+ were also determined in five controls and in five CM animals. With the increases in serum Ca2+ identical in the two groups, the percent increases in dP/dt max were less in CM hearts. Further, NE dose-response curves obtained during continuous CaCl2 infusion were sharply attenuated in CM hearts and initial LV end-diastolic pressure (LVEDP) in the CM hearts was considerably higher than in the controls. It is concluded that inotropic sensitivity to NE is reduced in CM hearts. This cannot be ascribed to altered beta-receptors alone, because responsiveness to Ca2+ was also reduced. Myocardial damage was indicated by histology and elevated LVEDP. Moreover, the normalized percent data suggest tht the remaining viable fibers in the CM hearts were functioning subnormally and thus reduced performance was not due solely to the decreased number of contracting units.

Animals↗
PubMed1981

Oral hydralazine in patients with pulmonary vascular disease secondary to congenital heart disease.

Two patients with pulmonary vascular obstructive disease secondary to congenital heart disease were evaluated hemodynamically before and during oral hydralazine therapy. Both patients were assessed postoperatively and had no significant residual shunts. Pulmonary vascular resistance failed to decrease, and an increase in pulmonary arterial pressure occurred because of increased cardiac output secondary to systemic arteriolar dilatation. These responses were sufficiently consistent to warrant a warning against the use of oral hydralazine except under controlled conditions in patients with secondary pulmonary vascular obstructive disease.

Administration, Oral↗
PubMed1981

Carbohydrate metabolism in isolated, working newborn pig heart.

Metabolic activity of the newborn pig heart was observed by means of a preparation that allowed isolated hearts to perform a physiologic work load. A 10-min period of retrograde aortic perfusion was followed by 60 min of recirculating perfusion in which bicarbonate buffer was infused into the right atrium and ejected from both ventricles at measured pressures and flow rates. The buffer was supplemented with either glucose (10 mM), lactate (20 mM), or pyruvate (20 mM), or was unsupplemented. Pressure development and ventricular outputs were stable through 60 min of perfusion with glucose, pyruvate, or lactate supplementation. Myocardial high-energy phosphate and glycogen contents were also stable. In hearts perfused without substrate supplementation, mechanical performance deteriorated after 30 min. Rates of substrate uptake and oxygen consumption indicated that either glucose, lactate, or pyruvate could serve as a primary source of metabolic energy. Minimal lactate production was observed when either glucose or pyruvate were present. These findings indicate that, despite recent emergence from the relatively hypoxic intrauterine environment, the well-oxygenated newborn pig heart did not depend on anaerobic metabolism of glucose for energy production at physiologic work loads.

Adenosine Triphosphate↗
PubMed1981

Effect of physical training on exercise performance of children following surgical repair of congenital heart disease.

The effect of physical training on the exercise performance of 26 patients following surgical repair of tetralogy of Fallot (16 patients) and ventricular septal defect (ten patients) was evaluated. Base line exercise testing was performed on a bicycle ergometer using the technique of Godfrey. Patients were placed on a six-week alternate day submaximal interval home exercise program of varying duration and intensity. Work loads at 50%, 60%, and 70% maximum oxygen consumption were selected to maintain heart rates between 130 and 160 beats per minute. Subjects completed an average of 18 of the possible 21 training sessions (range 11 to 21). A 25% improvement (p less than .001) was noted in maximum work capacity (747 to 935 km). Sixty-five percent of the patients performed at less than expected maximum work capacity prior to training, but only 31% performed at less than expected maximum work capacity after training. Repeat testing at work loads of one-third, one-half, and two-thirds the original maximum work capacity revealed improved aerobic efficiency as manifested by significantly decreased oxygen consumption and heart rate at each level of work. No significant difference was noted in maximum oxygen consumption. It is concluded that physical training can improve the exercise performance of patients after surgical repair, permitting the individuals to function at levels of activity at, or closely approaching, normal.

Adolescent↗
PubMed1977

Intussusception in haemophilia: a case report.

A case of intussusception in a haemophilic boy is described. The presumed cause was an intramural haematoma, which resulted in an ileocolic intussuception. This appears to be the first reported case which has been reduced by barium enema. It is suggested that this method, together with factor VIII replacement therapy as soon as possible after the development of symptoms, is the treatment of choice.

Adolescent↗