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Biomedical subjects

R J Boucek

Publications and source records attributed to R J Boucek.

At least 55 records · Page 3Linked to original sources
PubMed1985

Beneficial effects of perfluorochemical artificial blood on cardiac function following coronary occlusion.

This study compares the effects of perfluorochemical artificial blood versus whole blood on the systolic and diastolic function of regionally ischemic myocardial preparations. Regional ischemia was produced by ligation of the circumflex coronary artery in isolated, blood-perfused rabbit hearts. Three minutes after occlusion, half the hearts were switched from the blood perfusate to perfluorochemical artificial blood; the other half continued to be perfused with blood. Isovolumic left ventricular (LV) developed pressure, dP/dt and resting pressure were monitored before, and for 2 hours after coronary occlusion. After 90 minutes of regional ischemia, perfluorochemical-treated hearts exhibited significantly greater developed pressure than those perfused with blood (78 +/- 6% versus 61 +/- 5% of preligation values; P less than 0.05). At the end of the experiment, LV dP/dt was 21% greater in the perfluorochemical-perfused group than in the blood-perfused group (74 +/- 8% versus 53 +/- 10%; P less than 0.01). Perfluorochemical perfusion also preserved diastolic function by preventing the 58% increase in left ventricular chamber stiffness (i.e., resting pressure; P less than 0.01) associated with circumflex ligation. Thus, in the present model of regional ischemia, perfluorochemical artificial blood is significantly better than blood at maintaining both systolic and diastolic myocardial function after a major coronary artery has been occluded.

Animals↗
PubMed1985

Operative repair of coarctation of the aorta in infancy: results with and without ventricular septal defect.

Coarctation of the aorta (CA) presenting in infancy is a life-threatening condition, especially if associated with intracardiac left-to-right shunts. Between 1971 and 1980, 51 infants with symptomatic CA have been diagnosed and treated. Ventricular septal defect (VSD) was present in 18 patients and patent ductus arteriosus in 24. End-to-end repair was performed in 20 patients, 17 (85%) of whom were long-term survivors. Subclavian flap angioplasty repair was used in 28 patients, of whom 25 (89%) were long-term survivors. During long-term follow-up 6 patients (35%) who underwent end-to-end repair had recurrent CA, whereas only 3 patients (12%) who underwent subclavian flap angioplasty had recurrent CA (p less than 0.05). The mortality rate in patients with associated VSD was higher (4 of 18, 22%). Pulmonary trunk banding with subsequent VSD repair was associated with a better survival (13 of 14 patients, 90%) than when banding was not performed (2 of 5 patients) (p less than 0.05). These results suggest subclavian flap angioplasty is the preferred treatment for symptomatic CA occurring in infancy. Concomitant pulmonary trunk banding in patients with VSD can be performed with the expectation of a lower mortality at subsequent VSD repair.

Aortic Coarctation↗
PubMed1985

Exercise radionuclide ventriculography in children: normal values for exercise variables and right and left ventricular function.

Thirty two children (aged 5-19 years) with no clinical evidence of significant cardiovascular disease undertook continuous staged supine exercise on a bicycle ergometer. Multigated radionuclide ventriculography was performed at rest and during each exercise stage. Exercise duration and total workload both increased with age. Aerobic work correlated better with age than did total work. In most children the ejection fraction for both ventricles increased by at least 5% with exercise. Right ventricular ejection fraction did not decrease with exercise in any subject but left ventricular ejection fraction decreased by 2% and 9% in two. The response of end diastolic volume to exercise was variable, but there was a consistent decrease in mean (SD) end systolic volume of the left (29(22)%) and right (30(19)%) ventricles. Cardiac index (mean (SD)) increased by 234(65)% with exercise. The left ventricular:right ventricular end diastolic volume ratio (mean (SD)) at rest was 1.26(0.26). It is concluded that exercise radionuclide ventriculography is an excellent technique for a combined assessment of exercise capacity and an evaluation of ventricular size and performance in children. These values for supine bicycle exercise in children without significant cardiovascular disease will be useful for future comparisons with other groups.

Adolescent↗
PubMed1985

Pathophysiology of chronic cyanosis in a canine model. Functional and metabolic response to global ischemia.

To investigate the pathophysiology of chronic cyanosis, we subjected 14 adult mongrel dogs to diversion of the inferior vena cava to the right inferior pulmonary vein. This produced a mean oxygen tension of 42 +/- 2 mm Hg and a calculated right-to-left shunt of 52.0% +/- 3.9%. These animals (Group C) and 15 normal dogs (Group N) were subjected to cardiopulmonary bypass with 20 minutes of normothermic global ischemia. Functional indices studied were rate of rise of left ventricular pressure and the end-systolic pressure/volume ratio. Metabolic status was assessed by obtaining transmural myocardial biopsy specimens for measurement of adenosine triphosphate content. Myocardial blood flow was measured with radiolabeled microspheres. There were no significant differences between Group C and Group N in either functional index or blood flow measurement prior to global ischemia. At 45 minutes after ischemia, Group N animals had a significantly greater rate of rise of left ventricular pressure (at a left ventricular end-diastolic pressure of 0, 5, 10, and 15 mm Hg, p less than 0.025 to 0.05) and subendocarial perfusion (endocardial/epicardial flow ratio 0.961 +/- 0.037 versus 0.815 +/- 0.021, p less than 0.01). At 90 minutes after ischemia, Group N animals exhibited a significantly higher end-systolic pressure/volume ratio (4.9 +/- 0.7 versus 3.0 +/- 0.4 mm Hg/ml, p less than 0.05), rate of rise of left ventricular pressure (at an end-diastolic pressure of 0 to 20 mm Hg, p less than 0.005 to 0.05), and endocardial/epicardial flow ratio (1.065 +/- 0.046 versus 0.829 +/- 0.059, p less than 0.01). No differences in adenosine triphosphate content were found at any sampling period. The Group C left ventricles exhibited no hypertrophy but were significantly dilated compared to Group N (38.8 +/- 0.3 versus 30.1 +/- 0.2 mm, p less than 0.05). Inferior vena cava to pulmonary vein diversion produces cyanosis with left ventricular dilatation but without hypertrophy. It is proposed that abnormal loading characteristics of the left ventricle are responsible for the functional derangements that result from global ischemia.

Adenosine Triphosphate↗
PubMed1985

Improved right ventricular function after intra-atrial repair of transposition of the great arteries.

Current interest in the arterial switch operation for simple transposition of the great arteries (TGA) has led us to evaluate our latest patients who have undergone intra-atrial repair. Right ventricular function and overall results were compared in 32 patients who had undergone the Senning procedure between 1978 and 1983 and 26 patients who had undergone Mustard repair between 1971 and 1978). Deep hypothermia and circulatory arrest were used in all Senning operations and in 18 of 26 Mustard procedures. Cardiac catheterization was performed an average of 1 year after surgery in all patients. Postoperative right ventricular ejection fraction (EF) was below normal (less than 0.49) in 16 of 32 patients who underwent the Senning procedure and averaged 0.48 +/- 0.09. In the patients in this group with abnormal right ventricular EFs after repair there was a fall in the value after surgery (0.51 to 0.40, p less than .001), while in those with normal right ventricular EFs after repair there was no change (0.57 to 0.55, NS). All 32 patients who underwent the Senning procedure were compared with 26 patients who underwent the Mustard operation (13 treated between 1971 and 1974 and 13 treated between 1975 and 1978). An older age at surgery (12 +/- 7 vs 6 +/- 8 months, p less than .006) and a lower preoperative right ventricular EF (0.46 +/- 0.09 vs 0.54 +/- 0.08, p less than .007) characterized the Mustard vs the Senning group.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1984

Depression of contractility in isolated rabbit myocardium following exposure to iron: role of free radicals.

The mechanism of acute iron cardiotoxicity was investigated in isometrically contracting left atrial strips and right ventricular papillary muscles isolated from rabbit hearts. A 90-min exposure to iron (1.8 mM; as ferrous sulfate) reduced the peak-developed tension and the maximal rate of tension development. The presence of either N-acetylcysteine (20 mM), superoxide dismutase (2000 units/ml), or mannitol (5 mM) prevented this depression of contractility. Catalase (30,000 units/ml) was not protective against the effects of iron. Iron did not decrease myocardial adenosine triphosphate or creatine phosphate contents. The force-frequency relationship (positive staircase phenomenon) was examined in the absence and presence of iron. Iron did not reduce the positive inotropic response evoked by increasing the stimulation frequency, but at higher frequencies iron prolonged the time from peak tension to 90% relaxation. We conclude that acute iron cardiotoxicity may be mediated by free radical generation and does not involve impairment of myocardial high energy phosphate production.

Adenosine Triphosphate↗
PubMed1984

Myocardial dysfunction in children with acute meningococcemia.

Acute meningococcemia is frequently associated with cardiovascular collapse of uncertain cause. Review of the records of 12 consecutive children revealed clinical evidence of myocardial dysfunction in six (50%). Subsequently myocardial function was prospectively assessed clinically and echocardiographically in 12 children. Seven (58%) of the 12 children had echocardiographic evidence of myocardial dysfunction as defined by a depressed left ventricular shortening fraction (LVSF). The mean LVSF in these seven children was 0.25 +/- 0.03, as compared with the mean LVSF of 0.39 +/- 0.7 in the remaining children. The LVSF estimate of myocardial function strongly correlated with cardiac output as measured by standard thermodilution (r = 0.98, P less than 0.01). Acute meningococcemia was not fatal in those children without evidence of myocardial dysfunction. In contrast, three of the seven children with evidence of myocardial dysfunction died. In four children, echocardiographic evidence of left ventricular dysfunction preceded cardiovascular collapse and clinical recognition of myocardial dysfunction. In children with an initially low LVSF, recovery of LVSF was associated with survival. Children with acute meningococcemia may have impaired myocardial function as indicated by depressed LVSF, resulting in low cardiac output despite normal intravascular volume. Thus, in addition to restoring intravascular volume, knowledge of the status of myocardial function may help direct therapy toward optimizing myocardial contractility.

Acute Disease↗
PubMed1984

Acute effects of iron on contractile function in isolated rabbit myocardium.

Changes in contractile function following exposure to iron (Fe) salts were evaluated in isolated isometrically contracting rabbit left atrial strips and right ventricular papillary muscles. Fe acutely depressed myocardial contractility as evidenced by dose-related declines in developed force and maximal rate of force development. There were no significant changes in duration of contraction or resting force. The tissue Fe content was increased nearly 3-fold after a 60 min exposure to Fe and subsequently was not decreased by repeated washing or by treatment with deferoxamine. Isoproterenol, but not deferoxamine, reversed the Fe-mediated impairment of myocardial contractility. These findings suggest that in cases of severe acute iron poisoning, depression of cardiac contractility might occur which may be improved by treatment with isoproterenol.

Animals↗
PubMed1984

Short-term hemodynamic effects of hydralazine in infants with complete atrioventricular canal defects.

We evaluated the acute hemodynamic responses to hydralazine during cardiac catheterization in eight infants (ages 1.0 to 5.5 months) with congestive heart failure due to complete atrioventricular canal defect. Hydralazine administered intravenously (0.5 to 1.0 mg/kg body weight) increased heart rate and systemic blood flow and decreased mean right atrial pressure, systemic and pulmonic arterial pressures, systemic arteriolar resistance, and the ratio of pulmonary to systemic blood flow (p less than .05). The percentage of pulmonary flow contributed by shunted blood (percent left-to-right shunt; measured by indicator dilution) was decreased by hydralazine in six (mean = 85% before to 64% after hydralazine; p less than .01), but remained unchanged (79%) in two infants. The two infants with no change in percent left-to-right shunt had higher pulmonary arteriolar resistances (Rp) before hydralazine (mean = 12.8 vs 3.2 U/m2) and had greater declines in Rp (mean change = -5.1 vs + 0.3 U/m2) in response to hydralazine. Thus, if Rp does not fall, hydralazine reduces the percentage of left-to-right shunt over the short term and therefore might be useful for managing congestive heart failure in these infants. However, because the response varies, an evaluation of the short-term hemodynamic effects of hydralazine may be warranted in an attempt to select those infants who might respond favorably to long-term hydralazine therapy.

Blood Circulation↗
PubMed1984

Comparative effects of verapamil, nifedipine, and diltiazem on contractile function in the isolated immature and adult rabbit heart.

The effects of postnatal development on the systolic and diastolic responses to pharmacologic blockade of the slow inward calcium current were investigated in blood-perfused hearts isolated from immature (14-21-day-old) and adult rabbits. Isovolumic left ventricular developed pressure, resting pressure, and maximal rate of pressure development (+dP/dt) at cumulative doses of either verapamil, nifedipine, or diltiazem were determined by means of an intracavitary balloon. Myocardial contractile function in the immature heart was more sensitive to pharmacologic blockade of the slow inward calcium current than is the adult heart. Doses of verapamil, or nifedipine, that comparably reduced pretreatment developed pressure and +dP/dt were approximately 10-fold less in immature as compared to the adult heart. The dose of diltiazem which reduced developed pressure and dP/dt by 50% was 3-fold less in immature as compared to the adult heart. Verapamil and nifedipine decreased resting pressure in the adult but not in the immature heart. Conversely, diltiazem decreased resting pressure in the immature while not affecting resting pressure in adult hearts. Thus, postnatal cardiac development affects both the systolic and diastolic responses to calcium channel blockade. In addition, diltiazem appears to be qualitatively and quantitatively different from verapamil and nifedipine with respect to the age-related cardiac effects of calcium channel blockade.

Aging↗
PubMed1984

Global ischemia in the immature canine ventricle. Enhanced protective effect of verapamil and potassium.

The efficacy of the addition of verapamil to a cardioplegic solution was evaluated in immature canine hearts subjected to normothermic global ischemia. Two groups of mongrel puppies less than 10 weeks old were subjected to 30 minutes of global myocardial ischemia while on cardiopulmonary bypass. One group (Group K) was arrested with cardioplegic solution containing 20 mEq/L of KCl; the other group (Group K + V) was arrested with the same solution containing 0.2 mg/kg of verapamil. Ultrasonic crystals were placed for measurement of left ventricular dimensions, and micromanometers measured left ventricular pressures. Functional measurements included left ventricular strain, first derivative of left ventricular pressure (dP/dt), and the end-systolic pressure/volume ratio (Emax). Metabolic recovery was assessed by measuring myocardial adenosine triphosphate (ATP) content. Ninety minutes following ischemia, Group K + V exhibited greater minor axis strain at a left ventricular end-diastolic pressure of 15 and 20 mm Hg (p less than 0.05), greater dP/dt (p less than 0.05 to 0.001), and greater Emax (p less than 0.05) than Group K. ATP content in Group K + V was greater at 60 minutes (Group K + V: 12.74 +/- 1.60 mumol/gm; Group K: 8.39 +/- 1.30, p less than 0.05) and 90 minutes (Group K + V: 10.34 +/- 0.46; Group K: 7.55 +/- 1.42, p less than 0.05) after ischemia. The addition of verapamil to a cardioplegic solution containing potassium enhances the recovery of function and high-energy phosphate stores in the immature myocardium following normothermic global ischemia.

Animals↗
PubMed1983

Modulation by propranolol of the lysyl cross-links in aortic elastin and collagen of the aneurysm-prone turkey.

dl-Propranolol (propranolol) fed to immature and mature aneurysm-prone turkeys (Broad-Breasted White, BBW) for 6 weeks significantly raised the tensile strength of tissue rings from the abdominal aorta. The drug-mediated increase in tensile strength values was dose-related and independent of its heart rate- and arterial pressure-lowering effects. Propranolol acts, in part, by (a) stimulating lysyl oxidase to produce greater amounts of reactive aldehydes for intermolecular cross-links, (b) enhancing the progression of chemically unstable to stable forms of intermolecular elastin cross-links (lysinonorleucine and the desmosines), and (c) reducing the density of the age-related intermolecular cross-linking of collagen (pyridinoline). These propranolol effects on the lysyl cross-links were demonstrated in both the immature and mature animals and suggest a heretofore unrecognized potential for this widely used cardiovascular drug.

Aneurysm↗
PubMed1983

Assessment of ventricular size and function in congenitally corrected transposition of the great arteries.

Twenty-four quantitative cineangiographic studies were performed in 19 patients with congenitally corrected transposition of the great arteries to assess right and left ventricular size and function. Ages ranged from 7 days to 44 years and associated lesions included ventricular septal defect (13 of 19), pulmonary stenosis (9 of 19), and systemic (tricuspid) valvular insufficiency (7 of 19). Systemic (anatomically right) ventricular end-diastolic volume was within normal limits in most patients and averaged 119% of predicted normal. Pulmonary (anatomically left) ventricular end-diastolic volume also was normal in most patients, averaged 112% of predicted, and was not different from systemic (right) ventricular end-diastolic volume. Systemic ventricular ejection fraction (RVEF) averaged 0.61 +/- 0.02 and was not different from pulmonary ventricular ejection fraction (LVEF) (0.65 +/- 0.02), but important differences were apparent when age was considered. With exclusion of 2 patients with hypoplastic systemic ventricles and 2 studies performed less than 6 months after open heart surgery, all 12 patients aged less than 10 years had a normal RVEF, whereas 2 of 5 patients aged greater than 17 years had a definitely low RVEF and 1 of 5 had a value at the lower limit of normal. In children, systemic and pulmonary ventricular pump function is usually normal in congenitally corrected transposition of the great arteries and any deviation from normal should suggest ventricular hypoplasia or an increase in afterload. After childhood, systemic ventricular dysfunction is more common and may reflect the inability of the anatomic right ventricle to function as the systemic pumping chamber over a normal lifetime in most patients with congenitally corrected transposition of the great arteries.

Adolescent↗
PubMed1983

Radionuclide stroke count ratios for assessment of right and left ventricular volume overload in children.

The ratio of left ventricular to right ventricular stroke counts measured by radionuclide angiography has been used in adults to estimate the severity of left-sided valvular regurgitation. The validation of this technique in children for assessment of right and left ventricular volume overload is reported herein. Radionuclide stroke count ratios in 60 children aged 0.5 to 19 years (mean 11) were determined. Based on their diagnoses, the patients were divided into 3 groups: (1) normal--40 patients with no shunts or valvular regurgitation, (2) left ventricular volume overload--13 patients with mitral or aortic regurgitation, or both, and (3) right ventricular volume overload--7 patients, 2 with severe tricuspid regurgitation, 3 with atrial septal defects, and 2 with total anomalous pulmonary venous drainage. The radionuclide stroke count ratio clearly differentiated these groups (p less than 0.05): normal patients had a stroke count ratio of 1.04 +/- 0.17 (mean +/- 1 standard deviation), the left ventricular volume overload group had a stroke count ratio of 2.43 +/- 0.86, and the right ventricular volume overload group had a stroke count ratio of 0.44 +/- 0.17. In 22 of our 60 patients, radionuclide stroke count ratios were compared with cineangiographic stroke volume ratios, resulting in a correlation coefficient of 0.88. It is concluded that radionuclide ventriculography is an excellent tool for qualitative and quantitative assessment of valvular regurgitation in children.

Adolescent↗
PubMed1983

Emergency palliation of critical valvular aortic stenosis. A new application of prostaglandin E1.

Prostaglandin E1 (PGE1) was administered by continuous infusion to a critically III 3-day-old infant with severe stenosis of the aortic valve. A beneficial response was evidenced by increases in systemic BP, pulses, perfusion, urinary output, and arterial pH. The infusion of PGE1 improved and stabilized the infant's condition so that cardiac catheterization and surgery could be performed. Successful aortic valvulotomy was performed with continued PGE1 infusion. To out knowledge, this report is the first to describe a patient in whom PGE1 was used successfully for palliation of critical aortic valvular stenosis.

Aortic Valve Stenosis↗
PubMed1983

The B-aminopropionitrile-fed turkey: a model for detecting potential drug action on arterial tissue.

Broad-breasted white male turkeys develop hypertension, tachycardia and aortic arteriosclerosis spontaneously by approximately 5 weeks of age. When fed B-aminopropionitrile (BAPN), aortic tensile strengths are lowered, and a high percentage of the turkeys die from aortic dissecting aneurysms. There are essentially no deaths from aneurysms when either dl-propranolol or reserpine is fed in concert with BAPN; practolol and soltalol partially protect the BAPN-fed turkey from lethal aneurysms while hydralazine and phenelzine sulphate potentiate mortality from aneurysms. Dl-propranolol decreases and reserpine increases dP/dtmax and both drugs lower arterial pressure and heart rate when fed with BAPN. Such diets also decrease the ultrastructural disarray of collagenous and elastic fibres in the media of the abdominal aorta that occurs from the feeding of BAPN and thereby raise aortic tensile strength. Sotalol and practolol when fed to BAPN-fed turkeys lower blood pressure and dP/dtmax, but neither drug affects aortic tensile strength and both counteract the deleterious effect of BAPN on the ultrastructure of collagenous and elastic fibres to a minor degree. Phenelzine sulphate does not affect arterial pressure while hydralazine reduces arterial pressure; both drugs decrease aortic tensile strength and increase the ultrastructural disruption of aortic elastin and collagen in the BAPN turkey. The results suggest that dl-propranolol, reserpine, phenelzine sulphate, and hydralazine have an action on aortic tissue and indicate the usefulness of the BAPN-fed turkey as a model for identifying potential drug effects on aortic elastin and collagen.

Aminopropionitrile↗
PubMed1983

Experimental diabetes mellitus and age-simulated changes in intact rat dermal collagen.

Alterations in the physical properties of dermal collagen by streptozotocin-induced diabetes mellitus were investigated in young adult Lewis rats by mounting standardized rings of tail skin on an Instron Universal Testing Apparatus and measuring the thermally induced isometric contraction and stress at rupture of the tissue. Diabetes significantly increased the maximum tension (Tmax) of the contraction and raised the temperature for the Tmax while the stress at rupture (TR) was unaffected when compared with values for controls fed ad libitum and controls fed restricted diets for weight loss equivalence. The diabetes-mediated changes in thermal contractility appeared to be independent of the collagen concentration or negative caloric balance and resembled the reported age-related change in rat skin collagen.

Aging↗