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Biomedical subjects

T DeMarco

Publications and source records attributed to T DeMarco.

At least 19 recordsLinked to original sources
PubMed1997

Evaluation of acute dual-chamber pacing with a range of atrioventricular delays on cardiac performance in refractory heart failure.

OBJECTIVES: This study evaluated how variations in atrioventricular (AV) delay affect hemodynamic function in patients with refractory heart failure being supported with intravenous inotropic and intravenous or oral inodilating agents. BACKGROUND: Although preliminary data have suggested that dual-chamber pacing with short AV delays may improve cardiac function in patients with heart failure, detailed Doppler and invasive hemodynamic assessment of patients with refractory New York Heart Association class IV heart failure has not been performed. METHODS: Nine patients with functional class IV clinical heart failure had Doppler assessment of transvalvular flow and right heart catheterization performed during pacing at AV delays of 200, 150, 100 and 50 to 75 ms. RESULTS: Systemic arterial, pulmonary artery, right atrial and pulmonary capillary wedge pressures, cardiac index, systemic and pulmonary vascular resistances, stroke volume index, left ventricular stroke work index (SWI) and arteriovenous oxygen content difference demonstrated no significant changes during dual-chamber pacing with AV delays of 200 to 50 to 75 ms. There were also no changes in the Doppler echocardiographic indexes of systolic or diastolic ventricular function. The study was designed with SWI as the outcome variable. Assuming a clinically significant change in the SWI of 5 g/min per m2, a type I error of 0.05 and the observed standard deviation from our study, the observed power of our study is 85% (type II error of 15%). CONCLUSIONS: Changes in AV delay between 200 and 50 ms during dual-chamber pacing do not significantly affect acute central hemodynamic data, including cardiac output and systolic or diastolic ventricular function in patients with severe refractory heart failure due to dilated cardiomyopathy.

Aged↗
PubMed1996

Comparison of adenosine to dipyridamole in degree of coronary hyperemic response in heart transplant recipients.

Transplant coronary vasculopathy is associated with endothelial dysfunction. Microvascular function, assessed as coronary flow reserve, has been reported to be normal. We used intracoronary ultrasound technology to simultaneously assess conductance and resistance vessel function in response to standard dosages of the vasodilators adenosine and dipyridamole. Coronary hemodynamic changes were assessed in 11 heart transplant recipients, at a mean duration of 784 +/- 516 days after transplantation, using a 3.2Fr or 4.3Fr, 30-MHz ultrasound imaging catheter over a 0.014-inch Doppler guidewire. Measures of coronary average peak flow velocity (APV) and coronary cross-sectional area (CSA) were used to calculate volumetric flow during intravenous infusions of adenosine (140 micrograms/kg/min over 4 minutes) and dipyridamole (140 micrograms/kg/min over 4 minutes). Flow reserve was assessed as a ratio of maximal pharmacologically induced flow to steady baseline flow before infusion. Increase in APV (261.9% vs 194.6%, p = 0.005), lumenal CSA (+11.8% vs +4.2%, p = 0.01), peak volumetric blood flow (515.8 vs 317.2 ml/min, p = 0.007), and coronary flow reserve (2.93 +/- 0.74 vs 1.99 +/- 0.53, p < 0.001) were higher with adenosine than dipyridamole. Both agents caused similar decreases in systemic blood pressure and little change in heart rate. Adenosine appears to be a more potent coronary vasodilator than dipyridamole in denervated human transplant subjects. Adenosine has a vasodilator effect at the epicardial and microvascular levels, resulting in an overall increase in volumetric flow. Flow reserve in response to both endothelium-independent agents is decreased in comparison with previously established values, but the attenuation is greater with dipyridamole.

Adenosine↗
PubMed1995

Abnormal pulmonary artery pressure profile after cardiac transplantation: an exercise Doppler echocardiographic study.

This study was designed to test the hypothesis that pulmonary artery pressure at rest and during exercise differs between patients with a transplanted heart and normal subjects and to determine the mechanisms responsible for the difference. Twenty-one patients who had undergone heart transplantation 1.5 to 27 months earlier without current evidence of acute cardiac rejection and 25 normal subjects were studied by exercise Doppler echocardiography. Systolic pulmonary artery pressure was higher at baseline in heart transplant patients than in normal subjects, at 31.6 +/- 9 mm Hg (mean +/- SD) versus 22.5 +/- 4, respectively (p = 0.0001). The increase in systolic pulmonary artery pressure with exercise was 1.4 times higher in heart transplant patients and correlated with pretransplantation pulmonary vascular resistances (r = 0.55; p = 0.01). In contrast, cardiac index at baseline or during exercise did not differ between the two groups. Diastolic parameters and ejection fraction at baseline or during exercise did not correlate with systolic pulmonary artery pressure. In conclusion, Doppler exercise echocardiography offers an alternative, safe method hemodynamic study of the transplanted heart. Although an abnormal increase in left ventricular filling pressure with exercise has been well documented, further studies are needed to investigate and characterize potential abnormalities in pulmonary vascular tone in the transplanted heart.

Adult↗
PubMed1994

Effect of orthotopic cardiac transplantation on peripheral vascular function in congestive heart failure: influence of cyclosporine therapy.

The objective of this study was to examine peripheral vascular function before and after cardiac transplantation and to assess the effect of immunosuppressive therapy on peripheral vascular reactivity. Peripheral vascular function abnormalities present in congestive heart failure may be reversed with cardiac transplantation, but immunosuppressive therapy may alter these changes in the peripheral vasculature. Venous occlusion plethysmography was used to study peripheral vascular function in nine patients with severe congestive heart failure who underwent cardiac transplantation. Forearm blood flow and forearm vascular resistance were measured in patients with congestive heart failure in response to cold stimulation, maximal hyperemia, and hand grip exercise (1) before transplantation; (2) 24 to 36 hours posttransplantation before the commencement of cyclosporine; (3) 6 to 8 days posttransplantation in the presence of therapeutic cyclosporine levels; and (4) 6 weeks posttransplantation. Venous capacitance was also measured. After cardiac transplantation, mean arterial pressure increased and remained elevated. Forearm blood flow initially increased after transplantation but subsequently decreased with cyclosporine. Cold-induced reflex sympathetic activation decreased immediately after transplantation but was significantly enhanced with cyclosporine. The maximal vasodilatory response following ischemic cuff occlusion and with 5 minutes of isometric hand grip exercise increased significantly after transplantation and remained improved at 6 weeks. Thus after cardiac transplantation, peripheral vasodilator function improves and is not altered by cyclosporine. However, with cyclosporine therapy resting forearm vascular resistance increases and reflex sympathetic vasoconstriction is enhanced, suggesting that cyclosporine may potentiate adrenergic-mediated peripheral vasoconstriction and thus may contribute to posttransplant hypertension.

Analysis of Variance↗
PubMed1994

Cyclosporine impairs release of endothelium-derived relaxing factors in epicardial and resistance coronary arteries.

BACKGROUND: Cyclosporin A is reported to impair endothelium-mediated vasorelaxation and induce endothelin release in some noncoronary vascular beds. We wished to determine whether acute cyclosporine administration induces endothelial dysfunction in coronary conductance or resistance arteries. METHODS AND RESULTS: We examined the effect of intracoronary acetylcholine, N omega-nitro-L-arginine methyl ester (L-NAME), L-arginine, nitroglycerin, and adenosine before and after acute cyclosporine administration (3 mg/kg IV over 30 minutes) in anesthetized dogs. Flow velocity was measured with a 0.014-in Doppler wire to assess resistance vessel responses, and epicardial coronary lumen area was simultaneously measured with a 4.3F, 30-MHz imaging catheter inserted over the Doppler wire. In 6 dogs, acetylcholine-induced increase in flow velocity was attenuated by cyclosporine in vehicle (137% to 55% at 10(-5) mol/L, P < .001), as was acetylcholine-induced epicardial vasodilation (14.1% to 6.7% at 10(-5) mol/L, P < .001). Vasodilation in response to intracoronary nitroglycerin (200 micrograms) and adenosine (6 mg) were unchanged by cyclosporine. Epicardial vasoconstriction with L-NAME (10(-4) mol/L) was reduced by cyclosporine (Pre, 7.4 +/- 0.9%; Post, 2.6 +/- 1.2%; P = .04), but L-arginine (10(-4) mol/L) had no effect after cyclosporine. In another 5 dogs, pure cyclosporine impaired acetylcholine-induced vasodilatation to the same degree as cyclosporine in vehicle (Cremophor); vehicle infusion did not impair endothelial function. In 5 more dogs, cyclosporine did not increase either arterial or coronary sinus concentrations of endothelin-1. CONCLUSIONS: The present study shows that cyclosporine acutely impairs release of endothelium-derived relaxing factor in canine conductance and resistance coronary arteries and provides evidence for decreased epicardial nitric oxide release after cyclosporine. The potential contribution of acute cyclosporine-induced coronary endothelial dysfunction to posttransplant vasculopathy needs further study.

Acetylcholine↗
PubMed1994

Nonglycoside inotropes in congestive heart failure. Are they beneficial or harmful?

Nonglycosidic adrenergic and nonadrenergic inotropic drugs improve systemic hemodynamics and left ventricular function in patients with severe congestive heart failure. As these beneficial effects are observed with short-term therapy, the use of these agents should be restricted to the treatment of acute heart failure. Long-term therapy with adrenergic agents as well as the phosphodiesterase inhibitors appears to enhance mortality in patients with chronic systolic heart failure. Potential indications for long-term therapy with nonglycosidic inotropic drugs include vesnarinone and ibopamine for selected patients with refractory heart failure or as pharmacologic bridges to cardiac transplantation.

Animals↗
PubMed1993

Importance of oxygen-haemoglobin binding to oxygen transport in congestive heart failure.

OBJECTIVE: To assess the importance of 2,3-diphosphoglycerate (2,3-DPG) and oxygen-haemoglobin binding to oxygen transport in patients with congestive heart failure. METHODS: In 30 patients with severe congestive heart failure, arterial, mixed venous, and coronary sinus venous blood concentrations of 2,3-DPG were measured and systemic output and coronary sinus blood flow were measured by a thermodilution technique. Oxygen-haemoglobin affinity was expressed as the oxygen tension in mm Hg at which blood is 50% saturated with oxygen (P50). RESULTS: Compared with normal values, 2,3-DPG was high in arterial blood (2.58 mumol/ml, p = 0.01; 20.8 mumol/g haemoglobin, p < 0.0001). Significant gradients between arterial, mixed venous, and coronary sinus blood 2,3-DPG concentrations were also found (mixed venous = 2.40 mumol/ml, p = 0.05 v arterial blood; coronary sinus venous blood = 2.23 mumol/ml, p < 0.04 v arterial blood). P50 was correspondingly high compared with the accepted normal value (mean 29.7 mm Hg, normal 26.6 mm Hg, p < 0.001). Systemic oxygen transport (351 ml O2/min/m2) varied directly with the forward cardiac index (r = 0.89, p < 0.0001). There was no relation between systemic oxygen transport and arterial oxygen content. Similarly, myocardial oxygen transport was found to vary directly with coronary sinus blood flow. Calculations of changes in cardiac index and coronary sinus blood flow at normal oxygen-haemoglobin binding indicate that a considerable increase in cardiac index and coronary blood flow would be required to maintain similar systemic and myocardial oxygen transport. CONCLUSIONS: In patients with severe heart failure increased 2,3-DPG and reduced oxygen-haemoglobin binding may be compensatory mechanisms that maintain adequate systemic and delivery of oxygen to myocardial tissue.

2,3-Diphosphoglycerate↗
PubMed1991

Transvenous coronary ultrasound imaging. A novel approach to visualization of the coronary arteries.

BACKGROUND: Catheter-based ultrasound is a new imaging modality to examine endovascular detail in the coronary circulation. This technique requires direct placement of the catheter in the arterial segment of interest. METHODS AND RESULTS: We examined the feasibility of a less invasive approach by imaging the coronary arterial circulation by using a 5F (30 MHz) imaging catheter placed in the cardiac venous system. Using simultaneous fluoroscopy, we studied anesthetized closed-chest dogs (n = 6) and human subjects undergoing right heart catheterization (n = 11). After cannulation of the coronary sinus, the circumflex coronary artery (Cx) was visualized from the great cardiac vein (GCV), and on advancing the catheter into the anterior interventricular vein (AIV), the left anterior descending artery (LAD) was identified. Where artery and vein were parallel to each other, circular cross-sectional images of the coronary artery were obtained, whereas oblique and transverse orientation of artery to vein produced ellipsoid images or long-axis images. In the dogs, ultrasound-determined cross-sectional area of the coronary arteries (4.81 +/- 0.18 mm2) correlated closely with angiography (4.77 +/- 0.21 mm2) (r = 0.91, p less than 0.001). In humans, the Cx was readily visualized from the GCV in all subjects but because of anatomic variability, the LAD was seen less consistently from the AIV (73%). There was significant correlation between ultrasound-determined cross-sectional areas of the coronary arteries (8.25 +/- 0.34 mm2) with those from angiography (8.59 +/- 0.3 mm2) (r = 0.82, p = 0.001) in humans. In all subjects, the ultrasound transducer could be safely advanced into the AIV to the cardiac apex. Limitations of the technique include ultrasonic penetration problems, caused in part by the large size of human coronary veins and variability in artery-vein relations. CONCLUSIONS: We conclude that transvenous imaging of coronary arteries with intravascular ultrasound is a less invasive, promising new approach to the study of structure and morphology in the coronary vasculature.

Animals↗
PubMed1991

Progression of systemic disease and reduced long-term survival in patients with cardiac amyloidosis undergoing heart transplantation. Follow-up results of a multicenter survey.

Amyloid heart disease has been considered a contraindication for cardiac transplant based on the hypothesis that it is a systemic disease and that amyloid deposition would occur in the cardiac allograft. A survey was sent to all of the US centers and a limited number of Canadian and European centers listed with the International Registry. Twenty-four centers responded, and data were ultimately provided for a total of 10 patients (3 men, 7 women, mean age 48 years, range 30-60 years) who were transplanted for cardiac amyloid. The diagnosis of cardiac amyloidosis was made histologically on endomyocardial biopsy and/or examination of the explanted heart. Additional documented organ involvement included liver (two of 10), rectal (three of 10), renal (two of 10), gingiva (two of 10), and tongue (one of 10), although invasive biopsies were not performed in a majority of patients. A specific amyloid protein was identified in eight patients (seven lambda, one kappa immunoglobulin light chain). Although four of the surviving nine patients (one perioperative death) developed recurrent amyloid deposition in the allograft, it was detected solely by electron microscopy in two of these and had no clinical significance. There was, however, a progressive risk of major organ involvement with organ function impairment in this group (22% at 12 months, 50% at 24 months, 66% at 48 months). Although the immediate and early postoperative outcomes were not dissimilar between this group and patients undergoing transplantation for other cardiac diseases, late survival was reduced (39% at 48 months) compared with the larger population, but differences were not statistically significant due to the small amyloid sample size (p = 0.16).(ABSTRACT TRUNCATED AT 250 WORDS)

Amyloidosis↗
PubMed1990

Iron metabolism.

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Anemia, Hypochromic↗
PubMed1989

Enhancing children's participation in physical activity.

The school's role in enhancing children's participation in physical activity, particularly activities considered vigorous, is examined in this article. Children often elect not to take physical education classes. Even students who take physical education frequently fail to show marked gains of fitness since the intensity, duration, and nature of activities are inadequate to elicit cardiorespiratory adaptations. However, the school can and should play a major role in promoting children's interest in aerobic physical activities. Furthermore, the school can sustain this involvement by encouraging students to enroll in physical education by teaching the value of regular, vigorous physical activity, and by providing opportunities to engage daily in vigorous yet enjoyable activities. Recommendations are offered for increasing exercise participation and for improving children's attitudes toward physical activity within the school environment.

Adolescent↗
PubMed1986

Poor correlation between pulmonary arterial wedge pressure and left ventricular end-diastolic volume after coronary artery bypass graft surgery.

The authors studied 12 surgical patients in the intensive care unit post coronary artery bypass graft surgery and ten nonsurgical patients in the coronary care unit with chronic heart failure to determine the usefulness of the pulmonary arterial wedge pressure as an indicator of left ventricular preload. Left ventricular end diastolic volume was derived from concomitant determination of ejection fraction (gated blood pool scintigraphy) and stroke volume (determined from thermodilution cardiac output). In the nonsurgical patients, there was a significant correlation between changes in pulmonary arterial wedge pressure and left ventricular end-diastolic volume (P less than 0.05, r = 0.57). In the 12 patients studied during the first few hours after surgery, there was a poor correlation between changes in pulmonary wedge pressure (range = 4-32 mmHg) and left ventricular end-diastolic volume (range = 25-119 ml/m2), and a poor correlation between pulmonary arterial wedge pressures and stroke work index. In contrast, there was a good correlation between left ventricular end-diastolic volume and stroke work index. The poor correlation between the pulmonary arterial wedge pressure and left ventricular end-diastolic volume was not explained by changes in systemic or pulmonary vascular resistance. The altered ventricular pressure-volume relationship may reflect acute changes in ventricular compliance in the first few hours following coronary artery bypass graft surgery. While measurement of pulmonary arterial wedge pressure remains valuable in clinical management to avoid pulmonary edema, it cannot reliably be used as an index of left ventricular preload while attempting to optimize stroke volume in patients immediately following coronary artery bypass graft surgery.

Aged↗
PubMed1982

Living donor nephrectomy: factors influencing morbidity.

Recent interest in transperitoneal live donor nephrectomy prompted us to review our experience with 104 live donor nephrectomies performed through a standard flank extraperitoneal approach. There were no deaths and 14.4 per cent of the patients had minor complications that were managed easily. Factors influencing morbidity in the voluntary donor are analyzed.

Adult↗
PubMed1978

Effect of limiting post-shock pulmonary edema on mortality from bacterial pneumonia.

Dogs were subjected to hemorrhagic shock and then resuscitated according to physiological parameters. Randomly selected dogs received a sublethal dose of intratracheal microorganisms. In comparing the results with those previously reported from our laboratory, in which animals received an 85% greater resuscitation of Ringer's lactate, it appears that pulmonary edema in the post-shock contaminated state can be limited. Furthermore, through minimization of pulmonary edema, pulmonary defenses appear to be improved and mortality from infection reduced.

Animals↗
PubMed1977

Put it in writing!

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Education, Dental↗
PubMedDate not supplied

MR imaging of reversible cyclosporin A-induced neurotoxicity.

Neurotoxicity is a recognized complication of cyclosporin A (CsA) therapy in patients undergoing organ transplantation. It is most commonly manifested by fever, seizures, and altered mental status. Cortical blindness and speech and motor disturbances can also occur. Changes seen in cerebral white matter on imaging studies are nonenhancing areas of hypoattenuation on CT and T2 prolongation on MR. We report three cases of CsA-induced neurotoxicity in which reversible changes were observed in the cerebral white matter. In the first patient, CsA neurotoxicity occurred 1 week following orthotopic liver transplantation. In the second patient, CsA neurotoxicity coincided with an episode of severe systemic hypertension 4 weeks after cardiac transplantation. The third patient experienced seizures 1 month after heart/lung transplantation for cystic fibrosis. A current theory postulates a relationship between diminished serum cholesterol and CsA neurotoxicity. This theory, however, does not satisfactorily address all cases of CsA neurotoxicity. In particular, serum cholesterol measurements were normal in cases 2 and 3 and probably were normal in case 1, despite diminished cholesterol levels preoperatively. Although the matter of CsA-induced neurotoxicity remains unresolved, we suggest that endothelin, a newly described neuropeptide that causes intense vasoconstriction and that has been implicated in cerebral vasospasm, may potentiate CsA-induced damage to endothelium and promote CsA neurotoxicity.

Adult↗
PubMedDate not supplied

Transcoronary and pulmonary vascular dynamics of endothelin-1 in heart transplant recipients.

BACKGROUND: Endothelin-1, a potent endothelium-derived vasoconstrictor peptide, has recently been shown to be elevated in heart transplant recipients and may be a participant in posttransplantation vasculopathy. METHODS: We measured peripheral venous endothelin-1 concentrations in eight heart transplant recipients and eight age- and gender-matched healthy controls. Subsequently, in 21 transplant recipients, right atrial, aortic, and coronary sinus plasma was obtained and endothelin-1 levels were measured. Potential correlations to donor and recipient age, cyclosporine levels, hemodynamic parameters, donor heart ischemic time, time from transplantation, and serum creatinine were examined. In eight more patients, right atrial levels of endothelin-1 were measured before and after endomyocardial biopsy to examine the effect of this procedure on endothelin-1 concentrations. RESULTS: Peripheral endothelin-1 concentrations were significantly higher in heart transplant recipients (45.6 +/- 1.8 versus 25.8 +/- 2.3, p < 0.001). Multiple regression analysis showed a significant correlation between right atrial endothelin-1 and pulmonary artery systolic pressure (r = 0.48), as well as serum creatinine (r = 0.52). No relation to blood pressure, right atrial pressure, pulmonary vascular resistance, recipient age, cyclosporine levels, or donor heart ischemic time was observed. In 11 patients, a 38% +/- 7% fall in endothelin-1 levels across the pulmonary bed was observed, suggesting extraction across the lung in these subjects. Nine patients had net release of endothelin-1 (95% +/- 26% rise) across the coronary vascular bed, whereas 12 patients showed net extraction (24% +/- 4% fall). Endomyocardial biopsy had no influence on endothelin-1 levels (prebiopsy: 48.3 +/- 1.7; postbiopsy: 42.3 +/- 2.34; p = Not significant). CONCLUSION: These findings suggest that endothelin-1 levels in transplant recipients may be influenced by renal function and may contribute to pulmonary hypertension. The significance of transcardiac release of endothelin in some patients is unclear: further studies are needed to determine the pathophysiologic significance of endothelin-1 in heart transplant recipients.

Adult↗