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Biomedical subjects

J W Pratt

Publications and source records attributed to J W Pratt.

15 recordsLinked to original sources
PubMed2000

Current indications for left thoracotomy in coronary revascularization and valvular procedures.

BACKGROUND: Left thoracotomy is infrequently used for cardiac procedures, but its application in reoperative and minimally invasive coronary revascularization and in valvular procedures has been reported recently. METHODS: Three case reports and a review of the current literature illustrate the unique benefits of this approach for myocardial revascularization and valve replacement. RESULTS: Reoperative coronary revascularization of the left anterior descending and circumflex coronary arteries was performed off-pump via a left posterolateral thoracotomy. For the second case, this approach was used for coronary artery bypass grafting of the right coronary and left anterior descending arteries with femoral-femoral cardiopulmonary bypass in a patient with congestive heart failure and coronary artery disease who also required closure of a patent ductus arteriosus. In the third case, mitral valve replacement using femoral venous and aortic cannulation for cardiopulmonary bypass was performed via a left thoracotomy to avoid a retrosternal gastric conduit in a patient with severe mitral stenosis and congestive heart failure. All patients returned to normal activity and are asymptomatic. CONCLUSIONS: These case reports and a comprehensive review of the literature demonstrate the utility of left thoracotomy as an alternative approach to standard median sternotomy in selected cases of revascularization and valvular procedures.

Aged↗
PubMed2000

Neonatal intrapericardial teratomas: clinical and surgical considerations.

Intrapericardial teratomas are rare primary cardiac tumors of infancy and childhood. We describe three neonates with intrapericardial teratomas diagnosed during fetal life and treated after birth. Clinical and anatomic considerations suggest that cardiopulmonary bypass provides for safe tumor dissection and complete excision of the tumor, thereby decreasing the risk of recurrence.

Cardiopulmonary Bypass↗
PubMed2000

A comparison of hemodynamic changes during the transition from mechanical ventilation to T-piece, pressure support, and continuous positive airway pressure in canines.

The immediate transition from positive pressure mechanical ventilation to spontaneous ventilation may generate significant cardiopulmonary hemodynamic alterations based on the mode of weaning selected, particularly in individuals with preexisting cardiac dysfunction. The purpose of this study was to compare hemodynamic responses associated with the initial transition to 3 modes of ventilator weaning (spontaneous ventilation/T-piece, pressure support [PS], and continuous positive airway pressure [CPAP]). Right ventricular hemodynamic responses were evaluated with a thermodilution pulmonary artery catheter; while left ventricular hemodynamic responses were measured by a transducer-tipped Millar catheter and conductance catheter. Two groups of canines were studied. Group 1: normal biventricular function (n = 10) and group 2: propranolol-induced biventricular failure (n = 10). Dependent variables were measured at baseline on controlled mechanical ventilation (MV) and following the initial transition to each of 3 randomized spontaneous ventilatory conditions: T-piece, PS 5 cmH2O, and CPAP 5 cmH2O. Both groups significantly increased cardiac output in response to T-piece. Right ventricular stroke work was also significantly increased with T-piece and CPAP in both groups of subjects. Left ventricular response depended on baseline ventricular function. Baseline ventricular function influenced hemodynamic response to the immediate transition from mechanical to spontaneous ventilation. There were also differential hemodynamic responses based on the ventilatory mode. Consideration of baseline cardiac function may be an important factor in the selection of an appropriate mode of spontaneous ventilation following controlled MV.

Animals↗
PubMed1999

Minimally invasive coronary artery bypass grafting for myocardial muscle bridging.

Myocardial bridging is a congenital anomaly of the left anterior descending coronary artery (LAD), which is associated with myocardial ischemia and infarction, cardiac arrhythmias, and sudden cardiac death. Two cases are reported of symptomatic myocardial bridging refractory to medical management treated by minimally invasive coronary artery bypass grafting without cardiopulmonary bypass. We conclude that minimally invasive coronary artery bypass techniques are appropriate alternatives to endovascular stent placement, muscle bridge division, or aortocoronary grafting with cardiopulmonary bypass for the management of symptomatic myocardial bridging.

Adult↗
PubMed1998

Effects of hypoproteinemia-induced myocardial edema on left ventricular function.

In previous studies, we observed left ventricular (LV) systolic and diastolic dysfunction in association with interstitial myocardial edema (IME) induced by either coronary venous hypertension (CVH) or lymphatic obstruction. In the present study, we examined the effects of myocardial edema induced by acute hypoproteinemia (HP) on LV systolic and diastolic function. We also combined the methods of HP and CVH (HP-CVH) to determine their combined effects on LV function and myocardial water content (MWC). We used a cell-saving device to lower plasma protein concentration in HP and HP-CVH groups. CVH was induced by inflating the balloon in the coronary sinus. Six control dogs were treated to sham HP. Conductance and micromanometer catheters were used to assess LV function. Contractility, as measured by preload recruitable stroke work, did not change in control or HP groups but declined significantly (14.5%) in the HP-CVH group. The time constant of isovolumic LV pressure decline (tau) increased significantly from baseline by 3 h in the HP (24.8%) and HP-CVH (27.1%) groups. The end-diastolic pressure-volume relationship (stiffness) also increased significantly from baseline by 3 h in the HP (78.6%) and HP-CVH (42.6%) groups. Total plasma protein concentration decreased from 5.2 +/- 0.2 g/dl at baseline to 2.5 +/- 0.0 g/dl by 3 h in the HP and HP-CVH groups. MWC of the HP (79.8 +/- 0.25%) and HP-CVH groups (79.8 +/- 0.2%) were significantly greater than that of the control group (77.8 +/- 0.3%) but not different from one another. In conclusion, hypoproteinemia-induced myocardial edema was associated with diastolic LV dysfunction but not systolic dysfunction. The edema caused by hypoproteinemia was more than twice that produced by our previous models, yet it was not associated with systolic dysfunction. CVH had a negative inotropic effect and no significant influence on MWC. IME may not have the inverse causal relationship with LV contractility that has been previously postulated but appears to have a direct causal association with diastolic stiffness as has been previously demonstrated.

Acid-Base Equilibrium↗
PubMed1997

Impairment of left ventricular function by acute cardiac lymphatic obstruction.

OBJECTIVES: We performed the following study to define the effects of acute cardiac lymphatic obstruction on left ventricular (LV) systolic and diastolic function. METHODS: Cardiac lymphatic obstruction was created in 8 pentobarbital-anesthetized dogs by identifying (Evans blue) and ligating the right and left epicardial lymphatics, the afferent and efferent lymphatics associated with the pretrachael and cardiac lymph nodes, and the thoracic duct. Left ventricular function was assessed by analysis of micromanometer-conductance catheter-derived LV pressure-volume relationships. Contractility was assessed by preload recruitable stroke work (PRSW). The active and passive phases of LV relaxation were assessed by the time constant o isovolumic relaxation (tau) and the end-diastolic pressure-volume relationship (stiffness), respectively. RESULTS: PRSW decreased significantly and tau increased significantly from baseline at 1, 2, and 3 h after cardiac lymphatic obstruction (n = 8), but stiffness did not change. Cardiac lymphatic obstruction had similar effects on LV function in a group of autonomically blocked dogs (n = 5). Left ventricular function did not change in sham treated controls (n = 8). Cardiac lymphatic obstruction induced a significant increase in LV wet/dry weight ratios (3.58 +/- 0.01) when compared to the control group (3.53 +/- 0.02). Histopathology of the myocardium in the lymphatic obstruction groups revealed significant lymphangiectasis and increased interstitial spacing when compared to controls. CONCLUSIONS: Acute cardiac lymphatic obstruction depresses contractility and active relaxation and causes mild LV myocardial edema, but does not alter diastolic stiffness.

Acute Disease↗
PubMed1996

Effects of acid aspiration-induced lung injury on left ventricular function.

BACKGROUND: Acid aspiration-induced acute lung injury (AALI) leads to myocardial leukosequestration and edema in rats and hemodynamic depression in dogs, but the effects of AALI on left ventricular (LV) function have not been carefully studied. METHODS: We examined the effects of 0.1 N HCl administration into the lung on LV function, leukosequestration, and edema in pentobarbital-anesthetized, atropinized (n = 8), or autonomically blocked (n = 7) dogs. Saline solution was administered into the lungs of a control group of autonomically blocked dogs (n = 6). LV contractility was assessed by end-systolic elastance (EES) and preload recruitable stroke work (PRSW). Active relaxation was assessed by the time constant of LV pressure decline (tau). RESULTS: AALI resulted in significant (p < 0.05) decreases in mean arterial pressure and cardiac output and increases in pulmonary artery pressure and systemic vascular resistance in atropinized and autonomically blocked dogs but not in saline control group. In atropinized dogs tau did not change after injury, but EES and PRSW were increased significantly at 2 and 3 hours after injury, despite significant myeloperoxidase activity and extravascular fluid wet-dry weight ratios. EES, PRSW, and tau did not change in the autonomically blocked dogs in response to AALI or in the saline control group. CONCLUSIONS: We concluded that AALI results in a baroreflex mediated enhancement of LV contractility in dogs, despite mild myocardial leukosequestration and edema formation.

Acid-Base Equilibrium↗
PubMed1996

Acute transient coronary sinus hypertension impairs left ventricular function and induces myocardial edema.

This study was performed to evaluate the direct and indirect effects of acute coronary sinus hypertension (CSH) on systolic and diastolic left ventricular (LV) function. Coronary sinus pressure was elevated to 25 mmHg for 3 h in eight pentobarbital-anesthetized dogs and then relieved. LV contractility was assessed by preload recruitable stroke work (PRSW) and end-systolic elastance (Ees). Diastolic function was assessed by the time constant of isovolumic relaxation (tau) and the end-diastolic pressure volume relationship (EDPVR). PRSW and Ees decreased progressively, and tau and the slope of the EDPVR increased progressively with CSH. These changes persisted after relief of CSH. beta-Adrenergic and cholinergic receptor blockade, performed in six dogs, did not alter the effects of CSH on systolic or diastolic function. The LV wet-to-dry weight ratios of the groups with CSH were significantly greater than those of a control group without CSH. We conclude that CSH results in changes in the left ventricle that depress contractility, prolong active relaxation, and increase diastolic stiffness. The dysfunction was not the direct effect of CSH or autonomic reflex activation, but may have been induced by fluid accumulation within the interstitium.

Animals↗
PubMed1986

The USA's bicentennial census: new directions for methodology in 1990.

"Planning is under way for the U.S.A. bicentennial census in 1990. The U.S. Census Bureau sponsored a study panel under the U.S. Committee on National Statistics to consider key aspects of methodology for the census and to recommend priority areas for research and testing. The recommendations of the Panel on Decennial Census Methodology, which are summarized in this paper, cover four main topics: adjustment of the census counts for coverage errors, methods of coverage evaluation, uses of sampling in obtaining the count, and uses of administrative records in improving the quality of selected content items."

Americas↗
PubMed1984

The meaning of touch in care practice.

76 respondents were asked to categorise 28 specified examples of touching within health care. Broad agreement was found across the sample group as a whole, in its application of 8 of the 10 categories offered by the researchers. The need for alternative or additional categories and the occasional differences between responses of professional groups are discussed.

Female↗
PubMed1982

Inferences from alarming events.

An extreme event, such as a nuclear accident, an earthquake, a cluster of adverse reactions to a particular drug, or excessive breakdowns of some class of equipment, frequently focuses attention for the first time on an important issue. By then, however, data on the incidence and magnitudes of relevant past events may be unavailable or too costly to reconstruct. Using a simple probability model, we derive methods for drawing statistical inferences based only on the magnitude of the first event noticed and the amount of exposure before this event occurred. We assume that an event is noticed only when its magnitude exceeds some threshold, and we develop methods of inference that are valid even when this threshold is unknown. One tempting but incorrect approach is to treat the magnitude of the observed event as if it were the threshold, forgetting that smaller magnitudes might have been noticed as well. The biases that arise when this mistake is made turn out to be substantial; risks can easily be overstated by a factor of 3.

Disasters↗