Forced Bonhoeffer-van der Pol oscillator in its excited mode.
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Journal Article↗
Biomedical subjects
M Friedman
Publications and source records attributed to M Friedman.
Trends in medical education.
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Ambulatory Care↗
Basic FGF enhances endothelium-dependent relaxation of the collateral-perfused coronary microcirculation.
The effect of chronic, periadventitial administration of basic (b) fibroblast growth factor (FGF) on endothelial dysfunction in the collateral-dependent and normally perfused coronary microcirculation was examined. Ameroid constrictors were placed on the proximal left circumflex coronary artery (LCX) in 23 pigs. In 11 pigs, bFGF was released from calcium alginate microcapsules into the perivascular space of the proximal left anterior descending coronary artery (LAD) and LCX. After 5-8 wk, coronary arterial microvessels (80-170 microns) were studied in a pressurized (40 mmHg) no-flow state with video microscopy. Receptor-mediated endothelium-dependent relaxations to ADP and serotonin were reduced while contraction to acetylcholine was enhanced in the collateral-dependent LCX microvessels of non-bFGF-treated control hearts. Relaxation of vessels to the non-receptor-mediated, endothelium-dependent agent A-23187; endothelium-independent relaxation to nitroprusside; and contraction to KCl were similar in all groups. Chronic treatment with bFGF normalized responses to ADP, serotonin, and acetylcholine in the collateral-dependent LCX region but had no effect on the responses of vessels in the normally perfused LAD region. Arteriolar density in the collateral-perfused LCX region of bFGF-treated hearts was markedly increased (4-fold compared with that in untreated hearts, suggesting a link between the angiogenic effect of bFGF and its action on endothelial preservation. Thus the periadventitial, sustained delivery of bFGF preserves receptor-mediated, endothelium-dependent responses in the collateral-dependent LCX region but has no effect on responses of microvessels in the normally perfused LAD region or on non-receptor-mediated endothelium-dependent relaxation.
15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
Adrenergic regulation of coronary microcirculation after extracorporeal circulation and crystalloid cardioplegia.
The purpose of the present study was to examine whether adrenoceptor-mediated responses of porcine coronary resistance arteries are affected by cardioplegic arrest under conditions of extracorporeal circulation (cardiopulmonary bypass; CPB). Pigs were placed on CPB. The hearts were arrested with a cold hyperkalemic crystalloid cardioplegic solution for 1 h, then were reperfused for 1 h. In vivo and in vitro beta-adrenoceptor-mediated responses were compared before CPB and 2 min and 1 h after initiation of reperfusion. In vitro responses were studied in a pressurized no-flow state with video microscopy. Isoproterenol (0.02 micrograms.kg-1.min-1, intracoronary) increased coronary blood flow by 100 +/- 32% (P < 0.001) before CPB and cardioplegic arrest, 17 +/- 7% 2 min postcardioplegia (P < 0.01), and 71 +/- 9 (P < 0.001) after 1 h of reperfusion. Relaxation of precontracted microvessels (90-180 micron) to isoproterenol, NaF, forskolin, and adenosine was reduced after cardioplegic arrest (all P < 0.001). After 1 h of postcardiolegia-reperfusion, relaxation responses to forskolin and adenosine were completely restored, whereas the responses to isoproterenol (P < 0.05) and NaF (P < 0.10) were only partially recovered. Cardioplegic arrest and postcardioplegia-reperfusion blunted the alpha 2-adrenoceptor-mediated endothelium-dependent relaxation to clonidine (P < 0.001) but did not affect the minimal (< 4%) contractile response to the alpha 1-adrenoceptor agonist phenylephrine or the relaxation to nitroprusside. These results show that hyperkalemic cardioplegia results in the generalized defect in the beta-adrenoceptor-GS protein-adenylate cyclase pathway, which is significantly restored after reperfusion.
Adenosine↗
Basic fibroblast growth factor improves myocardial function in chronically ischemic porcine hearts.
The effect of basic fibroblast growth factor (bFGF) administration on regional myocardial function and blood flow in chronically ischemic hearts was studied in 26 pigs instrumented with proximal circumflex coronary artery (LCX) ameroid constrictors. In 13 animals bFGF was administered extraluminally to the proximal left anterior descending (LAD) and LCX arteries with heparin-alginate beads and 13 other animal served as controls. bFGF-treated pigs showed a fourfold reduction in left ventricular infarct size compared to untreated controls (infarct size: 1.2 +/- 0.4% vs. 5.1 +/- 1.3% of LV mass, mean +/- SEM, P < 0.05). Percent fractional shortening (% FS) in the LCX area at rest was reduced compared with the LAD region in both bFGF and control pigs. However, there was better recovery in the LCX area after rapid pacing in bFGF-treated pigs (% FSLCX/% FSLAD, 22.9 +/- 7.3%-->30.5 +/- 8.5%, P < 0.05 vs. prepacing) than in controls (16.0 +/- 7.8%-->14.3 +/- 7.0%, P = NS). Furthermore, LV end-diastolic pressure rise with rapid pacing was less in bFGF-treated than control pigs (pre-pacing; pacing; post-pacing, 10 +/- 1; 17 +/- 3; 11 +/- 1* mmHg vs 10 +/- 1; 24 +/- 4; 15 +/- 1 mmHg, *P < 0.05 vs. control). Coronary blood flow in the LCX territory (normalized for LAD flow) was also better during pacing in bFGF-treated pigs than in controls. Thus, periadventitial administration of bFGF in a gradual coronary occlusion model in pigs results in improvement of coronary flow and reduction in infarct size in the compromised territory as well as in prevention of pacing-induced hemodynamic deterioration.
Animals↗
Safety and tolerability of the implantable recurrent laryngeal nerve stimulator.
The recurrent laryngeal nerve (RLN) stimulator has been implanted on a limited basis since 1988 for control of spasmodic dysphonia. A similar vagus nerve stimulator has been implanted in a larger series of patients to control epilepsy. The safety and tolerability of these two stimulators were evaluated. In 113 patients implanted with the vagus nerve stimulator, the complication rate was 0.9%. All patients were monitored for vital signs, electrocardiographic changes, and adverse effects. The absence of changes in vital signs and electrocardiograms during vagal stimulation establishes the safety of this treatment. Since placement of the electrode around the vagus nerve is an easier surgical technique than placement deep to the RLN, it seems reasonable to change the technique to implant the stimulator on the vagus in patients with spasmodic dysphonia.
Electric Stimulation Therapy↗
Hemodynamic compromise secondary to a mediastinal bronchogenic cyst.
Bronchogenic cysts are not commonly the cause of severe symptoms, and often present only as an abnormality on chest roentgenogram. We report an unusual patient with a mediastinal bronchogenic cyst associated with rapid hemodynamic deterioration secondary to compression of vital structures.
Adult↗
CT of small-bowel obstruction: value in establishing the diagnosis and determining the degree and cause.
OBJECTIVE: The early diagnosis of small-bowel obstruction is critical in preventing complications, particularly strangulation. Traditionally, the clinical diagnosis of small-bowel obstruction has depended on plain film confirmation. Unfortunately, findings on the plain film may not be confirmatory in 20-52% of cases. The purpose of this study was to determine whether CT is superior to the traditional clinical-radiographic evaluation in prospectively establishing the diagnosis, severity, and cause in cases of suspected obstruction of the small bowel and to see what impact this information might have on treatment, costs, and the need for additional gastrointestinal contrast studies. SUBJECTS AND METHODS: Physicians from three surgical services referred all patients with suspected small-bowel obstruction for plain film and CT evaluation. Eight-five patients were evaluated on 90 occasions during an 11-month period. Obstruction was classified on the basis of clinical and plain film findings as absent, indeterminate, or present (partial or complete). CT scans were obtained in all patients and were interpreted and graded without knowledge of the clinical-radiographic classification. The results of gastrointestinal contrast studies (barium enema, small-bowel series, and enteroclysis) performed in 21 cases were also compared. The gold standard for the diagnosis was surgical findings in 61 cases and clinical course in 29 cases. RESULTS: On the basis of the combined clinical-radiographic findings, the diagnosis was complete obstruction in 21 of 46 cases (sensitivity, 46%; confidence interval (CI), 32-60%). When CT was used, the diagnosis was established in all 46 cases (sensitivity, 100%; CI, 86-100%). In the 25 cases in which the traditional evaluation failed, the early CT diagnosis of complete obstruction prevented a 12-72 hr delay in surgery with its attendant increased morbidity, mortality, and costs. On the basis of the combined clinical-radiographic findings, partial obstruction of the small bowel was diagnosed in six of 20 cases (sensitivity, 30%), whereas all cases were detected with CT. False-positive CT findings for complete obstruction of the small bowel occurred in three cases of paralytic ileus (one each due to small-bowel infarction, lower lobe pneumonia, and peritonitis due to rupture of the urinary bladder). One case of colonic obstruction due to carcinoma in the hepatic flexure was mistakenly diagnosed as partial obstruction of the small bowel. The clinical and plain film evaluation was never precise enough to provide the exact location or cause of small-bowel obstruction. Gastrointestinal contrast studies provided additional useful information regarding colonic abnormalities (four cases), functional grading of partial obstruction of the small bowel (six cases), and exclusion of a false-positive CT diagnosis of complete obstruction in a case of reflex ileus. CONCLUSION: CT is sensitive for diagnosing complete obstruction of the small bowel and for determining the location and cause of obstruction. In comparison, the traditional clinical and plain film evaluation is relatively insensitive. CT should be used when the results of clinical and plain film evaluation are inconclusive. Gastrointestinal contrast studies play an important diagnostic role in partial obstruction of the small bowel and in colonic obstruction with predominant small-bowel dilatation.
Humans↗
Parameters of pulmonary injury after total or partial cardiopulmonary bypass.
BACKGROUND: We have established that thromboxane B2 (TX) blood levels increase across the pulmonary circulation after total cardiopulmonary bypass (CPB) but not after partial CPB. In the present study, we used the same model and examined the parameters of pulmonary injury after total or partial CPB. METHODS AND RESULTS: Fourteen anesthetized sheep were placed on total CPB (n = 7), without ventilation and with occlusion of the pulmonary artery, or partial CPB (n = 7), with ventilation and an open pulmonary artery. After 90 minutes, the sheep were separated from CPB, and the pulmonary artery was perfused normally. After 30 minutes, we elevated left atrial pressure in all sheep. Plasma TX, plasma leukotriene B4, platelet counts, white blood cell counts, and plasma protein concentration were measured before CPB and every 15 minutes after CPB for 1 hour. The right and left atrial blood samples were obtained simultaneously. Pulmonary arterial pressure, left atrial pressure, and pulmonary arterial flow were measured. Pulmonary vascular resistance (PVR) was calculated for 30 minutes after CPB. Lung lymph protein, TX, leukotriene B4, and flow were measured before CPB and every 30 minutes after CPB for 1 hour. Pulmonary biopsies and bronchoalveolar lavage fluid were obtained before CPB and at the end of the experiment. After total CPB, levels of TX across the pulmonary circulation increased significantly, but leukotriene B4 remained constant. Platelets and white blood cells were consumed across the pulmonary circuit after total CPB but not after partial CPB. PVR increased by 170%, lymph flow increased by 233%, lung water content increased by 15%, and the ratio of lymph to plasma protein decreased by 20% after total CPB, but similar changes did not occur after partial CPB. CONCLUSIONS: During total CPB, the lungs are totally dependent on oxygen supply provided by nonpulsatile bronchial arterial flow. Lung injury seen with restoration of pulmonary artery flow and ventilation may be the result of an inflammatory response associated with TX elevation after a period of relative pulmonary ischemia. Pulmonary injury was not seen after less severe pulmonary arterial flow deprivation, with maintenance of ventilation (partial CPB). Although the specific cause is undetermined from these data, the occurrence of elevated TX levels and lung damage after total CPB is clearly established.
Animals↗
Pulmonary microvascular responses to protamine and histamine. Effects of cardiopulmonary bypass.
Total cardiopulmonary bypass with associated reduced pulmonary blood flow causes significant alterations of endothelium-dependent pulmonary microvascular responses after resumption of normal perfusion. To determine if this change in pulmonary vascular reactivity may influence the responses of pulmonary arterioles to protamine and histamine, we examined isolated pulmonary microvessels after cardiopulmonary bypass. Sheep were heparinized, cannulated, and placed on either total bypass without ventilation or partial bypass (70% of baseline pulmonary arterial flow) with continued ventilation. After 90 minutes, sheep were separated from cardiopulmonary bypass and the lungs were perfused normally for 60 minutes. Vessels from noninstrumented sheep were used as controls. Peripheral pulmonary arterioles (90 to 190 microns) were cannulated, pressurized (20 mm Hg) in a no-flow state, and examined with video microscopy. After precontraction of vessels with the thromboxane A2 analog U46619 by 18% to 25% of the baseline diameter, vasoactive agents were applied. Protamine sulfate, histamine, heparin, and the protamine-heparin complex caused significant dose-dependent relaxations of control pulmonary microvessels. These relaxation responses were substantially reduced or converted to contractile responses in endothelium-denuded vessels, which suggests that these relaxations are mediated through endothelium-dependent mechanisms. After partial bypass, responses to protamine and histamine were slightly reduced compared with the respective responses of control vessels, whereas the relaxation to protamine-heparin complex was not significantly altered. After total bypass, relaxation responses to protamine and protamine-heparin complex were markedly reduced, whereas histamine induced contraction of pulmonary microvessels. Endothelium-independent relaxation to sodium nitroprusside was not affected by partial cardiopulmonary bypass and was slightly reduced after total bypass. A reduced direct vascular relaxation response to protamine and increased contractile response to histamine (or other humoral substances released during the systemic administration of protamine sulfate) may contribute to the elevation of pulmonary vascular resistance during infusion of protamine after cardiopulmonary bypass.
Animals↗
Patterns of care for younger women with breast cancer.
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Adult↗
First-pass ventricular ejection fraction using a single-crystal nuclear camera.
UNLABELLED: The purpose of the study was to evaluate the reliability of ejection fractions obtained from first-pass radionuclide ventriculography with a large field-of-view tomographic single-crystal gamma camera. METHODS: A SPECT camera had its electronics redesigned to improve counting efficiency and was equipped with an experimental ultra-high sensitivity collimator. Left ventricular ejection fraction (LVEF) was measured in 28 patients by 30 degrees RAO first-pass imaging and by "best septal view" LAO planar equilibrium radionuclide ventriculography on a conventional small field of view Anger camera. For 28 other patients, first-pass ejection fractions were compared to multicrystal gamma camera values. Visual analysis was performed to judge clinical acceptability of first-pass images for identification of wall-motion abnormalities. RESULTS: Linear regression analysis of first-pass against equilibrium ejection fraction demonstrated good correlation (r = 0.92; slope = 0.90; intercept = 3.8; s.e.e. = 6.4%). First-pass ejection fraction values also correlated linearly with multicrystal camera values for the left ventricle (r = 0.94; slope = 1.05; intercept = 1.3; s.e.e. = 5.3%). For a subgroup of 19 patients, single-crystal camera right ventricle ejection fraction demonstrated good correlation with multicrystal camera values (r = 0.82; slope = 1.15; intercept = 1.3; s.e.e. = 6.1%). Interobserver variability correlated as r = 0.99 for LVEF ejection fraction and r = 0.92 for RVEF. Chi-square analysis of single-crystal first-pass image visual scores versus those from the gated equilibrium acquisitions showed close agreement (p < 10(-8)). CONCLUSIONS: The evaluated camera/collimator system measured left and right ventricular ejection fraction accurately. Lung frame correction and dual regions were superior to paraventricular background correction and a fixed end-diastolic region.
Feasibility Studies↗
ECFMG assessment of clinical competence of graduates of foreign medical schools. Educational Commission for Foreign Medical Graduates.
OBJECTIVE: To develop an assessment of clinical competence of graduates of foreign medical schools and to determine the reliability and validity of the assessment and the feasibility of large-scale administration. DESIGN: The Educational Commission for Foreign Medical Graduates (ECFMG) clinical competence study included (1) clinical encounters with standardized patients to assess history taking, physical examination, and communication skills; (2) laser videodisk pictorials to assess identification and interpretation of diagnostic procedures; (3) written clinical vignettes to assess diagnosis and management skills; and (4) assessment of spoken English. A uniform method of operating the test centers and of training the standardized patients was developed. SETTING: Medical schools and their primary teaching hospitals and affiliated hospitals. PARTICIPANTS: Six hundred twenty-four first-year residents, of whom 525 are graduates of foreign medical schools. MAIN OUTCOME MEASURES: Scores, reliability coefficients, validity measures, feasibility of multisite administration, trends of scores over time, and acceptability by examinees. RESULTS: The ECFMG clinical competence assessment was conducted at four geographically separate test centers. Reliability coefficients were high (.85) for the integrated clinical encounter and were in a reasonable range (.71 to .82) for all test components. The assessment adds to the predictability of the residents' performance in the hospital over that of current ECFMG certification examinations. Test security was addressed by demonstrating no consistent pattern of change in scores over testing dates. Virtually all examinees thought the assessment was appropriate. Standardized patients were able to assess spoken English accurately. CONCLUSION: The feasibility of conducting a reliable and valid test of clinical competence for graduates of foreign medical schools was demonstrated for this test population.
Clinical Competence↗
Three-dimensional imaging for evaluation of head and neck tumors.
OBJECTIVE: To determine the usefulness of three-dimensional imaging in addition to computed tomography in presurgical examination of patients with head and neck tumors. DESIGN: Two-dimensional computed tomographic information from 31 patients with oral facial tumors was converted to three-dimensional images. SETTING: University teaching hospital. PATIENTS OR OTHER PARTICIPANTS: A consecutive sample of 31 patients with oral facial tumors. INTERVENTIONS: None. MAIN OUTCOME MEASURES: Improved treatment planning with the use of three-dimensional images used in conjunction with computed tomographic scans. RESULTS: The three-dimensional images from patients with minimal tumor invasion of bone or with massive soft-tissue tumors allowed easy appreciation of tumor dimensions, an important factor in treatment planning. In patients with small soft-tissue tumors with no evidence of bone involvement on two-dimensional scans, massive tumors with complete bone destruction, and recurrent tumors, the three-dimensional representations added little to the obvious presentation of the two-dimensional scans. CONCLUSIONS: Three-dimensional imaging is a useful adjunct to diagnosis and treatment planning in patients with minimal tumor invasion of bone or with massive soft-tissue tumors.
Color↗
Medical diagnosis of type A behavior.
The objective of this investigation was to develop a medically oriented examination (including a search for physical signs in addition to elicitation of symptoms) for the accurate diagnosis of type A and type B behaviors. Comprising the study were 99 post-myocardial infarction patients, 15 clinically well persons in whom clinical coronary heart disease subsequently developed, and 23 healthy type B subjects. All participants were subjected to a videotaped clinical examination during which, in addition to eliciting responses to questions, 14 possible physical or psychomotor signs (many of which are newly discovered) of type A behavior were also observed. Each physical sign and symptom was given an arbitrarily weighted score (according to its observed frequency of occurrence in previously studied and authenticated type A behavior). These total scores were then statistically analyzed to obtain a critical "diagnostic score" for the presence of type A behavior. The medically oriented videotaped clinical examination detected the presence of type A behavior in 97 of 99 (98%) successively examined postinfarction patients and in 14 of 15 (93%) subjects who were clinically well at the time of their videotaped clinical examination but who subsequently had clinical coronary heart disease. Conversely type A behavior was diagnosed by videotaped clinical examination in only 1 of 23 (4%) healthy men who previously had been found to exhibit type B behavior by prior diagnostic procedures.
Aged↗
Isolated congenital atresia of the left main coronary artery and atherosclerosis.
Successful surgical revascularization in an adult with isolated congenital atresia of the left main coronary artery with coexistent two-vessel atherosclerosis is described. This extremely rare anomaly must be differentiated from single right coronary artery and acquired occlusion of the left main coronary artery. Symptomatic myocardial ischemia in patients surviving to adulthood is an indication for surgical revascularization in them.
Coronary Artery Bypass↗
A prototype erodible mask delivery system for the excimer laser.
PURPOSE: The authors developed an erodible mask delivery system for the argon-fluoride 193-nm excimer laser, which offers the possibility of correcting hyperopia and astigmatism as well as myopia. METHOD: Masks were made of polymethylmethacrylate on a quartz window, with intended corrections for myopia and hyperopia of 2.5 and 5 diopters (D). Ablations using the mask and control ablations using an expanding diaphragm were performed in 30 eyes of 15 pigmented rabbits with an Excimed UV200 laser (Summit Technology, Inc, Waltham, MA). The rabbits were followed for 134 days with regular biomicroscopy and retinoscopic examination by two observers. RESULTS: Ablations with the mask to correct myopia were successful and produced stable corrections, although the higher-power mask produced undercorrections. Hyperopic masks produced paradoxic myopic corrections, possibly due to the lack of a transition zone at the edge of the mask. Corneas ablated with the mask had less sub-epithelial haze than those ablated with the diaphragm at all examinations. Results of histopathologic examination showed epithelial hyperplasia over the ablation zone in all eyes. Dichlorotriazinyl aminofluorescein collagen staining showed subepithelial new collagen in all eyes, but there was no relation between the depth of ablation at any point on the cornea and the amount of new collagen deposited there. CONCLUSIONS: Myopic ablations are feasible with the erodible mask, although additional calibration is needed. Hyperopic ablations were unsuccessful with the current design. Corneas ablated with the mask may be clearer than corneas ablated with the diaphragm, possibly due to a smoother ablated surface. Regression of effect after laser ablation in the rabbit model is likely due more to epithelial hyperplasia than to stromal remodeling.
Animals↗