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Biomedical subjects

B S Lewis

Publications and source records attributed to B S Lewis.

At least 91 records · Page 5Linked to original sources
PubMed1991

Small bowel enteroscopy and intraoperative enteroscopy for obscure gastrointestinal bleeding.

Intraoperative endoscopy (IOE) is accepted as the ultimate diagnostic procedure for completely evaluating the small bowel in patients with obscure gastrointestinal (GI) bleeding. Small bowel enteroscopy (SBE) has been reported useful in the nonsurgical evaluation of the small intestine in these patients, but findings may be limited because of incomplete small bowel intubation and a lack of tip deflection. Twenty-three patients underwent 25 SBE exams and subsequently had 25 IOE exams during surgical exploration for continued bleeding. Patients' bleeding histories averaged 2 yr, with an average transfusion requirement of 27 units. Findings on IOE were the same as with SBE in 17/22 (77%) of examinations. We conclude that SBE and IOE are comparable in depth of insertion and ability to detect small vascular ectasias. Both procedures missed pathology due to limited visibility and the evanescent nature of ectasias. Long-term success in abolishing bleeding with these combined techniques can be expected in 55% of these patients. SBE should precede surgery, since the finding of diffuse ectasias precludes any benefit from operative intervention.

Aged↗
PubMed1990

Failure of captopril to prevent nitrate tolerance in congestive heart failure secondary to coronary artery disease.

The possible role of angiotensin-converting enzyme inhibition in preventing or minimizing tolerance to intravenous nitroglycerin in severe congestive heart failure (CHF) was studied by quantitating the degree of tolerance in 12 patients receiving nitroglycerin (group 1) and in 9 patients (group 2) receiving nitroglycerin and concurrent treatment with captopril (60 +/- 29 mg/day). At peak effect, nitroglycerin produced almost identical hemodynamic changes in both groups, with significant decreases in right atrial and pulmonary arterial wedge pressure, systolic blood pressure and systemic and pulmonary vascular resistances. Cardiac index increased. The extent of nitrate tolerance was calculated for each hemodynamic parameter as the percentage loss of the peak effect achieved by the drug. At 24 hours, 98 +/- 80% of the benefit achieved with respect to right atrial pressure was lost in group 1 and 61 +/- 74% in group 2 (group 1 vs 2, difference not significant). For pulmonary arterial wedge pressure, 51 +/- 31% (group 1) and 85 +/- 53% (group 2) (difference not significant) of the effect was lost, and for cardiac index, 53 +/- 58% (group 1) and 54 +/- 44% (group 2) (difference not significant). Tolerance was also almost identical regarding systolic blood pressure and systemic and pulmonary vascular resistance. Thus, the extent of tolerance to high-dose intravenous nitroglycerin in CHF was unaltered by administration of captopril, indicating that in clinical dosage, counter-regulatory neurohumoral mechanisms involving the renin-angiotensin system appear to be unimportant in its development.

Adult↗
PubMed1990

Nitrate tolerance in heart failure: differential venous, pulmonary and systemic arterial effects.

The hemodynamic profile of tolerance to intravenous nitroglycerin was studied in 9 patients with New York Heart Association Class III to IV congestive heart failure. After rapid dosage build-up to the maximal tolerated dose (decrease in pulmonary wedge pressure to 10 mm Hg or systolic blood pressure to 90 mm Hg), nitroglycerin (525 +/- 548 micrograms/min) was administered at a constant continuous intravenous infusion for a total of 24 hours. The extent of nitrate tolerance at 24 hours was calculated as the percentage loss of the benefit achieved at time of peak effect of nitroglycerin. Tolerance had a different time course and magnitude in the venous, arterial and pulmonary circulations. At 24 hours, right atrial pressure and pulmonary vascular resistance returned to control values in most patients, while 40 to 50% of the effect on systemic vascular resistance, cardiac index and pulmonary wedge pressure was maintained. These findings emphasize the importance of precise definitions in studies relating to nitrate tolerance.

Adult↗
PubMed1990

The effects of aminoguanidine on the glycation (non-enzymic glycosylation) of lens proteins.

Aminoguanidine is being studied as a possible drug to prevent diabetic complications, by blocking the reactive carbonyl group of the Amadori product formed by glycation (non-enzymic glycosylation) of proteins. Thus it prevents the later browning and cross-linking steps. In the present work we show that labelled aminoguanidine becomes bound to glycated lens proteins. We also show that aminoguanidine inhibits the first steps of glycation of lens proteins but has no effect on carbamylation, the reaction with cyanate. It appears, therefore, that aminoguanidine can prevent glycation as well as the browning reactions, and may do so not by acting on the proteins, as other putative anti-cataract drugs do, but by decreasing the concentration of the active aldehyde form of the sugars.

Animals↗
PubMed1990

Predicting late restenosis after coronary angioplasty by very early (12 to 24 h) thallium-201 scintigraphy: implications with regard to mechanisms of late coronary restenosis.

To examine whether late coronary restenosis may be predicted by abnormalities of myocardial perfusion in the early hours after successful percutaneous transluminal coronary angioplasty and to study in greater detail the mechanisms involved in the development of late coronary restenosis after angioplasty, a prospective study was undertaken in 90 consecutive patients. Thallium-201 scintigrams were recorded at rest and during the stress of atrial pacing, 12 to 24 h after angioplasty, and the results were related to the findings at angiography in 70 patients undergoing late cardiac catheterization. A reversible thallium-201 perfusion defect was found in 39 (38%) of 104 myocardial regions supplied by the dilated coronary vessel and identified a subset of patients at high risk of late (6 to 12 months) angiographic restenosis (sensitivity 77%, specificity 67%). In contrast, late coronary restenosis developed in only 7 (11%) of 65 vessels and in 5 (14%) of 37 patients with a nonischemic thallium-201 scintigram on day 1 (p less than 0.005). Multivariate logistic regression analysis of 14 possible preangioplasty and periangioplasty clinical and angiographic variables selected reversible perfusion defect on the thallium-201 scintigram on day 1 (p = 0.016) and immediate postangioplasty residual coronary narrowing (p = 0.004) as significant independent predictors of late restenosis, with younger patient age as an additional less powerful predictor (p less than 0.05). The findings have important implications regarding the pathogenesis of late coronary restenosis in patients undergoing successful angioplasty and they imply that in the majority of these patients pathophysiologic events in the early minutes and hours after angioplasty may determine the development of late restenosis.

Adult↗
PubMed1990

Intraoperative scintigraphy for active small intestinal bleeding.

Localizing active sites of bleeding within the small intestine remains a difficult task. Endoscopic, angiographic or scintigraphic studies may point to the small intestine as the site of blood loss, but at operation, without a palpable lesion, the exact site of bleeding remains elusive. Patients are managed at laparotomy with intraoperative endoscopy, angiography, multiple enterotomies, "blind" resections, or placement of an enterostomy. We describe two patients in whom intraoperative scintigraphy accurately identified active sites of bleeding in the small intestine when other modalities failed. Intraoperative scintigraphy is rapid, easy to perform and is an effective means of identifying active sites of bleeding within the small intestine.

Aged↗
PubMed1990

Blood pressure response to exercise in normotensive and hypertensive young men.

We attempted to determine the optimal cut-off value of blood pressure defining a hypertensive response to exercise testing in 90 asymptomatic Israeli candidates for flight training with casual resting blood pressure of 140/90 mm Hg or more, and 72 age-matched normotensive controls tested in the Israel Air Force Aeromedical Center. Exercise testing (Bruce protocol) was performed using a calibrated Quinton Treadmill and a Hewlett Packard 151711-A three-channel ECG recording system. Recordings were made at 3-min intervals. At 3 min of exercise 12/87 (14%) of the hypertensive subjects had a SBP of greater than or equal to 210, compared to only 1/71 (1%) of the control group (relative risk 14). At 12 min of exercise 27/51 (53%) of the hypertensives and 9/55 (16%) of the controls had similar elevations of SBP (relative risk 3.3). At 6 min of exercise 11/87 (13%) of hypertensives had SBP greater than or equal to 220, whereas none of the normal controls had SBPs elevated to that degree. We concluded that an increase in SBP to 210 mm Hg or more after 3 min or to 220 mm Hg after 6 min of exercise testing by the Bruce protocol best separates the hypertensive group from the control group. This occurs at the expense of sensitivity. Only appropriate longitudinal studies can compare the degree to which various definitions of the hypertensive response to exercise will predict future hypertension.

Adolescent↗
PubMed1989

Identifying patients at high risk for restenosis after percutaneous transluminal coronary angioplasty for unstable angina pectoris.

To study the determinants of late restenosis after percutaneous transluminal coronary angioplasty (PTCA) performed in patients with unstable angina pectoris, a prospective study was undertaken in 90 patients. Primary PTCA success was achieved in 84 (93%) patients, dilating 116 of 118 coronary narrowings (1.4/patient), while major complications during PTCA occurred in only 1 patient (1 death). Eighty-two patients (114 dilated arteries) were followed for 25 +/- 11 months: 68 (83%) were in New York Heart Association functional class I or II, 11 (13%) in class III, and there were 3 deaths. Late restenosis was found in 16 (25%) of 65 lesions (29% of 49 patients) studied by angiography 9 +/- 7 months after PTCA. Restenosis was more frequent in left anterior descending coronary artery lesions (p = 0.07) and in those which at the time of PTCA had multiple irregularities (67 vs 14%, odds ratio 12.5, p = 0.002), decreased coronary perfusion (Thrombolysis in Myocardial Infarction grade less than 3) (50 vs 15%, odds ratio 5.7, p = 0.02) or intraluminal thrombus (67 vs 19%, odds ratio 8.7, difference not significant). Multiple irregularities (p = 0.003) and decreased flow (p = 0.02) remained independent predictors of restenosis (goodness of fit 0.88) after adjustment for 12 pre- and peri-PTCA clinical and angiographic variables by logistic regression analysis. These data underline the feasibility of early revascularization by PTCA in patients with unstable angina pectoris. Careful follow-up should be instituted in patients with multiple irregular lesions, decreased coronary perfusion or intraluminal thrombus at the time of PTCA. In such patients, late restenosis may be the rule rather than the exception.

Adult↗
PubMed1989

[Percutaneous transluminal coronary angioplasty after coronary artery bypass].

Anginal syndrome may recur early of several years after coronary artery bypass surgery (CABS), and may be due to narrowing of a bypass graft, progression of pre-existing coronary artery lesions, or the appearance of new lesions. Repeat CABS is associated with considerable morbidity and mortality. We therefore performed percutaneous transluminal angioplasty (PTCA) in saphenous or internal mammary bypass grafts or native coronary arteries in 23 patients after CABS. We successfully dilated 35 of 37 lesions (95%) present in 33 of 35 vessels (94%) of 21 of 23 patients (91%). The mean vessel narrowing decreased from 86 +/- 22% to 13 +/- 19% (p less than 0.001) and in all 21 patients with angiographic evidence of success functional capacity improved. Single vein grafts were successfully dilated in 9 patients. None developed acute myocardial infarction or needed emergency surgery, but 1 had a cerebral embolism. PTCA is effective therapy for recurrent angina after CABS, and in many patients is preferable to another operation.

Angina Pectoris↗
PubMed1989

Pulmonary function in preterm infants following treatment with intravenous indomethacin.

Pulmonary function tests, including measurements of arterial blood gas levels, total pulmonary compliance, and arterial-alveolar oxygen ratios, were performed in 38 ventilator-dependent preterm infants with respiratory distress syndrome who weighed less than 1500 g at birth. Twenty-seven had a physiologically significant patent ductus arteriosus (PDA). Twelve were assigned at random to receive three doses of intravenous indomethacin, 0.2 mg/kg per dose, on the fourth day of life. This treatment resulted in ductal closure in seven infants by the seventh day of life. Another concurrently observed group of 15 infants with PDA received no indomethacin. A third group of 11 infants lacked evidence of a PDA. Pulmonary function in the infants who received indomethacin did not differ significantly from that in the other two groups.

Ductus Arteriosus, Patent↗
PubMed1989

Effect of isosorbide dinitrate on cardiac output in severe cardiac failure: relation to initial hemodynamics, ventricular volume, and the preload reserve mechanism.

Isosorbide dinitrate (ISDN) improves the clinical and hemodynamic state of patients with heart failure, but may cause dizziness and syncope. To characterize patients in whom cardiac output falls with high-dose nitrate therapy and to examine further the pathophysiology of the fall in cardiac output in these patients, we studies the effect of sublingual ISDN on forward cardiac output in 14 patients with severe cardiac failure (New York Heart Association grades 3-4). We examined systolic and diastolic left ventricular (LV) function from pressure and volume analyses of LV function. After administration of 15 mg ISDN, cardiac output was either unaltered or increased in 7 patients (Group 1) (11 +/- 12%, mean +/- SD), and decreased in 7 (Group 2) (-13 +/- 10%) (Group 1 vs. 2, p less than 0.002). Initial systemic arterial pressure, LV ejection fraction, wedge and LV transmural filling pressures were similar in both groups, but Group 2 patients had a lower systemic vascular resistance (p = 0.07) and tended to have a larger initial LV end-diastolic volume and increased end-diastolic compliance; following ISDN the decrease in LV filling pressure and end-diastolic volume was larger and the product of the changes greater (p less than 0.02). Thus ISDN decreases filling pressure and improves forward cardiac output in some patients with congestive heart failure, but large doses may decrease cardiac output in a subset of patients who have a lower systemic vascular resistance and a larger more compliant ventricle, maintaining forward blood flow predominantly by a preload reserve mechanism.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1989

Mitral leaflet motion: age and implications for the diagnosis of mitral valve prolapse.

The extent of posterior mitral leaflet motion (PMLM) during systole in relation to age was studied in 300 asymptomatic men aged 18-42 years. PMLM of 4 mm or more on two-dimensional directed M-mode echocardiography was found in 8% (16/200) of subjects under age 35 years, but in only 2% (2/100) of those aged 35 years or more (p less than 0.05). On two-dimensional echocardiography, 16% (31/200) of men under 35 years old had PMLM greater than or equal to 0.40 mm2 compared with 1% (1/100) of those 35 years or more (p less than 0.001). The findings were not related to differences in left ventricular cavity dimensions or in the extent of systolic ventricular contraction. Body mass index (BMI) increased with age, but there was a significant and independent negative correlation of age with PMLM after controlling for BMI. The data are compatible with the hypothesis that the aging process is associated with decreased mobility of the mitral valve or annulus with lesser degrees of backward bowing or billowing of the leaflets during systole. Age should be taken into account in determining "normal" values for mitral leaflet motion.

Adolescent↗
PubMed1989

Systolic tricuspid leaflet prolapse in asymptomatic young men.

The degree of systolic movement of the tricuspid valve (TV) leaflets was measured in 100 consecutive apparently healthy men 18-20 years old at the time of maximum posterosuperior motion toward or into the right atrium. Backward bowing of greater than 0.20 mm2 of the anterior leaflet, and greater than 0.15 mm2 of either the posterior or septal leaflets beyond the plane of the tricuspid annulus was found in 5% or less of the cohort irrespective of the echocardiographic view in which it was recorded. The upper 5% of these young men had greater than 0.80 mm2 of backward bowing when the leaflet motion was summed from all three views. The anterior leaflet demonstrated more bowing than either the septal or posterior leaflets. The systolic TV prolapse area correlated highly with the degree of mitral leaflet prolapse (r = 0.654, p less than 0.001). We conclude that there is a wide continuous spectrum of tricuspid valve leaflet prolapse area in healthy young men. This quantitative approach may help standardize the echocardiographic evaluation of tricuspid leaflet motion.

Adolescent↗
PubMed1989

Effect of the second-generation calcium channel blocking drug nisoldipine on diastolic left ventricular dysfunction in heart failure.

The effect of intravenous nisoldipine (0.12 microgram/kg/min) on diastolic left ventricular (LV) dysfunction was studied from simultaneous hemodynamic and radionuclide measurements in 12 patients with New York Heart Association class II to IV cardiac failure. The initial LV filling fraction was low, the peak LV filling rate normalized for end-diastolic volume was decreased, and the pulmonary capillary wedge pressure (PCWP) was high and associated with clinical shortness of breath. Nisoldipine produced an increase in LV filling fraction from 36 +/- 17% to 43 +/- 20% (p = 0.003). The increase in filling took place in both early and late diastole: peak early filling rate (PFR) increased in 11 of the 12 patients (p = 0.02) and late diastolic filling rate (atrial [A] wave in eight of them (NS). When the determinants of these changes, were examined further, it was found that in the control state PFR was inversely related to LV end-systolic volume (r = 0.77), whereas the A wave was related in exponential fashion to PCWP (preload) (r = 0.79). Nisoldipine did not change the slope of these relationships, and it did not alter the end-diastolic pressure-volume relationship, implying that inherent myocardial relaxation and distensibility were unaltered by the drug. In summary, nisoldipine improved measurements of diastolic LV dysfunction in patients with cardiac failure. This study illustrates the importance of considering ventricular loading conditions when analyzing and interpreting measurements of diastolic ventricular dysfunction. The measured changes in diastolic LV function during infusion of nisoldipine appear to be due to alterations in ventricular loading conditions rather than to a direct myocardial effect of the drug.

Aged↗
PubMed1989

The hairy polyp: a benign teratoma of the colon.

A 76-year-old female presented with bright red rectal bleeding. Endoscopic evaluation revealed a polypoid lesion sprouting hair in the sigmoid colon. Histologically the resected polyp was composed of elements of all three germ layers, fulfilling the criteria for a teratoma. The differential diagnosis of this benign polyp and its significance are discussed.

Aged↗
PubMed1989

Alterations in serum immunoglobulin G subclasses in patients with ulcerative colitis and Crohn's disease.

We have examined the concentration of immunoglobulin G (IgG) subclass antibodies in the sera of 27 patients with ulcerative colitis and 21 patients with Crohn's disease as well as in 11 normal controls and 11 patients with systemic lupus erythematosus. In comparison with a control mean serum IgG1 concentration of 5173 micrograms/ml, patients with ulcerative colitis exhibited a significantly increased mean serum concentration of 7924 micrograms/ml (p less than 0.05), whereas patients with Crohn's disease had a near normal mean serum IgG1 level of 5898 micrograms/ml. In contrast, control sera had a mean IgG2 level of 2477 micrograms/ml and ulcerative colitis sera had a similar IgG2 level of 2269 micrograms/ml, whereas Crohn's disease sera had a significantly increased mean IgG2 level of 5111 micrograms/ml (p less than 0.05). Patients with systemic lupus erythematosus, like those with ulcerative colitis, had a markedly elevated serum IgG1 level of 15,594 micrograms/ml (p less than 0.001) without a significantly increased IgG2 serum level (3271 micrograms/ml). Neither ulcerative colitis nor Crohn's disease sera exhibited altered levels of IgG3 or IgG4. These data show that alterations in IgG subclass concentrations occur in the sera of patients with active, untreated inflammatory bowel disease, similar to the previously noted changes in the IgG subclasses secreted by lymphocytes from involved inflammatory bowel disease intestinal specimens.

Adult↗