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Biomedical subjects

M D Feldman

Publications and source records attributed to M D Feldman.

At least 37 records · Page 2Linked to original sources
PubMed1999

Chinese and U.S. internists adhere to different ethical standards.

OBJECTIVE: To determine whether internists in the United States and China have different ideas and behaviors regarding informing patients of terminal diagnoses and HIV/AIDS, the role of the family in end-of-life decision making, and assisted suicide. DESIGN: Structured questionnaire of clinical vignettes followed by multiple choice questions. SETTING: University and community hospitals in San Francisco and Beijing, China. SUBJECTS: Forty practicing internists were interviewed, 20 in China and 20 in the United States. MEASUREMENTS AND MAIN RESULTS: Of the internists surveyed, 95% of the U.S. internists and none of the Chinese internists would inform a patient with cancer of her diagnosis. However, 100% of U.S. and 90% of Chinese internists would tell a terminally ill patient who had AIDS, rather than advanced cancer, about his diagnosis. When family members' wishes conflicted with a patient's preferences regarding chemotherapy of advanced cancer, Chinese internists were more likely to follow the family's preferences rather than the patient's preferences (65%) than were the U.S. internists (5%). Thirty percent of U.S. internists and 15% of Chinese internists agreed with a terminally ill patient's request for sufficient narcotics to end her life. CONCLUSIONS: We found significant differences in clinical ethical beliefs between internists in the United States and China, most evident in informing patients of a cancer diagnosis. In general, the Chinese physicians appeared to give far greater weight to family preferences in medical decision making than did the U.S. physicians.

Adult↗
PubMed1998

End-systolic pressure-dimension relationship of in situ mouse left ventricle.

The increasing popularity of genetically engineered mice in cardiovascular research has made it important to evaluate cardiac function in small animals. We have developed a system to enable simultaneous pressure-dimension analysis of the mouse left ventricle. The chest was opened under anesthesia, and a 1.4 F micromanometer catheter was inserted into the left ventricle through the apex. A pair of sonomicrometry crystals were attached to the anterior and posterior walls using tissue adhesive. Pressure and dimension were recorded simultaneously at baseline and after isoproterenol injection (1 micro g, intraperitoneally). The ascending aorta was occluded transiently to estimate the end-systolic pressure-dimension relationship (ESPDR), which was parameterized subsequently by the quadratic equation: Pes=C2 X (Des-D0)2+E0 X (Des-D0), where Pes is end-systolic pressure, Des is end-systolic dimension, D0 is the dimension axis intercept, E0 is the local slope at D0, and C2 is the curvilinearity coefficient. The maximum and minimum external dimensions at baseline were 5.82+/-0.50 (s.d.) mm and 5.49+/-0.46 mm with fractional shortening of 0.057+/-0.014 (n=12). The ESPDR was significantly curvilinear and increased convexity after isoproterenol injection (C2, -444+/-281 to -1113+/-780 mmHg/mm2, P<0. 05; E0, 536+/-175 to 889+/-276 mmHg/mm, P<0.001), while the dimension axis intercept remained relatively constant (D0, 5.39+/-0. 46 to 5.37+/-0.52 mm). In conclusion, the combination of miniature piezo-electric crystals and a micromanometer enables continuous measurement of pressure and dimension of in situ mouse left ventricle. This technology may be useful in evaluating the cardiac phenotype of genetically engineered mice.

Animals↗
PubMed1998

Factitious deafblindness: an imperceptible variant of factitious disorder.

We describe two women who, over a period of years, feigned the loss of both vision and hearing. Their principal motive appeared to be pursuit of the sick role, though each acquired disability payments as well. A face-saving intervention sharply reduced the alleged hearing deficits in one case; the other patient precipitously left treatment. A broad range of permutations of factitious disorder has been reported, but these appear to be the first published cases of factitious deafblindness.

Adult↗
PubMed1998

Direct myocardial effects of OPC-18790 in human heart failure: beneficial effects on contractile and diastolic function demonstrated by intracoronary infusion with pressure-volume analysis.

OBJECTIVES: We sought to determine the precise myocardial effects of OPC-18790 as demonstrated by intracoronary administration. BACKGROUND: Although previous studies have determined the cardiovascular effects of a novel intravenous inotrope, OPC-18790, the observed benefits on contractile and diastolic function may have been confounded by the marked changes in peripheral loading associated with this drug when given intravenously. METHODS: Eight heart failure patients received intracoronary OPC-18790 at 31.25 microg/min for 20 min, and then at 62.5 microg/min for another 20 min. Hemodynamic variables and pressure-volume indexes using the conductance catheter method were determined at baseline and then after the two doses. RESULTS: There were no significant effects on heart rate, cardiac output or loading conditions, including afterload as determined by systemic vascular resistance and arterial elastance (Ea) and preload as determined by end-diastolic volume (EDV). There were significant increases in end-systolic elastance (Ees) from 0.74+/-0.11 to 0.90+/-0.16 mm Hg/ml at 31.25 microg/min and to 137+/-0.33 mm Hg/ml at 62.5 microg/min (p < 0.05 by analysis of variance [ANOVA]). Diastolic function improved, as determined by the time constant for isovolumetric relaxation tau, which decreased significantly from baseline to 31.25 microg/min (94+/-9 to 79+/-9 ms, p < 0.05), and did not shorten further at 62.5 microg/min (78+/-8 ms, p=NS). There were significant decreases in right atrial pressure (9+/-1 to 7+/-1 mm Hg, p < 0.01 by ANOVA) and mean pulmonary artery wedge pressure (21+/-3 to 16+/-2 mm Hg, p < 0.05 by ANOVA). This fall in filling pressures was not accompanied by any change in EDV. Inspection of the diastolic portion of the pressure-volume curve confirmed a downward shift consistent with pericardial release in five of the eight patients. CONCLUSIONS: Intracoronary administration of OPC-18790 demonstrates that the direct myocardial effects of this agent include a modest increase in inotropy and improvement in diastolic function, both of which occur without increases in heart rate, indicating that this agent may be beneficial for the intravenous treatment of congestive heart failure.

Aged↗
PubMed1998

Micromechanical devices for intravascular drug delivery.

Microfabrication technology, more commonly applied to the manufacture of integrated circuits, can be used to build devices useful for mechanical delivery of drugs and genes. Microprobes fabricated using silicon micromachining have been used to deliver DNA into cells as an alternative to bombardment and microinjection. This idea can be extended to intravascular stents with integrated microprobes capable of piercing compressed plaque and delivering anti-restenosis therapies into coronary arteries. Preliminary experiments using filleted rabbit arteries have demonstrated transection of the internal elastic lamina. New nonplanar microfabrication technologies are necessary for creating practical devices with cylindrical symmetry; a promising possibility is to use microfabricated structures of anodic metal oxides.

Animals↗
PubMed1998

Estrogen acutely abolishes abnormal cold-induced coronary constriction in men.

BACKGROUND AND STUDY OBJECTIVE: Ambient cold exposure may induce myocardial ischemia by precipitating coronary artery constriction and a decrease in coronary blood flow. Estrogen has vasoactive properties that may prevent abnormal coronary constriction in a sex-independent manner. The purpose of this study is to determine whether estrogen acutely abolishes abnormal coronary responses to cold exposure in men. DESIGN: Randomized, double-blinded placebo-controlled clinical trial. SETTING: Cardiac catheterization laboratory. PATIENTS: Men referred for routine diagnostic coronary angiography who exhibit abnormal coronary artery constriction in response to a 90-s cold pressor test (CPT). INTERVENTION: Intravenous conjugated estrogens (1.25 mg) vs. placebo. MEASUREMENTS AND RESULTS: Rate-pressure product, coronary cross-sectional area (CSA), and coronary blood flow responses to the CPT were measured before and 15 min after intervention. In 12 men with CPT-induced coronary constriction who were assigned to estrogen, CPT induced a mean 21.8% decrease in coronary CSA (p < 0.01) and a nonsignificant change in coronary flow. After estrogen, the repeated CPT induced a 16.3% increase in CSA (p < 0.01) and a 54.9% increase in flow (p < 0.01). CSA and coronary flow responses to CPT were significantly different before and after estrogen (p < 0.01). In contrast, placebo was not associated with changes in CSA or coronary flow responses to CPT in eight men. CONCLUSIONS: In men, conjugated estrogens acutely abolish abnormal coronary constriction and improve coronary blood flow responses to an exogenous cold stimulus. These results suggest that estrogen favorably alters coronary vasoreactivity in men.

Aged↗
PubMed1997

Myocardial contrast echocardiography can be used to quantify intramyocardial blood volume: new insights into structural mechanisms of coronary autoregulation.

BACKGROUND: Changes in intramyocardial blood volume (IBV) mediate autoregulatory adaptations to coronary stenosis. This study investigated whether (1) myocardial contrast echocardiography (MCE) can quantify changes in IBV during coronary stenosis and (2) the relation between coronary resistance- and MCE-derived IBV could yield insight into structural mechanisms of IBV change. METHODS AND RESULTS: A circulating in vitro model with constant flow and varying volume was used to determine whether indicator dilution theory could be applied to MCE. Contrast echo was performed with albumin microbubbles, and time-intensity data were fit to a gamma-variate function. With six different volumes, bubble transit time was linearly related to volume (r=.91). To determine whether changes in IBV could be quantified in vivo, the left anterior descending coronary artery in 12 dogs was instrumented with a flow probe, occluder, and intracoronary pressure catheter, and non-flow-limiting stenoses were created. IBV was derived by use of coronary resistance measurements applied to models that assumed autoregulation to occur via vasodilatation or microvascular recruitment. MCE-IBV was calculated from microbubble transit rates. At constant flow, MCE and resistance IBV increased with stenosis. Although MCE and resistance IBV were linearly related, MCE overestimated IBV derived from the vasodilatation model and underestimated IBV calculated from the recruitment model. CONCLUSIONS: MCE can quantify autoregulatory increases in IBV that maintain resting myocardial perfusion. These data suggest that both microvessel vasodilatation and recruitment are dual mechanisms of IBV change. MCE thus may be a clinically useful technique for the detection and quantification of coronary artery disease at rest.

Animals↗
PubMed1997

Correlation of adenosine thallium 201 perfusion patterns with markers for inducible ischemia.

To determine the frequency of true myocardial ischemia caused by hemodynamic, metabolic, and regional functional abnormalities after intravenous adenosine infusion in patients with coronary artery disease, 13 patients--11 with coronary artery disease--received intravenous adenosine and thallium 201 during cardiac catheterization. Intracoronary adenosine levels increased by an average of 9.4-fold over baseline. Of the 11 patients, all had > or = 70% stenoses with a mean number of redistribution defects per patient of 3.3 +/- 0.7. Only two (18%) patients had new wall motion abnormalities detected by echocardiography during adenosine infusion. Pulmonary capillary wedge pressure did not significantly rise (13 +/- 7 to 17 +/- 8 mm Hg, p= NS). Lactate production occurred in two patients. Coronary sinus oxygen saturation levels rose from 29% +/- 6% to 68% +/- 8%, consistent with less myocardial oxygen extraction. Thus, despite a high prevalence of defects detected by 201Tl, the prevalence of true myocardial ischemia in patients with coronary artery disease undergoing pharmacologic stress imaging with intravenous adenosine is low. Perfusion defects induced by vasodilator stress are predominantly caused by heterogeneity of flow reserve rather than true ischemia.

Adenosine↗
PubMed1997

Concurrent factitious disorder and factitious disorder by proxy. Double jeopardy.

Two forms of medical dissimulation-factitious disorder and factitious disorder by proxy-present enormous challenges to clinicians accustomed to receiving valid symptom reports from their patients. The consequences of such "disease forgery" are heightened when a patient simultaneously engages in both forms of deception. We discuss a 34-year-old nurse who simulated or induced a panoply of physical and psychological ailments in both herself and her daughter. The staff's insistence on access to outside information sources proved indispensible in establishing both diagnoses, facilitating ongoing treatment for the patient and ensuring appropriate protection of the child.

Adult↗
PubMed1997

Arthroscopic excision of type II capitellar fractures.

Type II capitellar fractures are uncommon. The current treatment recommendation for these fractures is open excision. The major complication of open excision is loss of motion. Two cases of the previously unreported technique of arthroscopic excision are presented with a review of the literature. Arthroscopic excision of displaced type II capitellar fractures is a safe, effective technique that causes minimal soft tissue trauma, allows thorough inspection of the joint for additional occult injuries, and optimizes postoperative range of motion.

Adult↗
PubMed1997

An overview of HIV prevention in the United States.

Despite recent promising results with protease inhibitors and combinations of drugs in treating HIV-infected persons, a cure or vaccine for AIDS is unlikely within the next several years. Therefore, prevention remains the most realistic strategy for dealing with the HIV epidemic. However, HIV prevention efforts in the United States face enormous challenges. Translating knowledge about effective HIV prevention strategies into sound HIV prevention policy must be a priority. For example, AIDS prevention experts must dispel the myth that needle exchange programs for injection drug users encourage drug use. Such programs may, however, decrease the risk for HIV transmission. Another challenge is to implement effective sex education programs. It is well established that early sex education does not lead to promiscuity among young people; in fact, it may actually decrease overall sexual activity and decrease high-risk sexual activities. Finally, prevention programs must reach those most at risk. Surveillance data indicate that these include young gay men, Hispanic and African Americans, and the economically disadvantaged. Prevention policy too often is formed on the basis of opinion or anecdote rather than on the basis of science. Sound and strong science is needed to ensure that the best programs and policies can be put into place.

Adult↗
PubMed1997

Accuracy of the conductance catheter for measurement of ventricular volumes seen clinically: effects of electric field homogeneity and parallel conductance.

The conductance-volume method is an important clinical tool which allows the assessment of left ventricular function in vivo. However, the accuracy of this method is limited by the homogeneity of electric field the conductance catheter produces and the parallel conductance of surrounding structures. This paper examines these sources of error in volumes seen clinically. The characteristics of electric field within a chamber were examined using computer simulation. Nonconductive and conductive models were constructed and experimental measurements obtained using both single-field (SF) and dual-field (DF) excitation. Results from computer simulations and in vitro measurements were compared to validate the purposed theoretical model of conductance-volume method. The effects of field homogeneity and significance of parallel conductance in volume measurement were then determined. The results of this study show that DF provide a more accurate measure of intraventricular volume than SF, especially at larger volumes. However, both significantly underestimate true volume at larger volumes. In addition, the parallel conductance due to the chamber wall is significant at small volumes, but diminishes at larger volumes. Furthermore, the effect of parallel conductance beyond the chamber wall may be negligible. This study demonstrates the limitations in applying current conductance technology to patients with dilated hearts.

Animals↗