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Biomedical subjects

D L Stone

Publications and source records attributed to D L Stone.

At least 73 records · Page 4Linked to original sources
PubMed1983

Coronary haemodynamic effects of nifedipine. Comparison with glyceryl trinitrate.

The coronary haemodynamic effects of nifedipine and glyceryl trinitrate were compared in 22 patients undergoing investigations for suspected coronary artery disease. Myocardial blood flow was estimated by the coronary sinus thermodilution technique. In sinus rhythm nifedipine increased mean coronary sinus flow from 135 ml/min to 152 ml/min, and reduced arterio-coronary sinus oxygen difference from 12.4 to 10.96 ml/100 ml without causing a significant change in coronary vascular resistance or in myocardial oxygen consumption. Glyceryl trinitrate reduced mean coronary sinus flow from 165 to 111 ml/min, myocardial oxygen consumption from 19.2 to 11.9 ml/min, and arterio-coronary sinus oxygen difference from 11.7 to 10.9 ml/100 ml. There was a rise in coronary vascular resistance from 54 355 to 74 364 dynes s cm-5. During atrial pacing nifedipine reduced the arterio-coronary sinus oxygen difference from 11.99 to 11.0 ml/100 ml but had no significant effect on the other variables measured. Glyceryl trinitrate caused a fall in mean coronary sinus flow from 207 ml/min to 168 ml/min; myocardial oxygen consumption fell from 24 ml/min to 18 ml/min, while coronary vascular resistance rose from 41 714 to 51 234 dynes s cm-5. Direct comparison of the two drugs showed a significant difference in effects on coronary sinus flow and coronary vascular resistance in sinus rhythm. Both drugs appeared effective in relieving ischaemia as judged by a reduction of the incidence of pacing induced angina and an improvement in lactate status.

Blood Pressure↗
PubMed1982

Combined exercise radionuclide and hemodynamic evaluation of left ventricular aneurysmectomy.

Twelve patients were studied by rest and exercise radionuclide ventriculography following left ventricular aneurysmectomy (LVA). Left ventricular filling pressure (LVFP) was also measured. Nine patients had been studied pre-LVA at rest and exercise before and after isosorbide dinitrate (ISDN). Resting ejection fraction (LVEF) improved after LVA (p less than 0.25), but exercise LVEF did not. End-diastolic volume (EDV) and resting LVFP also fell after LVA (p less than 0.25 for EDV, p less than 0.05 for LVFP) and although exercise LVFP fell (p less than 0.02), the values were abnormal in all patients. Ejection fraction of contractile segment (EFCS) from the resting radionuclide study pre-LVA was related to resting LVEF post-LVA (r = 0.71 p less than 0.02), although postoperative LVEF could not be predicted from preoperative EFCS in individual patients. Deterioration in LVEF and LVFP from rest to exercise post-LVA occurred both in patients with single-vessel occlusion and in those with multivessel coronary disease, irrespective of whether or not revascularization had been performed. Thus LVA is effective in improving resting ventricular function; exercise performance may remain abnormal even in patients without residual coronary disease.

Adult↗
PubMed1982

Factorial phase imaging: a new concept in the analysis of first-pass cardiac studies.

A method is described which offers an alternative to conventional Fourier phase/amplitude imaging for analysing representative LV cycles obtained from first-pass cardiac studies. The method involves applying factor analysis to the data and producing functional images of the first two factor loadings after polar transformation. The method corrects for cycle asymmetries which produce anomalies in the Fourier images. For 88 studies the method provides greater uniformity among normal phase images while retaining, or even enhancing, abnormalities. Small differences between amplitude images produced by the two methods do not appear to be important.

Fourier Analysis↗
PubMed1982

Patient noncompliance with postvasectomy semen examination protocol.

This study determined the degree of patient compliance with postvasectomy semen examination protocol for verbal instructions as compared with verbal augmented by written instructions. The addition of written instructions did not improve patient compliance, and for a significant majority of patients (68 to 76 percent) there was no laboratory verification of the effectiveness of the vasectomy procedure. Results of the study raise serious concerns about physician reliance on patient compliance for postvasectomy semen examination protocol as assurance of successful vasectomy. When the potential for fertility among vasectomized men is uncertain, the complication of an unwanted pregnancy will fall on the woman. Educating physicians in the problems and strategies for gaining patient compliance is as essential as education in competent surgical technique.

Family Practice↗
PubMed1979

Cardiac emission tomography in patients using 201thallium. A new technique for perfusion scintigraphy.

The distribution of 201thallium (Tl) in the myocardium has been studied by the new technique of emission tomography, and compared with standard gamma camera images in 5 patients. Tomographic imaging was carried out using a dual-detector scanner operated under the single-photon technique. Initial results have been promising, with visualisation of resting perfusion defects in patients with recent infarction and those with ventricular aneurysms. Emission tomography has also been performed at exercise, and has shown tracer deficits in the distribution of significant coronary stenoses. This new approach to myocardial perfusion scintigraphy may lead to improved sensitivity for detecting apical and inferior wall abnormalities by providing depth information not available from a conventional two-dimensional image.

Coronary Disease↗
PubMed1978

A computer generated index for the assessment of coronary angiography.

Mortality in patients with coronary artery disease is related to its severity. The commonly used classification of 1, 2 or 3 vessel disease is relatively insensitive. We have designed a new classification which takes into account site, severity and effect of multiple lesions in the coronary circulation. Data is recorded on Mark Sense computer cards and a coronary index (CI) obtained. We have collected data from 1100 patients and shown correlations of the index with clinical variables, ventricular function and in particular, mortality.

Angina Pectoris↗
PubMed1978

The no-show patient in the model family practice unit.

Appointment breaking by patients causes problems for the physician's office. Patients who neither keep nor cancel their appointments are often referred to as "no shows." Twenty variables were identified as potential predictors of no-show behavior. These predictors were applied to 291 Family Practice Center patients during a one-month study in April 1977. A discriminant function and multiple regression procedure were utilized ascertain the predictability of the selected variables. Predictive accuracy of the variables was 67.4 percent compared to the presently utilized constant predictor technique, which is 73 percent accurate. Modification of appointment schedules based upon utilization of the variables studies as predictors of show/no-show behavior does not appear to be an effective strategy in the Family Practice Center of the Community Hospital of Sonoma County, Santa Rosa, due to the high proportion of patients who do, in fact, show. In clinics with lower show rates, the technique may prove to be an effective strategy.

Appointments and Schedules↗
PubMed1977

Regeneration of corneal epithelial basement membrane following thermal cauterization.

Thermal cauterization of the corneas of nine rhesus monkeys was performed by multiple thermokeratophore applications at temperatures of 90 degrees or 120 degrees C. Significant clinical observations included the resteepening of corneal curvature, delayed epithelial healing, stromal haze or scarring, and peripheral neovascularization. Reestablishment of tight adhesion of the regenerated epithelium to Bowman's layer required approximately 6 weeks. By transmission and scanning electron microscopy, the original basement membrane seemed relatively intact immediately following cauterization but disappeared within 1 week. The regeneration of new basement membrane complexes began at 1 week with the appearance of short discontinuous segments of basement material with hemidesmosomes and similarly required approximately 6 weeks for complete restoration.

Animals↗
PubMed1976

X-linked ocular albinism. An oculocutaneous macromelanosomal disorder.

Three unrelated kindreds with the Nettleship-Falls type of X-linked ocular albinism were studied. Postmortem examination of the eyes of an affected man revealed the presence of macromelanosomes in the pigment epithelia. Skin biopsy specimens of this patient, seven other affected male, and nine carrier female kindred members revealed the presence of Fontana-positive and dopa oxidase-positive macromelanosomes within the epidermis and dermis. Although clinically this disorder has been considered to be a form of albinism confined to the eyes, these findings indicate that an unusual disturbance in melanosome production characterized by macromelanosome formation affects the skin and the eyes. Histopathologic study of the skin is a useful adjunct in the diagnosis of X-linked ocular albinism, both in the affected and the carrier states. Linkage studies confirmed the close association of the Xg blood group with this disorder.

Adult↗
PubMed1976

Corneal endothelial degeneration and fibrous proliferation after plana vitrectomy.

A 45-year-old woman with juvenile-onset diabetes had persistent corneal edema after a pars plana vitrectomy and lensectomy procedure. Phase contrast and electron microscopic observation of the patient's cornea revealed extreme attenuation of the endothelial cell layer and abnormal collagenous and basement membrane material interposed between Descemet's membrane and the endothelium. Endothelial fibrous proliferations in this case were consistent with the development of ultrastructurally identical fibrous proliferations in many other situations involving dysfunction of the corneal endothelium.

Basement Membrane↗
PubMed1976

Ultrastructure of keratoconus with healed hydrops.

The corneas of three patients with keratoconus were examined by light and electron microscopy within approximately four months after onset of severe hydrops. The rupture and detachment of Descemet's membrane resulted in formation of extensive ledges. New endothelium completely resurfaced the exposed posterior stroma and the corresponding anterior aspect of the ledges. The endothelium also regenerated considerable basement membrane. In one case, clustered endothelium near the free end of the ledge appeared to have undergone fibrous metaplasia with secretion of extensive fibrillar and basement membrane material.

Adolescent↗
PubMed1976

Congenital central corneal leukoma (Peters' anomaly).

Corneal buttons from three patients with congenital central corneal leukoma (Peters' anomaly) were examined by light and electron microscopy. All cases exhibited a central absence of Bowman's membrane and iris synechiae to the periphery of the leukoma. In the first patient, extensive keratolenticular adhesion with retrocorneal fibrous tissue filling the central defect of endothelium and Descemet's membrane implicated late anterior displacement of the normally developed lens as the cause of secondary endothelial degeneration. In the second patient, attenuated endothelium and abnormally composed Descemet's membrane indicated primary dysgenesis of the endothelium. In the third patient, the extensive defect of posterior stroma with anterior stromal disorganization and endothelial metaplasia suggested dysgenesis of both the keratocytic and endothelial mesoderm. Thus, although no unified pathogenic mechanism was consistently applicable, either primary or secondary dysgenesis of the corneal mesoderm must be responsible.

Child, Preschool↗
PubMed1975

Candida endocarditis treated with a combination of antifungal chemotherapy and aortic valve replacement.

A case of Candida albicans endocarditis is described in which treatment with 5-fluorocytosine was started after aortic valve replacement, but relapse followed discontinuance of treatment. At a second operation the aortic valve was replaced under 5-fluorocytosine cover and treatment was continued with both 5-fluorocytosine and amphotericin-B. No resistance to 5-fluorocytosine developed, and the candida infection was eradicated. The patient is well 22 months after his operation.

Amphotericin B↗