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Biomedical subjects

H C Smith

Publications and source records attributed to H C Smith.

At least 127 records · Page 7Linked to original sources
PubMed1985

Follow-up clinical results in patients undergoing percutaneous transluminal coronary angioplasty.

Complete follow-up data were obtained from 229 consecutive patients who underwent percutaneous transluminal coronary angioplasty (PTCA) between 1979 and 1982 (mean follow-up 14 months, range 6 to 37). Single-vessel disease was present in 143 and multivessel disease in 86. PTCA was successful in 153 patients (67%). Failure was followed initially by bypass surgery in 59 and by continued medical therapy in 17. After successful PTCA, 90% of patients were improved subjectively and 74% were asymptomatic at follow-up. After unsuccessful PTCA but prompt bypass, 90% were improved subjectively and 85% were asymptomatic. Among the 229 patients, 39 (17%) required an additional intervention because of angina during follow-up; 15 of these had repeat PTCA and 18 had bypass surgery. Among patients with successful PTCA, revascularization was complete in 77% and partial in 23%. The completeness of revascularization with PTCA had a significant impact on follow-up. The follow-up data of patients with successful single-vessel PTCA and of those with multivessel disease with complete revascularization were similar. When the patients with complete revascularization were compared with those with multivessel disease but incomplete revascularization, the follow-up data were characterized by a higher incidence of angina or need for bypass surgery in the latter group (63%) than in the former group (29%); those with incomplete revascularization also had a significantly reduced event-free survival.

Adult↗
PubMed1985

Continuous-wave Doppler echocardiographic assessment of severity of calcific aortic stenosis: a simultaneous Doppler-catheter correlative study in 100 adult patients.

Studies of the correlation of aortic valve gradient determined by continuous-wave Doppler echocardiography and that determined at catheterization have, to date, involved young patients and nonsimultaneous measurements. We therefore obtained simultaneous Doppler echocardiographic and catheter measurements of pressure gradient in 100 consecutive adults (mean age 69, range 50 to 89 years). In 63 patients pressure measurements were obtained with dual-catheter techniques and in 37 they were obtained by withdrawal of the catheter from the left ventricle to the ascending aorta. Forty-six of these patients also underwent an outpatient Doppler study 7 days or less before catheterization. The simultaneous pressure waveforms and Doppler spectral velocity profiles were digitized at 10 msec intervals and maximum, mean, and instantaneous gradients (mm Hg) were derived for each. The correlation between the Doppler-determined gradient and the simultaneously measured maximum catheter gradient was r = .92 (SEE = 15 mm Hg), that between the Doppler-determined and mean catheter gradient was r = .93 (SEE = 10 mm Hg), and that between the Doppler and peak-to-peak catheter gradient was r = .91 (SEE = 14). The correlation between the nonsimultaneously Doppler-determined gradient and the maximum gradient measured by catheter was not as strong (r = .79, SEE = 24). The continuous-wave Doppler echocardiographic velocity profile represents the instantaneous transaortic pressure gradient throughout the cardiac cycle. The best correlation with continuous-wave Doppler-determined gradient was obtained with maximum and mean gradients measured by catheter. Continuous-wave Doppler echocardiography can be used to reliably predict the pressure gradient in adults with calcific aortic stenosis.

Aged↗
PubMed1985

A reappraisal of the binding characteristics of human thyroxine-binding globulin for 3,5,3'-triiodothyronine and thyroxine.

The binding characteristics of T4 and T3 to dilute plasma were studied separately in five normal euthyroid subjects with normal levels of thyroxine-binding globulin (TBG). Scatchard analyses of these data revealed similar mean affinity constants for T4 [2.0 +/- 0.7 (SD) X 10(9) M-1] and T3 (2.0 +/- 0.7 X 10(9) M-1), but a 5-fold higher capacity for T4 (0.75 +/- 0.18 mol T4/mol TBG) than for T3 (0.14 +/- 0.06 mol T3/mol TBG). Similar results were obtained using various assay buffers, pH concentrations, or separation methods. This characteristic pattern of T4 and T3 binding was retained by thyroid hormone free plasma, with the only difference being a slight parallel shift to the left of the Scatchard plots for both T4 and T3. The calculated affinities (Ka) for T4 and T3 were 5.2 X 10(9) M-1 and 5.2 X 10(9) M-1, respectively. High affinity T4 and T3 binding was abolished in plasma selectively depleted of TBG, but was retained after selective depletion of either prealbumin or albumin. Highly purified TBG, prepared from normal serum, demonstrated binding characteristics for T3 and T4 similar to dilute plasma. Displacement of [125I]T4 from dilute plasma by unlabeled T3 or T4 revealed a binding potency of T3 relative to T4 of 9%. Binding affinities derived from analog displacement studies appear invalid as these calculations assume equal binding capacities of TBG for T4 and T3. It seems clear from these studies, that the binding characteristics of human TBG are inconsistent with a single competitive binding site for thyroid hormones.

Autoradiography↗
PubMed1985

The angiographic spectrum of coronary artery disease.

A wide spectrum of coronary arteriographic anatomic findings exists in patients presenting with clinically stable and unstable angina pectoris. Although some generalizations about the clinical-angiographic correlations can be made, we are continuously reminded of the frequent individual patient whose findings fall well outside of these generalizations. The majority of patients will have double- or triple-vessel coronary disease, with approximately 10 percent having in addition a left main coronary artery stenosis of at least 50 percent luminal diameter narrowing. Patients with unstable angina tend to have slightly greater vessel involvement in terms of lesion severity, though major differences, in general, are not seen. Intracoronary thrombus is present more frequently in patients with unstable angina and in those with recent myocardial infarction, though the overall incidence of this finding is low. Knowledge of the anatomic extent of coronary atherosclerosis is useful for determining prognosis and for selection from an ever-increasing variety of medical and surgical treatment options. Cardiac imaging is a continuously evolving field with new techniques such as digital angiography, three-dimensional dynamic imaging (dynamic spatial reconstructor), and nuclear magnetic resonance undergoing preclinical or clinical evaluation. These modalities hold promise for ultimately evaluating the coronary vessels from unlimited angles, assessing regional transmural myocardial perfusion and the cellular metabolic consequences of ischemia. However, current therapies (bypass surgery or coronary angioplasty) are based upon modifications of major epicardial coronary anatomy, and techniques that adequately define this anatomy are required. Moreover, for imaging data to have prognostic application, it must have previously established clinical prognostic correlates and be broadly applicable or widely available for patients. Thus for the present and immediate foreseeable future, coronary angiography will be the primary method for establishing the anatomic abnormalities of the coronary arteries, and these angiographic studies will remain vital for the clinical management of ischemic heart disease.

Angina Pectoris↗
PubMed1984

Restenosis after percutaneous transluminal coronary angioplasty (PTCA): a report from the PTCA Registry of the National Heart, Lung, and Blood Institute.

The results of follow-up angiography in patients from 27 clinical centers enrolled in the PTCA Registry were analyzed to evaluate restenosis after PTCA. Of 665 patients with successful PTCA, 557 (84%) had follow-up angiography (median follow-up 188 days). Restenosis, defined as an increase of at least 30% from the immediate post-PTCA stenosis to the follow-up stenosis or a loss of at least 50% of the gain achieved at PTCA, was seen in 187 patients (33.6%). The incidence of restenosis in patients who underwent follow-up angiography was highest within the first 5 months after PTCA. Restenosis was found in 56% of patients with definite or probable angina after PTCA and in 14% of patients without angina after PTCA. Twenty-four percent of patients with restenosis did not have either definite or probable angina. Multivariate analysis selected 4 factors associated with increased rate of restenosis: male sex, PTCA of bypass graft stenosis, severity of angina before PTCA and no history of MI before PTCA.

Angioplasty, Balloon↗
PubMed1984

Design of comparative clinical studies of percutaneous transluminal coronary angioplasty using estimates from the Coronary Artery Surgery Study.

The design of a prospective randomized trial of PTCA is discussed. It is suggested that patients with proximal subtotal occlusion of 1 or more vessels may be candidates for such a trial. Medical therapy as a control of 1-vessel CAD, medical or surgical therapy as a control for 2-vessel CAD (with 1 dilatable vessel) cases and surgical therapy as a control for 3-vessel CAD are most congruent with current practice. Possible criteria for comparison of PTCA with a control therapy include vital status, angina with daily activities, angina upon maximal exercise testing, MI, hospitalization, work status, cost, follow-up angiographic assessment, follow-up radionuclide ventriculography, measurement of immediate anatomic or hemodynamic change during initial treatment and quality-of-life indexes. These 10 measures are evaluated with respect to 9 desirable attributes for outcome criteria: the importance of the quantity measured, reproducibility, accuracy, low influence of investigator bias, low influence of subject bias, the measure is inexpensive and easy to obtain, sufficient occurrence to detect important differences, convenient to patients and measuring impairment due to disease. Examination of data from the Coronary Artery Surgery Study suggests that (1) a trial based on mortality alone is not feasible (because of a needed sample size in the thousands); (2) a trial using a combined death and/or MI end point would need approximately 1,000 cases even for patients with multivessel CAD; (3) approximately 950 patients would be needed in a trial to evaluate return to work (within 10%); (4) a trial based on pain relief (within 15% of the control group) would need 500 subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Angina Pectoris↗
PubMed1984

Ventricular arrhythmias during coronary angiography in patients with angina pectoris or chest pain syndromes.

Of 7,915 patients undergoing coronary angiography from 1978 to 1983, 39 (25 men and 14 women with a mean age of 57 years [range 37 to 79]) had sustained ventricular tachycardia (VT) or ventricular fibrillation (VF) during the procedure. Nine patients had atypical chest pain and 30 had typical angina. Fifteen had had a previous myocardial infarction. One patient had a history of VT or VF. Electrocardiograms taken at rest revealed a prolonged QT interval in 14. A normal ejection fraction was found in 79%. Coronary angiography revealed that 10 patients had 3-vessel disease, 15 had 1- or 2-vessel disease and 14 had normal coronary arteries. The VT or VF was seen with injection of contrast medium into the right coronary artery in 24, the left coronary artery in 10 and vein bypass grafts in 5 patients. Of the episodes of VT or VF, 67% occurred after injection of contrast medium into a minimally diseased coronary artery. In patients in whom VT or VF occurred after injection into a minimally diseased coronary artery, the arrhythmia was preceded by bradycardia, usually with pronounced widening of the QRS and QT intervals. This response was significantly different from that in patients in whom VT or VF occurred after injection into a coronary artery with significant stenosis; in these patients, VT or VF was initiated by a single premature ventricular contraction on a T wave. VT or VF was successfully cardioverted in all instances, without further arrhythmias.

Adult↗
PubMed1984

Effect of dipyridamole and aspirin on late vein-graft patency after coronary bypass operations.

To study the prevention of occlusion of aortocoronary-artery bypass grafts, we concluded a prospective, randomized, double-blind trial comparing long-term administration of dipyridamole (begun two days before operation) plus aspirin (begun seven hours after operation) with placebo in 407 patients. Results at one month showed a reduction in the rate of graft occlusion in patients receiving dipyridamole and aspirin. At vein-graft angiography performed in 343 patients (84 per cent) 11 to 18 months (median, 12 months) after operation, 11 per cent of 478 vein-graft distal anastomoses were occluded in the treated group, and 25 per cent of 486 were occluded in the placebo group. The proportion of patients with one or more distal anastomoses occluded was 22 per cent of 171 patients in the treated group and 47 per cent of 172 in the placebo group. All grafts were patent within a month of operation in 94 patients in the placebo group and 116 patients in the treated group; late development of occlusions was reduced from 27 per cent in the placebo group to 16 per cent in the treatment group. The results show that dipyridamole and aspirin continue to be effective in preventing vein-graft occlusion late after operation, and we believe that such treatment should be continued for at least one year.

Adult↗
PubMed1984

Clinical evaluation and application of cardiac laboratory high-definition video systems.

This study evaluated a new high line rate (1,023-line) high band-width (10 MHz) system, compared it to our high-definition, 525-line video system, and compared both video systems to 35-mm cine angiography in 117 patients undergoing clinically indicated coronary angiography. The subjective image quality of the 1,023-line video system was not significantly better than that of the 525-line system. High line rate, high band-width systems may have theoretical advantages, but the increased noise level under clinical angiographic conditions reduces their diagnostic quality. Comparison between video (all modes) and cine images resulted in cine being rated as the best modality, but the differences were slight. Radiation levels required for video imaging, however, were significantly less than those required for cine recording. Current clinical and computer interactive uses of video systems in the cardiac laboratory are described. The eventual role and potential replacement of cine recording by video tape systems will depend on continued developments in video recording techniques.

Adult↗
PubMed1984

Technical considerations for cardiac laboratory high-definition video systems.

With the expanding use of video systems in diagnostic imaging a significant benefit could be obtained by applying this technology in the cardiac catheterization laboratory. Reduced radiation exposure to the patient and staff, reduced examination cost by the elimination of cine film and equipment (cameras, processors, etc), and instant replay of each injection would result in improved patient care. We discuss the technical parameters of a video system which we have found suitable for diagnostic purposes and describe how this system is used on a day-to-day basis. In addition, the technical aspects of higher bandwidth, higher line rate systems is presented, and we show that these more sophisticated systems provide no advantage over conventional high-definition television and, in fact, degrade the diagnostic quality of the image.

Angiography↗
PubMed1984

The effects of xylazine hydrochloride on intrauterine pressure in the cow.

The effect of xylazine on bovine intrauterine pressure was studied in the diestrous and estrous cow. Ten milligrams of xylazine and 50 units of oxytocin were administered intravenously to 11 diestrous and 8 estrous nonlactating Holstein cows after an intrauterine catheter was placed per vaginam. Xylazine produced intrauterine pressure responses which did not differ statistically from those seen with oxytocin. Intrauterine pressure increased and waves of contractions were observed within 1.5 min after administering xylazine and oxytocin to estrous and diestrous cows. The pharmacological basis for the oxytocic-like action of xylazine is presently unknown.

Journal Article↗
PubMed1984

Platypnea-orthodeoxia: clinical profile, diagnostic workup, management, and report of seven cases.

Platypnea-orthodeoxia is a rare and poorly understood syndrome of orthostatic accentuation of a right-to-left shunt, usually across a patent foramen ovale. The syndrome is most commonly recognized in patients with a history of a major pulmonary disorder such as pneumonectomy, recurrent pulmonary emboli, or chronic lung disease. Pulmonary artery pressures are typically normal. The physiologic mechanism is unknown. We recommend that initial assessment consist of measurement of blood gases with the patient in the supine and upright positions. Orthostatic desaturation should prompt further investigation. A definitive diagnosis can most easily be obtained by tilt-table two-dimensional echocardiography with peripheral venous contrast medium. The shunt can be localized at the atrial level and directly visualized and semiquantitated. The decision about surgical closure of the patent foramen ovale is based on the degree of clinical disability. Because a significant shunt is manifest only in the upright position, astute clinical suspicion is of paramount importance for proper diagnosis. Increased awareness of this syndrome and ease of echocardiographic diagnosis will facilitate recognition of this potentially treatable cause of orthostatic hypoxia.

Cardiac Catheterization↗
PubMed1984

Angioplasty in total coronary artery occlusion.

Percutaneous transluminal coronary angioplasty was attempted without streptokinase in 24 patients with total coronary artery occlusion but without acute transmural myocardial infarction. The maximal duration of occlusion was estimated to be 1 week or less in 10 patients, more than 1 to 4 weeks in 6, more than 4 to 12 weeks in 3 and more than 12 weeks in 5. Dilation of the occluded artery was attempted in the left anterior descending coronary artery in 17 patients, in the right coronary artery in 4 and in the circumflex coronary artery in 3. Angioplasty was successful in 13 patients (54%): left anterior descending coronary artery in 59%, right coronary artery in 50% and circumflex coronary artery in 33%. In patients with successful dilation, there was a mean decrease in coronary artery stenosis from 100 to 23%. In the 19 patients whose occlusion was estimated to be of 12 weeks' duration or less, angioplasty was successful in 68%. In the five patients whose occlusion was estimated to be of more than 12 weeks' duration, dilation was not successful in any (p = 0.006). It is concluded that in selected patients with symptomatic coronary artery disease and recent coronary artery occlusion without associated acute myocardial infarction, percutaneous transluminal coronary angioplasty alone may be effective in restoring patency.

Aged↗
PubMed1984

Spatial distribution of DNA loop attachment and replicational sites in the nuclear matrix.

Biochemical fractionation was combined with high resolution electron microscopic autoradiography to study the localization in rat liver nuclear matrix of attached DNA fragments, in vivo replicated DNA, and in vitro synthesized DNA. In particular, we determined the distribution of these DNA components with the peripheral nuclear lamina versus more internally localized structural elements of isolated nuclear matrix. Autoradiography demonstrated that the bulk of in vivo newly replicated DNA associated with the nuclear matrix (71%) was found within internal matrix regions. A similar interior localization was observed in isolated nuclei and in situ in whole liver tissue. Likewise, isolated nuclear lamina contained only a small amount (12%) of the total matrix-bound, newly replicated DNA. The structural localization of matrix-bound DNA fragments was examined following long-term in vivo labeling of the DNA. The radioactive DNA fragments were found predominantly within interior regions of the matrix structure (77%), and isolated nuclear lamina contained less than 15% of the total nuclear matrix-associated DNA. Most of the endogenous DNA template sites for the replicative enzyme DNA polymerase alpha (approximately 70%) were also sequestered within interior regions of the matrix. In contrast, a majority of the endogenous DNA template sites for DNA polymerase beta (a presumptive repair enzyme) were closely associated with the peripheral nuclear lamina. A similar spatial distribution for both polymerase activities was measured in isolated nuclei before matrix fractionation. Furthermore, isolated nuclear lamina contained only a small proportion of total matrix-bound DNA polymerase alpha endogenous and exogenous template activities (3-12%), but a considerable amount of the corresponding beta polymerase activities (47-52%). Our results support the hypothesis that DNA loops are both anchored and replicated at nuclear matrix-bound sites that are predominantly but not exclusively associated with interior components of the matrix structure. Our results also suggest that the sites of nuclear DNA polymerase beta-driven DNA synthesis are uniquely sequestered within the characteristic peripheral heterochromatin shell and associated nuclear envelope structure, where they may potentially participate in DNA repair and/or replicative functions.

Animals↗
PubMed1984

Deiodination of reverse 3, 3', 5'-triiodothyronine by hepatic nuclear protein preparations.

A reassessment of the binding characteristics of [125I]rT3 to putative receptors in nuclear protein extracts of rat and pig liver revealed that significant deiodination of radioligand occurred during incubation. When previously reported separation procedures are used, released radioiodine is included in the protein-bound [125I]rT3 fraction during separation of protein bound from free hormone by Sephadex G-25 chromatography. This misclassification produces artefacts in binding curves and Scatchard plots used to calculate binding affinity and capacity. Previously reported affinities and capacities derived by this methodology are therefore erroneous. Deiodination of rT3 in the nuclear protein extracts appears to be mediated by outer ring deiodinase. Whereas dithiothreitol markedly enhanced radioiodine generation, the enzyme inhibitors ipodate and salicylate reduced iodine production. These effects produced dramatic changes in apparent binding curves for the radioreceptor assay. When [125I]T3 was incubated with nuclear protein extract, no significant deiodination was detected. Whereas it is likely that the deiodinase is a microsomal contaminant of the nuclear preparation, as suggested by the presence of glucose-6-phosphatase in the nuclear protein preparation, the possibility of an intrinsic nuclear-linked deiodinase cannot be overlooked.

Animals↗
PubMed1983

Employment and recreation patterns in patients treated by percutaneous transluminal coronary angioplasty: a multicenter study.

Employment and recreational patterns were analyzed in 279 patients who underwent percutaneous transluminal coronary angioplasty (PTCA) for treatment of symptomatic coronary artery disease. PTCA was successful in 180 patients (65%). When it was unsuccessful, coronary artery bypass graft surgery was usually performed (80%). Return-to-work rates were high irrespective of the outcome of PTCA. Of patients employed full-time or part-time before treatment, 98.5% of those who had successful PTCA alone and 97% of those whose PTCA was unsuccessful but who underwent uncomplicated coronary artery bypass surgery maintained or improved their work status. In a subgroup of men who had been employed in occupations requiring physical labor, 85% of the men whose PTCA was successful returned to work, compared with 68% of those whose PTCA was unsuccessful. The interval from attempted PTCA to return to work was significantly shorter in the successfully treated group; in patients with successful PTCA, the median time to return to work was 14 days, compared with 60 days in patients in whom PTCA was unsuccessful (p less than 0.001). During follow-up, patients with successful PTCA had less angina and were more active in recreational activities than patients who required alternative treatments.

Angioplasty, Balloon↗