Biomedical subjects

D H Schmidt

Publications and source records attributed to D H Schmidt.

At least 19 recordsLinked to original sources

PubMed1995

Congenital clavicular pseudoarthrosis associated with vascular thoracic outlet syndrome: case presentation and review of the literature.

Thoracic outlet syndrome (TOS) associated with congenital clavicular pseudoarthrosis is rare in adults and often misdiagnosed. In this case report, we describe an adult female who was found to have thrombosis of the subclavian and axillary arteries with embolization documented by invasive angiography. This unusual vascular manifestation of TOS should remind physicians that anatomic derangements may predispose to upper extremity ischemia.

Adult↗

PubMed1995

Transesophageal echocardiographically guided atrial transseptal catheterization in patients with normal-sized atria: incidence of complications.

The incidence of cardiac complications from atrial transseptal catheterization has never been quantified in patients with normal-sized atria. Series defining the complication rate are derived from diseased hearts with structural changes that may alter the complication rate of the procedure. The generation of a standardized incidence of perforation in a population of structurally normal atria has important implications. A total of 46 atrial transseptal catheterizations guided by transesophageal echocardiography (TEE) for radiofrequency ablation of left-sided accessory pathways was performed in 42 patients during a 3-year period (1990-1993). Clinical and echocardiographic data were analyzed, with special attention given to TEE reports pre- and post-transseptal catheterization. Only one complication occurred in the 46 procedures (2.2%): a perforation of the left atrium that led to pericardial effusion and cardiac tamponade. In a small series of patients with normal sized atria, we have demonstrated that TEE-guided transseptal catheterization in a procedure with a low complication rate.

Adult↗

PubMed1994

High incidence of renal artery stenosis in patients with coronary artery disease.

The incidence of renal artery stenosis (RAS) in patients with coronary artery disease (CAD) has not been well documented. Over a 9-month period, 196 patients who underwent coronary angiography because of clinically suspected CAD had routine nonselective renal cine or digital subtraction angiography. There were 68 females and 128 males with a mean age of 63 years (range 35-85). Angiographically significant CAD was present in 152 patients (78%). Of the total patient cohort, 29 patients (15%) had mild RAS (< 50%), and 36 patients (18%) had significant RAS (> or = 50%). In patients with normal coronary arteries, only three patients (7%) had RAS. Thirty-three patients (92%) with severe RAS also had CAD. Of these 33 patients, 45% had hypertension, 30% had hyperlipidemia, 24% had diabetes mellitus, 24% had renal insufficiency (creatinine > or = 1.5), and 51% were smokers. In addition, it was noted that 20 of these patients (61%) had two or more of the above-listed clinical parameters. However, univariate analysis using the chi-square test revealed that only CAD (22% P < 0.03) and renal insufficiency (29% P < 0.15) were reliable clinical predictors of RAS. In conclusion, RAS is a frequent finding in patients with CAD, particularly when renal insufficiency is also present.

Adult↗

PubMed1994

Utilization of the Wallstent for the treatment of innominate vein obstruction: a case report.

Debilitating obstruction of the large veins may occur from external compression, neointimal proliferation or thrombosis. Appropriate interventions are contingent upon the underlying etiology and the local vascular anatomy. A case of innominate vein obstruction is presented illustrating the available intravascular therapeutic options, with special emphasis placed on intravenous stenting.

Aged↗

PubMed1993

Evaluating the flow characteristics of artificial pumping devices using nuclear scintigraphy.

The design and development of artificial blood pumps require qualitative and quantitative data relative to pump filling, ejection, and wall motion in order to optimize the design and maximize the pattern of blood flow through the pump. To assist in the development of an artificial heart, we utilized radionuclide scintigraphy and a high-resolution gamma camera to evaluate the flow patterns through the pump. We performed a comparative analysis of the flow patterns in a pneumatically driven ventricular assist device (Sarns/3M VAD) and the electrically driven Milwaukee Heart. These analyses disclose some significant differences between the two devices with regard to the blood sac compression patterns and ejection as well as valvular regurgitation. On the basis of these findings, nuclear scintigraphy for analyzing fluid shear stress and flow dynamics seems a useful technique for evaluating blood flow through artificial blood pumps. Because the procedure does not require a translucent casing or direct contact with the device being studied, it would be especially useful in evaluating artificial blood pumps implanted in patients with heart failure.

Coronary Circulation↗

PubMed1992

Left ventricular volume calculation using a count-based ratio method applied to first-pass radionuclide angiography.

Most count-based radionuclide methods for calculating left ventricular volume rely on measurement of radioactivity in a peripheral blood sample and a measurement of ventricle to collimator distance. We have developed a method which requires neither a blood sample nor a distance measurement and which is applicable to first-pass radionuclide angiography. The parameters used to calculate volume are the area of pixel, the total counts in the left ventricle and the maximum pixel count. The equation was used to calculate the volumes in 50 patients who had both resting first-pass radionuclide angiography (25 patients with a single crystal and 25 patients with a multicrystal camera) and contrast ventriculography on the same day. Correlation coefficients for end-diastolic and end-systolic volumes showed r ranging 0.93-0.98 and standard error of estimate ranging 23-35 ml for end-diastolic volume (14%-17% of mean end-diastolic volume) and 16-23 ml for end-systolic volume (18%-21% of mean end-systolic volume). Image processing software for extracting the needed values is generally available on most commercial nuclear medicine imaging systems and the additional time for the calculations is short. Although the theory is based on multiple assumptions, the volume calculation appears to be reasonably accurate and clinically applicable.

Adult↗

PubMed1991

Evaluation of transient mitral regurgitation in coronary artery disease.

The pathoanatomy and factors associated with transient mitral regurgitation (MR) induced by myocardial ischemic stress are unknown. Changes in valvular and ventricular parameters during transient, stress-induced MR in patients with coronary artery disease were investigated, and the clinical characteristics of these patients were identified. Color flow Doppler echocardiography was used to quantify the MR color area, the coaptation point of the mitral leaflets, the mitral valve anulus diameter, and left ventricular volumes and wall motion in 42 patients before and immediately after exercise echocardiography (group 1, n = 27), or before and during percutaneous transluminal coronary angioplasty (PTCA) (group 2, n = 15). Of the 27 patients with exercise echocardiography, 4 developed new, transient MR (group 1B) and 9 had MR both at rest and during exercise (group 1C). Of the 15 patients with PTCA, 7 developed new MR (group 2B). New MR (groups 1B and 2B) was associated with more severe stress-induced ventricular dyskinesia (p less than 0.05) than was seen in patients with chronic MR (group 1C) or in patients without MR, and occurred predominantly in patients with left anterior descending or right coronary artery stenoses. Stress-induced MR was not associated with changes in blood pressure or in mitral valve anulus diameter, nor with the development of mitral valve prolapse. It was associated with apical displacement of the mitral leaflets in patients in group 1B and C (p less than 0.05). New MR flow areas were significantly smaller than those in patients with chronic MR (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗

PubMed1990

Technically suboptimal first-pass radionuclide angiographic studies.

First-pass radionuclide angiography (FPRNA) has proven to correctly assess left ventricular function, however, technical difficulties do occur. One hundred and thirty one patients had contrast angiography and resting radionuclide angiography within 24 h. Of the 131 patients, 86 (66%) had adequate studies and 45 (34%) were technically suboptimal studies. In the latter group, low counts affected the quality of the images but did not change the left ventricular ejection fraction (LVEF) or regional wall motion (RWM) scores. Patients with high background activity showed overestimation of LVEF, however, by using a formula that was derived from the linear regression the LVEF could be calculated accurately in most cases. Multiple technical problems were noted in 14 patients in whom the best correlation was between contrast LVEF and background uncorrected LVEF from FPRNA (r = 0.87). In the latter group, FPRNA showed overestimation of RWM in 8 patients (57%), mainly in the inferior wall. We conclude that for most technically compromised first-pass radionuclide angiographic data, accurate LVEF values can be achieved but errors in regional wall motion interpretation will occur, especially when multiple technical problems exist.

Female↗

PubMed1990

Mitral regurgitation: parameters that affect the correlation between Doppler echocardiography and contrast ventriculography.

The correlation between Doppler and contrast angiographic estimation of severity of mitral regurgitation was assessed retrospectively in 60 patients with native mitral valve disease. Results showed r = 0.82. Among 15 parameters (demographic, clinical, echocardiographic and hemodynamic) 3 were found to be associated with overestimation of the severity by Doppler: low left ventricular ejection fraction, low cardiac output, and high mean pulmonary artery capillary wedge pressure. On the other hand, a large left atrium was associated with underestimation of mitral regurgitation by Doppler. Based on that data, Doppler results were adjusted in a prospective group of 30 patients with native mitral valve disease. The correlation between contrast ventriculography and uncorrected Doppler results showed r = 0.83, while the corrected Doppler results showed r = 0.91. The study implies that although a good correlation is found between the two modalities for estimation of mitral regurgitation, a better correlation can be achieved by adjusting the Doppler results according to the above-mentioned parameters.

Contrast Media↗

PubMed1990

Regional myocardial blood flow with a reperfusion catheter and an autoperfusion balloon catheter during total coronary occlusion.

We investigated the ability of two new coronary perfusion catheters to maintain regional myocardial blood flow throughout a 90-minute period of occlusion. In 21 dogs (group I = total occlusion control; group II = reperfusion catheter; group III = autoperfusion balloon catheter) we studied regional blood flow, distal coronary perfusion pressure, infarct size, and red blood cell hemolysis after placement of either catheter into the left anterior descending coronary artery. Regional (microsphere) blood flow showed a reduction in transmural blood flow during occlusion in comparison to baseline values (1.07 +/- 0.12 to 0.81 +/- 0.11 and 1.01 +/- 0.16 to 0.73 +/- 0.08 ml/min subendocardial perfusion for groups II and III, respectively). Comparable changes in blood flow were observed in the subepicardial and midmyocardial regions. Distal coronary perfusion pressures were reduced by 26% and 28% for groups II and III, respectively. Both catheters prevented significant infarction and maintained adequate regional myocardial blood flow throughout the 90-minute period of occlusion without significant complications of clotting or destruction of erythrocytes.

Angioplasty, Balloon, Coronary↗

PubMed1990

Left ventricular volume calculation using a count-based ratio method applied to multigated radionuclide angiography.

The purpose of this study was to investigate the accuracy of a new count-proportional method for the measurement of left ventricular volume when applied to gated equilibrium blood-pool imaging. An equation is developed that relates total chamber volume, Vt, to the area of a pixel (M) and the ratio (R) of total counts within the chamber to the counts within the hottest pixel in the chamber such that Vt = 1.38 M3R3/2. The value of M is a constant for the particular scintillation camera-collimator system and R is obtained from observed count rates. All calculated volumes were compared to volumes measured using biplane contrast ventriculography. In 25 patients, the method for ventricular volumes gave an r of 0.95 and an s.e.e. of 23 ml [Volume (nuclear) = 0.94 Volume (cath) + 1.3]. Endsystolic volume was best calculated from end-diastolic volume and ejection fraction. Manual regions of interest were more accurate than automated regions of interest. This method appears to be as accurate as more complex approaches and has the advantage of not requiring attenuation correction or blood sampling.

Angiography↗

PubMed1988

Inadequate subendocardial oxygen delivery during perfluorocarbon perfusion in a canine model of ischemia.

Perfusion of the coronary artery distal to an occlusion was performed in 16 canine preparations to compare the mechanical perfusion of autologous blood to the perfluorocarbon fluosol DA, 20% emulsion (FDA-20). Both substances were perfused under similar conditions (30, 60, and 80 ml/min) and regional electrograms, contractility, and coronary perfusion were measured relative to native coronary perfusion. Autologous blood (60 and 80 ml/min) produced a significant increase in regional (epicardial, midmyocardial, and endocardial) and transmural flow, but not in the endocardial/epicardial perfusion ratio. No other significant changes were observed during autologous blood perfusion. In contrast, FDA-20 perfusion resulted in significant ST depression (-1.8 +/- 0.2, -1.7 +/- 0.2, and -1.3 +/- 0.3 mm) at 30, 60, and 80 ml/min, respectively. FDA-20 also induced a significant decrease in distal diastolic coronary pressure and resistance, a significant decrease in the endocardial/epicardial perfusion ratio at all three perfusion rates, and a significant reduction in delivery of O2 to the subendocardium. These results indicate that autologous blood perfusion of the distal coronary artery during occlusion preserves myocardial function to a better degree than does FDA-20.

Animals↗

PubMed1987

Effect of age and training on aerobic capacity and body composition of master athletes.

Maximum oxygen uptake (VO2max) and body composition have been shown to deteriorate with age. How much of the decline is attributable to aging and how much is affected by reduced physical activity is not known. The purpose of this investigation was to determine the aerobic capacity and body composition of 24 master track athletes and to evaluate the relationship to age and maintenance of training over a 10-yr period. The subjects (50-82 yr of age) were retested after a 10.1-yr follow-up (T2). All continued their aerobic training, but only 11 were still highly competitive (COMP) and continued to train at the same intensity. The other 13 athletes studied became noncompetitive (post-COMP) and reduced their training intensity. The results showed the COMP group to maintain its VO2max and maximum O2 pulse while the post-COMP group showed a significant decline (54.2-53.3 vs. 52.5-45.9 ml X kg-1 X min-1; 20.7-20.8 vs. 22.4-20.0 ml/beat from test one (T1) to T2 for the COMP vs. post-COMP groups, respectively). Maximum heart rate declined 7 beats/min for both groups. Body composition showed no difference between groups from T1 to T2. For both groups body weight declined slightly (70.0-68.9 kg), percent fat increased significantly (13.1-15.1%), and fat-free weight decreased significantly (61.0-59.0 kg). Thus, when training was maintained, aerobic capacity remained unchanged over the follow-up period. Body composition changed for both groups and may have been related to aging and/or the type of training performed.

Aged↗

PubMed1986

Functional translation of exercise responses from graded exercise testing to exercise training.

This study attempts to develop a quantitative approach to the prescription of absolute exercise intensity during level ground ambulation (min/mile) or cycle ergometry (kpm) from responses observed during GXT. A total of 345 subjects performed GXT and exercise training sessions with either the Bruce treadmill protocol and level ground ambulation (N = 154) or cycle ergometry (N = 191). Responses from 90% of each group were used to generate equations for predicting training pace (or power output) from the time (or power output) during the GXT when target HR was achieved. FAI was also included in the prediction of training pace (or power output). The remaining 10% of subjects in each group were used to cross-validate the prediction equations. The correlation between the time (or power output) during GXT when the training HR was observed and the pace of ambulation (or power output) was 0.70 for treadmill walking and 0.88 for cycle-cycle. Correlations were increased by the addition of FAI to the prediction equation. The results of this investigation suggest that the absolute intensity of exercise for training can be predicted accurately from GXT results.

Cardiac Rehabilitation↗

PubMed1986

High count rate first-pass radionuclide angiography using a digital gamma camera.

In this study, first-pass radionuclide angiography (FPRNA) was performed using a digital single-crystal gamma camera. Twenty-nine men and six women (ages 43-80, mean 61 yr) underwent FPRNA in the supine position immediately prior to cardiac catheterization. Total counts/sec in the whole field-of-view in the right ventricular phase were 150,352 +/- 26,006. Background uncorrected counts in the representative cycle were 7,651 +/- 2,527 at end-diastolie and 4,904 +/- 2,314 at end-systolie. A linear correlation between FPRNA left ventricular (LV) ejection fraction and contrast LV ejection fraction gave an r = 0.95 with an s.e.e. of 0.05. Analyses of intra- and interobserver variability gave r = 0.99 and 0.98 and an s.e.e. of 0.02 and 0.03, respectively. Spearman-Rank correlation coefficients between FPRNA and contrast angiographic wall-motion scores were greater than 0.8 for all walls, while sensitivity/specificity were 0.86/0.90, 0.76/1.00, 0.76/1.00 for anterior, apical, and inferior wall-motion abnormalities, respectively. We conclude that satisfactory counting statistics for FPRNA can be obtained with a digital gamma camera, and that accurate and reproducible measurements of global and regional left ventricular function can be obtained with this technique.

Adult↗

PubMed1986

Background correction in first-pass radionuclide angiography: comparison of several approaches.

This study was designed to test the comparative accuracy of several commonly used background correction techniques in first-pass radionuclide angiography (FPRNA). Thirty patients underwent FPRNA and single plane contrast angiography (CA) within 1 hr of each other. The left ventricular ejection fractions (LVEF) calculated from the different background subtraction approaches to FPRNA were compared to the CA LVEF. When applied to a representative cycle, a horseshoe-shaped background region of interest (BKROI) underestimated LVEF (p less than 0.005, r = 0.91, s.e.e. = 0.06) while a ring shaped BKROI adjusted at end-systole for aortic valve motion insignificantly overestimated LVEF (p = NS, r = 0.91, s.e.e. = 0.07). A lung background approach applied to a representative cycle gave the best correlation with CA (p = NS, r = 0.96, s.e.e. = 0.04). Without using a representative cycle, time-activity curves from a horseshoe-shaped BKROI and the LV ROI were created and the LV curve was normalized to the peak counts in the BKROI curve. LVEF calculated from the normalized curve correlated favorably with CA LVEF (p = NS, r = 0.91, s.e.e. = 0.08). The influence of some recently described improvements in representative cycle generation are also documented.

Aged↗

PubMed1985

Assessment of single vessel coronary artery disease: results of exercise electrocardiography, thallium-201 myocardial perfusion imaging and radionuclide angiography.

The sensitivity of the commonly used stress tests for the diagnosis of coronary artery disease was analyzed in 46 patients with significant occlusion (greater than or equal to 70% luminal diameter obstruction) of only one major coronary artery and no prior myocardial infarction. In all patients, thallium-201 perfusion imaging (both planar and seven-pinhole tomographic) and 12 lead electrocardiography were performed during the same graded treadmill exercise test and radionuclide angiography was performed during upright bicycle exercise. Exercise rate-pressure (double) product was 22,307 +/- 6,750 on the treadmill compared with 22,995 +/- 5,622 on the bicycle (p = NS). Exercise electrocardiograms were unequivocally abnormal in 24 patients (52%). Qualitative planar thallium images were abnormal in 42 patients (91%). Quantitative analysis of the tomographic thallium images were abnormal in 41 patients (89%). An exercise ejection fraction of less than 0.56 or a new wall motion abnormality was seen in 30 patients (65%). Results were similar for the right (n = 11) and left anterior descending (n = 28) coronary arteries while all tests but the planar thallium imaging showed a lower sensitivity for isolated circumflex artery disease (n = 7). The specificity of the tests was 72, 83, 89 and 72% for electrocardiography, planar thallium imaging, tomographic thallium imaging and radionuclide angiography, respectively. The results suggest that exercise thallium-201 perfusion imaging is the most sensitive noninvasive stress test for the diagnosis of single vessel coronary artery disease.

Adult↗

PubMed1985

Myocardial perfusion after aortocoronary bypass surgery: measurements at rest and after administration of isoproterenol.

This study examined quantitative regional myocardial perfusion (RMP) measured by the washout of 133Xe at rest and after an isoproterenol challenge in 50 patients (group I) studied 8 to 14 days after they underwent saphenous vein bypass grafting to the left coronary artery, and compared this with RMP measured in the native left coronary artery in 14 patients (group II) with significant coronary artery disease and in 12 normal subjects (group III). The double product of the heart rate and aortic systolic pressure was used as an indicator of demand. The statistical significance of group comparisons was analyzed with Dunn's multiple comparisons among means test. Analysis of the data showed no significant difference among the groups with respect to aortic systolic pressure. In subjects at rest, heart rate was lower in groups II and III than in group I, and double product was lower in group II than in group I. After isoproterenol, both heart rate and double product were lower in group II compared with groups I and III, but there was no significant difference between groups I and III with respect to heart rate or double product. Mean resting RMP in group II was lower than in group I; however, results of other group comparisons were insignificant for resting parameters. After isoproterenol, mean flow (ml/100 g/min) in group I was similar to flow in group III (130 +/- 24 vs 139 +/- 26). In contrast, the average flow response after isoproterenol was significantly less in group II when compared with that in group I (105 +/- 20 vs 130 +/- 24) and with that in group III (105 +/- 20 vs 139 +/- 26). Because of differences in levels of demand with isoproterenol, the change in flow was normalized to the percent increase in double product. These data showed results similar to those above, i.e., normalized RMP in patients with coronary artery disease was significantly lower than that in normal subjects (82 +/- 41 vs 119 +/- 57) and in revascularized patients (82 +/- 41 vs 105 +/- 54). However, there was no significant difference between normal subjects and patients who had undergone surgery. To further evaluate the relationship of flow response to demand parameters, we plotted RMP/double product vs resistance. The data revealed a significant correlation between these variables in all groups both in subjects at rest and after isoproterenol.(ABSTRACT TRUNCATED AT 400 WORDS)

Coronary Artery Bypass↗