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Biomedical subjects

T M Bashore

Publications and source records attributed to T M Bashore.

At least 145 records · Page 8Linked to original sources
PubMed1987

Right ventricular aneurysm due to ischemic disease. Diagnosis by radionuclide angiography with localization of the site of PVC origin by phase analysis.

A case of right ventricular aneurysm due to coronary artery disease in a 69-year-old male with no prior history of surgery or chest trauma is reported. The presence of the aneurysm was diagnosed by gated radionuclide angiography and confirmed by contrast angiography. This is the first description of an isolated right ventricular aneurysm on the basis of ischemic disease. In addition, the patient had recurrent ventricular tachycardia and frequent premature ventricular contractions (PVC's). Using radionuclide angiographic phase analysis of the PVC's, their apparent origin was localized to the margin of the right ventricular aneurysm.

Aged↗
PubMed1987

Failure of normalized ventricular filling rates to predict true filling rates.

Ventricular filling rates derived from radionuclide angiographic (RNA) time-activity curves are commonly expressed as normalized values. The assumption that normalized filling rates have a relationship to the actual filling rates was tested. RNA and contrast angiography were performed within 20 min of one another in 21 patients with widely disparate volumes. The RNA time-activity curve was converted from counts to milliliters by equating the contrast angiography derived end diastolic volume to the end diastolic count rate determined by RNA. Peak filling rates were normalized to end diastolic volume (EDV), stroke volume (SV, and peak ejection rate (ER). No significant correlation between the normalized filling rates and the true filling rate was found. Significant correlations were found between the EDV normalized filling rate and the EDV (r = -0.70) and the ejection fraction (r = 0.89). Normalized filling rates are dependent upon the normalizing variable and are not a pure measure of ventricular filling rates. As the technique of gated radionuclide angiography has matured, it has become apparent that there is more information in the time-activity curve than just the ejection fraction. The emptying rates, filling rates, time to peak emptying, and time to peak filling are parameters that are also available from the time-activity curve. Several authors have used this information to quantitate ventricular ejection and filling rates [1-6]. Since the contrast angiography literature would indicate that in some disease states ventricular filling is impaired [7,8], attempts have been made to identify impaired filling rates by radionuclide techniques. Using this method, decreased normalized filling rates have been found in groups of patients with coronary artery disease and it has been suggested that the observed decrease is due to impairment of active relaxation and/or to reduced compliance [2,3,5,6]. It has even been suggested that the decrease seen in the normalized filling rates may be a reflection of ischemia in the resting patient [6]. While these RNA derived parameters have been normalized to end diastolic volume by most authors, normalization to stroke volume and maximum ejection rate have also been suggested [9,10]. A possible rationale for normalization is that the activity measured over the ventricle is dependent upon many factors, including radionuclide dose, attenuation from the patient's chest wall, the specific type of collimator used, thickness of the crystal, and the window width.(ABSTRACT TRUNCATED AT 400 WORDS)

Cardiomyopathies↗
PubMed1987

Altered phosphate metabolism in myocardial infarction: P-31 MR spectroscopy.

The high-energy myocardial phosphate metabolism of four patients with acute anterior myocardial infarction after coronary angioplasty and drug therapy was evaluated with cardiac-gated phosphorus magnetic resonance (MR) depth-resolved surface coil spectroscopy (DRESS) 5-9 days after the onset of symptoms. Significant reductions (about threefold) in the phosphocreatine (PCr) to inorganic phosphate (Pi) ratio and elevations in the Pi to adenosine triphosphate (ATP) ratio were observed in endocardially or transmurally derived MR spectra when compared with values from epicardially displaced spectra and values from seven healthy volunteers (P less than .05). High-energy phosphate metabolites and Pi ratios did not vary significantly during the cardiac cycle in healthy volunteers. However, contamination of Pi resonances by phosphomonoester components, including blood 2,3-diphosphoglycerate, precluded accurate spectral quantification of Pi and pH. The results indicate that localized P-31 MR spectroscopy may be used to directly assess cellular energy reserve in clinical myocardial infarction and to evaluate metabolic response to interventions.

Adult↗
PubMed1986

Localization of the site of ventricular premature complexes by radionuclide angiographic phase imaging.

To investigate whether gated radionuclide angiographic phase imaging is useful for visually displaying the origin of ventricular premature complexes (VPCs), 82 patients were studied by gating only VPCs. The VPC "origin" by the scintigraphic method was defined as the area of earliest phase and was compared with that predicted by 12-lead electrocardiographic criteria in all patients and to invasive electrophysiologic mapping in 10. Separating the right ventricle into 3 and the left ventricle into 4 segments, the phase imaging method and the electrocardiographic criteria agreed as to ventricle of VPC origin in 69 patients (84%) and segment of origin within each ventricle in 46 (56%). When baseline ventricular wall motion was analyzed, the 2 methods agreed to the ventricle of VPC origin in 31 of 33 patients (94%) with normal wall motion, 20 of 23 (87%) with segmental wall motion abnormalities and 19 of 26 (73%) with diffuse wall motion abnormalities. Agreement between the 2 methods as to specific segmental localization of the arrhythmia focus was noted in 21 of 33 patients (64%) with normal wall motion, 11 of 23 (48%) with segmental wall motion abnormalities and 12 of 26 (46%) with diffuse hypocontractility. In the 10 patients with endocardial mapping studies, the phase imaging technique confirmed the segment of VPC origin in all 10; the electrocardiographic method was accurate in 8. Thus, gated radionuclide angiographic phase imaging methods may be of value in noninvasively defining the origin of spontaneous VPCs. The visual format allows ready interpretation of the arrhythmia origin, and there may be an advantage to this approach over electrocardiographic morphometric criteria.

Adolescent↗
PubMed1986

Clinical and angiographic assessment of complex mammary artery bypass grafting.

The internal mammary artery has become the coronary bypass graft of choice in recent years because of enhanced long-term patency. Along with this trend, sequential, bilateral, and free mammary grafts have been employed more frequently in an effort to maximize the number of distal internal mammary anastomoses. This approach of maximally using the internal mammary artery (complex mammary grafting) seems logical, but at present little information about patency of the newer types of internal mammary artery grafts is available to justify the more complicated procedures. Over a 15 month period, 207 patients underwent bypass graft angiography from 1 to 32 weeks after operation. This is an 85% restudy rate for a consecutive series of coronary bypass procedures. Patency was defined as complete filling of the graft and distal vessel bypassed. A total of 841 distal vessels were grafted, or 4.1 per patient. The overall patency rate was 91% for 503 distal vein graft anastomoses and 99% for 338 internal mammary artery grafts. Individual patency rates of distal anastomoses, expressed as number patent/total (percent patent), were as follows: simple vein grafts, 262/285 (92%); sequential vein grafts, 196/218 (90%); left internal mammary artery to left anterior descending coronary artery, 109/110 (99%); left internal mammary to circumflex marginal artery, 14/14 (100%); right internal mammary to right coronary artery, 19/20 (95%); right internal mammary to left anterior descending coronary artery, 10/10 (100%); right internal mammary to circumflex marginal artery via transverse sinus, 18/20 (90%); sequential left internal mammary artery to left anterior descending system, 133/134 (99%); sequential left internal mammary to circumflex marginal system, 15/15 (100%); free internal mammary artery, 9/9 (100%); free sequential internal mammary artery, 6/6 (100%). Of the 18 patent transverse sinus right internal mammary grafts to the circumflex marginal artery, three exhibited very slow flow and probably were not functional. The hospital mortality associated with internal mammary revascularizations was 0.4% for nonemergency cases and 3.1% for emergency procedures. On the basis of clinical and postoperative graft patency data, expanded use of more complicated types of mammary grafts seems justified. Function of the right internal mammary graft to the circumflex marginal artery was suboptimal, and this method has been discontinued. All other complex mammary techniques had excellent patency rates as compared to vein grafts, and these differences may become even more significant in the late postoperative period.(ABSTRACT TRUNCATED AT 400 WORDS)

Aged↗
PubMed1985

Effect of acute standing and prolonged upright activity on left ventricular hemodynamics, systolic and diastolic intervals, and QT-QS2 relationship.

It is generally accepted that upright posture decreases preload and afterload, which could alter left ventricular (LV) performance. It is not known if changes occurring with acute standing persist after prolonged ambulatory activity (amb-act). In seven normal subjects echocardiographic end-diastolic and end-systolic diameters, percent shortening of the internal diameter (% delta D) and end-systolic wall stress (ES-WS), radionuclide diastolic volume and ejection fraction, preejection period over left ventricular ejection time (PEP/LVET), and diastolic time and QT-QS2 were measured supine, within 1 to 2 minutes after standing and after prolonged (60 minutes) amb-act. In addition, serial measurements were performed in PEP/LVET for 105 minutes at 15-minute intervals. With acute standing, end-diastolic diameter, diastolic volume, and ES-WS decreased (p less than 0.01); heart rate and PEP/LVET increased (p less than 0.01); while % delta D and ejection fraction remained unchanged. There was an inverse correlation between change in PEP/LVET and diastolic diameter (r = -0.59), but no correlation between PEP/LVET and ES-WS. The diastolic time per beat and per minute decreased (375 +/- 115 msec from 519 +/- 176 msec [p less than 0.01] and 31.3 +/- 4.2 sec/min from 33.7 +/- 4.5 sec/min [p less than 0.01]). The QT-QS2 increased when compared to supine (-7 +/- 7.6 msec from -22 +/- 7.7 msec [p less than 0.005]), but the QT-QS2 relationship remained normal (QT less than or equal to QS2). All the dynamic changes that occurred with acute standing tended to persist during prolonged amb-act.

Adult↗
PubMed1985

Prevention of bedrest-induced physical deconditioning by daily dobutamine infusions. Implications for drug-induced physical conditioning.

The effects of intermittent infusions of dobutamine were studied in young normal male subjects during a period of bedrest deconditioning to determine whether this synthetic catechol affects physical conditioning processes in humans. 24 volunteers were placed at bedrest and randomized to daily 2-h treatments of saline infusions (control), dobutamine infusions, or maintenance exercise (control). Exercise, hemodynamic, and metabolic studies were performed at base line and at the termination of the 3-wk treatment period. Maximal exercise (duration, oxygen consumption, and workload) fell for the saline group and remained unchanged for the dobutamine and exercise groups. Hemodynamics during exercise were maintained the same as pretreatment base line for the dobutamine and exercise groups, whereas stroke volume and cardiac output dropped and heart rate rose for the saline group. The metabolic profile showed an increased blood lactate response at rest and during submaximal exercise after 3 wk of bedrest for the saline group, and essentially no change for the exercise and the dobutamine groups. Extraction of oxygen across the exercising lower limb rose for the dobutamine group, as did the activity of the skeletal muscle oxidative enzymes, citrate synthetase, and succinate dehydrogenase. In contrast to the exercise control group, the saline and dobutamine groups developed orthostatic hypotension, tachycardia, and accentuation of the renin-aldosterone response over the 3-wk treatment period; for the saline group, this is best explained by the observed fall in blood volume and for the dobutamine group, by the blunting of vascular vasoconstrictive responses. During a period of bedrest deconditioning in humans, infusions of dobutamine maintain many of the physiologic expressions of physical conditioning.

Adult↗
PubMed1984

Relation between premature ventricular contraction site of origin (defined by radionuclide phase analysis) and subsequent left ventricular function.

It has been suggested that the effect of a premature ventricular contraction (PVC) on left ventricular (LV) function depends on the site of origin of the PVC, and that the subsequent impairment of LV performance during a PVC may be more pronounced if baseline LV dysfunction is present. To evaluate these concepts, radionuclide angiographic phase image analysis of spontaneous PVCs was performed after acquisition of images from PVCs alone by a new gating procedure. The sites of the PVCs were localized to 1 of 3 right ventricular (RV) or 5 left ventricular (LV) regions by this method. LV function during PVCs was assessed and compared with baseline by noting the LV ejection fraction (EF) during PVCs, the difference between sinus LVEF and PVC EF, and the normalized PVC EF (PVC EF/sinus EF). Twenty-four patients had LV PVC sites and 19 had RV sites. LV function during a PVC appeared to be independent of either the ventricle of origin of the PVC or a specific site of origin within the ventricles. The resultant PVC ventricular function also appeared independent of sinus LVEF and sinus wall motion abnormalities. In addition, no correlation between coupling interval and any of the variables measured was demonstrated (although extremely short coupling intervals were not evaluated). These data suggest that the effects of PVCs on ventricular performance seen during ventricular ectopy are independent of the site of origin of the PVC, baseline wall motion abnormalities or PVC coupling interval in the population studied.

Adolescent↗
PubMed1984

Hemodynamic correlates for timing intervals, ejection rate and filling rate derived from the radionuclide angiographic volume curve.

This study was designed to more clearly define the relation between various invasive hemodynamic measurements and left ventricular (LV) timing intervals, ejection rate and filling rate derived from the radionuclide angiographic volume curve. Twenty-eight patients were studied with simultaneous intracardiac micromanometer pressure and dP/dt recordings, gated radionuclide angiography and M-mode echocardiography. These techniques permitted multiple variables of systolic and diastolic function to be measured at a constant atrial paced rate of 100 beats/min. There was a strong correlation between peak ejection rate and ejection fraction (r = -0.97) and between peak ejection rate and maximum positive dP/dt (r = -0.85). There also was a strong correlation between peak filling rate and maximum negative dP/dt (r = -0.85). A weaker correlation existed between the time constant of LV relaxation and the peak filling rate (r = -0.49) and between the LV end-diastolic pressure and the peak filling rate (r = -0.62). There was no correlation between the modulus of chamber stiffness and filling rates, and no association was observed between the time to peak filling rate and the hemodynamic variables. Thus, under the conditions studied, the measured peak ejection and filling rate, determined from the radionuclide angiographic volume curve, correlated well with accepted invasive hemodynamic measurements.

Adult↗
PubMed1984

The noninvasive localization of ventricular pacing sites by radionuclide phase imaging.

This study was designed to investigate the potential role of radionuclide angiographic phase imaging in defining ventricular pacing sites. Twenty patients were paced from multiple right ventricular and left ventricular sites. Ten patients had both normal wall motion and normal electrocardiograms (ECGs), while 10 patients had segmental wall motion abnormalities and/or bundle branch block. Both continuous pacing and premature ventricular stimuli were performed. Multiple (two to three) views of each pacing site were obtained by radionuclide angiography and the ventricular site was determined by subsequent phase imaging. Simultaneous 12-lead ECGs were also obtained. The phase-imaging technique accurately localized all 35 right ventricular and 21 of 25 (84%) left ventricular sites to a specific segment. Statistically, this localization ability was independent of baseline wall motion or conduction system disease. In addition, sites as close as 1.5 cm were identified. The 12-lead ECG distinguished left ventricular from right ventricular pacing sites in all patients. Segmental localization by ECG in the right ventricle was accurate in 24 of 35 (69%) and in the left ventricle in 17 of 25 (68%). Thus, radionuclide angiographic phase imaging provides excellent descriptive information regarding the focus of ventricular pacing ectopy and can define both sites of continuous pacing and intermittent premature ventricular stimulation. These findings provide a basis for further assessment of the role of phase imaging in the evaluation of patients with spontaneous ventricular ectopy.

Bundle-Branch Block↗
PubMed1984

Chronic oral amrinone therapy in congestive heart failure: a double-blind placebo-controlled withdrawal study.

Eighteen patients with congestive heart failure were studied in a double-blind, randomized, placebo-controlled withdrawal trial to evaluate the effectiveness of chronic oral amrinone therapy when added to conventional heart failure therapy. All patients received a four-week lead-in of amrinone 100 mg orally every 8 h, then were randomly assigned to either continued amrinone (nine patients) or placebo (nine patients) groups. Compared to placebo, chronic amrinone therapy did not significantly improve clinical status, left ventricular function as measured by non-invasive testing techniques, or exercise tolerance. Side-effects occurred in every patient receiving amrinone and abated in those patients who received placebo for the last 12 weeks of the study. The limited effectiveness of oral amrinone and the high frequency of side-effects preclude the widespread use of this drug in the chronic therapy of congestive heart failure.

Administration, Oral↗
PubMed1983

Amrinone therapy for congestive heart failure in outpatients with idiopathic dilated cardiomyopathy.

Amrinone, 100 mg orally every 8 hours, was administered to 13 patients with moderate-to-severe congestive heart failure (CHF) for 1 month on an outpatient basis to determine the beneficial and undesirable effects of this new cardioactive agent in this clinical setting. These subjects received conventional CHF medications during the course of study. Ten patients who received conventional CHF medications alone served as a control group. Changes in functional classification were not significantly different between the 2 treatment groups. Amrinone augmented exercise capacity 37% above baseline compared with a 12% improvement for the control group. Noninvasive indexes of resting left ventricular function (echocardiography and systolic time intervals) did not change significantly for either group, nor was there a significant change in the exercise ejection fraction. All patients treated with amrinone had greater than or equal to 1 symptom-related or laboratory-detected adverse effect. An increase in the frequency of ventricular ectopic beats was noted at rest in 4 and with exercise in 6 patients (salvos of nonsustained ventricular tachycardia in 2). Six subjects treated with amrinone had gastrointestinal symptoms and 8 developed a viral-like illness. Other adverse effects noted in the amrinone-treated group included near-syncope, headaches, marked anxiety, chest pain, palpitations, maculopapular rash, hypokalemia, and elevation of serum transaminase levels. The control patients had significantly fewer adverse effects. Although individual patients with CHF may benefit from long-term amrinone therapy, the low benefit-to-risk-adverse effect ratio does not warrant widespread application of this drug in the outpatient management of CHF and requires caution when prescribing.

Aminopyridines↗
PubMed1983

Assessment of left ventricular pressure-volume relations using gated radionuclide angiography, echocardiography, and micromanometer pressure recordings. A new method for serial measurements of systolic and diastolic function in man.

This study was designed to validate the use of combined invasive and noninvasive methods in assessing serial pressure-volume relations in man. Ten patients undergoing cardiac catheterization were studied with simultaneous intracardiac micromanometer pressure recordings, gated radionuclide angiography and echocardiography. Systolic and diastolic function were measured at rest, during right atrial pacing rates of 100 and 120 beats/min and after nitroglycerin administration. Right atrial pacing studies (rate of 100 beats/min) were performed in duplicate to determine the reproducibility of the method. At the conclusion of each study, the model was validated with contrast angiography. Good reproducibility was evident when measuring the maximum and average filling and ejection rates, time to peak filling rate, ejection fraction, the modulus of chamber stiffness, the time course of left ventricular relaxation, global average stress and ventricular work indexes using the model described above. These data were not significantly different (p greater than 0.05) from comparable data obtained from contrast angiography. Right atrial pacing and nitroglycerin administration resulted in predictable alterations in the pressure-volume loop and in the systolic and diastolic measurements. The maximum and average filling rates, ejection rates and time to peak filling rate appeared to be heart rate-dependent variables. By combining available invasive and noninvasive methods, accurate pressure-volume relationships can be determined. Because the method we tested provides accurate volumetric and timing measurements for cardiac events and does not alter hemodynamics, it may be useful for obtaining serial assessments of the pressure-volume relationship in man.

Adult↗
PubMed1983

Repolarization variant vs acute pericarditis. A prospective electrocardiographic and echocardiographic evaluation.

Patients with ECG nonischemic ST segment elevation were prospectively studied to determine the accuracy of the initial ECG diagnoses. Evaluations were made of 131 consecutive patients by serial clinical, ECG, and echocardiography to establish a diagnosis. Eighty-six (66 percent) had an initial ECG interpretation of repolarization variant. Only three of the 86 (3 percent) subsequently met clinical criteria for acute pericarditis. Analysis of the mean frontal ST segment vector and PR segment depression revealed no significant differences between the 119 patients with final clinical diagnosis of repolarization variant and the 12 with clinical acute pericarditis. The diagnostic reliability of the initial ECG alone as a means of confirming acute pericarditis is low (9/45, 20 percent) but in the detection of repolarization variant is extremely high (83/86, 97 percent).

Acute Disease↗
PubMed1982

Anatomic and prognostic implications of an early positive treadmill exercise test.

Eighty men (group A) with clinical coronary artery disease underwent coronary angiography regardless of symptoms and previous therapy because they had a positive treadmill exercise test in stage I or II of the Bruce protocol. Thirty-four other men (group B) who also had an early positive treadmill test underwent coronary angiography because they had disabling angina pectoris despite medical therapy. We found left main coronary artery stenosis of 50% or greater of the vessel diameter in 28% of group A and 35% of group B (p greater than 0.3). In contrast, only 10% of 93 other catheterized patients who had treadmill tests that were not early positive had left main coronary disease (p less than 0.001). Fifty-four patients from group A who did not have left main stenosis of 50% or greater were treated medically. In this subgroup, 85% had 2 or 3 major coronary vessels with 75% or greater stenosis. These patients had a 36 month survival rate of 89.2%. We conclude that an early positive treadmill test identifies patients who have an increased likelihood of having left main coronary stenosis, even if they are minimally symptomatic. To identify left main coronary stenosis, catheterization may be justified in patients whose angina pectoris has been mild or not intensively treated when they have an early positive treadmill response. After left main coronary stenosis has been excluded, these patients may be treated medically with a low mortality.

Adult↗