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Biomedical subjects

M J Callahan

Publications and source records attributed to M J Callahan.

34 records · Page 2Linked to original sources
PubMed1989

Myocardial stunning in hypertrophic cardiomyopathy: recovery predicted by single photon emission computed tomographic thallium-201 scintigraphy.

A young woman with hypertrophic cardiomyopathy confirmed by echocardiography and cardiac catheterization presented with chest pain and features of a large left ventricular aneurysm. The initial diagnosis was myocardial ischemia with either an evolving or an ancient myocardial infarction. Subsequently, verapamil therapy was associated with complete resolution of the extensive left ventricular wall motion abnormalities, normalization of left ventricular ejection fraction and a minimal myocardial infarction. Normal thallium uptake on single photon emission computed tomographic scintigraphy early in the hospital course predicted myocardial viability in the region of the aneurysm. Thus, orally administered verapamil may reverse spontaneous extensive myocardial ischemia in hypertrophic cardiomyopathy and possibly limit the extent of myocardial infarction in such circumstances.

Adult↗
PubMed1988

Cardiopulmonary metastatic lesions of osteosarcoma and associated cerebral infarction.

Osteogenic sarcoma frequently disseminates by hematogenous routes. A 32-year-old patient underwent evaluation for an acute cerebral infarction. Cardiac auscultation disclosed an abnormal diastolic sound. Echocardiographic examination revealed a large left atrial mass, which was found at thoracotomy to be metastatic osteogenic sarcoma. Cerebral computed tomographic scans at the time of initial examination and 3 months later demonstrated new cerebral lesions consistent with metastatic growths. The abrupt cerebral infarction, other clinical findings, and results of diagnostic studies strongly suggested that the acute cerebrovascular event was the result of metastatic cerebral embolization from the tumor material found in the thorax. Cerebral infarction is an unusual and catastrophic complication of thoracic metastatic lesions of osteogenic sarcoma.

Adult↗
PubMed1987

Growing familiarity with the test situation augments the vigilance deficit of aged rats.

Quantitative EEG profiles of aged and of young-adult Fisher-344 rats were studied over 10 consecutive recording (3 h) sessions. The individual recording sessions were spaced regularly over a 6-week period. In the aged rats, in recordings from both the frontal cortex and dorsal hippocampus, the EEG characteristics of a vigilance deficit state increased in prominence up through 8 recording sessions before a stable level was reached. A similar trend was not seen in the young-adult rats; instead, these rats showed a stable level of spectral voltage output in both leads over the entire period of the 10 recording sessions. Thus, the aged rat brain appears to suffer from a vigilance deficit state which is revealed most clearly by testing under the basal conditions brought about by thoroughly familiarizing the subjects with the test environment.

Adaptation, Psychological↗
PubMed1987

Evaluation of intraoperative transesophageal two-dimensional echocardiography.

Transesophageal two-dimensional echocardiography (TEE) was evaluated in 11 patients who underwent myocardial revascularization. The TEE transducer was positioned to view the left ventricular (LV) short-axis at the level of the papillary muscles (midcavity). Good quality echocardiographic images were obtainable in ten of 11 patients. Global LV function was assessed by measuring LV end-diastolic and end-systolic area and computing the fractional area change (FAC). Measurements of LV areas and FAC had excellent intraobserver reproducibility. Regional LV function was analyzed in two ways after dividing the short-axis view of the LV into four or five anatomic segments. Systolic wall thickening (SWT) of the myocardium was measured in each of four segments by digitization of the endocardial and epicardial borders of the LV and determining the fractional wall thickening. Measurements of SWT were not reproducible, primarily because of a difficulty in delineating the epicardial border of the LV accurately. In the second method, regional wall motion (RWM) in each of five segments was graded according to a previously developed scoring system. RWM analysis proved to be a measurement with excellent interobserver and intraobserver reproducibility. TEE was performed without complication and found to be a reproducible method for assessing global and regional LV function. Quantitative analysis is tedious and, therefore, currently not available on-line in the operating room.

Echocardiography↗
PubMed1986

Doppler color flow imaging: a new technique for visualization and characterization of the blood flow jet in mitral stenosis.

We used Doppler color flow imaging, a new noninvasive technique for mapping of intracardiac blood flow, to visualize and characterize the blood flow jet in 42 patients with mitral stenosis. Color flow imaging provides information about the direction of blood flow, its velocity, and the presence of turbulence. Although we found various jet configurations, most frequently the jet was centrally and apically directed and had a "candle flame" appearance (a central blue zone surrounded by hues of yellow and orange). The blood flow jet can be used to guide the positioning of the continuous-wave Doppler beam parallel to the blood flow; thus, the accuracy of the Doppler data can be enhanced. This new technology has promising potential for other clinical applications in cardiology.

Adult↗
PubMed1986

Paraneoplastic digital thrombosis: a case report.

Persistent digital ischemia is an uncommon paraneoplastic syndrome. We describe a 71-year-old man whose only manifestation of an underlying adenocarcinoma was digital ischemia. His symptoms responded dramatically to bilateral dorsal sympathectomies. A thorough search for the mechanism producing the ischemia failed to provide an explanation. We assume that unknown neurohumoral factors produced by the tumor were responsible.

Adenocarcinoma↗
PubMed1985

Validation of instantaneous pressure gradients measured by continuous-wave Doppler in experimentally induced aortic stenosis.

The relation between catheter-measured and Doppler-derived aortic pressure gradients was examined in 8 open-chest dogs. A snare was placed around the proximal ascending aorta and adjusted to provide a wide range of gradient to left ventricular (LV) outflow. A continuous-wave Doppler transducer was placed above the level of the obstruction and angled to optimize the audio and spectral signals. Pressure tip transducer catheters recorded LV and ascending aortic pressures simultaneously with the Doppler signal. In 120 randomly selected sinus beats, Doppler-derived maximal gradient correlated well with maximal instantaneous catheter gradient from 4 to 179 mm Hg (r = 0.99). Mean gradients also were closely related (r = 0.98). For gradients above 100 mm Hg, the correlation remained good (r = 0.98), but for gradients below 50 mm Hg, the correlation was not as precise (r = 0.81). All 120 cycles were digitized at 10-ms intervals to examine the correspondence between the Doppler and catheter data throughout systole. For the 2,742 pairs of points so obtained, the correlation was excellent (r = 0.95). The close relation between Doppler-derived pressure gradient and that measured simultaneously by catheterization provides further validation of the use of continuous-wave Doppler in the assessment of aortic stenosis, not only at maximal gradient, but throughout the period of LV ejection.

Animals↗
PubMed1985

Two-dimensional echocardiographically guided pericardiocentesis: experience in 117 consecutive patients.

Pericardiocentesis guided by 2-dimensional echocardiography has been used at the Mayo Clinic since April 1980. The 2-dimensional examination localizes the pericardial fluid. Particular note is made of the place on the body wall closest to the fluid. An entry track that permits puncture of the pericardial sac without damage to any vital structure is then selected for the pericardiocentesis needle. Between April 1980 and March 1984, 132 consecutive pericardiocenteses in 117 patients were done by this technique. The volume of fluid obtained ranged from 75 to 1,700 ml (mean 650). Seventy percent of the taps were done for therapy, 21% for diagnosis, and 9% for both therapy and diagnosis. A Teflon-sheathed "intracath" needle was used to complete 80% of the pericardiocenteses. In the other 20%, a large catheter was secondarily introduced and connected to a closed drainage system. There were no deaths related to the procedure. One symptomatic pneumothorax occurred. There were 3 minor complications. Two-dimensional echocardiographic imaging of the heart and pericardial fluid permits a safe and effective means of performing pericardiocentesis.

Adolescent↗
PubMed1985

Doppler echocardiography: theory, instrumentation, technique, and application.

A Doppler examination is a valuable adjunct to a complete echocardiographic examination. It has the capability of measuring normal and abnormal velocities of blood flow noninvasively. For the first time, this procedure allows noninvasive quantitation of stenotic gradients, intracardiac pressures, and blood flow as well as semiquantitative assessment of regurgitant lesions. With this procedure, the operator must progress through a learning curve in order to gain a complete understanding of the examination techniques, the limitations of the instruments, and the Doppler physics principles before applications can be made to clinical practice. Evaluation of other aspects of Doppler echocardiography, such as color-flow mapping and assessment of diastolic events, portends great promise for the role of this procedure in the future.

Adult↗
PubMed1984

Transient atrioventricular block after open-heart surgery for congenital heart disease.

The records of 22 patients with transient atrioventricular (AV) block after open-heart surgery for congenital heart disease from 1972 to 1978 were reviewed to determine the natural history of this entity. Preoperatively, no patient had AV block; 3 had right bundle branch block (BBB), 1 had left BBB and 5 had nonspecific intraventricular conduction delay. Complete AV block developed in 20 patients and Mobitz II AV block in 2. Transient AV block occurred intraoperatively in 14 patients and within 48 hours postoperatively in 8; AV block persisted for greater than or equal to 48 hours postoperatively in all patients, for a mean of 7.3 days (range 2 to 28). During a follow-up of 5.5 years (range 2.5 to 10), late AV block developed in 2 patients. None of the 18 patients whose escape QRS complex morphology during AV block was similar to the final QRS complex during normal sinus rhythm or atrial fibrillation with AV conduction had late AV block, whereas 2 of the 4 in whom it differed did (p less than 0.01). There was no difference in the escape rate between the 2 groups. Thus, late development of high-grade AV block is infrequent among patients with transient postoperative AV block. An escape QRS complex during postoperative AV block that differs from the QRS complex seen on recovery of normal sinus rhythm or atrial fibrillation with anterograde conduction may identify those at high risk of late AV block.

Adolescent↗
PubMed1984

Noninvasive measurement of cardiac output by continuous-wave Doppler echocardiography: initial experience and review of the literature.

Doppler echocardiographic measurement of the velocity of blood flow in the ascending aorta is a noninvasive method for determining cardiac output in the critically ill patient. Fifty-four patients in the medical intensive care unit (35 men and 19 women, age range 41 to 91 years) in whom a Swan-Ganz catheter had been inserted underwent measurement of cardiac output with use of a commercially available continuous-wave Doppler echocardiographic instrument. The aortic root diameter was measured by A-mode echocardiography. An additional 26 patients (17 men and 9 women, age range 20 to 83 years) who had undergone an open-heart surgical procedure and had hemodynamic monitoring in the postoperative period also underwent Doppler measurement of cardiac output. In these patients, the aortic root diameter was measured directly intraoperatively. Cardiac output was also determined by thermodilution in both groups. An adequate A-mode study was possible in 83% of the medical patients but only 27% of the surgical patients. Doppler signals were adequate in 84% of the medical patients and 92% of the surgical patients. The correlation between thermodilution and Doppler-derived cardiac output was good in both the medical (r = 0.94, SEE = 0.78, P less than 0.001) and the surgical (r = 0.85, SEE = 0.78, P less than 0.001) group. Doppler echocardiography is a promising noninvasive method for determining cardiac output in critically ill patients.

Adult↗
PubMedDate not supplied

PD 142676 (CI 1002), a novel anticholinesterase and muscarinic antagonist.

Inhibition of brain acetylcholinesterase (AChE) can provide relief from the cognitive loss associated with Alzheimer's disease (AD). However, unwanted peripheral side effects often limit the usefulness of the available anticholinesterases. Recently, we identified a dihydroquinazoline compound, PD 142676 (CI 1002) that is a potent anticholinesterase and a functional muscarinic antagonist at higher concentrations. Peripherally, PD 142676, unlike other anticholinesterases, inhibits gastrointestinal motility in rats, an effect consistent with its muscarinic antagonist properties. Centrally, the compound acts as a cholinomimetic. In rats, PD 142676 decreases core body temperature. It also increases neocortical arousal, as measured by quantitative electroencephalography, and cortical acetylcholine levels, measured by in vivo microdialysis. The compound improves the performance of C57/B10j mice in a water maze task and of aged rhesus monkeys in a delayed match-to-sample task involving short-term memory. The combined effect of AChE inhibition and muscarinic antagonism distinguishes PD 142676 from other anticholinesterases, and may be useful in treating the cognitive dysfunction of AD and produce fewer peripheral side effects.

Animals↗
PubMedDate not supplied

Continuous ICV infusion of scopolamine impairs sustained attention of rhesus monkeys.

Systemic administration of anticholinergic agents impairs cognitive performance in animals and man. The anticholinergic, scopolamine, has profound effects on peripheral and central cholinergic function, making interpretation of its effects on cognitive performance difficult. To circumvent this problem, scopolamine was administered directly to the central nervous system of rhesus monkeys using a subcutaneously implanted infusion pump connected to a cannulae directed toward the right lateral ventricle. Intracerebroventricular (ICV) infusion of scopolamine (0.004, 0.012, 12.5, and 40.0 micrograms/kg/h) produced a dose-dependent decrease in the number of responses on a continuous performance task. Response decrements produced by scopolamine were seen mainly during the last half of the test session and at short stimulus durations. These data suggest that scopolamine produces a deficit in sustained attention or slowing of information processing that is mediated through direct central cholinergic blockade in the rhesus monkey.

Animals↗