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Biomedical subjects

N D Greyson

Publications and source records attributed to N D Greyson.

At least 19 recordsLinked to original sources
PubMed1992

Patients with symptomatic ischemia have larger thallium perfusion abnormalities and more adverse prognosis than patients with silent ischemia.

OBJECTIVE: To evaluate the mechanism for silent ischemia and the effect on prognosis. DESIGN: To test the hypothesis that patients with silent (compared with symptomatic) ischemia have less severe ischemia and a more favorable prognosis, the authors prospectively evaluated 152 consecutive patients with a positive exercise electrocardiogram with exercise thallium scintigraphy and followed them for two years. SETTING: Tertiary care university-based hospital. RESULTS: Asymptomatic patients during the exercise test had a greater exercise duration (9.4 +/- 3.1 versus 6.3 +/- 2.5 mins, P < 0.01), maximal heart rate (155 +/- 20 versus 136 +/- 20 beats/min, P < 0.01), systolic blood pressure (184 +/- 21 versus 176 +/- 23 mmHg, P < 0.05) and double product than patients who were symptomatic with chest pain. Although there was no difference in the magnitude of ST depression, time to ST depression was greater in the asymptomatic (5.6 +/- 2.7 mins), compared with symptomatic (4.6 +/- 2.6 mins), group (P < 0.01). Thallium ischemic score was smaller during asymptomatic ischemia (2.1 +/- 2.7) compared with symptomatic ischemia (3.9 +/- 3.1, P < 0.01). These findings were also demonstrated in a subgroup of 107 patients with both a positive exercise electrocardiogram and positive thallium scan. The patients with asymptomatic ischemia had a two-year cardiac event rate of 5.1% compared with 13.8% in the symptomatic patients (P = 0.065). CONCLUSIONS: Patients with asymptomatic ischemia have less severe myocardial ischemia and a better prognosis than patients with symptomatic myocardial ischemia during exercise testing.

Angina Pectoris↗
PubMed1991

A bullseye display of regional perfusion of the brain.

The authors submit a method of viewing Tc-99m HMPAO SPECT images of the brain based on the principles of the myocardial bullseye or polar mapping. Commercially available software for the production of a myocardial bullseye display is suitable for the preparation of a bullseye display of regional perfusion image of the brain. This display facilitates the detection of cerebral cortical perfusion defects by displaying all SPECT oblique slices concentrically from base to vertex in a single image.

Brain↗
PubMed1990

Long-term results of bipolar arthroplasty in osteoarthritis of the hip.

Bipolar arthroplasty of the hip was introduced by the first author in 1974. From that time until 1988, this type of arthroplasty has been carried out in 1213 hips at the authors' institution. Included is a group of 760 osteoarthritic hips on which follow-up studies have been done at six months, five years, ten years, and 15 years. Studies of the acetabulum show healthy bone preservation as long as 15 years after surgery. A process of floor reinforcement in certain states has also been identified. The relatively simple operative technique has resulted in few postoperative complications. Clinical results as long as 15 years postsurgery compare favorably with two-piece replacement techniques.

Acetabulum↗
PubMed1989

Role of resting thallium201 perfusion in predicting coronary anatomy, left ventricular wall motion, and hospital outcome in unstable angina pectoris.

We performed quantitative thallium scintigraphy in 66 unstable angina patients, 5.6 +/- 5.1 hours after rest pain, to predict coronary anatomy, left ventricular wall motion, and hospital outcome. Thallium defects and/or washout abnormalities were present in 5 of 10 (50%) patients with coronary stenoses less than 50%, 27 of 33 (82%) patients with coronary stenosis greater than or equal to 50% and no history of previous myocardial infarction, and in 23 of 23 patients (100%) with histories of previous infarction. Defects were uncommon in the territory of vessels with less than 50% (13 of 61, 21%), but significantly more common in the territory of vessels with greater than or equal to 50% stenosis (57 of 137, 42%), p less than 0.005. With the addition of washout abnormalities to defect analysis, sensitivity for detection of coronary stenoses improved to 67% (92 of 137), p less than or equal to 0.005, but specificity fell to 59% (36 of 61), p less than 0.01. Segmental wall motion abnormalities were less common in segments with normal perfusion (21%) or in those with washout abnormalities alone (19%), than in segments with thallium defects (45%, p less than 0.005). Defects in patients with previous infarction were common in both segments, with normal (26 of 66, 40%) or abnormal (24 of 45, 53%) wall motion. Eleven of 18 patients with in-hospital cardiac events, but no history of myocardial infarction, had resting thallium defects, whereas only 8 of 25 patients without cardiac event had thallium defect (p = 0.056).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1989

Clinical and laboratory features of acute sulfur dioxide inhalation poisoning: two-year follow-up.

We present clinical and laboratory results (including nuclear imaging) obtained over a period of two years in two nonsmoking miners who were exposed to high concentrations of sulfur dioxide (SO2) after a mine explosion. Within 3 wk of the accident, both miners had evidence of severe airways obstruction, hypoxemia, markedly reduced exercise tolerance, ventilation-perfusion mismatch, and evidence of active inflammation as documented by positive gallium lung scan. Serial ventilation-perfusion scans over the first 12 months showed progressive improvement without returning to normal. After the initial recovery, there has been no significant change over the subsequent two years postinjury. Pulmonary function and exercise tests also displayed a similar pattern of initial improvement. We conclude that (1) acute exposure to high concentrations of SO2 results in severe airways obstruction, (2) pulmonary function abnormalities are partially reversible, and (3) most of the improvement occurs within 12 months after the initial injury.

Accidents, Occupational↗
PubMed1989

"Kirlian photography" film artifacts.

A film artifact due to static discharges from the fingers is described. These are similar to Kirlian photographs, ostensibly representing the radiant spiritual aura.

Diagnostic Imaging↗
PubMed1987

Cardiovascular effects of positive pressure ventilation in humans.

Pulsus paradoxus is the pathological exaggeration of the normal transient decrease in arterial blood pressure that occurs during spontaneous inspiration. The transient increase in arterial pressure associated with positive pressure inspiration is termed reversed pulsus paradoxus (RPP). Cardiorespiratory interactions and the mechanism of these effects have been studied extensively in animals, and to a lesser extent, in humans. In this clinical investigation pulsus paradoxus and RPP were studied in 10 postoperative cardiac patients with invasive monitoring and mediastinal pressure catheters placed intraoperatively. From end-expiration to end-inspiration, RPP was accompanied by decreased transmural pressures in the right atrium, left atrium, and aorta. Left ventricular end-systolic volume measured by radionuclide studies diminished during a positive pressure inspiration, without a significant change in end-diastolic volume. These results are consistent with decreased left ventricular afterload as the major mechanism of RPP. During spontaneous breathing, inspiration was associated with converse effects, a fall in arterial pressure and an increase in transmural right atrial, left atrial, and aortic pressures from end-expiration to end-inspiration. End-systolic volume was significantly larger at end-expiration than end-inspiration, with no change in end-diastolic volume. These findings suggest that an increase in left ventricular afterload during inspiration is responsible for the observed pulsus paradoxus.

Blood Pressure↗
PubMed1987

Acute unilateral pulmonary nonventilation due to mucous plugs.

Acute bronchial obstruction by mucous plugs may be manifested clinically by dyspnea, hypoxemia, and respiratory alkalosis mimicking pulmonary thromboembolism. In eight cases with complete interruption of ventilation to an entire lung, chest radiography failed to reveal the extent of the obstruction. Perfusion was substantially less affected than ventilation. Routine ventilation-perfusion scintigraphy with technetium-99m DTPA aerosol aids in the diagnosis of acute major bronchial obstruction in patients with suspected pulmonary thromboembolism.

Acute Disease↗
PubMed1978

Radionuclide test for gastric bile reflux.

The authors conducted a study using radioactive endogenous bile to detect gastric bile reflux in healthy volunteers and patients suspected of having bile gastritis. When 7 muCi of pyridoxylideneglutamate of hydroxyiminodiacetic acid labelled with technetium-99m is injected intravenously it is excreted by hepatocytes, and sequential gamma camera images visualize the bile ducts and show subsequent activity in the gut. Following such an injection, the authors determined the presence of isotope-labelled bile in the stomach in fasting subjects by assaying count rates in serial gastric aspirates obtained by means of a nasogastric tube positioned in the antrum. The results were related to the clinical history and gastroscopic findings. In normal persons only extremely low counts were detected, possibly due to free activity; high counts (in excess of 50 000/min) indicated abnormal reflux. It is suggested that this test is a useful adjunct, and is more physiologic than endoscopy, in the assessment of bile reflux.

Bile↗
PubMed1977

Delayed imaging to distinguish bone lesions from urinary tract activity.

In 28/1,400 patients examined by bone imaging two hours after injection of 99mTc-polyphosphate or diphosphonate, it was found that activity in the urinary tract obscured the bony pelvis, making assessment of this region difficult or impossible. In several patients additional images were obtained 24 hours after the injection when decreased activity in the urinary tract allowed the pelvis to be more satisfactory visualized.

Aged↗
PubMed1977

Sophisticated radiology in otolaryngology. I. Diagnostic imaging: roentgenographic (x-ray) modalities.

Conventional radiography is now complemented by a large range of newer radiologic diagnostic techniques, involving both roentgenographic and non-roentgenographic modalities. It is the purpose of this presentation to present these new roentgenographic modalities in graphic form, and demonstrate their application to otolaryngic diagnosis. The major roentgenographic modalities which will be stressed are: xeroradiography, angiography, and computerized tomographic scanning.

Adolescent↗
PubMed1977

Sophisticated radiology in otolaryngology. II. Diagnostic imaging: non-roentgenographic (non x-ray) modalities (ultrasound, nuclear medicine, thermography).

Newer forms of radiologic diagnostic imaging now include non-roentgenographic modalities such as ultrasound, nuclear medicin, and thermography, all of which can be applied to otolaryngology. It is the purpose of this presentation to demonstrate these modalities, and indicate their clinical application, yet in its earliest stages, to otolaryngology.

Adult↗
PubMed1976

Serial bone-scan changes in recurrent bone infarction.

Recurrent bone infarcts in a black man produced a changing pattern of bone-scan abnormalities. Areas initially cold at the infarction site returned to normal over a period of months. Hyperconcentration was frequently noted during the healing phase. In the acute phase scanning was specific and more sensitive than radiography.

Adult↗