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Biomedical subjects

P Lavender

Publications and source records attributed to P Lavender.

27 records · Page 2Linked to original sources
PubMed1981

Myocardial ischemia and angina pectoris: the clinical problem in patients.

The morbidity and mortality suffered by patients with coronary artery disease is probably caused by the development of myocardial ischemia. Angina pectoris occurs not only during stress but also at rest and at night. This suggests that myocardial ischemia may be caused by a variety of mechanisms. Ambulatory monitoring of ST segment changes was performed in 60 patients presenting with angina, positive ECG stress tests and coronary artery disease. 85% of ischemic ECG events were asymptomatic, 37% occurred with no increase in heart rate and 15% of episodes either lasted 20 minutes or more or fluctuated in severity. A controlled pilot study in ten patients showed that the combination of high dose propranolol and nifedipine produced a significant decrease in chest pain and episodes of ST depression. Radionuclide studies in 50 patients with angina and coronary artery disease have shown that stress (i.e., atrial pacing) produced different patterns of disturbed regional myocardial perfusion related to the patient's exercise capacity and eventually leading to a decrease in regional myocardial perfusion during the ischemic episode. St segment depression appeared only after the decrease in regional myocardial perfusion. These findings combined with past research suggest that patients with angina and coronary artery disease can suffer frequent asymptomatic disturbances of the regional myocardial perfusion. The frequency of these episodes and the time course for the recovery of the metabolic consequences mean that segments of ventricular myocardium may be constantly abnormal. The relative importance of changes in coronary tone and malfunction of platelets in the diseased coronary tree needs to be examined in clinical research. Pilot studies of antiplatelet agents have shown a significant beneficial effect on episodes of ischemia occurring at night and those occurring without any increase in heart rate. The techniques and observations in these patients with coronary artery disease all suggest that acute transient regional myocardial ischemia is caused by a variety of mechanisms. Further research using objective methods is required to discover the causes of ischemia and to rationalize treatment. f

Angina Pectoris↗
PubMed1979

Autoradiography of technetium-labelled diphosphonate in rat bone.

The passage of technetium-labelled methylene diphosphonate (99mTc-MDP) across rat bone was examined by autoradiography. The autoradiographs showed that shortly after an injection of the bone-seeking agent there was activity outside the bone, within the bone marrow and also adjacent to the highly vascular epiphysial plate; the distribution of the isotope in the incubated bone appeared to be non-uniform, a high concentration being seen adjacent to the epiphysial plate and also on the surfaces of the bone. The evidence suggested that a two-fold mechanism resulted in the uneven distribution of 99mTc-MDP. The first factor probably represented the regional distribution of blood flow with a transcapillary movement of the tracer from the capillary bed to the extravascular space; the subsequent incorporation of the tracer into bone appeared to depend on the nature of the bone matrix.

Animals↗
PubMed1978

The uptake by the canine tibia of the bone-scanning agent 99mTc-MDP before and after an osteotomy.

The residue and extraction of technetium-labelled methylene diphosphonate (99mTc-MDP), a substance used in bone scanning, was examined in the canine tibia and found to be low. Examination of washout curves suggested that there were four compartments in cortical bone, a vascular, a perivascular, a bone fluid and a bone compartment. After an osteotomy in the canine tibia the residue of 99mTc-MDP increased. This was believed to be due to an increase in the blood supply to the bone and to an associated increase in new bone available for exchange. Bone scanning in a fracture is therefore a reflection of the vascular status of the bone being examined and of the uptake by bone. This is dependent on there being an adequate blood supply to the bone and an increased number of mineral-binding sites.

Animals↗