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Biomedical subjects

A J Roberts

Publications and source records attributed to A J Roberts.

At least 145 records · Page 8Linked to original sources
PubMed1979

Perioperative myocardial infarction associated with coronary artery bypass graft surgery: improved sensitivity in the diagnosis within 6 hours after operation with 99mTc-glucoheptonate myocardial imaging and myocardial-specific isoenzymes.

The present study was performed to evaluate scintigraphic imaging with technetium 99m-labeled glucoheptonate and serum enzyme levels of creatine phosphokinase isoenzyme (MB-CPK) in the early diagnosis of perioperative acute myocardial infarction associated with saphenous vein bypass graft operations. Myocardial imaging was done in 27 patients (50% of whom were considered high-risk) before operation and again 5 hours after operation. Four of these patients (15%) had both electrocardiographic and serum MB-CPK evidence of acute myocardial infarction, and all 4 had developed positive postoperative scintigrams. Four other patients had only elevated serum MB-CPK, and scintigrams became positive after operation in 3 of them. In addition, serum MB-CPK 6 hours after operation was 83 +/- 21 mIU/ml (mean +/- standard error of the mean) in patients with positive postoperative scans compared with 24 +/- 5 mIU/ml in those patients with negative postoperative scintigrams (p less than 0.001). Myocardial imaging with 99mTc-glucoheptonate in the perioperative period is rapid, safe, and atraumatic. Furthermore, our results suggest that it is a sensitive method for the early diagnosis of perioperative acute myocardial infarction, and, when imaging is combined with serum MB-CPK isoenzyme analysis, the reliability of the diagnosis of acute myocardial infarction is enhanced even further. Only 1 of the patients who showed perioperative myocardial damage had acute hemodynamic compromise or obvious impairment of recovery in the immediate postoperative period, and the 30-day mortality of the total group was 4% (1 of 27).

Acute Disease↗
PubMed1978

Role of delayed intraaortic balloon pumping in treatment of experimental myocardial infarction.

Intraaortic balloon pumping improves coronary blood flow characteristics while simultaneously reducing myocardial oxygen demands by reducing aortic systolic pressure. Clinical application of intraaortic balloon pumping has largely been in the "high risk" patient (cardiogenic shock, postinfarction angina, left main coronary artery disease and unstable angina) for support during diagnostic studies or cardiac surgery, or both. In addition, there is some evidence that balloon pumping immediately after coronary occlusion reduces the size of experimentally induced myocardial infarcts. In this study, myocardial infarcts were produced by ligation of the left anterior descending coronary artery in 12 dogs, 6 of which were treated with balloon counterpulsation beginning 3 hours after coronary occlusion. All dogs were killed 8 hours after coronary ligation. Intraaortic balloon pumping resulted in the expected hemodynamic changes (decreased aortic systolic pressure, left ventricular end-diastolic pressure and heart rate and increased aortic peak diastolic pressure). In addition, there was a significant reduction in infarct size in the group with balloon pumping as determined with epicardial S-T segment mapping, myocardial imaging with technetium-99m-glucoheptonate and histochemical staining with nitroblue tetrazolium. These results suggest that even when instituted as long as 3 hours after coronary occlusion, intraaortic balloon pumping results in significant reduction in infarct size and, it might be speculated, the mortality and morbidity associated with acute myocardial infarction may also be decreased.

Angina Pectoris↗
PubMed1978

Early quantification of experimental myocardial infarction with technetium-99m glucoheptonate: scintigraphic and anatomic studies.

Recent advances in understanding of the pathophysiology of myocardial necrosis indicate the need for a noninvasive method that will allow detection and quantification of infarcts in the first few hours after the onset of infarction. Myocardial infarct scintigraphy using technetium-99m glucoheptonate is capable of detecting infarction in dogs and man within 4 to 6 hours of onset. Studies were performed in 45 dogs with acute myocardial infarction: 28 with with an anterior infarct, 5 with an inferior infarct, 6 with an anterior infarct studied after infusion of mannitol and 6 with ligation of the left anterior descending coronary coronary artery and reperfusion of the ischemic area. The dogs were given 20 m Ci of technetium-99m glucoheptonate 1 hour after coronary occlusion, subjected to imaging 5 to 9 hours later and then killed. The experiments revealed that (1) scintigraphic infarct size correlated with infarct weight for anterior (r = 0.85) and inferior (r = 0.88) infarcts; (2) technetium-99m glucoheptonate also concentrated in a rim of myocardium around the infarct that probably represented the ischemic zone; and (3) technetium-99m glucoheptonate uptake by infarcted myocardium could be greatly increased with mannitol and reperfusion.

Animals↗
PubMed1978

Evaluation of methods for the quantification of experimental myocardial infarction.

Several invasive and noninvasive techniques used in determining the size of experimental myocardial infarction were evaluated after acute ligation of the left anterior descending (LAD) coronary artery in ten dogs. Systemic blood pressure, left ventricular end-diastolic pressure (LVEDP), and heart rate did not change significantly for up to 24 hours after coronary occlusion. Left ventricular wall motion abnormalities were detected by left ventriculography in the distribution of the LAD but these changes did not correlate well with the infarct weight determined at autopsy. On the other hand, the number of epicardial sites with ST-segment elevation of greater than or equal to 2 mm (mean 15.1 sites +/- 0.6 SEM) and the infarct area as measured by 99mTc-glucoheptonate (TcGH) myocardial imaging (15.7 sq cm +/- 0.6) did correlate strongly with the infarct weight (16.8 g +/- 0.7) determined by the nitroblue tetrazolium (NBT) technique (r = 0.91). TcGH myocardial scintigraphy and epicardial ST-segment mapping allowed early and accurate quantification of experimental myocardial infarcts ranging from less than 1 g to 28 g.

Animals↗
PubMed1978

Hypertension following coronary artery bypass graft surgery: comparison of hemodynamic responses to nitroprusside, phentolamine, and converting enzyme inhibitor.

Sustained systemic hypertension (mean arterial pressure 119 +/- 4 mm Hg) developed in 39 patients undergoing coronary artery bypass graft (CABG) surgery. In groups of patients with comparable mean arterial pressure, left ventricular filling pressure, heart rate, and cardiac output, treatment with sodium nitroprusside (NP) in 20 patients, phentolamine (PH) in 10 patients and nonapeptide converting enzyme inhibitor (CEI) in nine patients uniformly lowered mean arterial pressure by 26, 21, and 20%, respectively. Cardiac output increased during NP (5.7 +/- 0.1 to 6.4 +/- 0.3 L/min, P < 0.0005) and after CEI (5.7 +/- 0.4 to 7.4 +/- 0.5 L/min, P < 0.0005) but not after PH (5.7 +/- 0.3 to 5.9 +/- 0.3 L/min, P > 0.05). Left ventricular filling pressure decreased in all groups (P < 0.005), but heart rate increased during NP (91.3 +/- 2.4 to 98.4 +/- 2.2 beats/min, P < 0.0005 and after PH (95.5 +/- 2.1 to 99.2 +/- 3.0, P < 0.005), while it was unchanged after CEI P > 0.05). Of the nine patients with CABG hypertension who received CEI, seven exhibited a mean decrease in arterial pressure of 18.5 +/- 3.4%, while in the remaining two patients, mean arterial pressure was decreased only 3.4%. In the former, the pretreatment mean plasma renin activity (PRA) was 7.5 +/- 2.4 ng/ml/hr, while in the latter, mean PRA was 1.3 ng/ml/hr.

Adult↗
PubMed1977

Systemic hypertension associated with coronary artery bypass surgery. Predisposing factors, hemodynamic characteristics, humoral profile, and treatment.

Systemic hypertension occurs in more than one third of patients having coronary artery bypass graft (CABG) operations. This report describes our studies in 100 consecutive patients undergoing CABG. We found that certain preoperative clinical, angiographic, and biochemical factors predispose to the development of perioperative hypertension. These included a well-documented history of hypertension, an elevated blood pressure the day prior to operation, greater than 50 percent obstruction of the left main coronary artery, and increased levels of dopamine beta hydroxylase (DBH). The hemodynamic pattern of perioperative hypertension was that of an increased systemic vascular resistance which was associated with increased levels of plasma catecholamines and plasma renin activity (PRA). Nitroprusside was shown to be effective in managing CABG hypertension, although other, more specific therapy may be preferable.

Adult↗
PubMed1977

Early diagnosis of myocardial infarction in the dog with 99mTc-glucoheptonate.

Early gamma imaging of acute experimental myocardial infarcts was evaluated in mongrel dogs with 99mTc-glucoheptonate. From 15 to 20 mCi were injected between 1 and 27 hr after coronary artery occlusion. Nine dogs imaged 3 hr after injection (4 hr after occlusion) showed unequivocal uptake in the region of the infarct. Fifteen dogs imaged 5-7 hr after injection (6-8 hr after occlusion) showed sufficiently well-defined regions of abnormal uptake so that planimetry could be performed reliably. Five animals imaged serially showed improvement of the image only up to about 5-7 hr after injection. Infarct-to-normal myocardium and infarct-to-blood ratios were slightly higher in dogs injected 15-27 hr after infarction than in those injected 1 hr after infarction, implying that equally good results can be obtained with injection and imaging of 99mTc-glucoheptonate at any time within the first day. No other infarct-labeling radiopharmaceutical shares this capability for the early detection a delineation of acute infarcts.

Acute Disease↗