Biomedical subjects
S A Orr
Publications and source records attributed to S A Orr.
Total coronary occlusion in chronic coronary artery disease.
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Myocardial infarct extension: prevalence, clinical significance, and problems in diagnosis.
To examine the prevalence, clinical significance, and problems in the diagnosis of myocardial infarct (MI) extension, 103 patients with acute MI were studied. Each patient underwent enzymatic infarct sizing in the initial 72 hours and then had quantitative CK-MB (myocardial isoenzyme of serum creatine kinase) analysis at 8-hour intervals over the remaining hospitalization. In addition, daily standard 12-lead ECGs and documentation of prolonged (greater than 15 minutes) resting ischemic chest pain were recorded. MI extension, by CK-MB methods, occurred in 32 (31%) of 103 patients at 5.9 +/- 0.3 days after initial infarction. ECG changes suggesting MI extension occurred in 14 (14%), but only six of these patients had extension by CK-MB. Similarly, recurrent chest pain following initial MI occurred in 28 (27%), but enzymatic extension was evident in only 11 of these patients. MI extension resulted in significantly greater early in-hospital mortality (16%) compared to those patients without MI extension (2.8%, p less than 0.05). Thus MI extension occurs commonly and may explain some early in-hospital deaths post MI. The usual clinical and ECG diagnostic parameters utilized are insensitive indicators of enzymatic MI extension.
Spontaneous changes in thallium-201 myocardial perfusion imaging after myocardial infarction.
To examine regional myocardial perfusion after myocardial infarction, 26 patients underwent exercise electrocardiographic testing with thallium-201 myocardial perfusion imaging 3 weeks and 3 months after infarction. At 3 weeks, 9 of 26 patients (35%) had myocardial ischemia by exercise electrocardiographic testing, whereas 18 of 26 (69%) had ischemia by thallium-201 imaging. The thallium-201 scintigrams were scored by dividing each image, in 3 views, into 5 segments, using a 5-point scoring scheme. The exercise thallium-201 score was 44.3 +/- 1.2 and increased to 47.3 +/- 1.2 in the redistribution study (p less than 0.001). Three months after infarction, although there was a significantly greater rate-pressure product which would predict a larger ischemic defect and a decrease in the stress thallium-201 score, the stress score was improved (48.3 +/- 1.1, p less than 0.001). The redistribution score was similar, that is, 48.9 +/- 1.0. The improvement in thallium-201 myocardial perfusion was associated with a loss of stress-induced ischemia in 8 patients (30%). These results indicate that spontaneous improvements in thallium-201 myocardial perfusion imaging may occur after myocardial infarction.
Coronary disease progression and its effect on left ventricular function.
To determine the effect of coronary disease progression on left ventricular function, 47 patients who had two cardiac catheterizations at a mean interval of 25 months (range three to 92 months) without intervening surgery were studied. Of these, 35 patients had coronary disease and 12 patients had normal or near normal coronary arteries. Coronary disease progression was seen more often in patients with initial coronary disease than in those without significant disease (66 percent vs 25 percent, p less than 0.02). Left ventricular ejection fraction decreased in patients with coronary disease progression (0.63 +/- 0.03 to 0.51 +/- 0.04, p less than 0.01) but was unchanged in patients without progressive disease (0.58 +/- 0.04 to 0.57 +/- 0.93, p = NS). Interval myocardial infarction was the major cause of deteriorating left ventricular function. The rate or degree of coronary disease progression did not predictably change global left ventricular function, and progressive disease in individual vessels did not predictably alter regional left ventricular function. The presence or development of collateral vessels did not significantly alter ventricular performance.