Biomedical subjects
Publications and source records attributed to M Pfisterer.
Explore the source record for details and available documents.
To assess the accuracy of serial myocardial perfusion scintigraphy with thallium-201 (201Tl) to predict graft patency early and late coronary artery bypass surgery, rest and exercise 201Tl and coronary arteriography were performed preoperatively and 2 weeks and 1 year after operation. The scintigraphic results were compared with graft patency, symptoms, left ventricular function and physical work capacity in a consecutive series of 55 patients with a total of 154 grafts. Serial 201Tl had an 80% sensitivity, 88% specificity and 86% overall accuracy in detecting or excluding graft occlusion, which was predicted by reversible ischemia as well as persistent "new scar" segments. Occluded grafts were correctly localized by 201Tl scintigraphy in 61%. Postoperative apical 201Tl defects were frequent (two-thirds of cases), and were the result of intraoperative transapical venting of the left ventricle. After coronary bypass graft surgery, ejection fraction at rest was unchanged. Left ventricular end-diastolic pressure and physical work capacity improved significantly. In the presence of new perfusion defects detected postoperatively, physical work capacity was reduced significantly. New 201Tl defects in addition to typical or atypical angina provided a high probability of graft occlusion, while in the absence of new 201Tl defects all grafts were patent in more than 90% of patients, all of whom had no or only atypical chest pain. We conclude that serial 201Tl imaging after coronary artery bypass surgery is an accurate noninvasive method that can be used routinely to assess graft function, to localize spatially occluded grafts and to identify patients with a high likelihood of graft occlusion who may need invasive studies.
Explore the source record for details and available documents.
Prior to diagnostic left heart catheterization, 22 patients with atypical chest pain underwent thallium scintigraphy and radionuclide ventriculography at rest and during exercise. Combining both noninvasive tests, 6/8 patients with coronary artery disease, 3/4 with cardiomyopathies, and 9/10 patients without heart disease were correctly identified. From detailed analysis of the results it is concluded that left heart catheterization should not be necessary if the radionuclide findings are typical of either coronary artery disease (localized perfusion defect and abnormal left ventricular function) or absence of heart disease (normal perfusion and function studies).
Explore the source record for details and available documents.
In a review of the current literature, the importance of physical activity in the primary prevention of coronary heart disease is critically analyzed. The main results concerning a direct protective effect of physical training remain controversial. The problems of such epidemiological studies become apparent. Still, there seems to be evidence that a certain amount of physical activity, particularly during leisure time, has beneficial effects on known coronary risk factors such as high serum triglycerides and free fatty acids, obesity, high blood pressure as well as smoking habits and, thus, may reduce the coronary risk indirectly inducing psychological effects and changes in life-style.
To assess the relation between stress-induced perfusion defects and wall motion abnormalities (WMA), 20 patients were studied by thallium-201 (201Tl) scintigraphy and cineventriculography at rest and during exercise. Of 100 analyzed segments, 63 were normal while 13 showed constant (scar) and 24 reversible (ischemia) perfusion defects. At peak exercise, 85% of the scar and 80% of the ischemic segments corresponded to abnormally contracting wall segments. There was a marked correlation between the extent of ischemia and the degree of WMA. The increase in abnormal scintigraphic and angiographic segments from rest to exercise was parallel by a significant deterioration in left ventricular function. It is concluded that (1) ischemic perfusion defects detected by 201Tl scintigraphy correlate well with exercise induced wall motion abnormalities, and (2) the localization, extent and degree of WMA can be predicted by non-invasive 201Tl scintigraphy.
Combined ECG/myocardial perfusion szintigraphy (MPS) exercise tests were performed in 82 out-patients with suspected CAD who eventually underwent left heart catheterization. The sensitivity of MPS as compared to ECG was higher in patients with angina (86% vs. 67%) as well as in patients with atypical symptoms (63% vs. 25%). Here MPS was also more specific than ECG (86% vs. 68%). Combination of both tests improved sensitivity even more. The comparison of radionuclide and contrast ventriculography in 20 patients studied at rest revealed an excellent correlation (r = 0.90). Changes in radionuclide ejection fraction during exercise in 60 subjects showed significant differences between normals (increase of greater than 10% above resting level) and patients with CAD (decrease in patients with angina, no significant change without angina). Methods and indications are briefly discussed in the light of this experience.
In a critically ill patient referred to an intensive care unit, clinical evaluation remains the first method in the assessment of cardio-circulatory status. In more complex cases direct measurement of standard hemodynamics must be performed at the bedside, for instance by the use of a Swan-Ganz thermodilution catheter. As alternatives to hemodynamic parameters, non-invasive techniques for the evaluation of left ventricular function such as echocardiography, radionuclide angiography, measurement of systolic time intervals and electrical impedance are presented. Their indications and limitations in comparison with hemodynamics are discussed.
To test the value of combining treadmill exercise with radionuclide angiography for detecting exercise-induced left ventricular dysfunction, ejection fractions were calculated at rest, peak supine bicycle exercise, and during three supine post-treadmill recovery periods (2-4 min, recovery 1;4-6 min, recovery 2;8-10 min, recovery 3) in ten coronary artery disease patients and eight normal subjects. Both the normal subjects and coronary artery disease patients had normal resting ejection fractions (greater than 0.50). In the normal subjects the mean ejection fraction increased significantly (p less than 0.005) from rest (0.61 +/- 0.03) to peak supine bicycle exercise (0.71 +/- 0.04), and the mean ejection fraction also remained significantly higher (p less than 0.005) at rest than during 10 min post-treadmill exercise. However, the coronary artery disease patients did not significantly change the mean ejection fractions from rest (0.59 +/- 0.06) to peak supine bicycle exercise (0.55 +/- 0.08), and the average ejection fraction during each one of the post-treadmill recovery periods was not significantly different from rest. At the third recovery period all the normals but no coronary artery disease patients had higher ejection fraction than the resting ejection fraction. We thus conclude that the magnitude of change in ejection fraction from rest to 8-10 min post-treadmill exercise in patients with normal resting ejection fraction may be helpful in identifying those with coronary disease.
A unique case of 'variant' angina pectoris has been observed in a patient with normal coronary arteries and typical chest pain appearing spontaneously at rest, and repeatedly provoked by ergonovine maleate (0.1 mg iv) associated with large transmural perfusion defects on 201Tl-imaging (after ergonovine) and a marked increase in T wave voltage despite no demonstrable spasm of a major coronary artery after the same doses of ergonovine. While saline solution could not provoke chest pain and treatment with a beta-blocking agent increased the frequency of ischemic attacks, a calcium antagonist therapy reduced and eventually eliminated the attacks. Thus, this case provides evidence for yet another aspect of a 'variant' form of angina pectoris: small vessel coronary artery spasm.
Seventy-six patients were studied within one week of contrast ventriculography to assess the influence of differing background assignments on ejection fractions derived from gated equilibrium radionuclide anigograms. "Fixed" and "variable" left-ventricular regions on interest and five different backgrounds were used. Inter- and intra-observer variability were determined, and 15 patients underwent a second study 2 weeks later. Variable left-ventricular regions of interest produced higher ejection fractions than fixed ones. A computer-assigned background or a ring drawn manually around the left ventricle correlated best with contrast ventriculography, giving greater serial and inter- and intra-observer variability. Automated background assignments reduced variability and increased reproducibility, though not always associated with the best correlation with contrast ventriculography. Thus a variety of left-ventricular and background regions of interest gives excellent reproducibility and accuracy.
This paper presents the profiles of left ventricular ejection fraction (EF) during and following supine bicycle exercise in normal subjects and in patients with coronary heart disease, as well as the relationship of the described patterns to clinical parameters. Twenty normal men and 40 patients with coronary artery disease were studied using gated equilibrium radionuclide angiography (EQ-EF). In the normals, during exercise, EF increased by a mean of 25% of the resting value, with an increase of no less than 11%. The exercise-limiting symptom in patients with coronary artery disease was angina pectoris in 20 and fatique in the other 20 patients. In the angina patients, there was a mean decrease in EF of 20%, and in the other coronary artery disease patients ejection fraction change little. Only two patients with coronary artery disease increased from a normal resting value to peak exercise by more than 11%, and they had isolated right coronary lesions. An "overshoot" elevation of ejection fraction above resting levels was demonstrated following termination of exercise in most patients. The patients with a significant fall in exercise ejection fraction more frequently had abnormal exercise-induced ECG changes as well as abnormal left ventriculograms and more severe coronary artery disease at cardiac catheterization than the patients with little change in ejection fraction. We conclude that 1) normals could be separated from most patients with significant coronary artery disease in this study population; 2) ejection fraction must be measured at maximal exercise for it to have diagnostic value, since there could be normal rise before and after peak exercise and an abnormal response missed; and 3) the ejection fraction response to exercise reflects the severity of the underlying coronary artery disease. The described patterns of exercise-induced changes in left ventricular ejection fraction are important to consider when using this new technique to diagnose and evaluate patients with coronary artery disease.
Explore the source record for details and available documents.
To identify abnormal left ventricular function without exercise stress in patients with coronary artery disease first-pass radionuclide angiograms were analyzed in 32 normal subjects (Group I); 31 patients with coronary disease and normal contrast ventriculograms (Group II); and 17 patients with coronary disease and depressed left ventricular function (Group III). Total ejection fraction (EF) was computed with standard angiographic methods and from each time-activity curve. During the first third of systole, ejection fraction was determined manually by averaging three to five beats and the value compared with that obtained with contrast ventriculography: (Formula: see text). Both total radionuclide ejection fraction (r = 0.95) and first-third ejection fraction (r = 0.91) correlated well with angiography. Intraobserver and interobserver variation was small, averaging 0.02 +/- 0.02 (range 0 to 0.05). The radionuclide first-third ejection fraction was 0.25 or greater in normal subjects and less than 0.25 in 29 of 31 patients (94 percent) in Group II and in all patients in Group III. It is concluded that the first-third ejection fraction obtained with first pass angiography identifies subtle abnormalities of left ventricular function at rest in more than 90 percent of patients with coronary disease that may not be recognized by total ejection fraction alone.
The effect of diaphragmatic attenuation on 231Ti images of the heart was studied by intermittent recording with patients in inspiration and expiration. These studies suggest that the commonly observed posteroinferior defects in the left lateral projection can be explained by this mechanism. Possible effects on the anterior view are also suggested.
To validate the repeated use of radionuclide equilibrium angiography for determining left ventricular (LV) ejection fraction (EF) and end-diastolic and end-systolic volumes (EDV and ESV), 25 patients were studied on an hourly basis an average of 9.1 days after acute myocardial infarction. Data were processed with a semi-automatic computer program which develops an averaged-volume curve from an assigned LV region-of-interest. LV EDV and ESV were derived from a previously described method which correlates well with contrast angiography (r = 0.977, y = 0.0255x - 0.121). Comparison between initial and subsequent equilibrium EF and between initial and subsequent volumes showed excellent correlation. Excluding three anginal episodes, the EF variation between studies averaged 0.03 +/- 0.02.
To compare radionuclide end-diastolic (EDV) and end-systolic (ESV) volumes with angiographic volume, we studied 52 patients with equilibrium radionuclide angiography using 99mTc-human serum albumin within 48 hours of contrast angiography. Each RR interval was divided into 20--28 equally timed frames and a time-activity curve generated. End-diastolic counts were taken at the early peak of the curve and end-systolic counts at its nadir. Counts were divided by the total number of processed heart beats and normalized for: 1) dose per body surface area; 2) plasma volume; and 3) counts/ml of plasma. A cardiac phantom was developed and serial volumes were studied using a normalization factor. Radionuclide values were expressed as dimensionless units and compared with either biplane angiographic volumes (in the patient studies) or known phantom volumes. Good correlations were obtained with methods 1 and 2 in 35 patients (r greater than 0.84), but the best correlation was obtained in 17 patients when normalization for counts/ml of plasma was used (r = 0.98; y = 0.255 x -0.121). The standard error of the estimate (SEE) was +/- 11.5 ml for EDV and +/- 7.3 ml for ESV. The phantom study also showed an excellent correlation (r = 0.99), with a SEE of +/- 6.5 ml. We conclude that a radionuclide method independent of geometric assumptions can be used to estimate left ventricular volume in man.