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Biomedical subjects

V F Froelicher

Publications and source records attributed to V F Froelicher.

At least 127 records · Page 7Linked to original sources
PubMed1981

Rest and exercise electrocardiograms and radionuclides in patients presenting for cardiac rehabilitation.

The rest and exercise ECG, 201thallium myocardial scintigram (201T1), and radionuclide ventriculography are noninvasive procedures which can be used to evaluate myocardial damage and ischemia. To compare these procedures and to obtain baseline information, 85 male patients with coronary heart disease were evaluated prior to beginning an exercise program. Findings at rest included Q waves or bundle branch block in 54%; 47% had 201T1 redistribution defects and 33% an abnormal ejection fraction (EF). Of the 39 patients with normal ECGs, 31 had no 201T1 defects and only of these 31 (3%) had an abnormal EF. Abnormal EF or 201T1 redistribution defects did not occur in patients without a history of myocardial infarction. Abnormal resting EF occurred in 63% of patients with abnormal versus 7% of those with normal 201T1 redistribution scans. Exercise test results included an abnormal ST-segment response in 80%, an abnormal EF response in 65%, and a 201T1 ischemic defect in 37%. Twenty patients had exercise-induced ST elevation, and this phenomenon was more related to ventricular aneurysms than to ischemia. 201Thallium imaging, radionuclide ventriculography, and the ECG provide results regarding myocardial damage that agree by more than chance, while the exercise induced ST-segment changes did not agree with the radionuclide indications of exercise-induced ischemia.

Adult↗
PubMed1981

Progress in computer analysis of the exercise electrocardiogram.

The potential advantages of digital computer processing of exercise electrocardiographic data include reduction of noise, compression of data, improved precision and application of optimal criteria. Most prior approaches to such processing required equipment that was both expensive and inconvenient. With the revolution in instrumentation brought about by the development of microcomputers, powerful dedicated computers can now be afforded by many exercise laboratories. There are many approaches to computerized management of exercise electrocardiographic data and various criteria for ischemia. Studies are necessary to validate computer algorithms so that these devices can be used diagnostically to best advantage. Cardiologists need some understanding of this field so that they can be discriminating users of computer systems. In addition, the results of studies correlating electrocardiographic changes with radionuclide methods of assessing myocardial perfusion and function should enable such assessments to be made from the electrocardiographic signals alone, particularly when aided by computer analysis of spatial shifts.

Angina Pectoris↗
PubMed1981

Variations in normal electrocardiographic response to treadmill testing.

Forty healthy young men at low risk for coronary artery disease underwent progressive maximal treadmill testing. Four bipolar electrocardiographic leads including CM5, CC5, inferior-superior Y, anterior-posterior Z, and a standard V5 were recorded and later computer-processed. Measurements included amplitudes of the Q, R, S, J junction and T wave, R-T and Q-S intervals and S-T segment slope. These variables are presented as the 10th, 50th (median) and 90th percentiles throughout the testing procedure to define reference values for the electrocardiographic response to maximal treadmill testing. The medians are presented graphically so that the exercise-induced changes can be visualized. In addition, the percent change of R wave amplitude in V5 compared with the supine pretest value is displayed for each subject during and after testing.

Adult↗
PubMed1981

The relationship between exercise-induced R wave amplitude changes and QRS vector loops.

The mechanism for R wave amplitude changes during exercise testing is controversial. To investigate this, we recorded vectorcardiograms (VCG) during supine rest and bicycle exercise in 13 normals and 33 patients with coronary heart disease. In all normals, and in those CHD patients with an exercise-induced decrease in R wave amplitude, there was a posterior shift of the QRS vector loop in the transverse plane. In the CHD patients with an increase or no change in R wave amplitude, there was an anterior shift of the QRS vector loop. Though spatial vector length decreased with exercise and correlated with R wave changes, there was a better correlation between changes in the maximal QRS vector angle and R wave amplitude. The etiology of R wave changes during exercise appears to be mainly due to shifts in QRS vector loops, but the reason for these shifts is unknown.

Adult↗
PubMed1980

Detection of latent coronary stenosis in conscious dogs: regional functional and electrocardiographic responses to isoprenaline.

A conscious animal model was developed in which coronary stenosis could be produced while regional myocardial function and local surface electrocardiograms were measured. Responses to isoprenaline stress in the presence of mild (latent) coronary stenosis were then examined. In the absence of coronary stenosis, isoprenaline produced increases in regional function and no change in the surface VCG; at higher doses, increases in the endocardial ST segments occurred. After partial coronary stenosis, which produced no apparent regional dysfunction or electrocardiographic changes, isoprenaline infusion for 3 min (0.02 microgram . kg-1 . min-1) rapidly produced decreases in percentage wall thickening (average 17 +/- 4%, mean +/- SE, P < 0.01) and increases in the mean sum of VCG ST segments by 0.23 +/- 0.06 mV (P < 0.05). 1 min after stopping isoprenaline, most dogs showed further significant deterioration of both measures of ischaemia, but by 5 min there was no significant mean change from control. We conclude that in the presence of latent partial coronary stenosis, stress due to mild sympathomimetic stimulation alone can rapidly induce regional myocardial ischaemia. Deterioration of regional myocardial contractile function during such stress can provide as sensitive means of detecting latent coronary obstruction.

Animals↗
PubMed1980

Comparison of rest/exercise ECG, thallium-201 scans and radionuclide angiography in patients with suspected coronary artery disease.

The results of rest and exercise ECG, 201Tl myocardial perfusion imaging and equilibrium radionuclide angiography were analyzed in 71 consecutive patients referred for diagnosis or evaluation of coronary artery disease (CAD). In 45 patients the diagnosis was established either by catheterization or typical history. In this group the overall sensitivity for rest/exercise ECG was 66%, for 201Tl scans 74%, for both combined 79% and for the ejection fraction response to exercise determined by radionuclide angiography 97%. If only the exercise response was considered, the corresponding sensitivity values were 58% (ECG), 50% (201Tl scans), 71% (ECG + 201Tl) and 97% (radionuclide angiography). The specificity for coronary artery disease was determined to be 71% for ECG, 86% for 201Tl scans and 42% for radionuclide angiography. All patients with false-positive results by radionuclide angiography had cardiomyopathies, thus this test has a high specificity for left ventricular dysfunction rather than for CAD alone. Criteria developed from the analysis of the test results in the 45 patients with definite diagnoses were then applied to the evaluation of 26 additional patients with atypical chest pain. A diagnosis could be made in all but 5 of them and radionuclide angiography was again the single most reliable test. Based on this study a new approach for the noninvasive evaluation of patients with suspected coronary artery disease is proposed.

Angiography↗
PubMed1980

An introduction to the applications, methodology and interpretation of exercise electrocardiography.

Exercise testing is a very valuable tool in clinical practice since it has many applications including diagnosis, screening, evaluating treatment and for the determination of prognosis and severity of disease. Its methodology has been varied but comparisons of methodology have been performed that make it possible to obtain comparable information from almost any method of testing. The addition of microprocessors to medical instrumentation and the use of nuclear imaging can improve exercise testing. Exercise testing also play an important role in cardiac rehabilitation and in the prescription of exercise for apparently healthy individuals.

Computers↗
PubMed1980

Does exercise protect from coronary artery disease?

New studies support a lifestyle of regular physical activity. Regular physical activity most likely decreases one's risk for coronary heart disease and helps to decrease other risk factors. The inclusion of regular moderate exercise in one's life-style makes good sense for many reasons. It can improve the quality of life by avoiding illness and the quality is definitely improved in those in whom physical performance is important. Some say that physical exercise will increase the quantity of life but the extra years gained are spent exercising.

Activities of Daily Living↗