Frequency of occurrence of cytomegalovirus and Chlamydia pneumoniae in lymphocytes of atherosclerotic patients.

Forty-three blood samples from atherosclerotic donors and 28 samples from normal individuals were analyzed to determine the frequency of occurrence of cytomegalovirus (CMV) and Chlamydia pneumoniae DNA sequences in lymphocytes of Saudi Arabian donors using Polymerase Chain Reaction (PCR). In non-atherosclerotic donors, no CMV DNA was detectable and only one sample was positive for C-pneumoniae DNA sequences. Of the 43 atherosclerotic patients, 22 were infected with CMV, 23 were infected with C-pneumoniae and 11 showed no infection. Thirteen of the 43 donors showed simultaneous infection with both CMV and C-pneumoniae. These results demonstrate that atherosclerotic patients are more frequently infected with CMV or C-pneumoniae or both.

Changes in serum concentrations of markers of myocardial injury following treadmill exercise testing in patients with suspected ischaemic heart disease.

BACKGROUND: The treadmill exercise test (TEST) is frequently used in patients with suspected ischaemic heart disease to establish a diagnosis and estimate future risk. However, its predictive value is poor. We aimed to investigate whether measurement of biochemical markers of myocardial injury could improve the diagnostic value of the procedure. MATERIAL AND METHODS: Twenty-four subjects with suspected acute coronary syndrome underwent a treadmill exercise stress test. Of these 13 had had a previous myocardial infarction and two had a past history of coronary artery bypass grafting. Nine subjects were found to be positive for coronary ischaemia during the treadmill test. Serum cardiac markers (total creatine kinase [CK], CK-MB, Troponin I and Troponin T) were measured pre-TEST, and 0, 1, 2, 4, 8 and 24 hours following the treadmill test. RESULTS: Total CK remained within the reference range for all subjects and showed no significant rise. However, mean serum concentrations of CK-MB were significantly higher than pre-test values at 2 hours (p < 0.03) following treadmill exercise testing in subjects who had a positive exercise stress test, but not in those with a negative test. In the subjects with a positive stress test, CK-MB levels returned to pre-Test value by 24 hours. Levels of neither serum troponin I, nor troponin T altered significantly at any point. CONCLUSION: The measurement of CK-MB, but not cardiac troponins may add to the diagnostic utility of the TEST.

Identification of a hypoperfused segment in bull's-eye myocardial perfusion images using a feed forward neural network.

Artificial neural networks are computer systems which can be trained to recognize similarities in patterns and which learn by example; one of the more straightforward types being the feed forward neural network (FFNN). We previously reported the use of FFNNs for classification of hypoperfusion patterns in bull's-eye representation of 201Tl single photon emission tomography myocardial perfusion studies and showed that, when such an image was divided into 24 segments, FFNNs could detect perfusion defects without direct comparison to a normal data base. This has been extended in this investigation to assess the ability of an FFNN, trained on data in which only a single segment was hypoperfused, to detect this abnormal segment when the hypoperfusion pattern of the other segments in the image varied. The results indicated that the network could reliably determine whether a segment was normally or under perfused, with accuracies of 99% and 100%, respectively, if all other segments were normally perfused. It could also reliably detect a normally perfused segment, even if other segments were hypoperfused, with accuracies of 95% and 98%. The network was less reliable, however, in detecting a hypoperfused segment when other segments were also hypoperfused, showing accuracies of only 74% and 88%.

A feed forward neural network for classification of bull's-eye myocardial perfusion images.

Identification of hypoperfused areas in myocardial perfusion single-photon emission tomography studies can be aided by bull's-eye representation of raw counts, lesion extent and lesion severity, the latter two being produced by comparison of the raw bull's-eye data with a normal data base. An artificial intelligence technique which is presently becoming widely popular and which is particularly suitable for pattern recognition is that of artificial neural network. We have studied the ability of feed forward neural networks to extract patterns from bull's-eye data by assessing their capability to predict lesion presence without direct comparison with a normal data base. Studies were undertaken on both simulation data and on real stress-rest data obtained from 410 male patients undergoing routine thallium-201 myocardial perfusion scintigraphy. The ability of trained neural networks to predict lesion presence was quantified by calculating the areas under receiver operating characteristic curves. Figures as high as 0.96 for non-preclassified patient data were obtained, corresponding to an accuracy of 92%. The results demonstrate that neural networks can accurately classify patterns from bull's-eye myocardial perfusion images and detect the presence of hypoperfused areas without the need for comparison with a normal data base. Preliminary work suggests that this technique could be used to study perfusion patterns in the myocardium and their correlation with clinical parameters.

Inter-beat changes in left ventricular function with cardiomyoplasty as measured using MUGA scanning.

Dynamic cardiomyoplasty is a new surgical technique that uses electrically stimulated skeletal muscle to partially replace or reinforce the heart muscle in the treatment of advanced heart failure. Clinical experience with cardiomyoplasty is limited, which has precluded definitive conclusions about its value. We have studied the effect of cardiomyoplasty on the heart muscle when the skeletal muscle was being stimulated to coincide with alternate natural beats. The left ventricular function was assessed using radionuclide angiography during the beat immediately following skeletal muscle stimulation and during the beat immediately before stimulation. When the supported beat is compared with the unsupported beat, the results demonstrate that cardiomyoplasty improves the global and regional ejection fraction. The regurgitation index remains unchanged. The systolic peak emptying rate improves but the diastolic peak filling rate worsens. This latter finding provides additional information regarding the diastolic function of the heart following cardiomyoplasty, which is presently not well understood.