Compartmental multivariate analysis of exercise ECGs for accurate detection of myocardial ischaemia

An accurate computer-assisted diagnostic method for detection of myocardial ischaemia, called MUSTA, is developed. MUSTA is based on compartmental multivariate analysis of variables available in the exercise ECGs, and is definitively implemented in Prolog. It is heuristically developed by determining diagnostic criteria, which interrelate a modified ST/HR-slope, ST-segment value and shape, and maximum heart rate, so that concordance with the Tl-201 SPECT is maximised. In the learning group consisting of 47 patients, MUSTA provides a diagnostic accuracy of 98%, the detection of ischaemia being in absolute concordance with Tl-201 SPECT. MUSTA is evaluated in a similar but independent group of 60 patients. Then, accuracy is 90%, and sensitivity is 94%. The performance characteristics are significantly better than those of the standard exercise ECG, whose diagnostic accuracy in these groups is 77% and 70%, respectively. This study suggests that MUSTA is a significant improvement for computerised assessment of myocardial ischaemia.     

Early exercise thallium-201 single photon emission computed tomography in unstable angina: a prospective study.

To evaluate the safety and diagnostic value of early symptom-limited exercise electrocardiography (ECG) and exercise thallium-201 single photon emission computed tomography (SPECT) in unstable angina (UA), 39 patients were studied prospectively soon after stabilization on medical treatment. No patient had a history of myocardial infarction (MI) or revascularization and patients with left bundle branch block were excluded. Exercise ECG and exercise thallium-201 SPECT were performed 8 +/- 4 days and 11 +/- 6 days respectively after admission to hospital. Seventeen out of 39 patients (44%) had positive exercise ECGs and 22 (56%) negative or inconclusive ones. Exercise thallium-201 SPECT was positive in 26 patients (67%) and negative in 13 patients (33%). Thirty-one patients underwent coronary arteriography and 24 of them proved to have significant coronary artery disease (CAD). The sensitivity, specificity and positive predictive value of exercise ECG in detecting CAD are 62%, 86%, and 94% respectively while the corresponding results are 96%, 100%, and 100% for exercise thallium-201 SPECT. Therefore, it is concluded that the early symptom-limited exercise test is safe in medically stabilized patients with UA. Early exercise thallium-201 SPECT is highly sensitive and predictive of the presence of significant CAD among patients in the early recovery phase of UA and can be used in selecting this group of patients for coronary angiography and other therapeutic strategies.     

Differentiation of malignant from benign pancreatic mass by Tl-201 abdominal SPECT.

The aim of the present study was to evaluate the ability of Tl-201 abdominal SPECT to differentiate between chronic focal pancreatitis and pancreatic malignancy. Seventeen patients (12 men, 5 women; mean age, 56 years; 9 pancreatic cancer, 8 chronic pancreatitis) with pancreatic mass were prospectively investigated with Tl-201 abdominal SPECT. In all patients, CT and/or US could not clarify the nature of the pancreatic mass. Focal hot uptake was present in 8 of 9 patients with pancreatic cancer, while it was present in 2 of 8 patients with chronic pancreatitis. Therefore, the sensitivity and specificity of the present study were 89% and 75%, respectively. A significant difference of Tl-201 uptakes was noted between benign and malignant masses (p < 0.05). Therefore, we concluded that Tl-201 abdominal SPECT was a useful test in differentiation of malignant from benign pancreatic mass, especially when the differentiation could not be made by other imaging modalities.     

A new method to quantify postexercise ST-deviation--the ST-deficit. A study in men at high and low-risk for coronary heart disease.

BACKGROUND: Quantitative heart rate adjusted exercise ST criteria like microV/beats per minute (bpm) improve the diagnostic accuracy of the exercise ECG. However, there are few quantitative HR adjusted postexercise variables available. The aim of the present exercise study was to evaluate a new such variable from computerized averaging of the postexercise ECG. METHODS: The presence of possible myocardial ischaemia in a population based sample of 74 elderly male hypertensives at high-risk of coronary heart disease, and in 42 age-matched clinically healthy males (reference group) at low-risk was assessed by exercise ECG. All men had a normal resting ECG without signs of ischaemia. Variables studied: standard ST-criteria, ST/HR slope < or =-2.4 microV. bpm-1, shape of the rate-recovery loop, the latter also with a new quantitative variable, the ST-deficit. RESULTS: In spite of a normal resting ECG many subjects showed an abnormal ST/HR slope during exercise, 43% in the hypertension group and 26% in the reference group. An abnormal rate-recovery loop (ST-deficit) also contributed substantially to identify patients with possible myocardial ischaemia, 30 vs. 10%, respectively (P<0.02); cumulatively for the two HR adjusted criteria 53% vs. 29%, respectively (P<0.02). Mean ST-deficit was significantly lower in the high-risk group. CONCLUSIONS: Effort-related myocardial ischaemia is frequently silent in elderly high-risk hypertensives and necessitates testing, preferably with computerized exercise ECG and heart rate adjusted ST criteria. A new quantitative variable to assess the postexercise rate-recovery loop in the time domain, the ST-deficit is described. This variable seems to effectively discriminate between subjects with low and high-risk for coronary heart disease and thus provides new information. Further studies are warranted to validate this variable against myocardial perfusion scintigraphy and coronary angiography.     

Dipyridamole thallium-201 perfusion imaging for the study of ischemic heart disease in hemodialysis patients

To assess the usefulness of dipyridamole thallium perfusion imaging in the evaluation of myocardial perfusion in hemodialysis (HD), we studied 29 HD patients divided into three groups: A) 13 patients with clinical angina, B) 8 patients without angina but similar in age, sex, time on HD and hematocrit and C) 8 young asymptomatic patients (mean age 33 +/- 9.7 years). Dipyridamole thallium-201 (Tl-201) perfusion imaging revealed myocardial perfusion defects in 8 patients (61%) from group A, 4 (50%) from group B and 1 (12.5%) from group C. These defects were localized in the inferior, posterior and septal segments of the left ventricle. Abnormal myocardial perfusion was associated with age over 50 years and aortic calcifications (p less than 0.05). Eight patients died within the following four years. All had aortic calcifications (p less than 0.001). Our results show that myocardial perfusion defects are frequent even in non-symptomatic HD patients. This suggests that ischemic heart disease could be more frequent than estimated by clinical symptoms alone. Tl-201 scintigraphy may be a useful non-invasive procedure in cardiological evaluation of HD patients.     

Thallium-201 myocardial scintigraphy during dipyridamole-induced coronary hyperaemia. First experiences with a new regional washout programme

Eight patients with severe peripheral vascular atherosclerosis scheduled for abdominal aortic surgery were investigated to detect coexisting coronary artery disease. None of the patients had a history of angina pectoris or previous myocardial infarction. Preoperative computerised thallium-201 dipyridamole myocardial scintigraphy was abnormal in all patients, showing either myocardial scar tissue and/or ischaemia with redistribution and/or low washout. In all but one patient, the serum level of creatin kinase was elevated during the first postoperative days. In two patients, the serum concentrations of aspartate aminotransferase and lactate dehydrogenase were elevated. None of the patients showed clinical or electrocardiographical signs of acute myocardial infarction. Thallium-201 dipyridamole myocardial imaging is a new noninvasive method for detection of ischaemic heart disease in patients with severe peripheral atherosclerosis who are unable to perform a bicycle exercise test. The new programme for determination of regional washout appeared to be very precise and may be especially applicable in the case of low washout values.     

99-m technetium (Dupont Cardiolite) investigations in postinfarction patients with Holter-checked silent ischaemia.

Sixteen middle-aged, normotensive, slightly overweight male patients with previous myocardial infarction were studied during Holter-checked silent myocardial ischaemia. As reference, stress and late 201-T1 scintigraphy served for comparison with Cardiolite-MIBI silent ischaemic perfusion scan, both carried out in planar mode. The circumferential profiles differed in 9 cases, on region of interest basis the segment number difference was 10, but the late distribution segment number was near to both ischaemic numbers. The quantitative scores were distinctive (ratio 133-128/103) indicating the silent ischaemia appeared in the peri-infarct area. The silent ischaemic MIBI and stress 201-T1 ischaemic score difference was reduced by means of repeated SPECT investigation. With gated radionuclide ventriculography there was -4.3% difference between the left ventricular ejection fractions, measured with first pass MIBI technique during silent ischaemia and afterwards in basal state. The impairment of the left ventricular function was reflected on the stroke pattern of our Holter-based radiocyclogram, as well. Taking the 43.7-48.0 = -4.3% "ischaemic shift" into consideration it was a close correlation (r = 0.90) between the two kinds of ejection fraction determination. The major rhythm failures (occurring during the 24 h Holter monitoring) decreased to a higher degree the left ventricular ejection fraction than silent ischaemia or silent ischaemia and minor rhythm failure together (38-42-50%).     

Differentiation of thyroid nodules using Tl-201 scintigraphy quantitative analysis and fine-needle aspiration biopsy

We studied the differentiation of thyroid nodules using fine-needle aspiration biopsy (FNA) and Tl-201 scintigraphy quantitative analysis. One-hundred and thirty-one thyroid nodules were examined: 83 follicular lesions (58 benign and 25 malignant lesions) and 48 non-follicular lesions (8 benign and 40 malignant lesions). During Tl-201 scintigraphy examinations, an early and a delayed image were acquired 10 and 120 min after an intravenous injection, respectively. The T/N ratio (counts of nodular lesion/counts of contralateral normal thyroid tissue) of each image was calculated quantitatively. We assessed the ability of the Tl-201 scintigraphy and of the FNA analysis to differentiate benign and malignant lesions and determined the cut-off levels for the assays. For the follicular lesions, the area under the ROC (Receiver Operating Characteristic) curve (Az) for the Tl-201 scintigraphy data was greater than that for the FNA data. For the non-follicular lesions, the Az for the FNA data was greater than that for the Tl-201 scintigraphy data. We set cut-off levels at 1.370 for follicular lesions, and 1.070 for non-follicular lesions. The sensitivity and specificity were 76% and 82.7% for follicular lesions, and 90% and 87.5% for non-follicular lesions, respectively. The overall accuracy of the analysis was 84.0%.     

Localization of mediastinal parathyroid adenoma by Tl-201 scintiscan and SPECT

Summary A 64-year-old female patient was admitted to our department for fatigue, pain in the right upper abdomen, obstipation, and meteorism. The laboratory findings showed total calcium and ionized calcium elevated, phosphate close to lower limit, and parathyroid hormone increased. Tl-201/Tc-99m subtraction scintiscan of the neck and upper mediastinal region did not give any evidence of isolated enhanced uptake suggesting the presence of parathyroid adenoma. After further increases in calcium and parathyroid hormone level Tl-201 whole-body scan and single photon emission computed tomography of the thoracic region were performed. These revealed a circumscribed Tl-201 uptake in the mediastinum immediately cranial ventral to the heart base. The postcontrast transmission computed tomography of this area confirmed the finding of the Tl-201 scintigraphy with a 4×3×2 cm tumor. After sternotomy and surgical removal of the mediastinal parathyroid adenoma (chief cell adenoma), calcium and parathyroid hormone levels returned to normal values.Abbreviations Ca total calcium - Ca²⁺ ionized calcium - DSA digital subtraction angiography - hPTH human parathormone - MBq mega-Becquerel - mg milligram - MRI magnetic resonance imaging - mval millival - Ph phosphate - pmol picomol - RIA radioimmunoassay - SPECT single photon emission computed tomography - Tc-99m technetium 99m - TCT transmission computed tomography - Tl-201 thallium 201     

Metabolic changes during exercise testing of patients with ischaemic heart disease

Summary Nineteen patients who had recovered from a mild to moderately severe myocardial infraction 6–18 months previously were studied in order to investigate the relationship between the severity of myocardial insufficiency and metabolic changes developing during and after exercise. The patients were compared with six controls by means of a graded exercise test on a treadmill. Electrocardiographic records were made and blood pressure measured during and after the exercise and venous blood samples were taken for measurement of lactate, pyruvate, glycerol and free fatty acids. In five patients with moderate or advanced ischaemic electrocardiograph changes the blood lactate and pyruvate mean concentrations continued to rise up to a further 50% after they stopped exercising. The other patients, including some who developed symptoms suggestive of myocardial ischaemia, and all the controls, failed to show these marked increases in blood concentrations after the exercise.We conclude that the development of myocardial insufficiency during exercise is associated with marked increases in lactate and pyruvate concentrations in the peripheral blood particularly after the exercise has ceased.     

The sensitivity of the symptom angina pectoris as a marker of transient myocardial ischaemia in chronic stable angina pectoris

Therapeutic decisions in patients with angina pectoris are traditionally based on the history reported by the patient, since objective evidence of myocardial ischaemia during daily life is often not available. In this study, ambulatory ST segment monitoring was performed in 60 patients with a history of chronic stable angina pectoris, positive exercise test and/or positive coronary angiography, and a correlation was made between the episodes of chest pain and ST segment change. The patients were grouped according to the results of exercise testing and coronary arteriography, and one group was studied with and without antianginal medication. Overall, 195 episodes of angina were noted, only 94 of which (48%) were accompanied by ST segment depression. Pain and ST segment changes were best correlated in patients with a positive exercise test, positive angiography and who were not receiving antianginal medication. In 101 episodes of chest pain, ST segment change could not be identified; in 18 (18%) there was sinus tachycardia, in 12 (12%) ventricular premature beats, and in 71 (70%) sinus rhythm solely. Thus, anginal pain appears not to be the reliable indicator of transient myocardial ischaemia as was previously thought, a finding which supports the use of objective methods in identifying episodes of transient myocardial ischaemia in daily life.     

Clinical significance of Tl-201/Tc-99m subtraction scintigraphy as a parameter for surgical indication of cold struma nodules

In a retrospective study Tl-201/Tc-99m subtraction scintigraphy (method acco. to Ferlin et al.) was performed in addition to Tc-99m scintigraphy, sonography and fine needle puncture in 400 patients. Postoperative histological evidence was available of all patients (carcinomas [n = 31], follicular and oncocytic adenomas [n = 235], nodular hyperplasia, Hashimoto's thyroiditis, Riedel's struma and de Quervain's thyroiditis [n = 134]). With regard to possible malignancy the sensitivity, in case of positive Tl-201 uptake was 85%. As however, adenomas also have a high tendency towards isolated Tl-201 uptake, the specificity for malignant growth was 62%. Thus Tl-201/Tc-99m subtraction scintigraphy is well suited as a criterion to exclude thyroid carcinomas; on the other hand, a positive Tl-201 uptake is not a fail-safe indication of malignant processes. At best it suggests the occurrence of autonomous growth and can thus, in addition to sonography and fine needle biopsy, serve as an aid in the decision as to whether surgical intervention is indicated.     

Exercise thallium-201 scintigraphy in the localization of myocardial ischaemia

We performed a retrospective study in order to study the ability of thallium-201 exercise scintigraphy to detect and to localize coronary artery perfusion defects (in comparison with a recent coronary angiogram). We studied 81 patients (67 males); their average age was 52.3 years (men 50.5 and women 54.1 years). They performed a pulse-conducted cycle exercise test, and 2 min before end of exercise 75 MBq of thallium-201 was infused intravenously, and tomographic images were reconstructed by using a Siemens-Rota SPECT gamma camera immediately and 4 h after exercise. The thallium-201 uptake defects were attributed to different coronary arteries, and the results were compared with a coronary angiogram made afterwards in 48 patients. The groups of one-, two- and three-vessel disease were 27, 21, and 21 patients, and only 12 patients did not have significant (over 50%) stenoses. The latter had the highest ejection fraction and working capacity. Sensitivity of thallium-201 exercise scintigraphy was 65%, whereas that of exercise ECG was 41% in patients with a low ejection fraction, while in the whole material the sensitivity of thallium-201 scintigraphy was 91% and that of exercise ECG was 54%. A stenosis in the right coronary artery was best localized by the thallium-201 scintigram (86% correctly); a stenosis in the left anterior descending artery was localized correctly in 75% of the cases, but a stenosis in left circumflex artery was localized correctly only in 44%. We conclude that exercise thallium-201 scintigraphy is a useful method not only in detecting but also in localizing coronary artery disease.     

Problems of Mason-Likar lead system in treadmill exercise electrocardiography

A Mason-Likar (M-L) leads system has been widely used in the exercise electrocardiography (ECG) using treadmill for the detection of myocardial ischemia. In routine treadmill exercise ECG using M-L lead, we often observe different patterns of ST-T forms those of II, III and aVF on bipolar leads. In this study, on 213 patients, conventional 12 lead ECG and the M-L lead placement ECG were recorded both at supine and standing positions. A careful analysis was made on all the records of patterns, durations, and amplitudes of QRS and T waves. We also evaluated the ST trendgram of patients with no ischemic changes proven exercise TI-201 myocardial single photon emission tomography (SPECT). Quantitative examination showed no significant differences between those in precordial leads of the standard and the M-L lead system in any subjects. The augmented amplitude of QRS and T waves, the disappearance of abnormal Q-waves in II, III, aVF lead, the negative inversion in QRS phase in lead aVL an left axis deviation were often recognized with M-L lead placement. In treadmill exercise ECG, ST depression more than 1 mm in II, III, aVF lead was noted 14 out of 17 patients with no ischemic changes. The all ST-T changes showed "not-decrescendo" type in ST trendgram. We concluded that rigorous evaluation for electrical axis, the configuration of ST-T waves and the existence of myocardial ischemia in leads II, III, aVF was necessary on treadmill exercise ECG using M-L lead replacement.     

Evaluation of the membrane attack complex of complement for the detection of a recent myocardial infarction in man

The diagnosis of an acute myocardial infarction (MI) can be cumbersome for pathologists. Even with a positive nitroblue tetrazolium (NBT) reaction, haematoxylin and eosin (H&E) evaluation of the myocardial tissue can remain inconclusive. Early signs presumed diagnostic for myocardial infarction, such as hypereosinophilia, waviness, and contraction band necrosis, have to be considered non-specific and are probably reversible signs of ischaemia. Several studies implicate the complement system, and especially complement factor C9, as part of the membrane attack factor (MAC), in cardiomyocyte damage during MI. In a post-mortem study on well-documented cardiological autopsies, we evaluated the use of complement factor C9 immunostaining as a marker for the detection of very recent MI. Forty-three tissue samples from 40 patients were obtained from the left ventricular free wall only, a region that can be specifically attributed to one corresponding coronary artery. As some patients presented with MIs of various stages in that perfusion area, in total 57 observations were possible. C9 immunostaining specifically detected irreversibly damaged (=infarcted) cardiomyocytes, as is implied by the lytic activity of C9/MAC binding to cell membranes. Most interesting was the group of clinically suspected, NBT-positive MIs resulting from very recent myocardial ischaemia. In this population, where H&E evaluation by (cardio-) experienced pathologists was not conclusive, C9 immunostaining clearly pointed towards myocardial infarction in 47% of the cases. In conclusion, C9 immunostaining, routinely practicable in the pathology laboratory, has an additional value in discriminating between reversible ischaemia and infarcted cardiomyocytes in very early MIs.     

Predicting Breast Attenuation in Patients Undergoing Myocardial Perfusion Scintigraphy: A Digital X-Ray Study

Attenuation artifacts are the most common sources of error in myocardial single-photon emission computed tomography (SPECT) imaging. Breast artifacts are the most frequent causes of false positive planar images in female subjects. The purpose of this study was to predict breast adverse attenuation by measuring breast tissue thickness with digital x-ray. Sixty-five consecutive female patients with angina pectoris, who were referred to myocardial perfusion scintigraphy were enrolled in this study. Eighteen patients with normal perfusion imaging and normal coronary angiography composed the first group, whereas the second group consisted of 28 patients with a positive exercise electrocardiogram with anterior ischemia on myocardial perfusion imaging and greater than 50% left anterior descending artery stenosis on angiography. Nineteen patients in the third group had normal exercise electrocardiograms and normal coronary angiographies, but anterior ischemia on perfusion imaging. Digital x-ray records were obtained for measuring breast tissue thickness and Hounsfield density. The rate of breast adverse attenuation was 40% (19/47) in patients with anterior ischemia. The sensitivity and specificity of the prediction of breast adverse attenuation (lateral density less than 550 Hounsfield) were 79% and 11%, respectively. When breast attenuation for a breast thickness greater than 6 cm measured in the left anterior oblique view was predicted, the sensitivity and specificity were 79% and 93%, respectively. In conclusion, breast thickness greater than 6 cm measured from the left anterior oblique view with digital x-ray can predict breast adverse attenuation in female patients, and thereby may decrease the number of unnecessary invasive diagnostic procedures to be performed.     

Statistical and heuristic image noise extraction (SHINE): a new method for processing Poisson noise in scintigraphic images

Poisson noise is one of the factors degrading scintigraphic images, especially at low count level, due to the statistical nature of photon detection. We have developed an original procedure, named statistical and heuristic image noise extraction (SHINE), to reduce the Poisson noise contained in the scintigraphic images, preserving the resolution, the contrast and the texture. The SHINE procedure consists in dividing the image into 4 x 4 blocks and performing a correspondence analysis on these blocks. Each block is then reconstructed using its own significant factors which are selected using an original statistical variance test. The SHINE procedure has been validated using a line numerical phantom and a hot spots and cold spots real phantom. The reference images are the noise-free simulated images for the numerical phantom and an extremely high counts image for the real phantom. The SHINE procedure has then been applied to the Jaszczak phantom and clinical data including planar bone scintigraphy, planar Sestamibi scintigraphy and Tl-201 myocardial SPECT. The SHINE procedure reduces the mean normalized error between the noisy images and the corresponding reference images. This reduction is constant and does not change with the count level. The SNR in a SHINE processed image is close to that of the corresponding raw image with twice the number of counts. The visual results with the Jaszczak phantom SPECT have shown that SHINE preserves the contrast and the resolution of the slices well. Clinical examples have shown no visual difference between the SHINE images and the corresponding raw images obtained with twice the acquisition duration. SHINE is an entirely automatic procedure which enables halving the acquisition time or the injected dose in scintigraphic acquisitions. It can be applied to all scintigraphic images, including PET data, and to all low-count photon images.     

Localization Value of Magnetoencephalography Interictal Spikes in Adult Nonlesional Neocortical Epilepsy

Few studies have included magnetoencephalography (MEG) when assessing the diagnostic value of presurgical modalities in a nonlesional epilepsy population. Here, we compare single photon emission computed tomography (SPECT), positron emission tomography (PET), video-EEG (VEEG), and MEG, with intracranial EEG (iEEG) to determine the value of individual modalities to surgical decisions. We analyzed 23 adult epilepsy patients with no abnormal MRI findings who had undergone surgical resection. Localization of individual presurgical tests was determined for hemispheric and lobar locations based on visual analysis. Each localization result was compared with the ictal onset zone (IOZ) defined by using iEEG. The highest to the lowest hemispheric concordance rates were MEG (83%) > ictal VEEG (78%) > PET (70%) > ictal SPECT (57%). The highest to lowest lobar concordance rates were ictal VEEG = MEG (65%) > PET (57%) > ictal SPECT (52%). Statistical analysis showed MEG to have a higher hemispheric concordance than that of ictal SPECT (P = 0.031). We analyzed the effects of MEG clustered-area resection on surgical outcome. Patients who had resection of MEG clusters showed a better surgical outcome than those without such resection (P = 0.038). It is suggested that MEG-based localization had the highest concordance with the iEEG-defined IOZ. Furthermore, MEG cluster resection has prognostic significance in predicting surgical outcome.     

Diagnostic capabilities of I-131, TI-201, and Tc-99m-MIBI scintigraphy for metastatic differentiated thyroid carcinoma after total thyroidectomy

We investigated the diagnostic capabilities of I-131, Tl-201, and Tc-99m-MIBI (hexakis-2-methoxyisobutyl- isonitrile) scintigraphy for thyroid cancer metastases after total thyroidectomy over the entire body and for every locus before and after thyroid bed ablation. After total thyroidectomy of thyroid cancer, 36 cases were subjected to I-131 treatment 64 times. They consisted of 17 men and 19 women with 31 papillary carcinomas and 5 follicular carcinomas. Their ages were 22--75(an average of 60.5+/-12.3) years. I-131 scintigraphy(I-131), Tl-201 scintigraphy(Tl-201), and Tc-99m- MIBI scintigraphy (Tc-99m-MIBI) were performed. We defined the metastases as those cases in which serum thyroglobulin (Tg)increased significantly or in which we were able to prove the lesions on CT (computed tomography), MRI (magnetic resonance imaging) or bone scintigram. Three radiology medical specialists visually evaluated each scintigram and calculated the sensitivity, specificity, and likelihood ratio. For whole-body sensitivity, both Tl-201 and Tc-99m-MIBI were high before ablation and I-131 was high after ablation. Before ablation, the negative likelihood ratio was less than 0.1 for Tl-201 and Tc-99m-MIBI, while the positive likelihood ratio was more than 10 for Tl-201. After ablation, the positive likelihood ratio for I-131, Tl-201, and Tc-99m-MIBI was more than 10. The sensitivity of the mediastinum was appropriate, except for I-131 before ablation, and the sensitivity of the lung before and after ablation was inferior for either tracer. The specificity of the cervix for I-131 before ablation was markedly deteriorated, but it increased after ablation.     

Evaluation of T-wave alternans in high-resolution ECG maps recorded during the stress test in patients after myocardial infarction

Introduction

Recent studies point to analysis of T-wave alternans as a promising indicator of an increased risk of life-threatening ventricular arrhythmias. In this study the occurrence of T-wave alternans in the high-resolution ECGs recorded during the exercise stress test and scintigraphic tests (SPECT) in patients with ischemic heart disease was examined.

Material and methods

The study group consisted of 33 patients after myocardial infarction. In the group of patients after myocardial infarction and with low left ventricular ejection fraction correlations of 70% between the test results of T-wave alternans and SPECT and 60% between the test results of T-wave alternans and stress test were found.

Results

In the group of patients after myocardial infarction but with high left ventricular ejection fraction correlations were respectively 39% and 48%. The analysis of the electrocardiographic maps showed a strong dependence of this correlation on the T-wave alternans amplitude and location of the ECG measuring electrode on the chest. The results might suggest that in patients after myocardial infarction and at increased risk for sudden cardiac death T-wave alternans may also provide information about cardiac electrical instability associated with ischemia.

Conclusions

It can also be assumed that the position of the electrode where the highest level of the T-wave alternans was detected can indicate the location of the ischemic region of the heart.