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The advent of computerised electrocardiography has been of prime importance for the storage and retrieval of data, but none of the available systems is of universal application for analysis of patterns. Future needs require hierarchical systems of increasing degrees of complexity, depending on the source of requests, and there should be appropriate provision for review by cardiologists before the final report is issued.
One hundred and forty-nine patients with suspected ischaemic heart disease were evaluated by exercise thallium-201 myocardial scintigraphy (201Tl SMS), single lead exercise electrocardiography, and coronary arteriography. Myocardial distribution of tracer was assessed semi-quantitatively from digital 201Tl scintigrams and compared with tracer distribution in subjects with normal hearts. Fifty-two of 54 (96%) patients with normal coronary arteries had normal myocardial scintigrams whereas three patients had a positive ischaemic exercise electrocardiogram and were scan normal. Conversely, 36 of 95 (38%) patients with coronary artery disease had a positive ischaemic electrocardiogram compared with 94 of 95 (99%) patients who had a positive myocardial scintigram. Disease in specific coronary arteries could be deduced from the topography of myocardial tracer deficit. Disease was predicted correctly in 76 out of 80 (95%) of left anterior descending coronary stenoses, in 48 out of 64 (75%) of right coronary artery stenoses, and in 55 out of 64 (85%) of left circumflex coronary artery stenosis, despite the presence of infarcted myocardium in other territories. Similarly, single vessel disease was predicted correctly in 14 out of 17 (82%) patients and multiple vessel disease in 64 out of 77 (83%) patients. 201Tl SMS with segmental quantitative analysis is a highly sensitive and specific technique in the diagnosis of coronary artery disease and may be useful screening procedure to select patients for further investigation, particularly those with evidence of life-threatening severe left coronary artery disease.
OBJECTIVE: To study the effects of variability in the duration of the QT interval corrected for heart rate (QTc) on the occurrence of sudden death. DESIGN: Nested case-referent study. SUBJECTS: Cohort of 6693 consecutive patients who underwent 24 hour electrocardiography and were followed up for two years. Risk implications of QTc interval variables were studied in patients without evidence of cardiac dysfunction or of an intraventricular conduction defect (104 died suddenly and 201 patients were randomly drawn from the study cohort). MAIN OUTCOME MEASURES: Mean QTc interval duration and variation in QTc duration over time correlated with occurrence of sudden death. RESULTS: Patients with a prolonged mean QTc over 24 hours (> or = 440 ms) had a 2.3 times (95% confidence interval 1.3 to 4.5) higher risk of dying suddenly than patients with a normal mean QTc (400-440 ms); patients with a shortened mean QTc (< 400 ms) also had a higher risk (relative risk 2.4 (1.4 to 4.3)). Patients with low (< 20 ms) and high (> or = 25 ms) long term variation in QTc duration had an increased risk of dying suddenly compared with those with intermediate variation (20-25 ms) (relative risks 2.2 (1.2 to 4.2) and 2.3 (1.4 to 4.2) respectively). The relative risks for low and high short term variation were not significantly raised. CONCLUSIONS: A prolonged and a shortened mean QTc interval over 24 hours was associated with a more than twofold risk of sudden death compared with intermediate mean QTc values (400-440 ms). Neither short nor long term variability in QTc had a distinct relation with the risk of sudden death.
OBJECTIVE: To determine whether the effectiveness of long-term beta blocker treatment for idiopathic dilated cardiomyopathy can be predicted by signal averaged electrocardiography (ECG). PATIENTS: 31 patients with dilated cardiomyopathy and without bundle branch block were included in a retrospective study and 16 in a prospective study. METHODS: A signal averaged ECG was recorded before beta blocker treatment, and three variables were measured from the vector magnitude: QRS duration, root mean square voltage for the last 40 ms (RMS40), and duration of the terminal low amplitude signals (< 40 microV) (LAS40). In the retrospective study, these variables were compared among good responders (showing > or = 0.10 increase in ejection fraction 12 months after start of beta blocker treatment) and poor responders without such improvement. The validity of the signal averaged ECG criteria for prediction of the response to beta blocker treatment was examined in the prospective study. RESULTS: In the retrospective study, good responders (n = 16) had a shorter QRS duration (mean (SD): 122.9 (11) v 138 (14.4) ms, p < 0.005) and LAS40 (33.1 (8.9) v 42.5 (7.8) ms, p < 0.005), and a higher RMS40 (31.6 (16.3) v 19.0 (10.3) microV, p < 0.02) than poor responders (n = 15). Signal averaged ECG criteria for good response were defined as two or more of the following: QRS duration < 130 ms, RMS40 > 20 microV, LAS40 < 40 ms (sensitivity 81%, specificity 73%). In the prospective study, six of seven patients who met these criteria showed a good response to the beta blocker treatment, while eight of nine who did not showed a poor response (chi 2 = 6.1, p < 0.02). The signal averaged ECG criteria gave a sensitivity of 86% and a specificity of 89% for predicting the effectiveness of beta blocker treatment. CONCLUSIONS: A signal averaged ECG might be useful in predicting the effectiveness of beta blocker treatment for dilated cardiomyopathy.
OBJECTIVE: To investigate the accuracy of signal averaged electrocardiography (SAECG) and measurement of microvolt level T wave alternans as predictors of susceptibility to ventricular arrhythmias. DESIGN: Analysis of new data from a previously published prospective investigation. SETTING: Electrophysiology laboratory of a major referral hospital. PATIENTS AND INTERVENTIONS: 43 patients, not on class I or class III antiarrhythmic drug treatment, undergoing invasive electrophysiological testing had SAECG and T wave alternans measurements. The SAECG was considered positive in the presence of one (SAECG-I) or two (SAECG-II) of three standard criteria. T wave alternans was considered positive if the alternans ratio exceeded 3.0. MAIN OUTCOME MEASURES: Inducibility of sustained ventricular tachycardia or fibrillation during electrophysiological testing, and 20 month arrhythmia-free survival. RESULTS: The accuracy of T wave alternans in predicting the outcome of electrophysiological testing was 84% (p < 0.0001). Neither SAECG-I (accuracy 60%; p < 0.29) nor SAECG-II (accuracy 71%; p < 0.10) was a statistically significant predictor of electrophysiological testing. SAECG, T wave alternans, electrophysiological testing, and follow up data were available in 36 patients while not on class I or III antiarrhythmic agents. The accuracy of T wave alternans in predicting the outcome of arrhythmia-free survival was 86% (p < 0.030). Neither SAECG-I (accuracy 65%; p < 0.21) nor SAECG-II (accuracy 71%; p < 0.48) was a statistically significant predictor of arrhythmia-free survival. CONCLUSIONS: T wave alternans was a highly significant predictor of the outcome of electrophysiological testing and arrhythmia-free survival, while SAECG was not a statistically significant predictor. Although these results need to be confirmed in prospective clinical studies, they suggest that T wave alternans may serve as a non-invasive probe for screening high risk populations for malignant ventricular arrhythmias.
Cardiac catheterisation was carried out in 40 patients with thoracic scoliosis in order to measure the pulmonary artery pressure. Statistical correlations were calculated between these results and the electrocardiographic and mechanocardiographic findings determined on a separate occasion. The pulmonary artery pressure was normal in 72% of subjects. It was inversely correlated with arterial oxygen tension but not with the aetiology, severity, or age at onset of the scoliosis. The accuracy of electrocardiography and mechanocardiography in predicting the pulmonary artery pressure was assessed. The closet correlates were found to be a tall P wave in lead II or III and a prolonged interval between pulmonary valve closure and tricuspid valve opening.
Fetal electrocardiography (FECG) in the mare has been investigated by several workers (Holmes and Darke 1968, Kanagawa and others 1967). This short paper seeks to evaluate previous work, present new findings, and provide a practical technique enabling veterinary surgeons to diagnose singleton and twin pregnancies in the latter part of pregnancy.
The authors compared prospective (n = 20) and retrospective (n = 20) electrocardiography (ECG)-assisted multi-detector row computed tomography (CT) with non-ECG-assisted multi-detector row CT (n = 20) of the thoracic aorta with regard to reduction of motion-related artifacts. Image quality was rated for transverse source and sagittal oblique images of the thoracic aorta, including the aortic valve. ECG-assisted multi-detector row CT compared with non-ECG-assisted multi-detector row CT showed a significant reduction in motion artifacts for the entire thoracic aorta.
The authors evaluated a nonenhanced magnetic resonance (MR) angiographic technique that allows separation of arteries from veins. In 15 healthy subjects, peripheral MR angiography was performed with readout flow-spoiled gradient pulses in electrocardiography-triggered three-dimensional half-Fourier fast spin-echo MR imaging. Appropriate flow-spoiled gradient pulses were measured and applied in the three-dimensional acquisition to differentiate arteries and veins in the peripheral vasculature. Subtraction of the diastolic bright-blood arteries from the systolic black-blood arteries allowed visualization of the arteries by cancelling the veins, which are constantly depicted as bright blood throughout the cardiac cycle. Stronger flow-spoiled gradient pulses improved the depiction of slow-flow arteries even in the distal foot and hand vessels.
PURPOSE: To prospectively assess electrocardiography (ECG)-synchronized multi-detector row computed tomography (CT) for the evaluation of right ventricular (RV) function in patients suspected of having pulmonary embolism (PE). MATERIALS AND METHODS: All patients gave informed consent after the study details, including radiation exposure, were explained; institutional ethical committee approval was obtained. Nonsynchronized multi-detector row CT of the chest was performed in 66 consecutive patients (29 men, 37 women; mean age, 58 years+/-15 [standard deviation]) who were suspected of having PE. ECG-synchronized cardiac multi-detector row CT was performed to assess cardiac function. Dimension ratios for the RV and left ventricle (LV) were measured on nonsynchronized transverse and angulated four-chamber views. Furthermore, the RV end-diastolic and end-systolic volumes were measured on ECG-synchronized multi-detector row CT scans. An independent samples t test was performed to compare the mean value of different groups. An analysis of variance post hoc test was performed to investigate whether the values of the variables varied between groups. RESULTS: PE was detected in 29 of 66 patients. The location of PE was categorized as central (n=17) or peripheral (n=12). The RV/LV dimension ratio was larger on the four-chamber view (P=.002), and RV end-systolic volume was larger (P=.01) and ejection fraction was lower (P=.01) in patients with PE. The RV end-systolic volumes and RV/LV volume ratios, as assessed by using ECG-synchronized multi-detector row CT, showed significant differences (P<.005) between patients with central PE and those with peripheral PE. However, the RV/LV dimensions on nonsynchronized images revealed no significant differences. CONCLUSION: Retrospective ECG-synchronized multi-detector row CT facilitates detection of RV dysfunction, depending on pulmonary embolus location.
An electrocardiography (ECG) synchronization technique allowed triggering of 1.5-T echo-planar acquisitions of the heart, with high gradient slew rates. In 51 volunteers (37 men and 14 women, aged 21-48 years), the ECG signal was amplified, filtered, and converted into an optical signal directly above the heart and was transmitted optically outside the bore. Reliable and artifact-free ECG tracings were obtained in all cases, regardless of the gradient switching speed.
The authors developed an electrocardiography-triggered M-mode navigator-echo technique to help monitor cardiac motion and identify the period of minimal cardiac motion in the cardiac cycle. Coronary magnetic resonance angiography was performed in eight healthy adult volunteers and one patient with heart disease. To minimize cardiac motion effects, trigger delays were estimated with the navigator-echo technique and two empirical formulas. The quality of images obtained with the different delay times was compared for clarity of depiction of the coronary arteries. Image quality was best with the delay calculated with the navigator-echo technique.
Definition of QRS onset and offset is a basic problem in electrocardiography. Current techniques rely either on subjective estimates or on computer algorithms using QRS derivative or spatial vector velocity parameters. We developed a spectral method based on the observation that the QRS complex, unlike the P wave, PR segment, or ST-T complex is comprised of significant frequencies greater than 50 Hz. Accordingly, we adapted a microprocessor-based electrocardiograph (ECG) system with a signal-averaging program to reduce noise and a 50-300 Hz digital filter. Leads I and aVF were simultaneously acquired by computer in 40 subjects with a wide range of QRS duration (55.5-161 ms). Excellent correlation (r = 0.98) was noted between high-frequency QRS duration measurement and careful visual determinations made at high gain and expanded time scale. The high-frequency ECG appears to provide an objective physiological definition of the QRS complex based on spectral content not on morphology or slope.
Fetal magnetocardiograms (FMCGs) were recorded in a case of fetal complete heart block (CHB) from the 30th to the 37th week of gestation using the multichannel SQUID system (Hitachi, Japan). M-mode ultrasonography and direct fetal electrocardiography using needle electrodes revealed fetal CHB. We identified independent fetal P-waves and QRS complexes in the FMCG recorded in the 32nd week of gestation when the fetal atriums were close to the FMCG sensor. We also recorded FMCG P-waves in the 37th week of gestation when the fetal heart was larger. Fetal heart position and size are important for obtaining a useful FMCG. To establish FMCG as a diagnostic tool of fetal arrhythmia, comparative studies with FECG are needed.
OBJECTIVE: To demonstrate the coincidence of fetal magnetocardiography (FMCG) and fetal direct electrocardiography (FDECG) in a case of fetal atrial flutter (AF). METHODS: FMCG and FDECG using a fetal scalp electrode were recorded in the case of fetal AF at 41 weeks' gestation. RESULTS: FMCG revealed fetal AF with 2:1 atrioventricular block, which was also documented by FDECG using a fetal scalp electrode. The prenatal diagnosis was confirmed by postnatal electrocardiogram. Neonatal echocardiography revealed an intracardiac tumor on the left atrial septum. The tumor seemed to be the cause of AF. CONCLUSION: FMCG may provide the same information as a fetal electrocardiogram in the prenatal diagnosis of fetal AF.
We tried to assess the efficacy of precordial exercise electrocardiography (PEE) in evaluating various antianginal drugs. PEE was performed by 18 precordial electrodes. Leads V2-V7 were recorded at their usual position and one intercostal space higher and lower. The Bruce treadmill exercise protocol was used. A positivity index (PI) was formulated as follows. The total sum of maximal ST-segment depression (sigma ST reduced) X 100 was divided by the product of the number of precordial leads X minutes of exercise duration: (Formula: see text). The PI was measured basally and after the administration of nitroglycerin (NTG) ointment, 7.5 mg (7 patients), propranolol (P) 20-40 mg, 3 times daily (7 patients) and nifedipine (N), 10 mg 3-4 times daily (7 patients). A significant decrease of the PI was seen with NTG (p less than 0.01) and P (p less than 0.05) but not with N. However, in the N group, 2 patients had a significant increase in heart frequency, with resultant exercise deterioration. The remaining 6 patients had a satisfactory response to the drug (p less than 0.05). The PI is useful in assessing the antianginal efficacy of various medications. From our study it is suggested that inordinate tachycardia may negate the beneficial effect of N in some patients.
Signal-averaged electrocardiography, resting radionuclide ventriculography and Holter monitoring were performed prior to hospital discharge, to assess their value in predicting recurrent cardiac events in 210 survivors of acute myocardial infarction. In addition, 153 of these patients also underwent exercise radionuclide ventriculographic assessment. During median follow-up of 14 months (6-24 months), there were 16 cardiac deaths, 15 patients had recurrent infarction and 7 patients represented with symptomatic ventricular tachycardia. Cox regression analysis identified independent predictors of 'ischemic events' (death or re-infarction) as a previous history of infarction (p = 0.01), Killip class III-IV (p = 0.03) and an abnormal exercise radionuclide study (p = 0.04); and predictors of 'arrhythmic events' (sustained ventricular tachycardia or sudden death) as an abnormal signal-averaged electrocardiograph (p = 0.01) and left ventricular ejection fraction less than 40% (p = 0.03). Patients with an abnormal signal-averaged electrocardiograph and reduced left ventricular ejection fraction had a 34% incidence of arrhythmic events during the first 6 months compared with a 4% incidence among patients without late potentials. In those patients who underwent exercise testing and signal averaging, 85% of total cardiac events and all cardiac deaths were predicted by an abnormality of either noninvasive test. In addition, exercise testing and signal-averaged ECG were independent predictors of outcome. Hence, using a combination of noninvasive tests, patients can be stratified according to the risk of recurrent life-threatening cardiac events after myocardial infarction; such patients may be suitable for intensive investigation and considered for trials involving active intervention.
Twenty-four hour electrocardiography was performed in fifteen 73-year-old and seventeen 82-year-old subjects without known cardiovascular disease. They were selected from a representative population of elderly people. All subjects showed supraventricular premature beats. Supraventricular tachycardia was seen in 63%. Eighty-four percent showed ventricular premature beats (VPBs), and more than two VPB configuration types were seen in 23% of the subjects. Episodes of intermittent atrial flutter and fibrillation, higher-degree atrioventricular blocks and ventricular tachycardia were absent or rare.