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Objectives: We evaluated inter-reader agreement of the ST-segment between two electrocardiogram (ECG) core laboratories., Background: Accurate measurement of the ST-segment is key to diagnosis and management of acute coronary syndromes (ACS). Clinical trials also rely on adherence to the pre-specified ECG eligibility criteria., Methods: 150 patients (100 ST-segment elevation (STE)-ACS, 50 non-STE-ACS) were selected. An experienced ECG reader from each laboratory measured ST-segment deviation on the baseline ECGs (nearest 0.1mm)., Results: ∑ST-segment deviation showed excellent inter-reader agreement (R=0.965, intraclass correlation coefficient (ICC) 0.949, 95% CI (0.930-0.963)). Similar agreement was observed when ∑ST-segment elevation (∑STE) and ∑ST-segment depression (∑STD) were assessed separately. Better agreement was evident in STE-ACS cohort (ICC (95% CI): 0.968 (0.953-0.978, 0.969 (0.954-0.979), 0.931 (0.899-0.953)) compared to NSTE-ACS patients (ICC (95% CI): 0.860 (0.768-0.917), 0.816 (0.699-0.890), 0.753 (0.605-0.851) across measurement of ∑ST-segment deviation, ∑STE, and ∑STD., Conclusions: We demonstrated excellent agreement on ST-segment measurements between two experienced readers from two ECG core laboratories., (© 2013.)

Background: Symptomatic myopericarditis has been described after smallpox vaccination using replication-competent vaccinia strains., Methods: We examined the incidence of new electrocardiogram (ECG) abnormalities and evaluated the safety and immunogenicity related to vaccination. Volunteer subjects (n=90) aged 18 to 32 years were enrolled in a National Institutes of Health-sponsored phase I smallpox vaccination trial (Division of Microbiology and Infectious Diseases 02-017) and observed over a 26-week period after 2 injections of IMVAMUNE, Modified Vaccinia Ankara vaccine (Bavarian Nordic A/S, Copenhagen, DK), followed by scarification with Dryvax (Wyeth Laboratories, Marietta, Penn). Diagnostic computer-derived ECG statements were available to the clinical study team and compared with those of a board-certified cardiologist who independently read the ECG tracings., Results: Serial ECG tracings available for 89 of the subjects revealed new ST-segment abnormalities in 2.2% and new T-wave abnormalities in 15.7%; the majority (71.4%) resolved on subsequent tracings. Cardiologist over-read of computer statements resulted in frequent changes in readings, particularly negation of cardiac arrhythmias. A cardiology consultation was requested in 17 subjects for nonspecific cardiac symptoms or new abnormal ECG findings. Echocardiograms were performed in 12 of the 17 subjects and were normal except for 1 subject with possible myopericarditis after receiving Dryvax., Conclusion: New minor ECG abnormalities are common in apparently young healthy volunteers considered for smallpox vaccination trials. Cardiologist over-read of computer-generated ECG statements in vaccine trials using ECG as a screening tool for safety can reduce false-positive computer-determined ECG diagnoses and the need for inappropriate cardiology referral and additional noninvasive testing.

An academic 12-lead electrocardiogram (ECG) core laboratory aims to provide the highest possible quality ECG recording, measurement, and storage to aid clinicians in research into important cardiovascular outcomes and to maximize the credibility of scientific results based solely, or in part, on ECG data. This position paper presents a guide for the structure and function of an academic ECG core laboratory. The key functional aspects are: 1) Data collection, 2) Staff composition, 3) Diagnostic measurement and definition standards, 4) Data management, 5) Academic considerations, 6) Economic consideration, and 7) Accreditation. An ECG Core Laboratory has the responsibility for rapid and accurate analysis and responsible management of the electrocardiographic data in multicenter clinical trials. Academic Laboratories, in addition, provide leadership in research protocol generation and production of research manuscripts for submission to the appropriate peer-review journals.

This article examines specific electrocardiographic (ECG) and electrophysiological features of ventricular repolarization in rats and mice, and the role of depolarization-activated potassium currents in mediating the unique features of ECG recordings in these rodents. This article describes the currents that underlie ventricular repolarization in these rodents, identifies terminology that appropriately describes the unique features of murine ECG recordings, and correlates these unique findings with selected human ECG ventricular repolarization abnormalities. The absence of a distinct isoelectric interval between the QRS complex and the T wave, accompanied by a relatively short QT interval, are common features of ECG recordings in mice and rats, but not in ECGs in guinea pigs. The murine ECG morphology is apparently attributable to the presence of large outward K+ currents that dominate the early phase of ventricular repolarization. In rats and mice, the predominant current underlying the early phase of repolarization appears to be the rapidly activating and inactivating 4-aminopyridine-sensitive transient outward current (ie, I(to)). Importantly, the density of I(to) in rats and mice is high, whereas this current is not evident in the ventricular myocytes of guinea pigs. The high density of I(to) appears to underlie the prominent J wave or downsloping ST-segment elevation seen in rats and mice, whereas the ST-segment is isoelectric in guinea pigs. The unusual J wave and ST-segment pattern in murine ECGs, however, does bear some resemblance to ECG features observed in humans with Brugada syndrome, and with hypothermia and ischemia. These patterns in rats and mice might, therefore, serve as an experimental model for the idiopathic J wave.

In this first clinical report of an idiopathic familial persistently short QT interval (QTI), we describe three members of one family (a 17-year-old female, her 21-year-old brother, and their 51-year-old mother) demonstrating this ECG phenomenon, associated in the 17-year-old with several episodes of paroxysmal atrial fibrillation requiring electrical cardioversion. Similar ECG changes seen in an unrelated 37-year-old patient were associated with sudden cardiac death. Our report also describes other manifestations of abnormal shortening of the QTI and considers the possible arrhythmogenic potential of the short QTI., (Copyright 2001 S. Karger AG, Basel)

Right bundle-branch block (RBBB) has not traditionally been seen as an obstacle to ECG diagnosis of Q wave myocardial infarction (MI)--in clinical electrocardiography and vectorcardiography--because this conduction disturbance is not believed to cause significant alterations in the spatial orientation of initial excitation wavefronts. In the era of large-scale clinical trials, however, where serial ECG analysis is among the major diagnostic tools in MI classification, both false-positive and false-negative diagnoses of MI in the presence of RBBB have become increasingly evident. Because of the limited detectability of Q wave MI by ECG in the presence of RBBB, the electrocardiographic finding of Q wave MI should not be regarded as an independent diagnostic tool. It is best to utilize independent corroboration to establish the diagnosis of transmural infarction when RBBB is present. Further investigations are warranted to better delineate sensitivity, specificity, and predictive value of Q wave MI in the presence of RBBB.

It is generally accepted in clinical electrocardiography that a right bundle branch block (RBBB) does not interfere with the electrocardiographic (ECG) diagnosis of myocardial infarction (MI). The basic assumption is that the initial excitation wavefronts are relatively unchanged in RBBB. This study compared serial changes in Q wave duration in inferior leads II, III, and aVF in 9 patients who developed RBBB within 3 weeks after myocardial revascularization procedure (RBBB group) and in 41 revascularized patients without RBBB in the same observation period (control group). Q wave durations in the electrocardiograms obtained before the patients' procedures were not significantly different between the study and control groups. However, Q wave durations shortened significantly more in the RBBB group than in the control group. The most pronounced Q wave duration shortening took place in lead aVF, -18.2 ms in the RBBB group versus -3.8 ms in the control group (P = .0001). The shortening was less pronounced, although significant, in leads II and III: II, -7.6 +/- -10.9 ms in the RBBB group vs -2.3 +/- -3.5 ms in the control group (P = .01); III, -11.3 +/- -10.5 ms vs -2.6 +/- -6.5 ms (P = .002); aVF, -18.2 +/- -13.5 ms vs -3.8 +/- -5.3 ms (P < .0001). It is concluded that incident RBBB complicating revascularization procedures may cause significant alterations in spatial orientation of the initial excitation wavefronts. This may be a potential source of false-negative ECG diagnosis of inferior MI, particularly in clinical trials where serial ECG analysis is an important part in MI classification.

Electrocardiographic (ECG) manifestations of clinical and subclinical cardiovascular disease are used as an important component in the evaluation of clinical trials, and there is an increasing demand for well-defined criteria for clinically significant evolution of ECG abnormalities. The Novacode ECG classification system provides a comprehensive hierarchical set of criteria for prevalent ECG abnormalities and for clinically significant serial ECG changes, both adverse and favorable, as a response to pharmacologic, surgical, and other interventions. These criteria are used to grade Q wave and ischemic abnormalities in order to achieve stable classification of both prevalent and incident myocardial infarctions by minimizing false classifications due to clinically insignificant ECG variations. This approach differs from the traditional Minnesota Code classification system, in which incident events are determined by changes in classification categories, with the application of additional elaborate validation rules to exclude frequent false classifications. Novacode hierarchy is so structured that for each abnormality, a general class is first determined with the simplest possible classification criteria and more specific abnormality subgroups are then classified with more elaborate criteria. This approach will satisfy differing needs of clinical trials for detail in classification. Explicit definition of ECG variables and condition statements for the classification criteria facilitate implementation of the Novacode with computer ECG programs.

It is clinically important to estimate the size of a myocardial infarction (MI) to predict patient prognosis, to determine the ability of a therapy to limit its size, and to evaluate its effect on left ventricular function. Various electrocardiographic methods have been used for these purposes but their accuracies have not been compared with each other using an identical reference population of anatomically measured infarcts. The capability of 4 electrocardiographic scoring methods (the Selvester score, the Minnesota code, the Novacode, and the Cardiac Infarction Injury Score) to estimate MI size was compared using anatomic MI size in a group of 100 deceased patients. All patients had a standard 12-lead electrocardiogram of sufficient quality to perform manual waveform measurements and without confounding factors such as ventricular hypertrophy, fascicular block, or bundle branch block. The location and size of the left ventricular infarction was measured postmortem using the anatomic method of Ideker et al. All methods' size estimates correlated best with anatomic MI size in the anterior location (r = 0.65 to 0.89). The Selvester score was superior in estimating the sizes of inferior (r = 0.70) and posterolateral (r = 0.74) infarcts. For multiple infarcts all methods performed poorly (r = 0.18 to 0.44).

Myocardial ischemia identified by ambulatory electrocardiography (AECG), exercising treadmill testing, (ETT), or 12-lead electrocardiogram at rest is associated with an adverse prognosis, but the effect of improving these ischemic manifestations by treatment on outcome is unknown. The Asymptomatic Cardiac Ischemia Pilot (ACIP) study was a National Heart, Lung, and Blood Institute funded study to determine the feasibility of conducting a large-scale prognosis study and to assess the effect of 3 treatment strategies (angina-guided strategy, AECG ischemia-guided strategy, and revascularization strategy) in reducing the manifestations of ischemia as indicated by AECG and ETT. The study cohort for this database study consisted of 496 randomized patients who performed the AECG, ETT, and 12-lead electrocardiogram at rest at both the qualifying and week 12 visits. The effect of modifying ischemia by treatment on the incidence of cardiac events (death, myocardial infarction, coronary revascularization procedure, or hospitalization for an ischemic event) at 1 year was examined. In the 2 medical treatment groups (n = 328) there was an association between the number of ambulatory electrocardiographic ischemic episodes at the qualifying visit and combined cardiac events at 1 year (p = 0.003). In the AECG ischemia-guided patients there was a trend associating greater reduction in the number of ambulatory electrocardiographic ischemia episodes with a reduced incidence of combined cardiac events (r = -0.15, p = 0.06). In the revascularization strategy patients this association was absent. In the medical treatment patients the exercise duration on the baseline ETT was inversely associated with an adverse prognosis (p = 0.02). The medical treatment strategies only slightly improved the exercise time and the exercise duration remained of prognostic significance. In the revascularization group strategy patients this association was absent. Thus, myocardial ischemia detected by AECG and an abnormal ETT are each independently associated with an adverse cardiac outcome in patients subsequently treated medically.

Serial electrocardiographic (ECG) changes are a critical component of the diagnostic algorithm for classification of myocardial ischemic events in large-scale clinical trials. This study describes a computerized serial ECG classification program developed at the St. Louis University Core ECG Laboratory for use in the Bypass Angioplasty Revascularization Investigation (BARI) trial, in which patients with multivessel coronary artery disease were randomized to receive either coronary artery bypass grafting or percutaneous transluminal coronary angioplasty. The St. Louis University program detects and codes serial changes in Q, ST, and T wave items according to Minnesota code (MC) criteria using a modified NOVACODE hierarchical classification system. Measurements using a seven-power calibrated coding loupe are used to generate the MC from a customized software program. Significant minor or major changes are detected by the serial comparison program and referred to a physician coder for verification. Serial comparison coding rules are used to adjust for weaknesses in the standard MC classification system resulting from instability at decision boundaries. Of 4,244 BARI randomized and registry study participants with follow-up ECGs received at the Core ECG Laboratory as of March 1995, a grade 2 MC Q wave progression was noted in 568 participants (13.4%) using MC criteria alone, as compared with 367 (8.6%) after the St. Louis University coding rules were applied. The incidence of grade 1 MC Q wave progressions was 16.4% (697/4,244) versus 6.1% (259/4,244) when the St. Louis University program was applied. Intraobserver variability for grade 2 Q wave progression codes determined from a sample of 812 serial.

Among patients with acute ischemic syndromes, patients with non-Q-wave acute myocardial infarction (AMI) are known to be at higher risk for death, reinfarction, and other morbidity than those with unstable angina. The aim of this study was to develop a clinically useful prediction rule to assist in distinguishing, at the time of presentation, patients with non-Q-wave AMI from those with unstable angina. The TIMI IIIB trial enrolled 1,473 patients presenting with ischemic pain at rest within 24 hours who had either electrocardiographic changes or documented coronary artery disease. Non-Q-wave AMI on presentation was documented by elevation of creatine kinase-MB in 33% of patients. Fifty clinical and electrocardiographic variables were compared between the patients with non-Q-wave AMI and unstable angina. After performing logistic regression, 4 baseline characteristics independently predicted non-Q-wave myocardial AMI: the absence of prior coronary angioplasty (odds ratio [OR] = 3.3, p < 0.001), duration of pain > or = 60 minutes (OR = 2.9, p < 0.001), ST-segment deviation on the qualifying electrocardiogram (OR = 2.0, p < 0.001), and recent-onset angina (OR = 1.7, p = 0.002). Using these 4 characteristics, a prediction rule for non-Q-wave AMI was developed. For the entire cohort of patients in TIMI III, the percentages of patients with non-Q-wave AMI when 0, 1, 2, 3, and 4 risk factors were present were 7.0%, 19.6%, 24.4%, 49.9%, and 70.6%, respectively (p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

The ECG is the most widely used noninvasive diagnostic and prognostic test administered to patients with suspected or proven coronary artery disease. When considering appropriate use of the electrocardiogram, physicians need to examine the clinical question being asked, the additional information that can be derived, whether or not a diagnosis can be established, and application of the information to make appropriate management decisions.

The authors report on a semiautomated program that incorporates both visual identification of fiducial points and digital determination of the ST-segment at 60 ms and 80 ms from the J point, ST slope, changes in R wave, and baseline drift. The off-line program can enhance the accuracy of detecting electrocardiographic (ECG) changes, as well as reproducibility of the exercise and postexercise ECG, as a marker of myocardial ischemia. The analysis program is written in Microsoft QuickBASIC 2.0 for an IBM personal computer interfaced to a Summagraphics mm1201 microgrid II digitizer. The program consists of the following components: (1) alphanumeric data entry, (2) ECG wave form digitization, (2) calculation of test results, (4) physician overread, and (5) editor function for remeasurements. This computerized exercise ECG digitization-interpretation program is accurate and reproducible for the quantitative assessment of ST changes and requires minimal time allotment for physician overread. The program is suitable for analysis and interpretation of large volumes of exercise tests in multicenter clinical trials and is currently utilized in the TIMI II, TIMI III, and BARI studies sponsored by the National Institutes of Health.

Traditional serial electrocardiogram (ECG) change classification schemes used in clinical trials such as the Minnesota Code rely on independent classification of the baseline and each follow-up or acute event ECG, whereby graded changes in the hierarchic severity level of the code signify new events such as myocardial infarction (MI). This approach suffers from classification errors caused by repeated instability at decision boundaries at each step when the baseline and each acute event ECG is classified, and various "verification rules" must be used at the end of the coding process to prevent trivial serial changes from causing large transitions in coded events. The NOVACODE algorithms for visual and computer coding of serial ECGs were designed to alleviate some of these instability problems by quantifying changes in critical waveform patterns on a continuous scale. This is achieved by determining, for each ECG coded, a Q-QS Score, ST Depression Score, ST Elevation Score and T-Wave Score, each ranging from 0 to 50. In the next step, a score is derived for ST-T evolution and this ST-T Evolution Score together with changes in Q-QS Score define criteria for a hierarchic mutually exclusive serial ECG change classification scheme that includes coding categories for Q-wave and non-Q wave MIs, equivocal Q wave evolution, evolving ischemic ST-T abnormalities, and various combinations of nonevolving Q-QS wave, and ST-T abnormalities.(ABSTRACT TRUNCATED AT 250 WORDS)

Exercise electrocardiograms of 20 patients were analyzed using a customized software exercise electrocardiographic program and compared to measurements made by two cardiologists performing independent interpretations. The computerized program requires identification of the PQ junction, J point, and tracing of the ST-segment in three consecutive beats. The proportion of variance for J point, and ST 80 measurements was 0.93 and 0.90, respectively, when the same electrocardiogram was processed twice and analyzed by two separate cardiologists. The same 20 exercise electrocardiograms were analyzed by two other experienced cardiologists without computerized measurements. The proportion of variance was less at 0.73 and 0.76 for the J point and ST 80 measurements, respectively. The average amount of time required for the cardiologist to over read the computerized measurements was 2.7 +/- 1.5 minutes per ECG as compared to 20.7 +/- 11 minutes for the cardiologists who did not have computer-assisted measurements (p less than 0.0001). Thus, off-line computerized exercise electrocardiographic interpretation is highly reproducible, accurate, time-sparing for cardiologist over read function, and suitable for use in large-scale clinical trials.

The prognostic value of early exercise testing after successful coronary angioplasty was determined in 196 and 225 consecutive patients with single-vessel and multivessel coronary disease, respectively, who underwent a symptom-limited exercise test within 30 days of the procedure. The incidence of exercise-induced ST segment depression greater than or equal to 1 mm was significantly greater in patients with multivessel versus single-vessel disease (27% versus 14%; p less than 0.005) and in patients with multivessel coronary disease who had incomplete versus complete revascularization (36% versus 10%; p less than 0.001). An abnormal exercise ECG result was associated with a significantly increased risk of cardiac events in patients with multivessel disease but not in patients with single-vessel disease. Exercise-induced angina occurred in a small and similar proportion of patients with single and multivessel coronary disease (8% versus 12%). The presence of exercise-induced angina was associated with a higher incidence of follow-up cardiac events in patients with multivessel disease and incomplete revascularization (52% versus 33%; p less than 0.05). Exercise duration was significantly less in patients with multivessel disease who had a subsequent cardiac event compared with that in patients who did not have such an event (458 +/- 168 versus 519 +/- 156 seconds; p = 0.01). Thus an abnormal exercise ECG finding within 1 month of successful coronary angioplasty is predictive of subsequent cardiac events in patients who have multivessel disease. The prognostic content of the test might be further improved if the test were performed several months after the procedure when the risk of restenosis is greatest.

The duration of electrical systole (QT interval) was measured in 72 subjects (48 women and 24 men) who had normal coronary arteries and left ventricular function at cardiac catheterization (group 1). The same measurements were obtained in 100 patients with a normal ECG (from 40 women and 60 men referred to our institution and found normal on a noninvasive clinical basis) and compared to a double independent manual calculation (group 2). The computer assisted program was found reliable in QT interval measurements. In both study groups women showed longer QTc. No difference in QTc duration was seen in subjects taking beta-blockers prior to angiography. As compared to group 1, subjects of group 2 showed similar average QTc values. However, 9 out of 100 subjects of group 2 had abnormal QTc as compared with none of group 1 (p less than 0.05). QTc calculations may improve the usefulness of computer assisted programs in ECG interpretation. Present data can be used as reference values for normality. They stress in addition the necessity of introducing the heart rate correction for the interpretation of QT interval. This can help in stimulating prospective clinical studies to assess the value of QTc as an index of risk for cardiac dysrhythmias.

We studied 83 men, who had a chest pain syndrome, no prior history of myocardial infarction, and exercise-induced horizontal or downsloping ST segment depression greater than or equal to 0.2 mV. The 38 patients unable to complete Bruce stage II had a significant increased risk of coronary (0.97 vs 0.71) and multivessel (0.88 vs 0.61) disease (p less than 0.01) compared to the pretest risk; data obtained from exercise-reperfusion thallium scintigraphy and cardiac fluoroscopy did not alter the risk of coronary or multivessel disease. The 45 patients who had ST depression greater than or equal to 0.2 mV and a peak work capacity greater than or equal to Bruce stage III did not have a significant increased risk of coronary (0.76) or multivessel disease (0.44). When both exercise-reperfusion thallium scintigraphy and cardiac fluoroscopy were abnormal in this latter patient subgroup, the post-test risk of multivessel disease was increased from 0.44 to 0.82 (p less than 0.03); when both tests were normal, none of the patients had multivessel disease (p less than 0.03) and only 0.18 had coronary artery disease. Thus, cardiac fluoroscopy and exercise thallium scintigraphy increase the diagnostic content of the strongly positive exercise ECG, particularly in men who have a peak work capacity greater than or equal to Bruce stage III.

One hundred consecutive men with a normal ECG at rest had a maximal treadmill test using 14 leads during and post-exercise. Coronary arteriography performed the following day revealed coronary stenoses greater than or equal to 70% in 66 patients. Test results obtained from a V5 lead were compared to different lead combinations and were correlated with arteriographic findings. A positive exercise test occurred in 37 men using an isolated V5 lead compared to 50 men (P less than 0.05) using 11 leads, 52 men (P less than 0.05) using a combined CM5, CC5, Cl (inferior) lead system and 58 (P less than 0.001) men using all 14 leads. The predictive value of a positive test varied between 89-95% and was not changed significantly by the addition of multiple leads. The 14 lead ECG was positive in 43/45 (96%) patients with multivessel disease. Parameters which helped to predict multivessel disease using 14 leads were 1) the time that ischemia first appeared 2) the pressure-rate product at the time ischemia first appeared, and 3) the maximum workload that could be attained. In general, the magnitude of ST-segment depression and the time required for a positive ECG to return to normal postexercise were not useful predictors of multivessel disease. We conclude that the use of multiple leads improves the sensitivity and efficiency of the maximal treadmill exercise test. The usefulness of exercise test results can be further improved if multiple leads are combined with physiologic data collected during exercise.

One thousand consecutive ECG's from an ambulatory population of patients with suspected or proven cardiac disease were evaluated using two versions of the Telemed computerized ECG system. Only minor differences were found between the two programs. In version 6 vs. version 5, 87% vs. 90% of 287 normal ECG's were correctly classified and 93% vs. 96% of abnormal ECG's were correctly classified; the percent of acceptable diagnostic agreement was 86.2% and 87.4% respectively (NS). The sensitivity for arrhythmia detection, transmural inferior infarction and ST-T wave abnormalities was slightly greater in version 6. The increased sensitivity was not accompanied by decreased specificity. The sensitivity for left ventricular hypertrophy decreased from 95.2% to 91.4% in version 6 with a slight increase in specificity (95.2% to 97.0%). In conclusion, criteria changes in the most recent version of the Telemed program have not resulted in a major change in diagnostic performance. Arrhythmia detection is slightly but not significantly improved.

To determine if the signal-averaged electrocardiographic detection of late potentials is an independent marker of sustained ventricular tachycardia (VT) in patients with documented chronic coronary artery disease (CAD), 57 patients underwent signal-averaged electrocardiography. Mean ejection fraction was 47 +/- 13% in the 14 patients with sustained VT and 56 +/- 19% in the 43 patients without VT (difference not significant). The sensitivity, specificity and accuracy of late potentials for detecting patients with VT were 64% (9 of 14), 79% (34 of 43), and 75% (43 of 57), respectively. Univariate analysis and stepwise logistic regression of angiographic and electrocardiographic variables identified late potentials as an independent marker of the patient with sustained VT. The odds ratio for late potentials to detect patients with prior sustained VT was 2.6. Six-month follow-up revealed a cardiac mortality rate of 11% and an arrhythmia event rate of 22% in patients with late potentials vs a cardiac mortality rate of 3% and an arrhythmia event rate of 13% in patients without late potentials. Thus, signal-averaged electrocardiographic detection of late potentials is useful in identifying patients with prior sustained VT independent of left ventricular function.

There are few data on the long-term effects of new Q waves on survival and morbidity after coronary bypass graft surgery (CABG). We followed 1340 patients who underwent CABG in 1978 at 10 hospitals participating in the Coronary Artery Surgery Study (CASS). The incidence of perioperative Q-wave infarction was 4.76% (range 0.0-10.3% by hospital). The rate of infarction was higher in patients who had an increased left ventricular end-diastolic pressure or cardiomegaly on the preoperative chest radiograph. Patients who received more grafts or who had longer cardiopulmonary bypass time were also at higher risk of infarction. In a stepwise discriminant analysis of 44 clinical, angiographic and surgical variables, cardiopulmonary bypass time, topical cardiac hypothermia and cardiomegaly entered the stepwise selection of variables. Long-term survival was adversely affected by the appearance of new postoperative Q waves. The hospital mortality was 9.7% in the 62 patients who had new postoperative Q waves and 1.0% in the 1278 patients who did not (p less than 0.001); the 3-year cumulative survival rates were 85% and 95%, respectively (p less than 0.001). In patients who survived to hospital discharge, the presence of new postoperative Q waves did not adversely affect 3-year survival (94% and 96%, respectively). The survival rates were worse in patients who had a history of infarction or who had impaired left ventricular function preoperatively. The number of readmissions to hospital after CABG among the patients who had a transmural perioperative infarction was similar to to that among patients who did not. We conclude that the appearance of new Q waves after CABG adversely affects survival. The major impact on mortality occurs before hospital discharge. Patients who are destined to have a perioperative infarct cannot be predicted from commonly measured preoperative and angiographic variables.

A comparison of current exercise electrocardiographic lead systems reveals differences in the sensitivity and specificity of S-T segment shifts diagnostic of obstructive coronary artery disease. The differences are explained in part by differences in population samples, lead systems and criteria for positivity. Multiple electrocardiographic lead recording in symptomatic patients during and after exercise improves sensitivity in detecting S-T segment shifts with only a small decrease in specificity. A review of population screening studies in asymptomatic subjects shows a wide selection of different exercise electrocardiographic lead systems and criteria for a positive test. Few screening studies have compared the prevalence of different S-T segment configurations in individual leads of a simultaneously recorded multiple lead system during or after exercise. Data from animal studies of myocardial ischemia suggest why 100 percent sensitivity in detecting obstructive coronary disease is unlikely to be obtained with surface electrocardiographic recordings. Additional research is required to identify the optimal set of diagnostic exercise electrocardiographic leads and criteria for positivity so that maximal predictive accuracy can be obtained for different patient subsets.

To determine to what extent the diagnostic accuracy of stress testing is influenced by the prevalence of coronary-artery disease, we correlated the description of chest pain, the result of stress testing and the results of coronary arteriography in 1465 men and 580 women from a multicentered clinical trial. The pre-test risk (prevalence of coronary-artery disease) varied from 7 to 87 per cent, depending on sex and classification of chest pain. A positive stress test increased the pre-test risk by only 6 to 20 per cent, whereas a negative test decreased the risk by only 2 to 28 per cent. Aothough the percentage of false-positive results differed between men and women (12 +/- 1 per cent versus 53 +/- 3 per cent P less than 0.001), this difference was not seen in a subgroup matched for prevalence of coronary-artery disease. We conclude that the ability of stress testing to predict coronary-artery disease is limited in a heterogeneous population in which the prevalence of disease can be estimated through classification of chest pain and the sex of the patient.

A series of 1000 12 lead ECGs recorded in 1000 consecutive ambulatory patients were analysed by the Telemed (V Version) programme and its interpretation and the precision of the French translation were compared with the interpretation of two physicians using standard criteria. The computer identified 90% of the 285 ECGs coded as "normal" by the physicians, 69% of the 57 ECGs coded as "borderline" and 96% of the 658 ECGs coded as "abnormal". The computer interpretation was correct in 74% of cases and acceptable in 87,4% of cases. The computer classified 80% of the 240 arrhythmias correctly. Atrial fibrillation was detected in 91% of cases, and ventricular and supraventricular extrasystoles in 88% of cases. The recognition of other arrhythmias was not as good but the small number of cases did not allow statistical evaluation. The 148 cases of axis deviation and 98% of ventricular conduction defects were identified. The programme detected 84% of transmural infarcts, the sensitivity being greater for anterior or lateral than inferior infarctions. The majority of undiagnosed infarcts were "possibles" according to the criteria of the Minnesota Code. Of 536 ECGs with ST-T segment abnormalities, 81% were classified correctly; ST depression of less than 0.5 mm comprised the majority of false negatives. The sensitivity of the programme to left ventricular hypertrophy was excellent (95%) with a specificity of only 92,5% as the programme uses the Romhilt-Estes criteria which are more liberal than those of the Minnesota Code. The comparison of the sensitivity and specificity for the commonest ECG changes showed excellent all round diagnostic performance of the Telemed programme. In conclusion, despite the large number of abnormal ECGs, the level of computer-physician concordance was high. The French translation of the V Version of the Telemed programme is therefore suitable for clinical use Nevertheless, the computer interpretation should still be checked by a physician.

The functional and prognostic significance of exercise-induced ST elevation (by computer averaging) in ambulatory patients with coronary heart disease was recently reported for 181 patients in the Seattle Heart Watch (SHW). To further evaluate this, 3050 approximately similar patients enrolled in CASS were analyzed with respect to initial findings, survival, and incidence of secondary coronary events over the next 6 years. The ST elevation responses in CASS patients were classified by visual interpretation of 1 mm or more, whereas the SHW patients were identified by voltage greater than 0 mV. Accordingly, prevalence of exercise-induced ST elevation was lower in CASS patients, but they had greater frequencies of prior myocardial infarction and left ventricular enlargement and dysfunction. The poor survival was similar in the subgroup with ST elevation during exercise and recovery in CASS and SHW. Although not an independent predictor when invasive variables are known, ST elevation emerges as a useful predictor when exercise testing is performed before diagnostic invasive studies.

Physiological adaptations of the heart to prolonged, intense physical training produce electrocardiographic changes considered abnormal in untrained persons. Increased vagal tone, anatomical changes in the heart, and other less understood mechanisms are thought to cause a spectrum of surface ECG changes characteristic of trained athletes. Arrhythmias frequently seen include sinus bradycardia, sinus pauses, and supraventricular ectopic beats. Conduction abnormalities such as prolonged P-R interval, first degree AV heart block, Wenckebach type I AV heart block, non-sinus escape rhythms, and intraventricular conduction delays of right bundle branch type are also found. Other commonly seen abnormalities include right axis deviation, increased right and left ventricular voltage, ST segment elevation, diphasic and inverted T waves, and prominent U waves. Changes in ECG parameters with exercise include a shortening of the P-R interval with a concomitant increase in the P wave/P-R interval ratio, improved AV conduction with cessation of Wenckebach phenomenon, and normalisation of ST segment and other T wave changes. Thallium scintigraphy and radionuclide angiography have been very useful in ruling out ischaemic heart disease in athletes with rest- and exercise-induced repolarisation abnormalities. Racial differences in QRS voltage and repolarisation changes have been documented. In summary, it is important to consider the type of physical activity, intensity of training, race of athlete, body habitus, and the time the ECG was obtained in relation to training in order to better understand the "normal' spectrum of ECG changes in athletes.