Exaggerated atrial repolarization waves as a predictor of false positive exercise tests in an unselected population

The authors previously postulated that a markedly downsloping PR-segment might be a marker for exaggerated atrial repolarization waves and demonstrated PR-segment appearance to be an independent predictor of a false positive exercise test. This study was conducted to determine the sensitivity, specificity, and predictive value of markedly downsloping PR-segments for predicting false positive exercise tests. The study group consisted of 82 consecutive patients with a positive exercise test (≥ 1.0 mm horizontal ST depression) and a normal resting electrocardiogram. Tests were predicted to be false positive based on previously defined criteria: (1) markedly downsloping PR-segments in two or more of leads II, III, and aVF and (2) exercise duration 4 minutes or longer. Patients were then classified according to available clinical information (coronary angiography and radionuclide stress testing) into true positive (due to myocardial ischemia, n = 62) and false positive (n = 20) groups. The sensitivity, specificity, and predictive value of the PR-segment/exercise duration criterion for predicting a false positive test were 70, 74, and 47%, respectively. Patients with false positive tests also had higher heart rates (158 ± 16 vs 136 ± 20 beats/min, P < .001) and less frequent chest pain (15 vs 46%, P = .017) during the exercise test. Patients with false positive exercise tests can be recognized by the achievement of a high peak exercise heart rate, the absence of exercise-induced chest pain, and the appearance of markedly downsloping PR-segments in the inferior leads.     

P-R段明显下斜对运动试验假阳性的预测作用

目的探讨下壁导联P-R段明显下斜与运动试验假阳性的关系。方法比较76例运动试验阳性经冠状动脉造影确诊为真阳性组57例、假阳性组19例的运动试验参数。结果假阳性组有较长的运动总时间(389±112s∶287±95s,P<0.01),达到较大的代谢当量(7.9±1.9mets∶6.6±1.5mets,P<0.01),ST段压低≥1mm时间延长(284±140s:192±97s,P<0.01),运动中较少诱发胸痛及至少2个下壁导联P-R段明显下斜的比例较高(74%∶20%,P<0.01),若以运动总时间≥300s、至少2个下壁导联P-R段明显下斜判断运动试验假阳性,其敏感性为63%,特异性为91%,预测价值为88%。结论运动总时间≥300s、至少2个下壁导联P-R段明显下斜对运动试验假阳性的判断有较高的特异性。     

Assessment of electrocardiographic criteria for left atrial enlargement in childhood

Ninety children, aged 1 day to 18 years (median 7 months), with electrocardiographic or echocardiographic evidence of left atrial (LA) enlargement were selected to determine if electrocardiographic criteria accurately reflected increased LA dimension as determined by echocardiography. Four cardiac defects known to produce LA enlargement were chosen: ventricular septal defect (24 patients), patient ductus arteriosus (25 patients), cardiomyopathy (27 patients) and mitral regurgitation (14 patients). Different electrocardiographic criteria for LA enlargement were assessed. The data indicated that the overall sensitivity and predictive value of the ECG to detect LA enlargement were 40 and 85%, respectively. The ECG and echocardiogram failed to agree in 62% of the patients. The most predictive variable for LA enlargement was the presence of a notched P wave in the limb leads with a large negative terminal deflection in lead V1. The sensitivity of ECG was highest in patients with chronic LA overload status, in mitral regurgitation (77%), cardiomyopathy (50%) and ventricular septal defect (54%). The results show that in the pediatric population, electrocardiographic criteria are moderately predictive for LA enlargement but not as sensitive as generally believed.     

Two-dimensional echocardiographic assessment of electrocardiographic criteria for right atrial enlargement

Right atrial (RA) size was determined with two-dimensional echocardiography using the apical four-chamber view in 45 adult patients with various echocardiographic criteria for RA enlargement and in 25 normal controls. RA size varied from 11.4-24.0 cm2 (mean 16.1 cm2) in controls. RA enlargement (greater than or equal to 25 cm2) was found in only two of 11 patients with P pulmonale (predictive value [PV] = 18%) and one of five with prominent positive P-wave forces in lead V1 (PV = 20%). However, RA enlargement ws found in eight of eight patients with a qR pattern in lead V1 in the absence of clinical indications of coronary artery disease (PV = 100%). RA enlargement was also found in 13 of 28 patients with a total QRS amplitude in lead V1 of 6 mm or less and a threefold or greater ratio of total QRS amplitude in lead V2 relative to that in V1(V2/V1 greater than or equal to 3) (PV = 48%). A V2/V1 ratio of 4 or more detected 11 of 13 patients with RA enlargement, with six false-positive diagnoses (sensitivity = 85%, specificity = 60%, PV = 65%). The combination of total QRS amplitude in V1 of 4 mm or less, together with a V2/V1 ratio of 5 or more, detected six of 11 with RA enlargement, with one false-positive diagnosis (sensitivity = 46%, specificity = 93%, PV = 86%). We conclude that ECG criteria for RA enlargement that primarily use increased P-wave amplitude have a limited PV. The qR pattern in lead V1 appears to be extremely accurate in detecting RA enlargement. ECG criteria in leads V1 and V2 using decreased amplitude in leads V1 and a V2/V1 greater than or equal to 3 are of some value in detecting RA enlargement.     

Evaluation of abnormal exercise electrocardiogram in apparently healthy subjects: Labile repolarization (ST-T) abnormalities as a cause of false positive responses

Long-term follow-up studies were carried out in 121 apparently healthy men with an abnormal S-T segment response to exercise—49 Indiana State policemen and 72 subjects from a large occupational health center. The mean follow-up periods were 66 months and 43 months, respectively, for the two groups of subjects. A tendency toward labile S-T or T wave abnormalities were documented during standing rest or with hyperventilation in 61 of these 121 subjects and there was only one new coronary event in this subgroup. The labile ST-T wave changes and the abnormal S-T segment responses to exercise were not consistently reproducible in these subjects, and it was not unusual to see an abnormal S-T segment response at a time when the labile repolarization changes could not be demonstrated. Many of the subjects exhibited labile ST-T wave changes only after oral glucose loading. Significant coronary artery disease was documented in 34 (57 percent) of the remaining 60 subjects during the follow-up period.Coronary cineangiographic studies, obtained in 21 of the 35 subjects from the health center who had had no evidence of labile ST-T wave abnormalities, revealed coronary arterial stenoses of 75 percent or greater in 19. A statistical analysis was carried out in the 35 subjects without labile ST-T abnormalities to determine if there were exercise test variables that would differentiate the true positive from the false positive responses. A set of criteria were identified that yielded a specificity of 92 percent, a sensitivity of 82 percent and a predictive value of 95 percent. The entire group of 72 from the health center subjects had undergone an average of 3.8 exercise tests before their referral to the authors' laboratory. A review of these records revealed that a serial conversion from a normal to an abnormal S-T segment response was not more predictive of underlying coronary artery disease than an initially abnormal test result.     

Impact of ostium secundum atrial septal defect closure on the resolution of falsely positive electrocardiographic criteria for myocardial scarring

Background

Electrocardiographic (ECG) Selvester QRS score criteria with false indication of anteroseptal scarring consistent with myocardial infarction have been found in patients with ostium secundum atrial septal defect (OS-ASD). The objective of this study was to evaluate ECGs pre and post percutaneous transcatheter OS-ASD closure to test the hypothesis that the falsely positive criteria for anteroseptal scar decline 1 day post procedure.

Methods

Patients (n = 34, mean age 48 ± 17 years, 79% female) that underwent OS-ASD closure and had undergone pre procedure cardiac magnetic resonance imaging showing no left ventricular (LV) scarring were included in this study. ECGs pre and 1 day post procedure were assessed according to the QRS Selvester scoring system and compared.

Results

Mean Selvester score in anteroseptal regions pre procedure was 6.6 (0.0–6.8) % LV scar and decreased to 4.3 (0.0–6.0) % LV scar one day after the procedure (p = 0.01). Mean Selvester score in lateral regions pre procedure was 3.7 (0.0–3.0) %LV scar and decreased to 2.8 (0.0–0.0) % LV scar one day post procedure (p = 0.25).

Discussion

OS-ASD patients with falsely positive anteroseptal scar criteria by the Selvester QRS score pre procedure have a significant decrease in anteroseptal Selvester score 1 day post procedure. The falsely positive anteroseptal scar criteria did not completely resolve 1 day post procedure. Further studies are needed to investigate the relationship between ECG criteria for anteroseptal scar and right ventricular volume overload in late follow up.     

Relation of electrocardiographic criteria for left atrial enlargement to two-dimensional echocardiographic left atrial volume measurements

Left atrial (LA) enlargement by 2-dimensional (2-D) echocardiography predicts adverse cardiovascular outcomes. Electrocardiographic (ECG) criteria for LA enlargement are based on M-mode echocardiographic LA diameter, which is inferior to 2-D-derived LA volumes. This study compared established ECG criteria for LA enlargement with atrial volume obtained by 2-D echocardiography to determine if traditional ECG criteria accurately represent LA chamber enlargement, therefore offering a low-cost screening tool. A total of 261 randomly selected patients who underwent electrocardiography and 2-D echocardiography were enrolled. ECG parameters and electronically derived P-wave medians were analyzed with electronic calipers for maximal accuracy. LA volumes by 2-D echocardiography were measured with Simpson's method of discs, with enlargement defined as 32 ml/m(2). Sensitivity and specificity tables and receiver-operating characteristic curves were constructed for each criterion. Univariate and multivariate analyses were performed for predictors of 2-D echocardiographic LA enlargement. LA enlargement was present in 43% of patients. ECG P-wave duration was the most sensitive for the detection of LA enlargement (69%) but had low specificity (49%). Conversely, a biphasic P wave was the most specific (92%) but had low sensitivity (12%). The maximum area under the receiver-operating characteristic curve for any criterion was 0.64, too low to be of clinical utility. In conclusion, established ECG criteria for LA enlargement do not reliably reflect LA enlargement and lack sufficient predictive value to be useful clinically. These results suggest that P-wave abnormalities should be noted as nonspecific LA abnormalities, with the term "LA enlargement" no longer used.     

Heart rate adjustment of ST-segment depression for reduction of false positive electrocardiographic responses to exercise in asymptomatic men screened for coronary artery disease

The ability of heart rate (HR) correction of exercise-induced ST-segment depression (the delta ST/HR index) to reduce the number of false positive exercise electrocardiograms during initial screening for occult coronary artery disease (CAD) was examined in active, asymptomatic men from the Army Reserve. Among 606 consecutive men given treadmill tests, 62 asymptomatic subjects with normal results on resting electrocardiograms but abnormal outcomes on standard exercise electrocardiograms underwent rest and exercise radionuclide cineangiography, and the 10 subjects with abnormal radionuclide findings then underwent coronary angiography. A previously established delta ST/HR index less than 1.6 microV/beat/min correctly identified 34 of 52 subjects (65%) who, despite abnormal standard exercise electrocardiographic findings, had no rest or exercise radionuclide abnormalities. A delta ST/HR index greater than or equal to 1.6 microV/beta/min detected 7 of 7 subjects with abnormal radionuclide cineangiograms who had CAD at cardiac catheterization, but also identified 2 of 3 subjects with an abnormal radionuclide test who had no CAD. In contrast to the 7 of 62 subjects (11%) with abnormal standard exercise test criteria who had radionuclide and angiographic evidence of CAD, a delta ST/HR index partition of 1.6 microV/beat/min separated subjects into subgroups with 0% (0 of 35) vs 26% (7 of 27) prevalences of CAD by serial diagnostic evaluation (p less than 0.01). Thus, among asymptomatic subjects with abnormal electrocardiographic responses to exercise, simple HR correction of the magnitude of ST-segment depression reduced by 56% the number of subjects with standard exercise test criteria leading to referral for additional diagnostic evaluation, without loss of sensitivity for angiographically proven CAD and with accurate negative predictive value.(ABSTRACT TRUNCATED AT 250 WORDS)     

Study of repolarization heterogeneity and electrocardiographic morphology with a modeling approach

Background

Increase of heart repolarization heterogeneity has been linked to severe or even life-threatening arrhythmia like torsades de pointes and other forms of ventricular tachycardia. Although electrocardiography (ECG) still remains as the most convenient and cost-effective method of monitoring electrical activity of the heart, the link between ECG morphology and repolarization heterogeneity is not clear. Previous attempts of using QT interval dispersion from multiple leads to assess the heterogeneity changes were not successful either.

Method

The aim of this study is to use a cell-to-ECG model to study ECG morphology changes while varying transmural heterogeneity. The heterogeneity is simulated by increasing the difference of M cell Ikr block factors from either endocardial or epicardial cells. The model-simulated ECGs were processed and measured. The ECG parameters studied include QT interval dispersion of standard 12-lead ECG, QT peak dispersion, and T-peak to T-end interval (TpTe). An ECG vector magnitude signal based on 12-lead ECG was formed to estimate the global QT interval (vs lead-by-lead QT interval used for calculating QT dispersion) and also the global TpTe (TpTe_VM).

Results

The results based on the model simulation show that the TpTe_VM is highly correlated with transmural dispersion of repolarization (TDR), with a correlation coefficient of 0.97. The correlation coefficients of QT interval dispersion and QT peak dispersion with TDR are 0.44 and 0.80, respectively.

Conclusion

In conclusion, the cell-to-ECG model provides a unique way to study electrophysiology and to link physiologic factors to ECG morphology changes. The simulation results suggest that global TpTe can be a strong indicator of TDR.     

Evaluation of the electrocardiographic criteria for left ventricular hypertrophy with use of three-dimensional echocardiography

BACKGROUND: Left ventricular hypertrophy (LVH) is a common condition that carries an increased risk of cardiovascular events. Use of ECG in detection of LVH is limited because of the reported low sensitivity. Conventional echocardiographic techniques used as the standard for estimating left ventricular (LV) mass have limitations related to the position of the image plane and shape of the ventricle. Three-dimensional echocardiography is free of these limitations and therefore is more accurate. We hypothesized that accuracy of ECG criteria for LVH would improve when LV mass was assessed by three-dimensional echocardiography. RESULTS: For most of the criteria, sensitivity, specificity and accuracy improved when LV mass was assessed by three-dimensional echocardiography. Two-dimensional echocardiography significantly overestimated LV mass as compared with the three-dimensional method. CONCLUSIONS: Sensitivity, specificity, and accuracy of the ECG criteria improved when LV mass was estimated by three-dimensional echocardiography. This improvement may be attributed at least in part to superior accuracy of three-dimensional measurements.     

Current electrocardiographic criteria for diagnosis of Brugada pattern: a consensus report

Brugada syndrome is an inherited heart disease without structural abnormalities that is thought to arise as a result of accelerated inactivation of Na channels and predominance of transient outward K current (I(to)) to generate a voltage gradient in the right ventricular layers. This gradient triggers ventricular tachycardia/ventricular fibrillation possibly through a phase 2 reentrant mechanism. The Brugada electrocardiographic (ECG) pattern, which can be dynamic and is sometimes concealed, being only recorded in upper precordial leads, is the hallmark of Brugada syndrome. Because of limitations of previous consensus documents describing the Brugada ECG pattern, especially in relation to the differences between types 2 and 3, a new consensus report to establish a set of new ECG criteria with higher accuracy has been considered necessary. In the new ECG criteria, only 2 ECG patterns are considered: pattern 1 identical to classic type 1 of other consensus (coved pattern) and pattern 2 that joins patterns 2 and 3 of previous consensus (saddle-back pattern). This consensus document describes the most important characteristics of 2 patterns and also the key points of differential diagnosis with different conditions that lead to Brugada-like pattern in the right precordial leads, especially right bundle-branch block, athletes, pectus excavatum, and arrhythmogenic right ventricular dysplasia/cardiomyopathy. Also discussed is the concept of Brugada phenocopies that are ECG patterns characteristic of Brugada pattern that may appear and disappear in relation with multiple causes but are not related with Brugada syndrome.