Adverse Prognosis of ST Depression on the Resting Electrocardiogram in Stable Patients Following Acute Myocardial Infarction

Background: The aim of this study was to analyze the characteristics of stable patients with resting ST segment depression on the resting electrocardiogram (ECG) following an acute ischemic event (i.e., infarction or unstable angina) to better understand its association with subsequent cardiac death and nonfatal infarction. The recent Multicenter Study of Myocardial Ischemia (MSMI) demonstrated that the resting ST segment depression had an independent prognostic value. Methods: We studied clinical features, noninvasive test results and coronary arteriography findings in 99 patients with ST depression on the resting ECG and 837 patients without ST segment depression with respect to endpoints of cardiac death and hospitalization for acute myocardial infarction or unstable angina. Results: Our results showed that patients with resting ECG ST depression were significantly older with a higher incidence of hypertension, angina, claudication, and tobacco use. ST depression on the resting ECG correlated closely with ST segment depression on the 24-hour ambulatory ECG and the exercise ECG but not with redistribution on the thallium perfusion scan. Left ventricular diastolic pressure was higher and exercise duration less in patients with ST depression. Although not achieving statistical significance, patients with ST depression did show more extensive coronary disease and a lower ejection fraction. Conclusions: ECG ST depression was associated with cardiac death and nonfatal reinfarction over the follow-up period only in patients originally admitted with an acute infarction but not in patients hospitalized for unstable angina. The reason for this appears to be an association of ST depression with increased age, the presence of hypertension, the presence of more severe coronary disease, and more extensive myocardial damage.     

Computerized ST Depression Analysis Improves Prediction of All‐Cause and Cardiovascular Mortality: The Strong Heart Study

Background: Nonspecific ST depression assessed by standard visual Minnesota coding (MC) has been demonstrated to predict risk. Although computer analysis has been applied to digital ECGs for MC, the prognostic value of computerized MC and computerized ST depression analyses have not been examined in relation to standard visual MC. Methods: The predictive value of nonspecific ST depression as determined by visual and computerized MC codes 4.2 or 4.3 was compared with computer‐measured ST depression ≧ 50 μV in 2,127 American Indian participants in the first Strong Heart Study examination. Computerized MC and ST depression were determined using separate computerized‐ECG analysis programs and visual MC was performed by an experienced ECG core laboratory. Results: The prevalence of MC 4.2 or 4.3 by computer was higher than by visual analysis (6.4 vs 4.4%, P < 0.001). After mean follow‐up of 3.7 ± 0.9 years, there were 73 cardiovascular deaths and 227 deaths from all causes. In univariate Cox analyses, visual MC (relative risk [RR] 4.8,95% confidence interval [CIJ 2.6–9.1), computerized MC (RR 6.0, 95% Cl 3.5–10.3), and computer‐measured ST depression (RR 7.6, 95% CI 4.5–12.9) were all significant predictors of cardiovascular death. In separate multivariate Cox regression analyses that included age, sex, diabetes, HDL and LDL cholesterol, body mass index, systolic and diastolic blood pressure, microalbuminuria, smoking, and the presence of coronary heart disease, computerized MC (RR 3.0, 95% Cl 1.6–5.6) and computer‐measured ST depression (RR 3.1, 95% Cl 1.7–5.7), but not visual MC, remained significant predictors of cardiovascular mortality. When both computerized MC and computer‐measured ST depression were entered into the multivariate Cox regression, each variable provided independent risk stratification (RR 2.1, 95% Cl 1.0–4.4, and RR 2.1, 95% CI 1.0–4.4, respectively). Similarly, computerized MC and computer‐measured ST depression, but not visual MC, were independent predictors of all‐cause mortality after controlling for standard risk factors. Conclusions: Computer analysis of the ECG, using computerized MC and computer‐measured ST depression, provides independent and additive risk stratification for cardiovascular and all‐cause mortality, and improves risk stratification compared with visual MC. These findings support the use of routine computer analysis of ST depression on the rest ECG for assessment of risk and suggest that computerized MC can replace visual MC for this purpose. A.N.E. 2001;6(2):107–116     

f‐Wave Suppression Method for Improvement of Locating T‐Wave Ends in Electrocardiograms during Atrial Fibrillation

This article is to propose an algorithm for improving T‐wave ends location during atrial fibrillation (AF). The traditional algorithms do not take the irregular baseline fibrillation of AF into consideration, so their location accuracy is relatively low. Based on simple assumptions that AF is a random signal while T waves and QRS complexes are deterministic signals, we suggest a novel method to suppress f wave for improving location of T‐wave ends during AF. We firstly define a new cardiac cycle and then match R peaks and T peaks in the three adjacent cardiac cycles. Finally, we suppress the interference of the f wave by averaging. When evaluating with the PhysioNet QT database and simulated AF signals in terms of the mean and the standard deviation of the T‐wave ends location errors, the proposed algorithm improves the performance of existing popular methods. Besides, the clinical significance of the proposed method is illustrated.     

T‐Wave Morphology in Short QT Syndrome

Background: Short QT syndrome (SQTS) is an inherited disorder characterized by a short QT interval and vulnerability to ventricular tachyarrhythmias. The diagnostic criteria for this syndrome are not well defined, since there is uncertainty about the lowest normal limits for the corrected QT (QTc) interval. Objective: The aim of this study was to determine whether T‐wave morphology parameters are abnormal in short QT subjects and whether those parameters can help in the diagnosis of SQTS. Methods and Results: We describe three families (10 patients) with short QT intervals (QTc 310 ± 32 ms). Seven subjects had suffered serious arrhythmic events and three were asymptomatic. T‐wave morphology was assessed using the principal component analysis (PCA). QTc was significantly shorter and T‐wave amplitude in lead V₂ higher in the short QT subjects compared to healthy controls (n = 149), (P < 0.001 for both). The total cosine of the angle between the main vectors of the QRS and T‐wave loops (TCRT) was markedly abnormal among the symptomatic patients with short QT syndrome (n = 7) (TCRT –0.14 ± 0.55 vs 0.36 ± 0.51, P = 0.019). None of the three asymptomatic patients with short QT but without a history of arrhythmic events had an abnormally low TCRT. Conclusion: Our observations suggest that patients with a short QT interval and a history of arrhythmic events have abnormal T‐wave loop parameters. These electrocardiogram (ECG) features may help in the diagnosis of SQTS in addition to the measurement of the duration of QT interval from the 12‐lead ECG.     

Microvolt T‐Wave Alternans as Predictor of Electrophysiological Testing Results in Professional Competitive Athletes

Background: Several studies have confirmed the equivalence of the microvolt T‐wave alternans (mTWA) and the electrophysiology (EPS) tests in cardiac disease. No data are available in populations of competitive athletes with arrhythmias that might jeopardize the pursuit of their professional career. Methods: We prospectively studied 100 trained competitive athletes, including elite types (72/100), (mean age ± standard deviation: 26.1 ± 4.5 years). Forty‐eight of them were wholly normal (Group A, mean age: 24.5 ± 8.5 years) and 52 of them had severe arrhythmias (Group B, mean age: 28.2 ± 11.5 years) and were symptomatic in 85% of cases for prolonged palpitations and syncope, but lacked any overt structural heart disease at standardized cardiological screening. All athletes were evaluated with the microvolt T‐wave alternans exercise–stress test, using the Heart Wave System with Microvolt Sensors. Group B underwent EPS to evaluate inducibility to sustained ventricular tachycardia (VT) during programmed electrical stimulation. Results: In Group A, the mTWA outcome was determinate in 45 subjects (94%) and indeterminate in 3 (6%). No symptomatic event was reported in a follow‐up of 36.1 months. In Group B, the mTWA test was positive in 7 symptomatic subjects (15%), indeterminate in 3 (7%), and negative for the remaining 42 subjects (76%). Forty‐one of 42 negative mTWA subjects were also negative in the EPS test, without any syncope or sustained VT during 25.3 months of follow‐up. In the positive mTWA test subjects, 5 (72%) were positive for inducibility of rapid sustained monomorphic VT in EPS, 1 was positive for severe sustained atrial tachyarrhythmias, and 1 refused EPS. We were able to pronounce a correct diagnosis of lymphocytic myocarditis for only 1 mTWA and EPS‐positive subject. For the other 4 positive patients with arrhythmogenic micropathology, severe arrhythmic events were revealed in the follow‐up and aggressive hybrid treatment was necessary. Conclusion: Microvolt‐TWA study seems to be a useful, noninvasive, and feasible tool for evaluating arrhythmic risk in the athletic population. The mTWA test showed a high negative predictive value, using both EPS and the follow‐up observation for severe arrhythmic cardiac events as an endpoint. The positive predictive value was present in a limited number of cases that were, however, subjects with a high risk of sudden arrhythmic death.     

Electrocardiographic T‐ and U‐Wave Discordance

Background: Abundant information has been reported regarding the U wave, which almost entirely has been focused on U waves in isolation. There has been little investigation of discordant T and U waves. Methods: Of 18,750 consecutively recorded electrocardiograms, 143 patients were categorized resulting in three groups. Group A: 53 patients with negative T waves and positive U waves (Type I Discordance); Group B: 26 patients with positive T waves and negative U waves (Type II Discordance); and Group C: 63 patients with negative T and negative U waves. Each patient's chart was reviewed for relevant clinical, laboratory, and medical history. Results: Coronary disease was slightly more common in Group A (64%) than in Group B (46%) (P = 0.174; ns). Coronary disease in Group C was extremely common (88%; P <0.001). Hypertension in the two discordant groups was similar: Group A (60%) versus Group B (58%) (P = ns), Group C was significantly higher (88%) (P <0.001). Left ventricular hypertrophy was 49% in Group A and 58% in Group B (P = ns), but Group C was significantly higher at 70% (P = 0.038). Conclusions: This appears to be the first investigation of the associations of discordant T and U waves. We found that the significance of any U wave is not independent of their respective T wave. In addition, we propose that the U wave not be analyzed in isolation, but rather with respect to its T wave.     

Brachial‐Ankle Pulse Wave Velocity and the Cardio‐Ankle Vascular Index as a Predictor of Cardiovascular Outcomes in Patients on Regular Hemodialysis

Brachial‐ankle pulse wave velocity (baPWV) and the cardio‐ankle vascular index (CAVI) are both used to evaluate arterial stiffness. The aim of the present study is to determine whether baPWV or CAVI is superior as a marker of arterial stiffness in hemodialysis (HD) patients. Of 194 patients, 59 patients had been excluded from the study due to advanced age over 76 years old (n = 29), or abnormal ankle‐brachial pressure index (ABI) (<0.90 or ≥1.30) (n = 30). We then followed the 135 patients (age: 60 ± 11 years, time on HD: 110 ± 93 months) for the 63 ± 4 (55–70) months. Thirty‐two (23.7%) patients had expired, 22 of them of cardiovascular (CV) causes. There were 37 fatal and non‐fatal CV events. Kaplan–Meier analysis revealed that the patients with the highest tertile of baPWV (≥16.6 m/s) had a significantly lower survival rate (P < 0.01) when compared with the second (13.4 ≤ baPWV < 16.6 m/s) and the lowest tertiles (<13.4 m/s). Cox hazards analysis after adjustment for comorbid risk factors revealed that the top tertile of baPWV was a determinant of CV death (hazards ratio [HR]: 16.9 [1.1–251.8], P < 0.05) In contrast, CAVI did not associate with CV mortality or events. These findings suggest that baPWV is superior to CAVI as a predictor of CV outcomes in patients on regular HD.     

Giant J Wave on 12‐Lead Electrocardiogram in Hypothermia

Findings on standard 12‐lead electrocardiogram in patients with hypothermia include sinus bradycardia, prolonged QT and PR interval, wide QRS complex, supraventricular and ventricular arrhythmia, and the most striking electrocardiographic abnormality, the J wave. Although characteristic of hypothermia, J wave also occurs in other conditions. The electro‐physiologic basis of J wave in hypothermia has been recently elucidated. We present a case of giant J wave due to accidental hypothermia and in addition discuss the features, mechanism, and significance of J wave in hypothermia. A.N.E. 2003; 8(3):262‐265     

Prognostic value of T‐wave morphology parameters in coronary artery disease in current treatment era

Background

The prognostic value of T‐wave morphology parameters in coronary artery disease in the current treatment era is not well established.

Methods

The Innovation to reduce Cardiovascular Complications of Diabetes at the Intersection (ARTEMIS) study included 1,946 patients with angiographically verified coronary artery disease (CAD). The study patients underwent thorough examinations including 12‐lead digital electrocardiogram (ECG) at baseline.

Results

During a follow‐up period of 73 ± 22 months, a total of 201 (10.3%) patients died. Of the study patients, 95 (4.9%) experienced cardiac death (CD) consisting of 44 (2.3%) sudden cardiac deaths (SCD) and 51 (2.6%) nonsudden cardiac deaths (NSCD), and 106 (5.4%) patients experienced noncardiac death (NCD). T‐wave morphology dispersion (TMD), T‐wave area dispersion (TWAD), and total cosine R‐to‐T (TCRT) had a significant association with CD even after adjustment with relevant clinical risk markers in the Cox regression analysis (multivariate HRs: 1.015, 95% CI 1.007–1.023, p = .0003; 0.474, 95% CI 0.305–0.737, p = .0009; 0.598, 95% CI 0.412–0.866, p = .006, respectively). When including these parameters to the clinical risk model for CD, the C‐index increased from 0.810 to 0.823 improving the discrimination significantly (integrated discrimination index [IDI] = 0.0118, 95% CI 0.0028–0.0208, p = .01). These parameters were more closely associated with NSCD (multivariate p‐values from .016 to .001) than with SCD (univariate/multivariate p‐values for TMD .015/.197 and for TCRT .012/.43).

Conclusion

T‐wave morphology parameters describing repolarization heterogeneity improve the predictive power of the clinical risk model for CD in patients with CAD in the current treatment era.

     

Are Reciprocal Changes a Consequence of “Ischemia at a Distance” or Merely a Benign Electrical Phenomenon? A Pulsed‐Wave Tissue Doppler Echocardiographic Study

Objectives: The aim of the present study was to investigate whether ST segment depression in precordial leads at the time of acute inferior myocardial infarction represents a reciprocal change rather than concurrent anterior wall ischemia on the surface electrocardiography. Background: The mechanism of reciprocal ST segment depression during acute myocardial infarction is controversial. “Ischemia at a distance” or a benign electrical phenomenon has been implicated in numerous reports. Pulsed‐wave tissue Doppler (PWTD) echocardiography can be used to examine the regional diastolic motion of the left ventricular myocardial wall and may allow the detection of ischemic segments. Methods: We evaluated regional myocardial ischemia using PWTD echocardiography in 48 patients with a first inferior wall myocardial infarction. The left ventricle was divided into 16 segments. PWTD echocardiographic velocities were obtained from each left ventricular segments. Results: Reciprocal ST segment depression was present in 35 patients (Group 1) but not in the remaining 13 patients (Group 2). There were no significant differences between groups 1 and 2 with respect to systolic (S) (7.4 ± 1.1 vs 6.8 ± 0.9 cm/s; P > 0.05), early (E) (10.5 ± 2 vs 9.4 ± 1.2 cm/s; P > 0.05), and late (A) (9.5 ± 3.2 vs 8.5 ± 2.3 cm/s; P > 0.05) diastolic waves peak velocities, E/A ratio 1.1 ± 0.2 vs 1.1 ± 0.1; P > 0.05), Ewave deceleration time (DT) (92 ± 17 vs 101 ± 16 ms; P > 0.05) and regional relaxation time (RT) (82 ± 19 vs 93 ± 21 ms; P > 0.05) in anterior wall (basal levels), which correspond to reciprocal ST segment depression on electrocardiography. According to E/A ratio detected by PWTD echocardiography in anterior wall and anterior septum, patients with reciprocal ST segment depression were also divided into two groups: Group A, with E/A ratio > 1; Group B, with E/A ratio < 1. Among the 35 patients with reciprocal ST segment depression, anterior wall ischemia was present in 10 patients and absent in 25 patients, whereas anterior septal ischemia was present 12 patients and absent in 23 patients. Conclusions: Reciprocal ST segment depression during the early phases of inferior infarction is an electrical reflection of primary ST segment elevation in the area of infarction.     

Predictive Value of P‐Wave Signal‐Averaged Electrocardiogram for Atrial Fibrillation in Acute Myocardial Infarction

Background: Atrial fibrillation (AF) is a common complication of acute myocardial infarction (AMI) with a reported incidence of 7–18%. Recently, P‐wave signal‐averaged electrocardiogram (P‐SAECG) has been used to assess the risk of paroxysmal AF attacks in some diseases. The aim of this study was to determine prospectively whether patients with AMI at risk for paroxysmal AF would be identified by P‐SAECG and other clinical variables. Methods: A total of 100 patients (mean age: 59 ± 12 , 77 male, 23 female) with ST segment elevation AMI were enrolled in this study. Patients with chronic AF were excluded. At entry, all patients underwent standard 12‐lead ECG and in the first 24 hours, P‐SAECG was taken, and echocardiography and coronary angiography were performed on the patients. Patients are followed for a month in terms of paroxysmal AF attacks and mortality. Results: AF was determined in 19 patients (19%). In patients with AF, abnormal P‐SAECG more frequently occurred than in patients without AF (37% vs 15%, P < 0.05) . Patients with AF were older (70 ± 14 vs 56 ± 10, P < 0.001) and had lower left ventricular ejection fraction (42%± 8 vs 49%± 11, P < 0.05) . AF was less common in thrombolysis‐treated patients (47% vs 74%, P <0.05) . Thirty‐day mortality was higher in patients with AF (16% vs 2%, P = 0.05) . Conclusions: An abnormal P‐SAECG may be a predictor of paroxysmal AF in patients with AMI. Advanced age and systolic heart failure were detected as two important clinical risk factors for the development of AF.     

T‐Wave Alternans: Reviewing the Clinical Performance,Understanding Limitations,Characterizing Methodologies

Accurate recognition of individuals at higher immediate risk of sudden cardiac death (SCD) is still an open question. The fortuitous nature of acute cardiovascular events just does not seem to fit the well‐known model of ventricular tachycardia/fibrillation induction in a static arrhythmogenic substrate by a synchronous trigger. On the mechanism of SCD, a dynamical electrical instability would better explain the rarity of the simultaneous association of a correct trigger and an appropriate cardiac substrate. Several studies have been conducted trying to measure this cardiac electrical instability (or any valid surrogate) in an ECG beat stream. Among the current possible candidates we can number QT prolongation, QT dispersion, late potentials, T‐wave alternans (TWA), and heart rate turbulence. This article reviews the particular role of TWA in the current cardiac risk stratification scenario. TWA findings are still heterogeneous, ranging from very good to nearly null prognostic performance depending on the clinical population observed and clinical protocol in use. To fill the current gaps in the TWA base of knowledge, practitioners, and researchers should better explore the technical features of the several technologies available for TWA evaluation and pay greater attention to the fact that TWA values are responsive to several factors other than medications. Information about the cellular and subcellular mechanisms of TWA is outside the scope of this article, but the reader is referred to some of the good papers available on this topic whenever this extra information could help the understanding of the concepts and facts covered herein.     

T‐Wave Variability Detects Abnormalities in Ventricular Repolarization: A Prospective Study Comparing Healthy Persons and Olympic Athletes

Background: Sudden cardiac death in athletes is more common than in the general population. Routine screening procedures are performed to identify competitors at risk. A new Holter‐based parameter analyzes variation of the ventricular repolarization (TVar). The aim of this study was to evaluate differences in electrocardiogram (ECG), Echo, and Holter (H) in competitive athletes compared to a healthy control group consisting of medical students (MS). Methods: A total of 40 athletes (19 females, Olympic team, Luxembourg) and 40 MS (22 females) were examined by means of a resting ECG, treadmill exercise (TE), echocardiogram (Echo), as well as H recordings during a routine screening visit. To analyze TVar, a 20‐minute H recording at rest (sampling rate 1000 per second) was performed. Moreover, heart rate variability (HRV) as well as HR turbulence (HRT) was computed. Results: No differences in demographic variables were detected. Quantification of HRV detected a significant increase in the vagal component of autonomic cardiac modulation. In contrast, no differences for HRT were found. Echo parameter demonstrated a thicker septal wall without differences of the posterior wall. TVar values were normal in range, but did differ significantly between the two groups. No correlation between TVar and echo as well as Holter parameters was detected. Conclusions: TVar was able to demonstrate significant differences in terms of alterations of ventricular activation. This might indicate an early change of myocardial repolarization representing a substrate for life‐threatening arrhythmia. Larger studies on the predictive value of TVar including follow‐up are necessary to confirm this preliminary finding.