QRS Duration in High-Resolution Methods and Standard ECG in Risk Assessment After First and Recurrent Myocardial Infarctions

Magnetocardiography in the Evaluation of Sudden Cardiac Death Risk: A Systematic Review

Sudden cardiac death (SCD) is responsible for 15%-20% of deaths globally/year, predominantly due to ventricular arrhythmias (VA) caused by vulnerable cardiac substrate. Identifying those at risk has proved difficult with several limitations of current methods. We evaluated the evidence for magnetocardiography (MCG) in predicting SCD events. We searched Embase/Medline databases for English language papers evaluating MCG in patients at risk of VA. A total of 119 papers were screened with 27 papers included for analysis (23 case-controlled, four cohort studies); study sizes varied (n = 12 to 158). Etiology was ischemic cardiomyopathy (ICM) in 22, dilated cardiomyopathy in 2, arrhythmogenic cardiomyopathy in 1 and mixed in 2. In patients with ICM there were consistent discriminatory features seen using time-based and signal-complexity measures that persisted when evaluating the independence of these parameters. Current flow analysis demonstrated promising discriminatory results in other etiologies. The features studied support the role of MCG in identifying substrate for VA, particularly in ICM.

Magnetocardiography for the detection of myocardial ischemia

Ischemic heart disease (IHD) continues to be a significant global public health concern and ranks among the leading causes of mortality worldwide. However, the identification of myocardial ischemia in patients suspected of having coronary artery disease (CAD) remains a challenging issue. Functional or stress testing is widely recognized as the gold standard method for diagnosing myocardial ischemia, but it is hindered by low diagnostic accuracy and limitations such as radiation exposure. Magnetocardiography (MCG) is a non-contact, non-invasive method that records magnetic fields produced by the electrical activity of the heart. Unlike electrocardiography (EKG) and other functional or stress testing, MCG offers numerous advantages. It is highly sensitive and can detect early signs of myocardial ischemia that may be missed by other diagnostic tools. This review aims to provide an extensive overview of the available evidence that establishes the utility of MCG as a valuable diagnostic tool for identifying myocardial ischemia, accompanied by a discussion of potential future research directions in this domain.

Utility of a novel risk score for prediction of ventricular tachycardia and cardiac death in chronic Chagas disease - the SEARCH-RIO study

The SEARCH-RIO study prospectively investigated electrocardiogram (ECG)-derived variables in chronic Chagas disease (CCD) as predictors of cardiac death and new onset ventricular tachycardia (VT). Cardiac arrhythmia is a major cause of death in CCD, and electrical markers may play a significant role in risk stratification. One hundred clinically stable outpatients with CCD were enrolled in this study. They initially underwent a 12-lead resting ECG, signal-averaged ECG, and 24-h ambulatory ECG. Abnormal Q-waves, filtered QRS duration, intraventricular electrical transients (IVET), 24-h standard deviation of normal RR intervals (SDNN), and VT were assessed. Echocardiograms assessed left ventricular ejection fraction. Predictors of cardiac death and new onset VT were identified in a Cox proportional hazard model. During a mean follow-up of 95.3 months, 36 patients had adverse events: 22 new onset VT (mean±SD, 18.4±4/year) and 20 deaths (26.4±1.8/year). In multivariate analysis, only Q-wave (hazard ratio, HR=6.7; P<0.001), VT (HR=5.3; P<0.001), SDNN<100 ms (HR=4.0; P=0.006), and IVET+ (HR=3.0; P=0.04) were independent predictors of the composite endpoint of cardiac death and new onset VT. A prognostic score was developed by weighting points proportional to beta coefficients and summing-up: Q-wave=2; VT=2; SDNN<100 ms=1; IVET+ =1. Receiver operating characteristic curve analysis optimized the cutoff value at >1. In 10,000 bootstraps, the C-statistic of this novel score was non-inferior to a previously validated (Rassi) score (0.89±0.03 and 0.80±0.05, respectively; test for non-inferiority: P<0.001). In CCD, surface ECG-derived variables are predictors of cardiac death and new onset VT.

Diagnostic value of magnetocardiography in coronary artery disease and cardiac arrhythmias: a review of clinical data

Despite the availability of several advanced non-invasive diagnostic tests such as echocardiography and magnetic resonance imaging, electrocardiography (ECG) remains as the most widely used diagnostic technique in clinical cardiology. ECG detects electrical potentials that are generated by cardiac electrical activity. In addition to electrical potentials, the same electrical activity of the heart also induces magnetic fields. These extremely weak cardiac magnetic signals are detected by a non-invasive, contactless technique called magnetocardiography (MCG), which has been evaluated in a number of clinical studies for its usefulness in diagnosing heart diseases. We reviewed the basic principles, history and clinical data on the diagnostic role of MCG in coronary artery disease and cardiac arrhythmias.

Effects of early losartan therapy on ventricular late potentials in acute myocardial infarction

BACKGROUND

Ventricular late potentials (LPs) obtained by the signal-averaged electrocardiogram (SAECG) have prognostic significance as independent predictors of arrhythmic events after an acute myocardial infarction (AMI). Angiotensin receptor blockers reduce the overall mortality and risk of sudden cardiac death in postinfarction patients. The aim of this study was to investigate the effect of early losartan therapy on ventricular LPs, a noninvasive method for the evaluation of arrhythmogenic substrates in AMI patients.

METHODS

The study included 97 patients with their first AMI. Forty-eight patients (39 men and 9 women, aged 58.8 +/- 13.19 years), received early losartan therapy. The control group consisted of 49 patients (38 men and 11 women, aged 59.55 +/- 11.0 years), did not received early losartan therapy. The SAECG was performed at admission and day 14.

RESULTS

The baseline clinical, angiographic characteristics, and reperfusion methods were similar in both groups. The baseline SAECG findings were also similar in the two groups. There was a significant decrease in the rate of LP, between the first and last SAECG recordings, after reperfusion therapy in the losartan group. All of the parameters of LPs were significantly improved in the losartan group on the last SAECG recordings.

CONCLUSION

The results of this study showed that losartan treatment, early after an AMI, reduced the incidence of LP and may thus favorably affect arrhythmia substrates.

Prediction of arrhythmic events after myocardial infarction based on signal-averaged electrocardiogram and ejection fraction

BACKGROUND

Trials on implantable cardioverter-defibrillators (ICD) for patients after acute myocardial infarction (AMI) have highlighted the need for risk assessment of arrhythmic events (AE). The aim of this study was to evaluate risk predictors based on a novel approach of interpreting signal-averaged electrocardiogram (SAECG) and ejection fraction (EF).

METHODS

SAECG, interpreted with a new index, and EF were prospectively evaluated to predict AE in 144 patients with AMI.

RESULTS

During the mean follow-up period of 4.1 years, 19 AE occurred. The new SAECG index showed a sensitivity of 84%, a specificity of 62%, a positive predictive value (PPV) of 25%, and a negative predictive value (NPV) of 96%. A combination of a normal new SAECG index and an EF >35% resulted in a sensitivity of 100%, a specificity of 47%, a PPV of 22%, and a NPV of 100%; this corresponded to an AE incidence rate of 0%. When both tests were abnormal, the AE incidence rate was 21.3%.

CONCLUSIONS

This is the first contemporary study reporting predictive values based on a combination of SAECG and EF. If confirmed in an appropriately designed and powered trial, this novel approach might be used to identify both patients at very low risk for AE not requiring further risk assessment and patients at high risk in whom ICD implantation can be considered without further risk assessment.

Relationship between QRS duration and prognosis in non-ST-segment elevation acute coronary syndrome

BACKGROUND

Previous studies have shown that prolonged QRS duration increases the risk of death in patients with heart failure and after an ST-segment elevation acute myocardial infarction. Very little data exist about the prognostic implications of QRS duration in the non-ST-segment elevation acute coronary syndrome (NST-ACS): unstable angina and non-ST elevation acute myocardial infarction (non-STEMI).

METHODS

This is a prospective and observational study in which we included 502 patients (age 71+/-10 years, 68% males, 29% diabetes) consecutively admitted for NST-ACS. QRS duration was manually measured from the 12-lead electrocardiogram. Our aim is to assess the relation between the QRS duration on admission (QRSd) and the risk of cardiovascular death (CvD) in the long-term.

RESULTS

Mean QRSd was: 93+/-19 ms. After a median follow-up of 450 days, the cumulative incidence of CvD was: 17.8%. QRSd correlated with the incidence of CvD during the follow-up period: c=0.72 (p<0.001). The best cut-off point was 90 ms (sensitivity, specificity and negative predictive value of QRSd>or=90 ms for CvD: 82, 68 and 93%). According to the Kaplan-Meier analysis, QRSd>or=90 ms was associated with an increase in the risk of CvD: 26.6% versus 7.2% (log rank: 28.6; p<0.001). Cumulative incidence of CvD was higher in QRSd>or=90 ms in patients with unstable angina: 15.5% versus 4% (p=0.02), and in those with non-STEMI: 30.5% versus 8.9% (p<0.001). After adjusting for other significant variables (Cox-regression analysis), QRSd>or=90 ms persisted as an independent predictor for overall CvD (Hazard Ratio: 2.62; 95% Confidence Interval: 1.44-4.74; p<0.001).

CONCLUSION

In NST-ACS, the QRSd, even in the normal range, has prognostic implications. QRSd>or=90 ms is independently associated with an increased risk of CvD in the long-term.