Fragmented QRS in prediction of cardiac deaths and heart failure hospitalizations after myocardial infarction.

BACKGROUND: Increased QRS fragmentation in visual inspection of 12-lead ECG has shown association with cardiac events in postmyocardial infarction (MI) patients. We investigated user-independent computerized intra-QRS fragmentation analysis in prediction of cardiac deaths and heart failure (HF) hospitalizations after MI. METHODS: Patients (n = 158) with recent MI and reduced left ventricular ejection fraction (LVEF) were studied. A 120-lead body surface potential mapping was performed at hospital discharge. Intra-QRS fragmentation was computed as the number of extrema (fragmentation index FI) in QRS. QRS duration (QRSd) was computed for comparison. RESULTS: During a mean follow-up of 50 months 15 patients suffered cardiac death and 23 were hospitalized for HF. Using the mean + 1 SD as cut-point both parameters were univariate predictors of both end-points. In multivariate analysis including age, gender, LVEF, previous MI, bundle branch block, atrial fibrillation, and diabetes FI was an independent predictor for cardiac deaths (HR 8.7, CI 3.0-25.6) and HF hospitalizations (HR 3.8, CI 1.6-9.3) whereas QRSd only predicted HF hospitalizations (HR 4.6, CI 2.0-10.7). In comparison to QRSd, FI showed better positive (PPA) and equal negative (NPA) predictive accuracy for both end-points, and PPA was further improved when combined to LVEF < 40%. Limiting fragmentation analysis to 12-lead ECG or a randomly selected 8-lead set instead of all 120 leads resulted in an almost similar prediction. CONCLUSIONS: Increased QRS fragmentation in post-MI patients predicts cardiac deaths and HF progression. A computer-based fragmentation analysis is a stronger predictor than QRSd.

Complex T-wave morphology in body surface potential mapping in prediction of arrhythmic events in patients with acute myocardial infarction and cardiac dysfunction.

AIMS: Heterogeneous ventricular repolarization is associated with sudden cardiac death after myocardial infarction (MI). This prospective study investigated repolarization disparity with parameters based on T-wave morphology in body surface potential mapping (BSPM) in the assessment of arrhythmia risk in patients with a recent MI and cardiac dysfunction. METHODS AND RESULTS: Patients (n = 158) had 120-lead BSPM and 12-lead electrocardiogram (ECG) registered soon after acute MI. Principal component analysis (PCA) of the T-wave and T-wave vector loop descriptors were applied to compute parameters describing T-wave morphology and its variation. The study endpoints were arrhythmic events and all-cause mortality. During a mean follow-up of 50 months, 30 patients (19%) died and 16 (10%) had an arrhythmic event. Most of the parameters differed significantly between patients with and without arrhythmic events. In univariate analysis, T-wave vector loop length (TLL) and PCA parameter PCA(3) in BSPM and TLL in ECG were significant predictors of arrhythmic events. In multivariate analysis including several clinical variables, these parameters also showed an independent prediction, with parameters in BSPM performing somewhat better. None of the parameters predicted all-cause mortality. CONCLUSION: Complex T-wave morphology in BSPM is a marker of arrhythmia propensity in patients with a recent MI and cardiac dysfunction.

Localization of prior myocardial infarction by repolarization variables.

BACKGROUND: To find quantitative, automatically applicable electrocardiographic (ECG) variables for detecting prior myocardial infarction (MI) in different myocardial regions. METHODS: Observational study. Body surface potential mapping (BSPM) was recorded at rest, and automatically analyzed with regard to ECG parameters, blinded to the clinical characteristics of the study subjects, 144 patients with prior MI and 75 healthy controls. MI location was determined by cine angiography or echocardiography as anterior (66 patients), inferoposterior (89 patients), and lateral (15 patients). Patients' 12-lead ECG was interpreted according to Minnesota code (Q-wave MI in 97 patients). The QRSSTT, QRS, and STT integrals, and the T-apex amplitude in detecting prior anterior and inferoposterior MI were analyzed. RESULTS: The T-apex amplitude, QRSSTT integral, and STT integral were functional in detecting MI in all tested locations on a single-lead basis, with areas under receiver operating characteristic curves (AUC) of over 90% (p<0.001) in optimal sites. In the best leads AUC for the QRSSTT integral in anterior MI was 93% (CI 87-99%) and for the inferoposterior MI 92% (CI 88-97%). These repolarization variables outperformed the Minnesota code in all tested MI locations. They were also able to distinguish between anterior and inferoposterior MI with an AUC of >85% (p<0.001). CONCLUSIONS: Quantitative, automatically applicable single-lead repolarization variables detect prior MI irrespective of its location. They may simplify the screening for and localization of old infarctions as compared to the conventional ECG methods.

Single-lead electrocardiographic variables in the detection of prior myocardial infarction with respect to Q-wave status and infarct age.

OBJECTIVES: Conventionally, the detection of prior myocardial infarction (MI) is based on QRS abnormalities, which may ignore non-Q-wave MI (NQMI). We aimed at finding automatically applicable quantitative ECG variables for diagnosing prior MI. METHODS: Body surface potential mapping (BSPM) was registered and automatically analyzed in 144 patients with prior MI and in 75 healthy controls. The MI was defined according to its age as recent or old, and Q-wave status as Q-wave MI (QMI) or NQMI. RESULTS: The QRSSTT integral, the STT integral and the T-wave apex amplitude applied in single, selected leads were found to be the optimal parameters in the detection of prior MI. The areas under the receiver-operating characteristic curves (AUC) were 89% for each, and detection was equal in old and recent MI (AUCs from 87 to 90%), and in QMI and NQMI (AUCs from 88 to 90%). CONCLUSIONS: The quantitative, automatically applicable single-lead variables comprising ventricular repolarization was effective in detecting prior MI, irrespective of the time elapsed from MI or the Q-wave status. These variables could be suitable for population studies and health screening purposes and are applicable to automatic ECG diagnostics of prior MI.

QRS duration in high-resolution methods and standard ECG in risk assessment after first and recurrent myocardial infarctions.

BACKGROUND: Prolonged QRS duration (QRSd) is associated with increased mortality after myocardial infarction (MI). Only little data exist about its predictive ability and relationships to clinical variables in the present era of active treatment of myocardial ischemia and cardiac dysfunction. We investigated whether QRSd in high-resolution methods and standard ECG predict arrhythmic events and cardiac death in post-infarction patients with cardiac dysfunction and how it relates to clinical variables, with a special emphasis on history of previous MI. METHODS AND RESULTS: Patients (n = 158) with acute MI and cardiac dysfunction had magnetocardiography (MCG), signal-averaged ECG (SAECG), and ECG registered at discharge. Patients with a previous MI had significantly longer QRSd although their left ventricular function was almost similarly impaired. During the mean follow-up of 50 +/- 15 (range 1-72) months, 32 patients died and 17 (53%) of the deaths were classified as cardiac. Eighteen patients had an arrhythmic event. QRSd >121 ms in MCG and >114 ms in SAECG were significant predictors of arrhythmic events and cardiac death, whereas QRSd in ECG predicted only cardiac death. In multivariate analysis, QRSd in MCG (hazard ratio (HR) = 3.6, P = 0.007) and SAECG (HR = 4.6, P = 0.016) predicted only arrhythmic events, whereas QRSd in ECG was an independent predictor of cardiac death. CONCLUSIONS: Prolonged QRSd in MCG and SAECG are powerful indicators of the arrhythmia substrate in post-infarction patients with cardiac dysfunction, whereas prolonged QRSd in standard ECG associates with increased risk of cardiac death.

Increased intra-QRS fragmentation in magnetocardiography as a predictor of arrhythmic events and mortality in patients with cardiac dysfunction after myocardial infarction.

INTRODUCTION: Increased intra-QRS fragmentation score (FRA) in magnetocardiography (MCG) has shown association with sustained ventricular arrhythmias in post-MI patients suggesting its relation to arrhythmia substrate. The aim of this study was to investigate whether increased FRA in MCG predicts arrhythmic events and mortality after acute myocardial infarction (MI) with cardiac dysfunction. METHODS AND RESULTS: A series of 158 patients with acute MI and left ventricular ejection fraction (LVEF) <50% were studied. Their age was 60 +/- 10 years and LVEF 40 +/- 6%. MCG was registered and FRA was computed. For comparison, QRS duration in 12-lead ECG was measured. In a mean follow-up of 50 +/- 15 months, 32 (20%) patients died and 18 (11%) had an arrhythmic event. Both arrhythmic event rate and all-cause mortality were significantly higher in patients with increased FRA (P < 0.001 for both). In contrast, increased QRS duration in ECG predicted all-cause mortality (P < 0.05) but not arrhythmic events. In multivariate analysis, FRA was an independent predictor of both arrhythmic events and all-cause mortality. Using a combined criterion of increased FRA and LVEF < 30% yielded positive and negative predictive accuracies of 50% and 91% for arrhythmic events. CONCLUSION: In post-MI patients with left ventricular dysfunction, increased intra-QRS fragmentation in high-resolution magnetocardiography predicts arrhythmic events, whereas QRS duration in 12-lead ECG predicts all-cause mortality. Analysis of intra-QRS fragmentation by MCG may assist in guiding therapy of post-MI patients, for example, by selecting those who would benefit most from prophylactic implantable cardioverter-defibrillator therapy.