18 Nov 09

Long-term outcome associated with early depolarisation on electrocardiography

Posted in Cardiac arrest/Resuscitation, ECG, Pre-operatie evaluation at 21:20 by Laci

By J Tikkanen, O Anttonen,  M Junttila, A Aro, T Kerola, H Rissanen, A Reunanen and H Huikuri

NEJM 2009;361:2529-2537

Early repolarization, which is characterized by an elevation of the QRS–ST junction (J point) in leads other than V1 through V3 on 12-lead electrocardiography, has been associated with vulnerability to ventricular fibrillation, but little is known about the prognostic significance of this pattern in the general population.

Methods
We assessed the prevalence and prognostic significance of early repolarization on 12-lead electrocardiography in a community-based general population of 10,864 middle-aged subjects (mean [±SD] age, 44±8 years). The primary end point was death from cardiac causes, and secondary end points were death from any cause and death from arrhythmia during a mean follow-up of 30±11 years. Early repolarization was stratified according to the degree of J-point elevation (0.1 mV or >0.2 mV) in either inferior or lateral leads.

Results
The early-repolarization pattern of 0.1 mV or more was present in 630 subjects (5.8%): 384 (3.5%) in inferior leads and 262 (2.4%) in lateral leads, with elevations in both leads in 16 subjects (0.1%). J-point elevation of at least 0.1 mV in inferior leads was associated with an increased risk of death from cardiac causes (adjusted relative risk, 1.28; 95% confidence interval [CI], 1.04 to 1.59; P=0.03); 36 subjects (0.3%) with J-point elevation of more than 0.2 mV in inferior leads had a markedly elevated risk of death from cardiac causes (adjusted relative risk, 2.98; 95% CI, 1.85 to 4.92; P<0.001) and from arrhythmia (adjusted relative risk, 2.92; 95% CI, 1.45 to 5.89; P=0.01). Other electrocardiographic risk markers, such as a prolonged QT interval corrected for heart rate (P=0.03) and left ventricular hypertrophy (P=0.004), were weaker predictors of the primary end point.

Conclusions
An early-repolarization pattern in the inferior leads of a standard electrocardiogram is associated with an increased risk of death from cardiac causes in middle-aged subjects.

10 Mar 09

T-Wave alternans and the susceptibility to ventricular arrhythmias

Posted in ECG at 10:25 by Laci

By S Narayan

J Am Coll Cardiol. 2006;47:269:281

Sudden cardiac arrest (SCA) claims over 400,000 lives per year in the U.S. alone, predominantly from ventricular tachycardia (VT) or ventricular fibrillation (VF). Although prophylaxis with the implantable cardioverter defibrillator (ICD) is extremely effective, identifying individuals who should receive such therapy remains challenging. Certainly, reduced systolic function and heart failure are sensitive indices of SCA risk, yet they identify populations in whom arrhythmic event rates may be low. From an individual as well as a public health perspective, there is therefore an urgent need for more accurate indices of lethal ventricular arrhythmias.

T-wave alternans (TWA) is a promising electrocardiographic (ECG) index that measures beat-to-beat alternation in T-wave shape, amplitude, or timing. Decades of research now link TWA with inducible and spontaneous clinical ventricular arrhythmias, and with basic mechanisms leading to their initiation. This bench-to-bedside foundation makes TWA a very plausible index of susceptibility to SCA, and motivates the need to define optimal conditions for its detection and clinical populations in whom its potential can be realized.

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