Electrocardiogram of the failing heart.

In the failing heart general specific (e.g., Q-waves after acute myocardial infarction, persistent ST-elevations in post-myocardial infarction left ventricular aneurysm) and unspecific ECG changes (e.g., left bundle branch block, right bundle branch block, ST-T-alterations due to digitalis glycosides or antiarrhythmic drugs) may be seen in the conventional 12-lead ECG. In addition, atrial and ventricular tachy-arrhythmias may be detected and quantified by 24-hour-Holter ECG recordings, that may be relevant for a worse prognosis of patients with congestive heart failure. Heart rate variability as the most relevant derived ECG parameter of sympathetic tone fluctuations may be of important prognostic significance in congestive heart failure patients. An abnormal signal averaged P-wave duration may predict the incidence of atrial fibrillation, as may apply to QRS-prolongation and/or ventricular late potentials in the signal averaged ECG for the incidence of serious life-threatening ventricular tachy-arrhythmias or death from pump failure. Last but not least, cardiac repolarization abnormalities may be detected by QT dispersion-, QT-/QTc-fluctuation- or T-wave alternans studies, but the true prognostic significance of these parameters for predicting sudden cardiac death or death from pump failure in patients with congestive heart failure remains unclear.