Role of signal-averaged electrocardiography and ventricular late potentials in patients with chronic obstructive pulmonary disease.

Patients with chronic obstructive pulmonary disease (COPD) have an increased risk for cardiac arrhythmias. Ventricular late potentials (VLP) on signal-averaged electrocardiography (SAECG) are associated with an increased risk for malignant ventricular arrhythmias. Our aim is to investigate the modifications of SAECG parameters and the presence of VLP as possible indicators of proarrhythmic substrate in patients with COPD. We prospectively enrolled 41 consecutive patients in the COPD group and 63 patients without any history of pulmonary disease, matched for age and hypertension history, in the control group. Pulmonary function tests, arterial blood gases, echocardiography, 24-hour Holter monitoring and SAECG were performed. We measured total filtered QRS duration (QRSf), duration of high frequency, low-amplitude signals < 40 V (HFLA40), and root mean square voltage in the last 40 ms (RMS40). VLP were considered if at least two of these parameters were abnormal. Results. We did not register any significant differences in QRSf, HFLA40 or RMS40 between the two groups. In the COPD group there was a non-significant higher percentage of patients with VLP in comparison with the control group. In the COPD patients we registered a significantly higher number of isolated premature ventricular beats and of combined complex ventricular arrhythmias, consisting of polymorphic PVC, couplets, triplets or nonsustained ventricular tachycardias. None of these arrhythmic parameters correlated with SAECG variables or with the presence of VLP. Conclusion. In COPD patients parameters measured on signal-averaged electrocardiography and ventricular late potentials analysis have little value in risk stratification for ventricular arrhythmias.

Syncope in elderly patients--is there a place for endomyocardial biopsy?

Syncope in the aging population has two characteristics--it always has a multifactorial origin and age by itself is a predictor of a worse outcome even in syncope with an apparent benign mechanism. Therefore, it is worthwhile investigating extensively the cardiac substrate in selected cases when the initial evaluation demonstrates its presence. In the cases where the usual workup fails to unveil the cause for the decompensating heart substrate, morphological examination with endomyocardial biopsy should be taken into account, after matching every particular case with one of the clinical scenarios listed in the Scientific Statement on the role of endomyocardial biopsy in the management of cardiovascular disease.

The dynamic nature of ventricular tachycardia initiation.

Initiation of ventricular tachycardia (VT) or ventricular fibrillation (VF) requires heterogeneity of the substrate. This heterogeneity has a stable/fixed component (structural or functional) and a dynamic component. The latter explains the random and sudden destabilization of the substrate and the initiation of VT or VF by a ventricular extra stimulus trigger. The main mechanisms of dynamic heterogeneity are discussed at the cellular level (action potential duration alternans and restitution and intracellular calcium cycling instability) and at the tissue level (conduction velocity restitution and concordant and discordant alternans). Better knowledge of dynamic factors in arrhythmogenesis has an overwhelming impact on both predicting malignant arrhythmias and changing the antiarrhythmic drug paradigm from suppressing triggers to modifying dynamic instability factors.