Different Forms of Ventricular Tachycardia Involving the Left Anterior Fascicle in Nonischemic Cardiomyopathy: Critical Sites of the Reentrant Circuit in Low-Voltage Areas

Introduction: The purpose of this study was to examine the reentrant circuit of ventricular tachycardias (VTs) involving the left anterior fascicle (LAF) in nonischemic cardiomyopathy.
Methods and Results: Six patients with nonischemic cardiomyopathy presented with VTs involving the LAF. Potentials in the diastolic or presystolic phase of the VT were identified close to the LAF in 3 patients and in the mid or inferior left ventricular (LV) septum in 3 patients. Superimposed on a CARTO or NavX 3-dimensional voltage map, the diastolic and presystolic potentials were recorded within or at the border of a low-voltage zone in the LV septum in all cases. In 2 patients, both left bundle fascicles participated in the reentrant circuit including a possible interfascicular VT in one case. Ablation targeting the diastolic or presystolic potentials near the LAF or in the midinferior LV septum eliminated the VTs in all patients with the occurrence of a left posterior fascicular block and the delayed occurrence of a complete atrioventricular block in each one patient. During the follow-up of 23 ± 20 months after ablation, 4 patients were free of ventricular tachyarrhythmias. Due to detoriation of heart failure, one patient died after 12 months and one patient underwent heart transplantation after 40 months.
Conclusions: Slow conduction in diseased myocardium close to the LAF or in the middle and inferior aspects of the LV septum may represent the diastolic pathway of VT involving the LAF.     

Changes of QT Intervals Associated with Postural Change in Patients with Chronic Atrial Fibrillation

Although different computerized systems have been developed to localize specific patterns in electrocardiographic (ECG) signals, it is still difficult to detect T waves and measure QT intervals during atrial fibrillation. This article demonstrates the use of an auto-correlation (ECG) based system that was used to investigate the dynamicity of QT intervals related to active postural change in patients with chronic atrial fibrillation. Twenty patients (9 male, mean age 63 years) with chronic atrial fibrillation (8 idiopathic, 12 organic heart disease) were examined. Seventeen of these patients were on digoxin, but patients with other conditions potentially affecting the autonomic nervous system were not included. A 3-channel ECG was recorded digitally during active postural change from supine to standing. Data were first analyzed by the Burdick Altair system and subsequently processed using an in-house software package evaluating auto-correlations of ECG signals. An ECG channel with suitable repolarization patterns was found in 15 patients. The mean QT interval of 409.8 ± 11.1 ms (mean ± SE) recorded during supine position shortened to 401.9 ± 9.89 ms during the first minute of active standing (P < 0.05) and to 394.8 ± 10.0 ms during the second minute of active standing (P < 0.005). It did not further change during the subsequent minutes of active standing. The study shows that automatic detection of QT intervals during atrial fibrillation is possible. Although the effect of position change of the heart cannot be completely excluded, the study suggests that QT interval is changed directly by autonomic nervous mechanisms rather than indirectly via the mean heart rate.     

Factors Limiting Physical Working Capacity in Predialytic Uraemic Patients

ABSTRACT The exercise capacity of 20 predialytic uraemic patients (mean age 43±12 years) was studied prospectively. Nine of these patients were examined twice in a longitudinal study. The maximal working capacity, measured by standardized exercise test on a bicycle ergometer, averaged 74±19% of the expected normal. Normal exercise ECG were registered in 16 out of 20 patients. Total hemoglobinkg body weight (THb) was 67±16% of the expected normal and serum parathyroid hormone concentration (PTH) was 39±39 μg/l (normal range 0.5-1.5). Partial correlation showed a correlation between exercise capacity and PTH (p<0.05). In the longitudinal study the decrease in steady state exercise capacity was correlated to the decrease in THb (p<0.05), but not to the increase in PTH. In conclusion, patients with predialytic uraemia have a reduced maximal working capacity, due to several possible factors one of which is a reduced THb. Ischaemic heart disease seems to be of minor importance.