Is ventricular repolarization heterogeneity a cause of serious ventricular tachyarrhythmias in aortic valve stenosis?

Predictors of syncope in patients with severe aortic stenosis: The role of orthostatic unload test

BACKGROUND

There is a paucity of data regarding response of cerebral blood flow to the postural unloading maneuver and its impact on the risk of syncope in patients with aortic stenosis (AS). The aim of the present study was to assess effects of orthostatic stress test on changes in carotid and vertebral artery blood flow and its association with syncope in patients with severe AS.

METHODS

108 patients were enrolled (72 with and 36 patients without syncope) with severe isolated severe AS. Peak systolic blood-flow velocity (PSV) and end-diastolic velocity in the carotid arteries and vertebral arteries were measured by duplex ultrasound in the supine position and at 1-2 min after the assumption of the standing position.

RESULTS

The orthostatic stress test induced a significant decrease in carotid and vertebral arterial flow velocities in all examined arteries (p < 0.001). The median (interquartile range) of mean change in PSV for carotid arteries was higher for patients with syncope (syncope [-] vs. syncope [+]: -0.6 cm/s [-1.8, 1.0] vs. -7.3 cm/s [-9.5, -2.0]; p < 0.001) and similarly for vertebral arteries (-0.5 cm/s [-2.0, 0.5] vs. -4.8 cm/s [-6.5, -1.3]; p < 0.001, respectively). Age, aortic valve area, and mean change in PSV for carotid arteries were independently associated with syncope.

CONCLUSIONS

In patients with AS, a decrease in carotid and vertebral arterial flow velocities in the standing position was observed and was associated with syncope. The present findings may support the value of an orthostatic test in identifying patients with severe AS and a high risk of syncope.

Torsades de pointes as a cause of sudden death in a patient with aortic stenosis and atrial fibrillation

The occurrence of sudden cardiac death during Holter monitoring in patients with aortic stenosis has been reported previously. In the majority of the reported cases, the cause of death was a malignant ventricular tachyarrhythmia. The presence of a strong association between frequency and complexity of ventricular arrhythmias and sudden death in patients with aortic stenosis has been proposed. We report the case of a 77-year-old woman with aortic stenosis and atrial fibrillation who had an episode of torsades de pointes that degenerated into ventricular fibrillation during Holter monitoring. A short-long-short sequence, but not increased ventricular ectopics, precipitated torsades de pointes and sudden death in this case which is strongly indicative of triggered activity as the underlying mechanism of the lethal arrhythmia.

Vulnerability to ventricular arrhythmias [corrected] and heterogeneity of action potential duration in normal rats

In normal rats, we analysed the arrhythmogenic role of intrinsic action potential duration (APD) heterogeneity. In each animal, ventricular arrhythmic events (VAEs) occurring spontaneously and during the exposure to an acute social challenge were telemetrically recorded. Action potentials were recorded from isolated left ventricular myocytes, at a pacing rate of 5 Hz (patch clamp: current-clamp mode). APDs were measured at -20 mV, -30 mV, -40 mV, -50 mV and -60 mV. The difference between the shortest and the longest APD was also computed, as an index of individual APD heterogeneity. Animals predisposed to stress-induced arrhythmias showed higher values of APD and APD heterogeneity as compared with the remaining rats. We concluded that, in the normal heart, a large intrinsic APD heterogeneity resulting from specific electrophysiological properties of ventricular myocytes is not in itself arrhythmogenic, but can predispose towards arrhythmia development under certain conditions, such as autonomic activation.