ISTANBUL, TURKEY. Paroxysmal (intermittent) atrial fibrillation is an increasingly common heart arrhythmia. The condition may be associated with heart disease or it may have no known cause in which case it is classified as lone, primary or idiopathic atrial fibrillation (AF). It is believed that the arrhythmia is initiated by irregularities in autonomic tone (imbalances between the sympathetic and parasympathetic nervous systems) which causes a slowed and nonuniform progression of the atrial impulse. This progression is represented by the so-called P-wave dispersion on a standard 12-lead electrocardiogram.
Researchers at the Istanbul Faculty of Medicine now report that the P-wave dispersion during an atrial fibrillation attack is much longer than in normal controls (60 milliseconds vs. 37 milliseconds). Their clinical study involved 27 patients with AF and 27 controls with no history of heart problems. Almost half (48 per cent) of the patients suffered from lone atrial fibrillation. All participants had their electrocardiograms taken before, during, and after performing the Valsalva maneuver (exhaling into a mercury manometer with enough force to reach 35 mm Hg pressure and sustaining this pressure for 20 seconds). The AF patients were evaluated during an attack.
The researchers noted that the P-wave dispersion increased markedly in the controls after performing the Valsalva maneuver (from 37 ms to 47 ms). On the other hand, in the patients the P-wave dispersion declined from 60 to 45 ms indicating a pronounced decrease in sympathetic activity. They conclude that the Valsalva maneuver normalizes the P-wave duration and dispersion in AF patients and suggest that medications that decrease sympathetic tone may be beneficial in converting AF to sinus rhythm.
Tukek, Tufan, et al. Effect of Valsalva maneuver on surface electrocardiographic P-wave dispersion in paroxysmal atrial fibrillation. American Journal of Cardiology, Vol. 85, April 1, 2000, pp. 896-99