[Sinoatrial and intra-atrial conductive disorders. The value of recording the sinus node potential]

Direct recording of the sinus node potential in the bipolar mode using two electrodes of a quadripolar recording catheter positioned in the region of the sinus node at the junction of the superior vena cava to the right atrium was performed in 24 patients. Asynchronous overdrive atrial pacing was carried out using Strauss 'technique. Pharmacological denervation was carried out using intravenous propranolol (0,02 mg/kg) and atropine (0,04 mg/kg) using Jose's technique. An intravenous injection of a bolus of 20 mg of ATP was given in 3 cases. The sinus potential was identified by morphological criteria and confirmed after carotid sinus compression and atrial extrastimuli to exclude artefacts, especially the end of ventricular repolarisation of the preceding complex. The sinoatrial conduction time measured directly under basal conditions was considered normal when within 80 to 150 ms. Direct measurement of the sinus potential in the diagnosis of sinus node dysfunction seems to be less useful than the indirect techniques. On the other hand, it does confirm the diagnosis of sinoatrial block: five cases of special interest are described; in four cases the degree of sinoatrial block was variable: a significant increase of sinoatrial conduction time under basal conditions in 1 case; paroxysmal 3rd degree sinoatrial block revealed by programmed atrial stimulation in 2 cases; 2nd degree 2/1 sinoatrial block after injection of ATP in which the direct sinoatrial conduction time and sinus node function had been considered to be normal (1 case).(ABSTRACT TRUNCATED AT 250 WORDS)