SINUS NODE RECOVERY-TIME ASSESSMENT REVISITED - ROLE OF PHARMACOLOGICAL BLOCKADE OF THE AUTONOMIC NERVOUS-SYSTEM

Sinus node recovery time assessment is used to diagnose clinically sig nificant sinus node dysfunction (SND) when Holter has failed to prove a relationship between sinus bradyarrhythmias and symptoms, but consen sus has not been reached as to the value of including assessment after pharmacologic blockade of the autonomic nervous system, This issue wa s addressed in the present study performed on 52 patients with syncope or presyncope/dizziness (n = 38), sinus bradyarrhythmias (n = 35), or both (n = 41). Group 1 consisted of 13 patients with a proven relatio nship between symptoms and sinus bradyarrhythmias, Group 2 consisted o f 39 patients with suspected SND, The protocol included three pacing p eriods at two pacing rates and,vas performed at baseline (n = 52), aft er single doses of atropine and propranolol (0.02 mg/kg and 0.1 mg/kg, respectively) (n = 41), and again after a second dose (n = 29), The s ensitivity of prolonged recovery times was 77% in group 1, Among group 2 patients, 56% had prolonged recovery times at baseline (79% when in cluding the results after the first dose of drugs), The second dose di d not contribute diagnostic information, but it caused significant adv erse reactions in 7 of 29 patients (P < 0.001), These 7 patients were all older than 60 years, Assessment of sinus node recovery time after pharmacologic blockade of the autonomic nervous system thus increases the sensitivity of the method in patients with suspected SND and norma l baseline results, However, only 50% of the initially suggested doses of atropine and propranolol is sufficient and eliminates the risk for significant adverse reactions.