Markus Jerling

Electrophysiologic effects of a novel selective adenosine A1 agonist (CVT-510) on atrioventricular nodal conduction in humans.

Background: CVT-510, N-(3(R)-tetrahydrofuranyl)-6-aminopurine riboside, is a selective A,-adenosine receptor agonist with potential potent antiarrhythmic effects in tachycardias involving the atrioventricular (AV) node. This study, the first in humans, was designed to determine the effects of CVT-5 10 on AV nodal conduction and hemodynamics. Methods and Results: Patients in sinus rhythm with normal AV nodal function at electrophysiologic study (n = 32) received a single intravenous bolus of CVT-5 10. AH and HV intervals were measured during sinus rhythm and during atrial pacing at 1, 5, 10, 15, 20, 30, 45, and 60 minutes after the bolus. Increasing doses of CVT-510 (0.3 to 10 pg/kg) caused a dosedependent increase in the AH interval. At 1 minute, a dose of 10,ug/kg increased the AH interval during sinus rhythm from 93 ± 23 msec to 114 ± 37 msec, p = 0.01 and from 114 ± 31 msec to 146 ± 44 msec during atrial pacing at 600 msec, p = 0.003). The AH interval returned to baseline by 20 minutes. CVT-510 at doses of 0.3 to 10,ug/kg had no effect on sinus rate, HV interval, or systemic blood pressure, and was not associated with serious adverse effects. At doses of 15 and 30 pg/kg, CVT-510 produced transient second/third degree AV heart block in all four patients treated. One of these patients also had a prolonged sedative effect that was reversed with aminophylline. Conclusions: CVT-510 promptly prolongs AV nodal conduction and does not affect sinus rate or blood pressure. Selective stimulation of the A,-adenosine receptor by CVT-510 may be useful for immediate control of heart rate in atrial fibrillation/flutter and to convert paroxysmal supraventricular tachycardia to sinus rhythm, while avoiding vasodilatation mediated by the A2-adenosine receptor, as well as the vasodepressor and negative inotropic effects associated with 3-adrenergic receptor blockade and/or calcium channel blockers.

Trial to Evaluate the Management of Paroxysmal Supraventricular Tachycardia During an Electrophysiology Study With Tecadenoson

Background—Tecadenoson is a potent selective A1-adenosine receptor agonist with a dose-dependent negative dromotropic effect on the AV node. Tecadenoson terminates induced paroxysmal supraventricular tachycardia (PSVT) without the clinically significant side effects caused by stimulation of other adenosine receptors. This trial was designed to determine a safe and effective tecadenoson bolus for termination of electrophysiologically induced PSVT. Methods and Results—Patients with a history of symptomatic PSVT and inducible PSVT at the time of a clinically indicated electrophysiology study were randomized into a multicenter, double-blind, placebo-controlled trial. Five 2-dose tecadenoson bolus regimens were evaluated versus placebo (75/150, 150/300, 300/600, 450/900, 900 &mgr;g/900 &mgr;g). The second bolus was administered only if PSVT persisted for 1 minute after the first bolus. Each tecadenoson regimen resulted in a significant therapeutic conversion rate compared with placebo (range, 50.0% to 90.3%, analysis of all patients dosed; n=181; P<0.0005). Conversion by the first bolus was dose related (range: placebo, 3.3% to 86.7% for 900 &mgr;g/900 &mgr;g). Time to conversion was dose dependent, with a median time of <1 minute for the 3 highest dose regimens. Postconversion arrhythmias were transient, requiring no additional treatment in 4 regimens (including placebo). Transient second- and third-degree heart block occurred at higher doses (300/600, 450/900, 900 &mgr;g/900 &mgr;g) and was supported with backup pacing when needed. No effect on blood pressure was observed. Ten patients with a history of asthma or chronic obstructive pulmonary disease tolerated tecadenoson without bronchospasm. Conclusions—We identified an optimal tecadenoson regimen (300 &mgr;g/600 &mgr;g) that effectively and rapidly converted 90% (28 of 31) of PSVT patients to normal sinus rhythm with no significant adverse effects.