Termination of Atrial Flutter and Fibrillation by K201's Metabolite M-II: Studies in the Canine Sterile Pericarditis Model.

INTRODUCTION: K201, a 1,4-benzodiazepine derivative, acts on multiple cardiac ion channels and the ryanodine receptor. We tested whether administration of M-II, the main metabolite of K201, would terminate induced atrial flutter (AFL) or atrial fibrillation (AF) in the canine sterile pericarditis model. METHODS: In 6 dogs, electrophysiologic studies were performed at baseline and after drug administration, measuring atrial effective refractory period (AERP), and conduction time from 3 sites during pacing at cycle lengths (400, 300, and 200 milliseconds) on postoperative days 1-4. In 12 induced episodes of sustained AF/AFL (2/10, respectively), M-II was administered intravenously to test efficacy. Five of the AFL episodes were studied in the open chest state during simultaneous multisite atrial mapping. RESULTS: M-II terminated 2/2 AF and 8/10 AFL episodes, prolonged AERP (P < 0.05), significantly increased atrial pacing capture thresholds but did not significantly change atrial conduction time. AFL CL prolongation was largely explained by prolonged conduction in an area of slow conduction in the reentrant circuit. AFL terminated with block in the area of slow conduction. CONCLUSIONS: M-II was very effective in terminating AFL/AF in the canine sterile pericarditis model. AFL terminated due to block in the area of slow conduction of the reentrant circuit.

The effects of KW-3902, an adenosine A1-receptor antagonist,on diuresis and renal function in patients with acute decompensated heart failure and renal impairment or diuretic resistance.

OBJECTIVES: This study sought to evaluate the dose-dependent effects of adenosine A1-receptor blockade on diuresis and renal function in patients with acute decompensated heart failure (ADHF) and renal impairment or diuretic resistance. BACKGROUND: Intravenous loop diuretics are the mainstay of therapy for patients with ADHF. Treatment, however, may be complicated by diuretic resistance and/or worsening renal function. METHODS: We carried out a pair of randomized, double-blind, placebo-controlled, proof-of-concept studies in 2 clinically challenging ADHF populations. RESULTS: In the ADHF protocol, 146 patients with volume overload and an estimated creatinine clearance (CrCl) of 20 to 80 ml/min were randomized to placebo or 1 of 4 doses of KW-3902 (rolofylline) infused over 2 h daily for up to 3 days. On day 1, KW-3902 monotherapy increased urine output during the first 6 h (445, 531, 631, and 570 ml in the 2.5-, 15-, 30-, and 60-mg groups, respectively) compared with placebo (374 ml; p = 0.02). On day 2, serum creatinine decreased in all KW-3902 groups and increased with placebo (p = 0.04). By day 4 or day of discharge if earlier, intravenous furosemide administration tended to be lower in the KW-3902 groups compared with placebo (p = 0.10). In the diuretic-resistant protocol, 35 patients with an average CrCl of 34 ml/min were randomized to a single infusion of placebo, 10, 30, or 60 mg of KW-3902. Compared with placebo, KW-3902 increased hourly urine volume and estimated CrCl with peak effects occurring at 2 to 3 h and at 24 h, respectively. Adverse events were not different between placebo and KW-3902. CONCLUSIONS: In patients with ADHF and volume overload, KW-3902, an adenosine A1-receptor antagonist, enhances the response to loop diuretics and may have a renal protective effect.