Development and progression of atrial fibrillation (AF) is driven by comorbidities such as arterial hypertension and diabetes mellitus. In animal models of chronic hyperglycaemia, progression of AF has been proposed to be triggered by oxidative stress, apoptosis and fibrosis. Acute glycosylation of CaMKII has been associated with increased susceptibility to arrhythmias in acute hyperglycaemia. However, the proarrhythmogenic effect of acute hyperglycaemia has not been investigated. Nine healthy, anesthetized pigs (54 +/- 6 kg) were instrumented with electrophysiologic catheters and a multielectrode array on the epicardium of the left atrial anterior wall. Left and right atrial effective refractory periods (AERP), inducibility of AF and left atrial epicardial conduction velocities (CV) were measured at baseline (BL), increasing steps of blood glucose (200-500 mg/dL in steps of 100 mg/dL by glucose infusion) and repeated after normalisation of blood glucose levels (recovery). Serum electrolytes were kept constant during measurements by means of sodium and potassium infusion. There were no significant differences in AERP, CV or AF inducibility between BL and recovery. Heart rate remained constant regardless of blood glucose levels (BL: 103 +/- 18 bpm, 500 mg/dL: 103 +/- 18 bpm, r=0.02, p=0.346). Mean left as well as right AERP increased with higher glucose levels. CV increased with glucose levels (1.25 (1.04, 1.67) m/s at BL vs. 1.53 (1.22, 2.15) m/s at 500 mg/dL, r=0.85, p=0.034). Rate of AF inducibility in the left atrium remained constant throughout the whole protocol (AF episodes >10 s: mean inducibility of 80% at BL vs. 69% at 500 mg/dL, p=0.32, episodes >30 s: 0% at BL vs. 0% at 500 mg/dL, p=0.17). Our data imply that acute hyperglycaemia is associated with lower arrhythmogenic substrate and does not promote AF inducibility.