The invention provides compounds which are selective PDE2 inhibitors for use in the treatment of tachycardia or tachyarrhythmia. Such compounds are particularly suitable for use in the treatment of any of the following conditions: atrial tachycardia, atrial fibrillation, atrial flutter, paroxysmal supraventricular tachycardia, premature ventricular contractions (PVCs), ventricular fibrillation and ventricular tachycardia, and may be used alone or in combination therapy with other conventional cardiovascular drugs, e.g. beta-blockers. In particular, the invention provides compounds which are selective PDE2 inhibitors for use in the treatment of ventricular tachycardia in patients who are suffering from, or who are at risk of suffering from heart failure, CPVT or long QT syndrome.
