Bystander coronary sinus diverticulum and left anterolateral accessory pathway.

Left posteroseptal accessory pathways have been described inside coronary sinus diverticula. We here describe the case of a patient who was suffering from recurrent episodes of paroxysmal supraventricular tachycardia and had a concealed accessory pathway located in the left anterolateral margin of the mitral annulus and a left posterior coronary sinus diverticulum associated with an aneurysmal coronary sinus vein. In the electrophysiological study, an orthodromic supraventricular tachycardia was induced and reproduced. We performed a successful radiofrequency ablation of the pathway. Our case provides evidence of the coexistence of concealed accessory pathways capable of sustaining orthodromic tachycardia coexisting with a bystander posterior coronary sinus diverticulum and aneurysmal coronary sinus vein.