Situs inversus totalis: A challenge for cardiac resynchronization therapy.

Situs inversus totalis (SIT) is a congenital condition in which the major visceral organs are reversed or in a mirror image from their normal positions that affects one per 10,000 live births. It is associated with dextrocardia (DXC) in which the heart is located on the right side of the chest. We present a challenging cardiac resynchronization therapy (CRT) implantation in a 60-year-old man with SIT-DXC, heart failure, extreme bradycardia, wide QRS, and left ventricular (LV) dysfunction. The procedure was complex due to the mirror-image anatomy and the tortuous origin of the coronary sinus (CS) branches that required a subselection catheter for adequate lead implantation.