Discussion
The most common causes of inappropriate ICD therapies are supraventricular tachycardia, especially AF or atrial flutter with rapid ventricular response, T‐wave oversensing, and lead dysfunction (noise and myopotentials)(5). Dislodgement and migration of cardiac implantable electronic device leads are not uncommon, however leads placement in inappropriate areas is extremely rare.
The coronary sinus (CS) has become a clinically important structure especially through its role in providing access for different cardiac procedures(6). Accurate knowledge of the coronary venous anatomy is essential for electrophysiologists performing left ventricular pacing procedures or radiofrequency ablation. In our case ICD lead implantation into the coronary sinus with AF led to inappropriate unsynchronized shock that returned AF to normal sinus rhythm. Probably, due to the normal R wave sensitivity and the tests of pacing threshold being performed without ECG in device controls, it was not noticed that the lead was not at the proper location. Another reason may be that chest x-rays are not interpreted correctly.
In some cases, implantation of the lead into the coronary sinus can be needed.Various conditions requiring implantation into the coronary sinus are as follows; anatomical barriers that preclude the passage through the valve such as atresia, stenosis and mechanical prosthesis, failed implantation into the ventricle, presence of persistent left superior vena cava with absence of right sided vein making the implantation near impossible, presence of abnormal ventricular substrate resulting in abnormal elevation of the capture threshold, and high defibrillation threshold(7-10).