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).