Technique of CRT implantation
Technique of CRT implantation – CRT stands for cardiac resynchronization therapy or biventricular pacing with an additional atrial lead for atrioventricular synchrony. When a defibrillator is also needed, which is often the case, the device is called CRT-D. Plain CRT is also called CRT-P where P stands for pacing.
Basic cannulation of coronary sinus
Start ventricular to tricuspid valve and withdraw applying counterclockwise torque to stay septally to cannulate the coronary sinus ostium. LAO (left anterior oblique view) is lined upon the interventricular septum. The orthogonal view is RAO (right anterior oblique view). A prominent Thebesian valve with an associated pouch causes the lead to fall into it and cause difficulty in cannulating the coronary sinus (CS). Injecting a whiff of dye will help delineate the position of the sheath in the pouch, which causes transient dye stasis.
Inability to advance in coronary sinus
Inability to advance in CS could be due to stenosis, valves, subselection, dissection and tortuosity. Vieussens valve is an embryonic remnant, seen at the origin of the posterolateral ventricular vein. If there is a prominent valve in the posterolateral vein, we can cannulate the middle cardiac vein and go into a lateral branch of this vein. CS stenosis can be balloon dilated, but branch vein stenosis is better left alone. Search for other veins which could be used. This will also reduce the dye load in attempted dilatation. Dissections can occur due to dye injections and by sheath advancement. In most of the dissections it is still possible to get a wire across and proceed. Otherwise if the dissection is distal, try using the lateral branch of the middle cardiac vein. Pushing a catheter which is sub selected without recognizing it is one of the reasons for dissection. If it is atrial vein subselection, withdraw it. If it is ventricular vein subselection, your cannulation is over! So try to recognize it with appropriate views.
Inability to get lateral veins
In case of inability to get to lateral veins through a posterolateral vein, try lateral branches of middle cardiac vein or anterior interventricular vein. It is not important how you reach the lateral wall.
The ideal site to aim for the left ventricular lead is the lateral wall, mid position.
Need for ICD lead in left ventricle
When there is a mechanical tricuspid valve which you don’t want to cross, an ICD (implantable cardioverter defibrillator) lead can be placed in a coronary vein.