Transvenous device implant
Implant overview
Device pocket and position
Most common position
•Prepectoralis Fascia
•Should be under adipose tissue
•Too shallow (subcuticular) device presses on under surface of skin (“painful pocket”)
•Inferior to clavicle to allow shoulder mobility
•Medial to avoid anterior axillary fold (otherwise arm movements may be uncomfortable)
Pocket Size
•Too small/tight: risk of erosion
•Too big: excessive movement
Alternate pocket locations
•Submuscular: very thin patients
•Abdominal: small children
•Submammary: cosmetic/very thin
Submammary
Abdominal
Venous approaches
3 predominant approaches utilised
•Axillary (extrathoracic subclavian)
•Subclavian
•Cephalic
Axillary Vein
•Fast, low risk & facilitates multiple leads
•Uses the seldinger technique
•needle is directed towards the 1st rib to find the vein
•guidewire is then advanced through the needle into the heart
•the dilator is used and then sheath is positioned
•A peripheral contrast injection may be utilised to view vein
Subclavian vein
•Similar to axillary access
•Higher risk of complication to lung
•Vein enters at the junction of middle & inner 3rds of clavicle (medial)
•Medial approach – higher risk of subclavian crush
Cephalic vein
•Cut down, surgical approach
•Vein is situated within deltopectoral groove
•between deltoid and pectoralis major muscle
•Lowest risk of complication
•Sometimes too small for 2 leads
Lead positioning
When an active lead is positioned in an optimal/acceptable position, the screw is released to the myocardial tissue.
The appearance of the screw mechanisms varies between different manufacturers.
Lead testing
Lead is connected up to pacing cables via analyser
•Black lead tip
•Brown lead ring (bipolar) skin (uni)
Injury current
•Acute myocardial injury at lead tip
•Suggests adequate contact with myocardium
Loss of injury current and EGM inversion
•typically seen when myocardium is perforated
•Often accompanied by drop in impedance and increase in capture threshold/loss of capture
Sensing
•RA goal >2mV (minimal FFRW)
•RV goal >5mV
•Slew rate change in voltage/change in time (dV/dt) >0.5V/sec
Threshold
•RA & RV goal <1V@0.4ms
Impedances
•Slightly different depending on lead model
•Typically 200-1500 ohms
RV lead placement
Lead passed through sheath with straight or curved stylet
Lead passed down SVC, into RA and across the TV into RV
Lead positioned in optimal lead position
•RV apex: traditional position – now for HOCM, some defib leads, other exceptions
•Mid RV septum: optimal
•RVOT/high mid septum: doctor preference
Xray utilized to visualize lead position
•LAO confirm septal position
•RAO confirm lead is not anterior/inferior
Lead unscrewed
Lead tested
Lead slack is confirmed and lead secured from pocket end
RA lead placement
Lead passed through sheath with straight or curved stylet
Lead passed down SVC & into RA
Lead positioned in optimal lead position
•RA appendage standard position
•Lateral RA may be used if lead unstable in RAA or poor testing values (high threshold due to RAA scar from cardiac surg)
Xray utilized to visualize lead position
•AP medial position of lead
•RAO anterior position in line with RVA
Lead unscrewed
Lead tested
Lead slack is confirmed and lead secured from pocket end
