Health NZ Southern for the first time has successfully implanted a leadless pacemaker into a patient making the most of new technology.
Micra, is a leadless pacemaker, which is implanted directly into the heart and is 90 per cent smaller than a standard pacemaker.
Southern Cardiologist Dr Peter McLeod, who specialises in cardiac imaging and devices, says the pacemaker was used earlier this year for a patient that had specific needs.
The device is implanted under mild sedation. Under ultrasound guidance the patient’s femoral vein in the leg is accessed and used to place a large plastic tube (sheath) up to the heart. Through this tube, the device, attached to a steerable catheter-based delivery system, is manoeuvred, and implanted into the ventricular septum within the right ventricle of the heart.
Dr McLeod says the device has small hooks that deploy into the heart muscle to provide stability.
Ensuring two of the four hooks are attached to the heart muscle provides about 15 times the strength required to prevent embolization or dislodgement. The device is then tested electrically to ensure it senses the heart rhythm and can pace the heart muscle. The tube is then removed, and a stitch is put in to close the initial access site, which is then removed after three to four hours after which the patient may mobilise.
“This is an advancement on previous pacemaker technology. The main patients this may benefit are those who are small or frail, as well as patients with heart infections (endocarditis) as they have a very low risk of being infected while the device is implanted. There are also situations where these devices would be appropriate in younger patients as several can be implanted over a lifetime.
“It is also suitable for patients who have had heart valve surgery (tricuspid valve) where we cannot leave a pacing lead across this valve.”
As medical technology continues to progress, Dr McLeod is aware of the development of leadless devices that will pace both the atrium and ventricle.
Progress is also being made with pairing these devices with extracardiac (subcutaneous) defibrillators, which will be a big improvement for young people who require defibrillator and pacing devices who are at a higher lifelong risk of complications with standard transvenous systems. The Southern team is also grateful to Canterbury Cardiologist Dr Ross Downey and Medtronic Representative Rose Harrison, who both travelled to Dunedin Hospital to provide training and to assist the team with the procedure.
Southern Cardiac Physiologist Emma Guglietta says, “Our clinical staff are working alongside the manufacturers' representatives for support in the initial stages as the algorithms and the way this new leadless device monitors the heart rhythm is fairly complex and differs from standard pacemakers.”
Traditional dual chamber pacemakers detect heart rhythms using electrical signals to co-ordinate the top and bottom chambers (atria and ventricles) of the heart.
“This newer type only detects electrical signals in the bottom chamber (ventricle) the traditional way, and even though it is sited in the ventricle it detects signals from the top chamber (atria) using flow measurements. It can tell when there is a disconnect, also known as a heart block between the two chambers,” Emma says.
It is too early to say if leadless pacemaker will be used more predominantly in the future, as each patient’s needs will be different, but having the new technology available is a useful tool for cardiologists to access, Dr McLeod says.
Overall, Southern has about 2400 pacemaker/defibrillator patients that it looks after.
