Subcutaneous defibrillator prevents sudden cardiac death

More than 15,000 people a year die of sudden cardiac death in Austria. The main causes are heart rhythm disturbances such as atrial fibrillation or persistent ventricular tachycardia, which ultimately lead to cardiac arrest and, in 80% of cases, are the result of a circulatory problem in coronary heart disease. However, it can also be caused by other myocardial disorders such as various forms of cardiomyopathy or congenital diseases affecting cardiac rhythm, which can also produce arrhythmic conditions.

Implantable defibrillators, so-called ICDs, are the most effective method of preventing sudden cardiac death. In the event of malignant cardiac arrhythmia, the implanted device emits an electric shock that ends the arrhythmia and restores the normal cardiac rhythm. Such a device was implanted into the first patient in Austria almost 30 years ago to the day.

Older models suffer from mechanical wear
The first ICDs were quite big and were initially implanted in the abdomen and connected to electrodes sewn directly onto the heart, so that implantation was a major procedure. The devices have become smaller and smaller over time and are now routinely implanted under the collarbone, like a heart pacemaker. The electrodes are introduced into the heart via the major veins (transvenously), where they are directly attached in the right ventricle. If required, the implanted device emits an electric shock via the electrode.
These electrodes located right in the heart are subject to mechanical loadings due to contraction of the heart muscle and these loadings can impair their function over time. Especially in younger patients, who are physically active, the insulation can wear away at the point of insertion into the vascular system underneath the collarbone, causing an electrode fault. If this happens, the faulty electrode has to be surgically replaced and this is a risky procedure.

Since 2009, subcutaneous implantable defibrillators – S-ICD – which do not require any electrodes in the heart, have also been available. The device is implanted on the left side of the chest and connected to an electrode running under the skin next to the breastbone. In this device, the electrode is under the skin (subcutaneous) and is therefore subject to less loading than transvenous sensors. These sensors last much longer, as they are not damaged in use. Moreover, this system leaves the heart and blood vessels completely untouched.

300th S-ICD in Austria implanted in Vienna General Hospital
This new form of treatment is becoming increasingly important. Whereas, prior to 2016, around 13,000 of these subcutaneous S-IDC systems had been implanted, the same number were implanted in 2016 alone. The number of these subcutaneous defibrillator systems to be implanted is also increasing in Austria. Only recently, the team in Vienna General Hospital implanted the 300th S-ICD in Austria (electrophysiological cardiac surgery team comprising: Cesar Khazen, Thomas Aschacher, Martin Andreas, under the direction of the Division of Cardiac Surgery, Günther Laufer). Over the course of the last few decades, Vienna General Hospital has become a nationally important coronary care centre. It is increasingly in demand for managing complications associated with transvenous electrodes.