New, less invasive defibrillator reduces risk of sudden cardiac death in more patients

Patients with abnormal heart rhythms now have a less invasive option to save them from sudden cardiac death.

Known as the subcutaneous implantable cardioverter defibrillator system (S-ICD), this life-saving procedure was introduced by doctors at the Department of Cardiology and Electrophysiology and Pacing service at the National Heart Centre Singapore (NHCS).

How implanted defibrillators help patients with abnormal heart rhythms

In a healthy individual, the heart contracts strongly, and rhythmically delivers blood to all parts of the body.

But in patients with abnormal heart rhythms, an electrical malfunction causes the heart to sometimes quiver or flutter dangerously fast. When that happens, blood cannot be pumped out to vital organs such as the brain. Within seconds, the patient may lose consciousness and if treatment is not given within minutes, the patient could suffer from sudden cardiac death.

An implanted defibrillator is a battery-powered device that is able to detect abnormal heart rhythms. A short electric impulse is then delivered to the heart to jolt it back to normal rhythm.

Differences between the current defibrillator and the S-ICD

Limitations of the conventional defibrillator

In the conventional defibrillator, there are wires which have leads on the ends. These are connected to the heart chambers. The leads can deliver impulses, generated by the device, directly to the heart.

“With the usual defibrillator, the heart is moving constantly, so the leads of the defibrillator are under a lot of stress. This can cause the wires to eventually wear out, and replacing them can be complicated,” said Adjunct Assistant Professor Tan Boon Yew, Senior Consultant, Department of Cardiology, National Heart Centre Singapore (NHCS), a member of the SingHealth group.

Benefits of the subcutaneous implantable cardioverter defibrillator system (S-ICD)

The S-ICD overcomes this issue because it has wires that go just under the skin and leads that do not touch the heart or veins. Current state-of-the-art technology enables it to deliver impulses even though the leads are not in direct contact with the heart.

Because the S-ICD is less invasive, the risk of lead-related infections in or near the heart is reduced. “Removing the wire in the S-ICD, if necessary, is also much easier because it is just under the skin,” said Dr Tan. Also unlike conventional defibrillators, placement of the leads does not require an x-ray, thereby reducing radiation exposure to the patient.

“Other problems associated with lead placement in a conventional ICD can be avoided too, such as the small risk of damaging the lungs or perforating the heart,” said Adjunct Associate Professor Ching Chi Keong, Senior Consultant, Department of Cardiology and Director, Electrophysiology and Pacing, National Heart Centre Singapore (NHCS), a member of the SingHealth group.

More people in Singapore able to use the S-ICD

In Singapore, about 1,800 cases of sudden cardiac arrest occur outside of hospitals each year.

Of these, only 12 per cent survive. Among those who did not make it were patients who needed an internal defibrillator, but were not suitable for the conventional treatment.

NHCS expects to see about 15 to 20 patients a year who would be suitable for this new treatment. People who can take advantage of the new S-ICD implantation now include patients on dialysis. Previously, they were unsuitable candidates because of limited access to their veins and heart, and being at a higher risk of infections.

Adults under 40, who are at risk of sudden cardiac arrest, can also use the new procedure. In this group of patients, there is a higher lifetime risk of lead problems such as leads becoming loose or damaged with the conventional technique. They can now be free of their biggest worry of suddenly suffering a cardiac arrest.

Ref: Q15