Can an S-ICD provide pacing therapy?
No, not in the conventional sense. This is the most clinically important difference between an S-ICD and a standard transvenous ICD.
An S-ICD can deliver brief post-shock pacing — a short burst of pacing in the seconds immediately after it has delivered a defibrillation shock, to prevent the heart pausing dangerously in that window. But it cannot provide ongoing bradycardia pacing (pacing that keeps the heart from beating too slowly on a continuous basis) or anti-tachycardia pacing (ATP, which is rapid pacing used to interrupt a fast heart rhythm before it needs a shock).
This means an S-ICD is not appropriate if:
- You have a slow heart rate that requires a pacemaker to maintain an adequate rate
- You have a type of fast heart rhythm that can be reliably terminated with ATP, which is less painful than a full shock
Some patients who need both ICD protection and pacing have an S-ICD combined with a separate leadless pacemaker (such as the Micra device), which sits inside the right ventricle and handles pacing without transvenous leads. This combination is used in selected cases where both subcutaneous defibrillation and pacing are needed but traditional transvenous leads are undesirable. Your electrophysiologist will determine which configuration is right for you.
Category: Implantable DevicesWhat is a CRT-D and how is it different from a standard ICD?
A CRT-D (cardiac resynchronisation therapy defibrillator) is a device that combines two functions in one: a biventricular pacemaker and an implantable defibrillator.
The biventricular pacing component (the CRT part) sends precisely timed electrical signals to both the left and right ventricles, helping them contract in better synchrony with each other. In people whose ventricles are out of step — a condition that shows up on an ECG as a wide QRS complex — this can significantly improve the efficiency of the heart’s pumping action. The defibrillator component works exactly like a standard ICD: it monitors the heart rhythm continuously and delivers a shock if a life-threatening arrhythmia is detected.
A CRT-D typically has three leads rather than the one or two used in a standard ICD. The extra lead is positioned via the coronary sinus, a vein on the back of the heart, to pace the left ventricle directly. This three-lead system makes the implant procedure more complex than a standard ICD implant.
Category: TreatmentDo magnets affect pacemakers and implantable defibrillators?
Even though most electromagnetic fields in the home environment will rarely affect the function of a pacemaker or ICD, it is recommended you keep any item containing magnets at least 15cm (6 inches) away from your device.
The reason for this is that there is a small magnetically activated switch built into pacemakers and ICDs. This internal switch is designed to close when a magnet of sufficient strength is placed over it.
When the switch closes in a pacemaker, the device paces the heart at a fixed pre-set rate (which may differ from your programmed settings).
When the switch closes in an ICD, it prevents the device from delivering treatment therapies.
You may not always know whether an item contains a magnet. However, if household items are used as intended and properly maintained, they should have no effect on your heart device. This includes microwaves, kitchen appliances, cordless phones, radios, televisions, computers, hair dryers, electric shavers, electric toothbrushes, electric blankets, and small power tools.
If you accidentally place a magnet too close to your device, simply move the item away. The pacemaker or ICD will return to its normal programmed settings once the magnet is removed.
The use of magnetic mattress pads and pillows is not recommended as it would be difficult to maintain a 15cm (6 inch) separation from your device at all times.
Category: Implantable DevicesWhat does DDD and VVI mean?
DDD and VVI are pacemaker therapy modes that your doctor can program in your device. These are just two of many options. Each letter indicates something different (A=Atrium; V=Ventricle; D=Dual or both A and V; and O=none). The first letter indicates the chamber of the heart being paced. The second letter is the heart chamber being sensed. The third letter indicates how the device should respond when it senses a cardiac event (T=Triggered; I=Inhibited; D=Trigger or Inhibit; and O=none). Finally, the fourth letter, usually R, means that the rate response in the device is turned on (R=Rate Modulation on; O or blank = none or no rate modulation).
Category: Implantable Devices