How do I know if my CRT-D is working?
Your device clinic monitors CRT-D function at regular check-ups, just as with a standard ICD. They use a programmer to review pacing data, check battery levels, assess how much of the time the device is delivering biventricular pacing (the percentage pacing figure), and adjust settings if needed. Remote monitoring between appointments allows the clinic to track this data without a visit.
From your perspective, CRT often produces noticeable improvements over weeks and months after implant: reduced breathlessness, better exercise tolerance, and less fatigue. These changes can be gradual rather than immediate. Response to CRT is not universal — roughly one in three patients does not experience the expected benefit, sometimes because the lead positioning is not optimal or because of underlying heart anatomy. If this appears to be the case, your clinic may adjust settings or consider lead repositioning.
If your symptoms worsen after a CRT-D implant rather than improving, or if you receive a shock, contact your device clinic or attend A&E. As with any ICD, any shock should always be reviewed.
Category: Implantable DevicesWhy might I be offered a CRT-D rather than a standard ICD?
A CRT-D is recommended when someone needs both ICD protection and cardiac resynchronisation therapy. This typically applies to people with heart failure where:
- The left ventricle’s pumping function is significantly reduced (usually an ejection fraction of 35% or below)
- The ECG shows a wide QRS complex, indicating that the two ventricles are not contracting in synchrony
- Symptoms persist despite optimal medical therapy
In this group of patients, biventricular pacing can improve symptoms, exercise capacity, and quality of life, and in some cases can partially reverse the structural changes in the heart. Clinical evidence shows that approximately two in three eligible patients experience meaningful benefit from CRT.
Not everyone who has had a cardiac arrest has heart failure, and not everyone with heart failure needs a CRT-D. A standard ICD may be perfectly appropriate. The decision is made by a specialist cardiologist or electrophysiologist based on your ECG, echocardiogram results, symptoms, and other clinical factors. If a CRT-D has been recommended for you, your team will explain the specific reasons.
Category: TreatmentWhat 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: Implantable Devices