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.