In an ICD, what type of counter is used for VT detection?

In an ICD, what type of counter is used for VT detection?

• A. Up counter
• B. Down counter
• C. Up/down counter
• D. None of the above

Answer: (C)

Ventricular tachycardia detection in an ICD relies on recognizing that fast heart activity must be sustained, not just a brief spike. An up/down counter provides this persistence and hysteresis. When the sensed beats meet the VT rate criterion, the up-counter increments toward a detection threshold. If the rhythm later slows back toward normal, the down-side of the counter decreases, allowing the device to decay the detection toward non-tachycardia. Only when the combined up/down counter reaches the programmed threshold is VT declared and therapy considered. This approach prevents brief, non-sustained fast rates from triggering therapy and helps avoid missed detections by ensuring the rhythm remains fast long enough to warrant intervention.

Ventricular tachycardia detection in an ICD relies on recognizing that fast heart activity must be sustained, not just a brief spike. An up/down counter provides this persistence and hysteresis. When the sensed beats meet the VT rate criterion, the up-counter increments toward a detection threshold. If the rhythm later slows back toward normal, the down-side of the counter decreases, allowing the device to decay the detection toward non-tachycardia. Only when the combined up/down counter reaches the programmed threshold is VT declared and therapy considered. This approach prevents brief, non-sustained fast rates from triggering therapy and helps avoid missed detections by ensuring the rhythm remains fast long enough to warrant intervention.