What is Automatic Response Threshold (ART) on pacemaker interrogation?

What is ART (Automatic Response Threshold) on Pacemaker Interrogation?

ART is an automated pacemaker algorithm that continuously measures pacing thresholds and automatically adjusts pacing output to maintain adequate capture while maximizing battery longevity, eliminating the need for manual threshold testing at each follow-up visit. 1

How ART Works

The algorithm detects the evoked response (ER) signal 70-100 milliseconds after the pacing pulse to verify ventricular capture. 2 This automatic capture verification system:

• Uses a hardware feedback circuit and software template matching to produce a triphasic charge-balanced pacing pulse that eliminates pacing stimulus afterpotential 3
• Defines a "capture window" as the area integral of the first 24 milliseconds of the evoked depolarization 3
• Sets capture threshold as one-third the amplitude of the capture window 3
• Automatically adds a 0.8-V safety margin to the pacemaker output once threshold is determined 3

Clinical Benefits

ART algorithms significantly reduce follow-up time and improve patient safety by preventing exit block through automatic output adjustment. 4, 5

• Reduces device interrogation time from 13.5 minutes (manual) to 9.4 minutes (automatic) 4
• Decreases the number of sensor parameter reprogramming events during visits 4
• Prevents exit block by automatically adjusting output when thresholds increase 5
• Maximizes device longevity by avoiding unnecessarily high pacing outputs 5

Important Clinical Considerations

The evoked response sensitivity must be programmed individually before hospital discharge and reassessed at follow-up visits, as ER signal amplitude can change over time. 6

• ART can be successfully activated in approximately 95% of patients with appropriate leads 6
• ER sensitivity requires adjustment to more sensitive settings in approximately 21% of patients after hospital discharge due to decreasing ER signal amplitude 6
• The system requires high-ohmic ventricular pacing leads for optimal function 2
• If the ER is not sensed, high-voltage backup stimulation prevents loss of capture, ensuring patient safety 6

Long-Term Threshold Behavior

Despite modern steroid-eluting leads, approximately 13% of patients experience permanent threshold increases above 1.5V at 0.4ms, with most increases occurring within the first 12 months. 5

• Threshold increases to 2.6-3.5V occur in 2.2% of patients, representing a potential safety concern 5
• Maximum threshold increase occurs within 12 months in 5.9% of patients 5
• No predictors of threshold increase have been identified at multivariable analysis 5

Accuracy and Reliability

Automatic threshold measurements using ART show excellent agreement with manually determined thresholds, with 70% of unipolar and 67% of bipolar measurements showing no deviation. 2

• When deviations occur, 25-28% differ by only 0.1V 2
• Deviations ≥0.3V occur in only 2-5% of measurements 2
• The algorithm works effectively in both unipolar and bipolar pacing modes 2, 3

Common Pitfalls to Avoid

Do not assume ART eliminates the need for regular device follow-up—ER signal and polarization must be checked at each visit as signal amplitude can decrease, requiring reprogramming. 6

• Failure to monitor ER signal changes can result in inadequate capture detection 6
• Automatic features facilitate but cannot entirely replace comprehensive device interrogation 1
• Device longevity optimization requires attention to programming of output parameters beyond just threshold tracking 1