PAC Sweep Speed on ECG
The standard sweep speed for recording PACs (Premature Atrial Contractions) on an electrocardiogram is 25 mm/sec, which is the universal default for routine ECG recordings. 1
Standard ECG Recording Parameters
- The American Heart Association recommends a standard sweep speed of 25 mm/sec for all routine ECG recordings, including those capturing premature atrial contractions 1
- At this speed, each small box (1 mm) represents 0.04 seconds (40 milliseconds), and each large box (5 mm) represents 0.20 seconds (200 milliseconds) 1
- This standard sweep speed allows adequate temporal resolution to identify PAC morphology, measure coupling intervals, and assess P-wave characteristics 1
When to Use Faster Sweep Speeds
For detailed time interval measurements involving PACs, increase the sweep speed to 100 mm/sec to improve temporal resolution and measurement accuracy 1
- The American Society of Echocardiography and European Association of Cardiovascular Imaging specifically recommend 100 mm/sec sweep speed when measuring precise time intervals on Doppler recordings 1
- This faster speed is particularly useful when calculating coupling intervals of PACs, which are critical for determining arrhythmogenic potential 2
- PACs triggering atrial fibrillation typically have shorter coupling intervals (362.8 ± 23.0 ms) compared to non-triggering PACs from pulmonary veins (470.6 ± 60.1 ms) or non-PV areas (515.6 ± 77.2 ms), and these measurements require precise temporal resolution 2
Clinical Context for PAC Assessment
- When evaluating frequent PACs (>21,000 per 24 hours or burden >28%), standard 25 mm/sec sweep speed is adequate for initial rhythm assessment 3
- The prematurity index of PACs averages 45 ± 12%, meaning they occur approximately halfway through the expected cardiac cycle, which is easily visualized at standard sweep speed 4
- For mapping PAC origin during electrophysiology studies, activation time at successful ablation sites typically precedes P-wave onset by 36 ± 7.6 ms, requiring high-resolution recording systems beyond standard surface ECG 3
Common Pitfalls to Avoid
- Never assume computer-generated measurements are accurate without manual verification, particularly when assessing PAC coupling intervals or burden 5
- Ensure proper electrode placement, as precordial lead misplacement occurs in more than one-third of routine recordings and can affect PAC detection 5
- Document if non-standard sweep speeds are used, as this affects all time-based measurements and diagnostic interpretation 6