ECG Rhythm Analysis Algorithm Accuracy
9650-0912-01 Rev. N ZOLL R Series Operator’s Guide A–29
ECG Rhythm Analysis Algorithm Accuracy
Sensitivity and specificity are expressions of ECG rhythm analysis algorithm performance
when compared to ECG interpretation by a clinician or expert. Sensitivity refers to the
algorithm’s ability to correctly identify shockable rhythms (as a percentage of the total number
of shockable rhythms). Specificity refers to the algorithm’s ability to correctly identify
nonshockable rhythms (as a percentage of the total number of nonshockable rhythms).
The data in Table A-4 and Table A-5 summarize the accuracy of the ECG rhythm analysis
algorithm as tested against ZOLL’s ECG rhythm database. Rhythm sources included data
records from ZOLL devices and public domain databases recorded with electrode systems and
ECG signal processing characteristics similar to the R Series. Data records were of appropriate
length to allow for satisfactory analysis.
The algorithm sequence takes approximately 9 seconds and proceeds as follows:
• Divides the ECG rhythm into 3-second segments
• Filters and measures noise, artifact, and baseline wander
• Measures baseline content (“waviness” at the correct frequencies – frequency domain
analysis) of signal
• Measures QRS rate, width, and variability
• Measures amplitude and temporal regularity (autocorrelation) of peaks and troughs
• Determines if multiple 3-second segments are shockable and then prompts the operator to
treat the patient
Table A-4. Clinical Performance Results (Adult Patients)
Rhythms
Sample
Size
Performance
Goals
Observed
Performance
90% One-sided Lower
Confidence Limit
Shockable Sensitivity
Coarse VF 536 >90% 100.0% 99.4%
Rapid VT 80 >75% 100.0% 96.3%
Nonshockable Specificity
NSR 2210 >99% 100.0% 99.9%
AF, SB, SVT, heart block,
idioventricular, PVCs
819 >95% 99.9% 99.4%
Asystole 115 >95% 100.0% 97.4%
Intermediate
Fine VF 69 Report only 89.9% 81.8%
Other VT 28 Report only 96.4% 84.2%
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