9650-1210-01 Rev. R A-27
ECG Analysis Algorithm Accuracy
Sensitivity and specificity are expressions of ECG
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 non-shockable rhythms (as a
percentage of the total number of non-shockable
rhythms). The data in the following table summarizes the
accuracy of the ECG analysis algorithm as tested
against ZOLL’s ECG Rhythm Database.
The algorithm sequence takes approximately 9 seconds
and proceeds as follows:
• Divides the ECG rhythm into three-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 (‘auto-
correlation’) of peaks and troughs.
• Determines if multiple 3 second segments are
shockable then displays SHOCK ADVISED
message.
Clinical Performance Results
The performance of the incorporated analysis algorithm
in a single analysis sequence satisfies the applicable
requirements specified in ANSI/AAMI DF80 (section
6.8.3) and the recommendations by Kerber et al.
(Circulation. 1997;95(6):1677).
Table A-3. Clinical Performance Results
References:
Young KD, Lewis RJ: “What is confidence? Part 2:
Detailed definition and determination of confidence
intervals”. Annals of Emergency Medicine, September
1997; 30; 311-218
William H. Beyer, Ph.D.: “CRC Standard Mathematical
Tables 28
th
Edition,” CRC Press, Inc, Boca Raton, FL.,
1981, Percentage Points, F-Distribution Table, pg 573.
Rhythms Sample
Size
Performance Goals Observed
Performance
90% One-sided
Lower Confidence
Limit
Shockable Sensitivity
Coarse VF
Rapid VT
536
80
>90%
>75%
>95%
>98%
>97%
>96%
Non-shockable Specificity
NSR
AF, SB, SVT, Heart block,
idioventricular, PVCs
Asystole
2210
819
115
>99%
>95%
>95%
>99%
>99%
>98%
>99%
>99%
>97%
Intermediate
Fine VF
Other VT
69
28
Report only
Report only
Sensitivity
>88%
>96%
>80%
>84%
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