The ECG signal quality metrics are a combination of statistical measures, in both the time and frequency domains, multi-channel QRS detector performance, and correlation to past data. A more in-depth description of the formation of these annotations, together with an evaluation of a robust HR and ABP tracking algorithm that utilizes this information can be found in (9) and (10). The blood pressure signal quality metric is based upon two earlier developed metrics by Zong (7) and Sun (8).
There are several annotations associated with each beat in the ECG and ABP signals. Table 2.8 describes the available SQI annotations for waveform records. Full descriptions of how to interpret the SQI output for ECG and ABP can be found in in (9) and (10) respectively. Note that although many of the artifact types for each of these signals have been incorporated, and known errors in heart rate and blood pressure calibrated to the SQI output, some artifacts are not well represented. In particular, the tricky problem of blood pressure damping is not yet fully solved in our ABP SQI metric. Any analysis of blood pressure should therefore be tempered by the fact that damping may lead to an error, and in particular, an under-estimation of the SBP and pulse pressure.
Annotation | Description
|
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file.ecgsqid | A combined beat-by-beat ECG SQI created by selecting the best ECG SQI between different ECG leads. |
file.ecgsqidn | The ECGSQI annotation of the () ECG lead, used to create a combined annotation file'.multid' |
file.epltdn | The EPLTD (DF) annotation of the () ECG lead, used to create EPSQI and ICHSQI |
file.epsqin | The EPSQI (bSQI) annotation of the () ECG lead, used to create Kurtosis (kSQI) and SDR (sSQI) |
file.ichsqin | The ICHSQI (iSQI) annotation of the () ECG lead, used to create ECGSQI |
file.kurtdn | The Kurtosis (kSQI) and SDR (sSQI) annotation of the () ECG lead, used to create ECGSQI and the sample-and-hold HR (HRsh1) of the first ECG lead |
file.multid | An all-in-one annotation include all leads of ECG beats with ECGSQI and ABP beat with ABPSQI, used to create the HR and ABP |
fileTd | A WFDB trend data file that includes different calculations of HR, HRSQI and ABP sampled at 0.1Hz |
fileTd.hea | A header file of fileTd |
file.wqrsn | The WQRS (LT) annotation of the () ECG lead, used to create EPSQI (bSQI) |
fileT | A WFDB trend data file similar to fileTd, but without baseline wander filter to calculate kurtosis. |
fileT.hea | Header file for fileT |
file.wsqi | The WSQI annotation of the ABP lead, used to create ABPSQI |
file.jsqi | The JSQI annotation of the ABP lead, used to create ABPSQI |
file.abpsqi | The ABPSQI annotation of the ABP lead, used to create '.multid' |