Welch Allyn Cardioperfect Workstation, PEDMEANS ECG Interpretation Module - Physicians - User Manual - Manual (Page 26)

CardioPerfect Workstation
PEDMEANS ECG Interpretation Module Physicians Manual
DIR 80015051 Rev. C 26 / 55
3.2 Rhythm parameters
The following parameters are used in the diagnostic criteria of the rhythm section:

P/QRS ratio: ratio of the number of P waves to the number of dominant QRS complexes. Used as
a measure for atrial activity.

PR range: difference between the maximum and minimum PR interval (in ms). Used as a
measure for the constancy of the PR interval.

Type of QRS complex: classification of QRS complexes according to their morphology.
Complexes with the same morphology belong to one type. A basic distinction is between the
dominant type of QRS complex and non-dominant types. The latter group may consist of one or
more types of non-dominant QRS complexes.

RR interval: interval between two consecutive QRS complexes (in ms).

PP interval: interval between two consecutive P waves (in ms).

PR interval: interval between a dominant QRS complex and a preceding P wave (in ms)

atrial rate: number of atrial contractions (in beats per minute, BPM).

V rate: number of ventricular contractions (in BPM)

rate variation: difference between the maximum and minimum RR interval, normalized to the
average RR interval. Used as a measure for regularity of the rhythm.

QRS duration: difference between the overall onset and end of the QRS complex (in ms).

P axis: axis of the P wave in the frontal plane, using the areas under the P waves in lead I and II
(in degrees).

negative P amplitude (in µV): absolute value of the negative deflection of the P wave.
3.3 Decision tree
The decision tree for the rhythm analysis is shown in Figure 1 on page 28. The program starts at the
top decision node and proceeds depending on the value of the test. If the condition in the decision
node is met the branch marked by “yes” is taken, if not, the “no”-branch is followed. First, the activity of
an artificial pacemaker, the occurrence of more than one type of QRS complexes (non-dominant
complexes), and the presence of atrial flutter waves is tested. In case of pacemaker spikes or flutter
waves an appropriate statement is issued and the rhythm analysis stops. In case non-dominant
complexes are also present, the type of arrhythmia is described. The non-dominant complexes are
then discarded from further consideration and the analysis proceeds. Thus, after this first phase only
one type of QRS complex (dominant complexes) is analyzed.
Second, regular rhythms are distinguished from irregular ones based on the constancy of the RR
interval. Both types of rhythm are subdivided in different groups depending on the number of P waves
as compared to the number of QRS complexes (P/QRS ratio) and on the constancy of the PR interval
(PR range). It may happen that the irregularity of a rhythm is local. The program then describes the
abnormality and discards the relevant complexes, similar to the way non-dominant complexes are
handled. If the resultant rhythm, after removal of complexes, is regular the rhythm is taken care of in
the regular rhythm part of the program.
In Table 3 the various groups are listed together with a characterization of the types of arrhythmia in
each group.