Welch Allyn Cardioperfect Workstation, PEDMEANS ECG Interpretation Module - Physicians - User Manual - Manual (Page 25)

CardioPerfect Workstation
PEDMEANS ECG Interpretation Module Physicians Manual
DIR 80015051 Rev. C 25 / 55
3 Rhythm analysis
3.1 Introduction
In this section of the program a wide range of diagnoses is offered. There are six basic processing
steps:
1 The first aim of the computer program is to detect artificial pacemaker spikes. If these are found
the program will issue an appropriate statement and stop. Contour analysis is performed if there
are enough unpaced complexes.
2 If no artificial pacemaker spikes are detected the program will try to find QRS complexes which do
not conform to the dominant complexes in the ECG. These non-dominant complexes are
analyzed, classified and discarded so that further rhythm analysis can be performed on sequences
of complexes of the dominant type.
3 After this procedure, with only one type of QRS complexes left to analyze, the program will look for
flutter waves. Finding no flutter waves does not automatically mean that the diagnosis of atrial
flutter cannot be made. This precaution has been built in because it is not always possible for the
computer to detect flutter waves.
4 For the actual rhythm analysis a division is made between regular and irregular rhythms. A rhythm
is judged to be regular if the difference between the maximum and minimum RR interval is less
than 20% of the average RR interval. If there are RR intervals falling outside this range the rhythm
is categorized as irregular.
5 Subsequently, the program checks which relation exists between the dominant QRS complexes
and P waves. There are several possibilities:

There are no P waves found. The analyzed ECG falls into this category if less than 15% of the
QRS complexes is preceded by a P wave. This criterion has been built in to make allowance
for the program detecting P waves by mistake.

Some QRS complexes are preceded by a P wave, others are not. This category will be
chosen if 15-90% of the QRS complexes are preceded by a P wave.

Each QRS complex is preceded by one and only one P wave. This category will be chosen if
90-100% of the QRS complexes is preceded by a P wave. This criterion was so formulated
because it is possible that the program will incidentally miss a P wave.

Some or all QRS complexes are preceded by more than one P wave. This implies that the
number of P waves is larger than that of the QRS complexes.
6 A final distinction between the diagnostic groups is the constancy of the PR intervals. With
difference between the largest PR interval and the shortest PR interval of less than 30 ms the
interval is said to be constant.
Basic parameters such as constancy of the RR interval, P/QRS ratio, and constancy of the PR interval
are not the only characteristics on which a diagnosis is based. Other features are used to form a
statement, such as heart rate, type of the non-dominant complexes, QRS duration and PP interval.
Through combinations it is possible to form over a hundred and fifty statements concerning the type of
rhythm.
Subsequent paragraphs in this chapter will describe the parameters that are used in rhythm analysis,
the general structure of the decision tree and the categories of rhythm statements that have been
distinguished, and the diagnostic criteria for the rhythm statements grouped according to category. A
cross-reference list is provided for ease of finding the criteria for a specific statement.