Welch Allyn Means ECG Physicians Manual for CP Series Electrocardiographs - User Manual - Manual (Page 37)

MEANS Physicians Manual
Welch Allyn
37
3.4 Group 1: Rhythms with artificial pacemaker spikes
Artificial pacemaker spikes may have been detected by the measurement part of the program.
If so, a general statement will be issued and the program halts. No attempt is made to specify
the type of pacemaker, frequency, or functioning of the demand mechanism.
Say: “artificial pacemaker rhythm”
if: artificial pacemaker spikes have been found
3.5 Group 2: Non-dominant QRS complexes
Non-dominant QRS complexes can be classified in different categories. First, a test is
performed on the occurrence of short paroxysms of at least three complexes (“runs”). To
qualify as a run, its rate should exceed the inherent rate of the subsidiary pacemaker by 20%
and the number of complexes belonging to the run should be less than 90% of the total
number of QRS complexes. The identified non-dominant complexes are discarded and the
program continues with the classification of the non-dominant complexes that are still present
in the recording.
Second, consecutive non-dominant complexes without an acceleration of the QRS rate are
searched for. Depending on the number of complexes found, the term “doublet” (two
consecutive complexes) or “sequence” (three or more complexes) is used. One of the
parameters considered here is the length of the RR interval preceding the first non-dominant
complex of the doublet or sequence (the coupling interval) relative to the RR interval of the
basic rhythm (RR ratio). This parameter is used to distinguish between premature beats and
an escape rhythm. Again, complexes are discarded after their classification.
Following this, a test is performed for the presence of a bigeminy, i.e., for the alternation of
the dominant QRS type with another (or others), whether continuously or only during part of
the recording. If an alternation of QRS types is present during the entire recording, a special
test is made for the presence of a ventricular escape-capture bigeminy.
Finally, the type of the remaining single non-dominant complexes is classified according to
the QRS width and the duration of preceding RR interval. Coupling intervals (the interval
between the ectopic complex and the preceding dominant QRS complex) are considered
constant if the range of these intervals does not exceed 80 ms.
The classification of non-dominant complexes may need adjustment in the presence of some
rhythms that are classified at a later stage of the rhythm analysis. The alterations are
explained in the last paragraph of this section.