Welch Allyn Means ECG Physicians Manual for CP Series Electrocardiographs - User Manual - Manual (Page 53)

MEANS Physicians Manual
Welch Allyn
53
3.18 Group 15: Rhythms with constant PR interval
In this group rhythms with constant PR interval are classified that either did not qualify for
analysis in one of the previous groups or have only partly been analyzed there (see Figure 1).
Rhythms that were not yet analyzed comprise regular and irregular rhythms with 0.9 < P/QRS
ratio

1.0 and PR range

30 ms. The rhythms of this group may be classified as
uncomplicated sinus rhythm as far as SA and AV conduction are concerned, provided they
have a normal P wave axis and PR interval.
First, a test for premature supraventricular complexes is performed as these complexes may
still be present if the rate variation is large. Second, if the rhythm is regular with a PR interval
variation between 30 and 60 ms while the number of P waves found is less than the number
of QRS complexes, a pacemaker shift should be considered. (If the PR range exceeds 60 ms,
the rhythm has been taken care of in group 5.) Third, if the program detects a negative P axis
with a sufficiently negative P-wave amplitude in aVF, an ectopic atrial rhythm or an AV
junctional rhythm is considered present, depending on the length of the PR interval and the
program halts. If not, various types of sinus rhythm can be classified, with or without
arrhythmia dependent on the rate variation. Finally, the presence of first degree AV block,
corrected for heart rate, is tested at different levels of severity. The PR interval limits used by
the program are shown in Table 4.
Say: “premature supraventricular complexes”
if: test PSVC passed
Say:
“PR interval variation: pacemaker shift?”
if: 30 < PR range

60 ms
and P/QRS < 1.0
Say:
“AV junctional rhythm”
if: P axis   30 
and negative P amplitude in aVF > 70 µV
and PR interval

80 ms
Say:
“ectopic atrial rhythm”
if: P axis
 
30

and negative P amplitude in aVF > 70 µV
and PR interval > 80 ms
Say:
“sinus bradycardia with sinus arrhythmia”
if: heart rate < 50 BPM
and rate variation > 20%
Say:
“sinus arrhythmia”
if: 50

heart rate < 100 BPM
and rate variation > 20%
Say:
“sinus tachycardia with sinus arrhythmia”
if: heart rate

100 BPM
and rate variation > 20%
Say:
“extreme bradycardia, consider sinus rhythm with 2:1 AV conduction”
if: heart rate < 40 BPM
and rate variation

20%