Normal Sinus Rhythm With Junctional Escape

Normal Sinus Rhythm With Junctional Escape Beats: ECG Findin
Published on Cancer Network (http://www.cancernetwork.com)
Normal Sinus Rhythm With Junctional Escape Beats: ECG
Findings
September 01, 2007
By Richard A. Harrigan, MD [1], Richard A. Harrigan, MD [1], William J. Brady, MD [2], and Theodore
Chan, MD [3]
A 68-year-old woman with hypertension complains of intermittent dyspnea and light-headedness.
She is asymptomatic during the evaluation. Vital signs are normal, but an irregularly irregular pulse
is noted on examination as well as on the telemetry monitor. The 12-lead ECG is shown here; the
ECG machine printout reads "atrial fibrillation." The patient has no history of this arrhythmia.
Figure 1
Figure 2
Figure 3
A 68-year-old woman with hypertension complains of intermittent dyspnea and light-headedness.
She is asymptomatic during the evaluation. Vital signs are normal, but an irregularly irregular pulse
is noted on examination as well as on the telemetry monitor. The 12-lead ECG is shown here; the
ECG machine printout reads "atrial fibrillation." The patient has no history of this arrhythmia.
Do you agree with the computer-generated diagnosis? Which of the following do you
think best explains the ECG findings?
Atrial fibrillation.
Normal sinus rhythm with premature junctional contractions.
Normal sinus rhythm with junctional escape beats.
Second-degree atrioventricular block, Mobitz type I.
Normal sinus rhythm with premature atrial contractions.
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Normal Sinus Rhythm With Junctional Escape Beats: ECG Findin
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(Answer and Discussion on next page.)
Figure 1
Figure 2
Figure 3
Answer: Normal sinus rhythm with junctional escape beatsWhat The ECG Shows
The ECG shows an irregularly irregular rhythm that is slightly bradycardic but nearly normal in rate
(Figure 1). There appear to be P waves preceding some, but not all, beats (all except 5 and 8).
Beats 5 and 8 have P-like deflections immediately preceding the QRS complexes, but these are too
close to the QRS complexes to conduct. INITIAL STEPS IN RHYTHM ANALYSIS
The first step in deciphering a tricky narrow-QRS-complex rhythm is to ask for a 12-lead ECG, if
patient stability allows, since atrial activity may be obscure in certain leads. Imagine trying to
determine in this patient whether P waves were present if you were given only a single-lead rhythm
strip from lead III or lead V1!
If the rhythm diagnosis remains obscure after reviewing the 12-lead tracing, it is best to generate a
rhythm strip using the 12-lead ECG machine, incorporating the leads that best demonstrate atrial
activity in that patient. Here, these would include leads II and V5.
It is also often helpful to obtain a previous ECG for comparison. This strategy is frequently used to
evaluate T-wave patterns in patients with possible cardiac ischemia, but it is underutilized in settings
such as this. A previous ECG will demonstrate what the patient's P waves normally look like and thus
help determine whether minor, difficult-to-classify "atrial" deflections are indeed artifact or coarse
atrial fibrillation rather than P waves.
Lastly, the ECG machine may be manipulated to increase the size of all the complexes, thus making
minute P waves larger. This is referred to as increasing the "standardization," or calibration, of the
tracing to "double standard" (ie, 20 mm/mV, rather than the default of 10 mm/mV). Increasing the
calibration to double standard results in the doubling in size of all cardiac waveforms, as well as of
the plateau-shaped waveform at the extreme left of each row of waveforms on the tracing. Normal
standardization is reflected by a plateau-shaped waveform that is 2 large boxes in amplitude (or 20
small squares, as in these tracings); "double standard" shows a waveform 4 large boxes (or 40 small
squares) in amplitude. DECIPHERING THE IRREGULAR RHYTHM
"Regularly irregular" versus "irregularly irregular." An irregular, narrow-QRS-complex rhythm
evokes a wide differential diagnosis (Table).1 To narrow the differential, first determine whether the
rhythm is irregularly irregular or regularly irregular. The rhythm in this tracing (shown in Figure 1
with the ventricular beats/ QRS complexes numbered on the lead II rhythm strip at the bottom)
appears to be irregularly irregular. If it were regularly irregular, several ECG diagnoses would move
up in the differential diagnosis: namely, normal sinus rhythm (NSR) with a regular bigeminal,
trigeminal, or quadrigeminal pattern, and second-degree atrioventricular (AV) block in a fixed
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Normal Sinus Rhythm With Junctional Escape Beats: ECG Findin
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pattern (eg, 2-to-1 [meaning 2 atrial beats for every ventricular beat], 3-to-1, and so forth). Because
the tracing shows an irregular pattern of irregularity, all entities in the differential diagnosis are still
viable.
Table — D
narrow-Q
Atrial fibr
Atrial flut
variable b
NSR with
prematur
(atrial, ju
or ventric
be in bige
trigemina
quadrige
pattern
NSR with
pause or
arrest (m
accompa
escape b
Second-d
atriovent
block
Second-d
sinoatrial
Sinus arr
Wanderin
pacemak
NSR, norm
Data from
ECG in Em
Care. 2001
References: REFERENCE:
1. Harrigan RA. Dysrhythmias at normal rates. In: Chan TC, Brady WJ, Harrigan RA, et al. ECG in
Emergency Medicine and Acute Care. Philadelphia; Elsevier Mosby; 2005:31-35.
Source URL:
http://www.cancernetwork.com/normal-sinus-rhythm-junctional-escape-beats-ecg-findings
Links:
[1] http://www.cancernetwork.com/authors/richard-harrigan-md
[2] http://www.cancernetwork.com/authors/william-j-brady-md
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[3] http://www.cancernetwork.com/authors/theodore-chan-md
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