LOOK-ALIKE ECG CHALLENGE
352
Answers
1.
Rhythm strip A: Atrial fibrillation
Rhythm strip B: Multifocal atrial tachycardia (MAT)
To help you decide whether a rhythm is atrial fibrillation or the similar MAT, focus on the presence of P waves as well as the atrial and ventricular rhythms. You may find it helpful to look at a longer (greater than 6 seconds) rhythm strip.
Atrial fibrillation
•Carefully look for discernible P waves before each QRS complex.
•If you can’t clearly identify P waves, fibrillatory (f) waves appear in place of P waves, and the rhythm is irregular, then the rhythm is probably atrial fibrillation.
•Carefully look at the rhythm, focusing on the R-R intervals. Remember that one of the hallmarks of atrial fibrillation is an irregularly irregular rhythm.
MAT
•P waves are present in MAT. Keep in mind, however, that the shape of the P waves will vary, with at least three different P wave shapes visible in a single rhythm strip.
•You should be able to see most, if not all, of the various P wave shapes repeat.
•Although the atrial and ventricular rhythms are irregular, the irregularity generally isn’t as pronounced as in atrial fibrillation.
LOOK-ALIKE ECG CHALLENGE
354
3.
Rhythm strip A: Wandering pacemaker
Rhythm strip B: Premature atrial contraction (PAC) Because PACs are commonly encountered, it’s possible to
mistake wandering pacemaker for PACs unless the rhythm strip is carefully examined. In such cases, you may find it helpful to look at a longer (greater than 6 seconds) rhythm strip.
Wandering pacemaker
•Carefully examine the P waves. You must be able to identify at least three different shapes of P waves (see shaded areas above) in wandering pacemaker.
•Atrial rhythm varies slightly, with an irregular P-P interval. Ventricular rhythm also varies slightly, with an irregular R-R interval. These slight variations in rhythm result from the changing site of impulse formation.
PAC
•The PAC occurs earlier than the sinus P wave, with an abnormal configuration when compared with a sinus P wave (see shaded area above). It’s possible, but rare, to see multifocal PACs, which originate from multiple ectopic pacemaker sites in the atria. In this setting, the P waves have different shapes.
•With the exception of the irregular atrial and ventricular rhythms that result from the PAC, the underlying rhythm is usually regular.
LOOK-ALIKE ECG CHALLENGE
356
5.
Rhythm strip A: Ventricular flutter Rhythm strip B: Torsades de pointes
Torsades de pointes is a variant form of ventricular tachycardia, with a rapid ventricular rate that varies between 250 and 350 beats/minute. It’s characterized by QRS complexes that gradually change back and forth, with the amplitude of each successive complex gradually increasing then decreasing. This results in an overall outline of the rhythm commonly described as spindleshaped.
Ventricular flutter, although rarely recognized, results from the rapid, regular, repetitive beating of the ventricles. It’s produced by a single ventricular focus firing at a rapid rate of 250 to 350 beats/minute. The hallmark of this arrhythmia is its smooth sinewave appearance.
The illustrations shown here highlight key differences in the two arrhythmias.
Ventricular flutter
• Smooth sine-wave appearance
Torsades de pointes
• Spindle-shaped appearance
LOOK-ALIKE ECG CHALLENGE
358
7.
Rhythm strip A: Intermittent ventricular pacing
Rhythm strip B: Premature ventricular contraction (PVC) Knowing whether your patient has an artificial pacemaker
will help you avoid mistaking a ventricular paced beat for a PVC. If your facility uses a monitoring system that eliminates artifact, make sure the monitor is set up correctly for a patient with a pacemaker. Otherwise, the pacemaker spikes may be eliminated as well.
Intermittent ventricular pacing
•The paced ventricular complex will have a pacemaker spike preceding it (see shaded area above). You may need to look in different leads for a bipolar pacemaker spike because it’s small and may be difficult to see.
•The paced ventricular complex of a properly functioning pacemaker won’t occur early or prematurely. It will occur only when the patient’s own ventricular rate falls below the rate set for the pacemaker.
PVC
• PVCs will occur prematurely and won’t have pacemaker spikes preceding them (see shaded areas above).