ECG Challenge: A 56-year-old woman with a history of pulmonary fibrosis and pulmonary artery hypertension who was receiving diuretic therapy for peripheral edema presents to the emergency department with complaints of palpitations associated with worsened shortness of breath and more significant peripheral edema. Her vital signs are stable, but her pulse is rapid. Her neck veins are markedly distended, and there is 3+ pitting edema of the knees. An ECG is obtained (ECG A). She is admitted to the hospital and placed on telemetry. She is treated with intravenous diuretics. While on telemetry, her heart rate is noted to slow intermittently, and an ECG is repeated (ECG B).
ECG A shows a regular rhythm at a rate of 120 bpm. The QRS complex has a normal duration (0.08 second) and a normal morphology. The axis is normal between 0° and +90° (positive QRS complex in leads I and aVF). The QT/QTc intervals are normal (320/450 milliseconds). A P wave is seen before each QRS complex (^), but it is negative in leads II, aVF, and V1 through V6. There is a long RP interval (0.30 second; ┌┐) and a short PR interval (0.20 second; └┘). This is called a long-RP tachycardia, and causes for it include the following:
Sinus tachycardia, which is not the cause in this case because the P wave is negative in most of the leads;
Ectopic junctional tachycardia with a retrograde P wave
Atrial flutter with 2:1 atrioventricular block, which is not the cause here because a second flutter wave (which should be obvious) is not seen;
Atrioventricular re-entrant tachycardia; or
Atypical atrioventricular nodal reentrant tachycardia, which is known as fast-slow, ie, conduction to the ventricles via the fast pathway and retrograde conduction to the atria via the slow pathway.
ECG B shows a rhythm that is irregular as a result of 1 premature complex (*) and a short run of long-RP tachycardia with a negative P wave (^) that is the same as that seen in ECG A. All of the QRS complexes have the same duration, morphology, axis, and QT/QTc intervals as seen in ECG B. The first, third, and fourth QRS complexes are preceded by a P wave (+) with a constant PR interval (0.20 second). The last 2 QRS complexes are also preceded by a P wave (v) that has the same morphology and the same PR interval as complexes 1, 3, and 4. The P wave is positive in leads I, II, aVF, and V4 through V6. Hence, these are all sinus complexes. The second QRS complex (*) is wide, has a different morphology, and is not preceded by a P wave. This is a premature ventricular complex. The brief run of the long-RP tachycardia (10 beats) terminates spontaneously. It can be seen that it terminates without a P wave after the last QRS complex (↓). Arrhythmias that terminate with the absence of atrial activity after the last QRS complex originate from the atrium because the arrhythmia terminates when the atrial focus fails to generate an impulse (and hence no P wave). The arrhythmia seen in ECG A is therefore an atrial tachycardia.
Please go to the journal’s blog, OpenHeart, for more ECG Challenges: http://goo.gl/tQPNFp. Challenges are posted on Tuesdays and Responses on Wednesdays.
- © 2015 American Heart Association, Inc.