ECG Challenge: Cardiomyopathy and an Irregular Rhythm

Medscape

3 hours ago

A 67-year-old man with a history of dilated cardiomyopathy and a left ventricular ejection fraction of 40% presents to his primary care provider for a routine physical examination. His vital signs and blood pressure are normal, but he has an irregular pulse.
Figure 1. Courtesy of Philip J. Podrid, MD.
The correct diagnosis is sinus rhythm, PVCs, and echo beats (Figure 2).
Figure 2. Courtesy of Philip J. Podrid, MD.
Discussion
The rhythm is irregular with a repeating grouped beating pattern, with three QRS complexes and a pause. Therefore, the rhythm is regularly irregular. The average rate is 42 beats/min.
The first of three QRS complexes has a normal duration (0.08 sec) and morphology. The axis is physiologically leftward between 0° and -30° (positive QRS complex in leads I and II and negative in lead aVF). This QRS complex is preceded by a P wave (+), which is positive in leads I, II, aVF, and V4-V6. The PR interval is constant (0.16 sec). Therefore, this is a sinus complex. The QT/QTc intervals are normal (420/350 msec).
The second QRS complex (^) is wide (0.14 sec), and it has an unusual morphology not typical for either a left or right bundle branch block. There is positive concordance from V1-V5, although there is an S wave in V6. This QRS complex is not preceded by a P wave. Therefore, this is a PVC.
The third QRS complex is identical to the first and is therefore supraventricular. This QRS complex is preceded by a P wave (*) that is negative in leads II and aVF, and positive in aVR. Therefore, this is not a sinus P wave. Because it is negative in lead aVF, it originates from either the atrioventricular (AV) node (ie, retrograde) or the low part of the atrium. There is a fixed relationship between the PVC and the negative P wave, so it is likely a retrograde P wave resulting from ventriculoatrial (VA) conduction from the PVC. The supraventricular complex that follows the PVC is therefore termed an echo complex.
An echo complex occurs with a preceding QRS complex that is not preceded by a P wave (junctional, ventricular, or paced complex) and is associated with intact VA conduction. Intact VA conduction may lead to retrograde activation of the atrium (retrograde P wave). Given the right timing, this retrograde atrial impulse can then enter the AV node and His-Purkinje system to restimulate the ventricles in an antegrade direction (ie, it echoes back to the ventricles).
Philip Podrid, MD, is an electrophysiologist, a professor of medicine and pharmacology at Boston University School of Medicine, and a lecturer in medicine at Harvard Medical School. Although retired from clinical practice, he continues to teach clinical cardiology and especially ECGs to medical students, house staff, and cardiology fellows at many major teaching hospitals in Massachusetts. In his limited free time, he enjoys photography, music, and reading.