ECG Challenge: Cardiac Abnormalities After Aortic Valve Replacement

The correct diagnosis is sinus tachycardia, left atrial abnormality, and QRS (electrical) alternans, right axis caused by left posterior fascicular block (Figure 2).

Figure 2. Courtesy of Dr Podrid.

Discussion

The rhythm is regular at a rate of 130 beats/min. A P wave occurs before each QRS complex (+) with a stable PR interval (0.14 sec). The P wave is positive in leads I, II, aVF, and V4-V6. This is a sinus tachycardia.

The P waves are negative in leads V1-V2, consistent with a left atrial abnormality or left atrial hypertrophy. The QRS complex has a normal duration (0.08 sec) and morphology. The axis is rightward between +90° and +180° (negative QRS complex in lead I and positive in lead aVF). There are a number of causes of a rightward axis, including:

Right ventricular hypertrophy (associated with a tall R wave in lead V1 and often P pulmonale)
Wolff-Parkinson-White pattern (short PR interval and delta wave)
Lateral wall myocardial infarction (with a deep Q wave in leads I and aVL)
Right-left arm lead switch (with negative P and T waves in leads I and aVL and positive QRS complex, P and T waves in lead aVR)
Dextrocardia (with reverse R-wave progression in leads V1-V6)
Left posterior fascicular block (a diagnosis of exclusion when there is no other cause for the right axis noted)

This is a case of left posterior fascicular block.

Beat-to-beat changes occur in the QRS complex amplitude (*,^), known as QRS or electrical alternans. In addition, there is also P-wave alternans (↓). Causes of electrical alternans (often also associated with T-wave alternans) include a large pericardial effusion or tamponade, any rapid supraventricular tachycardia, an acute ST segment elevation myocardial infarction, a dilated cardiomyopathy, and decompensated heart failure.

Given the woman's history and the presence of sinus tachycardia and P-wave alternans (which is seen only with a pericardial effusion or tamponade), the diagnosis is a large pericardial effusion or tamponade. The QT/QTc intervals are normal (240/350 msec).

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.

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Cite this: ECG Challenge: Cardiac Abnormalities After Aortic Valve Replacement - Medscape - Jan 21, 2020.

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