ECG Challenge: A 54-year-old man with lung cancer who is being treated with chemotherapy presents with progressive fatigue, peripheral edema, and lightheadedness. Although his symptoms were felt to be related to the lung tumor, a chest x-ray film was obtained, and this showed a markedly increased cardiac silhouette. There was no evidence of vascular congestion. The lung tumor in the left upper lobe was observed. An echocardiogram confirmed a significant pericardial effusion with evidence of tamponade. On physical examination, he had significant peripheral edema and neck vein distension. A pulsus paradoxus of 18 mm Hg was noted.
There is a regular rhythm at a rate of 95 bpm. The QRS complex is narrow (0.10 s), and there is a right axis between +90° and +180° (negative QRS complex in lead I and positive QRS complex in lead aVF). There are a number of causes for a right axis including right ventricular hypertrophy (in which there is a tall R wave in lead V1 and often right atrial hypertrophy or a P pulmonale), a lateral wall myocardial infarction (in which there is a deep Q wave in leads I and aVL), Wolff-Parkinson-White (short PR interval and widened QRS complex attributable to a delta wave), right–left arm lead switch (in which there are negative P waves and T waves in leads I and aVL and a positive QRS, P wave, and T wave in lead aVR), dextrocardia (which resembles right–left arm lead switch and also has reverse R wave progression in leads V1–V6), and a left posterior fascicular block (which is a diagnosis of exclusion when no other cause for a right axis is present). Because the ECG does not show any features to suggest a specific cause for the right axis, the diagnosis is a left posterior fascicular block. There is J point and slight ST-segment elevation noted in leads I, II, and V2 to V6 (▼). The T waves have a normal morphology (ie, they are asymmetrical with a slower upstroke and faster downstroke). The ST-segment elevations are the result of a pericarditis. There is poor R-wave progression across the precordium. The QT/QTc intervals are normal (340/430 ms). Noted are beat-to-beat changes in QRS complex amplitude (*, **), termed QRS or electric alternans. There is also T-wave alternans present (+,++). QRS and T-wave alternans are seen with several conditions including a rapid supraventricular tachycardia, an acute ST elevation myocardial infarction, a dilated cardiomyopathy, decompensated heart failure, or a large pericardial effusion or tamponade. Given the clinical presentation and echocardiographic findings, the etiology in this case is the large pericardial effusion and tamponade. There is also low QRS voltage, defined as <5 mm in amplitude in each limb lead and <10 mm in amplitude in each precordial lead.
There are no P waves before any of the QRS complexes. Therefore, this is a junctional rhythm. There are P waves seen after the QRS complexes, most obvious in lead V1 (↓).
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- © 2014 American Heart Association, Inc.