A physician-validated, board-style question from the Active Transport QBank. Try it, then check the reasoning for every option.
A 49-year-old man comes to the physician because of a 2-week history of increasing shortness of breath. He has also had chest pain that is exacerbated by deep inspiration. He has had recurrent episodes of pain in his fingers for the past 2 years. Two years ago, he was treated for a deep vein thrombosis. He has hypertension and anxiety. Current medications include enalapril, St John's wort, and ibuprofen. His temperature is 37°C (98.6°F), pulse is 110/min, respirations are 17/min, and blood pressure is 110/70 mm Hg. Examination shows pale conjunctiva. There is tenderness to palpation of the proximal interphalangeal and metacarpophalangeal joints of both hands. Heart sounds are distant. The lungs are clear to auscultation. Laboratory studies show:
Hemoglobin 11.9 g/dL
Leukocyte count 4200/mm3
Platelet count 330,000/mm3
Serum
Na+ 136 mEq/L
K+ 4.3 mEq/L
Antinuclear antibodies 1: 320
Anti-SM-1 antibodies positive
Anti-CCP antibodies negative
An x-ray of the chest is shown. Which of the following is most likely to be seen on this patient's ECG?"
-
A
Increased QT intervalIncorrect. Increased QT interval reflects ion-channel/drug effects, electrolyte disturbances, or congenital LQTS — not pericardial effusion.
-
B
Deep Q waveIncorrect. Deep Q waves indicate prior transmural myocardial infarction, not pericardial disease.
-
C
Electric alternansCorrect. Electrical alternans — beat-to-beat amplitude variation — is classic for large pericardial effusion or tamponade as the heart swings within the fluid.
-
D
S1Q3T3 patternIncorrect. S1Q3T3 is a non-sensitive ECG sign of pulmonary embolism with right-heart strain; this patient's findings point to tamponade, not PE.
-
E
Delta wave with shortened PR intervalIncorrect. A delta wave with shortened PR interval signifies Wolff-Parkinson-White syndrome from an accessory pathway — unrelated to pericardial tamponade.
↑ Tap an answer to reveal the reasoning
Answer: C. A young man with positive ANA at high titer plus anti-Smith antibodies, Raynaud's-type finger pain, prior DVT, symmetric joint tenderness, and pleuritic chest pain has systemic lupus erythematosus. Anti-Sm is highly specific for SLE. His pleuritic chest pain plus distant heart sounds and pleural/pericardial involvement point to lupus pericarditis with effusion — likely tamponade.
The ECG hallmark of a large pericardial effusion / tamponade is electrical alternans: beat-to-beat alternation in the amplitude (and sometimes axis) of the QRS complex caused by the heart swinging within fluid-filled pericardium. Other ECG features include low-voltage QRS and diffuse PR depression with ST elevation if there is associated pericarditis.
The prior DVT also fits the lupus picture because of antiphospholipid antibodies (a common SLE association). The other ECG findings listed describe other entities: long QT (electrolytes/drugs/congenital), deep Q waves (prior infarction), S1Q3T3 (classic but insensitive PE pattern).
**Why each option:**
**A.** Increased QT interval reflects ion-channel/drug effects, electrolyte disturbances, or congenital LQTS — not pericardial effusion.
**B.** Deep Q waves indicate prior transmural myocardial infarction, not pericardial disease.
**C.** Electrical alternans — beat-to-beat amplitude variation — is classic for large pericardial effusion or tamponade as the heart swings within the fluid.
**D.** S1Q3T3 is a non-sensitive ECG sign of pulmonary embolism with right-heart strain; this patient's findings point to tamponade, not PE.