Arrhythmias & Conduction · Pathology · NBME-Style
Arrhythmias & Conduction — NBME-style practice question
A physician-validated, board-style question from the Active Transport QBank. Try it, then check the reasoning for every option.
A 55-year-old man with no significant medical history presents with new-onset fatigue. His vital signs include a pulse of 72/min and blood pressure of 140/90 mmHg. An ECG reveals a wide QRS complex with a 'W' pattern in lead V1. What is the most likely consequence if this condition is left untreated?
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A
Atrial flutterIncorrect. Atrial flutter is a reentrant atrial rhythm, not a downstream consequence of LBBB-induced ventricular dyssynchrony.
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B
Atrial fibrillationIncorrect. Atrial fibrillation arises from atrial remodeling/triggers, not directly from isolated LBBB conduction delay.
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C
Third-degree AV blockIncorrect. Third-degree AV block requires additional AV nodal/His disease beyond an isolated bundle branch block.
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D
Pulmonary embolismIncorrect. Pulmonary embolism is a thromboembolic event unrelated to chronic LBBB pathophysiology.
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E
Heart failureCorrect. LBBB causes ventricular dyssynchrony that progressively reduces ejection fraction and produces heart failure.
↑ Tap an answer to reveal the reasoning
Answer: E. (1) The vignette describes ECG findings consistent with a left bundle branch block (LBBB). (2) If untreated, LBBB can lead to dyssynchronous ventricular contraction and eventually heart failure due to reduced ejection fraction. (3) Third-degree AV block and atrial flutter would require additional conduction issues, while atrial fibrillation and pulmonary embolism are unrelated to LBBB.
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