This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Electrocardiography, Subject name: Medicine
Left bundle branch block (LBBB) on ECG can suddenly develop in all of the following except: 
Select and explain. 
A. Acute MI, B. Ashman phenomenon, C. Hypokalemia, D. Hyperkalemia
B: Ashman phenomenon
Answer: B: Ashman phenomenon 
Explanation: Ans. b. Ashman phenomenon (Ref: Harrison 18/e p1835) style="font-size: 1.04761904761905em; font-weight: bold; font-family: Times New Roman, Times, serif; margin: 0 0 0 8px; text-indent: 0">Ashman phenomenon:Ashman phenomenon is an intraventricular conduction abnormality caused by a change in the heart rate.Wide QRS complex) on the surface ECGA RBBB pattern is more common because of the longer refractory period of the right bundle branch, although association with LBBB has been documentedCauses of Left Bundle Branch Block (LBBB)* Aortic stenosis* Dilated cardiomyopathy* Acute myocardial infarction* Extensive coronary artery disease* Primary disease of the cardiac electrical conduction system* Long standing hypertension leading to aortic root dilatation and AR* Hypokalemia* Hyperkalemia