ECG Challenge: What’s Behind This Man’s Mid-systolic Murmur?

A 55-year-old man with a history of mild aortic stenosis presents to his cardiologist for a routine exam. He says he has no cardiac symptoms and is physically active. Physical examination is unremarkable except for a Grade 1 harsh mid-systolic murmur. Pulses and vital signs are normal. A 12-lead ECG is obtained (Figure 1).

Figure 1.