MM is 94 years old. Her only active medical issues are hypertension and vitamin D deficiency. She takes only 20 mg of lisinopril and 1000 units of vitamin D3 each day. She has no cognitive decline and gardens every day if the Chicago weather allows. Her Friday afternoon appointment is the...

A few short words about our conversation: Two decades have passed and electrophysiologists have learned little about how to ablate atrial fibrillation. Now, and then, we simply ablate circles around the orifices of the pulmonary veins. This works reasonably well. But we don’t—exactly—know why...