A Bone-Deep Heart Threat Emerges

Brian Gear, who has clonal hematopoiesis of indeterminate potential, or C.H.I.P., which greatly increases his odds of heart attack or stroke, in Braintree, Mass., Dec. 13, 2017. C.H.I.P. is emerging as a major cause of heart attacks and stroke, as deadly as high blood pressure or cholesterol. (Kayana Szymczak/The New York Times)