A Stethoscope That Can See

A new tool lets doctors turn sound waves into graphs.

For nearly 200 years, the stethoscope has allowed doctors to eavesdrop on the beat of patients’ hearts and the whoosh of their blood. Although the device has been refined over time, its effectiveness still depends on a decidedly low-tech variable: the human ear. Even the most attuned examiner might imagine hearing a subtle abnormality, leading to expensive and ultimately unnecessary tests—or miss one, overlooking a potential red flag.

The CardioSleeve, a new, FDA-approved accessory, transforms a standard analog stethoscope into a visual, as well as aural, tool. The device, which faces the usual financial and habitual barriers to adoption, digitally records a patient’s heartbeat while simultaneously taking an electrocardiogram, similar to an ultrasound...