From the commments on the article itself:

Cardiogram engineer here. 97% accuracy refers to a c-statistic (area under the ROC curve) of 0.9740. An example operating point would be 98% sensitivity with 90% specificity.

These important details are often lost in the news. You can some more details on our findings in our blog post:

https://blog.cardiogr.am/applying-artificial-intelligence-in...