The study hinges on the early detection of atrial fibrillation (AFib), which is an irregular heart rhythm that causes poor blood flow and is a leading cause of stroke. While the link between atrial fibrillation and stroke is thoroughly understood, AFib has very few warning signs, making it difficult to diagnose until a stroke occurs. Johnson & Johnson and Apple are hoping that apps and the Apple Watch's electrocardiogram (ECG) features will help detect AFib before a stroke occurs. This trial follows a Stanford study that found that the Apple Watch's irregular heart rate monitoring features are accurate enough to use in a medical setting.

Since this is a virtual trial, participants don't have to travel to a clinical trial site -- they can partake remotely via a proprietary app. The Heartline study could help prevent strokes and deaths -- AFib leads to 158,000 deaths per year -- and could lead the way toward a new approach to clinical trials that leverage greater sample sizes and more consistent reporting. Those interested in participating can sign up at Heartline.com.