Kardio and other devices like the Apple watch that can detect an arrhythmia DO NOT work if you have a pacemaker. I have a biventricular Pacemaker and after I had it put in, my Apple watch no longer detected even a sinus rhythm. Apple said it states this in the fine print and cardiologist said the same thing when I asked about getting a Kardio device. Best option is to learn how to check your pulse for an irregularly irregular heart beat or a rate so fast that you can't even count it. Then always call your Doc or 911 if you are not feeling well. It's important to remember that Afib and flutter are not necessarily life threatening conditions even though they can make you feel pretty awful. But it is always best to get checked out when you don't feel right. Learn to listen to your body!