You can take an electrocardiogram (ECG) with the ECG app. ECG or electrocardiogram (also called an EKG) is a test that records the timing and strength of the electrical signals that make the heart beat. By looking at an ECG, a doctor can gain insights about your heart rhythm and look for irregularities. The ECG app can record your heartbeat and rhythm using the electrical heart sensor on Apple Watch Series 4 and then check the recording for atrial fibrillation (AFib), a form of irregular rhythm. The ECG app records an electrocardiogram which represents the electrical pulses that make your heart beat. The ECG app checks these pulses to get your heart rate and see if the upper and lower chambers of your heart are in rhythm. If they’re out of rhythm, that could be AFib.

If Apple Watch Series 4 detects a hard fall, it can help connect you to emergency services if needed. If Apple Watch Series 4 detects a hard fall it taps you on the wrist, sounds an alarm, and displays an alert. You can choose to contact emergency services or dismiss the alert by pressing the Digital Crown, tapping Close in the upper-left corner, or tapping "I'm OK.". If your Apple Watch detects that you're moving, it waits for you to respond to the alert and won't automatically call emergency services. If your watch detects that you have been immobile for about a minute, it will make the call automatically. After the call ends, your watch sends a message to your emergency contacts with your location letting them know that your watch detected a hard fall and dialed emergency services.