World Heart Day: How to track your heart health on Apple Watch

Perhaps, at no other time has public awareness of heart health been as high as it is today. With even those who exercise assiduously being at risk of cardiac events, there is an obvious need for everyone to understand their heart health better.

An easy way to track fitness level in recent times has been with a smartwatch or a fitness band. The cheapest of these gadgets measures just the heart rate, replaces an oximeter, counts step, tracks workouts and calories. But what does one really do with a heart rate count? How do all the metrics from a smartwatch add up to give insights into heart health? It is undoubtedly the Apple Watch that gives the most comprehensive and usable data for those looking to improve heart health and even prevent fatal events in time.

Resting easy

On the surface, one way to gauge fitness level is to check the resting heart rate. Athletes tend to have low rates going down to the 40’s, but it would be more normal for the average active person to have a resting rate of between 60 and 70. Much higher rates could be an indication that one needs to increase daily exercise level, go for tests or check with a doctor.

High and low

In general, the Apple Watch checks for unusually high or low heart rates in the background, which could be signs of a serious underlying condition. This could help users identify situations that may warrant further evaluation. If a user's heart rate is above 120 bpm or below 40 bpm while they appear to have been inactive for 10 minutes, they will receive a notification. The user can keep an eye on the heart rate to figure out what heart rate ‘zone’ to stay in for a period while working out. When the heart rate is unusually high at a time when the watch senses no exercise is being done, it may be time to check with a doctor.

Other than resting rate, walking average, workout and recovery rate can also be in the health app in the form of heart history. This is in graphs that are meant to be shared with one’s doctor who will know what to do with the data, if anything. All irregular events will also be recorded and can be discussed with medical professionals.

Single lead ECG

The Apple Watch also famously has an ECG measure. With this and the app on the watch, users who experience symptoms such as rapid or skipped heartbeat, can capture an ECG and record their symptoms. The ECG feature uses the electrical heart sensor built into the Digital Crown and the back crystal to record a single-lead ECG. The ECG app then provides a result of sinus rhythm, atrial fibrillation, atrial fibrillation with high heart rate, inconclusive, or poor recording, and prompts the user to enter any symptoms such as rapid or pounding heartbeat, dizziness, or fatigue. The recorded waveform, results, date, time, and any symptoms are recorded and can be exported from the Health app as a PDF to share with a clinician. 

Recording the ECG takes no learning curve at all. It’s quick and easy but fortunately not ‘addictive’ in the sense that the feature doesn’t compel users to keep retrying a recording. This is perhaps because one is not presented with a figure and only a category.   In a clinical study using a 12-lead ECG as a reference device, the ECG app demonstrated 99.3% specificity in classifying sinus rhythm and 98.5% sensitivity in classifying AFib for the classifiable results.

From the beginning, the heart rate measurement on this device has been oriented towards trying to identify AFib or Atrial Fibrillation, AFib is a type of irregular heart rhythm where the upper chambers of the heart beat out of sync with the lower chambers. This is a common problem and can lead to a stroke.

Staying cardio-fit

A measure of VO2 Max, or the body's ability to intake oxygen during exercise is thought to be an important piece of information to gauge cardio fitness and overall. It is usually an intense test done in a lab. The Apple Watch now incorporates this measure and gives notifications for low V02 which can be associated with serious longterm health conditions. Fortunately, it is something one can improve by exercising more frequently or more rigorously, and something to track along the way.