By Zaki Khan, MBS 2019, Geisinger Commonwealth School of Medicine

Mentor: Gabi Waite, PhD


When you think of your heart, you think of emotion, love, warmth, and any other word that can describe the mushy gushy feeling one feels. Well, I am here to tell you that there is more to the heart than one can imagine, and the best part is that the heart does love you: thus, it takes care of you and keeps you healthy and stress-free.

For instance, your heart has two types of involuntary responses. One is called “rest-and-digest,” or the relaxed mode, a normal day to day feeling. The other is called “flight-or-fight,” or the panic button your body pushes after you see a bear running towards you. Let’s say you see the bear, you scream, and your heart rate goes up and is beating very fast. Your body is only responding this way because it is helping you escape from the bear, and I will tell you how it is helping you as you keep reading.

Now, you have successfully escaped the bear. Congratulations! How do you think your heart rate is responding at this moment? Probably not elevated like before when you were being chased. Your heart rate should be approaching normal levels at this point after you’ve remained calm, relaxed, and back to your normal day to day self. I am sure you’re wondering how your heart can be so generous by decreasing your heart rate back to normal levels without you telling it to do so. This is where heart rate variability becomes relevant. It is defined as a variation in time between each heartbeat. The idea is that if you maintain your body in relaxed mode, there is more variation and flexibility or more wiggle room to handle stressful situations in a healthy way. Therefore, rest-and-digest correlates with high heart rate variability, which keeps your body ready whenever a stressor comes your way.

However, this is not the case for the flight-or-fight response. Would you say this type of response has more or less variability? The answer is that it will have less variability and let me tell you why. While you are running from the bear, what is the one thought that is crossing your mind? Surviving, right? So, your heart rate variability is going to lessen because your heart only cares about making sure your heart is beating fast enough for oxygen to be sent to your skeletal muscles so you can continue running as fast as you can. In other words, you are keeping the heart rate consistently high. Notice I used the word, “consistently” as this is the opposite of variable; no wonder HRV levels are low. In the context of the bear chase, your eye on the prize is “safety” and so you maintain a condensed (less wiggle room) and consistent tunnel vision focusing only on safety and this is not healthy, it makes it difficult to switch into positive gear and have flexibility to manage stressful situations. This is why research shows that there is a relationship between low HRV levels and worsening anxiety and depression, and it can even lead to death or a cardiovascular condition.

I am not saying you will get attacked by a bear every day, but now you know that with any type of stressor, you should be more prepared to maintain a relaxed state, which in turn, keeps your HRV levels high and you are more resilient to handle stress in a healthy manner. To maintain your HRV at high levels, it is best to practice a healthy lifestyle such as exercising, meditation, sleep, and mindfulness. This lifestyle will help you manage stress without hitting the panic button. Unfortunately, when one has been diagnosed with a cardiovascular disease, like coronary artery disease or recently been a victim of a heart attack, HRV levels is steering itself towards lower variability levels because the heart is defective, putting oneself at a disadvantage of not having the flexibility to manage stress. Therefore, those with cardiovascular problems tend to have low heart rate variability levels.

What if we can turn this around by generating a device that can accurately test HRV, so we can prevent worse cardiovascular issues and heart attacks in the future? Fortunately, the HRV test is still in the works and more and more research is being done to perfect its validity. The goal is to implement this test with a small gadget that can be worn on your wrist (like a Fitbit) and you can monitor your HRV levels to curb worsening symptoms of coronary artery disease or having another heart attack.

I hope you enjoyed learning about the mysteries of the heart, the one organ that is trying to keep your body healthy and at safe physiological levels. Now, that’s what I call love!