One of the tests that doctors use to assess your heart health is an electrocardiogram (ECG). It involves attaching electrode sensors to your chest and monitoring your heart’s electrical activity.
The results of an ECG can show how well your heart is functioning and whether or not you are showing signs of any heart conditions, such as heart failure, irregular heartbeat, or low blood flow to your heart.
A few decades ago, it was noted that when a patient rolled onto their side while hooked up to an ECG, the heart’s electrical activity would sometimes change, potentially causing false alarms in the monitoring procedures.
In 1997, researchers investigated this phenomenon and found that right and left side-lying positions frequently induce clinically significant changes in the ECG readings. The changes were more pronounced in the left-sided position and more common in patients with cardiac disease than in healthy individuals.
Why Does It Happen?
A follow-up study in 2018 confirmed these findings and additionally performed vectorcardiography imaging to determine why this was happening.
When you lay on your left side, your heart slightly shifts and rotates, causing a noticeable change in electrical activity. The mediastinum (the primary tissues between your lungs) holds the heart in place in the right-sided position, leading to less movement and less change in the ECG readings.
Does It Really Matter?
Despite the observed change in electrical activity, there isn’t any evidence that this position is bad for your heart health.
Patients with prior experience with heart failure or other underlying heart conditions sometimes report discomfort when lying on their left side, but this is likely due to the position exacerbating symptoms that are already present rather than causing new problems.
There isn’t clear evidence that any one position is best for heart health. However, it is known that not enough high-quality sleep can increase your risk of heart disease and chronic illness. Find the most comfortable posture for you and allow you to get plenty of restful and nourishing sleep, no matter which side you lay on.
Sleeping on your back is another good option, though people with sleep apnea or obesity often report difficulty breathing in this position. And patients with underlying heart conditions may have poorer blood flow and blood oxygenation in a face-up position.
If you experience persistent discomfort in any position while sleeping, consult with a doctor to rule out any underlying health conditions.