How Your Ejection Fraction (EF) is like the Number of Cylinders in a Car

There are many ways to assess the function of your heart, and one of the easiest and most convenient methods is with an ultrasound of your heart called a echocardiogram. During a transthoracic echocardiogram, you will be asked to lay on your left side and an ultrasound technician will obtain images of your heart using sound waves.



From these images, your cardiologist can determine the size of your heart chambers, the structure and function of your valves, how well your heart squeezes, and the pressures within the heart.

How well your heart squeezes with every beat is called the ejection fraction, which represents the volume of blood pumped by your left ventricle divided by the total volume of blood in that ventricle. The ejection fraction, or EF, is represented as a percent. Roughly speaking, normal EF’s range between 55-70% and low normal EF is 50-55%. Ejection fractions less than 50% are reduced.

To explain and simplify the concept of ejection fraction to my patients, I sometimes use the analogy that your EF is like the number of cylinders in a sports car. Many sports cars have 6 cylinders. Think of a car having 6 cylinders as being proportional to a person with an EF of 60%.  As the number of cylinders that are functional decrease, the power to the car also decreases and its harder to get the car to zip along like normal. Similarly, as the EF decrease, patients generally begin to experience symptoms consistent with a failing heart. These symptoms can include shortness of breath, swelling in the legs, waking up at night gasping for air, or having to sleep on many pillows.

If you have heart failure, make sure you are aware of what your ejection fraction is to gauge your treatment progress. Read more about ejection fraction and ways to measure it from the American Heart Association.

Image: NHLBI