Let’s dive into some essential cardiology terms you’ll need to know.

Systole and Diastole

First off, you’ll hear about systole and diastole, as well as systolic and diastolic blood pressure.

Systolic Blood Pressure

This is the top number in a blood pressure reading. It measures the pressure in your arteries when your heart beats and the ventricles contract to pump blood out.

Diastolic Blood Pressure

This is the bottom number, representing the pressure in your arteries when the heart is at rest between beats and the ventricles are filling with blood.

Preload and Afterload


This is the amount of blood returning to the heart. Think of it as the volume of blood coming back to the right atrium from the venous system.


This is the pressure the left ventricle must overcome to pump blood into the aorta. High afterload means the heart has to work harder to push blood out.

Automaticity and Contractility


This is the heart muscle’s ability to contract independently without needing a signal from the nervous system. The cardiac cells do this automatically.


This refers to the strength of the heart’s contractions. It determines how forcefully the ventricles can pump blood with each beat.

Cardiac Output, Stroke Volume, and Heart Rate

Cardiac Output

This is the amount of blood the heart pumps in one minute, measured in liters per minute.

Stroke Volume

This is the amount of blood ejected by the heart in one contraction, measured in milliliters.

Heart Rate

This is the number of heartbeats per minute.

The equation for cardiac output is:

CO = SV x HR
CO = Cardiac Output
SV = Stroke Volume
HR = Heart Rate

For example, if your stroke volume is 100 mL and your heart rate is 60 beats per minute, your cardiac output would be:

Stroke Volume (SV) = 100 mL (which is 0.1 liters, since 1,000 mL = 1 liter)
Heart Rate (HR) = 60 beats per minute

CO = 0.1 liters/beat x 60 beats/minute
CO = 6 liters/minute

Ejection Fraction

This is an important measure in heart function, especially for patients with heart failure or those needing heart transplants.

Ejection Fraction (EF)

This is the percentage of blood pumped out of the ventricles with each contraction. A normal EF is between 50% and 75%.

The equation for ejection fraction is:

EF = Ejection Fraction
SV = Stroke Volume
EDV = End-Diastolic Volume

For instance, if your stroke volume is 70 mL and your end-diastolic volume is 120 mL, your ejection fraction would be:

EF = 70 mL/120 mL x 100
EF = 70/120 x 100
EF = 0.5833 x 100
EF = 58.33% (within normal range)

A normal ejection fraction indicates good heart function, while a low ejection fraction can signify heart disease or heart failure.

Remember these key terms and equations—they are crucial for understanding how the heart works and for effectively assessing cardiac patients.