Cardiac work


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Cardiac work

Cardiovascular system

Anatomy and physiology

Cardiovascular system anatomy and physiology

Lymphatic system anatomy and physiology

Coronary circulation


Blood pressure, blood flow, and resistance

Pressures in the cardiovascular system

Laminar flow and Reynolds number

Resistance to blood flow

Compliance of blood vessels

Control of blood flow circulation

Microcirculation and Starling forces

Cardiac output

Measuring cardiac output (Fick principle)

Stroke volume, ejection fraction, and cardiac output

Cardiac contractility

Frank-Starling relationship

Cardiac preload

Cardiac afterload

Law of Laplace

Cardiac and vascular function curves

Altering cardiac and vascular function curves

Cardiac cycle and pressure-volume loops

Cardiac cycle

Cardiac work

Pressure-volume loops

Changes in pressure-volume loops

Cardiovascular physiological responses

Physiological changes during exercise

Cardiovascular changes during hemorrhage

Cardiovascular changes during postural change

Auscultation of the heart

Normal heart sounds

Abnormal heart sounds

Myocyte electrophysiology

Action potentials in myocytes

Action potentials in pacemaker cells

Excitability and refractory periods

Cardiac excitation-contraction coupling


Electrical conduction in the heart

Cardiac conduction velocity

ECG basics

ECG normal sinus rhythm

ECG intervals

ECG QRS transition

ECG axis

ECG rate and rhythm

ECG cardiac infarction and ischemia

ECG cardiac hypertrophy and enlargement

Blood pressure regulation



Renin-angiotensin-aldosterone system


Cardiac work


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Cardiac work

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Content Reviewers

Robyn Hughes, MScBMC

Viviana Popa, MD


Sam Gillespie, BSc

David G. Walker

Cardiac work, also known as stroke work, is similar to the concept of work in physics. In physics, work is defined as force times distance.

Stroke work can be thought of as the work performed by the left ventricle to eject a volume of blood, defined as stroke volume multiplied by mean aortic pressure.

And here, stroke volume corresponds to distance, whereas mean aortic pressure corresponds to force. Stroke work is best represented by a pressure-volume loop.

Pressure- volume loops are graphs, where the pressure inside the left ventricle is on the y axis and the volume of the left ventricle is on the x axis.

Each loop represents changes in ventricular pressure and volume over the course of one cardiac cycle, or one heartbeat, which includes both ventricular systole, or contraction, and diastole, or relaxation.

The lower right hand corner is the end-diastolic point, and it’s the point in the cardiac cycle when diastole is over. Αt this point, the mitral valve between the left atrium and the left ventricle, closes, leaving the left ventricle filled with the maximum volume of blood, called the end-diastolic volume.

And then, systole begins, which is when the left ventricle contracts to push that blood into the aorta. Ventricular contraction makes the pressure shoot up, but for a brief period of time, both the mitral and aortic valves are closed, so left ventricular volume doesn’t change.

This phase is isovolumetric contraction, but it doesn’t last long, because eventually the pressure inside the left ventricle exceeds aortic pressure, making the aortic valve pop open, and that starts the ejection phase.


The cardiac cycle, also called the stroke work, is the work performed by the heart's left ventricle during an ejection of a blood volume. It is the performance of the heart from the beginning of one heartbeat to the beginning of the next, and equals to the product of the mean aortic pressure and stroke volume, which is the amount of blood pumped by the left ventricle in one beat. Cardiac work done in a full minute will be referred to as cardiac minute work. It is equal to the product of mean aortic pressure and cardiac output, since the cardiac output equals heartbeats in one minute times the stroke volume.


  1. "Medical Physiology" Elsevier (2016)
  2. "Physiology" Elsevier (2017)
  3. "Human Anatomy & Physiology" Pearson (2018)
  4. "Principles of Anatomy and Physiology" Wiley (2014)

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