Cardiac preload


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Cardiac preload

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 preload


0 / 7 complete

USMLE® Step 1 questions

0 / 1 complete

High Yield Notes

10 pages


Cardiac preload

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USMLE® Step 1 style questions USMLE

of complete

A scientist is studying the effect of different pathologic processes on cardiac preload. An increase in preload will be observed in which of the following conditions?  

External References

First Aid








ACE inhibitors p. 634

preload/afterload effects p. 292

Angiotensin II receptor blockers p. 634

preload/afterload effects p. 292

Preload in cardiac output p. 292

External Links


Content Reviewers


Filip Vasiljević, MD

Sam Gillespie, BSc

Pauline Rowsome, BSc (Hons)

Cardiac preload is one of the main factors that influence how much blood the heart pumps out with each heartbeat, or stroke.

Now, remember that the heart has two upper chambers: the left atrium, which receives oxygenated blood from the lungs via the pulmonary veins; and the right atrium, which receives deoxygenated blood from all of our organs and tissues via the superior and inferior vena cava.

From the atria, the blood flows into the lower chambers of the heart: the left ventricle, which pumps oxygenated blood to all our organs and tissues via the aorta; and the right ventricle, which pumps the deoxygenated blood back to the lungs via the pulmonary arteries.

Alright, now, each heartbeat consists of two phases: systole, which is when the heart contracts and pumps the blood out of the ventricles; and diastole, which is when the heart relaxes and ventricles fill with blood.

And as the left ventricle fills with blood during diastole, the pressure within it rises.

The pressure at the end of diastole is called the left ventricular end-diastolic pressure, which is a key determinant of cardiac preload.

So, cardiac preload can be defined as the ventricular wall stress at the end of diastole.

And it can be calculated using the law of Laplace, which states that wall stress = pressure (P) x radius (R) / 2 x wall thickness (W).

Another way to say this is that cardiac preload is directly proportional to the end-diastolic pressure and radius of the left ventricle, and indirectly proportional to two times the ventricular wall thickness.


Cardiac preload is the extent to which the left ventricular wall stretches at the end of diastole, or before systole starts. The amount of left ventricular wall stress is directly proportional to the ventricular end-diastolic pressure and the radius of the left ventricle, and indirectly proportional to two times the thickness of the left ventricular wall. Factors that increase preload include an increase in venous return (due to increased venous pressure or increased heart rate), an increase in arterial elastance, or an increase in myocardial contractility. Factors that affect preload include venous return, atrial contraction, heart rate, resistance from valves, and ventricular compliance.


  1. "Medical Physiology" Elsevier (2016)
  2. "Physiology" Elsevier (2017)
  3. "Human Anatomy & Physiology" Pearson (2017)
  4. "Principles of Anatomy and Physiology" Wiley (2014)
  5. "Physiology" Basic Science in Obstetrics and Gynaecology (2010)
  6. "Principles and Techniques of Blood Pressure Measurement" Cardiology Clinics (2010)

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