Abnormal heart sounds


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Abnormal heart sounds


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 work

Cardiac cycle

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


Abnormal heart sounds


0 / 14 complete

USMLE® Step 1 questions

0 / 5 complete

High Yield Notes

21 pages


Abnormal heart sounds

of complete


USMLE® Step 1 style questions USMLE

of complete

A 35-year-old woman presents to the clinic to establish care. She has not seen a doctor in many years. She has no active complaints. Physical examination is unremarkable. Cardiac auscultation reveals a midsystolic click followed by a short late-systolic murmur at the cardiac apex. When the patient is asked to bear down against a closed glottis, it makes the click occur earlier in systole. Which of the following is the most likely cause of change in the timing of systolic click with this maneuver?  

External References

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Aortic regurgitation

diastolic murmur in p. 297

heart murmurs with p. 298

Aortic root dilation

heart murmur with p. 298

Aortic stenosis

heart murmurs p. 298

systolic murmur in p. 297

Atrial septal defect (ASD) p. 305

diastolic murmur in p. 297

Bicuspid aortic valve

heart murmur with p. 298

Congenital rubella

heart murmur p. 298

Continuous heart murmurs p. 298


heart murmurs of p. 298, 298

Ehlers-Danlos syndrome p. 49

heart murmur with p. 298

Ejection murmur p. 716


heart murmurs p. 298

Heart murmurs p. 298

aortic regurgitation p. 716

aortic stenosis p. 716

auscultation of p. 297

cardiomyopathies p. 317

patent ductus arteriosus p. 305

Hypertrophic cardiomyopathy p. 317

systolic murmur in p. 297

Ischemic heart disease

heart murmurs in p. 298

Marfan syndrome

heart murmur with p. 298

Mitral regurgitation

murmurs caused by p. 297, 298

Mitral stenosis

murmurs caused by p. 297, 298

Multiple sclerosis p. 541

heart murmur with p. 298

Pansystolic murmur p. 297

Patent ductus arteriosus (PDA)

heart murmur with p. 298

Premature labor and delivery

murmur in prematurity p. 298

Pulmonic stenosis

systolic ejection murmur in p. 297

Rheumatic fever p. 321

heart murmur with p. 298

Rubella p. 166

heart murmur with p. 298


heart murmurs of p. 298, 298

Systolic murmur p. 317

Tricuspid regurgitation

heart murmurs with p. 298

pansystolic murmur in p. 297

Ventricular septal defect (VSD) p. 305, 728

heart murmurs p. 298

pansystolic murmur in p. 297

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Content Reviewers

Rishi Desai, MD, MPH


Antonia Syrnioti, MD

Sam Gillespie, BSc

Marisa Pedron

Tanner Marshall, MS

Justin Ling, MD, MS

If you put a stethoscope over the chest, you’ll usually hear something that sounds like lub dub, lub dub, lub dub, which repeats over and over again, with each cardiac cycle, or heartbeat.

In total, our heart has four valves- two atrioventricular valves, between the atria and the ventricles, which are the tricuspid valve, on the Left side, and the mitral valve, on the left side, and two semilunar valves, between the ventricles and the large arteries coming off of them, which are the pulmonary valve, on the right side, and the aortic valve, on the left side. Normally, in every heartbeat, some valves open, allowing blood to pass through and others close to hold blood within a chamber. The sound of the closing of each of these valves is projected onto the chest wall. The two normal heart sounds are S1, which is basically the tricuspid and mitral valve closing, and S2 which is the aortic and pulmonic valve closing. Between S1 and S2, we have systole, which is when ventricles are contracting and pushing blood out, and between S2 and S1 of the next heart cycle, we have diastole which is when blood is filling the relaxed ventricles. Together, S1 and S2 form the “lub dub” of the heart beat.

Alright, now in addition to S1 and S2, there are two other "extra" sounds that are sometimes heard in the cardiac cycle, called S3 and S4. S3 and S4 are heard in different parts of diastole. In early diastole, which is right after S2, the atrioventricular valves are open and blood is flowing from the atria into the ventricles. If there’s a lot of blood coming in, the ventricles fill up quickly, and fluid waves bounce off of the walls of the ventricles which makes them vibrate, creating a third heart sound, or S3. S3 sounds kind of like “lub-dub-ta”. In trained athletes and also in pregnancy this is totally normal and just means that the ventricles are handling extra blood volume. But an S3 can also be a sign of volume overload, like in congestive heart failure, where there’s too much volume coming into the ventricles. Now, at the end of diastole, just before S1, the atria are contracting to get that last bit of blood into the ventricles. If the ventricles are stiff, meaning that they can’t easily relax, the atria will have to contract extra hard to push that blood in, creating the fourth heart sound, or S4. So, S4 sounds kind of like "ta-lub-dub". Oftentimes, this stiffness is because the ventricular muscles have hypertrophied, or increased in size, in order to pump against high blood pressure in the aorta or pulmonary artery. In other words, S4 is typically a sign of pressure overload, or severe hypertension.


  1. "Medical Physiology" Elsevier (2016)
  2. "Physiology" Elsevier (2017)
  3. "Principles of Anatomy and Physiology" Wiley (2014)
  4. "Aortic origin of innocent murmurs" The American Journal of Cardiology (1977)
  5. "Still's-like innocent murmur can be produced by increasing aortic velocity to a threshold value" The American Journal of Cardiology (1991)
  6. "Human Anatomy & Physiology" Pearson (2018)

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