[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Clinical exam](https://durgical.com/en/clinical-exam/) › [Cardiovascular system](https://durgical.com/en/clinical-exam/#a-cardiovascular) › Heart sounds: S1, S2 and its splitting, S3 and S4 [Clinical exam](https://durgical.com/en/clinical-exam/) · [Cardiovascular system](https://durgical.com/en/clinical-exam/#a-cardiovascular) # Heart sounds: S1, S2 and its splitting, S3 and S4 - Sign The heart's two normal beats are its valves closing; extra sounds point to stiff or overloaded ventricles. Updated 2026-11-01 **See it in 3D:** [Mitral anterior leaflet](https://durgical.com/en/anatomy/anterior-leaflet-of-left-atrioventricular-valve/) · [Tricuspid septal leaflet](https://durgical.com/en/anatomy/septal-leaflet-of-right-atrioventricular-valve/) · [Aortic left coronary cusp](https://durgical.com/en/anatomy/left-coronary-leaflet/) · [Pulmonary left cusp](https://durgical.com/en/anatomy/left-semilunar-leaflet-of-pulmonary-valve/) · [Chordae tendineae](https://durgical.com/en/anatomy/chordae-tendineae-of-right-atrioventricular-valve/) ## Key points - S1 = mitral and tricuspid closure (apex); S2 = aortic and pulmonic closure (base). - Fixed S2 split = atrial septal defect; paradoxical split = left bundle branch block or severe aortic stenosis. - S3 = volume-overloaded ventricle (systolic heart failure); S4 = stiff ventricle. - No S4 in atrial fibrillation. ## What it is S1 marks the start of systole and S2 its end. Splitting of S2 with breathing is normal; its variants point to bundle branch blocks, shunts or pulmonary hypertension. S3 and S4 are the gallops: they tell how the ventricle fills. ## The anatomy it tests - S1: closure of the mitral and tricuspid valves as ventricular contraction begins. - S2: closure of the aortic (A2) and pulmonic (P2) valves. On inspiration more blood returns to the right ventricle, the pulmonic valve closes later and S2 splits. - S3: early diastole, rapid filling striking a dilated or volume-loaded ventricle. - S4: late diastole, atrial contraction against a stiff ventricle; it needs an atrial kick (absent in atrial fibrillation). ## How to elicit it - Listen at the four areas while feeling the carotid pulse: the sound that coincides with the pulse is S1. - S1 is loudest at the apex; S2 at the base (aortic and pulmonic areas). - For S2 splitting, listen at the pulmonic area during quiet breathing: it splits on inspiration and fuses on expiration. - For S3 and S4, turn the patient to the left lateral decubitus and rest the bell lightly on the apex. - Record the intensity of S1 and S2, the type of splitting and any extra sound (gallop, click, opening snap). ## What a positive result means - Loud S1: mitral stenosis, short PR, tachycardia. Soft S1: long PR, mitral regurgitation, poor ventricular function. - Loud P2: pulmonary hypertension. Soft A2: severe aortic stenosis. - Wide splitting (persists in expiration, widens on inspiration): right bundle branch block, pulmonic stenosis. - Fixed splitting (no change with breathing): atrial septal defect. - Paradoxical splitting (appears on expiration): left bundle branch block, severe aortic stenosis. - S3 after age 40: heart failure with a dilated or volume-overloaded ventricle; may be normal in children, young adults, athletes and pregnancy. - S4: hypertrophied or stiff ventricle (hypertension, aortic stenosis, hypertrophic cardiomyopathy, ischemia). ## Usefulness and limits - S3 and S4 are low-pitched and soft: they are missed with the diaphragm alone. - Inter-observer agreement for gallops is moderate; echocardiography defines ventricular function. ## Test yourself Think of the answer, then tap the question to see it. ## Which valves produce the first heart sound? The mitral and tricuspid valves, closing at the start of ventricular systole. ## Which heart defect gives fixed splitting of S2? Atrial septal defect: the shunt evens out filling of both ventricles in both phases of breathing. ## Why is there no S4 in atrial fibrillation? S4 depends on an effective atrial contraction against a stiff ventricle, and in atrial fibrillation there is none. ## What does an S3 suggest in a breathless 65-year-old? Heart failure with a dilated or volume-overloaded ventricle. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/clinical-exam/heart-sounds-s1-s2-and-its-splitting-s3-and-s4/) ## See it in 3D The structures of Durgical's 3D anatomy where it is found. - [Mitral anterior leaflet](https://durgical.com/en/anatomy/anterior-leaflet-of-left-atrioventricular-valve/) - [Tricuspid septal leaflet](https://durgical.com/en/anatomy/septal-leaflet-of-right-atrioventricular-valve/) - [Aortic left coronary cusp](https://durgical.com/en/anatomy/left-coronary-leaflet/) - [Pulmonary left cusp](https://durgical.com/en/anatomy/left-semilunar-leaflet-of-pulmonary-valve/) - [Chordae tendineae](https://durgical.com/en/anatomy/chordae-tendineae-of-right-atrioventricular-valve/) ## Related - [Cardiac auscultation: the areas and the order](https://durgical.com/en/clinical-exam/cardiac-auscultation-the-areas-and-the-order/) - [Murmurs: timing, grade, location and radiation](https://durgical.com/en/clinical-exam/murmurs-timing-grade-location-and-radiation/) - [Heart failure syndrome: left- and right-sided signs](https://durgical.com/en/clinical-exam/heart-failure-syndrome-left-and-right-sided-signs/) - [Dynamic auscultation: Valsalva, squatting, standing and handgrip](https://durgical.com/en/clinical-exam/dynamic-auscultation-valsalva-squatting-standing-and-handgrip/) ## Related conditions - [Heart failure](https://durgical.com/en/conditions/heart-failure/) - [Atrial septal defect](https://durgical.com/en/conditions/atrial-septal-defect/) - [Pulmonary hypertension and cor pulmonale](https://durgical.com/en/conditions/pulmonary-hypertension-and-cor-pulmonale/) - [Aortic Valve Stenosis](https://durgical.com/en/conditions/aortic-valve-stenosis/) - [Mitral stenosis](https://durgical.com/en/conditions/mitral-stenosis/) - [Hypertensive heart disease](https://durgical.com/en/conditions/hypertensive-heart-disease/) [← All of the clinical exam](https://durgical.com/en/clinical-exam/) Educational content on the clinical exam; it is learned and practised under supervision. It does not replace assessment by a health professional and is not for self-diagnosis. Sources: [19.3 Cardiac Cycle - Anatomy and Physiology 2e | OpenStax](https://openstax.org/books/anatomy-and-physiology-2e/pages/19-3-cardiac-cycle) (OpenStax (Rice University), 2022); [24.3 Nursing Assessment - Clinical Nursing Skills | OpenStax](https://openstax.org/books/clinical-nursing-skills/pages/24-3-nursing-assessment) (OpenStax (Rice University), 2024); [Mitral stenosis: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/000175.htm) (MedlinePlus, U.S. National Library of Medicine, 2026). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/clinical-exam/heart-sounds-s1-s2-and-its-splitting-s3-and-s4/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/clinical-exam/heart-sounds-s1-s2-and-its-splitting-s3-and-s4/