Table of ContentsView AllTable of ContentsWhat Makes the Noise?Cardiac CycleLoud S1Soft or Muffled S1TreatmentOther Heart SoundsMonitoring and ManagementWhen to See a Provider
Table of ContentsView All
View All
Table of Contents
What Makes the Noise?
Cardiac Cycle
Loud S1
Soft or Muffled S1
Treatment
Other Heart Sounds
Monitoring and Management
When to See a Provider
The first heart sound, or S1, is the “lub” of a normal heartbeat. It’s a high-pitched sound that occurs at the beginning of systole—when the heart pumps blood out of the heart into the lungs or body.
An unusually loud or soft S1, as well as extra vibratory heart sounds (“murmurs”), can indicate an underlying heart disorder.
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The first heart sound is a higher-pitched sound that can be heard with astethoscope’sdiaphragm (the bigger circular part).
The S1 noise is made when thetricuspidandmitralvalves close as blood cycles through theheart’s four chambers.
These four chambers include:
Thetricuspid valveconnects the right atrium and right ventricle, and themitral valveconnects the left atrium and ventricle.
When the tricuspid and mitral valves close, the ventricles squeeze (contract) and pump blood.
Specifically, the right ventricle pumps blood to the lungs to be oxygenated, whereas the left ventricle pumps oxygenated blood to theaorta, the main artery that delivers blood to the rest of the body.
Understanding the Cardiac Cycle
The cardiac cycle is a precise sequence of events the heart muscle performs during each heartbeat.
A single cardiac cycle consists of two components—systoleanddiastole.
Systoleoccurs when the heart muscle contracts and pumps deoxygenated blood into the lungs or to vital organs via the aorta (after it’s oxygenated in the lungs).
When Does S1 Occur?
Diastoleis when the heart muscle relaxes and refills with oxygenated blood returning from the lungs or deoxygenated blood from other body parts via the vena cava.
The vena cava is the largest vein in the body, carrying deoxygenated blood to the heart from the upper body parts (superior vena cava) and lower body parts (inferior vena cava).
Order of Blood Flow Through the Heart
What Does a Loud S1 Sound Mean?
Mitral stenosis andtachycardiaare two health conditions associated with a loud S1.
Mitral Stenosis
Mitral stenosisoccurs when the mitral valve’s opening narrows, impairing blood flow from the left atrium to the left ventricle.
Rheumatic fever—a complication of the bacterial infection “strep throat”—is the most common cause of mitral stenosis.Mitral stenosis may also be present at birth or develop after radiation therapy to the chest area.
The S1 is loud in mitral stenosis because the mitral valve leaflets are thick and close abruptly. It is best heard at the apex (the heart’s bottom tip, which points left and downward).
Besides a loud S1, an “opening snap” heard onauscultationin early diastole is a classic finding of mitral stenosis.
Tachycardia
Tachycardiaoccurs when the heart beats faster than normal, more than 100 beats per minute (bpm).Tachycardia causes a loud S1 from a higher force of ventricular contraction.
Types of tachycardia include:
What About a Soft or Muffled Sound?
Mitral regurgitation and severe congestive heart failure are two conditions associated with a soft and muffled S1.
Mitral Regurgutation
Mitral regurgitationis when the faulty valve allows blood to leak backward from the left ventricle into the left atrium.
Mitral regurgitation often develops from damage or weakening of the valve related to a heart problem such as:
The S1 is softer in mitral regurgitation because the mitral valve leaflets are rigid and do not fully close.
Another classic finding of mitral regurgitation is aholosystolicmurmur, best heard at the apex of the stethoscope’s diaphragm. With a holosystolic murmur, the extra heart sound starts after S1 and continues throughout systole until the second heart sound (S2) occurs.
Severe Congestive Heart Failure
Congestive heart failureis when the heart muscle is unable to pump blood well, and there is a buildup of fluid in the lungs and other parts of the body.
Symptoms and signs can include:
Severe or advanced congestive heart failure is when a person experiences worsening and/or persistent heart failure symptoms and signs despite undergoing various therapies.
The S1 is reported as soft and muffled in people with severe heart failure because of congested blood flow through the heart muscle and poor pumping ability of the heart.
4 Stages of Congestive Heart Failure: What Each Stage Means
Treatment for S1 Sound Deviations
The treatment of S1 sound deviations depends on the underlying cause.
As an example, general therapies potentially used to treat the following conditions associated with a loud S1 include:
Likewise, general therapies potentially used to treat conditions associated with a soft S1 include:
The second heart sound,S2, is the “dub” of a heartbeat. It occurs at the beginning of diastole when the pulmonary and aortic valves close as the ventricles relax and fill with blood.
Thepulmonary valveconnects the right ventricle and thepulmonary artery(the lung’s main artery), and theaortic valveconnects the left ventricle and theaorta.
LikeS1,S2is a high-pitched sound best heard with the stethoscope’s diaphragm.
Aside from the standardS1andS2heart sounds, there are also abnormal, extra heart sounds:
Murmurs may be “innocent,” occurring harmlessly in young children or during pregnancy. However, they can also be signs of an underlying heart problem, such as a faulty heart valve or acongenital (present at birth) heart defect.
Ongoing Heart Monitoring and Management
If you are diagnosed with a heart condition, such as heart valve disease, heart failure, or an arrhythmia, follow it closely with yourcardiologist(a doctor specializing in heart disorders).
Many heart conditions are lifelong and require close observation and minor adjustments to treatment plans over time. Depending on the condition, you may need to take one or more medications to, for example, decrease fluid buildup in your tissues, slow your heartbeat, or prevent blood clots.
In addition to attending appointments, you may need to perform activities at home, like tracking your weight to monitor edema or going in for periodic blood tests.
When to Contact a Healthcare Provider
If you are told you have a heart murmur, extra heart sound, or loud or soft heartbeat, see a healthcare professional, especially a cardiologist,
Moreover, seek medical attention if you are experiencing symptoms or signs of a possible heart condition, such as:
Summary
S1 is the first sound a healthcare provider hears when listening to a person’s heartbeat through their chest wall. S1 is the “lub” of a standard “lub-dub” heartbeat and is a high-pitched sound, so it’s best heard with the diaphragm (large circular part) of a stethoscope.
S1 happens when two of the heart’s valves, the mitral and tricuspid valves, close. These valves close in systole when the heart pumps blood into the lungs or out of the heart to the rest of the body.
A loud S1 sound can occur with mitral stenosis (narrowing of the valve) or tachycardia (when the heart beats faster than 100 beats per minute). A soft or muffled S1 can occur with mitral regurgitation (when the valve leaks blood backward) or severe/advanced heart failure.
Besides S1, there is also a second heart sound (S2), which is the “dub” of a heartbeat. In some cases, extra heart sounds like a third (S3) or fourth (S4) sound or brief, vibratory sounds (heart murmurs) may be present. Depending on the person’s age and clinical scenario, these extra sounds may be harmless or indicate an underlying heart disorder.
14 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Armstrong GP.Mitral stenosis. Merck Manual Professional Version.American Heart Association.Tachycardia: fast heart rate.Mayuga KA, Fedorowski A, Ricci F, et al.Sinus tachycardia: a multidisciplinary expert focused review.Circ Arrhythm Electrophysiol. 2022;15(9):e007960. doi:10.1161/CIRCEP.121.007960Yetkin E, Ozturk S, Cuglan B, Turhan H.Clinical presentation of paroxysmal supraventricular tachycardia: evaluation of usual and unusual symptoms.Cardiovasc Endocrinol Metab. 2020;9(4):153-158. doi:10.1097/XCE.0000000000000208Cronin EM, Bogun FM, Maury P, et al.2019 HRS/EHRA/APHRS/LAHRS expert consensus statement on catheter ablation of ventricular arrhythmias.Heart Rhythm.2020;17(1):e2-e154. doi:10.1016/j.hrthm.2019.03.002Armstrong GP.Mitral regurgitation. Merck Manual Professional Version.American Heart Association.Heart failure signs and symptoms.Fang JC, Ewald GA, Allen LA, et al.Advanced (stage D) heart failure: a statement from the Heart Failure Society of America Guidelines Committee.J Card Fail.2015;21(6):519-34. doi:10.1016/j.cardfail.2015.04.013Fujiyoshi K, Yamaoka-Tojo M, Fujiyoshi K, et al.Beat-to-beat alterations of acoustic intensity and frequency at the maximum power of heart sounds are associated with NT-proBNP levels.Front Cardiovasc Med. 2024;11:1372543. doi:10.3389/fcvm.2024.1372543National Heart, Lung, and Blood Institute.Heart treatments.Meyer TE.Patient education: mitral regurgitation (Beyond the Basics). In: UpToDate, Otto CM (Ed), Wolters KluwerColucci WS.Patient education: heart failure education (Beyond the Basics). In: UpToDate, Gottlieb SS (Ed), Wolters KluwerMeyer TE.Auscultation of heart sounds. In: UpToDate, Gersch BJ, (Ed), Wolters KluwerGupta JI, Shea MJ.Cardiac auscultation. Merck Manual Professional Version.
14 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Armstrong GP.Mitral stenosis. Merck Manual Professional Version.American Heart Association.Tachycardia: fast heart rate.Mayuga KA, Fedorowski A, Ricci F, et al.Sinus tachycardia: a multidisciplinary expert focused review.Circ Arrhythm Electrophysiol. 2022;15(9):e007960. doi:10.1161/CIRCEP.121.007960Yetkin E, Ozturk S, Cuglan B, Turhan H.Clinical presentation of paroxysmal supraventricular tachycardia: evaluation of usual and unusual symptoms.Cardiovasc Endocrinol Metab. 2020;9(4):153-158. doi:10.1097/XCE.0000000000000208Cronin EM, Bogun FM, Maury P, et al.2019 HRS/EHRA/APHRS/LAHRS expert consensus statement on catheter ablation of ventricular arrhythmias.Heart Rhythm.2020;17(1):e2-e154. doi:10.1016/j.hrthm.2019.03.002Armstrong GP.Mitral regurgitation. Merck Manual Professional Version.American Heart Association.Heart failure signs and symptoms.Fang JC, Ewald GA, Allen LA, et al.Advanced (stage D) heart failure: a statement from the Heart Failure Society of America Guidelines Committee.J Card Fail.2015;21(6):519-34. doi:10.1016/j.cardfail.2015.04.013Fujiyoshi K, Yamaoka-Tojo M, Fujiyoshi K, et al.Beat-to-beat alterations of acoustic intensity and frequency at the maximum power of heart sounds are associated with NT-proBNP levels.Front Cardiovasc Med. 2024;11:1372543. doi:10.3389/fcvm.2024.1372543National Heart, Lung, and Blood Institute.Heart treatments.Meyer TE.Patient education: mitral regurgitation (Beyond the Basics). In: UpToDate, Otto CM (Ed), Wolters KluwerColucci WS.Patient education: heart failure education (Beyond the Basics). In: UpToDate, Gottlieb SS (Ed), Wolters KluwerMeyer TE.Auscultation of heart sounds. In: UpToDate, Gersch BJ, (Ed), Wolters KluwerGupta JI, Shea MJ.Cardiac auscultation. Merck Manual Professional Version.
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
Armstrong GP.Mitral stenosis. Merck Manual Professional Version.American Heart Association.Tachycardia: fast heart rate.Mayuga KA, Fedorowski A, Ricci F, et al.Sinus tachycardia: a multidisciplinary expert focused review.Circ Arrhythm Electrophysiol. 2022;15(9):e007960. doi:10.1161/CIRCEP.121.007960Yetkin E, Ozturk S, Cuglan B, Turhan H.Clinical presentation of paroxysmal supraventricular tachycardia: evaluation of usual and unusual symptoms.Cardiovasc Endocrinol Metab. 2020;9(4):153-158. doi:10.1097/XCE.0000000000000208Cronin EM, Bogun FM, Maury P, et al.2019 HRS/EHRA/APHRS/LAHRS expert consensus statement on catheter ablation of ventricular arrhythmias.Heart Rhythm.2020;17(1):e2-e154. doi:10.1016/j.hrthm.2019.03.002Armstrong GP.Mitral regurgitation. Merck Manual Professional Version.American Heart Association.Heart failure signs and symptoms.Fang JC, Ewald GA, Allen LA, et al.Advanced (stage D) heart failure: a statement from the Heart Failure Society of America Guidelines Committee.J Card Fail.2015;21(6):519-34. doi:10.1016/j.cardfail.2015.04.013Fujiyoshi K, Yamaoka-Tojo M, Fujiyoshi K, et al.Beat-to-beat alterations of acoustic intensity and frequency at the maximum power of heart sounds are associated with NT-proBNP levels.Front Cardiovasc Med. 2024;11:1372543. doi:10.3389/fcvm.2024.1372543National Heart, Lung, and Blood Institute.Heart treatments.Meyer TE.Patient education: mitral regurgitation (Beyond the Basics). In: UpToDate, Otto CM (Ed), Wolters KluwerColucci WS.Patient education: heart failure education (Beyond the Basics). In: UpToDate, Gottlieb SS (Ed), Wolters KluwerMeyer TE.Auscultation of heart sounds. In: UpToDate, Gersch BJ, (Ed), Wolters KluwerGupta JI, Shea MJ.Cardiac auscultation. Merck Manual Professional Version.
Armstrong GP.Mitral stenosis. Merck Manual Professional Version.
American Heart Association.Tachycardia: fast heart rate.
Mayuga KA, Fedorowski A, Ricci F, et al.Sinus tachycardia: a multidisciplinary expert focused review.Circ Arrhythm Electrophysiol. 2022;15(9):e007960. doi:10.1161/CIRCEP.121.007960
Yetkin E, Ozturk S, Cuglan B, Turhan H.Clinical presentation of paroxysmal supraventricular tachycardia: evaluation of usual and unusual symptoms.Cardiovasc Endocrinol Metab. 2020;9(4):153-158. doi:10.1097/XCE.0000000000000208
Cronin EM, Bogun FM, Maury P, et al.2019 HRS/EHRA/APHRS/LAHRS expert consensus statement on catheter ablation of ventricular arrhythmias.Heart Rhythm.2020;17(1):e2-e154. doi:10.1016/j.hrthm.2019.03.002
Armstrong GP.Mitral regurgitation. Merck Manual Professional Version.
American Heart Association.Heart failure signs and symptoms.
Fang JC, Ewald GA, Allen LA, et al.Advanced (stage D) heart failure: a statement from the Heart Failure Society of America Guidelines Committee.J Card Fail.2015;21(6):519-34. doi:10.1016/j.cardfail.2015.04.013
Fujiyoshi K, Yamaoka-Tojo M, Fujiyoshi K, et al.Beat-to-beat alterations of acoustic intensity and frequency at the maximum power of heart sounds are associated with NT-proBNP levels.Front Cardiovasc Med. 2024;11:1372543. doi:10.3389/fcvm.2024.1372543
National Heart, Lung, and Blood Institute.Heart treatments.
Meyer TE.Patient education: mitral regurgitation (Beyond the Basics). In: UpToDate, Otto CM (Ed), Wolters Kluwer
Colucci WS.Patient education: heart failure education (Beyond the Basics). In: UpToDate, Gottlieb SS (Ed), Wolters Kluwer
Meyer TE.Auscultation of heart sounds. In: UpToDate, Gersch BJ, (Ed), Wolters Kluwer
Gupta JI, Shea MJ.Cardiac auscultation. Merck Manual Professional Version.
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