Lower Left Sternal Border Auscultation: Heart Sounds, Murmurs & Clinical Assessment
It’s late in a night shift, and you’re doing a cardiovascular reassessment. Along the lower left sternal border, you hear a soft systolic murmur. You listen again, this time asking the patient to take a slow, deep breath. The murmur becomes more prominent.That change gives you something to investigate. Right-sided heart murmurs often increase in intensity with inspiration, and the lower left sternal border is an important place to assess them. You may be hearing tricuspid regurgitation, although the location and respiratory response alone can’t establish the diagnosis.Most of us were introduced to this area as the tricuspid listening point, one of the traditional landmarks used during cardiac auscultation. It’s a useful starting point, but you can also hear several other important findings here, including ventricular septal defects, obstructive hypertrophic cardiomyopathy, and some innocent childhood murmurs.Our guide to cardiac auscultation landmarks covers the basic listening areas. Here, we’ll focus on the lower left sternal border, the anatomy beneath it, the murmurs you might encounter, and the bedside techniques that help distinguish one finding from another.
Where Is the Lower Left Sternal Border?
The lower left sternal border (LLSB) runs along the left edge of the sternum, generally at the fourth and fifth intercostal spaces.To find it, start at the sternal angle, the palpable ridge where the manubrium joins the body of the sternum. The second rib attaches at this level. Identify the second intercostal space just below that rib, then continue counting downward until you reach the fourth and fifth spaces.Keep your stethoscope close to the left edge of the sternum.Erb’s point is traditionally located at the third left intercostal space, just above the LLSB. The cardiac apex is farther lateral, typically near the fifth intercostal space at the midclavicular line in adults.These landmarks are useful, but heart sounds don’t always stay within their boundaries. A murmur may radiate across several listening areas, and the point of greatest intensity can vary with anatomy, body position, and the underlying condition.
[Illustration 1: Anterior chest diagram identifying the fourth and fifth left intercostal spaces, Erb’s point, and cardiac apex.]
Why Is the Lower Left Sternal Border Important?
To understand why this location matters, consider how the heart sits in the chest.The right ventricle forms much of the heart’s anterior surface and lies immediately behind the sternum. The tricuspid valve sits between the right atrium and right ventricle, while the interventricular septum separates the two ventricles.Heart sounds and murmurs come from vibrations caused by cardiac movement and blood flow. These vibrations travel through surrounding tissues, which helps explain why sounds from different structures can be heard over the same part of the chest.The tricuspid valve is most commonly associated with the LLSB, particularly when evaluating regurgitation or stenosis. However, turbulent flow through a ventricular septal defect can also produce a prominent murmur here.Obstruction within the left ventricular outflow tract, as occurs in some patients with hypertrophic cardiomyopathy, may produce another characteristic systolic murmur along the lower sternal border.Normal heart sounds also provide useful information. The first heart sound, S1, consists primarily of vibrations associated with closure of the mitral and tricuspid valves. These components are usually heard together, although a slight separation may occasionally be appreciated near the lower sternal border (Walker et al., 1990).Understanding what is normal for a particular patient makes it easier to recognize additional sounds or changes during subsequent assessments.
[Illustration 2: Anterior view of the heart showing the right ventricle, tricuspid valve, interventricular septum, and their relationships to the sternum.]
How to Auscultate the Lower Left Sternal Border
Before reaching for the stethoscope, take a moment to examine the precordium.With the patient positioned comfortably, inspect and palpate along the lower sternal border. A sustained parasternal lift may suggest right ventricular enlargement or increased right ventricular workload. A palpable vibration, or thrill, indicates a murmur strong enough to feel through the chest wall and warrants further evaluation. It's the medical equivalent of placing your hand on a subwoofer and feeling the vibration. For auscultation, begin with the patient supine or partially upright. Expose the area appropriately while maintaining privacy, and reduce background noise whenever possible.Start with the diaphragm of your stethoscope, which is well suited for higher-frequency sounds, including many regurgitant and ventricular septal defect murmurs.The bell, applied lightly, is useful for lower-frequency sounds such as the diastolic rumble of tricuspid stenosis. With a tunable diaphragm, you can adjust pressure against the chest to emphasize different frequency ranges without repeatedly repositioning the chestpiece.Listen through several cardiac cycles, paying attention to the relationship between the murmur and S1 and S2.If the timing is unclear, palpate the carotid pulse. The carotid upstroke occurs shortly after S1, providing a reference point for identifying systole.Next, listen during normal breathing and again during a slow inspiration. Some murmurs change considerably with respiration, while others remain relatively consistent.Finally, compare adjacent areas. Move toward Erb’s point, across to the apex, and, when indicated, below the xiphoid process.If you suspect right-sided pathology, also examine the jugular veins. In conditions such as significant tricuspid regurgitation, the venous pulse may provide important information even when the murmur is difficult to hear.When documenting a murmur, describe its timing, intensity, pitch, quality, location, radiation, and response to maneuvers. Those characteristics are considerably more informative than location alone.
Five Murmurs Heard at the Lower Left Sternal Border
Several conditions can produce murmurs in this region. These five are particularly useful to recognize because their mechanisms and examination findings differ.
1. Tricuspid Regurgitation
Tricuspid regurgitation occurs when the tricuspid valve fails to close adequately during ventricular contraction, allowing blood to flow backward from the right ventricle into the right atrium.The classic finding is a blowing, holosystolic murmur heard along the lower or middle left sternal border (O’Gara et al., 2025). Holosystolic means the murmur begins around S1 and continues through systole toward S2.One of its most useful distinguishing features is increased intensity during inspiration, known as Carvallo’s sign, first described by Rivero-Carvallo in 1946.During spontaneous inspiration, intrathoracic pressure decreases, and venous return to the right heart generally increases. The resulting increase in right-sided blood flow can make tricuspid regurgitation more audible.Tricuspid regurgitation frequently develops secondary to other cardiovascular conditions. Right ventricular dilation, pulmonary hypertension, atrial fibrillation, and leads from implanted cardiac devices are among the recognized contributors. Clinically significant tricuspid regurgitation may produce very little audible murmur.The American College of Cardiology’s expert consensus on tricuspid regurgitation emphasizes the importance of examining the jugular venous pulse. In severe disease, prominent systolic c-v waves may be more apparent than the murmur itself. Other findings can include peripheral edema, hepatomegaly, and hepatic pulsations (O’Gara et al., 2025).Carvallo’s sign can also be absent. When right atrial pressure is markedly elevated, inspiration may produce little additional right ventricular filling, limiting the expected change in murmur intensity.This is why you should consider the respiratory response alongside the rest of the examination. A murmur that increases with inspiration supports tricuspid regurgitation, but its absence doesn’t exclude it.
2. Ventricular Septal Defect
A ventricular septal defect (VSD) is an opening in the interventricular septum that allows blood to flow between the ventricles.In a typical restrictive VSD with a left-to-right shunt, blood moves from the higher-pressure left ventricle into the right ventricle during systole.This often produces a harsh holosystolic murmur, most prominent at the lower left sternal border. Strong vibrations may also create a palpable thrill.One of the more interesting aspects of VSD auscultation is the relationship between defect size and murmur intensity.As always, understand the patient population you are working with. A VSD is the most common congenital heart defect but is more likely to be found in pediatrics than adult medicine. A relatively small restrictive defect can produce a loud murmur because the pressure difference between the ventricles drives high-velocity flow through a narrow opening. A larger, nonrestrictive defect may allow ventricular pressures to become more similar, potentially producing a softer murmur despite greater hemodynamic consequences (Penny & Vick, 2011).There are exceptions. Very small defects can produce short or relatively quiet murmurs, and intensity also depends on pulmonary vascular resistance and the amount of blood crossing the defect.In infants with large defects, symptoms may become more apparent as pulmonary vascular resistance falls during the first weeks of life. Tachypnea, difficulty feeding, diaphoresis during feeds, and poor weight gain are particularly important findings.Auscultation provides clues about the underlying physiology, but murmur intensity should never be used alone to estimate the size or severity of a ventricular septal defect.
3. Obstructive Hypertrophic Cardiomyopathy
Hypertrophic cardiomyopathy (HCM) involves abnormal thickening of the heart muscle that cannot be explained solely by conditions such as hypertension or valvular disease.In some patients, a thickened interventricular septum and mitral valve movement during systole create dynamic obstruction of the left ventricular outflow tract.This obstructive form of HCM can produce a harsh, crescendo-decrescendo systolic murmur along the lower left sternal border, sometimes extending toward the apex.Its response to changes in ventricular filling is particularly useful during the physical examination.When left ventricular volume decreases, the obstruction may become more pronounced and the murmur louder. This explains why standing suddenly or performing the strain phase of a Valsalva maneuver can accentuate the finding.Increasing ventricular filling, as occurs with squatting or passive leg elevation, generally reduces the obstruction and may soften the murmur.These changes are worth assessing in a patient with exertional chest discomfort, syncope, dyspnea, or a family history of HCM or sudden cardiac death.For a young athlete who experiences syncope during exercise, an examination suggestive of HCM deserves prompt attention. The 2024 AHA/ACC multisociety guideline includes physical examination as part of the initial evaluation, with cardiac imaging used to establish the diagnosis and characterize the disease (Ommen et al., 2024).
4. Tricuspid Stenosis
Tricuspid stenosis occurs when the tricuspid valve opening narrows, restricting blood flow from the right atrium to the right ventricle during diastole.It is considerably less common than tricuspid regurgitation and is traditionally associated with rheumatic heart disease, often alongside other valvular abnormalities (Otto et al., 2021).The characteristic murmur is a low-pitched diastolic rumble heard near the lower left sternal border.Because this sound is low frequency, the bell or very light diaphragm pressure may improve detection.Like tricuspid regurgitation, the murmur of tricuspid stenosis often becomes more prominent with inspiration as right-sided blood flow increases.The examination becomes more challenging when mitral stenosis is also present, since both conditions produce diastolic murmurs. Location, associated findings, and respiratory response may help distinguish them.Evidence of systemic venous congestion, including elevated jugular venous pressure and peripheral edema, can provide additional clues.Although tricuspid stenosis is uncommon, it’s important to consider it when a diastolic sound is heard along the lower sternal border.
5. Still’s Murmur
Not every murmur heard at the lower left sternal border represents structural heart disease.Still’s murmur is one of the most common innocent murmurs in childhood, particularly in preschool- and school-aged children.It’s generally described as a short, low-pitched, musical or vibratory systolic murmur, commonly heard along the mid-to-lower left sternal border or between the sternum and apex (Ford et al., 2022).The characteristic twanging or vibrating quality can become familiar with experience.Still’s murmurs may be more noticeable when a child is lying down or when cardiac output increases, such as during fever or excitement. They often soften when the child sits or stands.In an otherwise healthy older child with normal heart sounds and no concerning symptoms, a classic Still’s murmur can be reassuring.Do not apply the same assumptions to newborns or symptomatic children. Neonatal murmurs are more likely to reflect underlying cardiac pathology than murmurs in older children, and their characteristics can be harder to interpret.Findings such as a thrill, diastolic component, harsh holosystolic quality, abnormal S2, or symptoms including feeding intolerance deserve further evaluation. Recognizing a typical innocent murmur can be just as useful as identifying an abnormal one, provided the entire clinical picture supports that interpretation.
Another Murmur to Remember: Aortic Regurgitation
Clinicians traditionally assess aortic regurgitation near Erb’s point and along the left sternal border, but its high-pitched, early diastolic decrescendo murmur may also be audible around the fourth left intercostal space. We'll do a deep dive on Erb’s point in an upcoming article, so this is a brief synopsis.If you suspect a diastolic murmur here, ask the patient to sit upright and lean slightly forward, when tolerated, and listen during end-expiration.We introduce that technique in the Erb’s point section of our auscultation landmarks guide.It’s a useful example of why you should examine neighboring listening areas rather than relying entirely on where a murmur was first detected.
Dynamic Auscultation: What Changes With Bedside Maneuvers?
Bedside maneuvers can provide additional information about a murmur by changing the conditions under which blood moves through the heart.Two key concepts are preload, which describes ventricular filling, and afterload, which describes the resistance the ventricle must overcome during ejection.Changes in these conditions can predictably affect murmur intensity.Inspiration generally increases systemic venous return to the right heart during spontaneous breathing. Murmurs associated with tricuspid regurgitation and tricuspid stenosis may become louder as right-sided flow increases.Valsalva strain decreases venous return and ventricular filling after its initial phase. Many murmurs soften, while dynamic left ventricular outflow obstruction in HCM may intensify as the ventricular cavity shrinks.Standing from a squatting position also reduces venous return and may accentuate the obstructive HCM murmur.Squatting or passive leg elevation increases ventricular filling. These maneuvers generally reduce dynamic outflow obstruction and may soften the associated HCM murmur.Sustained handgrip increases systemic vascular resistance (afterload). This may intensify murmurs associated with mitral regurgitation and VSD while reducing the murmur of obstructive HCM.Clinical studies have evaluated these responses.In 1988, Lembo and colleagues studied bedside maneuvers in 50 patients with documented systolic murmurs. Inspiratory augmentation distinguished right-sided murmurs with 100% sensitivity and 88% specificity. Increased murmur intensity during Valsalva showed 65% sensitivity and 96% specificity for hypertrophic cardiomyopathy.The findings illustrate the diagnostic value of dynamic examination, although the study was relatively small and involved experienced examiners under controlled conditions.Performance in everyday clinical practice may differ.Patient cooperation, respiratory effort, body position, and underlying hemodynamics all influence the results. Positive-pressure ventilation also changes normal respiratory physiology, so clinicians should not automatically apply typical inspiratory responses to mechanically ventilated patients.These maneuvers are most useful when they help refine a differential diagnosis already informed by the patient’s history and examination.
Lower Left Sternal Border Findings in Children and Adults
The patient’s age can substantially change how we interpret a murmur.In older children, innocent murmurs are common, and an otherwise normal physical examination may reveal a characteristic Still’s murmur.A harsh holosystolic murmur, however, raises different concerns, particularly when accompanied by a thrill, abnormal heart sounds, or symptoms (Ford et al., 2022).Infants require additional attention because significant congenital cardiac defects may become apparent during the first weeks of life. Respiratory distress, poor feeding, inadequate weight gain, and diaphoresis during feeds all deserve careful assessment.In adults, evaluate a new murmur in the context of symptoms, medical history, and cardiovascular risk factors.A holosystolic murmur in a patient with pulmonary hypertension, right ventricular dilation, atrial fibrillation, or an implanted cardiac device may suggest tricuspid regurgitation.A systolic murmur that changes substantially with ventricular filling, especially in someone experiencing exertional symptoms, may raise concern for obstructive HCM.Fever and other signs of systemic infection are also important when evaluating a new murmur, since infective endocarditis can involve the tricuspid valve.The listening location may be the same, but the differential diagnosis can differ widely depending on the patient.
Quick Reference: Murmurs at the Lower Left Sternal Border
| Condition | Timing | Characteristic finding | Useful assessment |
| Tricuspid regurgitation | Holosystolic | Blowing, often louder with inspiration | Jugular venous pulse and signs of congestion |
| Ventricular septal defect | Usually holosystolic | Harsh, sometimes with a thrill | Symptoms and shunt physiology |
| Obstructive HCM | Systolic ejection | Crescendo-decrescendo, often louder with Valsalva | Standing, squatting, family history, exertional symptoms |
| Tricuspid stenosis | Diastolic | Low-pitched rumble, often louder with inspiration | Bell or light pressure, signs of venous congestion |
| Still’s murmur | Early to midsystolic | Musical or vibratory, often softer with standing | Age, symptoms, and complete examination |
[Illustration 3: Cardiac cycle diagram comparing holosystolic, systolic ejection, and diastolic murmurs.]
When Is Further Evaluation Needed?
Auscultation remains an important part of the cardiovascular examination, but it has limitations.A loud murmur doesn’t necessarily indicate severe disease, and significant structural abnormalities can sometimes produce relatively quiet findings.Echocardiography allows clinicians to evaluate cardiac anatomy, valve function, ventricular dimensions, and blood flow. It plays a central role in assessing suspected valvular disease, congenital defects, and cardiomyopathy (Otto et al., 2021).Diastolic murmurs, suspicious holosystolic murmurs, loud or harsh murmurs, abnormal heart sounds, and associated symptoms generally warrant additional evaluation.In older children with a classic innocent murmur and a reassuring history and examination, routine echocardiography may not be necessary. Newborns with murmurs and patients with findings suggestive of structural disease require a more cautious approach (Ford et al., 2022).The decision to pursue imaging or specialist evaluation depends on the overall clinical presentation, rather than any single auscultatory characteristic.
Listen Beyond the Landmark
The lower left sternal border is an important part of a systematic cardiovascular examination, particularly when assessing the tricuspid valve and conditions affecting the ventricular septum or outflow tract.When you encounter an unfamiliar sound, start with its timing and location. Then consider its pitch, intensity, and response to respiration. Compare neighboring auscultation areas, look for a parasternal lift, assess the jugular veins, and consider the patient’s symptoms and history.With practice, these observations become a natural part of the examination.We may have learned the lower left sternal border as one of several landmarks to memorize, but understanding what we hear there requires a little more thought. The goal is to recognize findings that warrant further attention and understand the physiology that explains them.
References
- O’Gara PT, Lindenfeld J, Hahn RT, et al. 10 issues for the clinician in tricuspid regurgitation evaluation and management: 2025 ACC expert consensus decision pathway. Journal of the American College of Cardiology. Published online September 22, 2025. 2026;87(4):447–486. doi:10.1016/j.jacc.2025.07.002.
- Ford B, Lara S, Park J. Heart murmurs in children: evaluation and management. American Family Physician. 2022;105(3):250–261. Read article.
- Lembo NJ, Dell’Italia LJ, Crawford MH, O’Rourke RA. Bedside diagnosis of systolic murmurs. New England Journal of Medicine. 1988;318(24):1572–1578. doi:10.1056/NEJM198806163182404.
- Ommen SR, Ho CY, Asif IM, et al. 2024 AHA/ACC/AMSSM/HRS/PACES/SCMR guideline for the management of hypertrophic cardiomyopathy. Circulation. 2024;149(23):e1239–e1311.
- Otto CM, Nishimura RA, Bonow RO, et al. 2020 ACC/AHA guideline for the management of patients with valvular heart disease. Circulation. 2021;143(5):e72–e227.
- Penny DJ, Vick GW III. Ventricular septal defect. The Lancet. 2011;377(9771):1103–1112.
- Rivero-Carvallo JM. Signo para el diagnóstico de las insuficiencias tricuspídeas. Archivos del Instituto de Cardiología de México. 1946;16:531.
- Walker HK, Hall WD, Hurst JW, editors. Clinical Methods: The History, Physical, and Laboratory Examinations. 3rd ed. Boston: Butterworths; 1990.
- Merck Manual Professional Edition. Tricuspid Regurgitation.
Frequently Asked Questions
Which heart valve is heard at the lower left sternal border?The tricuspid valve is traditionally associated with this listening area. However, murmurs from ventricular septal defects, obstructive hypertrophic cardiomyopathy, and other conditions may also be heard here.What’s the difference between the lower left sternal border and Erb’s point?Erb’s point is traditionally located at the third left intercostal space, while the lower left sternal border generally refers to the fourth and fifth left intercostal spaces. Sounds may overlap between these neighboring locations.Why do right-sided murmurs get louder with inspiration?During spontaneous inspiration, intrathoracic pressure decreases, and systemic venous return to the right heart generally increases. The resulting increase in right-sided blood flow can make certain murmurs, particularly tricuspid regurgitation and stenosis, more prominent.Can a healthy child have a murmur at the lower left sternal border?Yes. Still’s murmur is a common innocent childhood murmur that may be heard in this region. Its interpretation depends on the child’s age, the murmur's characteristics, associated symptoms, and the rest of the examination.
