Who Heard It: A Murmur Mystery

Column Author: Zoetta McLoughlin, MD | Pediatric Resident

Column Editor: Kathleen Berg, MD, FAAP | Hospitalist - Pediatrics; Associate Professor of Pediatrics, University of Missouri-Kansas City School of Medicine; Clinical Assistant Professor of Pediatrics, University of Kansas School of Medicine

A new murmur, especially if harsh, might understandably set a physician’s own heart racing. An estimated 50%-80% of children will have a cardiac murmur at some point in their life, but less than 1% of these murmurs will correlate with serious congenital or acquired heart disease,^1,2 making identifying a pathologic murmur akin to finding a needle in a haystack. Here, we highlight the characteristics of heart murmurs, including timing, intensity, location and variability that should appropriately raise concern and prompt further evaluation, compared to those that can be observed. 

Normal heart sounds are caused by closure of four main valves in response to flow and pressure changes in the heart throughout the cardiac cycle. The first heart sound, S1, should be heard at the beginning of systole and is caused by closure of the tricuspid and mitral valves. S2, occurring at the end of systole, is caused by the closure of the pulmonary and aortic valves. Timing of a murmur is the first important characteristic to consider. An S1 co-incident murmur starts at the onset of systole and may blur S1. These and pansystolic murmurs raise concern for a pathology, such as a ventricular septal defect. Most continuous murmurs and all diastolic murmurs should be further evaluated.³

Next, we evaluate the intensity of a murmur, keeping in mind that the intensity of a murmur does not always correlate with severity of a condition. A grading scale of one to six is most common, with grade 1: barely audible, grade 2: easily audible but soft, grade 3: moderately loud without a thrill, grade 4: moderately loud with a thrill, grade 5: loud with a thrill, grade 6: loud with a thrill and heard with a stethoscope off the chest.⁴ Most pathologic murmurs are found to be greater than grade 3, and thus should be further evaluated. The quality of a murmur should also be considered, with harsh or blowing murmurs more worrisome, and “sweet” or “musical” murmurs less likely to indicate pathology.

The location of most prominent auscultation as well as radiation of a murmur can also be helpful in evaluation. Recall the main auscultation regions on the chest – with the aortic valve best heard at the right upper sternal border, the pulmonary valve at the left upper sternal border, the tricuspid valve at the left lower sternal border, and mitral valve at the apex. Location of maximum murmur intensity may help determine which anatomic component is affected, but murmurs that radiate throughout the precordium should be further evaluated.

Lastly, we decide if a murmur is variable in different positions or with special maneuvers. A murmur that intensifies with standing should be referred, while a murmur that gets louder in the supine position as venous return to the heart increases may indicate an innocent Still’s murmur.¹

As a key summary, use this handy tool to remember the characteristics that an innocent murmur should satisfy (adapted from Current Pediatric Reviews).¹ 

Seven S’s: An innocent murmur should be Systolic, Soft (< Grade 3), Small (not radiating), Short (not holosystolic), Single (no other associated sounds), Sweet (not harsh), and Sensitive (changes with position).

Most murmurs referred to pediatric cardiologists for further evaluation are innocent, indicating that much of the parental anxiety surrounding these visits was preventable.⁵ In a study reporting the prevalence of significant cardiac pathology in patients 2-18 years of age referred to cardiology for a murmur, 33/473 (7%) were diagnosed with cardiac pathology. Interestingly, 9.5% of those referred for a new murmur were found to have no murmur at the time of their cardiology visit.⁶ For asymptomatic children found to have new murmurs with innocent features, conservative management with observation alone should be considered. This approach may help mitigate excess resource use and parental anxiety. Of course, any child with a murmur and associated concerning signs or symptoms such as poor growth, tachypnea or exercise intolerance should also undergo further evaluation and referral. Remember the Seven S’s and find the needle in the haystack!  

References:

1. Kostopoulou E, Dimitriou G, Karatza A. Cardiac murmurs in children: a challenge for the primary care physician. Curr Pediatr Rev. 2019;15(3):131-138. doi:10.2174/1573396315666190321105536 
2. Ford B, Lara S, Park J. Heart murmurs in children: evaluation and management. Am Fam Physician. 2022;105(3):250-261. 
3. Gonzalez VJ, Kyle WB, Allen HD. Cardiac examination and evaluation of murmurs. Pediatr Rev. 2021;42(7):375-382. doi:10.1542/pir.2020-000604 
4. Kamat DM. Heart murmurs. Quick References 2020. doi:10.1542/aap.ppcqr.396079 
5. Ip FHL, Hay M, Menahem S. Impact of echocardiography on parental anxiety in children with innocent murmurs. J Paediatr Child Health. 2020;56(6):917-921. doi:10.1111/jpc.14775 
6. Gupta LJ, May JW. Managing a “new” murmur in healthy children and teens. Clin Pediatr (Phila). 2017;56(4):357-362. doi:10.1177/0009922816656623