Notes
Heart Murmurs (Stenosis & Regurgitation)
Sections
Heart Murmurs
Overview:
Review Heart Anatomy
In present times, echocardiography is used to visualize the valvular disease but auscultation of a murmur is a quick, important way to identify whether pathology is present.
Heart murmurs are abnormal sounds created by turbulent blood flow across defective cardiac valves.
Key causes of valvular damage:
Endocarditis, an infection of the endocardium (inner heart lining) commonly affects the valvular leaflets and causes murmur.
Calcification deposits on the valve leaflets create an audible murmur.
Rheumatic fever, which is an autoimmune disease (typically associated with Group A streptococcal infection) affects the leaflets and causes murmur.
Congenital defects of the valves can also be heard on heart auscultation.
Pressure Graphs:
Pressure graphs illustrate changes in aortic, left ventricular, and left atrial pressures during a cardiac cycle; if you are unfamiliar with these graphs, you may want to review our tutorial on the Wigger's diagram.
Normal blood flow and pressures in the left side of the heart:
– The left atrium is characterized by low blood pressure, approximately 10 mmHg; this allows passive blood flow to the ventricle.
– Blood pressure in the left ventricle is 120 mmHg during systole, 10 during diastole.
– Aortic pressure is 120/80. Notice that aortic and ventricular pressures during systole are the same.
Valvular insufficiency, aka, regurgitation
Valvular insufficiency occurs when the valve doesn't completely seal and allows blood to flow "backwards" across the valve; for example, regurgitation occurs when scarring of the valve leaflets prevents closure.
Mitral valve regurgitation
Mitral valve regurgitation produces a murmur during systole.
Be aware that tricuspid valve regurgitation produces the similar effects on the right side of the heart, and that ventricular septal defects produce similar holosystolic heart murmurs.
Anatomical and physiological effects of mitral valve regurgitation:
During ventricular contraction, the faulty mitral valve allows blood to "backflow" from the ventricle to the atria, increasing both atrial blood volume and pressure.
In chronic conditions, the left atrium responds by dilating to increase its compliance to mitigate the increase in pressure.
The blood that was pushed into the atrium combines with blood returning from the pulmonary circulation.
Thus, a greater volume of blood drains to the ventricle during diastole, increasing its preload; like the atrium, the ventricle accommodates by dilating.
Because only a portion of the stroke volume enters the aorta, aortic pressure is decreased.
In graphical form:
Mitral valve regurgitation raises left atrial pressure, most notably during ventricular systole, and is indicated by the higher v-wave; high left atrial pressure can lead to pulmonary congestion and edema.
Aortic pressure is reduced.
Left ventricular pressure is elevated during diastole.
Phonocardiogram:
Characterized by a high-pitched holosystolic murmur that lasts from S1 to S2.
Aortic valve regurgitation
Aortic valve regurgitation produces a murmur during ventricular diastole.
Anatomical and physiological effects:
Faulty aortic valve allows "backflow" of blood to the left ventricle.
Because only a portion of blood remains in the aorta, its diastolic pressure falls.
The blood that "backflows" into the ventricle combines with blood from the atria, increasing ventricular preload.
Thus, stroke volume and systolic aortic pressures increase.
Furthermore, increased ventricular filling and pressure causes blood to "back up" and raise pressure in the left atrium and pulmonary veins.
As in mitral valve insufficiency, chronic overload leads to atrial and ventricular dilation to increase compliance and mitigate pressure changes.
In graphical form:
Atrial and ventricular pressures increase.
Systolic aortic pressure is increased, but diastolic pressure is reduced (and, therefore, aortic pulse pressure is increased).
Phonocardiogram:
Characterized by high-pitched murmur is heard after S2.
Clinical Correlation:
Aortic valve insufficiency can lead to heart failure, and is characterized clinically by "head bobbing," aka, Corrigan's Sign, aka, dancing carotids, in which carotid pulsation is easily visible in the neck.
Valvular Stenosis
Stenosis occurs when a narrowed valve opening causes an elevated pressure gradient across valve, resulting in increased blood flow velocity, and, therefore, turbulence.
For example, calcification causes hardening and thickening of the valves, preventing their opening.
Mitral Valve Stenosis
Produces a murmur during diastole.
Anatomical and physiological effects:
Stiffened mitral valve raises the pressure gradient between the atrium and ventricle and creates blood flow turbulence.
To effectively move blood into the ventricle across the valve, the atrial muscle must generate additional force; it hypertrophies to meet this demand, and pressure is increased.
The opposite occurs in the ventricle, where filling and pressure are reduced.
Consequently, stroke volume, aortic pressure, and, in the absence of compensatory mechanisms, cardiac output, are reduced.
In graphical form:
Ventricular and aortic pressure are reduced.
Left atrial pressure is increased
We shade the area between the atrial and ventricular pressure curves to highlight the unusually high pressure gradient between them.
Phonocardiogram:
The weak diastolic murmur occurs after the opening snap; notice that this delay after S2 distinguishes the diastolic murmur of mitral valve stenosis from that of aortic valve regurgitation.
Aortic Valve Stenosis
Produces a loud, harsh murmur during systole.
Stiffened aortic valve obstructs blood flow into the aorta, creating turbulence and low aortic pressure.
The left ventricle hypertrophies to meet the demand for increased pressure generation, which can reach as high as 300 mmHg.
As a result of increased ventricular pressure, atrial pressure may also increase; in turn, the atrium will need to generate additional contractile force, so it, too, hypertrophies.
In graphical form:
Pressure in both chambers is elevated.
Aortic pressure is drastically reduced during systole, which increases the pressure gradient between the aorta and the left ventricle.
Phonocardiogram:
Very loud systolic murmur with a crescendo-decrescendo pattern. Notice that this differentiates it from the murmur heard in mitral valve regurgitation, which is steadier.
Systolic vs. Diastolic murmurs
Systolic murmurs are present with mitral valve regurgitation and aortic valve stenosis.
Diastolic murmurs are present with mitral valve stenosis and aortic valve regurgitation.
Be aware that patent ductus arteriosus, a congenital disorder, produces a continuous murmur that gets loudest at S2.
Clinical Correlation: Atrial Hypertrophy
Complications of valvular lesions
Heart failure and pulmonary edema; enlargement of the atria can cause atrial fibrillation when cardiac electrical signals have to travel increased distances through the atrial wall.
Clinical Cases
Case 1: Valvular Disease Presentation
A healthy 15-year-old female comes to your clinic today with her mother for evaluation of palpitations and shortness of breath. The patient plays basketball on her school team. Recently, she has become easily fatigued, and on a number of occasions complained of a "funny feeling" in her chest. Her symptoms are episodic, self-limiting, and appear to be associated with exercise. She denies any recent fevers or trauma. Her immunizations are up to date, she does not take any medications regularly, and has no history of chronic conditions.
On physical examination, she is 157 cm (5 ft 2 in), weighs 54 kg (120 lb), her blood pressure is 120/80 mm Hg, heart rate 60/min, respiratory rate 15/min, and oxygen saturation is 98 percent on room air. Lung auscultation demonstrates clear lung fields bilaterally with no wheezing. Cardiac examination reveals a mid-systolic click along with a high-pitch, holosystolic murmur, best heard at the apex, which is increased with valsalva.
Based on the information you have at this point, what is the most likely cause of this patient's symptoms?
Answer
- Mitral Valve Prolapse
Explanation
The patient in this clinical scenario has signs and symptoms consistent with mitral valve prolapse. The mitral valve is located between the left atrium and left ventricle. This condition occurs when the two leaflets of the mitral valve do not close evenly, and is thought to be caused by weakness in the valve tissue (myxomatous degeneration). Technically, mitral valve prolapse is defined as greater than 2 mm systolic displacement of one or both valve leaflets beyond the annulus into the left atrium.
Although often of unknown etiology (idiopathic), conditions commonly associated with the development of mitral valve prolapse include Ebstein anomaly, Ehlers-Danlos syndrome, Graves' disease, and Marfan syndrome. As in this clinical scenario, the typical murmur of mitral valve prolapse is a systolic murmur best heard at the apex of the heart and associated with a midsystolic "click", which is caused by the leaflets snapping against each other during contraction.
It should be noted that patients (specifically athletes) with severe mitral valve prolapse and significant mitral valve regurgitation have an increased risk for sudden cardiac death. Most cases are, however, mild and asymptomatic. This case highlights the importance of a thorough pre-participation history and physical evaluation for all adolescents prior to engaging in organized sports activities.
Board Review
Heart Murmurs
Getting ready for boards? Review these concise, bulleted high yield reviews for your exam.
USMLE & COMLEX-USA
Nurse Practitioner (NP)
Physician Assistant (PA)
Internal Medicine (ABIM)
References
- Jameson, J. Larry, ed. Harrison's Principles of Internal Medicine. Twentieth edition. New York: McGraw-Hill Education, 2018.
- Kumar, V, AK Abbas, JC Aster, and JA Perkins. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Philadelphia, PA: Elsevier Saunders, 2015.
- McPhee, Stephen J, Gary D Hammer, and Yeong Kwok. Pathophysiology of Disease: An Introduction to Clinical Medicine, 8e. New York, N.Y.: McGraw-Hill Education LLC., 2019. https://accessmedicine.mhmedical.com/cases.aspx?gboscontainerID=216.