What Is Heart Murmur?
The heart, being a mechanical pump, is noisy. Normal heart sounds, the familiar two-part stroke sound of the heart “beat,” are due to the cardiac valves closing, easily heard in auscultation through a stethoscope.
There are two normal heart sounds, labeled S1 and S2, and extra heart sounds labeled S3 and S4. The clichéd “Lub-Dub” of the heartbeat heard through a stethoscope minimizes and understates the complexity of what actually is occurring.
The First Heart Sound
Designated S1, it represents the nearly simultaneous closure of the left and right atrioventricular valves (the mitral and tricuspid valves, respectively) and is created from reverberation within the blood as an effect of the sudden block of blood flow by the valves. Since it occurs first, it represents the beginning of atrial diastole and the initiation of ventricular systole. S1 is a confluence of two sounds, M1 and T1, i.e., mitral valve and tricuspid valve closure. The near simultaneity of M1 and T1 can separate in some heart blocks of conduction.
The Second Heart Sound
Designated S2, it represents the closure of the pulmonary and aortic valves and is created from reverberation within the blood as an effect of the sudden block of flow reversal. The S2 sounds–known as A2 and P2–take place at the end of ventricular systole and the beginning of ventricular diastole. With inspiration, the S2 sound A2 and P2 can separate, but a wide split indicates an arrhythmia.
- Systole takes place between S1 and S2
- Diastole takes place between S2 and the subsequent S1 of the next cycle
Other Sounds: S3 and S4–Ventricular Filling Sounds
S3 and S4 are low-frequency diastolic sounds that originate in the ventricles. S3 occurs at the beginning of diastole after S2, is lower in pitch than S1 or S2, is not of valvular origin, and is thought to be caused by the oscillation of blood back and forth between the walls of the ventricles initiated by blood rushing in from the atria. The S3 sound is indicative of increased volume of blood within the ventricle. An S3 is able to be distinguished as either left- or right-sided by whether or not it increases in intensity with inhalation or exhalation. A right-sided S3 will increase upon inhalation, and a left-sided S3 will increase with exhalation.
S4 occurs just after atrial contraction at the end of diastole and immediately before S1, and is caused by the result of blood being forced into a stiff or hypertrophic ventricle, so it indicates pathology such as hypertension, aortic stenosis, or cardiomyopathy. Gallops are abnormal S3 and S4 sounds, louder and higher pitched (sharper). S3 is the ventricular gallop and S4 is the atrial gallop sound.
Murmurs are extra sounds heard as distinct from the S1 and S2 and are described in relation to the timing associated with both heart sounds. They are the result of turbulence of flow of blood (the sound is called a bruit) and are useful in diagnosing the valvular diseases that create them.
- Systolic heart murmurs occur during systole: Between the S1 and S2 sounds
- Diastolic murmurs occur during diastole: Between the S2 and the next S1
Significance of Heart Murmurs
Since the flow through the heart should be smoothly repetitive, any structural abnormalities will add noise to the auscultation due to turbulence and valve disease. Heart murmurs, therefore, are important diagnostic clues for heart and valvular disease identification which steers further diagnostics and subsequent therapies.
How Are Heart Murmurs Diagnosed?
Since heart murmurs indicate abnormalities of flow, many of which are pathologic, the description of them is important in arriving at a diagnosis. They are described as to their:
- Intensity (scale of Grade I–softest, to Grade V–which can be heard without a stethoscope)
- Pitch (high or low frequency)
- Quality (using descriptive adjectives such as scratchy, rumbling, vibratory, etc.)
- Graduated loudness (the rise or fall of the volume)
- crescendo, decrescendo, crescendo – decrescendo, and/or plateaued
- Location (where on the chest it is best heard and does the sound radiate)
- Timing and duration (systolic–early systolic, midsystolic, late systolic, or holosystolic (present the entire systole); diastolic–early diastolic, mid-diastolic, or late diastolic)
Systolic Murmurs (Between S1 and S2)
A murmur that occurs during systole is consistent with the following diagnoses:
- Early systolic murmur: Mitral regurgitation, tricuspid regurgitation, or ventricular septal defect
- Midsystolic murmur: Innocent flow murmurs, which may come and go based on hydration as a physiologic systolic “ejection” murmur; midsystolic murmurs, however, are also associated with aortic valve stenosis, prosthetic aortic valves, or pulmonic outflow obstruction
- Late systolic murmur: Mitral valve prolapse, tricuspid valve prolapse, mitral regurgitation
- Holosystolic murmur: Mitral regurgitation, tricuspid regurgitation, and ventricular septal defect
Diastolic Murmurs (Between S2 and the Next S1)
- Early diastolic murmur: Aortic regurgitation, pulmonic regurgitation, and left descending coronary artery stenosis
- Mid-diastolic murmur: Mitral stenosis, prosthetic mitral valve, tricuspid stenosis, atrial myxoma (obstruction); alternately, may represent increased flow across the atrioventricular valve
- Late diastolic murmur: Mitral stenosis and tricuspid stenosis
It is said tongue-in-cheek that the most important diagnostic part of the stethoscope is the part between the ear pieces. As much a cliché as it is a truism, auscultation and deciphering of the timing and quality of murmurs, in experienced hands (ears), can raise suspicion of arteriovenous fistulas, aortic disease, and shunts through septal defects, in addition to all of the more frequently diagnosed abnormalities of cardiac structure, valvular properties, and dysfunction.
How to Manage a Heart Murmur?
In the management of pathology of the heart, the diagnosis drives the treatment. For this reason, the diagnostic advantages of careful auscultation of the heart lead to both increased accuracy of diagnosis but also prevent missteps in protocol that can impact morbidity and mortality.
Confirmation of Diagnosis as Part of the Treatment Protocol
Once a provisional diagnosis is made based on abnormal heart sounds, confirmation usually relies on functional assessment as it is related to the diagnosis. Since many heart murmurs indicate disease, it is first important to differentiate the pathologic from the normal physiological (“flow”) murmurs. This requires adjunctive diagnostics:
- Examiner experience and expertise
- Electrocardiography (ECG): Used to correlate the sounds produced as murmurs with the electrical conduction sequence of the heart rate and rhythm.
- Chest X-ray: Identifies enlargement of the heart/ventricle(s) consistent with heart failure and valvular disease; it can also diagnose fluid shifts in the pulmonary system, such as pulmonary edema, lung congestion, and pleural effusions.
- Echocardiography: Cardiac ultrasonography can render visual information of structure (B mode ultrasound) and flow dynamics (functional flow via Doppler technology). The B mode is also useful in valve disease and in identifying the “vegetations” of endocarditis. The structural information gleaned from imaging can be used to assign physiologic relevance to the murmurs that are heard.
Therapy for Conditions Associated with Heart Murmurs
Therapy depends on the specific abnormality. Flow disturbances across the heart valves and through the chambers of the heart are treated according to site, severity of symptoms, and risks of morbidity and mortality. Stenosis, damage, or deterioration of a heart valve if mild and asymptomatic can be followed conservatively, but symptomatic patients can benefit from antiarrhythmics when indicated, anticoagulation therapy if there are thrombogenic conditions, and surgical repair (“commissurotomy”) or replacement (prosthetic valves). The decision for each of these is based on whether the mortality rate is lower for expectant therapy (mere observation) or for the specific invasive intervention.
Prevention of Heart Murmur
Semantically, prevention of heart murmurs is not a legitimate medical goal, as the sense of what is meant should be described as,
“prevention of heart disease that results in the cardiac valvular disease that creates murmurs heard in auscultating the heart.”
As such, prevention is centered on the prevention of heart disease, specifically valvular disease and the conditions that cause it.
Rheumatic fever decreased significantly in incidence in industrialized nations it can be caused by acute rheumatic fever, which frequently goes undiagnosed. In the pathogenesis, the heart valves are colonized and damage to them is significant. Prompt diagnosis and antibiotic treatment for group A streptococcal infection (tonsils and pharynx), will prevent the more virulent outcome that rheumatic fever can cause.
Those with a history of rheumatic fever or rheumatic heart disease should be treated with continuous prophylactic antibiotics. Patients with previous history of valve damage, disease, repair, or replacement, should undergo a course of antibiotics prior to any planned invasive intervention, including dental procedures.
Drug Toxicity and Prevention of Valvular Heart Disease
Anorectic drugs such as fenfluramine/dexfenfluramine can be toxic to heart valves via destruction based on the altered serotonin biochemistry they cause phentermine is known to augment the pathogenic qualities of the former. Any patients who have been exposed to these agents should be evaluated thoroughly, and this includes auscultation of the heart for identifying any suspicious murmurs. If a murmur is found, echocardiography is an important, preventative next step in reducing mortality.
Prevention Associated with Renal Dialysis
Aortic stenosis associated with the advanced calcification seen in renal failure patients should prompt annual or semiannual echocardiography.
Pre-Existing Valvular Heart Disease
For those for whom a diagnosis of valvular heart disease is already established, prevention of further morbidity or possible mortality from sudden cardiac death must include surveillance for arrhythmias that are more likely with malfunctioning valves. Specifically, atrial fibrillation can deteriorate further into deadly cardiac dysfunction as cardiac output falls; or it can present the threat of thromboembolism requiring anticoagulant therapy to prevent stroke, myocardial ischemia, or other obstructive ischemia and tissue death.