Heart Sounds and Heart Murmurs

Heart Sounds and Heart Murmurs: Understanding the Basics

Heart sounds are the sounds made by the heart as it beats and pumps blood through the body. There are four heart sounds, S1, S2, S3, and S4, each of which has a unique sound and significance. Additionally, heart murmurs are unusual sounds heard during a heartbeat, which may indicate a problem with the heart. 

The Four-Heart Sounds

There are four heart sounds, S1, S2, S3, and S4, each of which has a unique sound and significance. 

S1 (First Heart Sound): S1 is the first heart sound, and it occurs as the heart's two lower chambers (ventricles) contract and closes, preventing blood from flowing back into them. S1 is a "lub" sound that is usually heard as a distinct "lub-dub."

S2 (Second Heart Sound): S2 is the second heart sound, and it occurs as the heart's two upper chambers (atria) relax and fill with blood. S2 is a "dub" sound and is usually heard as a distinct "lub-dub."

S3 (Third Heart Sound): S3 is an extra heart sound that occurs when the blood rushes into the ventricles during rapid filling. S3 is a low-pitched, rhythmic "thud" sound that may be heard during physical activity, in children or people with heart disease.

S4 (Fourth Heart Sound): S4 is an extra heart sound that occurs when the ventricles are stiff and do not relax properly. S4 is a low-pitched, rhythmic "thud" sound that may be heard in people with heart disease or heart failure.

Heart Murmurs

Heart Murmurs are extra or unusual sounds heard during a heartbeat, caused by the turbulent flow of blood through the heart or blood vessels. Murmurs are often harmless and may occur in healthy people, but they may also indicate a problem with the heart, such as a congenital heart defect, valvular heart disease, or endocarditis (inflammation of the inner lining of the heart).

Innocent Murmur Vs Pathological Murmurs (Abnormal Murmurs)

Innocent heart murmurs are harmless and do not require treatment. They are common in children and often disappear by adulthood. Abnormal heart murmurs, on the other hand, may be a sign of an underlying heart condition and require further evaluation and treatment.

Innocent Murmurs

Innocent murmurs are relatively common in children and are considered harmless. They are often referred to as functional or physiologic murmurs and are caused by the normal flow of blood through the heart. Innocent murmurs are typically soft, short, and heard best at the lower left sternal border. They can be heard during certain activities, such as exercise or when the child is upset or anxious, but disappear when the child is relaxed.

Innocent murmurs do not require any specific treatment or follow-up, but the child should still receive regular check-ups to monitor their heart health. In some cases, an echocardiogram may be performed to confirm that the murmur is innocent and not indicative of an underlying heart condition.

Pathological Murmurs (Abnormal Murmurs)

Pathological murmurs, also known as abnormal murmurs, are heart sounds that are heard during a physical exam and are not associated with normal blood flow. These murmurs may be a sign of an underlying heart condition, such as valve disease, congenital heart defects, or aortic aneurysm.

There are several characteristics that differentiate pathological murmurs from innocent murmurs. Pathological murmurs are often louder, longer, and have a different quality to their sound. They may also be accompanied by other symptoms, such as shortness of breath, chest pain, or fatigue.

Pathological murmurs are further classified into systolic and diastolic murmurs based on the timing of the murmur within the cardiac cycle. Systolic murmurs occur during the contraction of the heart, while diastolic murmurs occur during the relaxation of the heart. There is also holosystolic murmur which is a continuous murmur that lasts throughout the entire heart cycle.

Murmur Grading 

Heart murmurs are graded on a scale of 1 to 6, based on their loudness and other characteristics, such as their timing, shape, and location. The higher the grade, the more significant the murmur, and the more likely it is to indicate a problem with the heart.

Grade 1: Very faint murmur, barely audible

Grade 2: Faint murmur, easily audible

Grade 3: Moderately loud murmur, clearly audible

Grade 4: Loud murmur, heard with the stethoscope barely off the chest

Grade 5: Very loud murmur, heard with the stethoscope only lightly touching the chest

Grade 6: Extremely loud murmur, heard without the stethoscope

The grading of a murmur can provide important information about the underlying cause of the murmur and the potential for it to cause problems.

Pathological Heart Murmurs

Heart murmurs can be classified into different types based on their characteristics, such as timing, shape, and location. Here are the different types of heart murmurs and what they indicate:

A.) Systolic Murmurs 

A systolic murmur is a type of heart murmur that occurs during the contraction (systole) phase of the heart's pumping cycle. It is characterized by a swishing or whooshing sound that is heard between the first and second heart sounds, which correspond to the closing of the mitral and aortic valves, respectively.

Causes of Systolic Murmurs

Systolic murmurs can be caused by a range of conditions affecting the heart's structure or function. Valvular disorders such as aortic stenosis, where the aortic valve narrows and impedes blood flow from the left ventricle to the aorta, and mitral regurgitation, which occurs when the mitral valve fails to close properly, leading to backflow of blood into the left atrium, are common causes. Cardiomyopathies such as hypertrophic cardiomyopathy, characterized by thickening of the heart muscle and obstruction of blood flow, and dilated cardiomyopathy, which involves enlargement and weakened pumping ability of the heart chambers, can also result in systolic murmurs. 

Additionally, congenital heart defects like ventricular septal defect (a hole in the wall between the ventricles) and atrial septal defect (a hole in the wall between the atria) contribute to these murmurs. Other conditions like hyperthyroidism, which increases heart rate and blood flow, and anemia, which reduces the blood's oxygen-carrying capacity and leads to increased blood flow through the heart, can also be underlying causes.

Characteristics of Systolic Murmurs

Systolic murmurs, which occur during the systole phase of the cardiac cycle, possess certain characteristics that aid in their evaluation and diagnosis. These characteristics include:

1.) Timing: Systolic murmurs occur between the first heart sound (S1) and the second heart sound (S2). They can be further classified based on their timing within systole, such as early systolic, mid-systolic, or late systolic murmurs.

2.) Intensity: The intensity of systolic murmurs can vary, ranging from soft to loud. The loudness of the murmur can provide important information about the severity of the underlying condition.

3.) Pitch: Systolic murmurs can have different pitches, ranging from low to high. The pitch can sometimes be described as a musical or harsh sound. The specific pitch can provide insights into the nature of the murmur and its origin.

4.) Quality: The quality or character of the murmur can also vary. It can be described as a blowing, whooshing, or rumbling sound, depending on the underlying cause.

5.) Location: The location where systolic murmurs are best heard can indicate the specific valve or area of the heart that is affected. Common auscultatory sites include the apex, left sternal border, and right upper sternal border.

6.) Radiation: Systolic murmurs may radiate to other areas of the chest, neck, or back, depending on the underlying condition. This radiation pattern can provide additional diagnostic clues.

7.) Timing in the Cardiac Cycle: The timing of systolic murmurs within systole can be further categorized. For example, an early systolic murmur occurs shortly after S1, while a mid-systolic murmur reaches its peak intensity in the middle of systole. Late systolic murmurs occur closer to S2.

Types of Systolic Murmurs

There are several different types of systolic murmurs, each with its own unique characteristics and causes. Systolic murmurs are categorized based on their timing, intensity, pitch, location, and radiation. 

1.) Ejection Murmurs

 Ejection murmurs are a type of systolic heart murmur characterized by abnormal blood flow through the heart's semilunar valves (aortic and pulmonic valves) during the ejection phase of the cardiac cycle. These murmurs occur when blood is forced through narrowed or abnormal valve openings, resulting in turbulent flow and generating audible sounds. Ejection murmurs are typically heard during systole (the contraction phase of the heart) and are categorized by timing, intensity, pitch, location, and radiation. They are often described as harsh, crescendo-decrescendo murmurs. 

The two main types of Ejection murmurs include:

• Aortic Stenosis: Harsh, crescendo-decrescendo murmur heard best over the right upper sternal border, often radiating to the carotid arteries.

• Pulmonic Stenosis: Similar to aortic stenosis but heard best over the left upper sternal border and radiates to the neck.

2.) Regurgitant Murmurs

Another type of systolic murmur is known as a "regurgitant murmur," which occurs when blood leaks back through a valve that should be closed during systole. This can be caused by conditions such as mitral valve prolapse or aortic regurgitation and may be accompanied by other symptoms such as shortness of breath or chest pain.

• Mitral Regurgitation: Failure of the mitral valve to close properly, causing backflow of blood from the left ventricle into the left atrium. This murmur is characterized by a high-pitched, holosystolic (pansystolic) sound heard best at the apex and radiating to the axilla.

• Tricuspid Regurgitation: Backflow of blood from the right ventricle into the right atrium due to improper closure of the tricuspid valve. The murmur is described as a blowing, holosystolic sound heard best over the lower left sternal border.

3.) Flow Systolic Murmur

Another common type of systolic murmur is known as a "flow murmur," which occurs when blood flows through a normal, healthy heart valve faster than usual. A flow systolic murmur refers to an abnormal sound heard during the systolic phase of the cardiac cycle that is caused by turbulent blood flow through a normal or abnormal opening or vessel. Unlike ejection murmurs, flow murmurs do not arise from the semilunar valves (aortic and pulmonic valves) but rather from disturbances in blood flow within the heart chambers or major blood vessels.

Flow murmurs can occur due to various conditions or factors, including:

• Innocent Flow Murmur: Physiological murmurs heard in children and young adults during periods of increased blood flow, such as exercise or pregnancy. These murmurs are typically soft, benign, and not associated with any underlying heart abnormalities. They are usually harmless and don't require treatment.

• Pathological Flow Murmur: Abnormal flow murmurs caused by conditions such as valvular regurgitation, ventricular septal defect (VSD), or patent ductus arteriosus (PDA). The characteristics of these murmurs may vary depending on the underlying cause.

Flow murmurs are often described as soft, blowing, or whooshing sounds heard during systole. They may vary in intensity, pitch, and location depending on the underlying cause. It is important to differentiate between innocent flow murmurs and those associated with pathological conditions to guide appropriate diagnosis and treatment.

4.) Other Systolic Murmurs

These conditions can also cause systolic murmurs:

• Hypertrophic Obstructive Cardiomyopathy: Thickening of the heart muscle, leading to obstruction of blood flow from the left ventricle. The murmur is often heard during systole and is associated with a harsh, crescendo-decrescendo sound.

• Anemia: Reduced oxygen-carrying capacity of the blood, causing increased blood flow through the heart. This may result in a systolic murmur, which can vary in intensity and characteristics depending on the severity of the anemia.

It is important to note that the characteristics of a systolic murmur, including its intensity, location, and timing, can provide valuable information about the underlying condition and help guide diagnosis and treatment.

B.) Diastolic Murmurs 

Diastolic murmurs are abnormal heart sounds that occur during the relaxation phase (diastole) of the cardiac cycle. They result from turbulent blood flow within the heart or major blood vessels. Diastolic murmurs can provide important clues about underlying cardiac conditions and are a crucial aspect of the cardiovascular assessment.

Causes of Diastolic Murmur

Diastolic murmurs can be caused by various cardiac abnormalities. Valvular disorders such as aortic regurgitation, where the aortic valve fails to close properly, resulting in the backflow of blood from the aorta into the left ventricle during diastole, and mitral stenosis, characterized by the narrowing of the mitral valve and impeding blood flow from the left atrium to the left ventricle during diastole, are common causes. Increased blood flow through a normal valve can lead to diastolic murmurs as well. 

In conditions like anemia, which reduces the blood's oxygen-carrying capacity, the heart compensates by increasing blood flow, resulting in diastolic murmurs. Similarly, during pregnancy, physiological changes cause an increase in blood volume and flow through the heart, leading to diastolic murmurs. 

Other conditions that can cause diastolic murmurs include patent ductus arteriosus (PDA), where a fetal blood vessel persists after birth, causing abnormal blood flow between the aorta and pulmonary artery during diastole, and ventricular septal defect (VSD), which involves a hole in the wall separating the heart's ventricles, allowing blood to flow between them during diastole.

Characteristics of Diastolic Murmurs

Diastolic murmurs, which occur during the diastole phase of the cardiac cycle, possess distinct characteristics that help in their evaluation and diagnosis. These characteristics include:

1.) Timing: Diastolic murmurs occur between the second heart sound (S2) and the subsequent first heart sound (S1) of the next cardiac cycle. They can be further classified based on their timing within diastole, such as early diastolic, mid-diastolic, or late diastolic murmurs.

2.) Intensity: The intensity of diastolic murmurs can vary, ranging from soft to loud. The loudness of the murmur may provide information about the severity of the underlying condition.

3.) Pitch: Diastolic murmurs can have different pitches, ranging from low to high. The pitch can sometimes be described as a rumbling or blowing sound. The specific pitch can offer insights into the nature of the murmur and its origin.

4.) Quality: The quality or character of diastolic murmurs can vary. They may be described as a decrescendo, crescendo, or plateau-shaped sound, depending on the underlying cause.

5.) Location: The location where diastolic murmurs are best heard can indicate the specific valve or area of the heart affected. Common auscultatory sites include the apex, left sternal border, and right upper sternal border.

6.) Radiation: Diastolic murmurs may radiate to other areas of the chest, neck, or back, providing additional diagnostic clues.

7.) Timing in the Cardiac Cycle: The timing of diastolic murmurs within diastole can be further categorized. For example, an early diastolic murmur occurs shortly after S2, while a mid-diastolic murmur reaches its peak intensity in the middle of diastole. Late diastolic murmurs occur closer to the subsequent S1.

Types of Diastolic Murmurs

Diastolic murmurs can be classified based on their timing, intensity, pitch, and location. Common types include:

1.) Early Diastolic Murmurs

Early diastolic murmurs are abnormal heart sounds that occur in the early part of the diastole phase of the cardiac cycle. These murmurs typically start immediately after the second heart sound (S2) and can extend into the early part of diastole. Early diastolic murmurs are often associated with conditions such as aortic regurgitation or pulmonary regurgitation.

• a. Aortic Regurgitation: High-pitched, blowing murmur heard best at the left sternal border.

• b. Pulmonary Regurgitation: Low-pitched, decrescendo murmur heard best at the left upper sternal border.

2.) Mid-Diastolic Murmurs

Mid-diastolic murmurs are abnormal heart sounds that occur in the middle of the diastole phase of the cardiac cycle. These murmurs typically start after the second heart sound (S2) and before the next heart sound. Mid-diastolic murmurs are commonly associated with conditions such as mitral stenosis or tricuspid stenosis. 

• a. Mitral Stenosis: Low-pitched, rumbling murmur heard best at the apex with the patient in the left lateral decubitus position.

• b. Tricuspid Stenosis: Low-pitched, rumbling murmur heard best at the lower left sternal border.

These murmurs are best heard at specific locations on the chest using a stethoscope.

3.) Late Diastolic Murmurs

Late diastolic murmurs are abnormal heart sounds that occur in the latter part of the diastole phase of the cardiac cycle. These murmurs typically start after the second heart sound (S2) and continue until the next heart sound. Late diastolic murmurs are often associated with conditions such as mitral stenosis, where there is an obstruction to blood flow from the left atrium to the left ventricle during diastole. These murmurs are usually low-pitched and may be described as a rumbling or presystolic murmur. They are best heard at the apex of the heart using a stethoscope.

C.) Continuous Murmurs or Machinery Murmurs (Pansystolic Murmurs)

Continuous murmurs, also referred to as machinery murmurs, are abnormal heart sounds that are present throughout both systole and diastole, resulting in a continuous sound without a clear separation between the two phases of the cardiac cycle. These murmurs have distinct characteristics and can provide important insights into underlying cardiovascular conditions. 

Characteristics of Continuous Murmurs

Continuous murmurs are a distinct type of abnormal heart sound that differentiates them from other murmurs. They are characterized by specific features, including their timing, intensity, pitch, and location. Unlike other murmurs that may have specific phases in the cardiac cycle where they occur, continuous murmurs are present throughout both systole and diastole, creating a continuous sound without a pause. This continuous nature sets them apart from other types of murmurs.

In terms of intensity, continuous murmurs often have a moderate to high intensity, although the loudness may vary depending on the underlying cause. The pitch of these murmurs can range from low to high, and interestingly, the pitch may change along the course of the murmur. This variability in pitch can provide important diagnostic information about the underlying condition.

The location of continuous murmurs can vary depending on the specific underlying cause. Common sites for their auscultation include the precordium, which is the area of the chest overlying the heart, as well as major blood vessels. The precise location can provide clues about the origin of the murmur and aid in further evaluation and diagnosis.

Causes of Continuous Murmurs

Continuous murmurs can arise from various cardiac and non-cardiac conditions. The most common causes include:

1.) Patent Ductus Arteriosus (PDA)

PDA refers to the persistence of a fetal blood vessel, the ductus arteriosus, after birth. The continuous murmur in PDA is caused by the abnormal flow of blood between the aorta and pulmonary artery, resulting in a continuous shunting of blood throughout the cardiac cycle. The murmur is typically heard best at the left upper sternal border.

2.) Arteriovenous Fistula (AVF)

AVF is an abnormal connection between an artery and a vein. Continuous murmurs associated with AVF result from the high-pressure arterial blood flowing directly into a low-pressure venous system, bypassing capillary beds. The location of the murmur depends on the specific site of the arteriovenous connection.

3.) Aortic Regurgitation

Aortic regurgitation refers to the incompetence of the aortic valve, allowing backflow of blood from the aorta into the left ventricle during diastole. The continuous nature of the murmur in aortic regurgitation arises from the continuous flow of blood from the aorta to the left ventricle throughout the cardiac cycle. The murmur is often best heard at the left sternal border or in the suprasternal notch.

Continuous murmurs, or machinery murmurs, are abnormal heart sounds that persist throughout both systole and diastole. Their unique characteristics and clinical significance make them valuable clues in the diagnosis and management of underlying cardiovascular conditions.

Summary

In conclusion, the four heart sounds and heart murmurs provide important information about the health of the heart and the functioning of the cardiovascular system. If you have any concerns about heart sounds or heart murmurs, it is essential to speak with your doctor and discuss the best diagnostic options for you.