Heart Sounds The Normal Heart Sounds Abnormal Heart Sounds

There are normally two distinct heart sounds, often described as a lub and a dub (although the words used to describe them vary regionally).

Auscultation, the process of listening to the heart sounds, is part of the general physical exam. Auscultation is used to identify problems with the valves of the heart. Stenosis (Impaired opening of a heart valve) will cause turbulence as blood flows through the valve. The turbulance due to a stenotic valve will cause a murmur while blood flows through the valve. Insufficiency or regurgitation is the leaking of blood through the valve when the valve is supposed to be closed. Regurgitant murmurs will be heard when the valve is supposed to be closed.

1 The normal heart sounds

The first heart sound, known as S₁, is caused by the closure of the mitral and tricuspid (the atrioventricular) valves at the beginning of ventricular systole. At the beginning of ventricular systole, the pressure in the left and right ventricles rise above the pressure in the left and right atrium, respectively, closing the mitral and tricuspid valves. It is the closure of these valves that prevents regurgitation of blood from the ventricles to the atria.

The second heart sound, known as S₂, is cause by the closure of the aortic and pulmonic valves at the end of ventricular systole. As the pressure in the left ventricle falls, it will drop below the pressure in the aorta, and the aortic valve will close. Similarly, as the pressure in the right ventricle falls below the pressure in the pulmonary artery, the pulmonic valve will close.

Due to the higher pressure in the aorta compared to the pulmonary artery, the aortic valve tends to close before the pulmonic valve, so the second heart sound may have an audible split. A split S₂ is made up of an A₂ and a P₂ components, signifying the closure of the aortic and pulmonic valves, respectively. Under normal conditions, A₂ always occurs before P₂.

Paradoxical split of S₂, when P₂ component occurs before A₂ component may be caused by right ventricular pacemaker or ectopy, severe aortic valve disease, or patent ductus arteriosus.

In normal individuals, there is respiratory variations in the splitting of the second heart sound (S₂). During inspiration, the negative intrathoracic pressure causes increased blood return into the right side of the heart. The increased blood volume in the right ventricle causes the pulmonic valve to stay open longer during ventricular systole. This causes a normal delay in the P₂ component of S₂. During expiration, the positive intrathoracic pressure causes decreased blood return to the right side of the heart. The reduced volume in the right ventricle allows the pulmonic valve to close earlier at the end of ventricular systole, causing P₂ to occur earlier.

2 Abnormal heart sounds

Most sounds of the heart other than S₁ and S₂ are abnormal heart sounds. Sometimes it is possible to hear flow through the aortic valve, due to increased cardiac output. This flow murmur is a normal variant, commonly heard in children and pregnant females.

2.1 S₃ gallop

A third heart sound, known as an S₃ or an S₃ gallop, is due to ventricular filling. It is commonly heard at the apex of the heart in athletes and young individuals, and may be heard in the third trimester of pregnancy. The sound is believed to be due to rapid vibration of the left ventricle due to brisk filling with blood from the left atrium. If an S₃ is heard in the elderly, it's considered an abnormal finding, suggesting volume overload of the left ventricle. In the elderly, an S₃ (when present) is considered diagnostic of congestive heart failure.

2.2 S₄ gallop

An S₄ gallop is a fourth heart sound due to resistance to atrial filling following atrial contraction, and is heard just before S₁. An S₄ is usually considered an abnormal heart sound. However, a grade 1 S₄ gallop can be considered a normal finding in trained athletes and after 40 years of age. Otherwise, it occurs in a hypertrophied ventricle, when atrial kick causes a diastolic vibration. Since S₄ is due to atrial kick, it cannot be heard during atrial fibrillation. Causes of a left-sided S₄ include hypertensive heart disease, coronary artery disease, aortic stenosis, and cardiomyopathy. The less common right-sided S₄ often gets louder with inspiration. Causes of right-sided S₄ include pulmonary hypertension and pulmonic disease. An S₄ may also be associated with delayed conduction between atria and ventricles. This delay separates the normally faint atrial sound from the louder S₁ and makes it audible.

2.3 Fixed splitting of S₂

In individuals with an atrial septal defect (ASD), there is a fixed splitting of S₂. This is pathognemonic of ASD, as no other cardiac defect causes a fixed splitting of S₂. The reason why there is a fixed splitting of the second heart sound is that the extra blood return during inspiration gets equalized between the left and right atrium due to the communication that exists between the atria in individuals with ASD. A wide, fixed, split of S2 may be caused also by an acute pulmonary hypertension, or pulmonic stenosis.

3 Cardiac conditions and related heart sounds

Many cardiac conditions can cause heart murmurs. However, the murmurs produced often change with the severity of the cardiac disease. Often, the astute physician can diagnose a cardiac condition solely on the murmur and related physical examination.

3.1 Aortic insufficiency

Aortic insufficiency is the abnormal leaking of blood from the aorta to the left ventricle. The murmur of acute aortic insufficiency (often due to aortic dissectionAortic dissection is a tear of the aorta (the largest artery of the body). This tear causes blood to flow between the layers of the wall of the aorta and dissects the layers apart. Aortic dissection is an extremely serious medical emergency and can quickl or endocarditisEndocarditis is an inflammation of the inner layer of the heart, the endocardium. The most common structures involved are the heart valves. Endocarditis can be classified as either infective or non-infective depending on whether a foreign organism is caus) may be very soft or even absent. The murmur of chronic aortic insufficiency has the following characteristics:

Systolic ejection click
Ejection murmur
S₃ present
Holodiastolic decrescendo murmur (If radiation to the right parasternal region, consider ascending aortic aneurysmAn aortic aneurysm is a general term for any localized dilatation or aneurysm of the aorta, usually representing an underlying weakness in the wall of the aorta at that location. This physical change in the aortic diameter can occur secondary to an intrin)
Austin flint murmur (an apical diastolic rumble due to mitral regurgitation)

4 Interventions that alter heart sounds

There are a number of interventions that can be performed that alter the intensity and characteristics of abnormal heart sounds. These interventions can be performed to differentiate the different heart sounds and obtain a diagnosis of the cardiac anomaly that causes the heart sound.

4.1 Respiratory changes

InspirationInhalation is the movement of air from the external environment, through the airways, into the alveoli during breathing. During inhalation, air passes through either the nose or the mouth into the pharynx ( throat). The pharynx attaches to the larynx, whi causes a decrease in intrathoracic pressure, allowing air to enter the lungs. This decrease in intrathoracicThe thoracic cavity is the chamber of the human body (and other animal bodies) that is enclosed by the ribcage and the diaphragm. It houses # the lungs, # the heart, # the thoracic aorta, # the main pulmonary artery and its branches, # the thymus gland, # pressure also causes an increase in the venous blood return to the right side of the heart. Therefore, right-sided murmurs generally increase in intensity with inspiration. The increased volume of blood entering the right sided chambers of the heart restricts the amount of blood entering the left sided chambers of the heart. This causes left-sided murmurs to generally decrease in intensity during inspiration.

With expirationExhalation is the movement of air out of the alveoli, through the airways, to the external environment during breathing. During exercise During exercise, exhalation becomes an active process. See also': Lung., the opposite hemodynamic changes occur. This means that left sided murmurs generally increase in intensity during expiration and right sided murmurs generally decrease in intensity during expiration.

5 Related topics

Physical examinationIn medicine, physical examination is the process by which the physician investigates the body of a patient for signs of disease to aid in determining the correct diagnosis. It generally follows the taking of the medical history an account of the symptoms
Anatomy
- Heart
- Heart valve
Pathophysiology
- Mitral stenosis
- Mitral regurgitation
- Aortic stenosis
- Aortic insufficiency
- Pulmonic stenosis
- Pulmonic insufficiency
- Tricuspid stenosis
- Tricuspid insufficiency

6 External links

http://www.nlm.nih.gov/medlineplus/ency/article/003266.htm

Cardiology

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Home > Heart sounds

1 The normal heart sounds

2 Abnormal heart sounds

2.1 S₃ gallop

2.2 S₄ gallop

2.3 Fixed splitting of S₂

3 Cardiac conditions and related heart sounds

3.1 Aortic insufficiency

4 Interventions that alter heart sounds

4.1 Respiratory changes

5 Related topics

6 External links

Topics: Heart Sounds, The Normal Heart Sounds, Abnormal Heart Sounds...

Home > Heart sounds

1 The normal heart sounds

2 Abnormal heart sounds

2.1 S3 gallop

2.2 S4 gallop

2.3 Fixed splitting of S2

3 Cardiac conditions and related heart sounds

3.1 Aortic insufficiency

4 Interventions that alter heart sounds

4.1 Respiratory changes

5 Related topics

6 External links

Topics: Heart Sounds, The Normal Heart Sounds, Abnormal Heart Sounds...

2.1 S₃ gallop

2.2 S₄ gallop

2.3 Fixed splitting of S₂