Heart Sounds A LearnTheHeart.com Slideshow Presentation What are heart sounds? A heart sound is a distinct audible event that occurs at a specific point in the cardiac cycle. There are two normal heart sounds (S1 and S2) and many abnormal heart sounds including S3, S4, clicks, and snaps. How to listen to the heart A = aortic listening post P = pulmonic listening post E T = tricuspid listening post M = mitral listening post E = “Erb’s point” The stethoscope basics The stethoscope • Every stethoscope has a “bell” and a “diaphragm”. • The bell is used to hear low pitched sounds and the diaphragm is used to hear high pitched sounds. The First Heart Sound (S1) What is the first heart sound (S1) • The first heart sound results from the closing of the mitral and tricuspid valves. • S1 is a high pitched sound heard best with the diaphragm of the stethoscope. • S1 can be divided into two components, M1 and T1. The Second Heart Sound (S2) What is the second heart sound (S2) • The second heart sound results from the closure of the aortic and and pulmonic valves. • S2 is a high pitched sound heard best with the diaphragm of the stethoscope. • S2 can be divided into two components, A2 and P2. Normal 1st and 2nd heart sounds Normal heart sounds • Normal heart sounds are described mainly by intensity and “splitting” (S1 and S2 sounds) or by their presence or absence (S3 and S4 sounds). • Any changes from normal can be a very important clinical indicator of certain cardiac diseases, thus learning heart sounds is critical to diagnosis in patients with cardiac diseases. The 1st heart sound The first heart sound • There are two components of the first heart sound designated T1 (tricuspid valve sound) and M1 (mitral valve sound). • The T1 sound is softer than M1 due to the lower pressures on the right side of the heart. • In up to 40% of normal people, the T1 sound can be distinguished from the M1 sound! Where would you listen to hear a split S1? The 1st heart sound The first heart sound – splitting • Normal splitting is very brief, however certain situations can increase or decrease the splitting of S1. The 1st heart sound The 1st heart sound The 1st heart sound - intensity The first heart sound • Certain cardiac conditions/abnormalities can alter the intensity of the S1 heart sound. Since M1 is much louder than T1, only things that effect M1 alter the S1 intensity. • Three things affect the intensity of the 1st heart sound: 1) The mobility of the mitral valve leaflets 2) The distance that separate the leaflets at the onset of ventricular contraction 3) The rate/intensity of ventricular contraction The 1st heart sound - intensity The mobility of the valve leaflets • If the valve leaflets are unable to open fully due to severe calcification/stenosis, then when they close they will not produce as loud of a sound. • A good example is mitral stenosis (MS). • In severe MS, the valves simply can’t open hardly at all, so the intensity of the S1 is decreased. • When MS is mild, the high pressure in the left atrial (LA) forces the mobile parts of the valve farther apart, so when they close the S1 is louder. (see next slide) The 1st heart sound - intensity The distance of the valve leaflets • Valves close very quickly, so the further apart the valve leaflets are at the onset of valve closure, the greater the force of valve closure. • A good example is mild MS. In mild MS, the pressures in the LA are elevated to the point that the mobile part of the mitral valve leaflets are forced far apart, so when they close quickly, a greater force is produced causing a louder 1st heart sound. The 1st heart sound - intensity The distance of the valve leaflets – PR interval • The PR interval on the EKG is another determinant of the intensity of the 1st heart sound. • What part of the cardiac cycle does the PR interval represent? The 1st heart sound - intensity The PR interval starts as the sinus node generates an action potential that spreads through the atrium. The P wave represents atrial depolarization and occurs at the onset of atrial contraction. The QRS complex represents ventricular depolarization. Therefore, the PR interval is the time it takes for the action potential to travel from the SA node, through the atrium, then through the AV node to the ventricles. The 1st heart sound - intensity The distance of the valve leaflets • In a person with a long PR interval (1st degree AV block), the time between atrial contraction and ventricular contraction is short. • This results in greater filling of the ventricles. When the ventricles are full at the onset of contraction, the valve leaflets are closer, thus the S1 heart sound is very soft. The 1st heart sound - intensity The distance of the valve leaflets • In a person with a short PR interval, the time between atrial contraction and ventricular contraction is short. • This results in less filling of the ventricles. When the ventricles are less full at the onset of contraction, the valve leaflets are further apart, thus the S1 heart sound is very soft. The 1st heart sound - intensity The rate/intensity of ventricular contraction • If the ventricle contracts faster and harder, the valves will also close with more force. This will increase the intensity of the S1 heart sound. • So when tachycardia exists, the S1 intensity increases. • Likewise, with bradycardia, the S1 intensity decreases. • When the inotropy (contractility) is enhanced by ß1 stimulation, the S1 is increased. • When the myocardium is weak/damaged, the S1 is softer. The 1st heart sound - intensity Summary – Intensity of S1 Accentuated S1 Diminished S1 • Shortened PR interval • Long PR interval • Mild MS • Moderate to severe MS • Tachycardia • Bradycardia • Increased inotropy • Decreased inotropy The 2nd heart sound The 2nd heart sound (S2) • There are two components of the second heart sound designated A2 (aortic valve sound) and P2 (pulmonic valve sound). • The P2 sound is softer than A2 due to the lower pressures on the right side of the heart. • In almost 100% of normal people, the A2 sound can be distinguished from the P2 sound! This results in a “physiologic” or normal split S2 heart sound. • Where would you listen to hear a split S2? The 2nd heart sound The 2nd heart sound (S2) • A great deal of clinical information can be obtained by analyzing the splitting pattern of the S2 heart sound and by determining the intensity of S2 • The intensity of the A2 heart sound is increased when the systemic arterial blood pressure is high. • Likewise, the P2 heart sound intensity is increased when the pulmonary artery blood pressure is elevated, as in pulmonary hypertension. • When the pulmonic or aortic valves are severely stenosed, their respective sounds will be diminished. This is an important way to determine the severity of aortic stenosis on physical examination. The 2nd heart sound The 2nd heart sound – types of splitting • Physiologic or normal splitting of S2 - The A2 comes before the P2 during inspiration only. • Widened split S2 - The A2 always comes before the P2, but is more pronounced during inspiration. • Fixed split S2 - The A2 always comes before the P2 and is equally split throughout inspiration and expiration. • Paradoxical split S2 - The P2 comes before the S2 during expiration, and the splitting disappears during inhalation. The A2 comes before the P2 during inspiration only since P2 is significantly delayed and A2 is slightly premature during inspiration. Causes: Normal in 90% of people The P2 comes before the A2 during expiration, and the splitting disappears during inhalation since A2 is always delayed. Causes: LBBB, AS, or HOCM The A2 always comes before the P2, but the splitting is more pronounced during inspiration. So P2 is always delayed, but more so during inspiration. Causes: RBBB, PS, or severe MR The A2 always comes before the P2 and is equally split throughout inspiration and expiration. So P2 is always delayed, but equally in inspiration and expiration. Causes: Atrial septal defect (ASD) The 2nd heart sound The 2nd heart sound – physiologic splitting • Normally, the A2 heart sound will slightly precede the P2 heart sound during inspiration, but they will occur almost simultaneously during expiration. The 2nd heart sound The 2nd heart sound – physiologic splitting • This is because inspiration increases venous return of blood to the right side of the heart, thus more blood flows across the pulmonic valve delaying it’s closure (major effect). • Also, during inspiration, filling of the left atrium is decreased resulting in a slightly premature A2 heart sound (minor effect). • The combination of a significantly delayed P2 and a slightly early A2 during inspiration leads to a “physiologic” split S2 during inspiration and the absence of a split S2 during expiration. The 2nd heart sound The 2nd heart sound – Paradoxical splitting • In certain pathological situations, the A2 heart sound is significantly delayed to the point that the P2 actually precedes the A2 heart sound. The 2nd heart sound The 2nd heart sound – Paradoxical splitting • This results in a splitting of S2 during expiration, then when venous return increases with inspiration (delaying P2), the A2 and P2 sounds overlap causing the splitting of S2 to disappear. • Causes of a paradoxical split S2 include any condition in which the A2 is significantly delayed. • The two most important causes are aortic stenosis and in a person with a left bundle branch block (LBBB). The 2nd heart sound The 2nd heart sound – Paradoxical splitting • Aortic stenosis makes it difficult to eject blood through the aortic valve from the left ventricle, so the aortic valve must remain open for a longer time to maintain cardiac output. The 2nd heart sound • A LBBB also causes significant delay of aortic valve closure since it takes longer for the action potentials to spread to the left ventricle. The 2nd heart sound The 2nd heart sound – Widened splitting • A widened split S2 occurs when pulmonic valve closure (P2) is always delayed and inspiration causes a further delay of P2. This occurs with a RBBB or pulmonic valve stenosis. The 2nd heart sound The 2nd heart sound – Fixed splitting • A fixed split S2 only occurs in one clinical situation which is in the setting of an atrial septal defect (ASD). The P2 is delayed the same amount during inspiration and expiration. Distinguishing Heart Sounds Which one is S1 and which is S2? • In the setting of tachycardia, it may be difficult to distinguish S1 from S2. • Remember: S1 always occurs at the same time as the peripheral pulses. So feel the radial pulse while listening to the heart to find S1. The 3rd heart sound The 3rd heart sound • The 3rd heart sound (S3) is produced just after the mitral valve opens when blood passively fills the left ventricle. This passive filling causes a compliant left ventricle to rapidly expand in size thus tensing the chordae tendinae that hold the mitral valve in place. This chordae tendinae tensing produces the S3 sound. S3 occurs in early diastole. The 3rd heart sound The 3rd heart sound • An S3 will only occur if the left ventricle is very compliant and able to relax/expand rapidly with passive LV filling. • In most people, the LV does not expand enough to cause significant tensing of the chordae, so no S3 sound is heart. • On physical exam, how could you tell an S3 heart sound apart from a split S2 heart sound? • Hint: The S3 heart sound is low-pitched. The 3rd heart sound The 3rd heart sound • An S3 sound is often present in children, pregnant females, and well trained athletes since their LV is able to expand more than a normal person. • S3 is best heard with the patient in the left lateral decubitus position (laying on their left side). S3 may disappear when sitting. • An S3 sound is also frequently present with systolic heart failure. In this situation, the LV is dilated and damaged to the point where it can rapidly expand upon passive filling. • An S3 heart sound is an important physical exam finding that may indicate systolic heart failure in many people! The 3rd heart sound S3 present Normal heart Dilated LV – systolic CHF The 4th heart sound The 4th heart sound • The 4th heart sound (S4) is produced when the left atrium contracts during the active filling phase of the LV and blood strikes a non-compliant left ventricle. S4 occurs in late diastole. The 4th heart sound The 4th heart sound • The S4 will only be audible when the ventricle is non-compliant, thus unable to appropriately relax during LV filling. • In most people, the LV has at least some compliance, thus atrial contraction does not normally cause an audible S4. • On physical exam, how could you tell an S4 heart sound apart from a split S1 heart sound? • Hint: The S4 heart sound is low-pitched. The 4th heart sound The 4th heart sound • So an S4 heart sound will be present when there is a non- compliant LV. • This occurs most commonly when there is left ventricular hypertrophy (LVH) or active myocardial ischemia. • Remember muscle physiology: ATP is required to release myosin from actin, so during ischemia when ATP can’t be produced, myosin and actin remain bound and the LV can’t relax. This results in an S4 occurs. • An S4 heart sound is an important physical exam finding that may indicate diastolic heart failure in many people! The 4th heart sound The 4th heart sound • In people with severe systemic hypertension, the long-term strain on the LV results in LVH. So people with uncontrolled HTN frequently have an S4 present. • Once the HTN is well controlled, the LVH can regress over time causing the S4 sound to disappear. • So in the setting of HTN, an S4 usually indicates poor control of blood pressure over a long period of time. • An S4 heart sound is an important physical exam finding that may indicate diastolic heart failure in many people! The 4th heart sound S4 present Normal heart LVH – diastolic CHF Comparing the “gallop” heart sounds S3 – “ventricular gallop” S4 – “atrial gallop” • Occurs in early diastole • Occurs in late diastole • Occurs during passive LV filling • Occurs during active LV filling • May be normal at times • Almost always abnormal • Requires a very compliant LV • Requires a non-compliant LV • Can be a sign of systolic CHF • Can be a sign of diastolic CHF Extra-systolic heart sounds Extra-systolic heart sounds • Includes systolic ejection sounds from the aortic and pulmonic valves. • The click of mitral valve prolapse occurs in mid-late systole and will vary in position based on the volume of the LV. • With larger LV volumes (squatting), there is less prolapse of the mitral valve, thus the click moves later in systole. • With smaller LV volumes (standing or Valsalva), there is more prolapse of the mitral valve, thus the click moves earlier in systole.