Cardiac Auscultation - Heart Sounds and Murmurs PDF

Cardiac auscultation, heart sounds and murmurs Dr B White – Spring Semester – MGEM2019 Learning objectives u To relate surface anatomy of the heart to the correct placement of a stethoscope for auscultation of the heart u To describe the normal heart sounds, how they are generated, and where on...

Cardiac auscultation, heart sounds and murmurs Dr B White – Spring Semester – MGEM2019 Learning objectives u To relate surface anatomy of the heart to the correct placement of a stethoscope for auscultation of the heart u To describe the normal heart sounds, how they are generated, and where one should listen for them u To describe common causes of heart murmurs, such as valvular heart disease and septal defects u To describe the point(s) in the cardiac cycle where murmurs associated with different forms of cardiac disease would be heard Valves & Heart Sounds: u If we listen to the heart with a stethoscope, we hear something that sounds like “lub-dub” u These sounds are caused by the closure of the heart valves at various points in the cardiac cycle: u When the tricuspid and mitral valves close (at the start of ventricular contraction, or systole), the turbulent flow of blood and the ‘wobble’ of the fibrous tissue around them cause the so-called first heart sound (S1 or “lub”) u When the pulmonary and aortic valves close (as the vessels start to relax, diastole), the same factors cause the second heart sound (S2 or “dub”) u When someone has valvular heart disease, extra sounds can often be heard between S1 and S2 (a systolic murmur) or between S2 and S1 (a diastolic murmur) Surface locations of the heart u On the costal cartilage 2nd costal cartilage (left) 3rd costal cartilage (right) 6th costal cartilage (right) u On the intercostal space, mid-clavicular line 5th intercostal space, midclavicular line (left) u Right border – right atrium u Right Inferior border – right ventricle u Left border – left ventricle u Left atrium is posterior These are the surface locations of where the heart sits in the chest – these are not the best places to necessarily listen to the heart (this is due to acoustic conduction of sounds) Where to place a stethoscope to hear specific valves u Aortic Valve Area Second right intercostal space (ICS), right sternal border (A1) u A1 Second left intercostal space (ICS), left sternal border (P1) P1 u M1 Tricuspid Valve Area Fourth left intercostal space (ICS), left sternal border (T1) T1 One way to remember the positions is to think of an inverted J shape between the 2nd intercostal spaces down to the 5th on the left Pulmonic Valve Area u Mitral Valve Area Fifth mid intercostal space (ICS), left mid-clavicular line (M1) (also location for listening for apical pulse) Aortic valve u Right 2nd intercostal space u 2nd sound (S2) loudest Pulmonary valve u Left 2nd intercostal space u 2nd sound (S2) loudest Tricuspid valve u Left sternal edge – 4th intercostal space u 1st sound (S1) loudest Mitral valve u Listen at the apex - Fifth intercostal space - left mid-clavicular line u 1st sound (S1) loudest u (also location for listening for apical pulse) The Valves sounds u u When the tricuspid and mitral valves close (at the start of ventricular contraction, or systole), the turbulent flow of blood and the ‘wobble’ of the fibrous tissue around them cause the so-called first heart sound (S1 or “lub”) When the pulmonary and aortic valves close (as the vessels start to relax, diastole), the same factors cause the second heart sound (S2 or “dub”) Diastole S2 or “dub” Diastole u Systole When someone has valvular heart disease, extra sounds can often be heard: u between S1 and S2 (a systolic murmur) u between S2 and S1 (a diastolic murmur) Systole S1 or “lub” Diastole S2 or “dub” Auscultation and systole/diastole NOTE: There is also a third and a fourth heart sound, S3 and S4. They can occur in normal persons or be associated with pathological processes. Because of their cadence or rhythmic timing S3 and S4 are called gallops. Systole Standard S1 + S2 with split S1 S2 closure of closure of mitral and aortic and tricuspid pulmonary valves valves Diastole Systole Diastole There is physiological splitting of S2 (the aortic valve closes just before the pulmonary valve), which is enhanced by deep inspiration Gallops are low frequency sounds that are associated with diastolic filling. Arterial pulses and systole/diastole Systole 120 Arterial Pressure (mmHg) 80 Diastole Systole Diastole Systolic and diastolic murmurs Systole Diastole Systole Diastole 120 Arterial Pressure (mmHg) 80 Murmurs heard when the artery is ‘pulsing’ are systolic murmurs – these would be heard between S1 and S2 Murmurs heard when the artery is not ‘pulsing’ are diastolic murmurs – these would be heard between S2 and S1 of the next cycle Aortic Stenosis (Early) Aortic Stenosis (Late) Mitral Valve Prolapse Ventricular Septal Defect Mitral Regurgitation Systolic Murmurs Systole Diastole Systole Diastole Systolic murmurs will be heard when: • the aortic valve is stenosed, and flow of blood out of the left ventricle is turbulent • the mitral valve is incompetent, and ventricular contraction pushes blood the wrong way, back into the left atrium • there is a ventricular septal defect meaning that blood is forced from the left ventricle into the right ventricle during systole In all three cases, this can lead to reduced stroke volume and reduced cardiac output. Aortic Stenosis (Early) Aortic Stenosis (Late) Mitral Valve Prolapse Ventricular Septal Defect Mitral Regurgitation Systolic murmurs 2 Systole Diastole Systole Diastole The murmur of mitral regurgitation is pan-systolic (i.e. is heard throughout systole) and is heard best at the left lower sternal edge The murmur of aortic stenosis is mid-systolic (only heard when aortic valve is open) and heard best in the right 2nd intercostal space on the sternal edge Aortic Regurgitation Mitral Stenosis Diastolic murmurs 1 Systole Diastole Systole Diastole Diastolic murmurs will be heard when: • the mitral valve is stenosed, and flow of blood from the left atrium to the left ventricle is turbulent • the aortic valve is incompetent, and blood leaks back into the left ventricle from the aorta – this may be seen as a ‘collapsing pulse’ In both cases, this can lead to blood ‘backing up’ into the pulmonary circulation, with symptoms of breathlessness and potentially pulmonary oedema. Aortic Regurgitation Mitral Stenosis Diastolic murmurs 2 Systole Diastole Systole Diastole The murmur of mitral stenosis is mid-diastolic and is heard best at the cardiac apex (5 ICS, MCL). This is a low pitched sound and the bell of the stethoscope should be used The murmur of aortic regurgitation occurs early in diastole and is heard best in the left lower sternal edge Summary u Relate surface anatomy of the heart to the correct placement of a stethoscope for auscultation of the heart u Describe the normal heart sounds, how they are generated, and where one should listen for them u Describe common causes of heart murmurs, such as valvular heart disease and septal defects u Describe the point(s) in the cardiac cycle where murmurs associated with different forms of cardiac disease would be heard Reading u Color Atlas and Text of Clinical Medicine, 3rd Ed. pp 220-225. UNaD WB141 FOR u Instant Notes Human Physiology, Topics D1 and D7. UNaD QT104 MAC