heart sounds

Question 1

S1 frequency

Answer 1

HIGH frequency (diaphragm)

Question 2

where is S1 best heard

Answer 2

at apex

Question 3

S2 frequency

Answer 3

HIGH frequency (diaphragm)

Question 4

where is S2 best heard

Answer 4

pulmonic closure (P2)–> at 2-3 intercostal space, L sternal border

aortic closure (A2)–> at 2-3 intercostal space at R sternal border

Question 5

when do you hear S2 as one sound? as two sounds?

Answer 5

one sound on expiration

two sounds on inspiration (physiological splitting)

Question 6

what causes S3

Answer 6

tensing or chordae tendinae during rapid FILLING and expansion of ventricle

normal finding in children and young adults, indicating supple ventricle with normal rapid expansion

disease sign in older adults indicating VOLUME OVERLOAD, mitral or tricuspid REGURGITATION

Question 7

S3 frequency

Answer 7

LOW frequency (bell)

Question 8

is S3 a systolic or diastolic sound?

Answer 8

diastolic (“ventricular gallop”)

Question 9

what causes an S4 heart sound

Answer 9

atria vigorously contracting against a STIFFENED VENTRICLE

can indicate a disease in ventricular compliance resulting from ventricular hypertrophy or myocardial ischemia

S4 is NEVER normal

Question 10

when is S4 heard

Answer 10

late diastole (right before S1)

Question 11

is S4 a systolic or diastolic sound?

Answer 11

diastolic (“atrial gallop”)

Question 12

S4 frequency

Answer 12

LOW frequency (bell)

Question 13

what causes physiological splitting of S2

Answer 13

inspiration causes negative intrathoracic pressure which transiently increases the capacity of the pulmonary vessels, which causes a delay in diastolic back pressure of the pulmonary artery causing a DELAYED P2

decreased venous return to the heart due to increased pulmonary capacity causes reduced filling of the LV and thus a lower stroke volume during the next contraction of the LV which means less time is needed for the LV to empty–> pressure drops sooner in LV and you get EARLIER A2

Question 14

what causes widened S2 splitting

Answer 14

separation of A2 and P2 in both expiration and inspiration

even wider during inspiration

usually due to LATE P2 which often occurs during RBBB and PULMONIC STENOSIS

Question 15

what causes fixed splitting of S2

Answer 15

abnormally wide A2 and P2 split that persists throughout the cardiac cycle

most common cause is ATRIAL SEPTAL DEFECT

chronic VOLUME OVERLOAD of the R side circulation (i.e L–>R SHUNT) results in high capacitance, low resistance pulmonary vasculature–> this delays pulmonary back pressure and delays P2

pattern doesnt change between inspiration and expiration because inspiration no longer substantially changes the pulm vessel capacity

Question 16

what causes paradoxical splitting of S2

Answer 16

S2 split on EXpiration that disappears on inspiration

reflects abnormal delay in closure of aortic valve (DELAYED A2) such that it follows P2

since P2 is normally delayed during inspiration, this normal P2 delay matches the abnormally late A2 during times of inspiration and thats why theres no split on inspiration but there is on expiration when P2 is earlier once again but A2 remains late

caused by LBBB or when ventricular ejection is greatly prolonged such as in AORTIC STENOSIS