ICL 1.12: Cardiac Blood Flow & Heart Sounds Introduction

Question 1

what is the normal flow of blood through the heart?

Answer 1

SVC + IVC –> R. atrium –> tricuspid –> R. ventricle –> pulmonary valve –> pulmonary artery –> lungs –> pulmonary veins –> L. atrium –> mitral valve –> L. ventricle –> aortic valve –> aorta –> body

Question 2

what is happening during lub?

Answer 2

S1

closure of the Tricuspid & Mitral valves which separate the atria and ventricles

valves close due to the increased pressure in the ventricles when they contract

times the onset of systole = ventricle contraction

Question 3

what is happening during dub?

Answer 3

closure of the Aortic & Pulmonic valves when ventricles relax and pressure drops

times the onset of diastole

Question 4

what is normal S2 splitting?

Answer 4

the aortic and pulmonic valves usually open and close together but in normal physiologic splitting the aortic valve closes before the pulmonic valve during inspiration and you can hear that

inspiration causes a drop in intrathoracic pressure –> drop in pressure results in increased venous return to the right side of the heart –> increased venous return results in prolongation of the time that the pulmonic valve is open, which results in the pulmonic valve closing after the aortic and can be heard

should only be heard during inspiration!!

Question 5

what are the 3 abnormal splitting of S2?

Answer 5

1. paradoxical splitting of S2
2. wide splitting of S2
3. fixed splitting of S2

Question 6

what is paradoxical splitting of S2?

Answer 6

the aortic valve closes after the pulmonic valve due to conditions that cause the aortic valve to take longer to close (i.e. aortic stenosis)

split is only heard during expiration because the “normal” splitting during inspiration “cancels out” the delay during that phase.

also referred to as “Reversed Splitting”

Question 7

what is wide splitting of S2?

Answer 7

exaggeration of the “normal” split of S2 during inspiration

during expiration a short split can be heard

caused by conditions that delay closure of the pulmonic valve (Pulmonary HTN, Pulmonic Stenosis, RBBB)

Question 8

what is fixed splitting of S2? what is the common cause of fixed S2 splitting?

Answer 8

splitting is heard during both inspiration and expiration of every dub– so every time you hear dub you hear a split which isn’t normal

most often associated with an ASD due to excess blood on right side of heart all the time from shunting being pumped across the pulmonic valve – so regardless of inspiration or expiration there will be a delay in closure of the pulmonic valve

Question 9

what is S3?

Answer 9

an extra sound heard early in diastole right after S2 –> diastole is when the atria are emptying into the ventricles

it’s caused by blood rushing in from the atria to the ventricle at the start of diastole colliding with ventricular blood or a compliant wall

can be normal in kids, athletes, and pregnant women due to their normal high output states but in others, usually associated with CHF/volume overload

Question 10

what is S4? what causes it?

Answer 10

an extra sound heard late in diastole right before S1

it’s caused by blood going into a stiff ventricle during the atrial kick at the end of diastole

the blood is filling into the ventricle but it’s still so it’s hard to get all the blood into the stiff ventricle so you get the atrial kick where the atrium is trying to shove that last bit of blood into the ventricle

this is NEVER normal! it’s often heard in hypertrophic cardiomyopathy

Question 11

what causes heart murmurs?

Answer 11

they are caused by increased flow or turbulent flow across a valve or opening

think about a rocky creek vs. a calm lake, turbulent water makes noise!

Question 12

when do heart murmurs happen during a heart cycle?

Answer 12

can occur in systole, diastole, or both

maybe the valves are stiff and the blood has to get over rocks to get through or maybe the valve is flappy and you get back flow when there’s another contraction

you can differentiate a murmur from S1 and S2 because of its duration, it has length to it

Question 13

what are the characteristics of heart murmurs?

Answer 13

1. timing (systolic, diastolic)
2. location
3. intensity
4. pitch (bell hears low pitch better)
5. radiation

Question 14

what are innocent systolic murmurs?

Answer 14

most common cause of mid-systolic murmurs

90% of them are associated with a normal echocardiogram

they can be seen in anyone, young people, anemia, pregnancy, thyrotoxicosis

Question 15

what conditions can cause systolic murmurs?

Answer 15

these are murmurs heard between S1 and S2

1. innocent flow murmurs
2. mitral regurgitation
3. tricuspid regurgitation
4. aortic outflow obstruction (aortic stenosis, HCM)
5. pulmonic outflow obstruction (pulmonary stenosis)
6. aortic sclerosis
7. mitral valve prolapse
8. tricuspid valve prolapse

don’t memorize right now

Question 16

what are diastolic murmurs?

Answer 16

murmurs between S2 and S1 during diastole

they’re rarely normal and can be caused by aortic regurgitation or pulmonic regurgitation

Question 17

what is a continuous murmur? what can cause them?

Answer 17

murmurs during both systolic and diastolic

the whole heart cycle sounds like a murmur

most commonly caused by patent ductus arteriosus but also by some shunts or coarctation of the aorta

Question 18

what causes heart clicks?

Answer 18

sounds caused by prolapse or thickening of valve leaflets –> prolapse is when the valve doesn’t close smoothly or evenly, but bulge (prolapse) upward

mitral prolapse would cause a systolic click because if the mitral valve isn’t closing, when the ventricle contracts the blood will flow back into the atria and you hear a click

Question 19

what is pericardial rub?

Answer 19

crackling sound caused by rubbing together of two surfaces of pericardial sack – so what causes it is the movement so you’ll hear it every time the heart beats

generally heard over left sternal border and louder with inspiration and leaning forward

seen with pericarditis

must differentiate from pleural rub!