cardiac cycle and heart murmurs

what occurs during systole?

Ventricles contract and blood is ejected into circulation

which valves are open during systole?

Both semilunar valves (pulmonic and aortic) are open to allow blood to lead the ventricle

which valves are closed during systole?

Both AV valves (mitral valve in left side, tricuspid on right side) are closed to prevent backflow into the atria

explain how the semilunar valves are able to open during systole

Ventricular pressure > great artery pressure → semilunar valves open → ejection of blood

what is happening during diastole?

Ventricles relax and fill with flood after ejection has completed

which valves are closed during diastole?

Both semilunar valves are closed to prevent backflow into the ventricles

which valves are open during diastole?

Both AV valves are open to allow blood to flow from the large veins through the atria into the ventricles

what phases of the cardiac cycle are associated with diastole?

• phase 5

• phase 1

• phase 2

what heart sound is associated with phase 5 of the cardiac cycle?

S2 sound

what occurs with the valves in phase 5 of the cardiac cycle?

All valves are closed

what happens with pressure during phase 5 of the cardiac cycle?

• Decrease of pressure in the chambers

• Pressure in aorta is greater than the pressure in the ventricles, but volume in the left ventricle remains the same throughout

what do we call phase 5 of the cardiac cycle?

Isovolumetric ventricular relaxation

what is happening during phase 1 of the cardiac cycle?

ventricular filling

what sound is associated with phase 1 of the cardiac cycle?

S2 heart sound

describe the pressure of the heart during phase 1 of the cardiac cycle and what effect this results in?

• Pressure in atria > pressure in ventricle → blood pressure gradient has been created → AV valves open to allow blood to fill ventricles

what happens to the blood volume during phase 1 of the cardiac cycle?

Increase in volume since AV valve has opened

what happens to aortic pressure during phase 1 of the cardiac cycle?

Decrease in pressure of aorta but your aortic pressure still remains higher in pressure than the ventricles to allow for pressure gradient

what is phase 2 of the cardiac cycle?

atrial contraction or atrial systole

what sound is associated with phase 2 of the cardiac cycle?

S2 sound

what is happening during phase 2 of the cardiac cycle?

Atrial contraction within ventricular diastole to finish process of filling ventricles with blood

what is happening with pressure in phase 2 of the cardiac cycle?

Left Atrial pressure slightly higher than ventricular pressure in order to push remaining volume in ventricles to the aorta

what wave on the ECG is associated with phase 2 of the cardiac cycle?

P-wave associated with increase in atrial pressure

what phases of the cardiac cycle are associated with systole?

• phase 3

• phase 4 (end of diastole start of atrial systole)

atrial systole

the contraction of the atria that helps to fill the ventricles with blood

ventricular systole

the contraction of the ventricles, which pumps blood into the systemic and pulmonary circuits

isovolumetric contraction

the period during ventricular systole when the ventricles contract with no volume change because all heart valves are closed

isovolumetric relaxation

the period during ventricular diastole when the ventricles relax with no volume change because all heart valves are closed

ventricular stroke volume (SV)

the amount of blood (mL) ejected per beat by the left ventricle into the aorta (or from the right ventricle into the pulmonary valve) * this assumes that all blood leaves the ventricle; so it is not precise in defects of heart

what is the definition of ventricular stroke volume in terms of echocardiography when assessing ventricular function?

(ventricular end-diastolic volume (EDV)) - (end-systolic volume (ESV))

end-diastolic volume (EDV)

the filled volume of the ventricle before contraction

end-systolic volume (ESV)

the residual volume of blood remaining in the ventricle after ejection

cardiac output formula

SV x HR

preload

the degree of stretch of the cardiac muscle fibers at the end of diastole

afterload

the resistance the ventricles must overcome to eject blood during systole

what produces the "lub" sound during S1?

the closure of the AV (mitral and tricuspid) valves at the beginning of ventricular systole; the energy from the decelerating blood flow is transmitted as vibrations through the heart tissue to produce the sound

what causes the "dub" sound during S2?

caused by the closure of the semilunar valves (aortic and pulmonary) during the beginning of ventricular diastole; rapid decleration of blood flow as these valves close cause vibrations

S3 heart sound

a low-frequency sound occurring in early diastole associated with rapid ventricular filling

S4 heart sound

a low-frequency sound occurring in late diastole associated with atrial contraction and the final phase of ventricular filling

murmurs

abnormal heart sounds caused by turbulent blood flow, often due to valvular insufficiency or stenosis

when do systolic murmurs occur?

during ventricular systole

when do diastolic murmurs occur?

during ventricular diastole

what is normally the cause of murmurs (systolic and diastolic)

aortic or pulmonary valve stenosismitral or tricuspid valve regurgitation

continuous murmurs

persist throughout the cardiac cycle, often indicative of conditions like paten ductus arteriosus (PDA)

functional murmurs

benign murmurs not associated with structural heart disease

what animal do we often find functional murmurs in?

young or very active animals

tricuspid valve stenosis

narrowing of tricuspid valve, impeding blood flow from the right atrium to the right ventricle during diastole

mitral valve stenosis

narrowing of the mitral valve, impeding blood flow from the left atrium to the left ventricle during diastole

tricuspid valve insufficiency/regurgitation

a condition where the tricuspid valve does not close properly, allowing blood to flow backward to the right atrium during ventricular systole

pulmonic stenosis

narrowing of the pulmonary valve, causing an obstruction to blood flow from the right ventricle to the pulmonary artery

aortic stenosis

narrowing of the aortic valve, causing an obstruction to blood flow from the right ventricle to the aorta

auscultation

listening to the heart sounds using a stethoscope to detect normal and abnormal heart sounds

echocardiography

ultrasound imaging of the heart to assess its structure and function, including valve abnormalities

electrocardiography (ECG)

recording the electrical activity of the heart to identify arrhythmias and other cardiac issues

phonocardiography

recording of heart sounds and murmurs using a sensitive microphone and recording device

radiography

X-ray imaging to assess the size and shape of the heart to detect conditions like heart enlargement or fluid accumulation

what heart sound is associated with phase 3 of the cardiac cycle?

S1 heart sound

what do we call phase 3 of the cardiac cycle?

isovolumetric ventricular contraction

what is happening during phase 3 of the cardiac cycle?

Left ventricular pressure increases, but there is not a change in the left ventricular volume

where will you see phase 3 of the cardiac cycle on an ECG?

Begins at start of QRS complex on ECG

what heart sound is associated with phase 4 of the cardiac cycle?

S1 heart sound

what do we call phase 4 of the cardiac cycle?

ventricular ejection or systole

what is happening during phase 4 of the cardiac cycle?

Pressure increases in pulmonary and aorta to eject blood from ventricles into systemic circulation

where will you see phase 4 of the cardiac cycle on an ECG?

Increase in pressure in pulmonary and aorta to eject blood from ventricles to circulation

what are points A to B representing in the cardiac cycle using the left ventricle pressure/volume loop?

ventricular filling and atrial systole

what is happening to pressure from point A-B in cardiac cycle using the left ventricle pressure/volume loop?

pressure of the left intraventricular will remain constant

what is happening to volume in points A-B in left ventricle/pressure loop?

The volume of the left ventricle will increase until the mitral valve closes at the end of point B

what does point A represent in the left ventricle volume/pressure loop?

the end of systolic volume

what does point B represent in the left ventricle volume/pressure loop?

end of diastolic volume

do points A-B represent systole or diastole in the left ventricular pressure/volume loop?

diastole

do points B-C represent systole or diastole on the left ventricular pressure/volume loop?

systole

what do points B-C represent in the cardiac cycle in the left ventricular volume/pressure loop?

Represents isovolumetric contraction

what happens to volume in points B-C of the cardiac cycle in the left ventricular pressure/volume loop?

Volume of left ventricular will remain constant

what happens to pressure in points B-C in the cardiac cycle of in the left ventricular volume/pressure loop?

Pressure in left ventricle will increase until the aortic valve opens

do points C-D in the left ventricular pressure/volume loop represent diastole or systole?

systole

what do points C-D represent in the cardiac cycle on the left ventricular pressure/volume loop?

Represents ventricular ejection

what happens to the volume with points C-D in the left ventricular volume/pressure loop?

Volume of left ventricle will decrease

what happens to the pressure from points C-D in the left ventricular volume/pressure loop?

Pressure in left ventricle will increase during period of ejection until the aortic valve closes

do points A-D in the left ventricular pressure/volume loop represent diastole or systole?

diastole

what do points A-D represent in the cardiac cycle on the left ventricular volume/pressure loop?

represents isovolumetric relaxation

what is happening in points A-D in terms of pressure on the left ventricular pressure/volume loop?

Aortic valve closes at point D, we have a decrease in left ventricular pressure and mitral valve will open

cardiac output

the amount of blood the heart pumps throughout the body per minute

what is another term for preload?

left ventricular end-diastolic pressure (LVEDP)

what determines the amount of ventricular stretch when discussing preload?

The amount of blood entering the ventricles determines the amount of stretch

what determines the amount of blood that will enter the left ventricle when discussing preload?

The amount of volume (blood flow) coming into the ventricles determined by pressure (ventricular pressure > atrial pressure)

When you have preload, you will have an increase in…

• Hypervolemia

• Regurgitation of cardiac values

what is another term for afterload?

systemic vascular resistance (SVR)

when you have afterload, what will there be an increase in?

• Hypertension

• Vasoconstriction

increased afterload equals…

increased cardiac workload (force of contraction)

what did Frank-Starling mechanism discover about increased afterload?

When the afterload is increased, the graph will shift right and there will be a decrease in stroke volume of the heart and weaker contractions

what did Frank-Starling mechanism discover about decreased afterload?

When afterload is decreased, the graph will shift left and there will be an increase in stroke volume of the heart and stronger contractions

S1 heart sound

AV valves (mitral valve) closing →(lub)

S2 heart sound

Closure of semilunar valves (pulmonic and aortic valves) → (dub)

what heart sounds are normal to hear in dogs and cats?

S1 and S2

what heart sounds are abnormal (pathological) to hear in dogs and cats?

S3 and S4

what heart sounds are normal (physiological) to hear in horses?

S3 and S4

heart sounds

physiological noises generated by the oscillation of blood (turbulent flow) and vibration of muscles and valves; valves are NOT the source of the heart sound

where would you place your stethoscope if you wanted to listen to Bicuspid/Mitral/Left AV valve?

Left 5th intercostal space, around the costal-chondral junction

where would you place your stethoscope if you wanted to listen to Aortic Valve?

Left 4th intercostal space dorsal to mitral valve, usually the level of the point of the shoulder

what heart sound is loudest when listening for Bicuspid/Mitral/Left AV valve?

S1 heart sound

what heart sound is loudest when listening to the aortic valve?

S2 heart sound