cardiac cycle + heart sounds

What is the cardiac cycle

 the period bwt one heartbeat and the next 

What are heart valves + functions ? 

To ensure unidirectional blood flow ( forward flow + X backward flow ) during the separate phases of systole + diastole of atria + ventricles 

2 sets of valves: 

1. Atrioventricular 

2. Semilunar 

Opening mechanism of valves: pressure behind  > pressure in front 

Closing mechanism of valves: pressure behind < pressure in front

Structures preventing valves from flipping inside out

Type of valve	Method
AV valve	Chordae tendinae + papillary muscles
Semilunar valve	Leakproof seam

Events in the cardiac cycle: 

Phases	Phenomenon
Ventricular diastole	Ventricles filled w/ blood  Passive filling ( all chambers in diastole )  Active filling ( atria contract )
Isovolumetric ventricular contraction	Ventricles contract + all valves closed  → pressure↑
Ventricular ejection	Pressure forces blood past semilunar valves
Isovolumetric ventricular relaxation	Pressure falls ( initially isovolumetric ) → AV valves open + filling begins again

States of AV and semilunar valves during different events of cardiac cycle

Phases	State of AV valve	State of semilunar valves
Ventricular diastole	Open	Closed
Isovolumetric ventricular contraction	Closed	Closed
Ventricular ejection	Closed	Open
Isovolumetric ventricular relaxation	Closed	Closed

Relationship bwt electrical activity + pressure and volume changes in cardiac cycle 1

Electrical activity	Pressure changes	Volumetric changes
At diastole + AV valves open	Atrial + ventricular pressure increases slightly → passive filling w/ blood	Ventricular volume increases rapidly
SA node fires → atrial depolarisation ( P wave )   PR segment: AV node delay	Atria contracts → more blood enters ventricle ( active filling w/ blood )	Ventricular volume increases slowly  until reaches end diastolic volume

Relationship bwt electrical activity + pressure and volume changes in cardiac cycle 1

Electrical activity	Pressure changes	Volumetric changes
Action potential travels through AV node in the septum + spreads to the myocardium through bundle of His ( QRS complex )	Ventricle contracts → increases pressure > atrial pressure → AV valve closes → ventricular pressure continues to increase → isovolumetric contraction	AV valve + semilunar valve still closed → volume X change
	Ventricular pressure > aortic pressure → semilunar valve opens	Volume decreases as blood is pumped out ( stroke volume ejected  + achieved end-systolic volume )
Ventricular repolarization when AP signal is over	Ventricles relax → pressure decreases < aortic pressure → aortic valve closes	Ventricular volume remains the same bc all valves are closed   → isovolumetric relaxation

Cardiac cycle terminology and defintions

Terminology	Definition
End-diastolic volume	Volume of blood in ventricle when filling is complete
End-systolic volume	Volume of blood remaining in ventricle
Stroke volume	Volume of blood pumped out by each ventricle per beat
Ejection fraction	proportion of EDV pumped out in each heartbeat
Afterload	Pressure against which the heart needs to work to eject blood during systole

What are the different heart sounds

sound produced by turbulent blood flow caused by closure of valves ( specific cardiac event )

Heart sounds	Sound	Produced by	Timing
First	‘Lub’	Closing of AV valves	Beginning of systole
Second	‘ Dub’	Closing of aortic + pulmonary valves	End of systole
Third		Recoil of blood from ventricular wall	End of rapid filling phase in early diastole
Fourth		Strong pathological (?) atrial contraction	Late diastole

what are heart murmurs + mechanism

Mechanism	Definition
Regurgitation	Valves X close tightly  → blood flows in resulting gaps in wrong direction
Stenosis	Passages w/ valves decrease in size  → correct blood flow in right direction impeded

sounds from turbulent blood flow at all times

Indication of pathology by type + timing of murmurs

Type of heart murmurs	Pathology
Lub whistle dub	Aortic stenosis
Lub swish dub	Mitral regurgitation
Lub dub swish	Aortic regurgitation
Lub dub whistle	mitral stenosis
Whistle	Patent ductus arteriosus

what is auscultation

Auscultation: positioning stethoscope at diff positions for listening to diff valves