Lecture 12: Cardiac cycle 2, Heart Sounds and Performance Flashcards
What causes heart sounds?
Rapid acceleration (or deceleration) of blood
Valve closing and opening sounds
Ventricular filling sounds (gallops)
What is S1?
First heart sound
Caused by AV valve closure (mitral and tricuspid)
What is S2?
Caused by semilunar valve closure
Aortic and pulmonic
What is splitting?
When the corresponding right and left sided valves do not close exactly simultaneously
Relationship of aortic and pulmonic valve closure varies with respiration
-inspiration augments systemic venous return so increases RV stroke volume and prolongs RV ejection
-this delays pulmonic valve closure so you can hear splitting upon splitting
How do you hear splitting?
Upon inspiration, the pulm valve closes later than aortic valve because there is more venous return
When you hear splitting on expiration, that means there may be LBBB because aortic valve is closing later than pulm valve
What is S3?
Rapid early ventricular filling Low frequency 160ms after S2 NOT NORMAL unless in young adults If heard, can indicated accentuated early ventricular filling or disordered diastolic compliance
What is the significance of hearing S3?
Problem with ventricular systole (3 syllables)
Can indicate accentuated early ventricular filling
Or disordered diastolic compliance
Means that there may be a volume overload
What is S4?
Accentuated late diastolic filling due to atrial contraction
Low frequency
100 ms before S1
Not normally heard
What is the significance of hearing S4?
Problem with ventricular diastole (4 syallables)
Can indicate abnormal diastolic compliance (so you need that extra atrial kick)
Indicative also of accentuated atrial contribution to ventricular filling
What causes murmurs?
Turbulent (high velocity) blood flow
Flow velocity > turbulence threshold predicted by Reynold
Relationship will produce murmurs
Normal blood flow in cardiac chambers and vessels is
Laminar and silent
Higher the velocity, the greater the frequency
Cardiac murmurs and vascular bruits
What is the significance of turbulent flow?
Occurs if flow velocity exceeds critical value predicted by Reynolds relationship
Turbulence creates vibrations that are perceived as sound
What are types of murmurs?
- Systolic
2. Diastolic
What are the characteristics of systolic murmurs?
Associated with ventricular ejection and can indicate
i. outflow tract obstruction ii. AV valve regurgitation iii. Interventricular communications iv. Aortic valve stenosis (only here S1 because aortic valve is too stenotic) v. Atrial septal defect
What are the characteristics of diastolic murmurs?
Associated with ventricular INFLOW and can indicate
i. Semilunar valve regurgitation ii. AV valve obstruction iii. aortic valve regurgitation
What are the principal parameters that define cardiac performance?
- Heart rate
- stroke volume
- systemic arterial pressure
- Left atrial pressure
What are the circulatory performance parameters?
- Cardiac output
- systemic arterial pressure
- Systemic and pulmonary venous pressure
- needs to be adequate to achieve satisfactory diastolic filling of ventricles
What are the three paradigms for assessing cardiac performance?
- pumping performance (how the heart does in pumping blood around)
- cardiac muscle performance
- chamber function (the integration of all variables that characterize and influence cardiac performance)
What is the cardiac output?
SV x HR = CO
What determines stroke volume?
- end diastolic volume (preload)
- volume available to eject
- determinant of available contractile force
- determined by ventricular end diastolic pressure
- force opposing ventricular ejection (afterload
- resistance to ejection that must be overcome to eject
- determines the contractile force required to shorten and eject
- determined by great vessel pressure
- contractility
What is the significance of preload and afterload?
The two most important operating parameters that affect ventricular performance
What is preload?
The force available to distend myocardium at end diastole
Determines end diastolic sarcomere length
Derived from ventricular diastolic pressure
The underpinning of the Frank-Starling relationship
What is the effect of preload on cardiac muscle shortening?
At constant aortic pressure and heart rate the work of the heart is capable of being varied within wide limits by variations in venous pressure
The most direct factor influencing the quantity of blood sent out from the ventricle is the intraventricular pressuWhat are the two parameters that preload affects to determine cardiac pumping performance?re by which the ventricle is distended during diastole
What is the effect of venous pressure on cardiac output?
The higher the venous pressure of blood (or return), the higher the output of blood (CO)
That’s how RV and LV are regulated to pump same amount
What is the effect of preload on intrinsic cardiac muscle contractile performance?
Dependence of peak isovolumic pressure on ventricular volume
More volume = more pressure = greater cardiac output
What are the two parameters that preload affects to determine cardiac pumping performance?
- ventricular volume at end diastole that is available to be ejected
- the contractile force that myocardium is able to develop
The greater the volume, the greater the force (regardless of compliance)