What valves are closing when the first heart sound is produced?
Atrio-ventricular valves (Tricuspid and mitral)
What valves are closing when the sound heart sound is heart?
The aortic and pulmonary valves
What stage of the heart cycle is signified by the first heart sound?
The beginning of systole
What stage of the heart cycle is signified by the second heart sound?
The beginning of diastole
Which part of the heart cycle is shortened when the heart rate increases, and what is a consequence of this?
Diastole, means that a very fast beating heart does not remain relaxed enough to allow complete filling of the ventricles before the next contraction
How much of the ventricular filling is caused by atrial contraction?
Around 20% - the remaining 80% is filled by direct blood flow from the SVC and IVC through the atria into the ventricles
On the JVP waveform, what causes the a, c and v waves?
- Atrial contraction
- Beginning of ventricular contraction as the tricupsid valve bulges back into the right atrium
- End of ventricular contraction when blood is entering the atria but the tricupsid valve is still shut
On the JVP waveform what causes the x and y descents?
- Contraction of the ventricles, the blood empties from the ventricles so the tricupsid valve no longer bulges into the atrium
- Opening of the tricuspid valve, allowing blood to flow from the atria to the ventricles
What occurs during the period of rapid ventricular filling?
The pressure in the atria is higher than the diastolic ventricles so the AV valves open allowing blood to flow rapidly into the ventricles and lasts about 1/3 the length of diastole
What is the period of isovolumetric contraction?
It is immediately after the beginning of ventricular contraction where the sharp rise in ventricular pressure causes the AV valves to close.
There is then a period of increasing pressure due to ventricular contraction but the pressure is not enough to open the aortic and pulmonary valves.
What pressures must be inside the ventricles to open the aortic and pulmonary valves?
Aortic valve - >80mmHg
Pulmonary valve - > 8mmHg
Which 1/3 of systole does the majority of blood get ejected from the heart, and what is this period called?
The first 1/3 (70% of the ventricular volume is ejected)
Called the period of rapid ejection
Describe the period of isovolumetric relaxation
The sudden onset of ventricular relaxation allows the ventricular pressures to drop rapidly.
The larger pressures in the arteries push blood back towards this lower pressure, causing the semilunar valves to snap shut.
During this period, the intraventricular pressures decrease rapidly back to their low diastolic pressures.
How much blood is normally found within each ventricle at the end of diastole, and what is this volume called?
Around 110-120mL per ventricle
Called the end-diastolic volume
How much blood is pumped out each ventricle during diastole and what name is given to this measurement?
This is known as the stroke volume output
How much blood is left in each ventricle at the end of systole and what is this called?
Known as the end systolic volume
What is the ejection fraction?
The fraction of the end-diastolic volume that is ejected from the heart - usually around 60%
What 2 mechanisms can be used to increase the stroke volume output?
Increase the end-diastolic volume - increase blood flow into the ventricles
Decrease the end-systolic volume - strong heart contraction
What is the most common cause of aortic stenosis?
Calcific aortic valvular disease
What are the risk factors for calcific aortic valvular disease?
Elevated lipoprotein and LDL
What is the process of calcific aortic valvular disease?
Subendothelial thickening with adjacent fibrosis, which may contain lipoproteins and then calcify, increasing the stiffness of the valve
What other conditions are associated with a bicuspid valve?
What infection is associated with aortic stenosis, usually with mitral valve disease
Rheumatic fever caused by Steptococcus pyogenes
What are some differential diagnoses for aortic stenosis?
Subvalvular diaphragm or ridge
What is the triad of symptoms associated with aortic stenosis?
What clinical signs are seen with aortic stenosis?
- Sinus rhythm, slow rising pulse, low volume
- Systolic thrill
- Not displaced, sustained
- Ejection click; A2, S4
- Systolic, low pitched, ejection and radiates to carotids
What findings might be seen on a CXR of a patient with aortic stenosis?
- Relatively small heart with prominent, dilated ascending aorta - post stenotic dilatation
- Calcification of the aortic valve
What ECG changes may be seen in aortic stenosis?
Signs of LV hypertrophy and L atrial delay
Left ventricular strain pattern - Depressed ST segment and T wave inversion in 1, aVL, V5 and V6