Valvular Disease Physiology Flashcards
What are the heart sounds?
The heart sounds are due to the valves closing.
What is the purpose of Chordae Tendini?
hold the valve in place, not to open and close that valve.
Explain some differences between systole and diastole?
Systole is shorter than diastole. Around 1/3 of the cycle is systole and 2/3 is diastole.
In tachycardia, diastole shortens in duration far more than systole so the sounds may be far closer together.
What is meant by valve stenosis?
- Stenosis means narrowing
During stenosis, the valve does not fully open and so there is a restriction of flow. This creates a pressure gradient across the valve and there is a higher pressure in the chamber behind the valve (LV in Aortic stenosis; LA in mitral stenosis), this can lead to a pressure overload.
What is meant by valve incompetence?
- Incompetence is also known as regurgitation or leaking.
In Regurgitation, the valve doesn’t close fully and so blood leaks back into the previous chamber. The heart is required to pump higher stroke volume to maintain forward cardiac output. This leads to a greater volume in the ventricle which means an increase in EDV. This will result in increased EF and could cause volume overload.
What is turbulence with respect to valvular physiology?
- Around stenosed or incompetent valves which causes a murmur in heart sounds. It is also visible on Doppler Echo.
- High flow may cause ‘innocent flow murmurs’ such as in children, fever, anaemia or pregnancy.
Explain some features of valvular heart disease?
- Used to be due to previous Rheumatic Fever (now uncommon except in NT)
- Most are due to degenerative conditions
- Can occasionally be congenital
- Mild & moderate lesions can be asymptomatic
- Cardiac compensation is effective so even severe lesions can be asymptomatic for many years.
- Cardiac compensation eventually fails (ventricular enlargement and irreversible failure)
- Symptoms such as shortness of breath are generally a late feature but are indications of poor prognosis.
- Irreversible LV changes occur about the time symptoms develop in regurgitation
- In Aortic stenosis, symptoms indicate time to intervene and LVH changes usually regress.
How is valvular disease assessed/diagnosed?
Assessment is by:
- history esp. of shortness of breath - examination - murmur, pulse - ECG - Echocardiography - most important (diagnosis, severity, Ventricular size & function, atrial size, pulmonary artery pressure) - Echo can show LV changes before they are irreversible - trigger for intervention in AR, MR
What are some various interventions of valvular disease?
- First successful heart valve operation was ‘closed’ mitral valvotomy in 1948 (involved cutting a hole in the atrium and breaking the scar up with finger and then repairing)
- Valve replacements have been occurring since 1958 (can be metal and plastic; bioprostheses- pig valves, calf pericardium, human)
- Valve repair especially of mitral valve
- Balloon valvotomy
- Stent valves - delivered percutaneously
Explain features of aortic stenosis?
- Progressive narrowing or aortic valve - fibrosis, calcification
- Reduction in valve area (Normal: >2.5 square cm; Severe: 50mmHg)
What is the left ventricular response during aortic stenosis?
During Aortic Stenosis there is a left ventricular response.
- pressure overload of LV
- Concentric hypertrophy
- walls thicken
- thick walls are stiffer- less compliant
- diastolic dysfunction
- increased LVEDP required to fill LV
- Atrial contraction important to fill LV
- LV changes usually reverse after surgery
What are the symptoms and progression of aortic stenosis?
Aortic Stenosis is the most common of valve lesions and is usually ‘calcific’ in older patients (occasionally congenital or rheumatic). It is very well tolerated with no symptoms until the stenosis is severe. Development of symptoms is a trigger for valve surgery.
What are the systolic murmurs of aortic stenosis?
Systolic Murmurs:
- Due to turbulence at pressure gradients.
Aortic Stenosis
- narrowed aortic valve
- gradient: LV to Ao
- Pressure gradient rises during systolic ejection
Murmur is crescendo decrescendo - ejection systolic
- Harsh, rough sound (Similar to a lawnmower)
What are the features of aortic regurgitation?
- Aortic leaflets are damaged: endocarditis, Rheumatic Fever
- Aortic root dilated so leaflets don’t close : Marfan’s syndrome, aortic dissection, collagen vascular disorders, syphilis.
- part of each stroke volume leaks back into the LV during diastole
- to maintain normal cardiac output, LV has to pump greater stroke volume each beat
- Volume overload
- Increased EDV, Increased EF, Normal ESV
- Increased SV, Increased pulse pressure (bounding pulse)
- Reduced aortic diastolic pressure (collapsing pulse)
- Early Diastolic murmur (third ‘blowing’ sound after lubdub)
- Well tolerated with no symptoms if mild or moderate AR.
If it is prolonged then there can be severe aortic regurgitation and eventual decompensation.
- LV Diastolic volume increases ++
- LV function decreases
- LV Systolic Volume Increases
- Coincides with development of symptoms
- Decompensation changes are irreversible.
What are some causes of mitral regurgitaton?
- Myxomatous degeration (Mitral valve prolapse)
- Ruptured chordae tendinae (flail leaflet
- Infective Endocarditis (Bacteria infection of the heart valve- usually staph from the skin, or strep from the mouth)
- Myocardial infarct - rupture papillary muscle
- Rheumatic fever
- Collagen Vascular disease
- Cardiomyopathy - change in ventricular shape
