Cardiac Valve defects Flashcards
Cardiac valve defects may be incompetent (regurgitant), stenosed or both. Abnormal valves produce turbulent flow which can be heard as a murmur on auscultation; a few murmurs are also felt as a thrill on palpation.
What is the S1 heart sound?
- closure of mitral + tricuspid valves at start of isovolumetric contraction
- VP > AP -> so AV valves close
- valves open during end of diastole
- soft if long PR or mitral regurgitation
What is the S2 heart sound?
- closure of aortic + pulmonary valves
- AortaP + Pulmp > ventricularp -> semilunar valves close
- splitting during inspiration is normal
What is the S3 heart sound?
- third heart sound - ‘ventricular gallop’
- ‘kentucky gallop’ - (S1 - Ken, S2 - tuck, S3 - y)
- caused by diastolic filling of ventricle
- considered normal if < 30 yrs old (may persist in woman up to 50y)
- heard in left ventricular failure (eg. dilated cardiomyopathy), constrictive pericarditis (aka pericardial knock) and mitral regurgitation
What is the S4 heart sound?
- occurs just before S1 only if pathology present
- ‘atrial gallop’
- caused by atrial contraction against a stiff ventricle
- may be heard in aortic stenosis, HOCM + hypertension
- in HOCM a double apical impulse may be felt as a result of a palpable S4
S3 and S4 may occur together in what is known as a quadruple gallop or may merge to produce a summation gallop S7
What are examples of ejection systolic murmurs?
- aortic stenosis
- pulmonary stenosis, HOCM
- ASD, Fallot’s
What are examples of pansystolic/holosystolic murmurs?
- mitral/tricuspid regurgitation (high-pitched + ‘blowing’ in character)
- VSD (‘harsh’ in character)
What are examples of late systolic murmurs?
- mitral valve prolapse
- coarctation of aorta
What are examples of early diastolic murmurs?
- aortic regurgitation (high pitched + ‘blowing’ in character)
- Graham-Steel murmur (pulmonary regurg, again high pitched + ‘blowing’ in character)
What are examples of mid-late diastolic murmurs?
- mitral stenosis (‘rumbling’ in character)
- austin-flint murmur (severe aortic regurgitation, again rumbling in character)
What is an example of a continuous machine-like murmur?
patent ductus arteriosus
What are the signs and symptoms of aortic stenosis and what is characteristic of this specific murmur?
- ejection systolic murmur - right 2nd ICS
- crescendo-decrescendo
- radiates to carotids bilaterally
- pitch = medium
- symptoms*: dyspnoea, angina, exertional syncope, systemic emboli, sudden death
- signs: slow rising carotid pulse, narrow pulse pressure, displaced, thrusting apex beat, soft S2 (absent S2 in severe disease), brachio-radial delay, late + weak pulse
*(SAD = syncope, angina, dyspnoea)
What are common causes of aortic stenosis?
- cusp calcification of bicuspid aortic valve - calcification develops approx 30yrs w/ progressive stenosis, thought that years of turbulent flow across abnormal valve disrupt endothelium and collagen matrix of leaflets, resulting in gradual calcium deposition
- age-related calcification of the normal tricuspid aortic valve - normal aortic valve is tricuspid where about 1-2% of pop have a bicuspid valve, it is thought cumulative wear + tear of valve motion over many years leads to endothelial + fibrous damage, causing calcificiation of an otherwise normal valve
- post rheumatic fever valve disease (rare in UK)
- congenital: William’s, Turner’s
What is the pathophysiology of aortic stenosis?
- blood flow across aortic valve is impeded during systole
- as a consequence, significantly elevated left ventricular pressure is necessary to drive blood into aorta
- since AS develops over chronic course, the LV is able to compensate by undergoing hypertrophy in response to the higher systolic pressure it must generate to maintain output
- ie. gradual development of LV outflow obstruction causes gradual pressure overload of LV + results in compensatory LV hypertrophy
- however, hypertrophy reduces compliance of ventricle -> resulting elevation of diastolic** pressure -> **LA hypertrophy in order to fill the ‘stiff’ LV
as a consequence of the compensatory changes, there is a long asymptomatic period - eventually, the heart decompensates and there is deterioration in cardiac function leading to development of symptoms.
What are relevant investigations for aortic stenosis?
- transthoracic echocardiogram - best for initial + subsequent evaluation of AS, used when there is an unexplaine dsystolic murmur, a single second heart sound, a history of a bicuspid aortic valve or symptoms that might be due to AS -> it shows elevated aortic pressure gradient
- ECG - may show LVH and absent Q waves, AV block, hemiblock or bundle branch block
- cardiac catheterisation - useful for diagnosis only when echo is inconclusive, shows elevated aortic pressure gradient
What does left ventricular hypertrophy look like on an ECG?
- Results in increased R wave amplitude in the left-sided ECG leads (I, aVL and V4-6) and increased S wave depth in the right-sided leads (III, aVR, V1-3)
- The most commonly used criteria are the Sokolov-Lyon criteria (S wave depth in V1 + tallest R wave height in V5-V6 > 35 mm)
- ST segment depression and T wave inversion in the left-sided leads: AKA the left ventricular ‘strain’ pattern
- Left axis deviation also common
