Aortic valve disease encompasses 3 diseases:
- Aortic stenosis
- Aortic regurgitation
- Aortic sclerosis
🦴 Anatomy
The aortic valve is a semilunar valve located between the left ventricle and the ascending aorta/aortic orifice. It consists of 3 cusps - a right, left and posterior cusp.
It’s orientation is oblique (down and to the right). It is located at the level of the 3rd intercostal space behind the sternum.
We listen to the aortic valve over the 2nd intercostal space, right sternal border as we auscultare where the blood is ejected to once the valve opens, not directly over the valve.
The aortic valve opens during ventricular systole which lasts approximately 0.3s long. This allows blood to be pushed into the aorta and systemic circuit. During diastole (lasting 0.4s) the aortic valve closes and blood passively pools in the aorta as well as the ventricles.
Aortic stenosis refers to the obstruction of blood flow through the aortic valve due to aortic valve fibrosis and calcification → narrowing of the valve orifice.
It is the most prevalent valvular disease of the heart.
Pathophysiology
It was previously believed to be normal to have aortic stenosis due to wear and tear, however, we now recognise it as pathological damage to the valvular endocardium. Damage to the endocardium of the valves leads to inflammation similar to atherosclerosis → fibrosis and calcium deposition on the valve itself. Eventually these deposits and fibrosis leaf to progressive fibrosis.
The similar process happens in rheumatic heart disease except the trigger for inflammation is an autoimmune inflammatory reaction that is triggered due to a prior streptococcal infection.
Over time this stenosis causes increased pressure → left ventricular hypertrophy to maintain a normal afterload irrespective of the pressure overload. However, as the stenosis worsens, the left ventricular wall stress increases and this leads to systolic dysfunction and systolic heart failure.
Let’s look at some of the causes for aortic stenosis, which we can divide into 3 categories:
- Supravalvular aortic stenosis
- William’s syndrome - it is a developmental disorder. It often leads to a long supravalvular aortic narrowing which can obstruct blood flow.
- Valvular aortic stenosis
- Degenerative calcification - this is the most common cause (80% of cases) and was described above.
- Bicuspid aortic valve - the most common cause in young people. A congenital bicuspid aortic valve is more common in people with Turner syndrome and coarctation of the aorta (birth defect in which the aorta is narrower than usual).
- Rheumatic heart disease - as mentioned above. It is the most common cause in developing countries.
- Subvalvular
- Hypertrophic obstructive cardiomyopathy (HOCM) - interventricular septum hypertrophy obstructs blood flow in the left ventricle at a level below the aortic valve.
⚠️ Risk factors
- Smoking
- Hypertension
- High LDL levels
- Rheumatic fever
- Advanced age (>60 years old)
- Congenital bicuspid aortic valve
- CKD - 55% of cases occur in dialysis patients over 65 years old.
😷 Presentation
It is often asymptomatic.
- Exertional dyspnoea
- Fatigue
- Exertional chest pain
- Exertional syncope
- Ejection systolic murmur
- Heart failure symptoms
- Diminished S2 - soft or absent due to decreased mobility of the valve leaflets.
- S1 - due to closure of the mitral and tricuspid valves.
- S2 - due to closure of the aortic and pulmonary valves.
- S3 - aka the ventricular gallop. It is produced by the blood striking the left ventricle during cardiac diastole.
In aortic stenosis, we have a crescendo-decrescendo pattern systolic murmur peaking in mid-systole. The murmur radiates to the carotid as well. It is loudest at the right upper sternal border.
- Narrow pulse pressure - the normal pulse pressure is 40mmHg (120mmHg - 80mmHg). It is the difference between systolic pressure and diastolic pressure. A narrow pulse pressure is when the pulse pressure <25% of the systolic BP.
- Slow rising pulse (parvus et tardus) - the rate of ejection of blood into the aorta is decreased so the ejection period is prolonged and the amplitude of the pulse is diminished. This is often present in the carotid artery.
- S4 heart sound - present in severe left ventricular hypertrophy with aortic stenosis.
- Thrill - a vibratory sensation felt on the skin overlying an area of turbulence, indicating a loud heart murmur.
- Left ventricular hypertrophy or failure
🔍 Investigations
🥇 🏆 First-line and gold standard investigation is a transthoracic echocardiogram.
ECG may also show signs of left ventricular hypertrophy due to pressure overload. This is seen as:
- Increased QRS voltage
- Left axis deviation
- Poor R-wave progression
- Absent Q waves
CXR - may be used to assess for pulmonary congestion, cardiomegaly or aortic calcification.
🧰 Management
Intervention is not always indicated, but is indicated in the following patients:
- All symptomatic patients
- Asymptomatic patients with LVEF <50%
- Asymptomatic patients with LVEF >50% who are physical active but have symptoms/fall in BP during exercise testing
- Asymptomatic patients with LVEF >50% with following risk factors:
- Aortic valve peak velocity >5.5m/s
- Severe calcification and peak velocity progression >0.3m/s
- Markedly elevated BNP without other explanation
- Severe pulmonary hypertension
The intervention options include surgical aortic valve replacement (SAVR) or transcatheter aortic valve implantation (TAVI):
- TAVI is favoured in high-risk patients >75 years old. A new valve is placed without removal of the damaged heart valve.
- SAVR is favoured in low-risk patients <75 years old.
In children with no calcification or in adults not fit for surgery, we can do balloon valvuloplasty in which a balloon stretches the aortic valve to improve symptoms.
⚠️ Beware of using nitrates in patients with aortic stenosis as it may precipitate syncope.
Aortic regurgitation is the leakage of blood through the aortic valve from the aortic sinus back into the left ventricle during diastole. This is due to failure of the aortic valve to completely close. Eventually, blood will back up from the left ventricle into the left atrium → pulmonary congestion.
It can be referred to as aortic valve insufficiency as well.
Pathophysiology
We can divide aortic regurgitation into valvular causes and non-valvular causes:
Valvular causes
Diseased aortic valve due to:
- Rheumatic heart disease - most common cause in the developing world.
- Age-related calcification
- Infective endocarditis - the most common cause of acute aortic regurgitation.
- Autoimmune disorders - such as RA and SLE.
- Libman-Sacks endocarditis
Non-valvular causes
These diseases cause distortion or dilation of the aortic root and ascending aorta. This then stretches the otherwise healthy leaflets, allowing for blood to flow through them as they fail to close completely.
- Congenital bicuspid aortic valve - affects both the valves and aortic root.
- Aortic dissection - common cause of acute aortic regurgitation as well.
- Spondylarthropathies - such as ankylosing spondylitis. The inflammatory processes from the spinal joints also have cardiac manifestations peculiarly enough.
- Hypertension
- Aortitis - due to syphilis, Behçet’s disease, Takayasu’s arteritis, reactive arthritis, ankylosing spondylitis.
- Connective tissue disorders
- Chest trauma
🔢 Classification
We can classify it as acute and chronic aortic regurgitation:
- Acute aortic regurgitation - this is a medical emergency. The left side of the heart acutely decompensates as it is unable to handle the sudden increase in the end-diastolic volume.
- Chronic aortic regurgitation - this is the aortic regurgitation that has progressed over months-years. The left side of the heart compensates with the increased end-diastolic volume without symptoms, however, it eventually reaches a point where it decompensates and presents with symptoms of congestive heart failure. Eventually the blood will back up into the pulmonary circuit → pulmonary congestion.
😷 Presentation
Acute aortic regurgitation
- Dyspnoea
- Cardiogenic shock - hypotension, tachycardia, pallor, faint peripheral pulses, raised JVP, altered mental status, low urine output.
- Basal lung crepitations - due to the pulmonary oedema.
- Soft S1 sound
- Cyanosis
- Tachypnoea
Chronic aortic regurgitation
- Fatigue
- Weakness
- Orthopnoea
- Paroxysmal nocturnal dyspnoea
- Raised JVP
- Basal lung crepitations
- Soft/absent A2 component of S2 (aortic valve closure)
- Displaced apex beat
- Early diastolic murmur - as blood flows back during diastole. This is accentuated with the handgrip manoeuvre in which one clenches their fist forcefully until they fatigue. The murmur duration directly correlates with severity.
The best location to listen to the murmur is at the left parasternal region between the 2nd and 4th ICS. This is where stream of blood may be regurgitating into the left ventricle.
- Mid-late diastolic Austin-Flint murmur - this occurs in severe aortic regurgitation. It is heard best at the apex beat.
- Collapsing pulse
- Wide pulse pressure - due to a low diastolic pressure.
Some eponymous signs of aortic regurgitation are:
- Quincke’s sign - when the nail bed pulsates with each heartbeat.
- De Musset’s sign - head bobbing with each heartbeat.
- Traube’s sign - a pistol shot sound heard when the stethoscope is placed over the femoral artery during systole and diastole.
- Muller’s sign - uvular pulsation with each heartbeat.
🔍 Investigations
🥇 Once again, the first-line investigation is echocardiography to assess the severity. In patients with severe aortic regurgitation or with those that have an inconclusive echo, a cardiac MRI is indicated.
If non-invasive tests are inonclusive, we may opt for a invasive cardiac catheterisation and angiography.
- ECG may also support diagnosis.
- CXR can show cardiomegaly with chronic aortic regurgitation due to the compensatory hypertrophic response that occurs due to the increased EDV.
🧰 Management
We can slow aortic root dilatation and reduce the risk of progression by appropriately managing hypertension.
- B-blockers or ACEIs may be used.
This involves valve replacement. It is indicated in the following situations:
- Significant enlargement of ascending aorta
- Symptomatic aortic regurgitation
- Asymptomatic but:
- Poor LVEF (<50%)
- Left ventricular end-diastolic diameter >70mm or left ventricular end-systolic diameter >50mm
- Infective endocarditis refractory to medical therapy.
For asymptomatic patients with severe aortic regurgitation, they should be monitored annually. If the left ventricular end-diastolic/systolic diameters show significant changes then monitoring needs to happen 3-6 monthly.
This is the senile degeneration of the aortic valve due to old age. We can hear it on auscultation with an ejection systolic murmur less intense than that of aortic stenosis, with no carotid radiation and normal pulses and S2 sound.