kembara Xtra - Medicine - Aortic Valvular Stenosis

kembara Xtra - Medicine - Aortic Valvular Stenosis 
​BASICS DESCRIPTION

The narrowing of the aortic valve region known as aortic stenosis (AS) prevents the left ventricle's (LV) outflow. A high death rate without surgical intervention is related with the development of severe obstruction or the advent of symptoms including syncope, angina, and congestive heart failure (CHF), despite the disease's lengthy asymptomatic latency phase.

EPIDEMIOLOGY
 
In Europe and North America, AS is the most prevalent primary valve disease requiring surgical intervention or catheter intervention, and its prevalence is rising as the population ages. Age at presentation as a cause:
Congenital conditions, rheumatic fever (RF), or degenerative calcification of the aortic valve are seen in people under the age of 30.
Prevalence
 Affects 1.3% of people aged 65 to 74, 2.4% of people aged 75 to 84, and 4% of people aged >84.
1-2% of people have an aortic valve that is bicuspid. An earlier onset of AS is predisposed by a bicuspid aortic valve.

PATHOPHYSIOLOGY AND ETIOLOGY
LV outflow blockage is caused by the progressive thickening and calcification of aortic leaflets. Increased afterload brought on by obstruction eventually results in decreased cardiac output.

To maintain cardiac output, an increase in LV systolic pressure is necessary, which causes concentric LV hypertrophy (LVH). While maintaining ejection fraction, the compensating LVH has a negative impact on heart performance.
- LVH reduces capillary ingrowth into hypertrophied muscle and compresses coronary arteries, which reduces coronary blood flow during diastole.
- LVH decreases ventricular compliance, causing diastolic dysfunction.
To increase preload and sustain stroke volume in the presence of diastolic dysfunction, the left atrium (LA) needs to contract more forcefully. Acute degeneration can result from atrial fibrillation's loss of LA contraction.
Due to the existence of interstitial fibrosis, diastolic dysfunction may continue even after the AS has been resolved.
Angina: a rise in LV pressure-related myocardial demand. LVH impairs the delivery of oxygen to the myocardium.
Syncope (exertional): There are a variety of causes, including arrhythmias, a fixed obstruction to the LV outflow, an aberrant baroreceptor response, or most commonly, a failure to properly increase blood pressure.
Heart failure: When the LVH eventually loses the ability to counteract an increase in afterload, the LV pressure and volume rise, and the pulmonary and LA pressures also rise.
Aortic valve degeneration caused by calcification: The mechanism involves both atherosclerotic alterations in the valve tissue and mechanical stress on the valve leaflets.
Mechanical stress is more likely to affect bicuspid valves.
- Inflammatory response in early lesions: subendothelial buildup of oxidized LDL, macrophages, and T cells
- Fibroblasts become osteoblasts as the disease progresses; these osteoblasts produce the proteins osteopontin, osteocalcin, and bone morphogenic protein-2 (BMP-2), which controls the calcification of leaflets.
Congenital conditions include unicuspid valves, bicuspid valves, tricuspid valves with fusion of commissures, and hypoplastic annuli. RF conditions include chronic scarring with commissure fusion.

Congenital unicommissural valve or bicuspid valve: The majority of instances were discovered during childhood.
- Bicuspid valve: compared to tricuspid valve (6th to 8th decade), predisposes to the development of AS earlier in adulthood (4th to 5th decade).
In the United States, the prevalence of chronic rheumatic valvular disease has considerably decreased.
– The majority of instances involve mitral valve disease.
The most frequent cause of acquired AS in the US is degenerative calcific alterations.
– Risk factors include hypercholesterolemia, hypertension, smoking, male gender, age, and diabetes mellitus and are comparable to those for coronary artery disease (CAD).
CONDITIONS OFTEN Associated with
CAD (50 percent of patients)
As a result of blockage brought on by AS and hypertension, the left ventricle becomes "doubleloaded" in 40% of individuals with hypertension.
Aortic insufficiency (frequent in rheumatic illness and calcified bicuspid valves)
95 percent of patients with AS brought on by RF also have mitral valve dysfunction.
CHF and LV dysfunction

 Acquired von Willebrand disease: In 20% of AS patients, bleeding (ecchymosis and epistaxis) is caused by impaired platelet function and reduced vWF.
The severity of AS is directly correlated with the severity of coagulopathy.
Arteriovenous malformations of the gastrointestinal tract (AVMs) Cerebral or systemic embolic events brought on by calcium emboli

DIAGNOSIS HISTORY
Angina, syncope, and heart failure are the main symptoms.
The most prevalent symptom is angina. Exertion frequently causes syncope. Fatigue, orthopnea, paroxysmal nocturnal dyspnea, exertional dyspnea, and shortness of breath are all signs of heart failure.
Heart palpitations
Neurologic events resulting from embolization, such as transient ischemia attack or cerebrovascular accident
Patients with geriatric conditions may have modest symptoms including weariness and exertional dyspnea.
Note that symptoms most frequently manifest when the aortic valve area is less than 1 cm2, the jet velocity is greater than 4.0 m/s, or the mean transvalvular gradient is less than 40 mm Hg. Symptoms do not always correlate with the severity of AS.


Auscultation: A harsh, systolic crescendo-decrescendo murmur that radiates into the carotid arteries can be heard best at the second right sternal border during a physical examination. The severity of the stenosis is correlated with the murmur peak; a later murmur peak indicates a more severe stenosis.
- An accompanying aortic insufficiency is suggested by a high-pitched blown diastolic murmur.
- A2 is missing or paradoxically split in S2. Note: Severe AS is consistently excluded by normally split S2.
Other concomitant symptoms include pulsus parvus et tardus, or a reduced and delayed carotid upstroke. - S4 because the left ventricle has stiffened. Findings of CHF include pulmonary and/or lower extremities edema and LV heave.

DISTINCTIVE DIAGNOSIS
Mitral regurgitation: A high-frequency, pansystolic murmur that is typically felt in the axilla but is most audible at the apex.
The optimum place to hear the systolic crescendo-decrescendo murmur is at the left sternal border, though it can also travel to the axilla in cases with hypertrophic obstructive cardiomyopathy. Murmur intensity increases when getting up from a crouch or when performing the Valsalva technique.
In 50–65% of cases of discrete fixed subaortic stenosis, cardiac deformities such patent ductus arteriosus, ventricular septal defect, and aortic coarctation are present.
Williams syndrome, homozygous familial hypercholesterolemia, and aortic supravalvular stenosis


DETECTION & INTERPRETATION OF DIAGNOSIS
Initial examinations (lab, imaging)
Chest x-rays (CXR) in compensated, isolated valvular AS may be normal
- Poststenotic dilatation of the ascending aorta and calcification of the aortic valve (visible on lateral PA CXR) - Boot-shaped heart reflecting concentric hypertrophy
ECG: Usually normal (ECG is nondiagnostic), but may also exhibit LVH, LA enlargement, and atypical ST- and Twaves.
Initial workup for echo indications
Doppler echocardiogram: the main test for identifying and assessing AS 
Assesses LV wall thickness, size, and function, as well as pulmonary artery pressure - in cases of known AS and evolving signs and symptoms
Echo findings include: - Aortic valve thickening, calcification - Reduced aortic valve area - Transvalvular gradient across aortic valve - LVH and diastolic dysfunction - LV ejection fraction - In known AS and pregnancy due to hemodynamic alterations of pregnancy
- Wall-motion anomalies that may indicate CAD
- Check for concurrent mitral valve disease or aortic insufficiency.
AS severity based on echo values: Stage A (at risk): bicuspid or trileaflet valve; mean pressure gradient: 0 mm Hg; jet velocity: 2 m/s Stage B (progressive): bicuspid or trileaflet valve
 Mild: jet velocity 2.0 to 2.9 m/s; mean pressure gradient: 20 mm Hg
Moderate: mean pressure gradient of 20–40 mm Hg; jet velocity of 3.0–3.9 m/s - Stage C (asymptomatic severe AS):
AVA 1.0 or AVAi 0.6 cm2/m2; mean pressure gradient: 40 to 60 mm Hg; jet velocity: 4 to 5 m/s; C1 (without LV dysfunction)
Stage D (symptomatic severe AS): AVA 1.0 or AVAi 0.6 cm2/m2; mean pressure gradient: 40 mm Hg; jet velocity: 4 m/s - C2 (with LV dysfunction):
AVA 1.0 cm2, mean pressure gradient >40 mm Hg, jet velocity >4 m/s, and D1 (high gradient)
AVA 1.0 cm2, mean pressure gradient 40 mm Hg, jet velocity 4 m/s; D2 (low flow/low gradient with reduced EF 50%)
AVA 1.0 cm2, AVAi 0.6 cm2/m2, and stroke volume index 35 mL/m2 are required for D3 (low gradient, normal EF 50%, or paradoxical lowflow severe AS); mean pressure gradient is 40 mm Hg; and jet velocity is 4 m/s.

Other/Diagnostic Procedures
Exercise stress testing is useful to identify modest symptoms or changes, high blood pressure (an increase of at least 20 mm Hg), and ECG alterations (ST depressions) in asymptomatic patients with severe AS. Exercise testing causes symptoms in one-third of patients; STOP testing at this point.
Exercise stress testing should not be done on symptomatic patients since it may produce hypotension or ventricular tachycardia.
Dobutamine stress echocardiography is an acceptable evaluation method for CHF patients who have LV dysfunction and low-flow/lowgradient AS.
Prior to an aortic valve replacement (AVR), individuals with suspected CAD should undergo a cardiac catheterization. decides whether a coronary artery bypass graft (CABG) is necessary. If AS is definitively diagnosed, only coronary angiography should be done.
– Useful when noninvasive testing is inconclusive or when the severity of the symptoms and the echo results conflict.
– calculates effective valve area by measuring transvalvular flow and transvalvular pressure gradient.
– For the examination of patients with low-flow/low-gradient AS and LV dysfunction, hemodynamic measures with dobutamine infusion may be helpful.

LVH, myocardial interstitial fibrosis, nodular calcification on the valve cusps (at first at bases), cusp rigidity, cusp thickening, and fibrosis; 50% incidence of concurrent CAD;

TREATMENT /MEDICATION
There is no proven medical treatment for severe or symptomatic AS.

Prevention: There is no currently suggested medical treatment.
When used in the early stages of an illness, statins are believed to reduce disease development. Large, randomized controlled trials have not, however, backed up this claim.

Patients with rheumatic AS should get antibiotic prophylaxis against recurrent RF (penicillin G 1,200,000 U IM every four weeks; duration varies with age and history of carditis).
The use of antibiotic prophylaxis to prevent infective endocarditis is no longer recommended.
Comorbid conditions Angiotensin-converting enzyme (ACE) inhibitors for hypertension; start with a low dose and increase gradually. Vasodilators should be avoided since they can result in hypotension.
SURGICAL AND OTHER PROCEDURE
For the majority of symptomatic individuals with substantial AS on echocardiography, AVR is advised.

 Causes of AVR surgery:
- History or exercise testing showing symptoms of severe high-gradient AS (2)[B] when the risk of surgery is modest or moderate
- LVEF 50%, severe AS, and no symptoms - Severe AS (stage C or D) while having further heart surgery

Patients who are: - Asymptomatic with severe AS (C1) with jet velocity 5 m/s and minimal surgical risk, have impaired exercise tolerance, or have an activity-induced drop in blood pressure should consider AVR surgery. 
Stage D2 symptomatology, low-dose dobutamine stress, jet velocity 4.0 m/s or mean pressure gradient 40 mm Hg with 1.0 cm2 (2) [B]
- Stage D3 symptomatic with LVEF >50% when valve blockage is supported by clinical and hemodynamic data (2)[C]
- Stage B patients receiving further cardiac surgery, or stage C1 patients who are asymptomatic with quick disease development and little surgical risk (2)[C]
ALERT
There is no advantage from AVR if the aortic valve area is greater than 1.5 cm2 and the gradient is less than 15 mm Hg.
For some individuals, transcatheter AVR (TAVR) offers a less invasive approach (1).
– TAVR has proven to be better to medicinal therapy for patients who are inoperable and at high surgical risk.
– TAVR has shown noninferiority to surgical AVR in patients who are at high surgical risk.
– Although this indication has not yet been approved in the United States, TAVR may become a viable option to surgery for patients who are intermediately at risk.
In high-risk patients with failed surgically implanted bioprosthetic valves, valve-in-valve TAVR may be an option.
Percutaneous balloon valvuloplasty is not advised as a substitute for valve replacement, however it may play a role in palliation or as a step before valve replacement in patients who are hemodynamically unstable or at high risk.

CONTINUING CARE AFTERCARE RECOMMENDATIONS
Encourage patients to report any AS-related symptoms right away.
Patients with no symptoms: annual history and examination
Serial ECHO is administered every year for severe AS, every one to two years for moderate AS, and every three to five years for mild AS. 

EDUCATION OF PATIENTS
Limitations on physical activity

No restrictions for asymptomatic mild AS; asymptomatic moderate to severe AS AS: Steer clear of intense exertion. Before beginning an exercise regimen, take a stress test.

PROGNOSIS: Although survival in asymptomatic patients is comparable to that in control patients of the same age and sex, it rapidly declines once symptoms manifest.
AVR surgery results in an annual mortality rate of 25% in symptomatic patients; the average survival time is 2 to 3 years.
 In symptomatic AS, the median survival was 2 years for heart failure, 3 years for syncope, and 5 years for angina.
AVR surgery has a 4% death rate, while AVR + CABG has a 6.8% mortality rate.
 Unfavorable postoperative prognostic variables: age, New York Heart Association (NYHA) class III/IV heart failure, cerebrovascular disease, and renal impairment as well as CAD.