Heart sounds

Heart sounds

In cardiac auscultation, an examiner uses a stethoscope to listen for these sounds, which provide important information about the condition of the heart.

In healthy adults there are two normal heart sounds often described as a lub and a dub, that occur in sequence with each heart beat. These are the first heart sound (S₁) and second heart sound (S₂), produced by the closing of the AV valves and semilunar valves respectively. In addition to these normal sounds, a variety of other sounds may be present including heart murmurs, adventitious sounds, and gallop rhythms S₃ and S_4.

S₁

Caused by closure of AV valves at the beginning of ventricular systole. The first heart tone, or S₁, forms the "lubb" of "lubb-dub" or "lubb-dup" and is composed of components M₁ and T₁. Normally M₁ precedes T₁ slightly.

S₂

The second heart tone, or S₂, forms the "dub" of "lubb-dub" and is composed of components A₂ and P₂. Normally A₂ precedes P₂ especially during inspiration when a split of S₂ can be heard. It is caused by the sudden block of reversing blood flow due to closure of the aortic valve and pulmonary valve at the end of ventricular systole, i.e beginning of ventricular diastole.

S₃

It occurs at the beginning of diastole after S2 and is lower in pitch than S1 or S2 as it is not of valvular origin. Benign in some youth and trained athletes. S3 is thought to be caused by the oscillation of blood back and forth between the walls of the ventricles initiated by inrushing blood from the atria. An S3 heart sound is best heard with the bell-side of the stethoscope (used for lower frequency sounds). A left-sided S3 is best heard in the left lateral decubitus position and at the apex of the heart, which is normally located in the 5th left intercostal space at the midclavicular line.^[2] A right-sided S3 is best heard at the lower-left sternal border.

S₄

The rare fourth heart sound is sometimes audible in healthy children and again in trained athletes, but when audible in an adult is called a presystolic gallop or atrial gallop. This gallop is produced by the sound of blood being forced into a stiff/hypertrophic ventricle. It is a sign of a pathologic state, usually a failing left ventricle, but can also be heard in other conditions such as restrictive cardiomyopathy. The sound occurs just after atrial contraction ("atrial kick") at the end of diastole and immediately before S1. It is best heard at the cardiac apex with the patient in the left lateral decubitus position and holding his breath. The combined presence of S3 and S4 is a quadruple gallop. At rapid heart rates, S3 and S4 may merge to produce a summation gallop (sometimes referred to as S7).

Murmurs are extra heart sounds that are produced as a result of turbulent blood flow which is sufficient to produce audible noise. Murmurs may be physiological (benign) or pathological (abnormal). Catergorised into 6 depending on intensity of murmur(Levine scale). Common descriptive terms include rumbling, blowing, machinery, scratchy, harsh, or musical.

§ Regurgitation through the mitral valve is by far the most commonly heard murmur, sometimes fairly loud to a practiced ear, even though the volume of regurgitant blood flow may be quite small. Yet, though obvious using echocardiography visualization, probably about 20% of cases of mitral regurgitation do not produce an audible murmur.

§ Stenosis of the aortic valve is typically the next most common heart murmur, a systolic ejection murmur. This is more common in older adults or in those individuals having a two, not a three leaflet aortic valve.

Note: We don’t hear the sounds of the valves directly over the valves because the sound waves are conducted to defferent regions

Investigation and diferential diagnosis of aortic stenosis

Investigations
The health care provider will be able to feel a vibration or movement when placing a hand over the person's heart. A heart murmur, click, or other abnormal sound is almost always heard through a stethoscope. There may be a faint pulse or changes in the quality of the pulse in the neck

Imaging tests
Chest radiography
o Chest radiographs may show cardiac enlargement. Minimal enlargement and more subtle signs of concentric hypertrophy without dilatation are present, including mildly enlarged heart size, rounding at the cardiac apex, and slight backward displacement of the heart as seen in lateral view.
o In later, more severe stages of aortic stenosis, radiographic signs of left atrial enlargement, pulmonary artery enlargement, right-sided enlargement, calcification of the aortic valve, and pulmonary congestion may be evident.

Echocardiography
o TTE-Two-dimensional transthoracic echocardiography can confirm the clinical diagnosis of aortic stenosis and provide specific data on left ventricular function. It can show the structure and function of the other valves as well.

Possible findings
 An aortic valve with no cusp motion is indicative of severe aortic stenosis.
 A decrease in the maximal aortic cusp separation is also indicative of severe aortic stenosis.
 The presence of otherwise unexplained left ventricular hypertrophy implies significant aortic stenosis.

o Using echo-Doppler techniques, the systolic pressure gradient across the aortic valve can be assessed. Doppler techniques also can help visualize any mitral or aortic regurgitation that might be present.

Other tests

Electrocardiography
o Generally, ECG is not a reliable test because of the wide variations seen in aortic stenosis and other cardiac conditions.
o An ECG of a patient with significant aortic stenosis most likely shows evidence of left ventricular hypertrophy. T-wave inversion and ST-segment depressions are common.

Cardiac catheterisation
Catheterization of the left side is performed to obtain information about the heart chambers on the left side (left atrium and left ventricle), the mitral valve (located between the left atrium and left ventricle), and the aortic valve (located between the left ventricle and the aorta). The left side is catheterized more often than the right.
Measuring the left ventricular end-diastolic and systolic volume and calculating the ejection fraction (EF) can quantitate the status of LV systolic pump function.

Stress testing
Stress testing gives your doctor information about how your heart works during physical stress. Some heart problems are easier to diagnose when your heart is working hard and beating fast.
During a stress test, you exercise (walk or run on a treadmill or pedal a bicycle) to make your heart work hard and beat fast. Tests are done on your heart while you exercise.
You may have arthritis or another medical problem that prevents you from exercising during a stress test. If so, your doctor may give you medicine to make your heart work hard, as it would during exercise. This is called a pharmacological stress test.

A stress test can detect the following problems, which may suggest that your heart isn't getting enough blood during exercise.
• Abnormal changes in your heart rate or blood pressure
• Symptoms such as shortness of breath or chest pain, which are particularly important if they occur at low levels of exercise
• Abnormal changes in your heart's rhythm or electrical activity

Exercise stress testing is usually not needed in patients with severe aortic stenosis to rule out coronary artery disease. However, closely monitored exercise stress testing may be of value to assess exercise capacity in asymptomatic patients. Abnormal results may prove greater disability than the patient would admit. In addition to watching for symptoms on the treadmill, one should also look for hemodynamic abnormalities, such as blood pressure decreases or failure to increase blood pressure normally, which can occur in the absence of symptoms. The test here is not used to screen for coronary disease.




Differential diagnosis

Myocardial Infarction
• Convex ST-segment elevation with upright or inverted T waves is generally indicative of myocardial infarction in the appropriate clinical setting.
• Troponin levels are now considered the criterion standard in defining and diagnosing myocardial infarction, according to the American College of Cardiology (ACC)/American Heart Association (AHA) consensus statement on myocardial infarction. Elevated amount of troponin in the blood is very likely due to a MI.

Hypovolemic Shock
• Hypovolemic shock refers to a medical or surgical condition in which rapid fluid loss results in multiple organ failure due to inadequate circulating volume and subsequent inadequate perfusion. Most often, hypovolemic shock is secondary to rapid blood loss
• Could be mistaken with aortic stenosis because of low BP and increased pulse rate. But easily ruled out by history and blood test.

Mitral Regurgitation
• The echocardiogram is commonly used to confirm the diagnosis of mitral regurgitation. Color doppler flow on the transthoracic echocardiogram (TTE) will reveal a jet of blood flowing from the left ventricle into the left atrium during ventricular systole.

Mitral Stenosis
• Use of chest x-ray, echocardiography, doppler’s echocardiography.

Mitral Valve Prolapse
• Echocardiography is the most useful method of diagnosing a prolapsed mitral valve. Two- and three-dimensional echocardiography are particularly valuable as they allow visualization of the mitral leaflets relative to the mitral annulus. This allows measurement of the leaflet thickness and their displacement relative to the annulus. Thickening of the mitral leaflets >5 mm and leaflet displacement >2 mm indicates classic mitral valve prolapse.

Classical Signs & Symptoms of Aortic Stenosis

***Quick review!!!
Symptoms: What the patient present with upon consultation.
Signs: What the doctor get from patient upon examination.

Symptoms
Symptoms and heart problems in aortic stenosis are related to the degree of narrowing of the aortic valve area. Patients with mild aortic valve narrowing may experience no symptoms. When the narrowing becomes significant (usually greater that 50% reduction in valve area), the pressure in the left ventricle increases and a pressure difference can be measured between the left ventricle and the aorta.

In 4% of the patients with aortic stenosis, the first symptom is sudden death, usually during strenuous exertion.

The major symptoms of aortic stenosis are:
• chest pain (angina)-usually 1st symptom. The pain is described as pressure below the breast bone brought on by exertion and relieved by rest. The thickened heart muscle must pump against high pressure to push blood through the narrowed aortic valve. This increases heart muscle oxygen demand in excess of the supply delivered in the blood, causing chest pain.
• fainting (syncope)- usually associated with exertion or excitement. These conditions cause relaxation of the body's blood vessels (vasodilation), lowering blood pressure. In aortic stenosis, the heart is unable to increase output to compensate for the drop in blood pressure. Therefore, blood flow to the brain is decreased, causing fainting. Fainting can also occur when cardiac output is decreased by an irregular heart beat (arrhythmia). Without effective treatment, the average life expectancy is less than three years after the onset of chest pain or syncope symptoms.
• shortness of breath (dyspnoe)- reflects the heart muscle's failure to compensate for the extreme pressure load of aortic stenosis. Shortness of breath is caused by increased pressure in the blood vessels of the lung due to the increased pressure required to fill the left ventricle. Initially, shortness of breath occurs only during activity. As the disease progresses, shortness of breath occurs at rest. Patients can find it difficult to lie flat without becoming short of breath (orthopnea). Without treatment, the average life expectancy after the onset of heart failure due to aortic stenosis is between six to 24 months.


Classical Clinical Signs
• Small and delayed pulse-absence of this finding, particularly in an elderly patient with noncompliant vasculature, does not exclude severe aortic stenosis.

• Systolic murmur-may be most easily audible in the ‘mitral area’. This may cause a mistaken diagnosis of ischaemic mitral regurgitation in a patient with severe aortic stenosis and angina. The absence of a murmur over the right clavicle can help to exclude aortic stenosis.

• Soft or absent second heart sound

• Hypotension

Prognosis - Aortic Stenosis

-Without surgery, a person with aortic stenosis who has angina or signs of heart failure may do poorly.
-After surgery there is a risk for irregular heart rhythms, which can cause sudden death, and blood clots, which can cause a stroke.
-There is also a risk that the new valve will stop working and need to be replaced

Aortic valves replacement surgery :
-The overall mortality risk : 5%
-Advanced age should not be a reason for not recommending aortic valve replacement for aortic stenosis.
-Otherwise healthy patients in their 80s with strong heart muscles often benefit dramatically from aortic valve replacement for critical aortic stenosis.

Balloon Valuloplasty:-Those who respond to valvuloplasty with improvement in ventricular function can be expected to benefit even more from aortic valve replacement.
-Aortic valvuloplasty in these high risk elderly patients has a similar mortality (5%) and serious complication rate (5%) as aortic valve replacement in surgical candidates.
-In critically ill patients, the mortality rate associated with the procedure is 3-7%.
-Another 6% develop serious complications including perforation, myocardial infarction, and severe aortic regurgitation.

Treatment - Aortic Stenosis

Goals of treatment :
- to allow the heart to get more blood into general circulation, improving overall blood supply to the body and the heart.
- to help reduce the person's symptoms.
- to treat complications

Patients with mild aortic stenosis (valve area > 1.2 square centimeters) :
- do not require treatment or restriction of activity

Patients with moderate aortic stenosis (valve area 1.5 to 1.0 square centimeters)
-avoid strenuous activities such as weight lifting or sprinting.

Symptomatic patients (chest pain, syncope, or shortness of breath)
- Aortic Valve replacement surgery
- Balloon valvuloplasty

Aortic Valve replacement : - 2 types of valves :
~ Bioprostheses - processed from pigs (porcine) or cows (bovine)
>less durable than mechanical prostheses
>have the advantage of not needing life-long blood thinning (anticoagulation)
medication to prevent blood clots from forming on the valve surfaces.
>average life expectancy : 10 to 15 years
>rapidly calcify, degenerate and narrow in young patients
>primarily used in patients over 75 years old or in patients who cannot take
blood thinners.
~ Mechanical prostheses
>extremely durable
>life expectancy : from 20 to 40 years.
>require life-long anticoagulation with blood thinners such as warfarin
(Coumadin) to prevent clot formation on the valve surfaces.
>Otherwise, blood clots dislodged from these valves can travel to the brain and
cause embolic stroke or embolic problems in other parts of the body

The surgeon will begin by exposing the heart. An incision is made to divide the breastbone. After the heart is exposed, blood must be rerouted to a heart-lung machine. This allows the blood to be pumped and oxygenated while the surgeon operates on the heart.

Your surgeon can now replace the damaged valve. An incision is made in the aorta to access the aortic valve. The diseased valve leaflets are then removed. After the appropriate valve is selected, sutures are used to secure the prosthetic valve. The aorta is then closed.

Blood is allowed to flow into the coronary arteries. If needed, an electric shock is used to start the heart. Before the chest is closed, pacing wires may be left to control irregular rhythm.

Balloon Valvuloplasty : -The aortic valve area can be opened or enlarged with a balloon catheter (balloon valvuloplasty)
-Patients with critical aortic stenosis can therefore experience temporary improvement with this procedure.
-Most of these valves narrow over a six to 18 month period.
-useful as a short-term measure to temporarily relieve symptoms in patients who are not candidates for aortic valve replacement.
-useful as a bridge to aortic valve replacement in the elderly patient with poorly functioning ventricular muscle.

In balloon valvuloplasty, a thin tube (catheter) with a small deflated balloon at its tip (balloon-tipped catheter) is inserted through the skin in the groin area into a blood vessel, and then is threaded up to the opening of the narrowed heart valve. The balloon is inflated to stretch the valve open and relieve the valve obstruction.

The procedure, which takes up to four hours, is performed in a cardiac catheterization laboratory that has a special x-ray machine and an x-ray monitor that looks like a regular TV screen. The patient will be placed on an x-ray table and covered with a sterile sheet. An area on the inside of the upper leg will be washed and treated with an antibacterial solution to prepare for the insertion of a catheter. The patient is given local anesthesia to numb the insertion site and will usually remain awake, able to watch the procedure on the monitor. After the insertion site is prepared and anesthetized, the cardiologist inserts a catheter into the appropriate blood vessel, then passes the smaller balloon-tipped catheter through the first catheter. Guided by the xray monitor that allows visualization of the catheter in the blood vessel, the physician slowly threads the catheter up into the coronary artery to the heart. The deflated balloon is carefully positioned in the opening of the valve that is being treated, and then is inflated repeatedly, which applies pressure to dilate the valve. The inflated balloon widens the valve opening by splitting the valve leaflets apart. Once the valve is widened, the balloon-tipped catheter is removed. The other catheter remains in place for six to 12hours because, in some cases, the procedure must be repeated. A double-balloon valvuloplasty procedure is often performed on certain high-risk patients because it is considered more effective in restoring blood flow.

Antibiotics :
Since valve infection (endocarditis) is a serious complication of aortic stenosis, these patients are usually given antibiotics prior to any procedure in which bacteria may be introduced into the bloodstream.

This includes routine dental work, minor surgery, and procedures that may traumatize body tissues such as colonoscopy and gynecologic or urologic examinations.

Examples :-oral amoxicillin (Amoxil) and erythromycin (E-Mycin, Eryc, PCE
-intramuscular or intravenous ampicillin (Unasyn), gentamicin (Garamycin), and vancomycin (Lyphocin, Vancocin

Mural Thrombosis

There is really nothing that I can find about this condition on the Net or in Kumar & Clark's but here's the definition for the moment :

Formation of a thrombus in contact with the endocardial lining of a cardiac chamber or, if not occlusive, with a wall of a large blood vessel.

Thrombus and Clot

Thrombosis represents a pathologic state in which there is formation of intra-vascular solid mass (thrombus) from the elements of circulating blood. The vessel may be uninjured or with minor injury.

Thrombosis:

Three primary factors influence thrombus formation (Virchow’s triad):

1. Endothelial injury.

2. Slowing of blood flow.

3. Hyper coagulability of blood.

1. Endothelial injury commonest cause, mainly in the heart and arterial circulation (e.g. Myocardial infarction, endocarditis, ulcerated atherosclerosis). Injury may occur from diverse causes e.g. hemodynamic stress (hypertension or turbulent flow in aneurysms), radiation, products absorbed from cigarette smoke, extensive burn etc.

2. Slowing of circulation (alteration in normal blood flow):

Normal blood flow is laminar (i.e., the cellular elements flow centrally inside the vessel, separated from endothelium by a clear zone of plasma).

Stasis and turbulence disrupt laminar flow and bring platelets into contact with the endothelium.

They prevent dilution of activated clotting factors by fresh flowing blood, retard the inflow of clotting factor inhibitors and permit the build-up of thrombi.

Stasis is important in causing thrombosis in veins, cardiac chambers and arterial aneurysms.

Hyperviscosity syndrome - Example: In polycythemia or deformed RBC as in sickle cell anemia causes stasis in small blood vessels predisposing to thrombosis.

3. Hypercoagulability of blood may be due to heritable gene mutation or acquired.

Example: Severe burn, shock, oral contraceptive, increased hepatic synthesis of coagulation factors and reduced synthesis of anti-thrombin III.

Mechanism:

Normally, in a blood vessel, cellular elements flow centrally, forming axial stream separated from endothelium by a clear, cell-free, plasmatic zone. Due to slowing of the circulation, platelets come in contact with endothelium and are activated to liberate tissue factors. Tissue factors recruit more platelets, which are deposited in the form of ridges at right angles to the blood flow forming corrugations, known as line of Zahn. Coming in contact with sub-endothelial collagen, platelets are activated to release ADP, Thromboxanes etc. ADP aggregate more platelets.

Thromboplastin, liberated from platelets and injured endothelium initiate precipitation of fibrin on the surface of platelets. Fibrin network may entangle RBC and leucocytes.

A thrombus is thus formed, on the basis of platelets and fibrin, with varying number of RBC and leucocytes.

Thrombi may form anywhere in the cardiovascular system.

Aortic and cardiac thrombi are typically nonocclusive (mural) as a result of rapid and high-volume flow.

Smaller arterial thrombi may be occlusive.

All these thrombi usually begin at sites of endothelial injury (e.g. atherosclerotic plaque) or turbulence (vessel bifurcation).

Venous thrombi characteristically occur in sites of stasis and are occlusive.

At sites of origin, thrombi are generally firmly attached. Arterial thrombi tend to extend retrograde from the attached point, where as venous thrombi extend on the direction of blood flow. The propagating tail may not be well attached and may fragment to create an embolus.

Sites of thrombus formation:

Cardiac and arterial thrombi are formed slowly in rapid circulation. They are pale-gray and tend to have gross and microscopic lamination (lines of Zahn) produced by pale layers of plates and fibrin alternating with darker red cell-rich layers. These are mostly seen in the left ventricle overlying an infarct, ruptured atherosclerotic plaques, and aneurysmal sacs.

Venous thrombosis (phlebothrombosis) often created a long red-blue cast of the vein lumen as it occurs in a relatively slow circulation. The thrombus contains more enmeshed erythrocytes among sparse fibrin strands (red or stasis thrombus).

Fibrin and attachment to the vessel wall distinguish stasis thrombus from postmortem clot. Phlebothrombosis is most commonly (more than 90 %) seen in the veins of the lower extremities.

Thrombi may also form on heart valves. In infective endocarditis, bacteria or fungi form large infected thrombi (vegetations), causing underlying valve damage and systemic infection. Sterile vegetations (nonbacterial thrombotic endocarditis) can also develop on noninfected valves in patients with hypercoagulable states, particularly in those with disseminated cancer. Noninfective, verrucous(Libman-Sacks) endocarditis is seen in patients of SLE due to circulating immune complex.

Heart:

i) Ball thrombus is seen in left atrium in mitral stenosis. It is large and spherical.

ii) Mural thrombus is seen over the wall of heart in cardiac infarct, cardiomyopathy

iii) Agonal thrombus is seen in right ventricle in case of death due to pneumonia.

iv) Vegetations over the cardiac valves are seen in endocarditis.

Artery:

i) On the atheromatous patch in coronary, cerebral, spleen, and renal arteries.

ii) Laminated thrombus is seen in aneurysmal sac.

iii) Marasmic thrombus is seen in marasmic children, in mesenteric artery (stasis)

Vein:

Veins are the commonest sites of thrombus formation due to slow circulation.

Other causes of venous thrombosis are:

i) Trauma, burn, due to reduced physical activity, injury to vessels and release of pro-coagulants from tissue.

ii) Puerperal and postpartum thrombosis occurs mainly due to amniotic fluid infusion into blood and hypercoagulability in late pregnancy and in postpartum period. .

iii) Disseminated cancer, due to release of tumour-associated -procoagulants.

iv) Advanced age, bed rest, immobilization, reduced physical activity diminishes milking action of muscle.

v) Thrombophlebitis is the inflammation of the venous wall due to septic thrombus.

Example: a) Pelvic veins in puerperal sepsis ; b) Portal vein in acute appendicitis ; c) Cavernous sinus in facial infection

Fate of a thrombus:

Septic thrombus causes abscess formation.

Aseptic thrombus may show:

i) Propagation causing complete vessel obstruction.

ii) Dissolution by fibrinolytic action.

iii) Detachment- with embolism.

iv) Organization and recanalization, re-establishing vascular flow by in-growth of endothelial cells, smooth muscle cells and fibroblasts to create through-and through capillary channels or by incorporating the thrombus as a sub-endothelial swelling of the vessel wall.

Effect of thrombosis:

Septic: Forms abscess and may cause pyaemia.

Aseptic: Effect will depend upon the vessel involved and efficiency of the collateral circulation of the area.

1. Arterial thrombus - in a small vessel is occlusive and usually causes infarction. This is particularly seen when it involves organs supplied with end-arteries (Example: cerebral, coronary, splenic, mesenteric and renal arteries).

2. Venous thrombosis - rarely causes infarction, as collateral channels soon enlarge to maintain the venous drainage.

Superficial venous thrombosis, as in varicose saphenous veins, causes local edema and impaired venous drainage, predisposing to skin infection and varicose ulcer.

Deep thrombi in larger leg veins above the knee (Example: popliteal, femoral and iliac veins), have good collateral circulation but commonly embolize (about 50 % cases).

Occlusive venous thrombi with poor collateral channels cause increased venous and capillary pressure forming edema (Example: ascites in portal vein thrombosis).

Beneficial effect of thrombosis:

Thrombosis causes hemostasis and sealing of the vessel wall after erosion by malignant tumours and attempts to prevent hematogenous spread.

Blood clot: Coagulation of dead blood (Example: in a test tube, in a blood vessel after death or after ligature).

Types of clot:

1. Current jelly clot (soft and red) forms rapidly in great vessels or heart. All the elements of blood are involved.

2. Chicken fat clot (lower part dark, upper part yellow) forms slowly, RBC settles at the bottom and pale upper part consists of leucocytes and fibrin.

Aortic Stenosis definition, incidence and prevalence.

Aortic Stenosis (AS)

Overview
-Aortic (aortic valve) Stenosis (abnormal narrowing of a passage) can be defined by restricted systolic opening of the valve leaflets with a mean transvalvular pressure gradient of at least 10 mm Hg
-The aortic valve does not open fully.
-Valve leaflets become coated with deposit. The deposits change the shape of the leaflets and reduce blood flow through the valve. The left ventricle has to work harder to make up for the reduced blood flow.
-May have no symptoms at all until late in the course of the disease.
-Diagnosis will be made based on the “heart murmur” and additional tests.

Incidence and Prevalence
-5 out of 10,000 people in US
-Common congenital cardiac defect (4 in 1000 live birth)
- AS caused by a congenital bicuspid aortic valve affects more men than women
-Later life calcific disease of a trileaflet valve affects both genders equally.
-80% of adults with symptomatic AS are male
-ppl >75 y/o, 3% have critical AS
-ppl <70y/o, 2% have AS

Mortality and Morbidity
-Sudden cardiac death: 3~5%
-Adult with AS: 9% mortality per year
-Incidence of sudden death after symptoms developed” 15~20% (survival duration <5 year)

Reference:
http://www.texasheartinstitute.org/HIC/Topics/Cond/vaortic.cfm
http://www.cardiologychannel.com/aorticstenosis/index.shtml
http://emedicine.medscape.com/article/757200-overview
http://www.clevelandclinicmeded.com/medicalpubs/diseasemanagement/cardiology/aortic-valve-disease/

Atielogy and Pathophysio of Aortic Stenosis

Atielogy

Congenital:
• Congenital Bicuspid Valve: Usually asymptomatic in the event of the early life. Usually diagnosed during routine physical check-up. 4 times likely to get the more compared to normal individuals in later life. Predominantly men.
• Congenital Aortic Stenosis: Usually develops congestive heart failure in the first week of life due to the incompatibly of the small left ventricle to sustain life.

Aquired
• Aortic sclerosis: Degenerative aortic valve disease with thickening of the aortic valves with fibrosis and calcification. Over the years it progresses to aortic stenosis in 15% of the patients. Resemblance to atherosclerosis with deposition of lipoproteins and active inflammation. Patients with risk factors for atherosclerosis have a higher chance to develop aortic stenosis.
• Rheumatic Fever: Patients have a fibrous contracture with shortening of the cusps due to recurrent inflammation from rheumatic carditis. Adjacent cusps tend to fuse at commissures. This causes a form of bicuspid or unicuspid valve. Calcification can occur but primary cause of stenosis is the adhesions that form the cusps. Incidence decreases with the decrease in rheumatic fever. Developing contries.
• Other less common causes of aortic stenosis include homozygous hypercholesterolemia, and radiation heart disease.

Pathophysiology
When the aortic valve becomes stenotic, resistance to systolic ejection increases as the lumen between the ventricular and aortic compartments becomes smaller. This creates a systolic gradient between the left ventricle and the aorta. This leads to pressure overload in the left ventricle to meet the demands of the cardiac output and causes left ventricle hypertrophy. At this stage, the ventricle chamber is not dilated, although diastolic compliance may be affected.
Eventually, the chamber will dilate, coupled with increase compliance, increase in end systolic pressure and rise in atrial systolic pressure will result in an overload in pressure. This eventually leads to myocardial decompensation. The contractility of the myocardium diminishes causing a drop in cardiac output. The increase in end systolic pressure causes an increase in left atrium pressure in which involving the pulmonary circuit, also decrease in ejection fraction. In the end, it sums up to Congestive Heat Failure (CHF).

An overview of Aortic Stenosis

taken from d same website again X) emedicine.medscape.com

Aortic stenosis (AS)

Aortic stenosis is a narrowing or obstruction of the aortic valve.

Pathophysiology

The pathophysiologic mechanisms responsible for symptoms (ie, angina, syncope, congestive heart failure) in patients with aortic stenosis include an increase in left ventricular (LV) afterload, progressive LV hypertrophy, and a decrease in systemic and coronary flow as consequences of valve obstruction.

In adults with aortic stenosis, LV outflow obstruction increases gradually over a long period of time, during which time the patient is asymptomatic. This progressive outflow obstruction results in increased LV mass by parallel replication of sarcomeres producing concentric hypertrophy, which is a compensatory mechanism to normalize LV wall stress. Inadequate development of hypertrophy, depression of myocardial contractility, or a combination of these factors may lead to impairment of LV performance (so-called afterload mismatch) and congestive heart failure (CHF) symptoms. Indeed, wall thickness appears to be a critical determinant of ventricular performance in patients with aortic stenosis. If afterload mismatch occurs, the LV ejection fraction, cardiac output, stroke volume, and transvalvular pressure gradient decline.

In most patients with aortic stenosis, LV systolic function is preserved and cardiac output is maintained for many years despite an elevated LV systolic pressure. Despite the fact that cardiac output at rest is normal, it often fails to increase appropriately during exercise, which may result in exercise-induced syncope or near syncope.

In the patient with aortic stenosis, diastolic dysfunction may occur as a consequence of impaired LV relaxation and/or decreased LV compliance, as a result of increased afterload, LV hypertrophy, or myocardial ischemia. LV hypertrophy often regresses following relief of valvular obstruction. However, in some individuals, extensive myocardial fibrosis develops, which may not disappear despite regression of hypertrophy.

In patients with severe aortic stenosis, atrial contraction plays a particularly important role in diastolic filling of the LV. Thus, development of atrial fibrillation in aortic stenosis is often catastrophic to the maintenance of normal forward stroke volume.

Increased LV mass, increased LV systolic pressure, and prolongation of the systolic ejection phase all elevate the myocardial oxygen requirement, especially in the subendocardial region. Coronary blood flow at rest is increased but normal when corrected for LV mass; however, coronary flow reserve is often reduced. Myocardial perfusion is also compromised by the relative decline in myocardial capillary density and by a reduced diastolic transmyocardial (coronary) perfusion gradient due to elevated LV diastolic pressure. Therefore, the subendocardium is susceptible to underperfusion, which results in myocardial ischemia.

Clinical

History

In aortic stenosis, a long latent period exists during which time the LV outflow obstruction and the pressure load on the myocardium gradually increase while patients remain asymptomatic.

• The classic symptom triad of aortic stenosis includes angina pectoris, syncope, and heart failure, which most commonly manifest after the sixth decade of life.
• Some patients remain asymptomatic, but others develop exertional chest pain, effort dizziness or lightheadedness, easy fatigueability, and progressive inability to exercise.
• Exertional dyspnea is the most common initial complaint, even with normal LV systolic function, and it often relates to abnormal LV diastolic function.
• Angina pectoris occurs in approximately two thirds of patients with critical aortic stenosis, of which 50% have significant coronary artery disease. Because angina commonly is precipitated by exertion and relieved by rest, it simulates symptoms of coronary artery disease. Angina results from a concomitant increased oxygen requirement by the hypertrophic myocardium and diminished oxygen delivery secondary to diminished coronary flow reserve, decreased diastolic perfusion pressure and relative subendocardial myocardial ischemia. Of course, angina also can result from coexistent coronary artery disease.
• The cause of syncope is multifactorial. It often occurs upon exertion when systemic vasodilatation causes the arterial systolic blood pressure to decline in the presence of a fixed forward stroke volume. It also may be caused by atrial or ventricular tachyarrhythmias.
• Syncope at rest may be due to transient ventricular tachycardia, atrial fibrillation, or atrioventricular block, with the latter due to extension of the calcification of the valve into the conduction system. Another cause of syncope is abnormal vasodepressor reflexes caused by increased LV intracavitary pressure (vasodepressor syncope).
• Congestive heart failure symptoms (ie, paroxysmal nocturnal dyspnea, orthopnea, dyspnea on exertion, and shortness of breath) may be due to systolic dysfunction from afterload mismatch, ischemia, or a separate cardiomyopathic process. Alternatively, diastolic dysfunction from LV hypertrophy or ischemia may also result in congestive heart failure symptoms.
• In patients in whom the aortic valve obstruction remains unrelieved, the onset of symptoms predicts a poor outcome with medical therapy; the approximate time interval from the onset of symptoms to death is 2 years for congestive heart failure, 3 years for syncope, and 5 years for angina.
• Gastrointestinal bleeding due to angiodysplasia or other vascular malformations is present at a higher than expected frequency in patients with calcific aortic stenosis; it usually resolves following aortic valve surgery.
• The risk of infective endocarditis is higher in younger patients with mild valvular deformity than in older patients with degenerated calcified aortic valves, but it can occur in either. It can occur at any age with hospital-acquired Staphylococcus aureus bacteremia, which frequently results in aortic valve replacement.
• Calcific aortic stenosis rarely may cause emboli of calcium to various organs, including the heart, kidney, and brain.
• Sudden cardiac death is rare and usually occurs in symptomatic patients.

Physical

In severe aortic stenosis, the carotid arterial pulse is typically diminished and rises slowly (pulsus parvus et tardus); however, in elderly individuals with rigid carotid vessels, this may not be present. A lag time may be present between the apical impulse and the carotid impulse. Systolic hypertension can coexist with aortic stenosis, but a systolic blood pressure higher than 200 mm Hg is rare in patients with critical aortic stenosis.

• Pulsus alternans can occur with the onset of LV dysfunction. The jugular venous pulse may show prominenta waves reflecting reduced RV compliance consequent to hypertrophy of the interventricular septum.
• At the apex, a precordial a wave often is visible and palpable. A hyperdynamic LV is unusual and suggests concomitant aortic regurgitation or mitral regurgitation. A systolic "thrill" may be present at the second right intercostal space or at the suprasternal notch. The thrill is best felt while the patient is leaning forward. On occasion, it can be transmitted to the carotids.
• S₁ is usually normal or soft.
• The aortic component of the second heart sound, A₂, is usually diminished or absent because the aortic valve is calcified and immobile and/or aortic ejection is prolonged and it is obscured by the prolonged systolic ejection murmur. The presence of a normal or A₂ speaks against the presence of severe aortic stenosis. Paradoxical splitting of the S₂ also occurs because of late closure of A₂. P₂ may also be accentuated when LV failure leads to secondary pulmonary hypertension.
• The presence of an ejection sound (eg, ejection click) is dependent on the mobility of the valve cusps and disappears when they become immobile and severely calcified. Thus, an ejection click is common in children and young adults with congenital aortic stenosis but rare in elderly individuals with acquired calcific aortic stenosis. This sound occurs approximately 40-60 milliseconds after the onset of S₁ and is frequently heard best along the mid to lower left sternal border; it is often well transmitted to the apex and may be confused with a split S₁.
• A prominent S₄ is usually present due to forceful atrial contraction into a hypertrophied left ventricle. The presence of an S₄ in a young patient with aortic stenosis indicates significant aortic stenosis, but with aortic stenosis in an elderly person, this is not necessarily true.
• The classic crescendo-decrescendo systolic murmur of aortic stenosis is best heard at the second intercostal space in the right upper sternal border; it is harsh at the base and radiates to one or both carotid arteries. However, it may be more prominent at the apex in elderly persons with calcific aortic stenosis due to radiation of the high-frequency components of the murmur to the apex (Gallavardin phenomenon) leading to its misinterpretation as a murmur of mitral regurgitation. Accentuation of the aortic stenosis murmur following a long R-R interval (as in atrial fibrillation or following a premature beat) distinguishes it from the mitral regurgitation murmur, which usually does not change.
• The intensity of the systolic murmur does not correspond to the severity of aortic stenosis, rather, the timing of the peak and the length or duration of the murmur corresponds to the severity of aortic stenosis. The more severe the stenosis, the longer the duration of the murmur and the more likely it peaks at mid-to-late systole.
• The murmur of valvular aortic stenosis is augmented upon squatting or following a premature beat; the murmur intensity is reduced during Valsalva strain, which is contrary to what occurs with hypertrophic obstructive cardiomyopathy where a Valsalva maneuver increases the intensity of the murmur.
• When the left ventricle fails and cardiac output falls, the aortic stenosis murmur becomes softer and may be barely audible. Atrial fibrillation with short R-R intervals can also decrease the murmur intensity or make it appear absent.
• Rarely, RV failure with systemic venous congestion, hepatomegaly, and edema precede LV failure. This is probably due to the bulging of the interventricular septum into the right ventricle, with impedance in filling, elevated jugular venous pressure, and a prominent a wave (Bernheim effect).

Causes

Most cases of aortic stenosis are due to the obstruction at the valvular level. Common causes are summarized inTable 1. Valvular aortic stenosis can be either congenital or acquired.

• Congenital valvular aortic stenosis
• Congenitally unicuspid, bicuspid, tricuspid, or even quadricuspid valves may be the cause of aortic stenosis. In neonates and infants younger than 1 year, a unicuspid valve can produce severe obstruction and is the most common anomaly in infants with fatal valvular aortic stenosis.
• In patients younger than 15 years, unicuspid valves are most frequent in cases of symptomatic aortic stenosis.
• In adults, congenital aortic stenosis is usually due to a bicuspid valve. It does not cause significant narrowing of the aortic orifice during childhood. The altered architecture of the bicuspid aortic valve induces turbulent flow with continuous trauma to the leaflets, ultimately resulting in fibrosis, increased rigidity and calcification of the leaflets, and narrowing of the aortic orifice in adulthood.
• Congenitally malformed tricuspid aortic valves with unequally sized cusps and commissural fusion can also cause turbulent flow leading to fibrosis and, ultimately, to calcification and stenosis. Clinical manifestations of congenital aortic stenosis in adults usually occur after the fourth decade of life.
• Acquired valvular aortic stenosis
• The main causes of acquired aortic stenosis include rheumatic heart disease and senile degenerative calcification.
• In rheumatic aortic stenosis, the underlying process includes progressive fibrosis of the valve leaflets with varying degrees of commissural fusion, often with retraction of the leaflet edges and, in certain cases, calcification. As a consequence, the rheumatic valve often is regurgitant and stenotic. Coexistent mitral valve disease is common.
• Degenerative (senile) calcific aortic stenosis involves progressive calcification of the leaflet bodies resulting in limitation of the normal cusp opening during systole. This represents a consequence of long-standing hemodynamic stress on the valve and is currently the most frequent cause of aortic stenosis requiring aortic valve replacement. It usually occurs in individuals older than 75 years. Cellular aging and degeneration have been implicated. Diabetes mellitus and hypercholesterolemia are risk factors for the development of this lesion. The calcification may also involve the mitral annulus or extend into the conduction system, resulting in atrioventricular or intraventricular conduction defects.
• The available data suggest that the development and progression of calcific aortic stenosis are due to an active disease process at the cellular and molecular level that shows many similarities with atherosclerosis, ranging from endothelial dysfunction to, ultimately, calcification.
• Calcific aortic valve disease is associated with older age, male sex, serum LDL and Lp(a) levels, systemic arterial hypertension, diabetes mellitus, and smoking.
• Other infrequent causes of aortic stenosis include obstructive vegetations, homozygous type II hypercholesterolemia, Paget disease, Fabry disease, ochronosis, and irradiation.