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Valvular heart disease: Clinical practice



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Valvular heart disease: Clinical practice


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USMLE® Step 2 style questions USMLE

12 questions

A 52-year-old woman comes to the dental clinic because of severe pain in the left second molar. She was diagnosed with grade III periodontitis and was advised to undergo extraction of her teeth. She has a history of diabetes and mitral valve prolapse. She has an allergy to amoxicillin, but is curious if she needs antibiotic prophylaxis. Which of the following prophylactic antibiotic regimens would be appropriate for this patient prior to tooth extraction?


Content Reviewers:

Rishi Desai, MD, MPH

Valvular heart disease involves damage or a defect in one or more of the four valves of the heart, so the aortic and bicuspid or mitral valves on the left side of the heart, and the pulmonary and tricuspid valves on the right side of the heart.

Normally, the valvular leaflets are very thin and when the cusps close they're perfectly apposed.

Valvular heart diseases are divided into stenosis - in which there’s narrowing of the valvular orifice that prevents adequate outflow of blood - and insufficiency or regurgitation, in which the valvular leaflets fail to close correctly and are unable to prevent backflow of blood.

These two are not mutually exclusive, which means they can both be present in the same individual and even in the same valve, for instance if thickening of the leaflets results in inappropriate closure as well as a narrow orifice.

Individuals with valvular heart disease are generally asymptomatic for a prolonged period, even for decades, and as soon as they become symptomatic, their life expectancy deteriorates very quickly.

The main symptoms are dyspnea, syncope, and angina. Both stenosis and regurgitation lead to turbulent flow when blood flows across the affected valve, which produces heart sounds called pathologic murmurs that are loud enough to be heard upon auscultation with a stethoscope.

When presentation suggests valvular heart disease, you should proceed with echocardiography to confirm the diagnosis of valvular disease and determine its severity.

A transthoracic echocardiogram is typically done, but a transesophageal echocardiogram may be needed in selected individuals, like those with a nondiagnostic transthoracic echocardiogram.

Doppler echocardiography allows determination the speed and direction of blood flow, which makes it the most sensitive noninvasive technique for detecting the regurgitant jet.

In some cases cardiovascular magnetic resonance imaging may be indicated to quantify the severity, measure left ventricular diastolic and systolic volumes, and assess left ventricular systolic function.

And as a last resort, cardiac catheterization is indicated when noninvasive tests are inconclusive or provide discrepant results, or for coronary angiography prior to valve surgery in patients at risk for coronary disease.

Cardiac catheterization allows you to measure pressure waveforms, which are indirect measurements of the left atrial pressure.

All right, onto aortic stenosis, which is the most common cause of valvular heart disease.

Typically, the three leaflets of the aortic valve get thick and calcified and don’t open all the way, making it harder to pump blood out to the body.

Most often, the aortic valve is tricuspid, but in some people it may be unicuspid, bicuspid, or quadricuspid.

Valves with different number of cusps than tricuspid, degenerate much more easily. Valve degeneration is usually due to wear and tear, and atherosclerosis, so these patients tend to be older.

In aortic stenosis, the pulse is described as being “parvus and tardus”.

That’s because the valve doesn’t fully open so there’s less blood flow and the pulse is weak - “parvus”, and there’s a delay in the opening of the valve which causes a mid systolic “crescendo-decrescendo” murmur that occurs a bit later than expected in systole - “tardus”.

This murmur mirrors the ejection of blood from the ventricle into the aorta: it increases with increasing pressure of ejection and decrease as ejection pressure decreases.

In aortic stenosis, thicker leaflets due to calcification are usually visible, as calcium on echo is brightly white, and the opening of the valve is also greatly reduced.

Doppler echocardiography permits measurement of jet velocity of blood and calculation of the left ventricular-aortic gradient and the valve area, which are the standard parameters used for evaluation of stenosis severity.

The flow is very turbulent because of the stenotic valve, presenting as elevated jet velocity.

Blood pressure gradient is useful to understand the severity of the stenosis: usually the cutoff is a mean gradient higher than 40 mmHg.

The more severe the aortic stenosis the higher the blood pressure gradient.

Asymptomatic individuals are not treated, while symptomatic aortic stenosis is an indication for aortic valve replacement, choosing from manufactured mechanical valves, human donor valves, or tissue valves created from animal tissue.

Aortic valve replacement can be done either through open-heart surgery with surgical aortic valve replacement or SAVR, or through transcatheter aortic valve implantation or TAVl, which involves placing the valve through a catheter, typically through the transfemoral route in the upper leg.

SAVR and TAVI should be used in individuals who are likely to have a prolonged life expectancy of at least a year as well as an improved quality of life.

For those individuals, the benefit should be weighed against the risk of the procedure.

For individuals with low surgical risk, or if transfemoral TAVI is not feasible, SAVR is performed.

For individuals with intermediate or high surgical risk, or if SAVR is contraindicated, then TAVI is performed.

Medical therapy has limited utility in treating aortic stenosis, so it is given as a last resort to individuals that are not candidates for aortic valve replacement.

The medications used include digoxin, diuretics, ACE inhibitors, or angiotensin receptor blockers.

Now, in aortic regurgitation, the valve doesn’t close all the way during diastole, and blood leaks back from the aorta into the left ventricle.

That leads to progressive ventricular dilation to accommodate the increased blood volume.

The valve leaflets may be abnormal or may be normal but stretched apart due to dilation of the ascending aorta.

Abnormalities that may be seen include thickening, vegetations, calcification, and prolapsed or flail leaflets.

On physical examination, aortic regurgitation causes a collapsing pulse, or water hammer pulse.

To feel it, the individual must lie back and raise their arm vertically upward, and the examiner has to grasp the muscular part of the patient's forearm.

A water hammer pulse is felt as a tapping impulse that’s felt through the bulk of the muscles, because the blood that is pumped to the arm during systole is emptied back into the heart during diastole due to the effect of gravity on the raised arm.

Upon auscultation, there’s an early diastolic murmur due to the backflow, and since there’s more volume in the left ventricle when it contracts, there’s also an ejection systolic murmur.

The severity of aortic regurgitation is determined through echocardiography or cardiac magnetic resonance imaging, which specifically look at the volume of blood flowing back into the left ventricle with each beat.

The mainstay of treatment is aortic valve surgery, which is indicated in severe aortic regurgitation.

But if aortic regurgitation is not severe, or even if it is severe but doesn’t cause left ventricular dysfunction, then surgery is not recommended.

Instead, the individual is given medications like ACE inhibitors, angiotensin receptor blockers, or vasodilators if they have hypertension.

Now, if there’s severe aortic regurgitation and left ventricle impairment, and if the surgical risk is low, then aortic valve surgery is recommended.

Alternatively, if individuals have another indication for cardiac surgery, like concomitant disease of another valve, then aortic valve surgery may be done independent of severity.

Moving on to mitral regurgitation, it’s caused by imperfect closure of the mitral valve during systole, which causes backflow of blood from the left ventricle into the left atrium.