Balance Week 4 LG1 Valvular Heart Disease

In mitral stenosis, which chamber initially experiences the greatest pressure overload?

Answer: The left atrium.

Extra Information:

• The narrowed mitral valve obstructs blood flow from the LA into the LV during diastole.

• LA pressure increases to maintain transmitral filling.

What is the characteristic murmur of mitral stenosis?

Answer: A low-pitched diastolic rumble at the apex, often preceded by an opening snap.

Extra Information:

• A loud S1 may also be present.

• The murmur is best heard in the left lateral decubitus position.

What is a common underlying cause of mitral stenosis?

Answer: Rheumatic heart disease.

Extra Information:

• The lecture's mitral stenosis case includes a history of childhood rheumatic fever.

How does mitral stenosis affect LV filling and cardiac output?

Answer: It obstructs diastolic LV filling, reducing preload and potentially decreasing cardiac output.

Extra Information:

• The LV may be relatively protected from direct pressure overload.
• The primary problem is filling across the stenotic valve.

Trace the hemodynamic consequences of progressive mitral stenosis.

Answer: Mitral obstruction → increased LA pressure → increased pulmonary venous pressure → pulmonary hypertension → eventual RV strain or failure.

Extra Information:

• Elevated pulmonary venous pressure explains dyspnea and pulmonary congestion.

Why does mitral stenosis cause left atrial enlargement?

Answer: The LA must maintain increased pressure to drive blood across the narrowed mitral valve.

Extra Information:

• Persistent pressure overload promotes LA enlargement.

Why does mitral stenosis predispose patients to atrial fibrillation?

Answer: Chronic LA enlargement promotes atrial electrical and structural remodeling.

Extra Information:

• AF can further compromise LV filling.
• LA enlargement and AF also increase thromboembolic risk.

Why is tachycardia particularly harmful in mitral stenosis?

Answer: It shortens diastole, leaving less time for blood to cross the narrowed mitral valve.

Extra Information:

• LA pressure rises further while LV filling may decrease.
• Pulmonary congestion can worsen rapidly.

Why can the onset of atrial fibrillation cause acute pulmonary edema in severe mitral stenosis?

Answer: Loss of atrial contraction and a rapid ventricular rate reduce LV filling and increase LA and pulmonary venous pressures.

Extra Information:

• The lecture's patient deteriorates after converting from sinus rhythm at 76/min to AF at 145/min.

Why is preserving sinus rhythm beneficial in mitral stenosis?

Answer: Atrial contraction helps move blood across the narrowed valve during diastole.

Extra Information:

• Preserving an appropriate heart rate also allows more time for transmitral filling.

Why can mitral stenosis cause hemoptysis?

Answer: Elevated pulmonary venous pressure can cause congestion and rupture of small pulmonary or bronchial vessels.

Extra Information:

• The lecture's case includes blood-streaked sputum and elevated pulmonary pressures.

What echocardiographic findings were reported in the lecture's severe mitral stenosis case?

Answer: Mitral valve area 0.9 cm², mean gradient 12 mmHg, marked LA enlargement and elevated pulmonary pressures.

Extra Information:

• The findings support substantial obstruction to LV filling.

During which phase of the cardiac cycle does mitral regurgitation occur?

Answer: Systole.

Extra Information:

• The LV ejects blood forward into the aorta and backward into the LA.

What is the characteristic murmur of mitral regurgitation?

Answer: A holosystolic murmur best heard at the apex, commonly radiating to the axilla.

Extra Information:

• Its timing corresponds to systolic LV-to-LA regurgitation.

What are important causes of mitral regurgitation in the slides?

Answer: Mitral valve prolapse, ischemic papillary muscle dysfunction, papillary muscle rupture, endocarditis and LV dilation.

Extra Information:

• LV dilation can cause functional MR even without primary leaflet disease.

How can an inferior myocardial infarction cause mitral regurgitation?

Answer: Ischemic papillary muscle dysfunction or rupture can prevent normal mitral valve closure.

Extra Information:

• Acute papillary muscle rupture is a life-threatening cause of severe MR.

Which chambers experience volume overload in chronic mitral regurgitation?

Answer: Both the LA and LV.

Extra Information:

• The LA receives regurgitant blood during systole.
• That additional blood returns to the LV during the next diastole.

How does the LA compensate for chronic mitral regurgitation?

Answer: It gradually enlarges and becomes more compliant.

Extra Information:

• Greater compliance allows it to accommodate regurgitant volume with a smaller initial pressure increase.

How does the LV compensate for chronic mitral regurgitation?

Answer: It dilates and develops eccentric remodeling, increasing total stroke volume.

Extra Information:

• The increased total stroke volume helps preserve forward cardiac output despite backward flow.

Why does LV end-diastolic volume increase in chronic mitral regurgitation?

Answer: The LV receives normal pulmonary venous return plus the regurgitant blood that returns from the LA.

Extra Information:

• This produces chronic LV volume overload.

How can chronic MR preserve forward cardiac output despite regurgitation?

Answer: The LV increases total stroke volume so enough blood still enters the aorta after the regurgitant volume is subtracted.

Extra Information:

• Forward stroke volume equals total stroke volume minus regurgitant stroke volume.

In the lecture's compensation example, what happens if total stroke volume is 70 mL and 25 mL regurgitates?

Answer: Forward stroke volume is only 45 mL.

Extra Information:

• Forward stroke volume = 70 − 25 = 45 mL.

In the lecture's compensation example, what total stroke volume restores 70 mL of forward flow when 25 mL regurgitates?

Answer: A total stroke volume of 95 mL.

Extra Information:

• The LV compensates by increasing filling and total ejected volume.

What are the lecture's numerical values for moderate chronic MR?

Answer: Regurgitant fraction 35%, LVEDV 150 mL, total SV 105 mL, forward SV 68 mL, HR 82/min, CO 5.6 L/min and LAP 11 mmHg.

Extra Information:

• The example illustrates compensation through increased LVEDV and total stroke volume.

What are the lecture's numerical values for acute MR?

Answer: Regurgitant fraction 35%, LVEDV 100 mL, total SV 60 mL, forward SV 39 mL, HR 90/min, CO 3.5 L/min and LAP 18 mmHg.

Extra Information:

• The example illustrates lower forward output and higher LA pressure without chronic remodeling.

Why can acute severe MR cause a much greater LA pressure rise than chronic MR?

Answer: The normal-sized LA has not had time to dilate or increase its compliance.

Extra Information:

• A sudden regurgitant volume therefore produces a steep pressure increase.

Trace the mechanism of pulmonary edema in acute severe MR.

Answer: Sudden LV-to-LA regurgitation → abrupt LA pressure increase → pulmonary venous pressure increase → pulmonary edema.

Extra Information:

• The patient may also develop severe hypoxemia.

Why does acute severe MR reduce forward cardiac output?

Answer: A substantial portion of LV stroke volume is diverted into the LA before compensatory LV dilation can develop.

Extra Information:

• Hypotension and cardiogenic shock may result.

How do the chest radiographs in the lecture compare acute and chronic MR?

Answer: Acute MR shows marked pulmonary congestion, while chronic MR demonstrates a larger cardiac silhouette with less acute congestion.

Extra Information:

• The slide reports oxygen saturation of 84% on room air in acute MR versus 97% in chronic MR.

Why can chronic MR remain relatively asymptomatic for years?

Answer: LA compliance and LV eccentric remodeling initially maintain tolerable filling pressures and forward cardiac output.

Extra Information:

• Symptoms develop as compensatory mechanisms become insufficient.

Why can an EF of 55% be concerning in significant chronic MR?

Answer: EF includes blood ejected backward into the low-pressure LA, so it can overestimate effective LV systolic performance.

Extra Information:

• A seemingly normal EF can conceal declining forward pump function.

How does handgrip generally affect the MR murmur?

Answer: It increases the murmur.

Extra Information:

• Handgrip increases systemic vascular resistance, favoring greater backward flow into the LA.

How does vasodilation generally affect mitral regurgitation?

Answer: It reduces excessive afterload and can decrease regurgitant flow while promoting forward ejection.

Extra Information:

• The hemodynamic response depends on the cause and severity of MR.

How does standing generally affect the MR murmur?

Answer: It generally decreases the murmur.

Extra Information:

• Standing reduces venous return and LV filling.

How does squatting generally affect the MR murmur?

Answer: It generally increases the murmur.

Extra Information:

• Squatting increases venous return and systemic vascular resistance.

What is the primary hemodynamic defect in aortic stenosis?

Answer: Fixed obstruction to LV outflow during systole.

Extra Information:

• The narrowed aortic valve creates increased resistance to LV ejection.

What are important causes of aortic stenosis?

Answer: Degenerative calcific disease, congenital bicuspid aortic valve and rheumatic valve disease.

Extra Information:

• The lecture's symptomatic AS case involves a 76-year-old patient.

What is the primary ventricular load in aortic stenosis?

Answer: LV pressure overload.

Extra Information:

• The LV must generate high systolic pressure to eject blood through the narrowed valve.

What remodeling pattern compensates for chronic aortic stenosis?

Answer: Concentric LV hypertrophy.

Extra Information:

• Wall thickness increases in response to chronic pressure overload.

How does concentric hypertrophy initially help in aortic stenosis?

Answer: Increased wall thickness helps counteract elevated ventricular wall stress.

Extra Information:

• The relationship follows the Laplace wall-stress principle.

What is the main diastolic disadvantage of concentric LV hypertrophy?

Answer: The thickened LV becomes stiff and less compliant.

Extra Information:

• Higher filling pressures are needed to achieve adequate end-diastolic volume.

How does aortic stenosis affect the LV pressure-volume loop?

Answer: LV systolic pressure increases, end-systolic volume rises and stroke volume decreases.

Extra Information:

• Increased outflow resistance reduces the velocity of myocardial fiber shortening.

Why can LV end-systolic volume increase in aortic stenosis?

Answer: Increased afterload makes it harder for the LV to eject blood completely.

Extra Information:

• The resulting decrease in stroke volume narrows the pressure-volume loop.

What is the classic symptom triad of symptomatic aortic stenosis?

Answer: Angina, syncope and exertional dyspnea.

Extra Information:

• These reflect myocardial ischemia, limited forward flow and elevated filling pressures.

What is the characteristic murmur of aortic stenosis?

Answer: A harsh crescendo-decrescendo systolic ejection murmur at the right upper sternal border radiating to the carotids.

Extra Information:

• Severe disease may also produce a soft A2.

What is pulsus parvus et tardus?

Answer: A low-amplitude, delayed carotid pulse.

Extra Information:

• It reflects slow and limited LV ejection through a stenotic aortic valve.

Why can exertion cause syncope in severe aortic stenosis?

Answer: Fixed LV outflow obstruction limits the increase in cardiac output needed during exertion.

Extra Information:

• Exercise-related peripheral vasodilation can further reduce arterial pressure and cerebral perfusion.

How does concentric LV hypertrophy increase myocardial oxygen demand?

Answer: Increased myocardial mass and the high pressure required for ejection increase myocardial workload.

Extra Information:

• Oxygen demand can become excessive during exertion.

Why can aortic stenosis cause angina without obstructive coronary artery disease?

Answer: Increased myocardial oxygen demand can exceed the oxygen supply available to the hypertrophied LV.

Extra Information:

• Elevated LV filling pressure can also reduce the coronary perfusion gradient.

Why is coronary perfusion vulnerable to hypotension in severe aortic stenosis?

Answer: Reduced aortic diastolic pressure decreases the driving pressure for coronary blood flow.

Extra Information:

• Elevated LV diastolic pressure further reduces the effective coronary perfusion gradient.

Why is tachycardia poorly tolerated in severe aortic stenosis?

Answer: It shortens diastole, reducing LV filling time and coronary perfusion time.

Extra Information:

• The stiff hypertrophied LV is especially dependent on adequate filling.

Why is maintaining sinus rhythm important in severe aortic stenosis?

Answer: Atrial contraction helps fill the stiff, poorly compliant LV.

Extra Information:

• Loss of atrial contraction can substantially reduce preload and cardiac output.

Why must preload and systemic vascular resistance be maintained in severe aortic stenosis?

Answer: Adequate preload supports filling, while adequate SVR maintains arterial pressure and coronary perfusion.

Extra Information:

• The lecture's perioperative case illustrates the danger of sudden hypotension and tachycardia.

How does aortic regurgitation differ fundamentally from aortic stenosis?

Answer: AR is a diastolic volume-overload lesion, whereas AS is a systolic pressure-overload lesion.

Extra Information:

• Chronic AR produces LV dilation, while AS produces concentric LV hypertrophy.

What happens to blood flow in aortic regurgitation?

Answer: Blood leaks from the aorta back into the LV during diastole.

Extra Information:

• The aortic valve fails to seal completely.

What are important causes of aortic regurgitation?

Answer: Valve disease or damage, infective endocarditis and aortic root disease, including aortic dissection.

Extra Information:

• Endocarditis and dissection are especially important causes of acute severe AR.

What is the characteristic murmur of aortic regurgitation?

Answer: A high-pitched, blowing, early diastolic decrescendo murmur along the left sternal border.

Extra Information:

• Severe AR may also produce an apical Austin Flint murmur.

Why does chronic aortic regurgitation produce a wide pulse pressure?

Answer: Increased total stroke volume raises systolic pressure while diastolic runoff into the LV lowers aortic diastolic pressure.

Extra Information:

• Bounding peripheral pulses are a characteristic finding.

What remodeling pattern compensates for chronic aortic regurgitation?

Answer: LV dilation with eccentric hypertrophy.

Extra Information:

• The enlarged LV accommodates increased diastolic volume and ejects a larger total stroke volume.

How does chronic AR initially preserve forward cardiac output?

Answer: The compliant, dilated LV increases total stroke volume to compensate for the blood that regurgitates.

Extra Information:

• Symptoms may therefore be delayed for years.

How does chronic AR affect LV end-diastolic volume and total stroke volume?

Answer: Both increase.

Extra Information:

• The LV fills with pulmonary venous return plus blood returning from the aorta.

Why does acute severe AR cause a rapid increase in LV end-diastolic pressure?

Answer: A large regurgitant volume suddenly enters an LV that has not had time to dilate or become more compliant.

Extra Information:

• Pulmonary edema and hypotension can follow.

Why may acute severe AR have less dramatic bounding pulses than chronic AR?

Answer: The LV has not developed the large compensatory stroke volume characteristic of chronic disease.

Extra Information:

• Forward output may instead be severely reduced.

Why can the murmur of acute severe AR be less impressive than expected?

Answer: Rapid elevation of LV diastolic pressure reduces the aorta-to-LV pressure gradient during diastole.

Extra Information:

• The murmur can therefore be shorter or softer despite severe regurgitation.

How do acute and chronic AR differ in their initial cardiac compensation?

Answer: Chronic AR permits LV dilation and increased compliance, while acute AR occurs before these adaptations develop.

Extra Information:

• Acute severe AR is consequently much more likely to cause abrupt pulmonary edema and shock.

Why does marked bradycardia worsen aortic regurgitation?

Answer: A slower heart rate prolongs diastole, allowing more time for blood to regurgitate into the LV.

Extra Information:

• The lecture specifically emphasizes avoiding marked bradycardia.

Why is reducing excessive afterload beneficial in aortic regurgitation?

Answer: Lower systemic resistance favors forward LV ejection and can reduce the fraction of blood that regurgitates.

Extra Information:

• Preserving contractility also supports forward output.

What is the main hemodynamic management goal in mitral regurgitation?

Answer: Promote forward LV ejection by avoiding excessive afterload and controlling volume overload.

Extra Information:

• Reducing systemic resistance can decrease the tendency for blood to flow backward into the LA.

Why can afterload reduction improve forward flow in MR?

Answer: Lower aortic resistance makes forward ejection more favorable relative to regurgitation into the LA.

Extra Information:

• The benefit is particularly relevant when systemic resistance is elevated.

Why are diuretics used in symptomatic MR or AR with congestion?

Answer: They reduce excess intravascular volume and pulmonary congestion.

Extra Information:

• Diuretics relieve symptoms but do not repair the incompetent valve.

What is the main hemodynamic management goal in aortic regurgitation?

Answer: Reduce excessive afterload, preserve forward contractility and avoid marked bradycardia.

Extra Information:

• A shorter diastolic regurgitation period can reduce backward flow.

Why must volume reduction be individualized in regurgitant valve disease?

Answer: Excessive diuresis can reduce preload and compromise forward cardiac output.

Extra Information:

• The goal is to relieve congestion without causing harmful volume depletion.

Why can medication alone be insufficient in severe symptomatic MR or AR?

Answer: Medication can improve loading conditions and symptoms but does not eliminate the structural valve defect.

Extra Information:

• Severe disease may require definitive valve repair or replacement.