Acute Presentations of Valvular Heart Disease

Clinical Presentation

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  Aortic regurgitation (AR) occurs as a result of either dilation of the aortic root or disruption of the valve leaflets.

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  The most common etiologies are infective endocarditis (IE) and aortic dissection (AD).

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    IE is more likely in a prediseased valve and AR occurs through endothelial damage, nonbacterial thrombotic vegetation, adherence of organisms, proliferation of infection, and valve destruction.

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    Acute, type A, AD is complicated by AR in 50% of cases.

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      AD can lead to AR by direct extension of the dissection to the base of the aortic valve (AoV) leaflets, dilation of the sinuses with leaflets, incomplete coaptation, involvement of a valve commissure, and/or prolapse of the dissection flap across the AoV.

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    Other etiologies are listed in Table 14.1 .

    Table 14.1

    Etiologies of Acute Aortic Regurgitation

    1.	Infective endocarditis
    2.	Aortic dissection—predisposing and associated conditions	Hypertension Marfan syndrome Bicuspid aortic valve Coarctation of aorta Ehler-Danlos syndrome Turner syndrome
    3.	Chest trauma
    4.	Rupture of a myxomatous valve
    5.	Systemic connective tissue disorders	Ankylosing spondylitis Systemic lupus erythematosus
    6.	Granulomatous diseases	Tertiary syphilis Giant cell arteritis Takayasu arteritis

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  The clinical features of AR are profoundly different in the acute setting, including a markedly elevated left ventricular end-diastolic pressure (LVEDP), but absent wide pulse pressure.

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  Acute AR on the unprepared left ventricle (LV) may lead to the rapid onset of acute heart failure (HF) or cardiogenic shock.

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  Patients typically present with dyspnea, weakness, or hypotension and are often misdiagnosed with sepsis, pneumonia, or nonvalvular heart disease.

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    They are often tachycardic.

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    The LV impulse may be normal in both location and duration.

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    The first heart sound is often soft or inaudible.

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    Occasionally, mitral valve (MV) closure may be heard during diastole and accompanied by mitral regurgitation (MR).

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    The Austin-Flint murmur, which is thought to represent turbulent flow from the left atrium (LA) to the LV because of partial MV closure from the AR jet, is either absent or brief.

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    An accentuated pulmonic closure sound suggests elevated pulmonary arterial pressure.

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    A third heart sound (S ₃ ) is frequently heard.

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    The acute AR murmur is characteristically short, early, and medium pitch.

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    Edema and weight gain are not often seen because there is inadequate time for salt and water retention.

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    The extremities may be cool and mottled owing to both poor cardiac output (CO) and elevated systemic vascular resistance (SVR).

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  Clinical features seen in acute and chronic AR are listed in Table 14.2 .

  Table 14.2

  Clinical Features of Severe Aortic Regurgitation

  Feature	Acute	Chronic
  Congestive heart failure	Rapid and sudden	Insidious
  Rhythm	Sinus tachycardia	Regular rate
  Point of maximal impulse	Not hyperdynamic and nondisplaced	Hyperdynamic and shifted inferolaterally
  Pulse pressure	Normal	Widened
  Heart sounds
  S 1	Soft or absent	Soft
  S 2	Soft A2, accentuated P2	Normal P2
  S 3	Present	Absent
  S 4	Absent	Usually absent
  Aortic regurgitation murmur	Soft, early	Holodiastolic
  Cardiac output	Decreased	Normal
  LVEDP	Increased	Normal
  LV size	Normal	Increased

  LV , Left ventricle; LVEDP , left ventricular end-diastolic pressure.

Pathophysiology

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  In acute, severe AR, increases in LV end-diastolic volume owing to regurgitant flow result in an abrupt rise in LVEDP ( Fig. 14.1 ).

  

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  Consequently, a rapid increase in the ventriculoatrial (VA) gradient can cause premature MV closure, preventing pulmonary edema.

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  However, a further rise in the VA gradient reopens the MV in late diastole, leading to diastolic MR.

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  Systolic MR can also manifest from the persistent VA gradient as a result of the high LVEDP level to the isovolumic contraction period during early systole.

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  This MR is usually effective in lowering the LVEDP and the LA essentially serves as a reservoir.

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  However, LA pressure may rise further, leading to pulmonary edema.

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  Coronary ischemia can complicate acute AR because a reduction in coronary flow leads to a decrease in myocardial perfusion, whereas an elevated LVEDP and tachycardia increase myocardial oxygen demand.

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  Diastolic coronary flow may be reduced by a reduction in diastolic blood pressure, elevation of LVEDP, and by the Venturi effect.

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  The supply-demand mismatch is worsened if coronary artery disease (CAD) is present or when AD impairs coronary flow.

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  To further complicate the picture, reflex sympathetic activation, in response to a reduction in CO and systemic blood pressure, produces tachycardia and increases SVR.

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  This worsens regurgitant flow and impedes ejection of blood from the LV to the aorta so that a rise in aortic systolic pressure is inhibited.

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  Aortic diastolic pressure usually does not fall significantly in the acute setting for two reasons:

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    The rapid increase in LVEDP reduces the driving gradient between the aorta and LV

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    Peripheral runoff is limited by an increase in SVR

Investigations

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  Initial diagnostic testing includes an electrocardiogram (ECG), chest radiograph, blood cultures (if IE is suspected or if the patient has a prosthetic valve), and a transthoracic echocardiogram (TTE).

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  An ECG is required in all patients with pulmonary edema, primarily to rule out acute myocardial infarction (MI).

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    The ECG in acute AR may be normal with left axis deviation. With early LV volume overload, there can be Q waves in leads I, aVL, and V ₃ to V ₆ .

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  The chest radiograph generally reveals a normal cardiac silhouette with evidence of pulmonary edema ( Fig. 14.2 ).

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    A widened aortic root suggests the presence of dissection.

  

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  TTE provides crucial information regarding the presence, severity, and etiology of the lesion.

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    With severe AR, in addition to visualizing the regurgitant jet, quantitative measurements, such as jet or vena contracta width, can be obtained ( Fig. 14.3 ).

    

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    A jet width greater than 65% of the LV outflow tract and vena contracta greater than 0.6 cm are consistent with severe AR.

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    Continuous wave Doppler is used to calculate the pressure half-time, with acute, severe AR, the rapid equilibration of aortic and LV diastolic pressure results in a pressure half-time of less than 300 msec.

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    Other supportive findings include premature MV closure and flow reversal in the descending aorta ( Fig. 14.4 ).

    

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    If TTE windows are limited, transesophageal echocardiography (TEE) may be required, which has increased sensitivity for evaluating the underlying etiology of AR, such as IE (vegetations or aortic root abscess; Fig. 14.5 ) or AD (dissection flap).

    

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  AD should be considered in the differential diagnosis of any acute AR, confirmed by computed tomography (CT), TEE, or magnetic resonance imaging.

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    TTE can be a very useful and quick tool for identifying AoV dysfunction, abnormalities in the proximal ascending aorta and a short segment of the descending aorta.

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      The sensitivity for diagnosing AD with a TTE is higher for type A AD at 78% to 100%, but for type B it is only 31% to 55%.

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      Thus, TTE should be used to evaluate complications, not diagnosis, of acute aortic syndrome (AAS).

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    TEE is highly accurate in detecting AAS owing to its ability to visualize both the ascending and descending aortas.

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    A true dissection flap features random mobility, constant echo intensity, and margination of flow on color flow imaging.

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    TEE can reach a sensitivity of 99% and a specificity of 89%.

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    However, owing to its requirement for a skilled operator and adequate sedation, CT is the preferred modality for evaluation of AD in the emergency department ( Fig. 14.6 ).

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      A contrast study is highly accurate, with a sensitivity and specificity of about 95% to 98%, and is able to provide the site and extent of the dissection.

    

Management

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  The principles of management include reducing pulmonary venous pressure, maximizing CO, and initiating therapy for any underlying disorder.

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  Invasive hemodynamic monitoring by placement of a Swan-Ganz pulmonary artery catheter is extremely helpful in that it allows the clinician to assess the response to therapy and gauge the tempo of the illness.

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  Medical therapy for HF caused by acute AR includes both loop diuretics and intravenous vasodilators and the hemodynamic response to this determines the urgency of surgical intervention.

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  In patients with acute AR, intravenous vasodilator therapy can significantly reduce pulmonary artery pressures and increase CO.

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    Nitroprusside is the vasodilator of choice.

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      The drug is started at 0.25 µg/kg/min intravenously and uptitrated by increments of 0.25 to 0.5 µg/kg/min with the goal of achieving optimal hemodynamics.

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      The speed of uptitration is dictated by the degree of hemodynamic compromise.

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    Intravenous diuretics should be initiated to induce a brisk sustained urine output.

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  Inotropic agents do not play a significant role in acute AR because most cases occur in the setting of normal or accentuated LV function.

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  However, if preexisting myocardial dysfunction exists, agents, such as dobutamine, at a dose of 5 to 15 µg/kg/min may assist in maintaining CO.

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  Intraaortic balloon pumps (IABPs) are contraindicated because balloon inflation during diastole would increase regurgitant flow.

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  Additional medical therapy includes appropriate antibiotics in suspected IE.

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  In the case of AD, intravenous β-blockers are thought to be useful in reducing the velocity of LV ejection, thereby minimizing aortic wall stress.

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  However, when AD is complicated by acute AR, β-blockers should be used cautiously, because the compensatory tachycardia would be blunted, further reducing CO.

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  If hemodynamic instability persists, emergent surgical valve repair or replacement represents the only curative option.

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  Indications for surgery in the presence of IE are outlined in Table 14.3 . Even in the presence of active IE, valve surgery should not be delayed.

  Table 14.3

  Indications for Surgery in Infective Endocarditis of Native or Prosthetic Valve

  From Nishimura RA, Otto CM, Bonow RO, et al. 2017 AHA/ACC Focused Update of the 2014 AHA/ACC Guideline for the Management of Patients With Valvular Heart Disease. J Am Coll Cardiol . 2017;70:252–289.

  Early Surgery (During Initial Hospitalization Before Completion of Full Antibiotic Course)
  Valve dysfunction causing heart failure symptoms (class I)
  Left-sided infective endocarditis caused by highly resistant organism (Staphylococcus aureus , fungi) (class I)
  Heart block, abscess, or destructive penetrating lesion (class I)
  Persistent infection (persistent bacteremia or fevers lasting longer than 5 to 7 days despite appropriate therapy; class I)
  Recurrent emboli and persistent vegetations despite appropriate antibiotic therapy (class IIa)
  Large (>10 mm) mobile vegetation on native valve (class IIb)
  Indication for surgery, but with complication of a stroke with no evidence of intracranial hemorrhage or extensive neurologic damage (class IIb)
  Surgery
  Relapsing prosthetic valve endocarditis (recurrence of bacteremia after completion of antibiotic course with subsequent negative blood cultures) (class I)
  Complication of major ischemic stroke or intracranial hemorrhage and hemodynamically stable, delay surgery for at least 4 weeks (class IIb)

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  The International Registry of Acute Aortic Dissection (1995–2013) analysis, demonstrated a decline in overall mortality for AD type A from 31% to 22%, driven mostly by a reduction in surgical mortality from 25% to 18%.

Clinical Presentation

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  Aortic stenosis (AS) is a progressive disorder characterized by narrowing of the AoV orifice resulting in dyspnea, angina, or syncope.

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  The etiology varies from an age-related degenerative process, chronic rheumatic heart disease, or congenital abnormalities in valve structure.

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  Physical examination of the patient with AS reveals a small-volume, slowly rising pulse.

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  The apical impulse of the heart may be displaced downward and to the left with a marked presystolic impulse or “a” wave.

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  The harsh ejection systolic murmur of AS is best heard at the base and is transmitted to the carotids.

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  In general, late peaking murmurs of longer duration signify more severe stenosis.

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  With decreasing CO, there is a fall in the gradient and in the intensity of the murmur.

Pathophysiology

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  Progressive valvular AS leads to increasing LV systolic pressure and so the LV hypertrophies to normalize wall stress.

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  But it also results in a shift of the LV pressure-volume curve upward and to the left; because of this, any diminution in preload will impair stroke volume (SV).

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  Therefore, acute volume reduction will result in a significant impairment of CO.

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  The altered LV pressure-volume relationship also makes LV preload critically dependent on atrial contraction.

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  Any impairment in the contribution of diastolic filling by atrial systole can lead to acute decompensation, increasing heart rate may impair LV filling simply by shortening diastole, and a markedly decreased heart rate will impair CO as it becomes heart rate dependent.

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  Any condition that further impairs LV relaxation (e.g., acute coronary ischemia) will also have a significant impact on diastolic filling.

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  Relative ischemia may also occur in the setting of normal coronary arteries or nonobstructive CAD when myocardial oxygen demands have exceeded coronary reserve.

Treatment

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  Atrial fibrillation should be treated with urgent synchronized cardioversion.

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  Atrioventricular (AV) conduction abnormalities should be managed with temporary pacing followed by a dual chamber permanent pacemaker if the disturbance persists.

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  Once the patient is stabilized, urgent valve replacement should be undertaken.

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  If there is a question of CAD, cardiac catheterization should be performed.

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  Valve replacement for AS includes surgical or transcatheter aortic valve replacement (TAVR).

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  Based on the updated 2020 American Heart Association/American College of Cardiology (AHA/ACC) guidelines for severe and symptomatic (stage D) aortic stenosis:

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    Surgical AVR is a class IA recommendation for patients less than 65 years of age.

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    TAVR is a class Ia recommendation for patients 65 to 80 years of age.

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    For patients at high surgical risk, TAVR are is a class IA recommendations.

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  Mechanical circulatory support approaches have emerged as a rescue therapy in critical AS with or without cardiogenic shock or as a bridge to TAVR.