Acute Severe Aortic Regurgitation

I. Acute Severe Aortic Regurgitation: What every physician needs to know.

Acute severe aortic regurgitation (AR) comes about when there is rapid disruption of the anatomic integrity of the aortic valve. As a consequence, the sudden imposition of a large regurgitant volume leads to a precipitous increase in left ventricular diastolic pressure and a decrease in forward stroke volume. The clinical correlates include acute pulmonary edema and, on occasion, circulatory collapse.

However, not all patients present with acute respiratory failure and some may show clinical signs of biventricular heart failure without marked respiratory signs. The most common causes of acute severe AR include infective endocarditis and aortic dissection.

II. Diagnostic Confirmation: Are you sure your patient has Acute Severe Aortic Regurgitation?

A. History Part I: Pattern Recognition:

Clinical scenarios

Acute severe AR should be considered in the differential diagnosis of all patients who present with sudden unexplained hemodynamic collapse and respiratory failure.

  1. The most common clinical scenario in which acute severe AR is encountered is in the patient with established aortic valve endocarditis who manifests with rapid onset heart failure. Alternatively, patients who do not have an established diagnosis of endocarditis may present with fever, cardiorespiratory failure, and positive blood cultures. Pulmonary edema in the presence of a normal heart size on a chest radiograph may be the only clue to the diagnosis in this setting.

  2. The second circumstance in which a flail aortic valve leaflet is encountered is in the setting of acute type A aortic dissection, when the dissection extends into the base of the aortic leaflet. In this instance, there is usually a history of sudden, severe “tearing” chest and back pain with rapid onset respiratory failure.

  3. Acute severe AR may complicate blunt chest trauma (e.g., striking the steering wheel in the course of a motor vehicle accident) or deceleration injury, and should be considered if the patient presents with pulmonary congestion. A new diastolic murmur, particularly if it is accompanied by chest radiographic signs of pulmonary edema, should alert the clinician to the diagnosis. However, as noted above, even if the murmur is not appreciated, the constellation chest trauma and pulmonary congestion should raise suspicion of traumatic disruption of the aortic valve.

  4. Rarely, severe AR may develop abruptly following prolapse of a myxomatous fenestrated aortic cusp. Under these circumstances there is usually no antecedent history of an acute inciting process.

  5. Finally, severe AR may develop in the setting of aortic balloon valvotomy or transcatheter aortic valve replacement.

B. History Part 2: Prevalence:

Prevalence and risk factors

The true incidence and prevalence of acute severe AR is not known, but is clearly dependent on the incidence and prevalence of the causes of AR. Whereas the incidence of infective endocarditis appears to be unchanged from 1970 to 2000, the incidence of type A aortic dissection appears to be increasing over time.

Predisposing risk factors for infective endocarditis are believed to be structural cardiac abnormalities that disrupt the endocardium by means of high velocity jet injury in the presence of blood-borne bacteria that colonize the surfaces of the valve. The most common predisposing lesions for aortic valve endocarditis are congenitally bicuspid aortic valve and prosthetic heart valve.

The typical patient in the International Registry for Aortic Dissection was a male in his seventh decade with history of hypertension. Other risk factors include connective-tissue disorders, such as Marfan syndrome and Ehlers Danlos syndrome, a bicuspid aortic valve, or atherosclerotic disease.

Type A dissection occurs most frequently in two groups of patients, older men with a history of hypertension and younger patients with Marfan syndrome. In the latter group a family history of sudden unexplained death or a physical examination consistent with Marfan syndrome might raise the suspicion a dissection etiology for acute AR where it would not have been previously entertained.

C. History Part 3: Competing diagnoses that can mimic Acute Severe Aortic Regurgitation.

Differential diagnosis

A number of conditions should be considered when a patient presents with:

Scenario 1

Fever, leukocytosis, respiratory failure, and bilateral lung infiltrates on chest x-ray:

1. Bilateral pneumonia

2. Septicemia/systemic inflammatory response syndrome (SIRS)

3. Acute respiratory distress syndrome (ARDS)

4. Acute myocarditis

Differentiating these conditions from acute severe AR secondary to infective endocarditis may be difficult. Patients with bilateral pneumonia often have a history of aspiration, coughing purulent material, poor nutrition, and prolonged mechanical ventilation.

SIRS and ARDS occur in the setting of overwhelming infection, trauma, burns, pancreatitis and blood transfusions. A history of intravenous drug abuse, prior infective endocarditis or recent dental procedures, should alert the clinician to the possibility of aortic or mitral valve endocarditis.

The physical examination, electrocardiographic, and chest x-ray findings are often not helpful to confirm the diagnosis. However, the electrocardiogram (ECG) is often abnormal in patients with acute myocarditis.

Whereas patients with septicemia or SIRS often have warm extremities, patients with severe AR frequently exhibit cold and clammy limbs. Laboratory data such as elevated natriuretic peptide levels may be helpful, but it should be kept in mind that these peptide levels may also be elevated in patients with septicemia and SIRS. Elevated troponin levels may point to the diagnosis of myocarditis. The best approach is the have a high index of suspicion and to confirm the diagnosis with echocardiography.

Scenario 2:

Chest pain, circulatory collapse, and respiratory failure without signs of an inflammatory process:

  1. Myocardial infarction with or without mechanical complications, such as ventricular septal rupture or mitral papillary muscle rupture

  2. Pulmonary embolus

As stated earlier, type A aortic dissection is another important cause of acute severe AR. The diagnosis is usually evident when there is a clinical suspicion of aortic dissection and manifestations of pulmonary vascular congestion in the absence of characteristic electrocardiographic signs of myocardial ischemia.

Aortic dissection complicated by severe AR and involvement of the right coronary or left main ostium may masquerade as an acute myocardial infarction secondary to plaque rupture. Pulmonary embolism is not usually associated with signs of marked pulmonary vascular congestion.

Scenario 3:

Respiratory failure secondary pulmonary vascular congestion in the setting of normal-sized heart on chest x-ray:

1. Heart failure with preserved ejection fraction

2. Mitral stenosis

3. Recent onset left ventricular dysfunction

History of prior hospitalizations for heart failure, typical for patients with heart failure with a preserved ejection fraction, virtually excludes the diagnosis of severe AR as the cause of pulmonary congestion. Recent onset cardiomyopathy complicated by decompensated heart failure may be difficult to differentiate from acute severe AR. Respiratory failure in the setting of mitral stenosis invariably is seen in the setting of atrial fibrillation with a rapid ventricular response.

D. Physical Examination Findings.

Many of the characteristic physical findings of chronic, severe AR are often absent in acute AR. The constellation of tachycardia, absent or soft first heart sound, single component second heart sound, loud third heart sound, short to medium length decrescendo diastolic murmur, and a positive Duroziez sign are typical findings in acute severe AR.

Whereas most of the classic findings in chronic, severe AR depend on a widened pulse pressure, the pulse pressure is usually reduced, owing to a reduced stroke volume and increased peripheral vascular resistance in acute AR. Similarly, the typical decrescendo diastolic murmur of chronic AR may be truncated in acute AR because aortic and left ventricular diastolic pressure equilibrate rapidly (Figure 1).

Figure 1.

A. M-mode echocardiographic recording of the mitral valve. Note the premature or diastolic closure of the mitral valve (arrowed) prior to the onset of systole (R wave of QRS complex). IVS, intraventricular septum; PLVW, posterior left ventricular wall; MV, mitral valve. B. The hemodynamic correlate of premature or diastolic closure of the mitral valve is early pressure crossover between left ventricular (LV) and left atrial (equivalent to pulmonary artery occlusion pressure, PAOP). The pressure range is from 0 to 100 mmHg.

  • Other physical examination findings, such as fever and splinter hemorrhages, may be found in patients with endocarditis or absent pulses secondary to aortic dissection may be indicative of the cause of AR. Preclosure of the mitral valve caused by increased diastolic pressure from volume overload causes S1 to be soft or almost absent. Likewise an increasing P–R interval caused by a myocardial abscess also diminishes the intensity of S1. Both etiologies for a reduced S1 intensity require prompt aortic valve replacement.

E. What diagnostic tests should be performed?

1. What laboratory studies (if any) should be ordered to help establish the diagnosis? How should the results be interpreted?

E. Diagnostic tests

Laboratory tests

Routine laboratory tests should include complete blood counts, serum electrolytes, creatinine, and estimation of glomerular filtration rate, glucose, liver function tests, and urinary analysis. Blood cultures should be obtained when endocarditis is suspected.

Plasma levels of natriuretic peptides (B-type natriuretic and peptide [BNP] and N-terminal pro-BNP [NT-proBNP] are useful biomarkers when the etiology of respiratory failure is uncertain. A normal concentration in an untreated patient has a robust negative predictive value.

2. What imaging studies (if any) should be ordered to help establish the diagnosis? How should the results be interpreted?

Imaging studies

Chest x-ray: Bilateral pulmonary parenchymal infiltrates or pulmonary interstitial changes suggestive of pulmonary venous congestion are often found in a patients with acute AR. These findings are not specific for this condition and other confirmatory imaging tests are required. The finding of a widened mediastinum raises the specter of aortic root dilatation and dissection.

Echocardiography: A comprehensive two-dimensional transthoracic echocardiographic study will usually provide the diagnosis. In most instances, echocardiography will also provide information about the anatomic abnormality and characterization of the hemodynamic severity of aortic regurgitation.

Premature closure of the mitral valve, indicating significantly increased left ventricular filling pressure, can be easily demonstrated by M-mode echocardiography (Figure 1). Echocardiographic examination of the aortic valve in bacterial endocarditis generally shows evidence of infection.

When extravalvular extension is suspected, it is best to perform transesophageal imaging. In acute aortic regurgitation caused by acute dissection, the echocardiogram may disclose the size of the aortic root and the severity of AR. Spectral

Doppler ultrasound is also used to quantify the severity of aortic regurgitation. These techniques are particularly important when two-dimensional imaging is suboptimal.

Computerized tomography: This imaging modality is most useful when aortic dissection is suspected. It provides information about the size of the aortic root, the extent of dissection distally, and whether major arterial branches are involved.

Cardiac catheterization and coronary arteriography: Invasive cardiac imaging is not routinely performed and not necessary for the diagnosis or the treatment plan for acute AR.

III. Management.

A. Immediate management.

Almost all patients with acute AR exhibit tenuous hemodynamics, even if at first glance they appear to be stable. Initial stabilization is required in the intensive care unit before the diagnostic work-up for the underlying cause is commenced. Medical treatment is directed at reducing pulmonary venous congestion and maximizing cardiac output in an attempt to stabilize the hemodynamics prior to surgery.

Pulmonary artery catheter placement is likely to be helpful in patients in whom the response to vasodilator and other therapies may be difficult to predict. These patients are so tenuous that they can usually be better managed with hemodynamic data.

Intravenous vasodilator and diuretic therapy can be effective in this regard. Nitroprusside usually represents a stabilizing pharmacologic bridge to more definitive interventions (e.g., valve replacement). The endpoints of acute vasodilator therapy can vary somewhat from patient to patient, but reasonable hemodynamic endpoints include a reduction in left ventricular filling pressure to 15 mm Hg or less and an increase in cardiac output that would ensure adequate tissue oxygen delivery (usually a cardiac index >2.5 L/min/m2) while maintaining a systemic blood pressure of 90 mm Hg or higher.

The optimally effective and safe administration of nitroprusside often requires hemodynamic monitoring by means of intraarterial catheters. The initial dose of 0.10 to 0.20 μg/kg/min is gradually increased as needed to attain the desired clinical and hemodynamic effects.

However, if the cause of acute AR is aortic dissection, the use of vasodilators may increase aortic shearing force and worsen the dissection. This presents a difficult clinical dilemma. In dissection, beta blockade is used in conjunction with vasodilators to reduce blood pressure. However, in severe AR, the blood pressure is usually reduced to begin with. Thus acute AR due to dissection offers little opportunity of effective medical therapy, stressing the importance of immediate surgery.

Increasing the heart rate by atrial pacing has also been shown to decrease regurgitant volume, left ventricular end-diastolic pressure, and pulmonary venous pressure in patients who have severe AR. The principal aim of medical treatment is to optimize the patient’s preoperative clinical status, rather than to provide definitive treatment, which may potentially delay surgery.

Once an accurate preoperative diagnosis is made and initial stabilization with medical therapy has been achieved earlier rather than later, surgical intervention generally improves results and prevents the long-term complications of delayed operations in anatomically complex patients. The inherent operative risk is far greater for this group of patients than for those who have chronic severe AR. The increased risk is related to the hemodynamically unstable state and the coexisting pathologic abnormalities, such as infective endocarditis or aortic dissection.

B. Physical Examination Tips to Guide Management.

Apart from improvements in the respiratory status, as assessed by respiratory rate and oxygen requirements following vasodilator and decongestive therapy, the other physical examination findings are unlikely to change significantly during the course of medical management.

C. Laboratory Tests to Monitor Response To, and Adjustments in, Management.

  1. Serum blood tests: Frequent assessments of electrolytes and liver function tests during the early phase of stabilization is essential so that early signs of worsening renal or hepatic function can be monitored. Renal function may deteriorate as a result of either worsening hemodynamics, or following the use of antibiotics, or renal infarction secondary to septic emboli, or renal artery involvement in the setting of aortic dissection. Evidence of early hepatic dysfunction may herald the onset of spiraling multiorgan failure.

  2. Natriuretic peptides: There is no role for serial measurements of these peptides to monitor hemodynamic improvement.

  3. Blood cultures: While some practitioners firmly believe that repeat blood cultures in patients with infective endocarditis should show no growth prior to surgery, others have not insisted on this prior to valve surgery, especially when there is evidence of hemodynamic instability.

D. Long-term management.

E. Common Pitfalls and Side-Effects of Management

Common pitfalls

  1. The most common mistake in management of these patients is a false sense of security that a patient can wait for extended period of time for surgery after initial medical stabilization. The gain obtained by delaying surgery is minimal and the risk is substantial.

  2. Surgeons may be reluctant to intervene when there is early evidence of multiorgan failure with worsening renal and hepatic dysfunction. Although the risk is substantially higher in this subset of patients, stabilization with prolonged (>48 hours) medical therapy is unlikely to improve multiorgan failure and will only result in a much higher surgical mortality rate.

  3. Severe AR secondary to infective endocarditis deserves special mention. In the past, there has been reluctance among surgeons to operate early on patients who have infective endocarditis because of the presence of infected, friable tissue and hemodynamic instability. It was believed that implantation of a prosthesis in an infected area may lead to prosthetic endocarditis. These concerns have been shown to be unfounded, as judged by the results from several centers. Thus, procrastination in referral for surgery is not justified.

IV. Management with Co-Morbidities

V. Patient Safety and Quality Measures

A. Appropriate Prophylaxis and Other Measures to Prevent Readmission.

B. What's the Evidence for specific management and treatment recommendations?

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Rowe, GG, Afonso, S, Castillo, CA, McKenna, DH. "The mechanism of the production of Duroziez's murmur". N Engl J Med. vol. 272. 1965. pp. 1207-10.

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