Skip Navigation LinksHome > July 2013 - Volume 117 - Issue 1 > Intraoperative Diagnosis of Transient Pseudo-Severe Aortic S...
Anesthesia & Analgesia:
doi: 10.1213/ANE.0b013e3182945ba6
Cardiovascular Anesthesiology: Echo Rounds

Intraoperative Diagnosis of Transient Pseudo-Severe Aortic Stenosis

Gerlach, Rebecca M. MD; Tanzola, Rob MD, FRCPC; Allard, Rene MD, FRCPC

Free Access
Supplemental Author Material
Article Outline
Collapse Box

Author Information

From the Department of Anesthesiology, Kingston General Hospital, Queen’s University, Kingston, Ontario, Canada.

Accepted for publication October 23, 2012.

Published ahead of print May 17, 2013

Funding: None.

The authors declare no conflict of interest.

Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal’s Web site (www.anesthesia-analgesia.org).

Reprints will not be available from the authors.

Address correspondence to Rob Tanzola, MD, FRCPC, Department of Anesthesiology, Queen’s University, Anesthesiology, Victory 2, Kingston General Hospital, 76 Stuart St., Kingston, Ontario K7L 2V7, Canada. Address e-mail to tanzolar@kgh.kari.net.

Consent for publication of this case was obtained from the patient. A 67-year-old woman presented to the emergency department with a septic shoulder. During her assessment, she developed hypotension and acute pulmonary edema associated with significant inferior ST-depression on electrocardiogram. She was diagnosed with both septic and cardiogenic shock, requiring hemodynamic support and endotracheal intubation. Transthoracic echocardiography revealed severe left ventricular (LV) dysfunction with an ejection fraction (EF) of 10% to 15% (Video 1, see Supplemental Digital Content 1, http://links.lww.com/AA/A546) and severe aortic stenosis (AS) with an aortic valve area (AVA) by continuity equation of 0.63 cm2. The aortic valve (AV) mean pressure gradient was low, at 19 mm Hg. Two dimensional views of the AV were of poor quality (planimetry was not possible); however, images were consistent with thickened calcified AV cusps with restricted mobility. Pressure gradients across the AV were not measured at catheterization, but a proximal right coronary artery stenosis was stented. After surgical consultation, the decision was made to proceed with AV replacement (AVR) once she had recovered, because she had severe AS and LV systolic dysfunction (class I indication).1 Importantly, a follow-up transthoracic echocardiography was not performed after the resolution of her acute illness.

Two weeks after having returned to her preadmission functional status, she was brought to the operating room. A preincision transesophageal echocardiogram unexpectedly revealed near-normal LV function (Video 2, see Supplemental Digital Content 2, http://links.lww.com/AA/A547). The AV was not heavily calcified, having only moderate systolic cusp restriction. The AVA was 1.1 to 1.2 cm2 by planimetry and continuity equation (Fig. 1; Video 3, see Supplemental Digital Content 3, http://links.lww.com/AA/A548), and the mean gradient was 20 mm Hg. Comparative preoperative and intraoperative echocardiographic measurements are presented in Table 1. In light of the intraoperative findings of only moderate (and now asymptomatic) AS, and normal LV function, AVR was no longer indicated. Surgery was aborted, and the patient was discharged home.

Figure 1
Figure 1
Image Tools
Table 1
Table 1
Image Tools

Echocardiographic measures of severe AS include a jet velocity >4.0 m/s, a mean gradient of >40 mm Hg, an AVA of <1.0 cm2, and a dimensionless index (DI) of <0.25.1,2 One caveat is that the assessment of the severity of AS should be made, taking into consideration the underlying LV function. Under low-flow states, the mean AV gradient may be deceptively low in the setting of severe AS. The diagnostic criteria for this low-flow, low-gradient AS include: LVEF <40%, mean AV gradient <30 to 40 mm Hg, and AVA <1.0 cm2.3 Low-gradient AS can be further divided into those with true severe AS and those with pseudo-severe AS. In true severe AS, decreased EF results from failure of LV compensatory mechanisms that normally occur in response to chronic pressure overload (afterload mismatch). In pseudo-severe AS, the actual severity of AS is mild to moderate but it appears more severe due to LV dysfunction (e.g., myocardial infarction, cardiomyopathy) that does not provide enough force to fully open the diseased valve. Simply put, true severe AS is a primary AV problem leading to ventricular dysfunction, whereas pseudo-severe AS is primary ventricular dysfunction that gives the appearance of an AV problem. Although AVR is associated with better outcomes than medical management in low-gradient AS, it is important to distinguish true from pseudo-severe AS as the benefit of AVR in the latter is not definitive.4

Differentiating true severe AS from pseudo-severe AS is not straightforward. The traditional flow-dependent echocardiographic measures of AS severity (jet velocity and mean gradient) will yield, by definition, measurements in the nonsevere range. Both the AVA (by continuity and planimetry) and the DI (ratio of peak velocities or velocity time integrals at the LV outflow tract [LVOT] and AV) are touted as flow-independent measures to assess the severity of AS. Both AVA and DI, however, rely on a functional anatomical opening, and would therefore not be able to distinguish true severe AS from pseudo-severe AS. Thus, a valve that is unable to fully open due to low flow would still be expected to show an AVA and a DI in the severe range.5

To differentiate true severe AS from pseudo-severe AS, current guidelines recommend dobutamine stress echocardiography (DSE) as a method to increase transvalvular flow.1 In true severe AS, increased flow will result in an increase in mean gradient, a minimal change in AVA, and a maximum AVA <1.0 cm2 (Table 2). In contrast, with a pseudo-severely stenotic valve, the increased flow will augment its opening and result in minimal change in mean gradient, an increase in AVA, with an absolute value >1.0 cm2.5–7 DSE can be performed easily in the operating room and is useful when surgical urgency limits a full preoperative AV assessment.8 After baseline echocardiography measurements, dobutamine is titrated from 5 to 20 µg/kg/min, after which a second assessment of the valve is made. The infusion is stopped once cardiac output increases by 25% or if side effects, such as ischemia or arrhythmia, are encountered. In some patients, DSE assessment is indeterminate because of a lack of LV contractile reserve. In these cases, more sophisticated measurements have been developed but these are not easily performed intraoperatively.6

Table 2
Table 2
Image Tools

Reviewing the continuity equation is helpful in the understanding of the AVA findings in this case:

Equation (Uncited)
Equation (Uncited)
Image Tools

In this case, the recovery in LV function after resolution of the patient’s acute illness is analogous to improvement that can be observed with dobutamine infusion. With improved flow the LVOT velocity time integral (VTI) increased significantly, whereas improved opening of the AV resulted in only a relatively smaller increase in AV VTI (Table 1). Thus, the ratio of LVOT VTI to AV VTI (the DI) increases, resulting in the calculated AVA increasing from baseline. The mean gradient also remained relatively unchanged due to improved opening of the AV.

This unusual intraoperative diagnosis of pseudo-severe AS illustrates how altered physiology induced by acute myocardial dysfunction can affect the echocardiographic measures of AS severity. It emphasizes the importance of reassessing patients after the resolution of an acute event to confirm the findings of low-flow, low-gradient AS; to assess for myocardial recovery; and to exclude the presence of pseudo-severe AS to avoid unnecessary valve replacement.

Back to Top | Article Outline

Clinician’s Key Teaching Points

By Martin M. Stechert, MD, Donald Oxorn, MD, Martin J. London MD

* Although infrequently encountered, the subset of aortic stenosis (AS) patients presenting with low-flow, low-gradient AS poses a diagnostic challenge for the perioperative echocardiographer. Correctly differentiating the major subgroups of these patients may have important implications for perioperative management and long-term outcome.

* Low-flow, low-gradient AS occurs with decreased systolic function in the setting of true AS or with “pseudo-severe AS” where impaired systolic function results in the inability to open valve leaflets to their maximal extent that are otherwise only affected by moderate AS. Current guidelines recommend the use of dobutamine stress echocardiography to evaluate the patient’s contractile reserve. Impaired contractile reserve generally indicates pseudo-severe AS where surgical management is unlikely to be indicated.

* In this case of an elderly woman with septic shock and secondary cardiomyopathy (ejection fraction 10%–15%), the severity of her AS (0.63 cm2) was overestimated by transthoracic echocardiography examination during her acute illness with a resultant recommendation for valve replacement. After recovery from septic shock and heart failure, an intraoperative transesophageal echocardiogram immediately before skin incision revealed only moderate AS (1.1–1.2cm2), thereby avoiding unnecessary valve replacement. Although not performed, dobutamine stress echocardiography testing before the planned surgery may have been helpful.

* This case of pseudo-severe AS emphasizes the potential value of a complete transesophageal echocardiogram examination before a scheduled aortic valve replacement, particularly in patients with abnormal ventricular function. It also illustrates potential limitations of echocardiographic measurements, especially when assessing pressure gradients that may vary with cardiac output and impedance alterations, factors that may cause variability in measurements between preoperative and anesthetized states.

Back to Top | Article Outline

DISCLOSURES

Name: Rebecca M. Gerlach, MD.

Contribution: This author helped write and prepare the manuscript.

Attestation: Rebecca Gerlach approved the final manuscript.

Name: Rob Tanzola, MD, FRCPC.

Contribution: This author helped write and prepare the manuscript.

Attestation: Rob Tanzola approved the final manuscript.

Name: Rene Allard, MD, FRCPC.

Contribution: This author helped write and prepare the manuscript.

Attestation: Rene Allard approved the final manuscript.

This manuscript was handled by: Martin J. London, MD.

Back to Top | Article Outline

REFERENCES

1. Bonow RO, Carabello BA, Chatterjee K, de Leon AC Jr, Faxon DP, Freed MD, Gaasch WH, Lytle BW, Nishimura RA, O’Gara PT, O’Rourke RA, Otto CM, Shah PM, Shanewise JS, Nishimura RA, Carabello BA, Faxon DP, Freed MD, Lytle BW, O’Gara PT, O’Rourke RA, Shah PMAmerican College of Cardiology/American Heart Association Task Force on Practice Guidelines. . 2008 focused update incorporated into the ACC/AHA 2006 guidelines for the management of patients with valvular heart disease: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Writing Committee to revise the 1998 guidelines for the management of patients with valvular heart disease). Endorsed by the Society of Cardiovascular Anesthesiologists, Society for Cardiovascular Angiography and Interventions, and Society of Thoracic Surgeons. J Am Coll Cardiol. 2008;52:e1–142

2. von Homeyer P, Oxorn DC. Aortic stenosis: echocardiographic diagnosis. Anesth Analg. 2012;115:517–21

3. Tribouilloy C, Lévy F. Assessment and management of low-gradient, low ejection fraction aortic stenosis. Heart. 2008;94:1526–7

4. Fougères E, Tribouilloy C, Monchi M, Petit-Eisenmann H, Baleynaud S, Pasquet A, Chauvel C, Metz D, Adams C, Rusinaru D, Gueret P, Monin JL. Outcomes of pseudo-severe aortic stenosis under conservative treatment. Eur Heart J. 2012;33:2426–33

5. Burwash IG. Low-flow, low-gradient aortic stenosis: from evaluation to treatment. Curr Opin Cardiol. 2007;22:84–91

6. Blais C, Burwash IG, Mundigler G, Dumesnil JG, Loho N, Rader F, Baumgartner H, Beanlands RS, Chayer B, Kadem L, Garcia D, Durand LG, Pibarot P. Projected valve area at normal flow rate improves the assessment of stenosis severity in patients with low-flow, low-gradient aortic stenosis: the multicenter TOPAS (Truly or Pseudo-Severe Aortic Stenosis) study. Circulation. 2006;113:711–21

7. deFilippi CR, Willett DL, Brickner ME, Appleton CP, Yancy CW, Eichhorn EJ, Grayburn PA. Usefulness of dobutamine echocardiography in distinguishing severe from nonsevere valvular aortic stenosis in patients with depressed left ventricular function and low transvalvular gradients. Am J Cardiol. 1995;75:191–4

8. Maslow AD, Mahmood F, Poppas A, Singh A. Intraoperative dobutamine stress echocardiography to assess aortic valve stenosis. J Cardiothorac Vasc Anesth. 2006;20:862–6

Supplemental Digital Content

Back to Top | Article Outline

© 2013 International Anesthesia Research Society

Login

Become a Society Member