| JOURNAL HOME | CME HOME | THIS MONTH | PAST ISSUES | ETOC | COLLECTIONS |
| AUTHORS | REVIEWERS | EDITORIAL BOARD | FEEDBACK | RSS | HELP |
| ||||||||||||||
| ||||||||||||||
|
|
|
|
||||||||||||
|
||||||||||||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
From the Department of Anesthesiology, Henry Ford Hospital, Detroit, Michigan.
Address correspondence and reprint requests to Jonathan Frogel, MD, Henry Ford Hospital, Department of Anesthesiology, 2799 West Grand Blvd, Detroit, Michigan. Address e-mail to jfrogel1{at}hfhs.org.
A 64-yr-old man with a history of triple vessel coronary artery disease and moderate aortic insufficiency (AI) presented to our institution for aortic valve replacement and coronary artery bypass graft surgery. The pre-bypass intraoperative transesophageal echocardiography (TEE) revealed mild global hypokinesis with an ejection fraction of 40%–45% and 3+ central AI (video loop 1; please see video loop available at www.anesthesia-analgesia.org). There were no other significant valvular abnormalities. The pre-bypass cardiac output measured 6.0 L/min by thermodilution.
Pulsed wave Doppler (PWD) interrogation of mitral inflow demonstrated E:A reversal with decreased E-wave velocity, increased A wave velocity, and prolonged E wave deceleration time (Fig. 1A). In addition, PWD of the left upper pulmonary vein demonstrated diastolic blunting of pulmonary venous flow, suggesting impaired left ventricular (LV) relaxation (Fig. 1B). Furthermore, mitral annular tissue Doppler imaging (TDI) revealed an E' peak velocity of 7.75 cm/s (normal >8 cm/s), consistent with diastolic dysfunction (Fig. 2, Doppler and TDI variables of diastolic function). At the time of image acquisition, the patient's arterial blood pressure measured 105/52 mm Hg, central venous pressure was 8 mm Hg, and pulmonary artery pressure was 24/13 mm Hg.
|
|
The patient underwent four vessel coronary artery bypass grafting and aortic valve replacement with a 25-mm pericardial tissue valve (Thermafix®, Edwards Lifesciences, Irvine, CA) and was successfully weaned from bypass without pressor or inotropic support (video loop 2; please see video loop available at www.anesthesia-analgesia.org). The post-bypass TEE revealed a normally functioning bioprosthetic valve with no residual regurgitation or paravalvular leak. LV function remained essentially unchanged (ejection fraction of 45%), with well preserved contractile function and mild inferoseptal hypokinesis. The post-cardiopulmonary bypass cardiac output measured by thermodilution was 6.5 L/min. Doppler studies demonstrated normalization of both the transmitral diastolic filling pattern (Fig. 3A), and the left upper pulmonary vein flow (Fig. 3B). The post CPB TDI E' velocity was essentially unchanged (7.86 cm/s). At the time of image acquisition, the patient's arterial blood pressure measured 90/59 mm Hg, with a central venous pressure of 5 mm Hg and pulmonary artery pressure of 20/9 mm Hg.
|
The evaluation of mitral inflow with transmitral PWD is an important part of the intraoperative TEE examination that can aid in the assessment of LV diastolic function and mitral valve pathology. This case demonstrates the influence of aortic valve incompetence on transmitral flow. Severe acute AI leads to a mitral inflow pattern characterized by an increased E wave velocity, decreased A wave velocity and decreased E wave deceleration time.1 This effect may be caused by early mitral valve closure secondary to a rapid increase in LV pressure and competitive diastolic filling from the incompetent aortic valve in the setting of a relatively noncompliant LV. In chronic AI, increased LV compliance (when compared with acute aortic insufficiency) and remodeling prevents the rapid increase in left atrial pressure seen in acute AI. As a result, relatively decreased early filling (E wave), increased filling during atrial contraction (A wave) and an inverted E:A ratio on PWD interrogation of mitral inflow are observed.2
Post-CPB changes in loading conditions can alter transmitral and pulmonary venous flow dynamics, converting a pseudonormal pattern to an impaired relaxation pattern when preload is decreased or converting an impaired relaxation pattern to a pseudonormal pattern when left atrial pressure is increased. Furthermore, diastolic function typically worsens transiently in the immediate post-CPB period.3 In this case, the transition from an apparent impaired relaxation pattern to normal diastolic function after aortic valve replacement likely represents uncovering of the patient's normal baseline LV diastolic function.
AI may confound accurate evaluation of LV diastolic function when transmitral PWD is used alone or in conjunction with pulmonary venous Doppler. Although color M-mode propagation velocity and mitral annular tissue Doppler imaging are less load-dependent than transmitral and pulmonary venous Doppler evaluation, chronic AI can hinder their accuracy as measures of diastolic function. Color M-mode propagation velocity images can be difficult to obtain in patients with moderate to severe AI, particularly if the regurgitant jet crosses paths with mitral inflow. Patients with chronic moderate or severe AI also demonstrate alterations in TDI that may preclude adequate evaluation of diastolic function using this modality. Chronic LV volume overload secondary to AI may lead to compensatory longitudinal hypertrophy of the LV myocardium resulting in impaired diastolic relaxation in the longitudinal axis. TEE TDI of the lateral mitral annulus is a sensitive, relatively load-independent measure of longitudinal diastolic relaxation and function. As a result, patients with long standing AI will exhibit significantly decreased E' velocities when interrogated with this modality. In contrast, the circumferential myocardium is relatively well preserved in this subset of patients and, consequently, global diastolic function may be normal even in the presence of mitral TDI abnormalities.4 Indeed, despite normalization of transmitral and pulmonary vein Doppler variables suggesting normal diastolic function, this patient's TDI E' velocity remained essentially unchanged (7.86 cm/s) after aortic valve replacement.
LV diastolic dysfunction has been identified as an important predictor of difficult weaning from CPB as well as increased post-CPB pressor and inotrope requirements.5 Thus, the evaluation of LV diastolic function has become an integral part of the intraoperative TEE examination. As this report demonstrates, aortic regurgitation should be recognized as a possible impediment to the accurate evaluation of diastolic function in the perioperative setting.
Footnotes
This article has supplementary material on the Web site: www.anesthesia-analgesia.org.
Accepted for publication September 19, 2007.
REFERENCES
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
