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CARDIOVASCULAR ANESTHESIOLOGY

Left Ventricular Outflow Tract Obstruction After Mitral Valve Replacement

From the Department of Anaesthesia; Trent Cardiac Centre, Nottingham University Hospital Trust, City Hospital Campus, Hucknall Road NG5 1PB, Nottinghamshire, United Kingdom.

Address Correspondence to: Prabhat Tewari, MD, Department of Anaesthetics, Trent Cardiac Centre, Nottingham University Hospital Trust, City Hospital Campus, Hucknall Road NG5 1PB, Nottinghamshire, United Kingdom. Address e-mail to ptewari123{at}yahoo.co.in; ptewari{at}sgpgi.ac.in.

A 68-yr-old man presented with a 1-yr history of exertional dyspnea. Five years previously he had contracted endocarditis for which he underwent mitral valve replacement (MVR) with the native leaflet preservation technique. During his current hospitalization, preoperative transthoracic echocardiography demonstrated a gradient of 50 mm Hg across the left ventricular (LV) outflow tract (LVOT) with no evidence of aortic valve disease. There appeared to be a mobile strand attached to the subvalvular aspect of his mitral valve prosthesis (29 mm Carpentier–Edwards pericardial stented valve). Suspecting a healed endocarditis strand, he was scheduled for a redo MVR via a transeptal approach.

In the operating room a transesophageal echocardiography (TEE) examination was done before cardiopulmonary bypass. Two-dimensional midesophageal (2D ME) five chamber (Fig. 1) and 2D ME long axis views revealed a long anterior mitral leaflet (AML)-like structure (2.71 cm in 2D ME five chamber view) attached to the base of the mitral valve prosthesis. On further interrogation this structure seemed to be attached to the papillary muscles with chordae-like strands (please see videos clip available at www.anesthesia-analgesia.org). The structure extended well into the LVOT during systole, causing a gradient of 40 mm Hg with continuous wave Doppler (CWD) and showing turbulence on color flow Doppler (please see videos clip available at www.anesthesia-analgesia.org). The prosthetic valve was seated well, had good leaflet excursion, sharp margins, and minimal transvalvular gradient. There was no paravalvular or significant transvalvular regurgitation. On the basis of the TEE findings, the surgical team changed its plan to cut this structure out through an aortotomy leaving the prosthetic valve untouched. At surgery, the structure was confirmed to be a redundant AML with elongated chordae. The postcardiopulmonary bypass TEE gradient across the LVOT was <6 mm Hg (Fig. 2). The patient made an uneventful recovery.

View larger version (26K): [in this window] [in a new window]   Figure 1. Precardiopulmonary bypass midesophageal 5-chamber view at 0° showing the anterior mitral leaflet in the left ventricular outflow tract (LVOT): LA = left atrium; LV = left ventricle; RV = right ventricle.

View larger version (32K): [in this window] [in a new window]   Figure 2. Continuous wave Doppler flow profile across the left ventricular outflow tract showing higher flow velocity precardiopulmonary bypass (Left panel, transgastric long axis view), which was normalized postcardiopulmonary bypass (right panel, deep transgastric view).

Elevated LVOT gradients after MVR can occur for a variety of reasons. Fixed LVOT obstruction (LVOTO) is sometimes found with high profile bioprosthetic valves, like the Carpentier–Edwards used in this patient. This occurs because of incorrect orientation resulting in the strut impinging on the LVOT.1 Dynamic LVOTO, after MVR, can occur with a narrowed mitral-aortic angle, thickened interventricular septum, systolic anterior motion of the preserved AML, small hyper contractile LV and also with atrial fibrillation.2 Pharmacological attenuation of dynamic obstruction with the use of β-blockers and vasoconstrictors along with adequate fluid therapy is sometimes successful in providing symptomatic relief.

In addition to measuring the gradient across the LVOT, the shape of the CWD flow profile can be useful in differentiating a dynamic LVOTO from a fixed one. Dynamic LVOTOs show a characteristic dagger-shaped flow profile on CWD with velocity peaking in late systole. This occurs because of bending of mitral leaflet tips into the LVOT. Timing the CWD flow profile with the electrocardiogram is useful in differentiating a mitral regurgitation jet that may mimic an LVOT gradient in the deep transgastric view. The mitral regurgitation jet starts early (during isovolumetric contraction) because the LV pressure exceeds the left atrial pressure almost as soon as LV contraction begins. LVOT flow profile starts later because flow begins when LV pressure exceeds aortic diastolic pressure.

Both native leaflet and chordal structure preservation during MVR help in long-term preservation of LV function.3 However, complete AML preservation risks causing prosthetic malfunction or sometimes LVOTO, even late after surgery.4 In the case presented, the anterior leaflet was pursed with a suture onto the underside of the annulus. The prosthesis was secured on top of the annulus with a different suture, taking into consideration the infective etiology of leaflets at first surgery. It is possible that the suture which held the leaflet cut through and the AML unfurled, but the valve remained well seated. LVOTO probably occurred because of drag on the unfurled AML in the LVOT during systole as a result of the venture effect. Also, in systole the bioprosthetic valve strut restricted the movement of the AML towards the mitral annulus.

TEE is most suited to assess mitral valve pathology, as the mitral valve is a posteriorly placed structure. TEE visualization of the chordal connection of AML to papillary muscles changed the surgical plan in the case discussed. Detailed TEE evaluation before MVR is important to predict future LVOTO. A small LV cavity, redundant mitral valve leaflets, anteriorly placed chordal apparatus, and a thickened septum are all predictors of postoperative LVOTO after MVR with anterior leaflet preservation. In these circumstances modifying the leaflet preservation technique, avoiding insertion of a high profile bioprosthetic valve and proper valve orientation can significantly reduce the risk.

Footnotes

Accepted for publication August 30, 2007.

REFERENCES

1. Guler N, Ozkara C, Akyol A. Left ventricular outflow tract obstruction after bioprosthetic mitral valve replacement. Texas Heart Inst J 2006;33:399–401[Web of Science][Medline]
2. Esper E, Ferdinand FD, Aronson S, Karp RB. Prosthetic mitral valve replacement: late complications after native valve preservation. Ann Thorac Surg 1997;63:541–3[Abstract/Free Full Text]
3. Yun KL, Sintek CF, Miller DC, Pfeffer TA, Kochamba GS, Khonsari S, Zile MR. Randomized trial comparing partial versus complete chordal-sparing mitral valve replacement: effects on left ventricular volume and function. J Thorac Cardiovasc Surg 2002;123:707–14[Abstract/Free Full Text]
4. Okamoto K, Kiso I, Inoue Y, Matayoshi H, Takahashi R, Umezu Y. Left ventricular outflow obstruction after mitral valve replacement preserving native anterior leaflet. Ann Thorac Surg 2006;82:735–7[Abstract/Free Full Text]

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This Article Full Text (PDF) CME: Take the course for this article: Echocardiography Rounds Echo Loops Alert me when this article is cited Alert me if a correction is posted Services Email this article to a colleague Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Tewari, P. Articles by Basu, R. Search for Related Content PubMed PubMed Citation Articles by Tewari, P. Articles by Basu, R. Related Collections Cardiovascular Heart Monitoring (Cardiac) Echo Rounds Video Clip