Mitral Valve Area Using 3-dimensional Transesophageal Echocardiography
Mitral Valve Area Using 3-dimensional Transesophageal Echocardiography
Even during mitral valve repair procedure (MVP) for severe mitral stenosis (MS), the
 intraoperative assessment of mitral valve area (MVA) is necessary for evaluating the severity
 of MS before the repair and excluding residual MS for immediate determination of the success
 of the repair procedure and postoperative prognosis. For this purpose, several methods have
 been applied by introperative transesophageal echocardiography (TEE): pressure half-time
 (PHT) of mitral inflow Doppler and 2-dimensional (2D) planimetry methods have been widely
 used in clinical practice. However, especially after MVP, the PHT method is usually
 unreliable because it usually underestimates the MVA due to various intraoperative
 hemodynamic factors.

 The authors hypothesized that the MVA determined by 3D TEE would be more accurate than that
 by PHT during immediate post-MVP procedure in severe MS patients and comparable to
 postoperative MVA determined by MDCT. Therefore, the present study determined the MVA by
 using PHT, 3D planimetry and MDCT before and after the MVP procedure in severe MS patients
 and analyzed them to evaluate 3D TEE's utility for evaluation of MVA.
After obtaining permission of the Institutional Review Board of Konkuk University Medical
 Center, Seoul, South Korea , patients scheduled to undergo elective MVP due to more than
 moderate MS and left atrial enlargement with or without atrial fibrillation (AFib) signed
 written informed consent agreements and prospectively participate in the present study.

 In addition to the routine transthoracic echocardiographic evaluation, cardiac CT examination
 is performed in all recruited patients prior to surgery to determine MVA.

 Induction of anesthesia and tracheal intubation are performed after the administration of
 intravenous etomidate 0.1-0.2 mg/kg and rocuronium 0.9 mg/kg followed by continuous infusion
 of remifentanil (0.5-1.0 mcg/kg/min). After tracheal intubation, sevoflurane (1.0 inspired
 vol%) and infusion of rocuronium (0.2 mg/kg/hr) are administered for anesthesia maintenance.

 After anesthesia induction, pulmonary artery catheter (PAC) is placed in right internal
 jugular vein into pulmonary artery by pressure guidance and a 3D TEE probe (X-9™, Philips
 Medical Systems Andover, MA, USA) is inserted for the comprehensive intraoperative TEE
 examination using a 3D echocardiographic imaging platform (iE33; Philips Medical Systems,
 Andover, MA, USA). While momentarily turning off the ventilator, three consecutive
 velocity-time integrals (VTIs) of mitral inflow Doppler scans were obtained by applying the
 continuous wave Doppler parallel to the mitral inflow Color Doppler signal in the
 midesophageal long-axis view. In case of AFib, the biggest VTI among the 5 consecutive VTIs
 of the mitral inflow Doppler was used for determining PHT to detect maximal mitral inflow
 among irregular heartbeats. Immediately after recording the VTIs, a live 3D zoom "en face" MV
 view from the left atrium (LA) or left ventricle (LV) perspective is acquired.

 As baseline data, MVA is determined by using PHT method (MVA-PHT): PHT of the mitral inflow
 deceleration slope is determined using stored mitral inflow Doppler VTI and the MVA are
 automatically calculated assuming MVA = 220/PHT. At the same time, a 2D image of the smallest
 MVA perpendicular to the mitral inflow at the maximal MV opening was achieved by
 post-processing including aligning and cropping of the acquired 3D images with an installed
 software (3DQ™ in Q-lab™, Philips, USA). MVA was determined by circumferential tracing of the
 leaflet edges of the MV opening in the cropped and reconstructed tomographic image from
 stored 3D volume image (MVA-3D) (Fig. 1). All MVA measurements were repeated 3 times within a
 minimal time interval by the same expert cardiac anesthesiologists with the mean value used
 for analysis.

 All patients got a single type of MVP (Comprehensive Mitral Valve Apparatus Reconstruction™)
 consisting of following procedures under moderate hypothermic cardiopulmonary bypass (CPB) by
 one cardiac surgeon: restoration of a sufficient MV opening with repair of anterior or
 posterior MV leaflets, mitral commissure, and chordate; and lifting posterior annuloplasty
 using a flexible ready to use band. A Maze operation is additionally performed in patients
 who associated with Afib.

 Immediately after the weaning from the CPB and achieving stable hemodynamics (mean arterial
 blood pressure > 65 mmHg, heart rate 60-90 beats per minute, cardiac index > 2.0 L/min/m2),
 MVA-PHT and MVA-3D are determined in the same manner as the baseline data acquisition.

 The following intraoperative exclusion criteria are applied: 1) intraoperative conversion to
 MV replacement due to insufficient repair procedure, 2) the inability to delineate MV opening
 due to insufficient 3D imaging.

 Within 7 postoperative days, the MVA-CT is determined again for comparison to other methods
 by an expert cardiac radiologist in the same manner which applied preoperatively.

 Statistical analyses are conducted using SPSS 18.0 (SPSS Inc., Chicago, IL, USA). To assess
 intra-observer variability, the MVAs measured by PHT method and 3D planimetry with TEE are
 analyzed using intraclass correlation coefficient (ICC). The comparisons of MVA-PHT, MVA-3D,
 and MVA-CT before or after MVP are analysed used a One Way Repeated Measures Analysis of
 Variance and their pairwise multiple comparisons are performed via the Tukey method. The
 comparisons of the other continuous variables of echocardiographic findings are performed by
 paired t or Wilcoxon Signed Rank tests. The linear regression analysis is used to determine
 possible correlation between MVA by using each method. Data are expressed as mean ± SD (95%
 confidence interval. CI) or median (25%-75%), and number of the patients. A p value less than
 0.05 is considered statistically significant.
Inclusion Criteria:

 -  patients scheduled to undergo elective mitral valve repair surgery

 -  more than moderate mitral stenosis

 -  left atrial enlargement

 -  signed written informed consent agreements

 Exclusion Criteria:

 -  urgent or emergency case

 -  other concurrent valvular surgery

 -  patient age < 18 years,

 -  reduced left or right ventricular function (ejection fraction < 40%),

 -  mitral regurgitation grade more than moderate

 -  repeated surgery for cardiac valvular disease