18

Intraoperative and Interventional Echocardiography

Step-By-Step Approach

1. ▪ Transesophageal echocardiography (TEE) is increasingly used to guide surgical and transcatheter cardiac procedures (Table 18.1).
   
2. ▪ TEE performance and interpretation occur simultaneously, with immediate communication of results to the physician performing the surgical or percutaneous procedure.
   
3. ▪ More detailed information on intraoperative TEE is provided in Intraoperative and Interventional Echocardiography: Atlas of Transesophageal Imaging, 2nd edition, by Don Oxorn and Catherine Otto (Elsevier, 2018).

Key Points

• □ Time constraints may require a focused examination.
  
• □ Altered loading conditions may affect evaluation of valve and ventricular function.
  
• □ Loading conditions should be matched on baseline and postintervention studies.
  
• □ Urgent decision making based on TEE findings may be necessary.
  
• □ Limitations of the TEE data must be promptly recognized and communicated.
  
• □ Appropriate training and experience are needed for procedural TEE; at many institutions, these TEE studies are performed and interpreted by qualified cardiac anesthesiologists.

Step 1: Preoperative Data Review

1. ▪ For elective procedures, a complete diagnostic evaluation is performed before the planned intervention to ensure evaluation under normal loading conditions and to allow time for discussion and procedural planning.
   
2. ▪ All preprocedure images and diagnostic data should be reviewed, including coronary angiography, hemodynamics, cardiac magnetic resonance (CMR) imaging and computed tomography imaging, as well as echocardiographic data.

Key Points

• □ Intraoperative TEE provides:
  
• 
  
  
  
  • □ Confirmation of the diagnosis
    
  • □ Additional information for procedure planning
    
  • □ A baseline study for comparison to postprocedure imaging
    
  • □ Monitoring of left ventricular (LV) function
    
  • □ Guidance for optimization of catheter and device placement
  
  
• □ Unexpected findings on the baseline procedural TEE may require a change in the planned intervention, consultation with the referring cardiologist, or rescheduling of the procedure.
  
• □ In emergency situations, the baseline procedural TEE may be the primary diagnostic test; in this setting, a complete study should be performed when allowed by time constraints.

Step 2: Hemodynamic Changes and Surgical Instrumentation

1. ▪ Hemodynamic effects of sedation or anesthesia must be considered in the interpretation of procedural TEE imaging and Doppler data.
   
2. ▪ Baseline and postprocedure data should be recorded at similar loading conditions, using volume infusion and pharmacologic agents, if needed, to match hemodynamic parameters.

TABLE 18.1

Indications for Intraoperative or Intraprocedural TEE

Clinical Setting	Procedure	Timing and Goals
Monitoring ventricular function	Before and after cardiopulmonary bypass in high-risk patients	LV volume status, global and regional function
	During noncardiac surgery in high-risk patients	LV volume status, global and regional function
Cardiac surgical procedures	Mitral valve repair	Mechanism and severity of regurgitation Functional assessment and complications after mitral valve repair
	Prosthetic valve replacement	Evaluation after valve implantation
		Detection of complications
	Complex surgical valve procedures	Aortic valve resuspension and aortic root repair
		Coronary artery reimplantation
	Endocarditis	Valve involvement and dysfunction
		Assessment after repair or valve replacement
	Hypertrophic cardiomyopathy	LV outflow anatomy before and after myectomy Evidence of subaortic obstruction
	Aortic dissection repair	Dissection flap location and flow Residual dissection after repair
	Congenital heart disease	Complex anatomy and function before and after surgical repair
Transcatheter interventions	Transcatheter aortic valve implantation (TAVI)	Aortic valve anatomy and function before and after valve implantation
	Transcatheter mitral valve procedures (balloon valvotomy, mitral clip placement, transcatheter mitral valve implantation)	Mitral valve function before and after procedure
	Prosthetic valve dysfunction	Guide and monitor transcatheter closure of paravalvular regurgitation Guide valve-in-valve implantation
	Atrial septal defect or patent foramen ovale closure	Baseline size and anatomy of defect Residual shunt post-procedure Assess for complications
	Septal ablation for hypertrophic cardiomyopathy	Baseline and post-procedure LV outflow obstruction Determine optimal site for ablation
Placement of intracardiac devices	Cannula placement	Guide positioning during placement
	Ventricular assist devices
	Aortic cannulation (avoid atheroma)
General surgical complications	Loculated pericardial effusion after surgical or transcatheter procedures	Detection, size, and hemodynamic consequences
	Intracardiac air after surgical procedures	Recognition and treatment

From Otto CM: Textbook of clinical echocardiography, ed 6, Philadelphia, 2018, Elsevier, p. 509.

Key Points

• □ Assessment of hemodynamics and ventricular function is affected by:
  
• 
  
  
  
  • □ Positive pressure mechanical ventilation
    
  • □ Volume status
    
  • □ Myocardial “stunning” (when aortic cross-clamping is necessary)
    
  • □ Effects of cardiopulmonary bypass
    
  • □ Pharmacologic therapy
  
  
• □ Basic hemodynamic parameters (heart rate and blood pressure) should be indicated on the recorded echocardiographic images to ensure matched loading conditions.
  
• □ When possible, cardiac output, filling pressures, and systemic vascular resistance should also be recorded with the TEE images.
  
• □ With cardiac surgery, TEE images will be affected by:
  
• 
  
  
  
  • □ Inversion of the left atrium (LA) appendage (looks like an LA mass) during mitral valve surgery
    
  • □ Reverberations and shadowing by intracardiac cannulas
    
  • □ Electronic interference (Fig. 18.1)
    
  • □ Intracardiac air (Fig. 18.2)

Step 3: Baseline Data Acquisition

1. ▪ A complete systemic TEE (see Chapter 3) is recommended when possible, but time constraints may require a limited study focused on the key diagnostic information.
   
2. ▪ Optimal diagnosis is ensured by use of a protocol with a consistent image sequence, and acquisition of images is obtained in standard TEE views.
   
3. ▪ Images may be acquired either by:
   
4. 
   
   
   
   • ○ Obtaining all views from each transducer position (high esophageal, midesophageal, transgastric), first with imaging and then with Doppler, or
     
   • ○ Evaluation of each anatomic structure by both imaging and Doppler in at least two orthogonal views—all four cardiac chambers, all four valves, both great arteries, systemic and pulmonary venous return, atrial appendage, and interatrial septum.

Key Points

• □ As with any echocardiographic study, intraoperative and intraprocedural TEE images should be obtained in standard long-axis, short-axis, 2-chamber, and 4-chamber image planes (Fig. 18.3).
  
• □ Three-dimensional (3D) imaging is helpful for evaluation of mitral valve and atrial septal defect anatomy. 3D echocardiographic guidance is essential for some transcatheter procedures.
  
• 
  

  

  
  
• □ Color Doppler is helpful for evaluation of intracardiac flow patterns, particularly for evaluation of mitral regurgitation. 3D color imaging is useful in selected cases (Fig. 18.4).
  
• □ Pulsed Doppler is useful for evaluation of antegrade pulmonary venous and transmitral flow patterns (Fig. 18.5). The pulsed Doppler signal also may help in identification of anatomic structures when otherwise unclear.
  
• □ Continuous-wave (CW) Doppler is helpful in selected cases, but the possibility of a nonparallel intercept angle (and underestimation of velocity) must be considered due to the constraints on transducer positioning in the esophagus.
  
• □ Interference and technical artifacts that limit image quality may be reduced by repositioning the transducer or pausing electronic devices while images are obtained.
  
• □ Standard instrument presets, including transducer frequency, depth, gain, preprocessing and postprocessing, and sector scan width, may be adequate for some images, but adjustment often is needed during the examination.
  
• □ If the electrocardiogram signal is inadequate or subject to interference, cine loops can be acquired using a set time interval instead of one- or two-beat clips triggered by the electrocardiogram QRS complex.
  
• 
  
• 
  

  

  
  
• 
  

  

  
  
• 
  

  

  
  
• □ The structure of interest should be centered with depth and zoom adjusted to optimize the image.

Step 4: Postprocedure Data Acquisition

1. ▪ After the procedure, TEE is repeated to assess the results of the intervention and to evaluate for potential complications.
   
2. ▪ When possible, loading conditions on the postoperative TEE should be similar to the baseline study.

Key Points

• □ The postprocedure TEE focuses on the views and Doppler flows needed to evaluate the effect of the procedure; obtaining data in similar views as the baseline study allows direct comparison of the images.
  
• □ With surgical procedures, the postprocedure TEE is performed after weaning from cardiopulmonary bypass and after restoration of hemodynamics similar to the baseline study.
  
• □ With percutaneous interventions, TEE data may be used continuously to guide the procedure with repeat evaluations at each stage of the intervention.
  
• □ Instrument settings should be the same as on the baseline study to avoid differences due to technical factors, rather than to the procedure itself.

Step 5: Interpret and Communicate Findings

1. ▪ Unlike a conventional diagnostic TEE, intraoperative and procedural TEE studies are interpreted and reported verbally simultaneously with image acquisition.
   
2. ▪ In addition to the results themselves, the degree of certainty of each finding should be reported.

Key Points

• □ TEE findings may prompt a change in surgical plans or additional procedures.
  
• □ If the findings are equivocal or images are low quality, this information should be communicated to avoid decision making based on inadequate data.
  
• □ Qualitative data often are adequate for decision making; when quantitative approaches are used, measurements and calculations that can be performed rapidly are preferred.
  
• □ TEE findings should be documented in the permanent medical record, as well as providing immediate results during the procedure.
  
• □ Intraoperative and intraprocedural TEE images should be saved, as for any echocardiographic study, to allow comparison with future studies.

Intraoperative TEE

Monitoring Left Ventricular Function

1. ▪ Intraoperative TEE is useful for continuously monitoring LV function in high-risk patients undergoing noncardiac surgery and for evaluation of LV function after cardiac surgical procedures (see Table 18.1).
   
2. ▪ Images of the LV allow monitoring of:
   
3. 
   
   
   
   • ○ Ventricular preload (LV volume)
     
   • ○ Global LV systolic function
     
   • ○ Regional LV function
     
   • ○ Right ventricle (RV) size and systolic function

Key Points

• □ In general, the size of the LV chamber reflects filling volume; monitoring allows optimization of preload.
  
• □ Small LV volumes with adequate filling pressures are seen with restrictive cardiomyopathy, pericardial constraint, severe RV dysfunction, or high contractility states.
  
• □ The transgastric short-axis view is often used for continuous monitoring of LV size and global and regional function because it includes myocardial segments supplied by the three major coronary arteries (Figs. 18.6 and 18.7).
  
• □ Standard two-dimensional (2D) TEE images of the LV apex are usually suboptimal, because the LV is typically foreshortened due to the constraints of transducer positioning in the esophagus.
  
• 
  

  

  
  
• 
  
• 
  

  

  
  
• □ 3D LV volumes are recommended for quantitation of LV volumes and ejection fraction.
  
• □ Changes in wall motion usually reflect ischemia; other causes include conduction defects, hypovolemia, and myocardial stunning after cardiopulmonary bypass.
  
• □ RV dysfunction may be due to ischemia, inadequate cardioplegia, or air embolism into the right coronary artery when separating from cardiopulmonary bypass.

Mitral Valve Repair

1. ▪ Baseline 2D and 3D TEE allows precise delineation of mitral valve anatomy and the mechanism of regurgitation, which is helpful in planning the surgical repair.
   
2. ▪ Postrepair TEE allows evaluation of any residual mitral regurgitation and detection of complications.

Key Points

• □ Mitral valve anatomy is best evaluated using 2D rotational scanning and 3D full volume imaging from a midesophageal position (Fig. 18.8).
  
• 
  
  
  
  • □ The central scallops of the anterior (A) and posterior (P) leaflets are seen in the 4-chamber and long-axis views.
    
  • □ The lateral (P1) and medial (P2) scallops of the posterior leaflets are seen in the bicommissural view at 60° to 90° rotation.
    
  • 
    

    

    
    
  • □ Starting in the 4-chamber plane, the lateral scallops of the anterior (A1) and posterior (P1) leaflets can be seen by slightly withdrawing the probe, or tilting superiorly; medial segments (A3 and P3) are seen by advancing the probe or tilting posteriorly.
    
  • □ From the 2-chamber plane, all three scallops of the anterior leaflet are seen when the probe is turned toward the patient’s right and all three scallops of the posterior leaflet are seen when the probe is turned leftward.
    
  • □ A transgastric short-axis view of the mitral valve, when possible, shows both leaflets.
  
  
• □ 3D images of the mitral valve are recommended in all patients with mitral valve disease. A view showing the LA side of the valve facilitates identification of prolapsing segments and flail chords.
  
• □ The direction of the mitral regurgitant jet is helpful in defining the mechanism of regurgitation. Severity of regurgitation is evaluated by (Fig. 18.9):
  
• 
  
  
  
  • □ Vena contracta width (2D) or area (3D)
    
  • □ CW Doppler signal intensity of regurgitant compared to antegrade flow
    
  • □ Pulmonary vein systolic flow reversal (Fig. 18.10)
    
  • □ Proximal isovelocity surface area calculation of regurgitant orifice area
  
  
• 
  
• 
  
• 
  

  

  
  
• □ Postrepair, anatomic, and functional results are evaluated using the same imaging views and Doppler measures as on the baseline study (Fig. 18.11).
  
• 
  
  
  
  • □ Loading conditions (especially blood pressure) should be similar to the baseline study.
    
  • □ Use of the same imaging planes facilitates comparison of pre- and postprocedure data.
    
  • □ Doppler data are recorded with the same instrument settings to ensure detection of any residual regurgitation.
  
  
• □ The postprocedure TEE includes evaluation for the complications of mitral valve repair:
  
• 
  
  
  
  • □ Persistent mitral regurgitation
    
  • □ Systolic anterior motion of the mitral leaflet
    
  • □ Functional mitral stenosis
    
  • □ Ventricular systolic dysfunction

Aortic or Mitral Valve Replacement

1. ▪ In patients undergoing aortic or mitral valve replacement, anatomic and functional assessment should be completed before the patient is in the operating room.
   
2. ▪ Evaluation of the severity of valve stenosis by TEE is problematic for several reasons, so intraoperative TEE decisions regarding stenosis severity should be avoided (Fig. 18.12).
   
3. ▪ The postprocedure TEE allows detection of prosthetic valve dysfunction and assessment of LV systolic function.
   
4. 
   
5. 
   

   

   
   
6. ▪ Knowledge of the structure and function of each prosthetic valve type is needed for correct interpretation of postprocedure data.

Key Points

• □ A parallel alignment between the ultrasound beam and aortic velocity is rarely possible on TEE, resulting in underestimation of stenosis severity.
  
• □ Direct imaging and planimetry of aortic valve area is limited by reverberations and shadowing due to valve calcification but may be possible with 3D imaging when calcification is not severe.
  
• □ Mitral stenosis can be evaluated using the Doppler pressure half-time method, because the TEE probe position allows a parallel alignment with antegrade transmitral flow.
  
• □ A small amount of valve regurgitation is seen with a normally functioning prosthetic valve.
  
• □ Central regurgitation is common with a bioprosthetic valve; eccentric jets, with a variable pattern of regurgitation depending on valve type, are typical with mechanical valves.
  
• □ A small amount of paravalvular regurgitation may be seen, but a large paravalvular leak may require immediate correction.
  
• □ Rarely, retained mitral leaflet tissue impairs normal motion of a mechanical mitral occluder.
  
• □ Recording images of leaflet/occluder motion and transvalvular Doppler flows in the operating room provides a useful comparison for subsequent studies.

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1. Specialized Echocardiography Applications
2. Endocarditis
3. Pericardial Disease
4. Valvular Regurgitation

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