Transthoracic and Transesophageal Echocardiography in the Catheterization Laboratory

4 Transthoracic and Transesophageal Echocardiography in the Catheterization Laboratory

Rebecca Hahn, Linda D. Gillam

Alcohol Septal Ablation

Background

• In the setting of hypertrophic obstructive cardiomyopathy (HOCM), transcoronary alcohol septal ablation by injection of ethanol into the septal perforator supplying the muscle mass adjacent to the point of mitral leaflet-septal contact widens the outflow tract and relieves the obstruction.
• Echocardiography has become an essential tool, contributing to procedural success and reduction in complications.

Preprocedural Anatomic and Physiologic Imaging

• Confirm left ventricular (LV) anatomy and function:
• Perform routine transthoracic imaging to exclude atypical forms of hypertrophic cardiomyopathy as well as fixed left ventricular outflow tract (LVOT) obstruction.
• Patients with apical or mid-cavity hypertrophy with intracavitary (not subaortic) gradients are not candidates for alcohol septal ablation (ASA).
• Measure the septal thickness at the site of obstruction from parasternal and apical views (Fig. 4-1).
• Avoid measuring right ventricular (RV) trabeculations and papillary muscle tissue, which may merge with the RV side of the septum.
• Confirm mitral valve (MV) anatomy and function:
• Document systolic anterior motion (SAM) of the mitral leaflet with proximal MV-septal contact (Fig. 4-2).
• Document the direction and severity of mitral regurgitation (MR).
• Typical MR jet secondary to SAM is directed laterally and posteriorly (Fig. 4-3).
• Severity of MR is usually proportional to the severity of septal contact during SAM and thus to the severity of the LVOT obstruction.
• If atypical MR is seen, intrinsic valvular disease may be present.
• Determine the subaortic gradient:
• Appropriate patients for ASA should have a gradient of 50 mm Hg or more measured with Doppler echocardiography either at rest and/or with physiologic provocative maneuvers and/or during exercise.
• Avoid using dobutamine as a stressor since it can provoke significant subaortic gradients in normal hearts and may result in catastrophic adverse consequences in patients with significant obstructive disease.
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Figure 4-1 Septal thickness at the site of obstruction should be measured from parasternal (A) and apical (B) views (arrows).

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Figure 4-2 Document systolic anterior motion (SAM) of the mitral leaflet with proximal mitral valve (MV)-septal contact (arrows) from parasternal (A) and apical (B) views.

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Figure 4-3 Typical mitral regurgitation (MR) jet secondary to SAM is directed posteriorly (A, parasternal view) and laterally (B, apical view).

Pitfalls

• RV trabeculations merging with the septum should not be included in measurements of the interventricular septum. Low parasternal views are particularly prone to this type of error. If in doubt, angulation of the imaging plane will help demonstrate the plane separating such trabeculations from the septum.
• When endocardial borders are not well imaged, consider using intravenous contrast agents for LV opacification to confirm ventricular anatomy. The apex may be particularly difficult to image.
• Discrete subaortic stenosis and valvular aortic stenosis must be excluded.
• Congenital abnormalities of the mitral apparatus (anomalous papillary muscle insertion or malpositioned enlarged papillary muscles) produce more distal muscular obstruction in the mid-cavity. These lesions are not candidates for ablation.
• Avoid contamination of the subaortic spectral Doppler with MR.
• MR peak velocities are always higher than LVOT velocities.
• Both MR and LVOT velocities may appear to peak late given the anatomy; however, the duration of MR is typically greater than the duration of systolic ejection (Fig. 4-4).
• Use color Doppler to determine the direction of flow: MR and LVOT flows are typically in opposite directions unless intrinsic MV disease is present.
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Figure 4-4 Both MR and left ventricular outflow tract (LVOT) velocities may appear to peak late given the close relationship between abnormal MV motion and outflow obstruction; however, the duration of MR (A) is typically longer and the velocity higher than transaortic (B) flow.

Intraprocedural Anatomic and Physiologic Imaging

• Identification of the appropriate septal perforator:
• Balloon occlusion followed by myocardial contrast injection directly into the septal perforator by the angiographer should be performed during continuous transthoracic echocardiographic (TTE) or transesophageal echocardiographic (TEE) imaging.
• Apical four- or five-chamber views are easiest to obtain during the procedure.
• The resulting hyperechoic region of the myocardium is identified (Fig. 4-5).
• Continuous wave (CW) Doppler is performed (again from the apical views).
• An immediate fall in outflow gradient following balloon occlusion and/or contrast injection should be seen and aids in the decision to proceed with alcohol injection.
• If no change in gradient is seen and/or the hyperechoic region of the septum does not correlate with the region of subvalvular obstruction, another target septal perforator should be chosen.
• Injection of alcohol with limited myocardial infarction:
• Apical four- or five-chamber views are continuously imaged during and following injection of alcohol.
• The area of infarction is identified by myocardial thinning and hypokinesis (Fig. 4-6).
• CW Doppler is performed and an immediate fall in outflow gradient following septal ablation is frequently seen.
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Figure 4-5 Following direct intracoronary contrast injection, the resulting hyperechoic region of the myocardium is identified.

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Figure 4-6 Following injection of alcohol, the area of infarction is identified by myocardial thinning (A) and hypokinesis with an immediate reduction in transaortic gradient (B).

Pitfalls

• The selected septal perforator must perfuse the region of the septum in contact with the MV during SAM but should not perfuse other distant regions of the LV or RV myocardium or papillary muscles.
• Approximately 15% to 20% of patients will not have a successful procedure due to lack of suitable septal arteries in the region of obstruction.
• If a larger than expected region of anteroseptal hypokinesis is seen, the possibility of backward extravasation of alcohol producing occlusion or abrupt coronary no-flow should be considered.

Postprocedural Imaging

• Confirm LV anatomy and function:
• Image basal septum from parasternal and apical views concentrating on septal anatomy following controlled infarction.
• Measure the septal thickness in the region of infarction and, if different, in the region of mitral-to-septal contact.
• Color Doppler imaging to exclude perforation (ventricular septal defect) should include the RV side of the septum.
• Color Doppler imaging of the LVOT should show reduced turbulence.
• Confirm MV anatomy and function:
• Document absence of SAM of the mitral leaflet.
• Color Doppler to assess the severity of residual MR.
• Determine the subaortic gradient:
• Following successful ASA, peak gradients should be <50 mm Hg.
• Acute reduction in transaortic gradient in the catheterization laboratory may be followed by an increase in gradient within 24 hr, but typically is followed by significant reduction in the gradient over the ensuing 6 to 12 months due to further remodeling and thinning of the affected septum.

Key Points

• Confirm LV anatomy (increased basal septal wall thickness) and MV anatomy (SAM) with documentation of a resting or provoked gradient of >50 mm Hg arising from septal-MV contact.
• Identify appropriate septal perforator supplying the region of septal-MV contact using direct injection of myocardial contrast and imaging the hyperechoic region of the septum.
• Image the area of infarction and document myocardial thinning and hypokinesis, as well as residual outflow gradient.

Percutaneous Balloon Mitral Valvuloplasty

Background

• Since the advent of percutaneous balloon mitral valvuloplasty (PBMV) in 1984, the technique has become the treatment of choice for mitral stenosis (MS); it is as effective as open valvotomy and more effective than closed valvotomy. Echocardiographic assessment is essential in patient selection, intraprocedural monitoring, and postprocedural follow-up.
• Echocardiographic characterization and quantitation of MV structure and function are key determinants of patient suitability for PBMV.

Preprocedural Imaging

• Assess severity and level of MV obstruction.
• Both the pre-PBMV area and severity of MR are independent predictors of immediate post-PBMV success and should be assessed.
• Planimeter MV area from parasternal short axis views.
• Color Doppler MV to assess MR.
• CW Doppler across MV to record peak and mean gradients and pressure halftime.
• Record heart rate.
• Apply the Wilkins Echo Score to predict outcome of valvuloplasty (Table 4-1).
• In Wilkins’ original report,1 patients with a score of less than or equal to 8 were more likely to have optimal results following valvuloplasty (post mitral valve area [MVA] >1.5 cm2, left atrial pressure [LAP] <18 mm Hg). Patients with a score of greater than 8 had suboptimal outcomes, and a score of greater than 10 increased the chance of suboptimal results with complications.
• Apply MR score (Table 4-2) to predict development of significant MR.
• Assess presence of intracardiac thrombus.
• Preprocedure TEE is performed to exclude left atrial thrombus (Fig. 4-7).
• If a thrombus is found, PBMV is relatively contraindicated. The patient can be anticoagulated or surgical intervention considered.
• Confirmation of MV anatomy is also performed; three-dimensional (3D) TEE may be useful for optimizing planimetry of the valve orifice (Fig. 4-8).

TABLE 4-1 THE MV SCORE HELPS PREDICT PERCUTANEOUS BALLOON MITRAL VALVULOPLASTY SUCCESS BY GRADING FOUR CHARACTERISTICS OF THE MV APPARATUS

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TABLE 4-2 FURTHER SCORING OF THE MV HELPS PREDICT THE OCCURRENCE OF THE PRIMARY COMPLICATION OF PBMV, MITRAL REGURGITATION

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Figure 4-7 Preprocedural transesophageal echocardiography (TEE) must be performed to exclude left atrial thrombus (arrows).

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Figure 4-8 Three-dimensional (3D) TEE imaging may be utilized to assess the MV area.

Pitfalls

• Pressure half-time calculation of valve area has numerous limitations and should be used with caution in older patients, in atrial fibrillation, and in patients with prior MV interventions. An integrative approach to calculating valve area is always recommended.
• Peak and mean gradients are closely related to the amount of diastolic flow across the valve and the diastolic filling period and should be interpreted in relation to heart rate.
• Patients with degenerative MS (calcification of the annulus or body of the leaflets with little or no commissural fusion) should not undergo PBMV.
• Scores greater than 8 are not absolute contraindications to attempted PBMV.

Intraprocedural Imaging

• Transseptal puncture: although typically interventionalists can perform the transseptal puncture under fluoroscopy, occasionally TEE can help interventionalists position the puncture to avoid puncture of the aorta or atrial wall.
• Assessing postvalvuloplasty results by TTE:
• After each balloon inflation, imaging should be performed to assess MR severity, peak and mean transmitral gradients, and MV area by planimetry.
• A suboptimal valvuloplasty result is defined as a final valve area of less than 1.0 cm2, a final transmitral mean pressure gradient greater than 10 mm Hg, or a less than 25% increase in valve area.
• Creation of more than mild MR is a relative contraindication to further balloon inflations.
• In some cases, intracardiac echocardiography or TEE imaging (see Fig. 4-8) may be utilized to assess MV area.
• Assess for complications of the procedure:
• Hemopericardium (0.5–12%), embolism (0.5–5%), severe MR (2–10%, although 25% of patients increase severity by one grade) most often due to non-commissural tear, any of which might create a need for urgent surgery (<1%) (Fig. 4-9).
• Transient atrial septal defects are common after transseptal access, but substantial shunting occurs in less than 5% of patients.
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Figure 4-9 This biplane image following percutaneous balloon mitral valvuloplasty shows a noncommissural tear (right panel, arrow), which is the most common etiology of significant MR. In the left panel the arrows point to the intraventricular catheter.

Pitfalls

• Pressure half-time calculation cannot be used immediately post-PBMV to assess area due to acute changes in compliance of the left atrium.

Key Points

• Apply various echocardiography scores to predict procedural success and anticipate procedural complications.
• Assess peak/mean gradient and presence/severity of MR following each balloon inflation and planimeter the final valve area.
• Assess for complications.

Percutaneous Valves: Transcatheter Aortic Valve Implantation

Background

• Transcatheter aortic valve implantation (TAVI) has been shown to be superior to medical therapy in a population of patients with severe, symptomatic aortic stenosis at prohibitive risk for surgery.2
• Because echocardiography has largely replaced the invasive assessment of aortic stenosis, it is a necessary tool in the preprocedural, intraprocedural, and postprocedural evaluation of patients undergoing transcatheter valve procedures.
• Because the experience in the United States has to date been limited to the balloon expandable valve, the current review will outline the approach to preprocedural, intraprocedural, and postprocedural echocardiographic assessment of candidates for TAVI with the balloon expandable valve. Both the balloon expandable and a self-expanding valve are commercially available in Europe.

Preimplantation Echocardiographic Imaging for TAVI (Box 4-1)

• Measure the LVOT diameter in systole:
• The LVOT diameter should be measured from parasternal long axis views in systole
• The diameter is measured in parasternal long axis view typically between the annulus and 0.5 cm apical to the aortic annulus in systole. The long axis view is used to measure the diameter of the LVOT since the septum and anterior leaflet of the MV are most parallel in this view; apical views should not be used.
• The largest measured diameter of the LVOT should be used in calculating the aortic valve area.
• In the setting of acoustic shadowing of the distal annulus, a lower or higher window can be used to better image the entire plane of the annulus.
• If the LVOT diameter cannot be accurately measured, the dimensionless index (cut-off of <0.25 for LVOT diameters of 2.4 cm and <0.2 for LVOT diameters of >2.4 cm) can be a more accurate indicator of aortic stenosis severity.
• Measure the aortic annulus diameter in systole:
• The annulus should be measured from the long axis view in systole.
• Measure the hinge point of the cusps.
• Short axis views may be helpful in characterizing the appearance of the valve and aligning the long axis view perpendicular to the largest annular diameter (Fig. 4-10).

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  4. Transthoracic Three-Dimensional Echocardiography

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Jun 4, 2016 | Posted by in CARDIOLOGY | Comments Off on Transthoracic and Transesophageal Echocardiography in the Catheterization Laboratory

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