The use of intracardiac echocardiography and other intracardiac imaging tools to guide noncoronary cardiac interventions

The limitations of standard fluoroscopy have led to the development of improved imaging techniques to guide noncoronary cardiac interventions. Imaging tools that are used in the interventional laboratory can be categorized as invasive and noninvasive. Noninvasive cardiac imaging tools include ultrasound, computed tomography, and magnetic resonance imaging. These modalities can generate high-resolution images of the heart and are increasingly being used to guide cardiac interventions. Despite these advances, there remains a strong role for invasive imaging tools in the interventional laboratories. Such invasive imaging tools include transesophageal echocardiography, intracardiac echocardiography, intracardiac endoscopy, and electroanatomic mapping systems. Despite the risks inherent to the invasive nature of these tools, these modalities can provide excellent real-time, detailed images that can be invaluable in guiding certain cardiac interventions. This review will propose the features of an ideal intracardiac imaging tool, summarize the intracardiac imaging tools that are currently available or under development to guide noncoronary cardiac interventional procedures, and suggest opportunities for improvement. One opportunity in this field is to couple imaging systems directly with the interventional devices themselves. The use of intracardiac imaging to guide select cardiac procedures including transseptal catheterization, catheter ablation procedures for arrhythmias, and percutaneous placement of cardiac valves and closure devices will also be discussed. Most of this review will be devoted to intracardiac echocardiography, which currently has the broadest number of applications.

Real-time 3-dimensional transesophageal echocardiography in the evaluation of post-operative mitral annuloplasty ring and prosthetic valve dehiscence

OBJECTIVES

This study sought to assess the use of real-time (RT) 3-dimensional (3D) transthoracic and transesophageal echocardiography (TEE) in the evaluation of post-operative mitral valve dehiscence.

BACKGROUND

Mitral valve replacement or repair may be complicated by post-operative dehiscence of the valve or annuloplasty ring resulting in clinically significant mitral regurgitation or hemolysis. Diagnosis is generally performed using 2-dimensional transthoracic echocardiography and TEE. Recently, an RT 3D TEE probe has been developed to produce high-quality real-time images.

METHODS

We used RT 3D TEE to evaluate mitral regurgitation after mitral valve repair or replacement as a result of mitral ring dehiscence. We studied the additional information and diagnostic utility provided by RT 3D TEE.

RESULTS

Eighteen patients were studied (8 patients after repair and 10 after replacement). Real-time 3D TEE allowed accurate evaluation of the pathology, including definition of the type of ring or prosthesis used; description of the site, size, shape, and area of the dehisced segment; and clear definition of the origin of the mitral regurgitation.

CONCLUSIONS

In mitral valve dehiscence, RT 3D TEE provides additional information about the exact anatomic characteristics of the dehiscence that can be used to help in planning the most appropriate corrective intervention.

Real-time 3-dimensional echocardiographic quantification of left ventricular volumes: multicenter study for validation with magnetic resonance imaging and investigation of sources of error

OBJECTIVES

We sought to study: 1) the accuracy and reproducibility of real-time 3-dimensional echocardiographic (RT3DE) analysis of left ventricular (LV) volumes in a multicenter setting, 2) interinstitutional differences in relationship with the investigators' specific experience, and 3) potential sources of volume underestimation.

BACKGROUND

Reproducibility and accuracy of RT3DE evaluation of LV volumes has not been validated in multicenter studies, and LV volumes have been reported to be underestimated compared to cardiac magnetic resonance (CMR) standard.

METHODS

A total of 92 patients with a wide range of ejection fractions underwent CMR and RT3DE imaging at 4 different institutions. Images were analyzed to obtain LV end-systolic volume (ESV) and end-diastolic volume (EDV). Reproducibility was assessed using repeated analyses. The investigation of potential sources of error included: phantom imaging, intermodality analysis-related differences, and differences in LV boundary identification, such as inclusion of endocardial trabeculae and mitral valve plane in the LV volume.

RESULTS

The RT3DE-derived LV volumes correlated highly with CMR values (EDV: r = 0.91; ESV: r = 0.93), but were 26% and 29% lower consistently across institutions, with the magnitude of the bias being inversely related to the level of experience. The RT3DE measurements were less reproducible (4% to 13%) than CMR measurements (4% to 7%). Minimal changes in endocardial surface position (1 mm) resulted in significant differences in measured volumes (11%). Exclusion of trabeculae and mitral valve plane from the CMR reference eliminated the intermodality bias.

CONCLUSIONS

The RT3DE-derived LV volumes are underestimated in most patients because RT3DE imaging cannot differentiate between the myocardium and trabeculae. To minimize this difference, tracing the endocardium to include trabeculae in the LV cavity is recommended. With the understanding of these intermodality differences, RT3DE quantification of LV volume is a reliable tool that provides clinically useful information.

Combined assessment of coronary anatomy and myocardial perfusion using multidetector computed tomography for the evaluation of coronary artery disease

Multidetector computed tomography (MDCT) is increasingly used as an alternative to invasive coronary angiography. Although computed tomographic coronary angiography (CTCA) has been validated against invasive coronary angiography and nuclear myocardial perfusion imaging, the potential of MDCT to evaluate perfusion has not been fully explored. We sought to (1) develop a new technique for quantitative assessment of myocardial enhancement based on analysis of MDCT images acquired for CTCA, (2) identify the underlying causes of myocardial hypoenhancement detected by MDCT, and (3) determine the added diagnostic value of the MDCT perfusion index when combined with CTCA. We studied 84 patients undergoing clinical CTCA (64 patients with invasive coronary angiogram and a control group of 20 patients). MDCT perfusion index was calculated from x-ray attenuation measured in 16 myocardial segments. Hypoenhancement was automatically detected using comparisons with the normal range obtained in the control group, and its added value was determined against invasive coronary angiographic findings combined with known previous myocardial infarction. Myocardial hypoenhancement was detected in 29 of 64 patients in 47 vascular territories, of which 36 (77%) were abnormal by the reference technique. Of these 36 abnormalities, 10 (28%) were associated with previous myocardial infarction, whereas 26 (72%) corresponded to significant coronary stenosis. The addition of MDCT perfusion index to CTCA improved its diagnostic accuracy (sensitivity 0.87 to 0.96, accuracy 0.84 to 0.88, despite a decrease in specificity 0.79 to 0.68). In conclusion, myocardial hypoenhancement is a potentially valuable addition to MDCT evaluation of coronary artery disease without additional cost in radiation dose or contrast load.

Quantification of left ventricular volumes using three-dimensional echocardiographic speckle tracking: comparison with MRI

AIMS

Although the utility of two-dimensional (2D) speckle tracking echocardiography (STE) to quantify left ventricular (LV) volume has been demonstrated, this methodology is limited by foreshortened views, geometric modelling, and the assumption that speckles can be tracked from frame to frame, despite their out of plane motion. To circumvent these limitations, a three-dimensional (3D) speckle tracking algorithm was recently developed. Our goal was to evaluate the accuracy of the new 3D-STE side by side with 2D-STE using cardiac magnetic resonance (CMR) as a reference.

METHODS AND RESULTS

Apical two- and four-chamber views (A2C and A4C) and real-time 3D datasets (Toshiba Artida 4D System) obtained in 43 patients with a wide range of LV size and function were analysed to measure LV end-systolic and end-diastolic volumes (ESV and EDV) using 2D and 3D-STE techniques. Short-axis CMR images (Siemens 1.5T scanner) acquired on the same day were analysed to obtain ESV and EDV reference values using the method of disks approximation. Reproducibility of both STE techniques was assessed using repeated measurements. While 2D-STE correlated well with CMR (r: 0.72-0.88), it underestimated LV volumes with relatively large biases (10-30 mL) and wide limits of agreement (SD: 36-51 mL), with A2C-derived measurements being worse than A4C values. The 3D-STE measurements showed higher correlation with CMR (0.87-0.92), and importantly smaller biases (1-16 mL) and narrower limits of agreement (SD: 28-37 mL). In addition, 3D-STE showed lower inter- and intra-observer variability (11-14% and 12-13%), than 2D-STE (16-17% and 12-16%, respectively).

CONCLUSION

This is the first study to validate the new 3D-STE technique for LV volume measurements and demonstrate its superior accuracy and reproducibility over previously used 2D-STE technique.

Automated frame-by-frame endocardial border detection from cardiac magnetic resonance images for quantitative assessment of left ventricular function: validation and clinical feasibility

PURPOSE

To develop a technique based on image noise distribution for automated endocardial border detection from cardiac magnetic resonance (CMR) images throughout the cardiac cycle, validate it, and test its clinical utility.

MATERIALS AND METHODS

Images obtained in 36 patients were analyzed using custom software to obtain left ventricular (LV) volume throughout the cardiac cycle, end-systolic and end-diastolic LV volumes, and ejection fraction (EF). Validation against manually-traced endocardial boundaries included intertechnique comparisons of LV volumes, slice areas, and border positions. Then, the clinical feasibility of the dynamic automated analysis of LV function was tested in 14 patients with normal LV function, 12 patients with systolic dysfunction, and 10 patients with diastolic dysfunction.

RESULTS

Analysis time for one cardiac cycle was <15 minutes. Intertechnique comparisons resulted in high correlation (r>0.96), small biases (volumes: -6 mL; EF: 4.6%) and narrow limits of agreement (volumes: 17.6 mL; EF: 9.2%). We found significant intergroup differences in multiple quantitative indices of systolic and diastolic function.

CONCLUSION

Fast, automated, dynamic detection of LV endocardial boundaries is feasible and allows accurate quantification of LV size and function, which is potentially clinically useful for objective assessment of systolic and diastolic dysfunction.

Value of multidetector computed tomography evaluation of myocardial perfusion in the assessment of ischemic heart disease: comparison with nuclear perfusion imaging

MDCT-derived myocardial perfusion has not yet been validated against accepted standards. We developed a technique for quantification of myocardial perfusion from MDCT images and studied its diagnostic value against SPECT myocardial perfusion imaging (MPI). Ninety-eight patients were studied. Abnormal perfusion was detected by comparing normalized segmental x-ray attenuation against values obtained in 20 control subjects. Disagreement with resting MPI was investigated in relationship to MDCT image quality, severity of MPI abnormalities, and stress MPI findings. Resting MPI detected mild or worse abnormalities in 20/78 patients. MDCT detected abnormalities in 15/20 patients (sensitivity of 0.75). Most abnormalities missed by MDCT analysis were graded as mild on MPI. Additional abnormalities found in 16/78 patients were not confirmed on resting MPI (specificity of 0.72). However, 8 of these 16 apparently false positive MDCT perfusion tests had abnormal stress MPI; of these 8 patients, 7 had optimal MDCT image quality, while in 6/8 remaining patients, image quality was suboptimal. When compared with resting MPI, MDCT detected perfusion abnormalities with high accuracy. Moreover, half of MDCT perfusion abnormalities not confirmed by resting MPI were associated with abnormal stress MPI. Importantly, this information can be obtained without additional radiation dose or contrast agent.

Real-time three-dimensional transesophageal echocardiography of the left atrial appendage: initial experience in the clinical setting

BACKGROUND

The aim of this study was to determine the feasibility and accuracy of a new real-time 3-dimensional (RT3D) matrix-array transesophageal echocardiographic probe for the determination of left atrial appendage (LAA) geometry.

METHODS

Sixty-six consecutive patients (mean age, 53 +/- 17 years) referred for 2-dimensional (2D) transesophageal echocardiography (TEE) underwent additional RT3D TEE. The feasibility of RT3D TEE for LAA geometry was studied in the first 37 patients, and 2D and RT3D transesophageal echocardiographic quantification of the LAA were compared in the subsequent 29 patients. The LAA orifice diameter and depth were measured using biplane 2D TEE, and LAA orifice area was calculated as an ellipse. LAA orifice area and depth were measured in 3D and correlated to 2D measurement and were also correlated to 64-slice cardiac computed tomography (CT) in 8 patients.

RESULTS

All 66 patients underwent RT3D matrix-array TEE without complication. In the feasibility study, the LAA was well visualized in 95%. In the quantitation study, 2D TEE underestimated LAA orifice area compared with 3D imaging (3.1 +/- 1.3 vs 4.2 +/- 2.2 cm(2); r = 0.55). LAA depth by 2D and 3D imaging were well correlated (3.7 +/- 0.7 vs 3.4 +/- 0.7 cm; r = 0.77). LAA orifice area on CT was well correlated with area on 3D TEE (r = 0.98) but not with area 2D TEE (r = 0.13). Bland-Altman analysis demonstrated that 2D TEE systematically underestimated LAA orifice area compared with 3D TEE (mean bias, -1.0 cm(2), with wide limits of agreement [-4.6 to 2.6 cm(2)]). In the 8 patients who underwent both 3D TEE and CT, the mean bias was 0.15 cm(2), with narrow limits of agreement (-0.50 to 0.20 cm(2)).

CONCLUSIONS

RT3D TEE for the visualization and quantitative analysis of LAA orifice area is feasible and correlates well with 64-slice cardiac CT.

Diagnostic value of parametric imaging of left ventricular wall motion from contrast-enhanced echocardiograms in patients with poor acoustic windows

BACKGROUND

Analysis of left ventricular (LV) regional wall motion (RWM) is subjective and may be challenging in patients with suboptimal images, even with contrast enhancement. It was hypothesized that the amplitude and timing of RWM obtained from contrast-enhanced echocardiograms can be accurately represented in still-frame parametric images. This study was designed to (1) test this hypothesis, (2) establish the diagnostic value of these images as an aid for inexperienced readers, and (3) test the feasibility of automated quantitative analysis of RWM.

METHODS

Contrast-enhanced apical 4-chamber, 2-chamber, and 3-chamber LV views were acquired in 45 patients with poor acoustic windows. The interpretation of dynamic images by an experienced reader who classified RWM as normal or abnormal was used as a reference for comparisons against (1) visual interpretation of parametric images, (2) interpretation of dynamic images by two inexperienced readers (American Society of Echocardiography level I) without and subsequently with parametric images, and (3) automated quantification of RWM.

RESULTS

Expert readers detected abnormal RWM in 30 patients (437 of 945 segments). Visual interpretation of parametric images showed good agreement with the reference (sensitivity, 85%; specificity, 82%; accuracy, 84%). The interpretations by inexperienced readers improved with the addition of parametric images, with increases in specificity (from 58% to 79%) and accuracy (from 74% to 84%), despite a slight decrease in sensitivity (from 92% to 91%). Automated classification was feasible and accurate (sensitivity, 82%; specificity, 78%; accuracy, 80%).

CONCLUSION

Parametric images derived from contrast-enhanced echocardiograms of patients with poor acoustic windows accurately depicted RWM, improved the diagnostic accuracy of inexperienced readers, and allowed the objective detection of RWM abnormalities.

Measurement of left ventricular mass by real-time three-dimensional echocardiography: validation against magnetic resonance and comparison with two-dimensional and m-mode measurements

BACKGROUND

The recent development of 3-dimensional (3D) surface detection algorithm of the endocardial and epicardial surfaces from real-time 3D echocardiographic (RT3DE) datasets allows direct semiautomated quantification of left ventricular mass (LVM). Our aims were to (1) evaluate the accuracy of RT3DE measurements of LVM using this algorithm against cardiac magnetic resonance (CMR) reference and (2) compare RT3DE LVM with conventional M-mode, 2-dimensional (2D), and RT3DE-guided biplane measurements.

METHODS

A total of 205 patients were studied in 2 protocols: (1) RT3DE and CMR imaging was performed on the same day in 55 subjects; (2) in an additional 150 subjects, RT3DE, 2D, and M-mode images were acquired. In both protocols, RT3DE endocardial and epicardial surfaces were semiautomatically identified at end diastole (QLab, Philips Medical Systems, Andover, MA) to calculate LVM. CMR, 2D, and M-mode-derived LVM were obtained using standard techniques.

RESULTS

A significant correlation (r = 0.95) was noted between RT3DE and CMR-derived LVM with a small bias of -2 g. M-mode-derived LVM measurements (175 +/- 64 g) were significantly larger than RT3DE LVM (123 +/- 39 g, bias: 52 g) with moderate correlation (r = 0.76). No significant differences in LVM were noted between 2D (125 +/- 42 g) and RT3DE values (bias: 1.2 g) with good correlation (r = 0.91, P < .001). However, the best correlation was noted between RT3DE and RT3DE-guided biplane LVM values (r = 0.95, P < .001, bias: -4.6 g). Intraobserver, interobserver variability, and test-retest variability of the RT3DE measurements were 9%, 12%, and 6%, respectively.

CONCLUSION

RT3DE imaging using the 3D surface detection algorithm allows accurate and reproducible measurements of LVM. RT3DE-guided biplane technique can be used as an accurate time-saving alternative in clinical practice.

A study of functional anatomy of aortic-mitral valve coupling using 3D matrix transesophageal echocardiography

BACKGROUND

Mitral and aortic valves are known to be coupled via fibrous tissue connecting the two annuli. Previous studies evaluating this coupling have been limited to experimental animals using invasive techniques. The new matrix array transesophageal transducer provides high-resolution real-time 3D images of both valves simultaneously. We sought to develop and test a technique for quantitative assessment of mitral and aortic valve dynamics and coupling.

METHODS AND RESULTS

Matrix array transesophageal (Philips iE33) imaging was performed in 24 patients with normal valves who underwent clinically indicated transesophageal echocardiography. Custom software was used to detect and track the mitral and aortic annuli in 3D space throughout the cardiac cycle, allowing automated measurement of changes in mitral and aortic valve morphology. Mitral annulus surface area and aortic annulus projected area changed reciprocally over time. Mitral annulus surface area was 8.0+/-2.1 cm(2) at end-diastole and decreased to 7.7+/-2.1 cm(2) in systole, reaching its maximum (10.0+/-2.2 cm(2)) at mitral valve opening. Aortic annulus projected area was 4.1+/-1.2 cm(2) at end-diastole, then increased during isovolumic contraction reaching its maximum (4.8+/-1.3 cm(2)) in the first third of systole and its minimum (3.6+/-1.0 cm(2)) during isovolumic relaxation. The angle between the mitral and aortic annuli was maximum (136+/-13 degrees ) at end-diastole and decreased to its minimum value (129+/-11 degrees ) during systole.

CONCLUSIONS

This is the first study to report quantitative 3D assessment of the mitral and aortic valve dynamics from matrix array transesophageal images and describe the mitral-aortic coupling in a beating human heart. This ability may have impact on patient evaluation for valvular surgical interventions and prosthesis design.

The safety of deFinity and Optison for ultrasound image enhancement: a retrospective analysis of 78,383 administered contrast doses

BACKGROUND

The purpose of this retrospective analysis was to define the incidence of severe adverse events after exposure to ultrasound contrast agents.

METHODS

Data between January 1, 2001, and September 30, 2007, were collected using invited responses to an on-line web-based questionnaire from 1 general and 12 cardiac ultrasound laboratories. During a period of 4.5 +/- 2.4 years, a total of 66,164 doses of Definity (Lantheus Medical Imaging, North Billerica, MA) and 12,219 doses of Optison (GE Healthcare, Buckinghamshire, UK) were administered, reflecting contrast use in 5% of transthoracic and 28% of stress echocardiographic procedures. More than 10,000 doses were given to critically ill patients in intensive care unit settings or to patients with acute chest pain of suspected cardiac origin. The median age of patients who received an ultrasound contrast agent was 60 years, 49% were male, and the mean body mass index was 32 +/- 1.4 g/m(-2).

RESULTS

Severe reactions that were considered "probably" related to an ultrasound contrast agent developed in 8 patients (0.01%), all of whom were outpatients, and 4 (0.006%) of these were consistent with anaphylactoid reactions. There were no deaths reported. All patients recovered with treatment. No serious events were seen in inpatients.

CONCLUSION

This multicenter, retrospective analysis includes the largest number of doses of ultrasound contrast agents ever published and a large number of patients evaluated in a wide variety of settings, including the critically ill. It shows that these agents have a good safety profile in both cardiac and abdominal ultrasound applications. The incidence of severe adverse reactions to ultrasound contrast agents is no greater, and may be lower, than that reported for contrast agents commonly used in other cardiac imaging tests.

Real-time three-dimensional transesophageal echocardiography in valve disease: comparison with surgical findings and evaluation of prosthetic valves

BACKGROUND

Recently, a novel real-time 3-dimensional (3D) matrix-array transesophageal echocardiographic (3D-MTEE) probe was found to be highly effective in the evaluation of native mitral valves (MVs) and other intracardiac structures, including the interatrial septum and left atrial appendage. However, the ability to visualize prosthetic valves using this transducer has not been evaluated. Moreover, the diagnostic accuracy of this new technology has never been validated against surgical findings. This study was designed to (1) assess the quality of 3D-MTEE images of prosthetic valves and (2) determine the potential value of 3D-MTEE imaging in the preoperative assessment of valvular pathology by comparing images with surgical findings.

METHODS

Eighty-seven patients undergoing clinically indicated transesophageal echocardiography were studied. In 40 patients, 3D-MTEE images of prosthetic MVs, aortic valves (AVs), and tricuspid valves (TVs) were scored for the quality of visualization. For both MVs and AVs, mechanical and bioprosthetic valves, the rings and leaflets were scored individually. In 47 additional patients, intraoperative 3D-MTEE diagnoses of MV pathology obtained before initiating cardiopulmonary bypass were compared with surgical findings.

RESULTS

For the visualization of prosthetic MVs and annuloplasty rings, quality was superior compared with AV and TV prostheses. In addition, 3D-MTEE imaging had 96% agreement with surgical findings.

CONCLUSIONS

Three-dimensional matrix-array transesophageal echocardiographic imaging provides superb imaging and accurate presurgical evaluation of native MV pathology and prostheses. However, the current technology is less accurate for the clinical assessment of AVs and TVs. Fast acquisition and immediate online display will make this the modality of choice for MV surgical planning and postsurgical follow-up.

Semi-automated analysis of dynamic changes in myocardial contrast from real-time three-dimensional echocardiographic images as a basis for volumetric quantification of myocardial perfusion

AIMS

Despite the potential of real-time three-dimensional (3D) echocardiography (RT3DE) to assess myocardial perfusion, there is no quantification method available for perfusion analysis from RT3DE images. Such method would require 3D regions of interest (ROI) to be defined and adjusted frame-by-frame to compensate for cardiac translation and deformation. Our aims were to develop and test a technique for automated identification of 3D myocardial ROI suitable for translation-free quantification of myocardial videointensity over time, MVI(t), from contrast-enhanced RT3DE images.

METHODS AND RESULTS

Twelve transthoracic RT3DE (Philips) data sets obtained in pigs during transition from no contrast to steady-state enhancement (Definity) were analysed using custom software. Analysis included: (i) semi-automated detection of left ventricular endo- and epicardial surfaces using level-set techniques in one frame to define a 3D myocardial ROI, (ii) rigid 3D registration to reduce translation and rotation, (iii) elastic 3D registration to compensate for deformation, and (iv) quantification of MVI(t) in the 3D ROI from the registered and non-registered data sets to assess the effectiveness of registration. For each MVI(t) curve we computed % variability during steady-state enhancement (100 x SD/mean) and goodness of fit (r2) to the indicator dilution equation MVI(t) = A[1-exp(-betat)]. Analysis of myocardial contrast throughout contrast inflow was feasible in all data sets. Three-dimensional registration improved MVI(t) curves in terms of both % variability (2.8 +/- 1.8 to 1.5 +/- 0.9%; P < 0.05) and goodness of fit (r2 from 0.79 +/- 0.2 to 0.90 +/- 0.1; P < 0.05).

CONCLUSION

This is the first study to describe a new technique for semi-automated volumetric quantification of myocardial contrast from RT3DE images that includes registration and thus provides the basis for 3D measurement of myocardial perfusion.