Intracardiac echocardiography: in vitro and in vivo validation for right ventricular volume and function

The use of intracardiac echocardiography during percutaneous pulmonary valve replacement

High-quality live imaging assessment of cardiac valves and cardiac anatomy is crucial for the success of catheter-based procedures. We present our experience using Intracardiac echocardiography (ICE) during transcatheter Percutaneous Pulmonary Valve replacement (tPVR).This is a retrospective study that included 35 patients who underwent tPVR between April 2008 and June 2012. Thirty-one of these patients had the procedure performed under continuous ICE guidance. Pre-procedure transthoracic echocardiography (TTE) was obtained in all patients. ICE was performed at baseline, during the procedure, and at the conclusion of the procedure. Comparisons between the pre-procedure TTE and baseline ICE data and between post-procedure ICE data and the following day TTE were performed. Total of 35 patients had tPVR during the above-mentioned time period. Twenty-one patients received the Edwards Sapien valve and 14 patients had the Melody valve. Thirty-one patients had the procedure performed under continuous ICE guidance. The mean Pre-TTE peak gradient (PG) and Pre-ICE-PG were 45.5 ± 20 vs 33 ± 13 mmHg (p < 0.001) and the mean Pre-TTE mean gradient (MG) and Pre-ICE-MG were 27.7 ± 13 vs 21 ± 18 mmHg (p < 0.001). The mean Post-TTE- PG and Post-ICE-PG were 24.3 ± 11 vs 15.3 ± 7 mmHg (p < 0.001) and the mean of the Post-TTE-MG and Post-ICE-MG were 14.2 ± 7 vs 8.4 ± 4 mmHg (p < 0.001). There was a good correlation between peak ICE and TTE gradient at baseline and after valve placement. For the degree of pulmonary regurgitation, there was no significant difference between TTE and ICE. ICE is an important modality to guide tPVR in patients with dysfunctional homograft valve between the right ventricle and pulmonary artery and should be used to assess valve function before, during and immediately after the procedure.

Imaging techniques and the evaluation of the right heart and the pulmonary circulation

Since the right side of the heart and the pulmonary circulation are regarded as secondary components of the circulatory system, their role in disease has traditionally not received the same attention as their counterparts in the systemic circulation. This was partly because precise noninvasive study of these structures was difficult. For many years, chest radiography and invasive angiography were the only techniques available for imaging the minor circulation. The development of transthoracic echocardiography and nuclear techniques has produced a significant leap forward for noninvasive imaging, particularly of the right ventricle. More recently, novel echocardiographic techniques, and advances in computed tomography and magnetic resonance imaging, in particular, have expanded our diagnostic armamentarium and provided new insights into the anatomy and function of the pulmonary circulation in both health and disease. This article contains a review of the current status of techniques for imaging the right side of the heart and the pulmonary circulation.

Echocardiography-guided interventions

A major advantage of echocardiography over other advanced imaging modalities (magnetic resonance imaging, computed tomographic angiography) is that echocardiography is mobile and real time. Echocardiograms can be recorded at the bedside, in the cardiac catheterization laboratory, in the cardiovascular intensive care unit, in the emergency room-indeed, any place that can accommodate a wheeled cart. This tremendous advantage allows for the performance of imaging immediately before, during, and after various procedures involving interventions. The purpose of this report is to review the use of echocardiography to guide interventions. We provide information on the selection of patients for interventions, monitoring during the performance of interventions, and assessing the effects of interventions after their completion. In this document, we address the use of echocardiography in commonly performed procedures: transatrial septal catheterization, pericardiocentesis, myocardial biopsy, percutaneous transvenous balloon valvuloplasty, catheter closure of atrial septal defects (ASDs) and patent foramen ovale (PFO), alcohol septal ablation for hypertrophic cardiomyopathy, and cardiac electrophysiology. A concluding section addresses interventions that are presently investigational but are likely to enter the realm of practice in the very near future: complex mitral valve repairs, left atrial appendage (LAA) occlusion devices, 3-dimensional (3D) echocardiographic guidance, and percutaneous aortic valve replacement. The use of echocardiography to select and guide cardiac resynchronization therapy has recently been addressed in a separate document published by the American Society of Echocardiography and is not further discussed in this document. The use of imaging techniques to guide even well-established procedures enhances the efficiency and safety of these procedures.

A comparison of echocardiographic modalities to guide structural heart disease interventions

Percutaneous techniques to treat structural heart disease are rapidly evolving based on innovative interventions and the considerable advancement in image guidance technology. While two-dimensional transthoracic and transesophageal echocardiography have been integral to procedural planning and execution, intracardiac and three-dimensional echocardiography supply unique visualization of target structures with a potential improvement in patient safety and procedural efficacy. The choice of image guidance modality is based on specific differences between imaging systems, as well as other variables including cost, patient safety, operator expertise, and complexity of procedure. We will compare the adjunctive imaging tools for structural heart disease interventions, with a focus on intracardiac echocardiography and real-time three-dimensional transesophageal echocardiography.

An Abnormal Right Ventricular Apical Angle is Indicative of Global Right Ventricular Impairment

The presence of right ventricular (RV) dysfunction is an adverse prognostic indicator but current echocardiographic methods have some limitations. RV apical angles in systole and diastole were correlated with known parameters of RV function in patients without pulmonary hypertension (Group 1) and in patients with pulmonary hypertension (Group 2). RV apical angles were significantly smaller in both systole (22 +/- 7 degrees) and diastole (33 +/- 6 degrees) in Group 1 patients when compared to Group 2 (54 +/- 18 degrees, p < 0.0001 and 59 +/- 17 degrees, p < 0.0001, respectively). RV apical angles, both in systole and diastole, were strongly correlated with RV end-systolic area (R = 0.89, p < 0.0001) and end-diastolic area (R = 0.81, p < 0.0001), respectively. Similarly, the apical systolic and diastolic angle correlated well with decreased tricuspid annular plane systolic excursion (TAPSE, R = -0.76 and R = -0.73, p < 0.001) as well as with decreased RV fractional area change (R = -0.81 and R = -0.77, p < 0.001). Therefore, we conclude that this new measurement of RV apical angle is simple and useful to quantify RV apical structural and functional abnormalities that are well correlated with global RV impairment in patients with chronic pulmonary hypertension.

Use of Intracardiac Echocardiography to Guide Catheter Closure of Atrial Communications

Intracardiac echocardiography (ICE) is slowly replacing transesophageal echocardiography as the preferred imaging tool to guide device closure of atrial septal defects and patent foramen ovale. This article is a brief review of the literature related to ICE, the technical aspects ICE imaging, techniques for obtaining the standard views, and the future directions of this methodology.

Normal regional right ventricular function and its change with age: a Doppler myocardial imaging study

BACKGROUND

Doppler Myocardial Imaging (DMI) is a new technique currently being studied for the assessment of regional systolic and diastolic left ventricular (LV) function. No normal values or data on age-related changes in regional myocardial right ventricular (RV) velocities are available.

METHODS AND RESULTS

Color DMI was used in 32 healthy volunteers (aged 16-76 years) to derive regional velocities from basal, medial, and apical segments of the RV free wall in the apical 4-chamber view, and from distal segments as well as from the tricuspid annulus in the parasternal long-axis view. Both mitral annular and regional LV velocities (4-chamber, long-axis parasternal view) were also recorded and compared with corresponding RV regional velocities. The M-mode displacement of the cardiac base was measured. Corresponding RV and LV DMI data sets were compared. For longitudinal function, RV free wall systolic velocities were consistently higher than velocities recorded in corresponding LV segments (analysis of variance, P <.05). Older subjects (40-76 years; 13 men, 2 women) had lower RV long-axis regional velocities than younger subjects (16-39 years; 15 men, 2 women), but had higher short-axis RV systolic velocities. For diastolic velocities, a negative correlation between age and the ratio of regional early diastolic to late diastolic velocity was shown for all RV free wall segments (eg, basal segment: r = -0.63, P <.0001).

CONCLUSIONS

The right ventricle has higher long-axis regional velocities, a greater excursion of its lateral atrioventricular valve ring, and reduced circumferential shortening velocities compared with the left ventricle. Right ventricular longitudinal shortening is dominant over short-axis function in healthy young subjects. Normal age-related changes of diastolic velocities for each segment of the normal RV free wall have been defined.

Transvascular Imaging: Feasibility Study Using a Vector Phased Array Ultrasound Catheter

BACKGROUND: Transvascular imaging is defined as the acquisition of anatomic and functional information of structures lying beyond the confines of a vascular conduit within which the imaging device resides. Interrogating structures surrounding the vascular conduit is the subject of this feasibility study using a novel underblood, phased array ultrasound-tipped catheter. METHODS: An intravascular catheter (10-F, 3.2-mm-diameter, four-way articulation) tipped with a 5.5- to 10-MHz frequency agile, vector phased array transducer with full Doppler capability (Sequoia, Acuson) was used. The imaging transducer has a wide range of tissue penetration (2 mm to >10 cm from the lens). The catheter was introduced via an 11-Fr femoral venous sheath into the inferior and superior vena cavae and right heart chambers. As the catheter was advanced, attention was directed to visualization of structures surrounding the vessel in which the catheter resided. RESULTS: From the cavae and femoral vein the thoracic, abdominal and femoral arteries could be easily imaged. Anatomy that was visualized included the liver, hepatic veins, gallbladder, and mesenteric vessels. Normal and pathological anatomy and Doppler physiology could be readily appreciated. Doppler (i.e., pulsed- and continuous-wave, color flow, and tissue Doppler) fostered unique transvascular physiological hemodynamic and flow assessment. CONCLUSION: Transvascular imaging is feasible in human subjects using this 10-Fr catheter tipped with a 5.5- to 10-MHz vector phased array transducer. Intravascular navigation to a desired location within the body and the performance of diagnostic or therapeutic procedures at a remote site under direct ultrasound visualization are possible. Full Doppler capability extends the concept of transvascular hemodynamic and physiological assessment.

Intracardiac echocardiography: computerized detection of left ventricular borders

A semi-automated method for two- and three-dimensional analysis of intracardiac echocardiography (ICE) images and image sequences is reported based on detection of epicardial and endocardial borders using graph searching. The border detection method was applied to 50 ICE images acquired in vivo in five dogs and to 108 images in 16 volumetric ICE image sequences from eight cadaveric pig hearts. The ICE images from the in vivo study showed good correlation between computer-detected and observer-defined left ventricular (LV) cavity areas and epicardial areas (r = 0.99, y = 0.98x + 0.43 [cm2]; r = 0.99, y = 0.98x + 1.11 [cm2]; respectively). In the cadaveric hearts, the LV volumes were determined with the volume measurement error of 7.6 +/- 7.7% and 11.3 +/- 11.2% for the aortic valve and mitral valve image sequences, respectively. Our method facilitates an accurate and computationally efficient approach for the quantitative assessment of ICE image data in 2D and 3D.

[Right ventricular function: physiological and physiopathological features]

Sinus and conus constitute the two cavities of the right ventricle. They are anatomically and functionally different. The sinus is a flow-generator and the conus a pressure-regulator. The coronary circulation of the right ventricle is provided by the right coronary artery and the left anterior descending artery. The right ventricle is perfused during systole and diastole. When oxygen demand increases, coronary arteries dilate and oxygen extraction rises. As for the left ventricle, right ventricular performance depends upon heart rate, rhythm, contractility and loading conditions. Ventricular interactions are very important for right ventricular function. Loading conditions and contractility of the left ventricle are of major significance for right ventricular performance. For the right ventricle, the end of the ejection is different from the end of the active contraction. The time between them allows to achieve ventricular emptying. This duration is linked to afterload. Presently, it is impossible to accurately and simply assess these conditions. Pressure and volume overloadings result in right ventricular failure. They are responsible for ventricular dilation and ischaemia with a decrease in cardiac output, generating a vicious circle. Treatment includes the removal of the cause, and the maintenance of systemic arterial pressure and biventricular contractility. It is difficult to assess the effects of intravenous vasodilators on right ventricular afterload.