Right ventricular outflow tract imaging with CT and MRI: Part 1, Morphology

Cardiac Computed Tomographic Angiography Evaluation of Right Ventricle-Pulmonary Artery Conduits with Surgical Correlation

Right ventricle-pulmonary artery (RV-PA) conduits are used in the treatment of certain congenital heart disease (CHD). RV-PA conduit complications might develop over time and require intervention. To evaluate how well cardiac computed tomographic angiography (CCTA) performs compared to transthoracic echocardiography (TTE) in evaluating RV-PA conduit complications by using surgical findings as the reference standard. A retrospective chart review of all patients over a 5-year period who underwent CCTA for RV-PA conduit evaluation was performed. Patient demographics and clinical data were recorded. Preoperative CCTA and TTE findings were compared to the operative findings for concordance or discordance. Forty-one patients were included, 51% females. The complications were conduit stenosis (28.68%), infection (7.17%) and aneurysm/pseudoaneurysm (6.15%). TTE and CCTA were consistently able to visualize focal conduit stenosis (96%). The greatest discrepancy between TTE and CCTA was in evaluating for aneurysm/pseudoaneurysm, where TTE detected only 2/6 (33%) compared to CCTA which detected 6/6 (100%) of the cases. However, TTE was slightly better at detecting conduit infection (3/7, 43%) compared to CCTA (2/7, 29%). Note that 5 out of 7 patients with endocarditis had bovine jugular graft. CCTA and TTE provide similar diagnostic accuracy evaluating certain types of RV-PA conduit complications. However, certain complications were only visualized on CCTA or TTE making both modalities complementary to each other during diagnostic evaluation.

Dynamic cardiac computed tomography characteristics of double-chambered right ventricle

To introduce image characteristics of double-chambered right ventricle on cardiac computed tomography and set a diagnostic criterion for the diagnosis. We retrospectively collected and measured the right ventricular constrictive ratio on computed tomography images in children who had simple ventricular septal defects in the past 10 years, because double-chambered right ventricle is often associated with ventricular septal defects. The right ventricular constrictive ratio was defined as the subinfundibular cross-sectional intraluminal area during end-systole divided by the area during end-diastole in the same patient. We compared the right ventricular constrictive ratio between subjects with concomitant double-chambered right ventricle and those without. 52 children were included, and 23 (44.2%) of them have concomitant double-chambered right ventricle. In most cases (n = 21; 91.3%), the hypertrophied muscular bundles occur just inferior to the level of the supraventricular crest in the right ventricle. Mean right ventricular constrictive ratio in patients with double-chambered right ventricle (15%) was significantly smaller than that without (29%). A cut-off value of a right ventricular constrictive ratio less than 20.1% was established to diagnose double-chambered right ventricle with an 89.7% sensitivity and 78. 3% specificity. Right ventricular constrictive ratio can be a valuable asset for the preoperative diagnosis of double-chambered right ventricle with cardiac computed tomography.

Spatial Distribution of Idiopathic Ventricular Arrhythmias Originating Around the Pulmonary Root: Lessons From Intracardiac Echocardiography

OBJECTIVES

The purpose of this study was to investigate the spatial distribution of ventricular arrhythmias (VAs) and their relationship with anatomic landmarks in the right ventricular outflow tract (RVOT).

BACKGROUND

Although controversy has mainly focused on whether VAs ablated in the RVOT originate above or below the pulmonary sinus, little is known about their actual distribution.

METHODS

We performed mapping and ablation in the reconstructed RVOT using intracardiac echocardiography (ICE) and summarized the spatial electroanatomic characteristics of RVOT-VAs.

RESULTS

A total of 50 VAs were recruited and were distributed among the 3 subregions: the pulmonary sinuses (19 of 50, 38%), sinus junctions (18 of 50, 36%), and infundibulum (13 of 50, 26%). In total, 70% (35 of 50) of ablation targets were within 10 mm (mean 4.3 ± 2.7 mm) of the pulmonary valve hinge point. An ablation target with both amplitude ≤1.14 mV and duration ≥101.5 milliseconds predicted an origin above the pulmonary sinus with a sensitivity of 84.2% and specificity of 84.4%. For the ablation targets (13 of 50, 26%) located in the infundibulum of the RVOT, 4 were surrounded by trabeculations, whereas only 1 ablation target in the sinus junction abutted the trabeculation (30.8% vs 5.6%).

CONCLUSIONS

Ablation targets of RVOT-VAs were mainly distributed around the hinge point of the pulmonary valve and the trabeculation of the infundibulum. ICE can clearly and precisely locate those anatomic landmarks of the RVOT.

Mitral valve Doppler for cardiac output assessment in preterm neonates

INTRODUCTION

Cardiac output (CO) assessment in neonates is commonly done by echocardiography. It is unclear which is the best site to measure the left ventricular (LV) outflow tract for CO assessment (the aortic valve [AV] aortic sinus [AS] or the sinotubular junction [STJ]). In the normal heart, the blood flow entering the LV equals the blood ejected from it. Therefore, measuring the blood flow into the LV through the mitral valve (MV) is an alternative way to measure CO.

METHODS

In stable preterm infants the MV CO was compared with the right ventricular (RV) CO and the three ways to measure LV CO, in 30 stable preterm neonates. Interobserver variability for MV CO was established.

RESULTS

In the 30 neonates studied, MV CO was best correlated and had a minimal bias to the RV CO and LV CO measured at the STJ. Left ventricular CO measured at the AV and AS had significant bias relative to RV CO and MV CO. MV CO inter-observer variability was similar to other echocardiographic CO assessment methods.

CONCLUSION

MV CO may be used as an alternative way to assess CO. The STJ may be the optimal site to measure LV outflow tract.

Catheter ablation of outflow tract ventricular arrhythmia with intracardiac echocardiography assistance

As the indications for catheter-based electrophysiologic procedures become more diverse and complex, accurate assessment of the anatomy of intracardiac structure has become essential for the optimal clinical outcome. Since intracardiac echocardiography (ICE) was first introduced in 1980, it has become an integral part of various electrophysiologic procedures enabling accurate visualization of cardiac structures and continuous monitoring of catheter position, with integration of real-time images and electroanatomic mapping. Catheter ablation for outflow tract ventricular arrhythmias (OTVAs) has been actively performed in symptomatic patients. However, the anatomic complexity of OT serves as the biggest obstacle to obtain the optimal results. In OTVAs, ICE has played an invaluable role in precisely defining the anatomic shell of OT beyond fluoroscopy and in guiding catheter manipulation in relation to critical structures like the conduction system and coronary arteries. This review article provides detailed information on comprehensive application of ICE for catheter ablation of OTVAs.

Perioperative right ventricular function and dysfunction in adult cardiac surgery-focused review (part 1-anatomy, pathophysiology, and diagnosis)

Right ventricle (RV) dysfunction and failure are now increasingly recognized as an important cause of perioperative morbidity and mortality after cardiac surgery. Although RV dysfunction is common, RV failure is very rare (0.1%) after routine cardiac surgery. However, it occurs in 3% of patients after heart transplantation and in up to 30% of patients after left ventricular assist device implantation. Significant RV failure after cardiac surgery has high mortality. Knowledge of RV anatomy and physiology are important for understanding RV dysfunction and failure. Echocardiography and haemodynamic monitoring are the mainstays in the diagnosis of RV dysfunction and failure. While detailed echocardiography assessment of right heart function has been extensively studied and validated in the elective setting, gross estimation of RV chamber size, function, and some easily obtained quantitative parameters on transesophageal echocardiography are useful in the perioperative setting. However, detailed knowledge of echocardiography parameters is still useful in understanding the differences in contractile pattern, ventriculo-arterial coupling, and interventricular dependence that ensue after open cardiac surgery.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s12055-021-01240-y.

Validity of cardiovascular magnetic resonance in pre- and post-operative evaluation of pulmonary arteries and ventricular functions in pediatric conotruncal anomalies

Background

The aim of this work is to evaluate the validity of magnetic resonance (MR) imaging in assessment of pulmonary arteries and ventricular functions with conotruncal anomalies in the pediatric population.

Results

Between March 2018 and December 2019, 42 patients ranging in age from 6 months to 18 years and diagnosed with conotruncal anomalies by echocardiographic examination were submitted for cardiac MRI followed by assessment of their morphological (intra- and extra-cardiac anatomy) and functional parameters. The most common conotruncal anomaly was tetralogy of Fallot which represented 45% of the cases. Cardiac magnetic resonance (CMR) compared to echocardiography showed 46% agreement in the assessment of right ventricular volumes and function. There was only 37% agreement between echocardiography and MRI in delineation of MAPCAS.

Conclusion

CMR provides a powerful tool, giving anatomical and physiological information that echocardiography and catheterization alone cannot provide in conotruncal anomalies.

Double Outlet Right Ventricle: In-Depth Anatomic Review Using Three-Dimensional Cardiac CT Data

Double outlet right ventricle (DORV) is a relatively common congenital heart disease in which both great arteries are connected completely or predominantly to the morphologic RV. Unlike other congenital heart diseases, DORV demonstrates various anatomic and hemodynamic subtypes, mimicking ventricular septal defect, tetralogy of Fallot, transposition of the great arteries, and functional single ventricle. Because different surgical strategies are applied to different subtypes of DORV with ventricular septal defects, a detailed assessment of intracardiac anatomy should be performed preoperatively. Due to high spatial and contrast resolutions, cardiac CT can provide an accurate characterization of various intracardiac morphologic features of DORV. In this pictorial essay, major anatomic factors affecting surgical decision-making in DORV with ventricular septal defects were comprehensively reviewed using three-dimensional cardiac CT data. In addition, the surgical procedures available for these patients and major postoperative complications are described.

State-of-the-Art Review: Anatomical and Imaging Considerations During Transcatheter Tricuspid Valve Repair Using an Annuloplasty Approach

Transcatheter techniques for the treatment of tricuspid regurgitation (TR) are being more frequently used and several new devices are in development. Since 90% of patients with TR have secondary TR, catheter based systems which reduce the dilated tricuspid annulus area are of particular interest. In order to perform an annuloplasty procedure effectively and safely, knowledge about the anatomy of the tricuspid valve apparatus and especially of the annulus in relation to the important neighboring structures such as the aortic root, the RCA, the electrical pathways and the CS is fundamental. In addition, comprehensive understanding of the device itself, the delivery system, its maneuverability and the individual procedural steps is required. Furthermore, the use of multi-modality imaging is important. For each step of the procedure the appropriate imaging modality as well as the optimal; imaging planes are crucial to provide the necessary information to best guide the individual procedural step.

Exercise cardiac magnetic resonance imaging to assess dynamic right ventricular outflow tract obstruction in congenital heart disease: a case report

Background

Right ventricular outflow tract obstruction in patients with congenital heart disease is usually assessed using echocardiographic peak instantaneous gradient at rest. Since right ventricular outflow tract obstruction may change during exercise (dynamic right ventricular outflow tract obstruction), we present a case emphasizing the potential use of exercise cardiac magnetic resonance imaging (CMR).

Case summary

We discuss a 15-year-old patient with repaired mid-ventricular sub-pulmonary stenosis type double-chambered right ventricle causing right ventricular outflow tract obstruction and symptoms on exertion. In this case, exercise CMR imaging provided additional information, allowing adequate surgical planning.

Discussion

The additional value of exercise CMR imaging in a case of right ventricular outflow tract obstruction was described. Although exercise cardiac magnetic resonance imaging did not show a significant increase in peak gradient across the right ventricular outflow tract obstruction, shifting and D-shaping of the interventricular septum with subsequent insufficient left ventricular filling (preload) was observed in the patient with recurrent double-chambered right ventricle. This case demonstrates how exercise CMR imaging can be helpful in the clinical decision beyond standard echocardiographic evaluation by providing additional evidence of adverse haemodynamics during exercise.

Amplitude of QRS complex within initial 40 ms in V2 (V2QRSi40): Novel electrocardiographic criterion for predicting accurate localization of outflow tract ventricular arrhythmia origin

BACKGROUND

The initial depolarization vector of outflow tract (OT) ventricular arrhythmia (VA) varies in different origins, which may help to predict OT-VA origin more accurately.

OBJECTIVE

The purpose of this study was to develop a more accurate electrocardiographic (ECG) criterion for differentiating between left and right OT-VA origins.

METHODS

We studied 275 patients with successful ablation in the right ventricular outflow tract (RVOT) (n = 207) or left ventricular outflow tract (LVOT) (n = 68) in the development cohort. Amplitude of the QRS complex within initial 40 ms (QRS_i40) in precordial leads was measured. A novel criterion for identifying OT-VA origin was developed based on the development cohort. Predictive performance of novel criterion was further validated by comparing with previous ECG criteria (V₂S/V₃R index, V₂ transition ratio, and transition zone index) in the validation cohort with 107 patients (RVOT 75; LVOT 32).

RESULTS

QRS_i40 of identical precordial leads were significantly greater in the LVOT group than the RVOT group (P <.05). In the development cohort, QRS_i40 of V₂ (V₂QRS_i40) exhibited the greatest area under the curve of 0.950, with cutoff ≥0.52 mV predicting LVOT origin (sensitivity 86.0%; specificity 94.6%). In the validation cohort, V₂QRS_i40 ≥0.52 mV outperformed previous criteria in predictive performance (accuracy 90.7%; sensitivity 84.4%; specificity 93.3%). This advantage of V₂QRS_i40 over previous criteria also held true for subgroups of transition zone index = 0 and V₃ R/S transition.

CONCLUSION

V₂QRS_i40 is a novel and accurate ECG criterion to predict OT-VA origin that outperforms previous criteria.

Retinoic Acid Signaling and Heart Development

As the first organ to form and function in all vertebrates, the heart is crucial to development. Tightly-regulated levels of retinoic acid (RA) are critical for the establishment of the regulatory networks that drive normal cardiac development. Thus, the heart is an ideal organ to investigate RA signaling, with much work remaining to be done in this area. Herein, we highlight the role of RA signaling in vertebrate heart development and provide an overview of the field's inception, its current state, and in what directions it might progress so that it may yield fruitful insight for therapeutic applications within the domain of regenerative medicine.

Imaging Needs in Novel Transcatheter Tricuspid Valve Interventions

The advent of novel transcatheter therapies for severe tricuspid regurgitation (TR) has attracted much attention. Novel 3-dimensional imaging techniques have permitted analysis of the tricuspid valve (TV) anatomy from unparalleled views and better understanding of the underlying pathophysiology of TR. Grading TR and assessment of right ventricular function remain challenging, and although 2-dimensional echocardiography is the mainstay imaging technique to evaluate patients with severe TR the use of 3-dimensional echocardiography and cardiovascular magnetic resonance is increasing. The number of transcatheter interventions for TR is growing, and procedural success relies significantly on the pre-procedural evaluation of the anatomy of the TV, etiology and severity of TR, right ventricular size and function, and importantly, the anatomic relationships of the TV. The role of multimodality imaging in patient selection and procedural planning for transcatheter TV repair is reviewed.

Radiologist's Guide to Diagnosis of Fetal Cardiac Anomalies on Prenatal Ultrasound Imaging

Congenital cardiac anomalies are a common finding during prenatal anatomical survey ultrasound examination. Cardiac anomalies are a major cause of prenatal and neonatal mortality and morbidity. If the anomaly is not lethal, most would require surgical correction. Therefore, early recognition of these abnormalities is essential for parental counseling and delivery planning, as well as analysis of neonatal treatment options. Although prenatal ultrasound plays an important role in identification of such anomalies, diagnosis and interpretation of imaging findings require familiarity and knowledge of the common imaging features. In this article, we provide a comprehensive review of ultrasound appearance of common fetal cardiac anomalies.

Cross-sectional imaging of congenital pulmonary artery anomalies

Congenital pulmonary artery (PA) anomalies comprise a rare and heterogeneous spectrum of disease, ranging from abnormal origins to complete atresia. They may present in early infancy or more insidiously in adulthood, often in association with congenital heart disease such as tetralogy of Fallot or other syndromes. In recent years, cross-sectional imaging, including computed tomography (CT) and magnetic resonance imaging (MRI), has become widely utilized for the noninvasive assessment of congenital PA diseases, supplementing echocardiography and at times supplanting invasive angiography. In this article, modern CT and MRI techniques for imaging congenital PA disorders are summarized. The key clinical features, cross-sectional imaging findings, and treatment options for the most commonly encountered entities are then reviewed. Emphasis is placed on the ever-growing role of cross-sectional imaging options in facilitating early and accurate diagnosis and tailored treatment.

Evaluation of right ventricular function by coronary computed tomography angiography using a novel automated 3D right ventricle volume segmentation approach: a validation study

OBJECTIVES

To evaluate right ventricle (RV) function by coronary computed tomography angiography (CTA) using a novel automated three-dimensional (3D) RV volume segmentation tool in comparison with clinical reference modalities.

METHODS

Twenty-six patients with severe end-stage heart failure [left ventricle (LV) ejection fraction (EF) <35%] referred to CTA were enrolled. A specific individually tailored biphasic contrast agent injection protocol was designed (80%/20% high/low flow) was designed. Measurement of RV function [EF, end-diastolic volume (EDV), end-systolic volume (ESV)] by CTA was compared with tricuspid annular plane systolic excursion (TAPSE) by transthoracic echocardiography (TTE) and right heart invasive catheterisation (IC).

RESULTS

Automated 3D RV volume segmentation was successful in 26 (100%) patients. Read-out time was 3 min 33 s (range, 1 min 50s-4 min 33s). RV EF by CTA was stronger correlated with right atrial pressure (RAP) by IC (r = -0.595; p = 0.006) but weaker with TAPSE (r = 0.366, p = 0.94). When comparing TAPSE with RAP by IC (r = -0.317, p = 0.231), a weak-to-moderate non-significant inverse correlation was found. Interobserver correlation was high with r = 0.96 (p < 0.001), r = 0.86 (p < 0.001) and r = 0.72 (p = 0.001) for RV EDV, ESV and EF, respectively. CT attenuation of the right atrium (RA) and right ventricle (RV) was 196.9 ± 75.3 and 217.5 ± 76.1 HU, respectively.

CONCLUSIONS

Measurement of RV function by CTA using a novel 3D volumetric segmentation tool is fast and reliable by applying a dedicated biphasic injection protocol. The RV EF from CTA is a closer surrogate of RAP than TAPSE by TTE.

KEY POINTS

• Evaluation of RV function by cardiac CTA by using a novel 3D volume segmentation tool is fast and reliable. • A biphasic contrast agent injection protocol ensures homogenous RV contrast attenuation. • Cardiac CT is a valuable alternative modality to CMR for the evaluation of RV function.

Propulsion of blood through the right heart circulatory system

Venous return, the right heart function and the pulmonary circulation is an integrated functional unit. The right ventricle is particularly load sensitive, and will be influenced directly by the venous and pulmonary physiology. In this paper we present important physiological principles that govern the diagnosis and treatment of dysfunctions affecting the return of blood to the heart and the transfer of the cardiac output from the right to the left side. We do evaluate both basic science and the clinical literature pointing to practical aspects of physiological knowledge.

Inadequacy of fluoroscopy and electrocardiogram in predicting septal position in RVOT pacing - Validation with cardiac computed tomography

BACKGROUND

Electrocardiographic (ECG) and fluoroscopic criteria, which are the only available guides to achieve a true septal position during right ventricular outflow tract (RVOT) pacing, have been infrequently validated. We sought to validate these using cardiac computed tomographic angiography (CTA) to confirm lead position within the RVOT septum.

METHODS

Forty-four patients with permanent pacemaker leads in the RVOT position underwent CTA. Lead positions in RVOT were classified as anterior, free wall, or septal location. Fluoroscopic images were obtained in 4 standard views.

RESULTS

Only 19 (43%) patients had lead in true septal position within the RVOT in CTA while 25 patients (57%) were found to have an anterior lead location. Mean QRS axis, QRS duration, negative QRS in lead I, and notching in inferior leads were not significantly different between the two groups. The standard fluoroscopic LAO view showed a rightward-directed lead not only in all 19 patients with septal location, but also in 14/25 patients in the anterior location (p=0.22), and thus had a sensitivity of 100% but specificity of only 16% in predicting true septal position. The posteriorly directed lead in left lateral view was more accurate in predicting true septal position with good sensitivity (73.7%) and excellent specificity (80%).

CONCLUSIONS

This study, using validation with CTA, showed that conventional ECG criteria and fluoroscopy are inaccurate in differentiating septal from anterior RVOT pacing. The fluoroscopic lateral view, as corroborated by CTA, is more reliable than the LAO view in predicting septal lead placement.

Clinical cardiac structural anatomy reconstructed within the cardiac contour using multidetector-row computed tomography: Left ventricular outflow tract

The left ventricular outflow tract (LVOT) is a common site of idiopathic ventricular arrhythmia. Many electrocardiographic characteristics for predicting the origin of arrhythmia have been reported, and their prediction rates are clinically acceptable. Because these approaches are inductive, based on QRS-wave morphology during the arrhythmia and endocardial or epicardial pacing, three-dimensional anatomical accuracy in identifying the exact site of the catheter position is essential. However, fluoroscopic recognition and definition of the anatomy around the LVOT can vary among operators, and three-dimensional anatomical recognition within the cardiac contour is difficult because of the morphological complexity of the LVOT. Detailed knowledge about the three-dimensional fluoroscopic cardiac structural anatomy could help to reduce the need for contrast medium injection and radiation exposure, and to perform safe interventions. In this article, we present a series of structural images of the LVOT reconstructed in combination with the cardiac contour using multidetector-row computed tomography. We also discuss the clinical implications of these findings based on the accumulated insights of research pioneers.

Imaging pitfalls, normal anatomy, and anatomical variants that can simulate disease on cardiac imaging as demonstrated on multidetector computed tomography

Advances in computed tomography have led to continuous improvement in cardiac imaging. Dedicated postprocessing capabilities, faster scan times, and cardiac gating methods reveal details of normal cardiac anatomy and anatomic variants that can mimic pathologic conditions. This article will review normal cardiac anatomy and variants that can mimic disease. Radiologists should be familiar with normal cardiac anatomy and anatomic variants to avoid misinterpretation of normal findings for pathologic processes.