Imaging-based tricuspid valve anatomy by computed tomography, magnetic resonance imaging, two and three-dimensional echocardiography: correlation with anatomic specimen.

Interest on tricuspid valve (TV) (and hence in TV anatomy) has increased in the last two decades with the awareness that functional tricuspid regurgitation (FTR) is an insidious disease progressively leading to untreatable right heart failure and eventually to death. Medical therapy may alleviate symptoms, while surgical therapy may improve outcome but it is associated with high mortality and recurrence of significant regurgitation. Nowadays, an increasing number of left valve diseases are successfully treated through a percutaneous transcatheter approach. The negative impact that the untreated FTR may have in these patients has highlighted the necessity of developing transcatheter solutions also for FTR and numerous catheter devices for treating FTR are currently under evaluation. The essential pre-requisite for an effective and safe surgical or transcatheter therapy is a deep knowledge of the normal TV anatomy. In this review, we describe the anatomy of TV and surrounding structures as revealed by computed tomography, cardiac magnetic resonance, 2D/3D transthoracic echocardiography, and 2D/3D transoesophageal echocardiography emphasizing strengths and weaknesses of each of these imaging tools. To confirm the anatomical fidelity of these imaging modalities, where appropriate, the non-invasive images where presented, side-by-side, with corresponding images from anatomic specimens.

Imaging for Mitral Interventions: Methods and Efficacy.

The mitral valve (MV) is a complex and intricate structure. With the development of transesophageal echocardiography in the 1990s, it became possible to evaluate MV anatomy and function in real time during surgical procedures. Subsequently, new surgical and percutaneous techniques for MV repair as well as replacement have evolved. Development of 3-dimensional and intracardiac echocardiography, as well as computed tomography, cardiac resonance imaging, and most recently fusion imaging, have paved the way for a more comprehensive evaluation of the MV as well as for the planning of percutaneous MV procedures such as balloon valvuloplasty, paravalvular mitral leak closure, percutaneous edge-to-edge repair, transcatheter MV annuloplasty, artificial chord implantation, and transcatheter MV replacement. The applicability and use of the various imaging modalities for the assessment and guidance of therapy for MV disorders is discussed in this paper.

Personalized computational modeling of left atrial geometry and transmural myofiber architecture.

Atrial fibrillation (AF) is a supraventricular tachyarrhythmia characterized by complete absence of coordinated atrial contraction and is associated with an increased morbidity and mortality. Personalized computational modeling provides a novel framework for integrating and interpreting the role of atrial electrophysiology (EP) including the underlying anatomy and microstructure in the development and sustenance of AF. Coronary computed tomography angiography data were segmented using a statistics-based approach and the smoothed voxel representations were discretized into high-resolution tetrahedral finite element (FE) meshes. To estimate the complex left atrial myofiber architecture, individual fiber fields were generated according to morphological data on the endo- and epicardial surfaces based on local solutions of Laplace's equation and transmurally interpolated to tetrahedral elements. The influence of variable transmural microstructures was quantified through EP simulations on 3 patients using 5 different fiber interpolation functions. Personalized geometrical models included the heterogeneous thickness distribution of the left atrial myocardium and subsequent discretization led to high-fidelity tetrahedral FE meshes. The novel algorithm for automated incorporation of the left atrial fiber architecture provided a realistic estimate of the atrial microstructure and was able to qualitatively capture all important fiber bundles. Consistent maximum local activation times were predicted in EP simulations using individual transmural fiber interpolation functions for each patient suggesting a negligible effect of the transmural myofiber architecture on EP. The established modeling pipeline provides a robust framework for the rapid development of personalized model cohorts accounting for detailed anatomy and microstructure and facilitates simulations of atrial EP.

Intracardiac anatomical relationships and potential for streaming in double inlet left ventricles.

The aim of this study was to gain better understanding of the variable anatomical features of double inlet left ventricle hearts without cavopulmonary connection that would potentially facilitate favorable streaming. Thirty-nine post-mortem specimens of double inlet left ventricle without cavopulmonary connection were investigated. The focus was on anatomical characteristics that could influence the flow and separation of deoxygenated and oxygenated blood in the ventricles. Elements of interest were the ventriculoarterial connection, the spatial relationship of the ventricles, the position and size of the great arteries, the ventricular septal defect, the presence of relative outflow tract stenosis and the relationship of the inflow and outflow tracts. The most common anatomy was a discordant ventriculoarterial connection with an anatomically left-sided morphologically right ventricle (n = 12, 31%). When looking at the pulmonary trunk/aorta ratio, 21 (72%) hearts showed no pulmonary stenosis relative to the aorta. The ventricular septal defect created a relative subpulmonary or subaortic stenosis in 13 (41%) cases. Sixteen (41%) hearts had a parallel relationship of the inflow and outflow tracts, facilitating separation of deoxygenated and oxygenated blood streams. On the other end of the spectrum were 10 (25%) hearts with a perpendicular relationship, which might lead to maximum mixing of the blood streams. The relationship of the inflow and outflow tracts as well as the presence of (sub-) pulmonary stenosis might play a crucial role in the distribution of blood in double inlet left ventricle hearts. Additional in vivo studies will be necessary to confirm this postulation.

In vivo cardiovascular magnetic resonance diffusion tensor imaging shows evidence of abnormal myocardial laminar orientations and mobility in hypertrophic cardiomyopathy.

BACKGROUND: Cardiac diffusion tensor imaging (cDTI) measures the magnitudes and directions of intramyocardial water diffusion. Assuming the cross-myocyte components to be constrained by the laminar microstructures of myocardium, we hypothesized that cDTI at two cardiac phases might identify any abnormalities of laminar orientation and mobility in hypertrophic cardiomyopathy (HCM). METHODS: We performed cDTI in vivo at 3 Tesla at end-systole and late diastole in 11 healthy controls and 11 patients with HCM, as well as late gadolinium enhancement (LGE) for detection of regional fibrosis. RESULTS: Voxel-wise analysis of diffusion tensors relative to left ventricular coordinates showed expected transmural changes of myocardial helix-angle, with no significant differences between phases or between HCM and control groups. In controls, the angle of the second eigenvector of diffusion (E2A) relative to the local wall tangent plane was larger in systole than diastole, in accord with previously reported changes of laminar orientation. HCM hearts showed higher than normal global E2A in systole (63.9° vs 56.4° controls, p=0.026) and markedly raised E2A in diastole (46.8° vs 24.0° controls, p<0.001). In hypertrophic regions, E2A retained a high, systole-like angulation even in diastole, independent of LGE, while regions of normal wall thickness did not (LGE present 57.8°, p=0.0028, LGE absent 54.8°, p=0.0022 vs normal thickness 38.1°). CONCLUSIONS: In healthy controls, the angles of cross-myocyte components of diffusion were consistent with previously reported transmural orientations of laminar microstructures and their changes with contraction. In HCM, especially in hypertrophic regions, they were consistent with hypercontraction in systole and failure of relaxation in diastole. Further investigation of this finding is required as previously postulated effects of strain might be a confounding factor.

Anatomical classification of left atrial appendages in specimens applicable to CT imaging techniques for implantation of amplatzer cardiac plug.

BACKGROUND: Certain anatomical characteristics of the left atrial appendage (LAA) are associated with complexity in the implantation of occluder devices. OBJECTIVE: The aim was to define characteristics measurable by three-dimensional imaging that would predict complexities both in the implantation procedure and the selection of the appropriate device size. METHODS: An anatomical study was performed of 50 postmortem hearts, of which 15 had a history of atrial fibrillation, and of 30 consecutive patients undergoing LAA occlusion with the Amplatzer cardiac plug (ACP). The specimens were classified according to variables that can be visualized using computerized tomography (CT). The CT scans of 30 consecutive patients were classified according to the level of the LAA ostium, the left lateral ridge (LLR), the LAA limbus and distance from LAA to the mitral annulus before undergoing LAA occlusion, and the results were correlated. RESULTS: Three types of LAA orifice were defined: type I, with a usually higher, anterior LAA ostium, a short, flattened and wide LLR and almost nonexistent limbus; type II, presenting a long, pointed and narrow LLR, and a longer, more defined limbus; type III, with a lower LAA ostium, close to the left atrium floor and the mitral annulus, a marked separation from the left pulmonary vein orifices and a limbus of intermediate length. CONCLUSION: LAA with lower ostia are more difficult to occlude. Types II and III have very prominent LLRs with longer limbi, which may increase the difficulty of inserting the guide and making measurements for selection of the right ACP size.

Total anomalous pulmonary venous connection: outcome of postoperative pulmonary venous obstruction.

OBJECTIVE: Pulmonary venous obstruction (PVO) is an important cause of late mortality in total anomalous pulmonary venous connection (TAPVC). We aimed to describe current practices for the management of postoperative PVO and the efficacy of the different interventional procedures. METHODS: We conducted a retrospective international collaborative population-based study involving 19 pediatric cardiac centers in the United Kingdom, Ireland, and Sweden. Patients with TAPVC born between January 1, 1998, and December 31, 2004, were identified. Patients with functionally univentricular circulation or atrial isomerism were excluded. All available data and images were reviewed. RESULTS: Of 406 patients undergoing repair of TAPVC, 71 (17.5%) had postoperative PVO. The diagnosis was made within 6 months of surgery in 59 (83%) of the 71 patients. In 12, serial imaging documented change in appearance of the pulmonary veins. Good-sized pulmonary veins can progress to diffusely small veins and rarely atresia. Patients presenting after 6 months had less severe disease; all are alive at most recent follow-up. Fifty-six (13.8%) of 406 patients underwent intervention for postoperative PVO: 44 had surgical treatment and 12 had an initial catheter intervention. One half underwent 1 or more reinterventions. Three-year survival for patients with postoperative PVO was 58.7% (95% confidence intervals, 46.2%-69.2%) with a trend that those having a surgical strategy did better (P = .083). Risk factors for death included earlier presentation after TAPVC repair, diffusely small pulmonary veins at presentation of postoperative PVO, and an increased number of lung segments affected by obstruction. CONCLUSIONS: Postoperative PVO tends to appear in the first 6 months after TAPVC repair and can be progressive. Early intervention for PVO may be indicated before irreversible secondary changes occur.

Total anomalous pulmonary venous connection: morphology and outcome from an international population-based study.

BACKGROUND: late mortality after repair of total anomalous pulmonary venous connection is frequently associated with pulmonary venous obstruction (PVO). We aimed to describe the morphological spectrum of total anomalous pulmonary venous connection and identify risk factors for death and postoperative PVO. METHODS AND RESULTS: we conducted a retrospective, international, collaborative, population-based study involving all 19 pediatric cardiac centers in the United Kingdom, Ireland, and Sweden. All infants with total anomalous pulmonary venous connection born between 1998 and 2004 were identified. Cases with functionally univentricular circulations or atrial isomerism were excluded. All available data and imaging were reviewed. Of 422 live-born cases, 205 (48.6%) had supracardiac, 110 (26.1%) had infracardiac, 67 (15.9%) had cardiac, and 37 (8.8%) had mixed connections. There were 2 cases (0.5%) of common pulmonary vein atresia. Some patients had extremely hypoplastic veins or, rarely, discrete stenosis of the individual veins. Sixty (14.2%) had associated cardiac anomalies. Sixteen died before intervention. Three-year survival for surgically treated patients was 85.2% (95% confidence interval 81.3% to 88.4%). Risk factors for death in multivariable analysis comprised earlier age at surgery, hypoplastic/stenotic pulmonary veins, associated complex cardiac lesions, postoperative pulmonary hypertension, and postoperative PVO. Sixty (14.8%) of the 406 patients undergoing total anomalous pulmonary venous connection repair had postoperative PVO that required reintervention. Three-year survival after initial surgery for patients with postoperative PVO was 58.7% (95% confidence interval 46.2% to 69.2%). Risk factors for postoperative PVO comprised preoperative hypoplastic/stenotic pulmonary veins and absence of a common confluence. CONCLUSIONS: preoperative clinical and morphological features are important risk factors for postoperative PVO and survival.

Anatomy of right atrial structures by real-time 3D transesophageal echocardiography.

The rapid development of catheter ablation techniques for atrial arrhythmias has triggered a renewed interest in the anatomy of the right atrium. In particular, some atrial arrhythmias such as focal atrial arrhythmias or atrial flutter have been linked to the anatomic architecture of specific structures such as the crista terminalis or cavotricuspid isthmus. Real-time 3-dimensional transesophageal echocardiography (RT 3D TEE) is a recently developed technique that provides 3D images of unprecedented quality. Because the right atrium is very close to the transducer, this technique may provide high-quality images of those atrial structures involved in ablation procedures. This review describes a step-by-step approach for acquisition and processing of RT 3D TEE images of right atrial structures of relevance to electrophysiologists. For anatomical correlations of RT 3D TEE images, selected images of right atrial structures were matched to anatomical specimens.

Capillary supply to the sinus node in subjects with long-term atrial fibrillation.

BACKGROUND: Atrial ischemia, and sinus node ischemia in particular, may be involved in the pathogenesis of atrial fibrillation. In this study we compared the sinus node blood capillary content in normal hearts in sinus rhythm and in pathologic hearts with chronic atrial fibrillation and we analyzed the ultrastructural features of such capillaries. METHODS: Sinus node biopsy specimens were obtained from 16 patients in chronic atrial fibrillation undergoing open heart surgery. Control sinus node specimens of normal hearts were obtained at autopsy from 7 subjects. Specimens were processed for immunohistochemical, light microscopy and transmission electron microscopy analysis and compared grossly and with morphometric techniques. RESULTS: The proportion of sinus node tissue corresponding to capillaries, defined as blood vessel density (or BVD), was estimated as 1.06 +/- 1.47% for the atrial fibrillation group versus 2.12 +/- 2.0% for controls (p < 0001). Internal capillary diameter averaged 21.6 microm in the atrial fibrillation group and 24.2 microm in controls (p = 0.175), whereas external diameter averaged 32.2 microm in the atrial fibrillation group and 38.9 microm in controls (p = 0.052). Ultrastructural analysis demonstrated scarce and interrupted myoendocardial bridges and abnormal deposits of elastic fibers under the endothelial basal membrane at the level of precapillary sphincters and metaarterioles of atrial fibrillation specimens. CONCLUSIONS: There is a significant reduction in the amount of capillaries in the sinus node of hearts in chronic atrial fibrillation. Our findings would support a potential association between sinus node tissue ischemia and chronic atrial fibrillation.

Prenatal identification of the pulmonary arterial supply in tetralogy of Fallot with pulmonary atresia.

OBJECTIVE: To define the patterns of flow of blood to the lungs in fetuses with tetralogy of Fallot and pulmonary atresia. BACKGROUND: In this condition, supply of blood to the lungs is provided via an arterial duct or systemic-to-pulmonary collateral arteries, or very rarely through other conduits such as coronary arterial fistulas or an aortopulmonary window. The intrapericardial pulmonary arteries vary in size, and may be absent. These variables influence the prognosis and management. METHODS: We carried out a retrospective review of cases from a tertiary service for fetal cardiology, identifying all cases of tetralogy of Fallot with pulmonary atresia diagnosed antenatally between January, 1997, and April, 2006. We established pre- and postnatal outcomes, and compared the prenatal diagnosis with postnatal or autopsy findings. RESULTS: Of 6587 fetuses scanned during this period, 11 were diagnosed as having tetralogy of Fallot with pulmonary atresia and no other cardiac defect. In 5, arterial flow to the lungs was via an arterial duct, and in the other 6, the main identified source of flow was systemic-to-pulmonary collateral arteries. Of the latter 6 pregnancies, 4 were terminated, along with 3 of the 5 with ductal supply. The presence of systemic-to-pulmonary collateral arteries was confirmed at postmortem examination in 3 instances, and in the two delivered neonates, in neither of whom was an infusion of prostaglandin commenced. CONCLUSION: The patterns of pulmonary flow can be identified prenatally in the setting of tetralogy with pulmonary atresia. Supply through systemic-to-pulmonary collateral arteries impacts on counselling, introducing uncertainty regarding postnatal surgical management.

The difficulty in diagnosing idiopathic arterial calcification of infancy, its variation in presentation, and the importance of autopsy.

Idiopathic calcification of the coronary arteries is a rare hereditary condition of infancy. Complications include cardiac ischaemia, cardiac failure, and systemic hypertension. We present three patients with this condition, which in each case masqueraded as other cardiac diseases, with no indication of the specific diagnosis prior to autopsy.A 5 month old female presented with respiratory failure and hypertension and died within 24 hours of admission. All the coronary arteries were thick-walled, with narrow lumens. The aorta, great vessels, and renal arteries also showed thickening of the wall. Histology confirmed calcium in the internal elastic lamina of all vessels. The second patient was a female baby of 2 months, diagnosed with a large ventricular septal defect. She died suddenly prior to surgery. At autopsy, the orifice of the right coronary artery was reduced to a pinhole. The coronary arteries showed white patches of calcification, with associated ventricular infarction. The third patient was an 11 year old female who presented with cardiac failure, and had been diagnosed with dilated cardiomyopathy. Two weeks later, she died suddenly. The coronary arteries were patent, but firm with calcification and narrowed, with associated ventricular infarction. Our experience shows that idiopathic arterial calcification of infancy should always be considered in infants and children presenting with hypertension, cardiac failure, or sudden death.

Aortic root disease in tetralogy of Fallot.

PURPOSE OF REVIEW: Progressive aortic root dilatation is a recognized feature of tetralogy of Fallot even in patients following initial reparative surgery. The underlying pathophysiology was initially attributed to altered hemodynamics resulting from longstanding volume overloading and stretching of the aortic root from increased right to left shunting. This review explores the pathophysiology and possible mechanisms for the aortic dilatation, and whether these changes are a reflection of the initial hemodynamic stress or a cellular expression of an unrecognized gene associated with conotruncal defects. RECENT FINDINGS: The recent publication of two case reports of aortic aneurysm and dissection in tetralogy of Fallot patients re-emphasized the fact that aortic root dilatation can no longer be regarded as a benign problem in tetralogy of Fallot patients. Findings of intrinsic histological abnormalities in the aortic root and ascending aorta of tetralogy of Fallot patients suggest that intrinsic abnormalities may also play an important causative role. SUMMARY: A better understanding of the pathophysiology will help to formulate future treatment and management strategies in the subgroup of tetralogy of Fallot patients with progressive aortic dilatation.

The relationship between structure and function: why does reshaping the left ventricle surgically not always result in functional improvement?

Surgical strategies recently introduced to improve ventricular function have been based on the concepts of reduction of ventricular diameter, synchronization of myocardial activity, passive support of diastolic ventricular shape, and active support of systolic ventricular constriction. They have depended on several established theoretical assumptions, not all of which are totally valid. Clinical results have proved markedly variable. This is especially true for procedures designed to reduce the radius of the left ventricle. Some have reported up to 80% mortality, whereas others achieve results comparable with those for heart transplantation. Because of this, the method runs the risk to be rejected, or else, its more widespread application will be postponed until essential details concerning the basic concepts have been elucidated. It is these details which we discuss in this review.

Basic and clinical electrophysiology of pulmonary vein ectopy.

In a subset of patients, atrial fibrillation is caused by rapidly firing foci that are often located in the pulmonary veins especially when fibrillation is paroxysmal. Histologic data show that myocardial tissue of the left atrial wall extends into the pulmonary venous walls. Both in dog and human pulmonary veins, arrangement of the myofibers is complex. Clinical and animal studies reveal both double potentials and fractionated electrograms in the pulmonary veins, which are related to the complex architecture of the myocardial sleeves in the veins. Such a structure supports the occurrence of reentry. As well, the reduced coupling of cells at sites with abrupt changes in fiber direction could facilitate the escape of a focus and subsequent activation of surrounding tissue. Intracellular recordings made in the pulmonary veins of guinea pig and dog hearts showed that spontaneous activity can occur. Spontaneous action potentials with phase 4 depolarization as well as early after depolarizations were observed in these animal models. In non-spontaneously active preparations, spontaneous activity could be provoked by pharmacologic interventions. The cycle length of bursts of ectopic beats arising in the pulmonary veins of man is often irregular, supporting a focal mechanism of the ectopic beats. The anisotropic characteristics of the myocardial sleeves in the veins may increase the ability of a focus to become evident.

Electrical conduction in canine pulmonary veins: electrophysiological and anatomic correlation.

BACKGROUND: Paroxysmal atrial fibrillation in patients is often initiated by foci in the pulmonary veins. The mechanism of these initiating arrhythmias is unknown. The aim of this study was to determine electrophysiological characteristics of canine pulmonary veins that may predispose to initiating arrhythmias. METHODS AND RESULTS: Extracellular recordings were obtained from the luminal side of 9 pulmonary veins in 6 Langendorff-perfused dog hearts after the veins were incised from the severed end to the ostium. Pulmonary veins were paced at the distal end, the ostium, and an intermediate site. During basic and premature stimulation, extracellular electrical activity was recorded with a grid electrode that harbored 247 electrode terminals. In 4 hearts, intracellular electrograms were recorded with microelectrodes. Myocyte arrangement immediately beneath the venous walls was determined by histological analysis in 3 hearts. Extracellular mapping revealed slow and complex conduction in all pulmonary veins. Activation delay after premature stimulation could be as long as 96 ms over a distance of 3 mm. Action potential duration was shorter at the distal end of the veins than at the orifice. No evidence for automaticity or triggered activity was found. Histological investigation revealed complex arrangements of myocardial fibers that often showed abrupt changes in fiber direction and short fibers arranged in mixed direction. CONCLUSIONS: Zones of activation delay were observed in canine pulmonary veins and correlated with abrupt changes in fascicle orientation. This architecture of muscular sleeves in the pulmonary veins may facilitate reentry and arrhythmias associated with ectopic activity.