Anatomic, histologic, and mechanical features of the right atrium: implications for leadless atrial pacemaker implantation.

BACKGROUND: Leadless pacemakers (LPs) may mitigate the risk of lead failure and pocket infection related to conventional transvenous pacemakers. Atrial LPs are currently being investigated. However, the optimal and safest implant site is not known. OBJECTIVES: We aimed to evaluate the right atrial (RA) anatomy and the adjacent structures using complementary analytic models [gross anatomy, cardiac magnetic resonance imaging (MRI), and computer simulation], to identify the optimal safest location to implant an atrial LP human. METHODS AND RESULTS: Wall thickness and anatomic relationships of the RA were studied in 45 formalin-preserved human hearts. In vivo RA anatomy was assessed in 100 cardiac MRI scans. Finally, 3D collision modelling was undertaken assessing for mechanical device interaction. Three potential locations for an atrial LP were identified; the right atrial appendage (RAA) base, apex, and RA lateral wall. The RAA base had a wall thickness of 2.7 ± 1.6 mm, with a low incidence of collision in virtual implants. The anteromedial recess of the RAA apex had a wall thickness of only 1.3 ± 0.4 mm and minimal interaction in the collision modelling. The RA lateral wall thickness was 2.6 ± 0.9 mm but is in close proximity to the phrenic nerve and sinoatrial artery. CONCLUSIONS: Based on anatomical review and 3D modelling, the best compromise for an atrial LP implantation may be the RAA base (low incidence of collision, relatively thick myocardial tissue, and without proximity to relevant epicardial structures); the anteromedial recess of the RAA apex and lateral wall are alternate sites. The mid-RAA, RA/superior vena cava junction, and septum appear to be sub-optimal fixation locations.

Double outlet ventricles: review of anatomic and imaging characteristics.

Hearts with double outlet ventricles and concordant atrioventricular connections account for about 1%-3% of all cases of congenital heart disease. We review hearts with two ventricles and concordant atrioventricular connections with double outlet right ventricle (DORV), double outlet left ventricle (DOLV) and double outlet both ventricles (DOBV) from the morphological and clinical imaging perspectives. These hearts are a heterogeneous group of congenital cardiac malformations with a wide range of pathophysiologies that require an individualised surgical approach based on a precise understanding of the complex cardiovascular anatomy. Owing to their differing temporal, spatial and contrast resolutions, we propose that multimodality imaging provides optimal characterisation of various intracardiac morphological features of double outlet hearts. This approach aids clinical diagnosis for optimising treatment options across these malformations.

Development of a cardiovascular magnetic resonance-compatible large animal isolated heart model for direct comparison of beating and arrested hearts.

Cardiac motion results in image artefacts and quantification errors in many cardiovascular magnetic resonance (CMR) techniques, including microstructural assessment using diffusion tensor cardiovascular magnetic resonance (DT-CMR). Here, we develop a CMR-compatible isolated perfused porcine heart model that allows comparison of data obtained in beating and arrested states. Ten porcine hearts (8/10 for protocol optimisation) were harvested using a donor heart retrieval protocol and transported to the remote CMR facility. Langendorff perfusion in a 3D-printed chamber and perfusion circuit re-established contraction. Hearts were imaged using cine, parametric mapping and STEAM DT-CMR at cardiac phases with the minimum and maximum wall thickness. High potassium and lithium perfusates were then used to arrest the heart in a slack and contracted state, respectively. Imaging was repeated in both arrested states. After imaging, tissue was removed for subsequent histology in a location matched to the DT-CMR data using fiducial markers. Regular sustained contraction was successfully established in six out of 10 hearts, including the final five hearts. Imaging was performed in four hearts and one underwent the full protocol, including colocalised histology. The image quality was good and there was good agreement between DT-CMR data in equivalent beating and arrested states. Despite the use of autologous blood and dextran within the perfusate, T2 mapping results, DT-CMR measures and an increase in mass were consistent with development of myocardial oedema, resulting in failure to achieve a true diastolic-like state. A contiguous stack of 313 5-µm histological sections at and a 100-µm thick section showing cell morphology on 3D fluorescent confocal microscopy colocalised to DT-CMR data were obtained. A CMR-compatible isolated perfused beating heart setup for large animal hearts allows direct comparisons of beating and arrested heart data with subsequent colocalised histology, without the need for onsite preclinical facilities.

Predicting Survival in Repaired Tetralogy of Fallot: A Lesion-Specific and Personalized Approach.

OBJECTIVES: This study sought to identify patients with repaired tetralogy of Fallot (rTOF) at high risk of death and malignant ventricular arrhythmia (VA). BACKGROUND: To date there is no robust risk stratification scheme to predict outcomes in adults with rTOF. METHODS: Consecutive patients were prospectively recruited for late gadolinium enhancement (LGE) cardiovascular magnetic resonance (CMR) to define right and left ventricular (RV, LV) fibrosis in addition to proven risk markers. RESULTS: The primary endpoint was all-cause mortality. Of the 550 patients (median age 32 years, 56% male), 27 died (mean follow-up 6.4 ± 5.8; total 3,512 years). Mortality was independently predicted by RVLGE extent, presence of LVLGE, RV ejection fraction ≤47%, LV ejection fraction ≤55%, B-type natriuretic peptide ≥127 ng/L, peak exercise oxygen uptake (V02) ≤17 mL/kg/min, prior sustained atrial arrhythmia, and age ≥50 years. The weighted scores for each of the preceding independent predictors differentiated a high-risk subgroup of patients with a 4.4%, annual risk of mortality (area under the curve [AUC]: 0.87; P < 0.001). The secondary endpoint (VA), a composite of life-threatening sustained ventricular tachycardia/resuscitated ventricular fibrillation/sudden cardiac death occurred in 29. Weighted scores that included several predictors of mortality and RV outflow tract akinetic length ≥55 mm and RV systolic pressure ≥47 mm Hg identified high-risk patients with a 3.7% annual risk of VA (AUC: 0.79; P < 0.001) RVLGE was heavily weighted in both risk scores caused by its strong relative prognostic value. CONCLUSIONS: We present a score integrating multiple appropriately weighted risk factors to identify the subgroup of patients with rTOF who are at high annual risk of death who may benefit from targeted therapy.

Three-Dimensional Late Gadolinium Enhancement Cardiovascular Magnetic Resonance Predicts Inducibility of Ventricular Tachycardia in Adults With Repaired Tetralogy of Fallot.

BACKGROUND: Adults with repaired tetralogy of Fallot die prematurely from ventricular tachycardia (VT) and sudden cardiac death. Inducible VT predicts mortality. Ventricular scar, the key substrate for VT, can be noninvasively defined with late gadolinium enhancement (LGE) cardiovascular magnetic resonance but whether this relates to inducible VT is unknown. METHODS: Sixty-nine consecutive repaired tetralogy of Fallot patients (43 male, mean 40±15 years) clinically scheduled for invasive programmed VT-stimulation were prospectively recruited for prior 3-dimensional LGE cardiovascular magnetic resonance. Ventricular LGE was segmented and merged with reconstructed cardiac chambers and LGE volume measured. RESULTS: VT was induced in 22 (31%) patients. Univariable predictors of inducible VT included increased RV LGE (odds ratio [OR], 1.15; P=0.001 per cm3), increased nonapical vent LV LGE (OR, 1.09; P=0.008 per cm3), older age (OR, 1.6; P=0.01 per decile), QRS duration ≥180 ms (OR, 3.5; P=0.02), history of nonsustained VT (OR, 3.5; P=0.02), and previous clinical sustained VT (OR, 12.8; P=0.003); only prior sustained VT (OR, 8.02; P=0.02) remained independent in bivariable analyses after controlling for RV LGE volume (OR, 1.14; P=0.003). An RV LGE volume of 25 cm3 had 72% sensitivity and 81% specificity for predicting inducible VT (area under the curve, 0.81; P<0.001). At the extreme cutoffs for ruling-out and ruling-in inducible VT, RV LGE >10 cm3 was 100% sensitive and >36 cm3 was 100% specific for predicting inducible VT. CONCLUSIONS: Three-dimensional LGE cardiovascular magnetic resonance-defined scar burden is independently associated with inducible VT and may help refine patient selection for programmed VT-stimulation when applied to an at least intermediate clinical risk cohort.

The morphologically right and left ventricles cannot be distinguished by their coronary arterial pattern.

OBJECTIVES: The morphologically right and left ventricles are distinguished from each other based on their internal anatomical features, because their external (epicardial) surfaces do not appear to have any distinguishing mark for such ventricular identification. Nevertheless, ventricular identification based on epicardial characteristics, if these were possible, would be interesting to surgeons, because this would enable them to identify each ventricle rapidly upon opening the chest. This made us curious as to whether or not the two ventricles may be distinguished based on their epicardial coronary arterial patterns, because this is the most obvious epicardial ventricular feature. METHODS: This idea led us to formulate the following 2 hypotheses: (i) The morphologically left ventricle is always the one that receives the higher number of the marginal arteries as compared to the morphologically right ventricle. (ii) Only the morphologically left ventricle receives the diagonal arteries from the anterior and posterior interventricular arteries. These hypotheses were tested in this anatomical observational study by examination of 98 normal and 398 congenitally malformed formaldehyde-preserved hearts encompassing most malformations, including rare ones and hearts in which 1 ventricle is hypoplastic. RESULTS: These examinations show that both hypotheses are false. CONCLUSIONS: The two ventricles cannot be distinguished from each other based on the number of marginal arteries that they receive or which one receives diagonal arteries; both ventricles may receive diagonal arteries from either or both interventricular arteries.

Anatomy of the atrial septum and interatrial communications.

Deficiencies in the septum separating the two atrial chambers are among the most common of congenital heart malformations. This article reviews the developmental aspects of the partitioning of the primitive atrium into right and left atrial chambers, the anatomical components of the atrial septum, and deficiencies that produce the various types of interatrial communications. Knowledge of the components of the true atrial septum in the developed heart clarifies the morphology of various types of interatrial communications. The oval fossa defect (also termed secundum ASD) is located within the true septum. The patent foramen ovale (PFO) is a tunnel-like passageway between the free edge of the overlapping ovale fossa valve and its muscular rim. Other defects such as superior and inferior sinus venosus defects, coronary sinus defects, and ostium primum defects lie outside the area of the true septum.

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.

Immediate and Midterm Cardiac Remodeling After Surgical Pulmonary Valve Replacement in Adults With Repaired Tetralogy of Fallot: A Prospective Cardiovascular Magnetic Resonance and Clinical Study.

BACKGROUND: Pulmonary valve replacement (PVR) in patients with repaired tetralogy of Fallot provides symptomatic benefit and right ventricular (RV) volume reduction. However, data on the rate of ventricular structural and functional adaptation are scarce. We aimed to assess immediate and midterm post-PVR changes and predictors of reverse remoeling. METHODS: Fifty-seven patients with repaired tetralogy of Fallot (age ≥16 y; mean age, 35.8±10.1 y; 38 male) undergoing PVR were prospectively recruited for cardiovascular magnetic resonance performed before PVR (pPVR), immediately after PVR (median, 6 d), and midterm after PVR (mPVR; median, 3 y). RESULTS: There were immediate and midterm reductions in indexed RV end-diastolic volumes and RV end-systolic volumes (RVESVi) (indexed RV end-diastolic volume pPVR versus immediately after PVR versus mPVR, 156.1±41.9 versus 104.9±28.4 versus 104.2±34.4 mL/m2; RVESVi pPVR versus immediately after PVR versus mPVR, 74.9±26.2 versus 57.4±22.7 versus 50.5±21.7 mL/m2; P<0.01). Normal postoperative diastolic and systolic RV volumes (the primary end point) achieved in 70% of patients were predicted by a preoperative indexed RV end-diastolic volume ≤158 mL/m2 and RVESVi ≤82 mL/m2. RVESVi showed a progressive decrease from baseline to immediate to midterm follow-up, indicating ongoing intrinsic RV functional improvement after PVR. Left ventricular ejection fraction improved (pPVR versus mPVR, 59.4±7.6% versus 61.9±6.8%; P<0.01), and right atrial reverse remodeling occurred (pPVR versus mPVR, 15.2±3.4 versus 13.8±3.6 cm2/m2; P<0.01). Larger preoperative RV outflow tract scar was associated with a smaller improvement in post-PVR RV/left ventricular ejection fraction. RV ejection fraction and peak oxygen uptake predicted mortality (P=0.03) over a median of 9.5 years of follow-up. CONCLUSIONS: Significant right heart structural reverse remodeling takes place immediately after PVR, followed by a continuing process of further biological remodeling manifested by further reduction in RVESVi. PVR before RVESVi reaches 82 mL/m2 confers optimal chances of normalization of RV function.

Distinct genetic architectures for syndromic and nonsyndromic congenital heart defects identified by exome sequencing.

Congenital heart defects (CHDs) have a neonatal incidence of 0.8-1% (refs. 1,2). Despite abundant examples of monogenic CHD in humans and mice, CHD has a low absolute sibling recurrence risk (∼2.7%), suggesting a considerable role for de novo mutations (DNMs) and/or incomplete penetrance. De novo protein-truncating variants (PTVs) have been shown to be enriched among the 10% of 'syndromic' patients with extra-cardiac manifestations. We exome sequenced 1,891 probands, including both syndromic CHD (S-CHD, n = 610) and nonsyndromic CHD (NS-CHD, n = 1,281). In S-CHD, we confirmed a significant enrichment of de novo PTVs but not inherited PTVs in known CHD-associated genes, consistent with recent findings. Conversely, in NS-CHD we observed significant enrichment of PTVs inherited from unaffected parents in CHD-associated genes. We identified three genome-wide significant S-CHD disorders caused by DNMs in CHD4, CDK13 and PRKD1. Our study finds evidence for distinct genetic architectures underlying the low sibling recurrence risk in S-CHD and NS-CHD.

Systemic right ventricular fibrosis detected by cardiovascular magnetic resonance is associated with clinical outcome, mainly new-onset atrial arrhythmia, in patients after atrial redirection surgery for transposition of the great arteries.

BACKGROUND: We hypothesized that fibrosis detected by late gadolinium enhancement (LGE) cardiovascular magnetic resonance predicts outcomes in patients with transposition of the great arteries post atrial redirection surgery. These patients have a systemic right ventricle (RV) and are at risk of arrhythmia, premature RV failure, and sudden death. METHODS AND RESULTS: Fifty-five patients (aged 27±7 years) underwent LGE cardiovascular magnetic resonance and were followed for a median 7.8 (interquartile range, 3.8-9.6) years in a prospective single-center cohort study. RV LGE was present in 31 (56%) patients. The prespecified composite clinical end point comprised new-onset sustained tachyarrhythmia (atrial/ventricular) or decompensated heart failure admission/transplantation/death. Univariate predictors of the composite end point (n=22 patients; 19 atrial/2 ventricular tachyarrhythmia, 1 death) included RV LGE presence and extent, RV volumes/mass/ejection fraction, right atrial area, peak Vo(2), and age at repair. In bivariate analysis, RV LGE presence was independently associated with the composite end point (hazard ratio, 4.95 [95% confidence interval, 1.60-15.28]; P=0.005), and only percent predicted peak Vo(2) remained significantly associated with cardiac events after controlling for RV LGE (hazard ratio, 0.80 [95% confidence interval, 0.68-0.95]; P=0.009/5%). In 8 of 9 patients with >1 event, atrial tachyarrhythmia, itself a known risk factor for mortality, occurred first. There was agreement between location and extent of RV LGE at in vivo cardiovascular magnetic resonance and histologically documented focal RV fibrosis in an explanted heart. There was RV LGE progression in a different case restudied for clinical indications. CONCLUSIONS: Systemic RV LGE is strongly associated with adverse clinical outcome especially arrhythmia in transposition of the great arteries, thus LGE cardiovascular magnetic resonance should be incorporated in risk stratification of these patients.

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.

Substrates of atrial arrhythmias: histological insights from patients with congenital heart disease.

BACKGROUND: The impact of overload duration and age on remodelling process in human atria remains controversial. We analysed histological markers of right atrial (RA) remodelling in CHD patients in order to provide some insights into impacts of age and overload duration on substrates of atrial arrhythmias. METHODS: Sixty-five CHD patients who underwent initial cardiac surgery were enrolled (median age 18 years). Patients with dominant left atrial overload were excluded. RA tissues resected from CHD patients during surgery were examined by means of histology and immunohistochemistry and compared with RA tissues from age-matched control hearts from post-mortem (n=22, median age 22 years). Patient histories of preoperative SVTs and echocardiography were also examined. RESULTS: The greatest extent of fibrosis, the largest myocyte diameter and the longest capillary distance and the most CD45-positive cell infiltration was observed in CHD samples with SVT, followed by CHD without SVT and then control samples. All histological changes were correlated with age in CHD samples (r=0.462, 0.718, 0.529 and 0.447, respectively) with relatively steep and continuous manner, whereas only myocyte diameter was correlated with age in control samples (r=0.576). RA dimensions and area obtained from echocardiography also correlated with histological markers in CHD patients. CONCLUSIONS: Dominant and chronic RA overload due to CHD resulted in time-course related RA structural remodelling, which could provide the background for atrial arrhythmia. The overload duration, rather than age, seems to be a key factor for atrial histological degeneration in the cohort of CHD.

Histopathology of the great vessels in patients with pulmonary arterial hypertension in association with congenital heart disease: large pulmonary arteries matter too.

BACKGROUND: Pulmonary arterial hypertension (PAH) is considered primarily a disease of the distal pulmonary arteries whereas little is known on the effect of long-standing pulmonary hypertension on the larger proximal pulmonary arteries. This study aims to investigate the structural changes in the great arteries of adults who developed PAH in association with congenital heart disease (CHD), with severe cases termed Eisenmenger syndrome. METHODS: We performed macroscopic and light microscopy analyses on the great arteries of 10 formalin-fixed human hearts from patients with PAH/CHD and compared them to age-matched healthy controls. A detailed histology grading score was used to assess the severity of medial wall abnormalities. RESULTS: Severe atherosclerotic lesions were found macroscopically in the elastic pulmonary arteries of 4 PAH/CHD specimens and organised thrombi in 3; none were present in the controls. Significant medial wall abnormalities were present in the pulmonary trunk (PT), including fibrosis (80%), and atypical elastic pattern (80%). Cyst-like formations were present in less than one third of patients and were severe in a single case leading to wall rupture. The cumulative PT histology grading score was significantly higher in PAH/CHD cases compared to controls (p<0.0001) and correlated positively with larger PT diameters (ρ=0.812, p<0.0001) and the degree of medial wall hypertrophy (ρ=0.749, p<0.0001). CONCLUSIONS: Chronic PAH in association with CHD results in marked macroscopic and histological abnormalities in the large pulmonary arteries. These abnormalities are likely to affect haemodynamics and contribute to morbidity and mortality in this cohort.

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.

Right atrial appendage and vestibule: further anatomical insights with implications for invasive electrophysiology.

AIMS: Despite recognition that understanding gross anatomy of the right atrium is important in the era of invasive electrophysiology, areas such as the right atrial appendage (RAA) wall or the vestibule are not fully appreciated. The aim of this study was to conduct an anatomical assessment focusing on these structures to gain further insights into electrophysiological procedures. METHODS: Forty-four normal human hearts were examined macro- and microscopically. RESULTS: Inside the RAA, two prominent muscle bundles; the crista terminalis (CT) and the sagittal bundle (SB) were identified. The medial wall at which the CT originated from and its surrounding area was the thickest part adjacent anteriorly to the thin aortic mound, suggesting non-uniform wall thickness of this area. Histological sections revealed that myocardial strands of the SB connected the CT and RAA tip, implying preferential anterior conduction of the sinus impulse. The vestibule had a thin myocardium with extensive fat covering along the epicardial side of the tricuspid annulus. The proximal portion of the right coronary artery (RCA) was relatively distant from the annulus, followed by gradual shortening of the distance from the endocardium to the RCA, which led to a very close relationship (<3.0 mm) at the inferior annulus. CONCLUSION: Non-uniform wall thickness and muscle fibre orientation in the RAA should be taken into consideration during lead/catheter positioning. The RCA proximity in the inferior portion of the vestibule and the deeper fatty plane of the anterior atrioventricular groove are important anatomical features relevant to accessory pathway ablation.

Reproducibility of in-vivo diffusion tensor cardiovascular magnetic resonance in hypertrophic cardiomyopathy.

BACKGROUND: Myocardial disarray is an important histological feature of hypertrophic cardiomyopathy (HCM) which has been studied post-mortem, but its in-vivo prevalence and extent is unknown. Cardiac Diffusion Tensor Imaging (cDTI) provides information on mean intravoxel myocyte orientation and potentially myocardial disarray. Recent technical advances have improved in-vivo cDTI, and the aim of this study was to assess the interstudy reproducibility of quantitative in-vivo cDTI in patients with HCM. METHODS AND RESULTS: A stimulated-echo single-shot-EPI sequence with zonal excitation and parallel imaging was implemented. Ten patients with HCM were each scanned on 2 different days. For each scan 3 short axis mid-ventricular slices were acquired with cDTI at end systole. Fractional anisotropy (FA), mean diffusivity (MD), and helix angle (HA) maps were created using a cDTI post-processing platform developed in-house. The mean ± SD global FA was 0.613 ± 0.044, MD was 0.750 ± 0.154 × 10-3 mm2/s and HA was epicardium -34.3 ± 7.6°, mesocardium 3.5 ± 6.9° and endocardium 38.9 ± 8.1°. Comparison of initial and repeat studies showed global interstudy reproducibility for FA (SD = ± 0.045, Coefficient of Variation (CoV) = 7.2%), MD (SD = ± 0.135 × 10-3 mm2/s, CoV = 18.6%) and HA (epicardium SD = ± 4.8°; mesocardium SD = ± 3.4°; endocardium SD = ± 2.9°). Reproducibility of FA was superior to MD (p = 0.003). MD was significantly higher in the septum than the reference lateral wall (0.784 ±0.188 vs 0.714 ±0.155 ×10-3 mm2/s, p <0.001) [corrected]. Septal HA was significantly lower than the reference lateral wall in all 3 transmural layers (from -8.3° to -10.4°, all p < 0.001). CONCLUSIONS: To the best of our knowledge, this is the first study to assess the interstudy reproducibility of DTI in the human HCM heart in-vivo and the largest cDTI study in HCM to date. Our results show good reproducibility of FA, MD and HA which indicates that current technology yields robust in-vivo measurements that have potential clinical value. The interpretation of regional differences in the septum requires further investigation.

Anatomic assessment of variations in myocardial approaches to the atrioventricular node.

INTRODUCTION: The tissues in the posteroinferior atrioventricular (AV) junction around the AV node are important in procedures for ablating and manipulation of catheters in and around the coronary sinus (CS). However, information with regard to the histological arrangement of perinodal myocardium relative to the CS is lacking. METHODS AND RESULTS: We examined 21 postmortem human hearts without any abnormalities (9 women; mean age 68.8 ± 14.3 years). After making measurements, the posteroinferior AV junction was removed and processed for histology. Sections were cut parallel to the septum. We assessed the myocardial arrangements from the atrial septum and the CS toward the AV nodal tissue, including the transitional cell zone, and measured the dimensions between the compact AV node and the CS, and the circumference of the CS. We observed 3 patterns of myocardial approaches to the AV node: extension of myocardium from the atrial septum (Group A; n = 6); extension of CS musculature (Group B; n = 6); and both septal and CS musculature (Group C; n = 9). The distance between the AV node and the CS in Group A was significantly longer than in the other groups (mean 11.5 ± 3.1 mm, 1.7 ± 0.6 mm, 3.8 ± 1.5 mm, respectively; P < 0.0001), and the circumference of the CS in Group B was longer than in Group A (mean 31.1 ± 7.9 mm*, 44.4 ± 8.4 mm*, 33.7 ± 6.9 mm, respectively; P < 0.05). CONCLUSION: The myocardial approaches including the transitional cell zone toward the AV node are variable in normal hearts. The location and size of the CS can affect the myocardial arrangements and the area of transitional cells around the AV node.