Normal and Abnormal Atrial Anatomy Relevant to Atrial Flutters: Areas of Physiological and Acquired Conduction Blocks and Delays Predisposing to Re-entry.

This article reviews the structure of the atrial chambers to consider the anatomic bases for obstacles and barriers in atrial flutter. In particular, the complex myocardial arrangement and composition of the cavotricuspid isthmus could account for a slow zone of conduction. Prominent muscle bundles within the atria and interatrial, and myoarchitecture of the walls, could contribute to preferential conduction pathways. Alterations from tissue damage as part of aging, or from surgical interventions could lead to re-entry.

Anatomy for atrial lead implantation.

Positioning and fixation of pacemaker leads in the right atrium depends on advanced anatomic knowledge in order to correctly interpret information from fluoroscopy and electrograms. Particularly the inability to reach a certain position or to achieve lead stability requires familiarity with right atrial structures such as the Eustachian ridge or areas of trabeculated versus smooth myocardium. Only a good understanding of right atrial anatomy makes it possible to replace electrophysiologically suboptimal atrial pacing sites such as right atrial appendage or high lateral wall by electrophysiologically better septal atrial pacing sites.

Catheter Ablation of the Superolateral Mitral Isthmus Line: A Novel Approach to Reduce the Need for Epicardial Ablation.

BACKGROUND: The mitral isthmus is a critical part of perimitral reentrant tachycardia, as well as an important substrate of persistent atrial fibrillation. Deployment of an endocardial mitral isthmus line (MIL) with the end point of bidirectional block may be challenging and often requires additional epicardial ablation within the coronary sinus. METHODS AND RESULTS: The study population comprised 114 patients with perimitral flutter who underwent de novo ablation of an MIL. The initial 57 patients (group A) underwent catheter ablation using a novel superolateral MIL design, connecting the left-sided pulmonary veins with the mitral annulus along the posterior base of the left atrial appendage visualized by selective angiography. The next 57 patients (group B) served as a control group and underwent ablation using a conventional MIL design, connecting the left inferior pulmonary vein with the mitral annulus. Bidirectional block was achieved in 56 of 57 patients in group A (98.2%) and 50 of 57 patients in group B (87.7%; P=0.06). Deployment of a superolateral MIL required significantly less ablation from within the coronary sinus (7.0% versus 71.9%; P<0.01). Predictors for unsuccessful bidirectional mitral isthmus blockade were the need for epicardial ablation from within the coronary sinus (P<0.01) and the total length of the MIL (29.3±6.35 mm versus 40.8±7.29 mm; P=0.005). A higher rate of pericardial tamponade was observed in group A (5.2% versus 0%; P=0.24). CONCLUSIONS: The superolateral MIL is associated with a high acute success rate to achieve bidirectional block using endocardial ablation only with minimal need for epicardial ablation from within the coronary sinus.

CT and MR imaging of the pulmonary valve.

With rapid advancements in imaging technology, cardiac computed tomography (CT) and magnetic resonance (MR) imaging are increasingly being used for anatomic evaluation, functional assessment, and pathologic diagnosis of the pulmonary valve and right ventricle. MR imaging is especially helpful in evaluating postoperative pulmonary valve function and grading of pulmonary regurgitation. On the other hand, CT has the advantage of high-resolution isovolumetric whole-chest coverage and is able to depict anatomic detail of the pulmonary valve, perivalvular structures, and pulmonary artery branches.

Surgical repair of pulmonary artery branches.

Surgical repair of pulmonary artery (PA) branches encompasses many different clinical scenarios and technical challenges. The most common, such as bifurcation and central PA reconstruction, are described, as well as the challenges of complex and peripheral reconstruction.

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.

Spontaneous rupture of atrioventricular valve tensor apparatus as late manifestation of anti-Ro/SSA antibody-mediated cardiac disease.

Atrioventricular (AV) block and endocardial fibroelastosis associated with dilated cardiomyopathy are the most common clinical manifestations of anti-Ro/SSA-mediated fetal cardiac disease. Valvar dysfunction has not been a prominent feature of this disease; however, recent anecdotal cases have suggested an association between rupture of the AV valve tensor apparatus and maternal anti-Ro/SSA antibodies. In the present study, we have described the clinical and laboratory findings and reviewed the published data for infants of anti-Ro/SSA-positive pregnancies with AV valve insufficiency due to chordal rupture from the papillary muscles. The histopathologic features of the papillary muscle and ventricular free wall and septum biopsy specimens were examined and compared to the sections of AV leaflets from 6 autopsied fetuses with anti-Ro/SSA-mediated complete AV block without chordal disruption. Specific epitopes to the p200 region of Ro52, and Ro60 antibodies were evaluated in cases with chordal rupture. Severe AV valve insufficiency was detected prenatally (as early as 34 weeks of gestation) or postnatally (as late as 182 days) after areas of patchy echogenicity were noted in the papillary muscle at 19 to 22 weeks of gestation. Postnatally, urgent valve surgery was performed in 5 of 6 patients; 1 of 6 patients died preoperatively. All patients tested positive for Ro52. Valve leaflet tissue from the autopsy specimens was normal. The ventricular free wall and septum biopsy specimens from a patient with chordal rupture showed normal tissue; however, the papillary muscle biopsy specimens demonstrated severe atrophy with near total replacement of myocytes by fibrosis and dystrophic calcifications, and negative immunochemistry findings. In conclusion, these findings have defined an underappreciated complication of fetal antibody-mediated cardiac inflammation.

[Anatomy of the atria for rhythmologists]. / Anatomie des oreillettes à l'usage des rythmologues.

The anatomy of the atria is always in the mind of interventional rhythmologists. There is a mental superposition of the anatomical structures and the references obtained by different incidences of fluoroscopy and the endocavitary electrocardiogram. But understanding the anatomy also requires a certain knowledge of dissection to determine, for example, the orientation of bundles of muscle fibres and anatomical sections. The sino-atrial node is situated at a distance from the endocardium. It is long and protected by its own artery which makes it difficult to reach. The atrio-ventricular node has multiple posterior expansions which correspond to the sites where radiofrequency ablation is effective. The cavo-tricuspid isthmus is the target zone for the treatment of atrial flutter but radiofrequency ablation which must be long may be applied at three different levels: inferolateral, median (the most common site) or inferoseptal. Finally, atrial fibrillation has incited many studies of the muscular extensions of the left atrium to the pulmonary veins, the morphological variations of these veins and the organisation of the muscle fibres of the left atrial wall. They have inspired new concepts of atrial fibrillation.

Double-chambered right ventricle or sub-infundibular stenosis assessed by cardiovascular magnetic resonance.

This paper presents magnetic resonance findings in four adults with double-chambered right ventricle or sub-infundibular stenosis, a condition that is treatable by surgery, but which can be difficult to assess echocardiographically. Four patients referred for cardiovascular magnetic resonance in the last 2 years were identified from CMR findings, although not necessarily from previous echocardiography, as having sub-infundibular stenosis. We used multislice spin echo imaging, cine imaging in oblique sagittal planes, and phase velocity mapping. We performed spin echo imaging of a post-mortem heart without known structural abnormality to illustrate right ventricular myocardial morphology. Results in patients showed evidence of sub-infundibular muscular obstruction separating the hypertrophied inlet and apical portions of the right ventricle from a thin-walled, unobstructed infundibular region in each case, with a systolic jet originating at least 15 mm beneath the unstenosed pulmonary valve. In addition to previously described structural components contributing to stenosis--enlargement and/or displacement of the septomarginal trabeculation, septoparietal trabeculations or the moderator band--CMR suggested additional components: a right ventricular papillary muscle in one, an anteriorly bulging aortic sinus in one, and hypertrophied muscular ridges of the parietal wall of the right ventricle. Even in this small group of patients, the causes of sub-infundibular stenosis appeared to be varied and multi-factorial. The abilities of magnetic resonance to give unrestricted, multi-planar views of right ventricular anatomy, movement and flow make it well suited for diagnosis and characterization of sub-infundibular stenosis, especially in adults.

Coronary arterial abnormalities in pulmonary atresia with intact ventricular septum diagnosed during fetal life.

OBJECTIVES: To establish the prevalence of coronary arterial abnormalities in mid-trimester fetuses with pulmonary atresia with intact ventricular septum, and whether their presence correlates with right ventricular morphology. BACKGROUND: The presence of coronary arterial fistulas significantly alters the surgical options and prognosis for patients with pulmonary atresia with intact ventricular septum. The lesion can reliably be diagnosed using fetal echocardiography, and further definition of the prognosis is important for counselling parents. METHODS: We examined the hearts of 39 pathological specimens diagnosed during fetal life, 3 of whom died postnatally. Coronary arterial abnormalities were defined as non-connection of the left or right coronary arteries to the aorta, ostial stenosis, marked tortuosity, dilation, thickening or abnormal myocardial branching. Mild tortuosity, or myocardial bridging, were considered normal. We measured the dimensions of the tricuspid valve along with the inlet and outlet portions of the ventricles. Ebstein's malformation, tricuspid valvar dysplasia, and the presence or absence of the infundibulum, were especially noted. We examined also 12 normal hearts as controls. RESULTS: Coronary arterial abnormalities were found in 14/39 (36%). The dimensions of the right ventricle and tricuspid valves, and the gestational ages of the fetuses, were compared for these 14 with the 25 having no abnormalities using independent t-tests. The gestational ages were similar, 21.9 vs 21.1 weeks. The mean dimensions of the tricuspid valve, median z-scores, and right ventricle were smaller, 2.9 vs 7.2 mm; p < 0.002; -4.46 vs 0.23; p < 0.03; and 6.9 vs 13.7 mm; p < 0.002, for those with coronary arterial abnormalities. Ebstein's malformation, or dysplasia of the tricuspid valve, was present in 4 of 14 with, vs 15 of 25 without, coronary arterial abnormalities. A patent infundibulum was noted in 34 of 39 specimens. CONCLUSIONS: Mid-trimester fetuses with pulmonary atresia with intact ventricular septum already exhibit coronary arterial abnormalities, with a prevalence of 36%. The presence of a patent infundibulum confirms that atresia of the pulmonary valve is an acquired process. Coronary arterial abnormalities are seen in 50% of those with hypoplastic right ventricles, but less frequently in the presence of well developed ventricles. This is important information for those involved in counselling parents.