The rapid development of interventional procedures for the treatment of arrhythmias in humans, especially the use of catheter ablation techniques, has renewed interest in cardiac anatomy. Although the substrates of atrial fibrillation (AF), its initiation and maintenance, remain to be fully elucidated, catheter ablation in the left atrium (LA) has become a common therapeutic option for patients with this arrhythmia. Using ablation catheters, various isolation lines and focal targets are created, the majority of which are based on gross anatomical, electroanatomical, and myoarchitectual patterns of the left atrial wall. Our aim was therefore to review the gross morphological and architectural features of the LA and their relations to extracardiac structures. The latter have also become relevant because extracardiac complications of AF ablation can occur, due to injuries to the phrenic and vagal plexus nerves, adjacent coronary arteries, or the esophageal wall causing devastating consequences.

The establishment of radiofrequency catheter ablation techniques as the mainstay in the treatment of tachycardia has renewed new interest in cardiac anatomy. The interventional arrhythmologist has drawn attention not only to the gross anatomic details of the heart but also to architectural and histological characteristics of various cardiac regions that are relevant to the development or recurrence of tachyarrhythmias and procedural related complications of catheter ablation. In this review, therefore, we discuss some anatomic landmarks commonly used in catheter ablations including the terminal crest, sinus node region, Koch’s triangle, cavotricuspid isthmus, Eustachian ridge and valve, pulmonary venous orifices, venoatrial junctions, and ventricular outflow tracts. We also discuss the anatomical features of important structures in the vicinity of the atria and pulmonary veins, such as the esophagus and phrenic nerves. This paper provides basic anatomic information to improve understanding of the mapping and ablative procedures for cardiac interventional electrophysiologists.

Aims: Seeking to account for accessory atrioventricular conduction potentially leading to ventricular pre-excitation, Mahaim in the mid-20th century had described pathways between the atrioventricular conduction axis and the muscular ventricular septum. We aimed to look for such ‘paraspecific’ connections in adult human hearts. Methods and results: We serially sectioned 21 hearts, covering the triangle of Koch and the aortic root, and assessing the atrioventricular node, the penetration of the conduction axis, and the bundle branches in our search for fasciculo-ventricular connections. We also calculated the length of the non-branching bundle, and if present the origin of the fasciculo-ventricular connections. The non-branching bundle was 3.6 ± 1.7 mmin length, varying from 1.7 mm to 7.2 mm. Fasciculo-ventricular connections were found in more than half of the hearts, making direct contact with the muscular septum at an average of 3.5 ± 1.7 mm from the origin of the left bundle branch, with the site of origin varying from 1.1 mm to 5.5 mm from the first fascicle of the left bundle branch. In three hearts, additional fasciculo-fascicular connections were observed in the left bundle branch. Two loops were small, but one loop extended over 9.5 mm. Conclusion: We endorse the finding of Mahaim that fasciculo-ventricular pathways exist in most human hearts. We presume the identified connections had the capability of producing ventricular pre-excitation. More studies are needed to determine the potential clinical manifestations.

Introduction: Several reports suggest a possible association between polymorphisms in the cytochrome P450 2C9 (CYP2C9) gene and the risk for non-steroidal anti-inflammatory drug (NSAID)-related adverse gastrointestinal events, including gastrointestinal bleeding. Because findings were controversial, a systematic review and a meta-analysis of eligible studies on this putative association was conducted. Areas covered: The authors have revised the relationship between CYP2C9 polymorphisms and the risk of developing NSAID-related gastrointestinal bleeding, as well as other adverse gastrointestinal events, and performed meta-analyses. The bias effect and potential sources of heterogeneity between studies was analysed. Expert opinion: Individuals classified as poor metabolizers after CYP2C9 genotyping (activity scores equal to 0 or 0.5) have an increased risk of developing NSAID-related gastrointestinal adverse events with an odds ratio (OR) = 1.86, (p = 0.004) and the OR for subjects with gastrointestinal bleeding is = 1.90, (p = 0.003). Gene-dose effect for variant CYP2C9 alleles (p = 0.005 for all gastrointestinal adverse events, and p = 0.0001 for bleeding patients) was observed. Also, there is an allele-specific effect in the association: CYP2C9*2 is a poor risk predictor, whereas CYP2C9*3 is a highly significant predictor of gastrointestinal adverse events (p = 0.006) and gastrointestinal bleeding (p = 0.0007).