Description of the aortic root anatomy in relation to transcatheter aortic valve implantation.

INTRODUCTION: Transcatheter aortic valve implantation (TAVI) has emerged as a less invasive treatment than surgical aortic valve replacement in patients with aortic stenosis. Understanding the anatomy of aortic valve complex may help in optimal positioning of prosthetic valve and circumvent complications that can arise during its implantation. MATERIAL AND METHODS: The anatomy of aortic root was studied in 30 formalin-fixed cadavers. Aortic root and left ventricular cavity was opened to measure the diameter at the base of aortic root and sinotubular junction (STJ); distance of coronary ostia from base of aortic root and STJ; height and width of aortic valve leaflets; length and thickness of membranous septum (MS). RESULTS: The diameter of aorta at the base of aortic root and STJ was 22.4±2.1 mm and 21.8±2.4 mm, respectively. The height of aortic leaflets was smaller than the width. The right and left coronary ostia were 10.7±1.9 mm and 10.5±1.9 mm above the base of aortic root. Membranous septum was 4.7±1.23 mm (range 2.9-6.1 mm) long and formed part of the wall of aortic root in 40% (12/30) cases. CONCLUSIONS: Low lying coronary ostia speculate the use of a small prosthesis size to avoid or reduce the degree of coronary compression. Length of MS may help in deciding the extent of devise penetration into left ventricular outflow tract to avoid conduction block. Membranous septum forming wall of aortic root increases the risk of aortic root rupture and iatrogenic membranous defect during TAVI.

Histological topography of the atrioventricular node and its extensions in relation to the cardiothoracic surgical landmarks in normal human hearts.

BACKGROUND: Atrioventricular (AV) nodal injury which results in cardiac conduction disorders is one of the potential complications of heart valve surgeries and radiofrequency catheter ablations. Understanding the topography of the AV conduction system in relation to the tricuspid and mitral valves will help in reducing these complications. METHODS: A tissue block of 3cmx4cm, which contain the AV node, bundle of His and the AV nodal extensions, was excised at the AV septal junction in 20 apparently normal human hearts. The block was divided into three equal segments through vertical incisions perpendicular to the insertion of the septal leaflet of the tricuspid valve. Each segment was processed and stained with H&E and Gomori to study the different parts of the AV conduction system. RESULTS: The lower pole of the AV node was located vertically above the tricuspid septal leaflet (TSL) in 100% (20/20) of cases and at the level of the muscular interventricular septum in 65% (13/20) of cases. The upper pole of the compact AV node was located at the level of the mitral valve leaflet (MVL) in 50% (10/20) of cases. The penetrating bundle of His was seen at the level of the TSL, while the branching bundle of His was situated 1.9±1.5 mm inferior to the TSL. The right and left posterior extensions of the AV node spanned from the MVL to 2.9±1.3 mm above the TSL. CONCLUSIONS: A rectangular area (2.5 mm × 12 mm) in the Koch's triangle was devoid of AV nodal tissue and could be labeled as a safe area with no risk of conduction defects during valve surgeries. Information on the separation of AV nodal extensions from the TSL, MVL and muscular interventricular septum may play a crucial role in guiding and improving the safety of radiofrequency ablations.

Variant origin and course of left circumflex coronary artery.

Variant origin of left circumflex coronary artery (LCx) from right aortic sinus is a well-recognized coronary variation, usually without any clinical consequences. However, the variant origin and trajectory of the artery may have major implications during percutaneous coronary intervention, coronary artery surgery, aortic and mitral valve replacement procedures. We observed a variant LCx in a heart specimen belonging to 45-year-female with no history of hypertension, diabetes mellitus and coronary artery disease. The artery arose along with the right coronary artery from a common ostium in right aortic sinus and depicted a retroaortic course. The vessel was located at the level of aortic annulus and 6.6 mm above mitral valve annulus. The degree of luminal stenosis in variant LCx was higher than that in right coronary artery (RCA) and left anterior descending artery (LAD). Appropriate anatomical knowledge of the location and course of variant LCx is important for successful coronary interventions and valve replacement procedures.

Spatial relationship of coronary sinus-great cardiac vein to mitral valve annulus and left circumflex coronary artery: implications for cardiovascular interventional procedures.

BACKGROUND: The spatial relationship of the coronary sinus-great cardiac vein (CS-GCV) to free posterior portion of the mitral valve annulus (MVA) and left circumflex coronary artery (LCx) has gained importance with the advent of cardiovascular interventional procedures such as percutaneous transvenous mitral annuloplasty (PTMA) and mitral isthmus (MI) ablation. METHODS: In 50 normal (nondilated cardiomyopathy, or non-DCM) and 20 dilated cardiomyopathy (DCM) cadaveric hearts, the diameter and distance from the MVA of CS-GCV and its spatial relationship to LCx along the free posterior portion of the MVA were studied. RESULTS: The diameter of the CS-GCV increased from the beginning to termination in both non-DCM and DCM cases. The CS-GCV was located farthest from the MVA in the vertical plane in the middle of its course and in the horizontal plane at its beginning. The LCx was located above the CS-GCV in direct contact with the epicardial aspect of MI in 12% non-DCM and 15% DCM cases and was wedged between the CS-GCV and MI in 20% non-DCM and 15% DCM cases. CONCLUSIONS: Knowledge of the separation between the CS-GCV and MVA in the horizontal and vertical planes could help in selecting suitable candidates and the preprocedural prediction of success of PTMA. Awareness of the spatial relationship of LCx with CS-GCV in MI would help to reduce the risk of incomplete MI block due to a heat sink effect or damage to the LCx by direct thermal injury during MI ablation.

Spatial relationship of coronary sinus-great cardiac vein with adjoining anatomic structures: a key element in predicting the success of percutaneous transvenous mitral annuloplasty.

BACKGROUND AND AIM OF THE STUDY: Knowledge of the anatomy of the coronary venous system and its relationship with the mitral valve annulus (MVA) and coronary arteries is a key element to successful percutaneous transvenous mitral annuloplasty (PTMA) device implantation for treating patients with severe mitral regurgitation. METHODS: The spatial relationship of the coronary sinus-great cardiac vein (CS-GCV) with the MVA, left circumflex coronary artery (LCx) and its branches was examined in 120 formalin-fixed adult human cadaveric hearts. RESULTS: During the initial part of its journey, the CS-GCV was seen to course along and parallel to the plane of the MVA in 109 cases (90.8%), and to cross the MVA obliquely in 11 cases (9.2%). The LCx crossed deep or superficial to the CS-GCV at a discrete point in 98 cases (81.6%) and in eight cases (6.6%), respectively. In two cases (1.6%), the LCx was overlapped by the CS-GCV for an average length of 3.5 +/- 0.7 cm, and in five cases (4.1%) it lay superficial to the CS-GCV for an average length of 3.1 +/- 1.0 cm. In the remaining seven cases (5.8%), the artery did not accompany the CS-GCV along the MVA. Obtuse marginal arteries and the ramus intermedius were seen coursing deep to the CS-GCV in 40 cases (33.3%) and 33 cases (27.5%), respectively. CONCLUSION: The study results showed that the CS-GCV crosses the annulus obliquely in 9.2% of cases, and hence might affect the efficiency of PTMA. Similarly, positioning of the annuloplasty device in the CS-GCV in cases where the LCx and its branches lay deep to the vein may result in an impingement of the arteries, leading to ischemia.

Study of spatial relationship of phrenic nerves with cardiac structures relevant to electrophysiologic interventions.

BACKGROUND: Pulmonary vein (PV) isolation with catheter ablation in treating atrial fibrillation carries the risk of injury to phrenic nerve (PN). Left PN (LPN) stimulation continues to be one of the common complications of transvenous left ventricular lead placement during cardiac resynchronization therapy (CRT). METHODS AND RESULTS: In 30 formalin-fixed cadavers, spatial relationship of PNs with PV ostia, left atrial appendage (LAA), and cardiac veins was observed. Segmental location of LPN and cardiac vein crossover was also noted. Right and left PNs coursed abutting the ostium of right superior and left superior PVs in five (16.6%) and one (3.33%) cases, respectively. LPN coursed along the lateral surface of LAA in 20 (66.66%) cases and behind LAA in one (3.33%) case. Out of 18 (60%) cases having two cardiac veins draining free wall of left ventricle (LV) and suitable for CRT lead placement, both cardiac veins were crossed by LPN in two (6.66%) cases. LPN-cardiac vein crossover was located in midlateral segment in 10 (33.3%) cases; mid posterolateral segment in five (16.7%) cases; apical lateral segment and apical posterolateral segment in three (10.0%) cases each. CONCLUSION: PN is highly susceptible to either injury during catheter ablation or stimulation with LV pacing in certain critical locations. Detailed knowledge of spatial relationship of PNs with cardiac structures could help minimize inadvertent complications during these transcatheter electrophysiological procedures.

Variance in coronary venous anatomy: a critical determinant in optimal candidate selection for cardiac resynchronization therapy.

BACKGROUND: Knowledge of coronary sinus (CS) anatomy and its variations is one of the important factors determining the final position of left ventricle pacing lead during cardiac resynchronization therapy. METHODS: Coronary venous system anatomy, including number, diameter, and opening angles of tributaries, was studied in 50 normal formalin-fixed adult cadaveric hearts. RESULTS: Thebesian valve (TV) and Vieussens valve were present in 64% and 60% cases, respectively. CS ostium coverage of ≥75% by TV was seen in 25% (8/32) cases. Number of prominent tributaries lying between anterior interventricular vein and middle cardiac vein varied from 1-4. In 28% of hearts, only one prominent tributary was present. Midlateral vein (average diameter 1.75 ± 0.66 mm) with an average distance of 43.5 ± 12.2 mm from coronary ostium was present in 58% (29/50) hearts, of which it formed an acute angle with CS axis in four (13.39%) cases. Posterolateral vein (average diameter 1.62 ± 0.45 mm) with an average distance of 33.4 ± 11.7 mm from coronary ostium was found in 72% (36/50) cases and formed an acute angle with CS in three (8.33%) cases. CONCLUSIONS: Restrictive TV covering ≥75% CS ostium (25% cases), presence of single prominent tributary (28% cases), and formation of acute angle of tributary with CS axis (1/4 cases with anterolateral vein, 4/29 cases with midlateral vein, 3/36 cases with posterolateral vein, and 3/28 cases with posterior veins of the left ventricle) can impede successful cannulation of CS.