Anatomy for right ventricular lead implantation

Abstract

To understand the position of a pacing lead in the right ventricle and to correctly interpret fluoroscopy and intracardiac signals, good anatomical knowledge is required. The right ventricle can be separated into an inlet, an outlet, and an apical compartment. The inlet and outlet are separated by the septomarginal trabeculae, while the apex is situated below the moderator band. A lead position in the right ventricular apex is less desirable, last but not least due to the thin myocardial wall. Many leads supposed to be implanted in the apex are in fact fixed rather within the trabeculae in the inlet, which are sometimes difficult to pass. In the right ventricular outflow tract (RVOT), the free wall is easier to reach than the septal due to the fact that the RVOT wraps around the septum. A mid-septal position close to the moderator band is relatively simple to achieve and due to the vicinity of the right bundle branch may produce a narrower paced QRS complex. Special and detailed knowledge is necessary for His bundle and left bundle branch pacing.

Keywords: Fluoroscopy; Moderator band; Right ventricular outflow tract; Septal right ventricular pacing; Septomarginal trabeculations.

Fig. 1

Anatomy of the right ventricle (RV). a In a frontal view, the tricuspid valve is seen with its septal leaflet (SL), anterior leaflet (AL), and inferior leaflet (IL). They lead to the inlet compartment of the RV. At the border to the outlet compartment, there is the septomarginal trabeculation (SMT) with an anterior (a), superior, and a posterior (p), inferior branch. At the septum, outlet and inlet are connected by the ventriculo-infundibular fold (VIF). The moderator band (MB) crosses the RV from SMT to the anterior papillary muscle (APM) and marks the border between inlet and apical compartment of the RV. With permission © Sieuw Yen Ho, London. b View to the inlet compartment of the RV (bovine heart). Note the fasciculae of the right bundle branch (arrows) within the septomarginal trabeculation (SMT) and moderator band (MB). The atrioventricular node and atrial part of the proximal His bundle (dotted arrows) are shining through the endocardium above the septal leaflet (SL) of the tricuspid valve. AL anterior leaflet. Note the thinning of the myocardium at the RV apex

Fig. 2

Dual-chamber implantable cardioverter-defibrillator (ICD) with a lead position in the right ventricular (RV) apex. Patient with sternotomy and aortic valve replacement. a Chest X‑ray in postero-anterior (PA) projection. b Chest X‑ray in right lateral 90° projection. The ventricular lead is implanted in the RV apex. Since this is an ICD lead (stiffer than a pacemaker lead), perforation at the RV apex is a risk, particularly if abundant lead slack (big loop in the right atrium in the lateral projection!) pushes the lead against the RV apex with each heartbeat. c Left anterior oblique (LAO) 40° view (after upgrade to a biventricular ICD). The RV lead positioned in the RV apex points towards 5 o’clock. Dotted line: approximate ventricular septum. d Right anterior oblique (RAO) 30° projection. The lead tip is positioned deep in the RV apex but still millimeters apart from the silhouette (otherwise: suspicion of perforation). Red circle: presumed approximate atrioventricular valve plane, the ventricular silhouette is divided into three segments: basal (B), mid (M), and apical (A) third

Fig. 3

Right ventricular outflow tract. The medial septal part has a smooth surface, while the anterior part of the muscular tube has multiple trabeculae and recesses below the pulmonary valve. With permission, © Siew Yen Ho, London, UK

Fig. 4

Right ventricular (RV) mid-septal and His bundle pacing in a patient with tricuspid valve repair. In this patient with a Cardioband® (Edwards, Irvive, CA, USA), the ring of the tricuspid valve is visible. a Chest X‑ray in the posterior-anterior view. The mid-septal RV back-up lead points towards the right side (3 o’clock), the bipolar tip of the thin His bundle pacing lead is attached on the ventricular part of the His bundle at the “roof” of the inlet compartment. b Chest X‑ray in the right lateral view (90°). The RV back-up lead points towards the sternum, overlapping the anterior end of the tricuspid valve. The His bundle lead is positioned close to the posterior end of the tricuspid ring. c Fluoroscopy in left anterior oblique (LAO) 40° projection. This is a fundamental view to understand the lead position. The RV back-up lead points straight to the spine (3 o’clock position). The His bundle lead is positioned just superior to the septal leaflet of the tricuspid valve. d Fluoroscopy in right anterior oblique (RAO) 30° projection. The RV back-up lead still points towards 3 o’clock, in this projection the middle third of the RV (basal, mid, apical). The His bundle lead seems to be on the atrial side of the tricuspid valve. e Fluoroscopy in RAO 12° projection. In this view, the leaflets of the tricuspid valve completely overlap; therefore the exact site of His bundle lead implantation can be assessed. The tip is obviously at the rather distal part, some millimeters into the ventricular side

Fig. 5

Atrioventricular (AV) node and His bundle. The AV node (green with dotted points) is located on the atrial side, slightly above the insertion of the septal leaflet of the tricuspid valve and anterior to the coronary sinus (CS) ostium. Its distal portion points towards the commissure (com) between the septal and anterior leaflet. It transitions to the His bundle on the atrial part of the membranous septum, which is separated from the ventricular membranous septum by the septal leaflet. White circle and arrow: membranous septum, AL anterior leaflet, IL inferior leaflet, IVC inferior vena cava, SL septal leaflet, SVC superior vena cava. With permission, © Siew Yen Ho, London, UK

Fig. 6

View from the right atrium to the tricuspid valve and entrance to the right ventricle. The His bundle typically perforates the tricuspid annulus at the commissure (red arrow) between septal (SL) and anterior leaflet (AL) of the tricuspid valve. The atrial and interventricular membranous septum is transilluminated. © With permission José Angel Cabrera, Madrid, Spain

Fig. 7

View on the subendocardial branches of the left bundle branch (LBB). The LBB penetrates the membranous septum between the right and the non-coronary cusps of the aortic valve and divides into a widespread subendocardial network on the left side (white subendocardial fibers). a Human heart, with permission, © Siew Yen Ho, London, UK. b Bovine heart. Solid arrows: location of transseptal perforation of the LBB between the non-coronary and right coronary cusps; dotted arrows: widespread network of multiple subendocardial fascicles of the LBB

Fig. 8

Fluoroscopy with contrast in left bundle branch (LBB) pacing. In this left anterior oblique view at 40°, the LBB pacing lead is visible screwed into the interventricular septum. Dotted line: right ventricular surface of the septum. At a depth of > 10 mm, it captured the proximal LBB. Upgrade in a patient with chronic failure of the left ventricular lead implanted via the coronary sinus (CS). RA right atrial lead at the high right atrial septum, RV right ventricular lead at the mid right ventricular septum

Fig. 9

Echocardiography in left bundle branch (LBB) pacing. In the apical view, the tip of the LBB pacing lead (arrow) is visible just under the left ventricular endocardial surface. LA left atrium, LV left ventricle, RA right atrium, RV right ventricle