The anatomic basis for ventricular arrhythmia in the normal heart: what the student of anatomy needs to know

Abstract

The traditional route for teaching cardiac anatomy involves didactic instruction, cadaver dissections, and familiarization with the main structure and relationships of the cardiac chambers, valves, and vasculature. In contemporary cardiac electrophysiology, however, a very different view of anatomy is required including details rarely appreciated with a general overview. In this review, we discuss the critical advances in cardiac electrophysiology that were possible only because of understanding detailed anatomic relationships. While we briefly discuss the clinical relevance, we explain in depth the necessary structural information for the student of clinical anatomy. Interspersed through the text are boxes that highlight and summarize the critical pieces of knowledge to be borne in mind while studying the fascinating structural anatomy of the human heart.

Keywords: cardiac anatomy; catheter ablation; complications; outflow tract; ventricular tachycardia.

Figure 1

Anatomical relationships of the ventricular outflow tract. The RVOT lies anterior to the left ventricular outflow tract. It arises above the tricuspid annulus and directs upward and leftward. As a result, the distal right ventricular outflow tract is leftward and cephalad to the left ventricular outflow tract. Also note that while the pulmonary valve lies horizontally, while the aortic root is tilted up on its left. RVOT: right ventricular outflow tract; LVOT: left ventricular outflow tract.

Figure 2

Anatomical relationship of the aortic sinuses and the neighboring cardiac structures. The right coronary sinus lies immediately posterior to the mid right ventricular outflow tract. To its right it is closely related to the right atrial appendage and the superior vena cava-right atrial junction. As the aortic root is tilted up on the left, and the right ventricular outflow tract runs directs upward and leftward, the anterior portion of the left coronary sinus is in close proximity to the subpulmonic right ventricular outflow tract. The posterior lobe of the left atrial appendage is situated on the left side of the left coronary sinus. The non-coronary sinus is the most posteriorly located aortic sinus. It lies anterior to the mid interatrial septum and the adjacent right and left atrial walls, and is not anatomically related to any ventricular muscles. The membranous septum is located at the junction between the right and non-coronary sinuses. This is a consistent site where the His bundle penetrates the left ventricle. RVOT: right ventricular outflow tract; R: right (coronary sinus); L: left (coronary sinus); N: non- (coronary sinus); SVC: superior vena cava.

Figure 3

The aortomitral continuity separating the left ventricular inflow and outflow tracts. The aortomitral continuity is a fibrous structure extending from the left fibrous trigone at the posterior left coronary leaflet to the right fibrous trigone between the right and non-coronary leaflets. The membranous septum is located below the junction of the valvar attachments of the right and non-coronary leaflets, which is a consistent site where the bundle of His penetrates the left ventricle. The membranous septum and the right fibrous trigone are collectively known as the central fibrous body. R: right (coronary leaflet); N: non- (coronary leaflet); L: left (coronary leaflet); MV: mitral valve; LBB: left bundle branch.

Figure 4

Gross specimen showing the position of the membranous septum (transilluminated) in between the right coronary and non-coronary leaflets. R: right (coronary leaflet); N: non- (coronary leaflet); Ao: Aorta; MS: membranous septum; LV: left ventricle.

Figure 5

Gross specimen illustrating the location of the penetrating His bundle at the atrioventricular portion of the membranous septum. RA – right atrium; RV – right ventricle; Ao – Aorta; AV – atrioventricular; LV – left ventricle.

Figure 6

Schematic diagram showing individual component of the aortic root. As each aortic valvar leaflet is attached to the left ventricular outflow in semilunar fashion, the valvar attachment to the outflow is in fact a crown-like structure rather than the traditional sense of an annulus (ring-like). The wall of the aortic root within the boundaries of each aortic valvar leaflet expands to form the corresponding aortic sinus. The aortic root is bounded at the top by the sinotubular junction, and at the bottom by the virtual ring formed by the basal attachments of the three aortic valvar leaflets. As the ventriculo-arterial junction is located in between these two rings, ventricular myocardial fibers are included in the aortic sinuses but never extend beyond the sinotubular junction.

Figure 7

Relationship of the coronary arteries and veins to the ventricular outflow tracts. RVOT: right ventricular outflow tract. SVC: superior vena cava.

Figure 8

A. Limb lead positions for electrocardiographic recordings. B. Precordial lead positions for electrocardiographic recordings.

Figure 9

Classical electrocardiogram of right ventricular outflow tract tachycardia associated with left bundle branch block morphology and inferior axis. LBBB: left bundle branch block.

Figure 10

Classical electrocardiogram of left ventricular outflow tract premature ventricular complexes associated with right bundle branch block morphology and inferior axis. RBBB: right bundle branch block.

Figure 11

Non-sustained ventricular tachycardia originating from the paraHisian region. Note the left bundle branch block pattern, positive aVL and negative aVR. Because of medically refractory symptoms and tachycardia-mediated cardiomyopathy, patient agreed to proceed to ablation with the understanding that heart block may result. Procedure was performed which was complicated with permanent atrioventricular block requiring pacemaker implantation.