Anatomy, histology, and pathology of the cardiac conduction system: Part II

Abstract

Normal anatomic and histologic features of the atrioventricular junction (transitional cell zone, atrioventricular node, penetrating portion of bundle) and the bifurcation of the penetrating portion into bundle branches are reviewed. Terminal ventricular Purkinje fibers are also discussed.

The infrahisian conduction system and endocavitary cardiac structures: relevance for the invasive electrophysiologist

“…The penetrating bundle of His is a cord-like structure measuring approximately 20 mm in length and up to 4 mm in diameter [20], identifiable by its encasement in the central fibrous body, being cytologically similar to the atrioventricular node from which it arises and undergoing a transition such that its emerging fibers are indistinguishable from those of the bundle branches [21]. In the majority of individuals, the His bundle lies towards the left of the septum and divides at the junction of the membranous septum and crest of the muscular interventricular septum into the left and right bundle branches (Fig.…”

Blood flow specific assessment of ventricular function: Visualization and quantification using 4D flow CMR

“…Action potentials leaving the AV-node enter this ventricular conduction system by the bundle of His, dividing into left and right bundle branches. These branches further divide into an extensive system of fibers that conduct the impulses at high velocities, the Purkinje fibers, that in turn are in contact with the myocardium (6). This permits the impulse to reach the whole ventricular myocardium almost simultaneously creating a rapid, organized, near-synchronous depolarization and contraction of the ventricles.…”

“…The AV-node is situated in the inferior posterior region of the atrial septum, and the specialized cells here will slow down the impulse (6). This delay in conduction is physiologically important as it allows for the late ventricular filling through atrial contraction before ventricular depolarization and contraction.…”

“…The conduction of action potentials between cells in this manner is however usually slow, why ventricular depolarization occurs via a specialized high-speed conduction system (6). Action potentials leaving the AV-node enter this ventricular conduction system by the bundle of His, dividing into left and right bundle branches.…”

“…Where ω 0 is the precession frequency, or Larmor frequency (number of precessions per second, in MHz), and γ is the gyromagnetic constant for protons (42,6 MHz/T). In a magnetic field with a strength of 1.5 T, the clinically most common for cardiac applications, the Larmor frequency for protons will be 63.9 MHz.…”