Leonardo da Vinci's flights of the mind must continue: cardiac architecture and the fundamental relation of form and function revisited

Abstract

This overview addresses the remarkable efficiency of the mammalian heart as a pump of unique capacity to quickly vary output and ejection velocity and its relation to ventricular geometry, fiber architecture, integrity of collagen scaffold and microvasculature and appropriate electrical activation. The unique functional capacity of the ventricle depends critically on the organization of cardiac muscle fibers in layers of counter-wound helices encircling the ventricular cavity in a pattern that allows a special twisting motion during systole and early diastole, essential to the mechanical efficiency of the normal ventricle to eject and suction venous return. The important contribution of advances in imaging techniques is reviewed, especially magnetic resonance with tagging and tensor analysis to define fiber orientation; these measurements are made without the use of implanted devices that can distort structure and even impair function. The impact of loss of optimal fiber orientation and geometry of the ventricle as a result of diseases that cause heart failure is analyzed, along with the possibility of improvement by carefully planned surgical restoration of ventricular geometry. The very encouraging results yielded by these therapeutic strategies are critically dependent on a clear understanding of the relation of structure and function that our analysis attempts to promote. Simultaneously, there is full acknowledgment of the unanswered questions that are inevitable but equally essential to the continuing search that scientific progress depends on.

Neonatal Murine Heart Slices. A Robust Model to Study Ventricular Isometric Contractions

“…It is known that cardiac fiber arrangement as counter-wound helices encircling the ventricles is crucial for achieving sufficient ejection fractions [36]. Fiber direction is oriented predominantly in the base-apex direction on the epicardial and endocardial surfaces and is rotated to a circumferential direction in the midwall only [20].…”

Myocardial Deformation in Acute Myocarditis With Normal Left Ventricular Wall Motion - A Cardiac Magnetic Resonance and 2-Dimensional Strain Echocardiographic Study -

“…These are predominantly longitudinal in the subendocardial region (right-handed helix), become circumferential in the mid-wall, and resume a longitudinal orientation at the subepicardial surface (left-handed helix). [28][29][30] During ejection, the ventricular volume is reduced as a result of contraction of both the subendocardial and subepicardial layers. 1-3 Whenever one of these is damaged (subendocardium in myocardial infarction, subepicardium in focal acute myocarditis), longitudinal function is impaired.…”

Insights into Biomedicine from Animal Adaptations

“…Although the adult giraffe heart has the same relative mass as that of mammals in general (22,76), it has a different shape than that of the human heart, being much more elliptical (29). This shape allows the left ventricle of the giraffe heart to generate the pressures required to maintain adequate cerebral perfusion (29).…”

“…This shape allows the left ventricle of the giraffe heart to generate the pressures required to maintain adequate cerebral perfusion (29). Although the giraffe heart is not unusually large, the left ventricular and interventricular walls are massively thickened (44,76) with wall thickness being linearly related to neck length (76).…”