Related Experiment Video
Updated: Aug 9, 2026
Three-Dimensional Echocardiographic Method for the Visualization and Assessment of Specific Parameters of the Pulmonary Veins
Published on: October 28, 2020
Septal structure and function relationships parallel the left ventricular free wall ascending and descending segments
Nikola Hristov1, Oliver J Liakopoulos, Gerald D Buckberg
1Department of Surgery, Division of Cardiothoracic Surgery, David Geffen School of Medicine at University of California Los Angeles, 10833 Le Conte Avenue, 62-258 CHS, Los Angeles, CA 90095-1701, USA.
Objective:
Determine if ventricular septum structure and function relationships parallel the left ventricular free wall descending and ascending segments of the helical heart.
Methods:
Forty pigs (30-38 kg) were studied physiologically by sonomicrometer to determine if septal fiber orientation resembled responses in the free wall. Following pilot studies in the non-bypassed heart, a right ventriculotomy was made to place septum crystals with fiber orientations that were either perpendicular to or reflected simultaneous free wall measurements. Postbypass measurements tested responses to positive (dopamine) and negative (esmolol) inotropic agents.
Results:
Similar oblique fiber directions were found for baseline percent systolic shortening (SS%) in the free wall and septum; free wall descending and ascending SS% were 21+/-3% and 10+/-3%, and 13+/-2% and 12+/-2%, respectively, in the septum. Conversely, impaired shortening occurred when transverse fiber direction was tested. Both oblique areas demonstrated comparable time-delay changes between free wall and septal descending and ascending segment at onset (75+/-11 ms) and termination (86+/-21 ms) of contraction. Dopamine increased heart rate and caused a similar increase of free wall descending and ascending segment SS% to 24+/-2% and 14+/-3% (p<0.05), and septal SS% response to 16+/-2% and 15+/-2% (p<0.05), and comparable decrease of time-delay changes of shortening between ascending and descending segments of 54+/-6 ms and 68+/-10 ms, respectively (p<0.05). Conversely, esmolol decreased heart rate and similarly reduced SS% in left ventricular free wall (descending: 18+/-4%; ascending: 7+/-4%; p<0.05) and septum (descending: 10+/-2%; ascending: 10+/-3%; p<0.05). Time-delay of contraction between segments was increased to 91+/-4 ms (p<0.05), but the hiatus at the end of shortening remained unchanged, due to prolonged endocardial contraction.
Conclusions:
Septal structure and function relationships parallel the left ventricular free wall ascending and descending segments, thereby supporting the helical heart fiber spatial relationships. The oblique fiber orientation may make the septum become the 'lion of right ventricular function'.
Related Concept Videos
01:27Development of the Heart
As the embryo undergoes lateral folding, these paired tubes approach each other, merging into a single primitive heart tube by...
01:16Chambers of the Heart
Deoxygenated blood from the body is received in the right...
01:27Anatomy of the Heart
01:20Anatomy of the Heart
The heart has three layers: the innermost endocardium, the muscular myocardium, and the outer epicardium, all working together for optimal cardiac function.
Chambers of the Heart
The heart is made up of four...
01:13The Cardiac Cycle
The Process
Electrical signals—sent from the sinoatrial (SA) node in the right atrial wall to the atrioventricular (AV) node between the right atrium and right ventricle—cause both atria to simultaneously contract. When the signal reaches the AV node, it pauses for approximately a tenth of a second, allowing the atria to contract and empty blood into the...
01:15Layers of the Heart Wall
The myocardium, the thickest layer, consists of cardiac muscle cells interconnected by intercalated discs and crisscrossing connective tissue fibers. These muscle fibers contract...