Related Experiment Video
Updated: Aug 9, 2026
Benefits of Cardiac Resynchronization Therapy in an Asynchronous Heart Failure Model Induced by Left Bundle Branch Ablation and Rapid Pacing
Published on: December 11, 2017
The effect of ventricular sequential contraction on helical heart during pacing: high septal pacing versus
Hideyuki Tomioka1, 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 90095-1741, USA.
Objective:
To investigate the effect of biventricular and high septal pacing on the normal contraction sequence of the helical ventricular myocardial band, and its impact on left ventricular function.
Methods:
Ten pigs (25-68 kg) underwent analysis of percent segmental shortening (SS%) by sonomicrometry, with crystals placed along the fiber orientation of the ascending, descending segments, and posterior LV wall within the spatial geometry of the helical heart. Unipolar pacing electrodes stimulated the right atrium (RA) and either the right ventricular apex and left ventricular posterior wall (atrio-biventricular), or the proximal high septum (atrio-high septal). Systemic hemodynamics, QRS-interval, cardiac index (CI), systolic and diastolic LV functions and pressure-dimension loops (P-D) were analyzed and cardiac motion was monitored by video analysis.
Results:
Pacing increased normal sinus heart rate (NSR) from 77+/-9 beats/min to 98+/-5 beats/min. Atrial pacing did not change the NSR hemodynamic variables. Conversely, atrio-biventricular pacing prolonged the QRS-interval (91+/-14 ms vs 56+/-11 ms at baseline, p<0.05) and decreased mean arterial pressure (50+/-4 mmHg vs 58+/-12 mmHg), CI (3.4+/-0.3 L/(min m2) vs 4.0+/-0.8 L/(min m2)) and PRSW (71+/-25%) compared to NSR (p<0.05). Furthermore, atrio-biventricular pacing decreased SS% in all segments, especially at the LV posterior wall (71% of baseline, p<0.05), and disrupted the NSR shortening sequence (progression from descending to posterior to ascending regions). Changes were characterized by premature stimulation of the posterior wall segment adjacent to the pacer stimulus, with associated (1) decrease of pressure-dimension loop area, (2) desynchronization of P-D loops and (3) consistent loss of the twisting pattern of visible cardiac motion. In contrast, atrio-high septal pacing restored systemic hemodynamics, LV systolic and diastolic functions to baseline values and preserved the normal sequence of shortening of the ventricular myocardial band.
Conclusions:
(1) Biventricular pacing disrupts of the natural sequence of shortening of the myocardial band and results in impaired LV function. (2) High septal pacing preserves the sequential shortening pattern of the myocardial band and LV function.
More Related Videos
10:17Real-Time Cardiac Mapping with a Noninvasive Imageless Electrocardiographic Imaging System
Published on: April 11, 2025
06:57Ablation of Ischemic Ventricular Tachycardia Using a Multipolar Catheter and 3-dimensional Mapping System for High-density Electro-anatomical Reconstruction
Published on: January 31, 2019
Related Concept Videos
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...
01:29Cardiac Cycle
During the cardiac cycle, blood flow through the heart is regulated entirely by changing pressure gradients. This sequence of events begins with the heart in a state of total relaxation, known as mid-to-late diastole, during which blood passively flows from...
01:19Cardiac Output I:Effect of Heart Rate on Cardiac Output
Cardiac output (CO) refers to the total amount of blood ejected by one of the ventricles in liters per minute (L/min). In a resting adult, CO ranges from 5 to 6 L/min, adjusting according to the body's metabolic requirements.
Effect of Heart Rate on Cardiac Output
Cardiac output adapts to metabolic demands during stress, physical activity, or illness. The autonomic nervous system regulates heart rate via the sinoatrial node. The parasympathetic nervous system decreases heart rate...
01:29Heart Failure II: Pathophysiology
01:19Conduction System of the Heart
The pacemaker cells are located in two primary nodes: the sinoatrial (SA) node and the atrioventricular (AV) node. The SA node pacemaker cells can autonomously depolarize, triggering an action potential that leads to the...
01:22Cardiac Output II: Effect of Stroke Volume on Cardiac Output
Preload
Preload refers to the initial elongation of the cardiac myocytes before contraction and is related to the volume of blood filling the heart at the end of diastole, or end-diastolic volume. The...