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International Conference on Complex Systems (ICCS2006)

Manifestations of Cellular Contraction Patterns on the Cardiac Flow Output

Edward Marcus
Children's Hospital Boston Department of Cardiology

     Full text: Not available
     Last modified: May 1, 2006

Abstract
Manifestations of Cellular Contraction Patterns on the Cardiac Flow Output

Edward Marcus 1, Ira Cheifetz 2, Damian Craig 3, Rupak Mukherjee 4


Introduction: On a microscopic scale, the heart consists of cells (myocytes) whose contracting motions are activated by electrical stimulations. At physiological scale, the heart is a chamber whose dimensions are reduced during systolic contraction and outflow. We have developed a model to describe the kinematics of a contracting cell as the underlying source of flows measured from a ventricle during ejection.

Methods: In ten piglet hearts, the pressure and outflow is recorded and a characteristic measure of each ventricle’s compliance C and arterial input resistance R is derived. As reported previously, the hearts ejection consistently demonstrates a characteristic time constant T= RxC indicative of the mechanical discharge between the ventricle’s compliance and the artery’s resistance. With an R x C ventricular-arterial discharge model, measured flow signals from all hearts are deconvolved to derive an average source function. The resulting source function is then correlated to the velocity measured from isolated contracting cells.

Results: Deconvolution of the ventricle’s outflow into a source function indicates a time of maximum velocity by the flow source occurring 60 msec after activation, and a time of maximum displacement occurring 187 msec following activation. Velocity and displacement measures of contracting cardiac cells demonstrate these identical timings.


Outflow Source Contracting Cells
(10 animals, 100 beats) (9 cells, 18 beats)

Time Maximum Velocity 60 msec 60 ± 16 msec
Time Maximum Displacement 187 msec 189 ± 32 msec


Conclusion: A heart’s contraction is induced by simultaneous and aggregate shortening movements of cells embedded in the ventricle’s tissue. These cellular motions are manifested as flows at a physiological scale through a convolution of the cell’s contractile motion with a mechanical discharge response between the ventricle and the arterial input.


1.Boston Children’s Hospital, Department of Cardiology USA
2.Duke Children’s Hospital and Medical Center, Division of Pediatric Critical Care Medicine USA
3.Duke Children’s Hospital and Medical Center, Division of Cardiothoracic Surgery USA
4.Medical University of South Carolina, Department of Surgery, Cardiothoracic Surgery Research USA




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