1. Novel Programmable Isolated Perfused Heart Apparatus to Study Heart-
Vasculature Interaction In Vitro
Michael T. McDowall, Cole Nipper, Alex Urquia, Nolan R. Stowe, Christopher M. Quick, Ranjeet M. Dongaonkar
Michael E. DeBakey Institute, Texas A&M University, College Station, TX 77843
Introduction: Left ventricular volume, one of the most important factors that determines cardiac function, arises
from the dynamic interaction between the heart and the vasculature. Although in vivo characterization of cardiac
function includes the heart-vasculature interaction, the effects of homeostatic feedback mechanisms confound
such characterization. Isolated perfused heart experiments eliminate the confounding effects of feedback
mechanisms; however, they are limited due to the exclusion of the heart-vasculature interaction. Numerical
approaches allow characterization of effects of dynamic interaction between the heart and the vasculature on
cardiac function. However, these approaches are also limited because a particular set of assumed cardiac
parameters limits the generality of the results. Therefore, the goal of the present work was to integrate and exploit
the advantages of both numerical and in vitro experimental approaches to develop a programmable isolated heart
apparatus for characterizing the effects of dynamic interaction between the heart and the vasculature on the
isolated perfused heart.
Materials and Methods: Following cannulation and retrograde perfusion of the isolated rat heart, a balloon
attached to a fluid-filled catheter was inserted into the left ventricle through the pulmonary artery and left atrium.
A pressure transducer and a piezoelectric linear pump, controlled with a custom made LabVIEW virtual
instrument (VI), were connected to the catheter. Pressure generated by the contracting ventricle was measured and
used as an input to our cardiovascular system model to estimate ventricular volume. The linear pump was then
used to set the ventricular volume to match this estimated value, allowing the ventricle to contract and generate
pressure. The lumped parameter model includes pulmonary and systemic vascular compliances and resistances, a
right ventricle, and mitral and aortic valves.
Results and Discussion: Parameter values used in the cardiovascular system model were set to mimic altered
vascular conditions and cardiac responses were determined using left ventricular pressure-volume relationship. By
exploiting the advantages of both numerical and in vitro experimental approaches, it is not only possible to
rapidly simulate effects of changes in preload and afterload but also to mimic the complexities arising from heart-
vascular interaction.
P: pressure
R: resistance
s, p: systemic, pulmonary
a, v: arterial, venous
RV, LV: right ventricle, left ventricle
LA: left atrium
LVP: left ventricular pressure
Figure 1: Left ventricular volume was set to the value
estimated using lumped parameter model of the
cardiovascular system. Pressure generated by the
isolated perfused heart contraction was measured and
used as input to the cardiovascular system model.
Pulmonary*
Vasculature*
Cardiac*
Ventricles*
Systemic*
Vasculature*
Ppa$
Ppv$
Rp$
Psa$
Psv$
Rs$
RV$
Cardiovascular,System,Model,,
Es4mated,Le6,
Ventricular,Volume,
Le6,Ventricular,,
Pressure,
Isolated,Perfused,Heart,
Perfusion,
,Cannula,
Aorta,
LA,
RA,
LV,
Fluid,Filled,
Balloon,
LVP,
Pump,
,
Pacing,
Electrode,