ECHOCARDIOGRAPHY OF MYOCARDIAL PERFUSION/FUNCTION

There is no readily available method that can be used to precisely
assess both regional myocardial perfusion and function in humans.
It has been recently demonstrated by the principal investigator
and others that myocardial contrast echocardiography can be
utilized to define zones of decreased perfusion. Further, two-
dimensional echocardiography has also been used by the principal
investigator and others for quantitating regional myocardial
function. This proposal aims at developing these techniques using
computer analysis for simultaneous assessment of regional
perfusion and function, first in the animal model, and later in
humans. An attempt will be made to understand the relationship
between myocardial contrast parameters and regional myocardial
blood flow as measured by radiolabeled microspheres and mean
coronary transit times using technetium labeled red cells.
Algorithms will be developed to measure absolute regional
myocardial blood flow derived from parameters obtained from the
washout of contrast from the myocardium. It is hoped that this
research will provide an in-depth understanding of the kinetics of
microbubbles through the myocardium at different coronary flow
rates and the effect of flow on the microbubbles. The optimal
contrast agent and the optimal method for injection of the agent
without causing a hyperemic response will be developed. The
effect of this agent on normal and ischemic human myocardium
will be studied. Although methods for measuring regional
myocardial function have been previously described, there are
limitations in these methods which mostly relate to defining the
center of mass in an ischemic ventricle and overall translation of
the heart. This proposal defines a new approach for quantifying
regional myocardial function using a sophisticated computer
algorithm which is independent of the center of mass and is not
affected by cardiac translation. Using these techniques, we aim
to study the relationship between transmural and endocardial
blood flow and regional myocardial function over varying degrees
of coronary blood flow. It is also proposed to estimate coronary
flow reserve in humans prior to and following coronary
angioplasty to determine if changes in coronary flow reserve
correlate with the success of coronary angioplasty and the
restenosis rate following the procedure. It is hoped that these
methods can be used to assess regional myocardial perfusion and
function simultaneously in humans using tow-dimensional
echocardiography.