This study is designed to examine the blood flow, the nutrition, and the beating function of
the heart under different conditions. Patients with narrowed coronary arteries my have
restricted blood flow to the heart. The lowered blood supply to the heart muscle may not
cause symptoms immediately. However, as the heart pumps faster and harder the blood supply
demand is increased. If blood flow is unable supply enough oxygen and nutrition to heart
muscle patients can experience symptoms of chest pain and shortness of breath. Even after
the heart slows down and demand for oxygen and nutrition is reduced, patients can still
experience pain and abnormal heart function.
The purpose of this study is to determine the changes in blood flow and the beating function
of the heart during periods of increased demands (such as exercise) and shortly after
Blood flow to the heart will be measured by positron emission tomography (PET scan). The
PET scan is a test where a small amount of radioactive water is injected into the
bloodstream and pictures of the heart are taken by the special camera. This procedure
allows researchers to measure blood flow to heart muscle. In order to measure nutrition
(metabolism) of the heart muscle, researchers will use a radioactive substance similar to
Results of this study may provide important information about the activity and function of
heart muscle after exercise in patients suffering from coronary artery disease.
Exercise-induced left ventricular regional wall motion abnormalities among patients with
coronary artery disease indicate myocardial ischemia due to significant coronary artery
narrowing. Recovery of such stress-induced wall motion abnormalities is thought to occur
within minutes after the termination of exercise. However, in some patients, persistent
contractile dysfunction has been observed up to 90 minutes into recovery. Whether
persistent regional wall motion abnormalities after exercise are due to stunned myocardium
(prolonged but reversible postischemic dysfunction despite restoration of blood flow) or
persistent ischemia due to coronary vasoconstriction (prolonged postischemic dysfunction due
to persistent reduction of regional blood flow) is not well established. It is possible
that persistent but reversible left ventricular dysfunction post-exercise may represent
persistent reduction in regional blood flow and/or altered regional metabolic state.
In this protocol, we intend to elucidate the mechanisms of prolonged but reversible
post-exercise left ventricular contractile dysfunction. Results of this study may provide
insight into the post-exercise cardiovascular physiology among patients with coronary artery
disease. In addition, clinical implications can be drawn regarding patient safety and
timing of discharge from the exercise laboratory, as well as timing of post-exercise
myocardial perfusion studies.
We propose to evaluate left ventricular regional wall motion by gated blood pool tomographic
(SPECT) imaging at rest, during maximal exercise, 15 and 30 minutes after termination of
exercise. Myocardial perfusion (O-15 water) and metabolic (F-18 deoxyglucose) studies will
be performed utilizing positron emission tomography (PET). Absolute regional myocardial
blood flow (ml/min/gm) will be assessed at rest, during maximal exercise, 15 and 30 minutes
post-exercise along with myocardial fluorodeoxyglucose utilization 45 to 90 minutes
post-exercise. Patients afflicted with conditions that limit their capacity to perform an
adequate exercise study will undergo pharmacological stress study with dobutamine. Normal
subjects will also be studied in order to create a control database.
Adult patients with greater than 50% stenosis in at least one major coronary artery.
No significant valvular heart disease.
No congenital heart disease.
No myocardial disease unrelated to co-existing coronary artery disease.
No severe angina where withdrawal of therapy would be dangerous.
No recent unstable angina or myocardial infarction (less than 1 month).
Not pregnant or breast feeding.
No history of ventricular tachycardia or malignant arrhythmias.
No history of active bronchospastic disease.