Analysis of Heart Muscle Function in Patients With Heart Disease and Normal Volunteers

Overview

Myocardial ischemia is a heart condition in which not enough blood supply and oxygen reaches the heart muscle. Damage to the major blood vessels of the heart (coronary artery disease), minor blood vessels of the heart (microvascular heart disease), or damage to the heart muscle (hypertrophic cardiomyopathy) can cause myocardial ischemia. Any of theses three conditions can cause patients to experience chest pain and other symptoms as well as cause the heart to function improperly. In order to detect myocardial ischemia researchers can use tests to measure the movement of the walls of the heart. Walls receiving inadequate supplies of blood often move less and occasionally move in the opposite direction. Some of the tests may require patients to receive injections of radioactive tracers. The radioactive material acts to enhance 3 dimensional pictures of the heart and helps to identify areas of ischemia. The purpose of this study is to determine whether 3-dimensional imaging (tomography) with radioactive tracers can provide more important information about heart wall function than routine diagnostic tests.

We propose to assess regional myocardial function using gated blood pool imaging acquired by a tomographic technique at rest and during stress in patients with myocardial ischemia (coronary artery disease, hypertrophic cardiomyopathy and microvascular angina). Gender differences in response to exercise and pharmacologic stress will also be evaluated. Normal subjects will be studied in order to establish a control database. Current methods of gated blood pool studies use planar imaging, with its attendant limitations; poor resolution and inadequate separation of the myocardial segments, only one view assessed during exercise and superimposition of overlying structures. Tomographic imaging has the advantages of reconstructing 3-dimensional data of the entire heart with the ability to improve segmental resolution and separate overlapping structures, potentially resulting in increased sensitivity and specificity for detection of disease. The role of pharmacologic stress will be assessed by comparison with exercise stress, in order to validate its use in subjects unable to exercise and identify gender related differences. Quantitative measures of regional wall motion obtained from tomography will be compared to regions of prior myocardial infarction (if present), and with other modalities for evaluating cardiac structure and function. The diagnostic and prognostic value of tomographic wall motion analysis will be studied in patients with myocardial ischemia, with special emphasis on correlation between physiologic variables of coronary blood flow and metabolic function.