[Myocardial perfusion reserve studied by single-photon emission-computed tomography with thallium-201 and a drug stress test with adenosine triphosphate in patients with cardiovascular risk factors].
OBJECTIVE
Recent studies have suggested that the evaluation of coronary reserve is a sensitive method in the early detection of vascular alterations before plaques exist, and certainly before clinical detection of atherosclerotic lesions. Single-photon emission-computed tomography (SPECT) with thallium-201 (201Tl) provides a noninvasive tool for evaluating myocardial perfusion reserve. The objective of this study was to measure the myocardial perfusion reserve in two groups of subjects, some with and some without cardiovascular risk factors and in a group of patients with coronary artery disease.


METHODS
Seventy-four subjects, divided into three groups, were recruited to assess regional and global myocardial perfusion reserve. The control group consisted of 11 asymptomatic individuals without cardiovascular risk factors. The second group was composed of 49 patients with one or more risk factors. Finally, the third group included 14 patients with coronary artery disease. 201Tl-SPECT at rest and after pharmacological stress with a 7 minute adenosine triphosphate (ATP) infusion (140 micrograms/kg/min) was performed in all patients. ATP minus rest value subtraction was applied in order to obtain the stress data. Relative myocardial perfusion reserve indices were calculated as the ratio between stress and rest values.


RESULTS
Global and regional myocardial perfusion reserves of the vascular territories were significantly lower in patients with cardiovascular risk factors than in control subjects (Global: 1.48 +/- 0.19 vs 1.81 +/- 0.08, LAD: 1.52 +/- 0.21 vs 1.85 +/- 0.09, CX: 1.45 +/- 0.2 vs 1.79 +/- 0.86, RCA: 1.47 +/- 0.2 vs 1.79 +/- 0.86) and higher than in patients with coronary artery disease (Global: 1.48 +/- 0.19 vs 1.31 +/- 0.14, LAD: 1.52 +/- 0.21 vs 1.35 +/- 0.15, CX: 1.45 +/- 0.2 vs 1.2 +/- 0.24). Univariate linear regression analysis in a group of 40 patients with high risk lipid profiles revealed a significant negative correlation between myocardial perfusion reserve and total cholesterol (r = -0.35; p = 0.01), LDL-cholesterol (r = -0.38; p = 0.036) and LDL/HDL ratio (r = -0.39; p = 0.029).


CONCLUSIONS
Determination of myocardial perfusion reserve with 201Tl-SPECT allows the detection of abnormal vasodilatory response to intravenous ATP in patients with cardiovascular risk factors. These patients have higher reserves than patients with coronary disease, which might suggest an early phase of atherosclerosis.
Huelmos Rodrigo
A
A
Departamento de Cardiología y Cirugía Cardiovascular, Facultad de Medicina, Universidad de Navarra, Pamplona.
García Velloso
M J
MJ
Alegría Ezquerra
E
E
Richter Echevarría
J A
JA
Martínez Caro
D
D
D000255:Adenosine Triphosphate; D000328:Adult; D000368:Aged; D003326:Coronary Circulation / Q000187:drug effects; D003327:Coronary Disease / Q000097:blood / Q000175:diagnosis*; D005080:Exercise Test / Q000379:methods* / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D008055:Lipids / Q000097:blood; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D013794:Thallium Radioisotopes; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods* / Q000706:statistics & numerical data
D008055:Lipids; D013794:Thallium Radioisotopes; D000255:Adenosine Triphosphate