In vivo myocardial tissue kinetics of Gd(ABE-DTTA), a tissue-persistent contrast agent.

ABSTRACT

The phenomenological tissue kinetics of Gd(ABE-DTTA) was investigated in myocardial infarction (MI). Reperfused infarction was generated by balloon catheter in closed-chest canines (N=11). Forty-eight hours thereafter, inversion-recovery (IR)-prepared fast gradient-echo control images were acquired with varying inversion times (TIs). Precontrast R(1) maps were calculated from the TI dependence of signal intensity (SI) using nonlinear curve fitting. Then 0.05 mmol/kg Gd(ABE-DTTA) was administered I.V. In 11 dogs postcontrast R(1) maps were generated at 24 hr and 48 hr postcontrast. In five dogs measurements were also repeated at 108 hr and 12 days. In one dog early measurement was carried out at 4 hr. Delta R(1) values for blood and viable and infarcted myocardium were calculated at each time point by subtracting the precontrast R(1) from the postcontrast R(1). Gd(ABE-DTTA) showed significant, progressive accumulation into infarcts during the first 2 days (k(in)=0.39 hr(-1)) and a delayed clearance (k(out) = 0.005 hr(-1)). Among the time points sampled, the maximum infarct Delta R(1) was detected at 48 hr (1.72 s(-1)). Contrast agent (CA) in infarcted tissue was detectable for 12 days. Clearance from blood and viable myocardium occurred in parallel and was completed by 108 hr. Gd(ABE-DTTA) displays slow, tissue-persistent kinetics and partly intravascular, partly extravascular characteristics. It demonstrates high affinity for infarcted myocardium and induces highlighting of infarcts between 4 hr and 12 days following administration.