Comparison of cardiac to hepatic uptake of 99mTc-tetrofosmin with and without adenosine infusion to predict the presence of haemodynamically significant coronary artery disease.

Background Coronary artery disease impairs cardiac vasodilatory reserve. A low ratio of cardiac to hepatic vasodilatory reserve may be diagnostic for coronary artery disease. Aim To compare the ratio of cardiac to hepaticuptake of 9 9 m Tc-tetrofosmin during adenosine infusion and at rest in patients with and without coronary artery disease in order to determine whether the ratio was significantly different between the two groups. Methods Fifty-one patients who underwent coronary angiography and adenosine stress myocardial perfusion imaging using 9 9 m Tc-tetrofosmin were studied retrospectively. Anterior planar images from the single photon emission computed tomography (SPECT) raw data were used to draw regions of interest around the heart and liver. The counts per pixel in each region were used to calculate the stress ratio (SR) and the rest ratio (RR) as follows: SR=(cardiac counts per pixel)at s t r e s s /(hepatic counts per pixel) a t stress; RR=(cardiac counts per pixel)at r e s t /(hepatic counts per pixel)at rest. The SR and SR/RR ratios were compared in patients with and without significant coronary artery disease. Receiver operating characteristic curves were drawn for SR and SR/RR. Results The SR and SR/RR ratios were significantly lower in patients with significant coronary artery disease than in patients without (P<0.001). A cut-off ratio of SR/RR=1.00 yielded 87% sensitivity and 74% specificity for the detection of significant coronary artery disease. Combining SR/ RR with standard SPECT image interpretation increased the sensitivity without substantially changing the specificity in comparison with standard SPECT image interpretation only. Conclusion Comparison of cardiac to hepatic 9 9 m Tc-tetrofosmin concentration at rest and under adenosine stress provides useful diagnostic information for the assessment of the presence of significant coronary artery disease.