T max is a sensitive indicator of myocardial ischaemia under adenosine stress as determined by static PET imaging: a study in a porcine model.

AIM: To evaluate Tmax , defined as the time of residual function R(t) reaching its maximum, as an indicator of myocardial ischaemia and compare its efficacy with other computed tomography perfusion (CTP) parameters.

MATERIALS AND METHODS: Eight Bama miniature pigs with 50-90% left anterior descending artery stenosis underwent adenosine stress myocardial CTP and 13 NNH3 position-emission tomography (PET) perfusion imaging. Tmax , myocardial blood flow (MBF), myocardial blood volume (MBV), mean transit time (MTT), and time to peak (TTP) were calculated from CTP images. PET images were evaluated as ischaemia or non-ischaemia. Using PET as a reference standard, the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy were calculated. Multiple comparisons of the receiver operating characteristic (ROC) curves between Tmax and other parameters were performed. The diagnostic performance of the combination of each two parameters was calculated and compared with Tmax. RESULTS: Tmax was significantly higher in ischaemic segments compared with non-ischaemic segments. Multiple comparisons of the ROCs indicated that Tmax was better than MBF or TTP but not statistically different from MBV. Tmax was superior to the combination of (MBF + MBV) but not to (MBF + TTP) or (MBV + TTP).

CONCLUSION: Tmax in dynamic stress CTP provides good diagnostic accuracy for detecting myocardial ischaemia, especially in sensitivity and NPV, compared with PET method. Tmax has better performance than MBF or TTP or combination of (MBF + MBV) in diagnosing myocardial ischaemia.