Technetium-99m-labelled HL91 and technetium-99m-labelled MIBI SPECT imaging for the detection of ischaemic viable myocardium: a preliminary study

Purpose: The assessment of myocardial viability has become an important aspect of the diagnostic and prognostic work‐up of patients with coronary artery disease. Technetium‐99m labelled sestamibi (^99mTc‐MIBI) myocardial perfusion imaging may underestimate the viability of ischaemic myocardium. Technetium‐99m labelled 4,9‐diaza‐3,3,10,10‐tetramethyldodecan‐2,11‐dione dioxime (^99mTc‐HL91) is a hypoxia‐avid agent which can identify acutely ischaemic viable myocardium in a canine model using a standard gamma camera. The aim of this study was to evaluate uptake character of ischaemic viable myocardium and diagnostic performance of single‐photon emission computed tomography (SPECT) imaging by ^99mTc‐HL91 and ^99mTc‐MIBI in detecting ischaemic viable myocardium in coronary heart disease. Methods: A total of 41 patients with coronary artery disease were recruited from March 2008 to May 2009. For detecting ischaemic viable myocardium, SPECT imaging by ^99mTc‐HL91 and ^99mTc‐MIBI were performed in all patients before coronary revascularization. Six patients with single ischaemic myocardial segment received a 2‐day SEPCT/CT imaging protocol and the uptake of ^99mTc‐HL91 in ischaemic myocardium was quantitatively analysed. The remaining 35 patients received a 1‐day ^99mTc‐HL91 and ^99mTc‐MIBI SPECT imaging protocol. Resting ^99mTc‐MIBI myocardial perfusion imaging in 3–18 months after revascularization was used as the standard methodology to evaluate the myocardial viability. Results: In 41 patients, 66 ischaemic myocardial segments were proven to be viable and 12 to be necrotic by resting ^99mTc‐MIBI myocardial perfusion imaging after coronary revascularization. Furthermore, 60 viable segments with negative uptake of ^99mTc‐MIBI showed positive uptake of ^99mTc‐HL91. The remaining six viable segments and 12 necrotic segments showed both negative uptake of ^99mTc‐HL91 and ^99mTc‐MIBI. The sensitivity, specificity, accuracy, Younden Index, positive predictive value and negative predictive value for evaluating ischaemic viable myocardium were 90·9%, 100%, 92·3%, 90·9%, 100% and 66·7%, respectively. Ischaemic viable myocardium had the negative ^99mTc‐MIBI uptake and positive ^99mTc‐HL91 uptake, which demonstrated a mismatched uptake character. Quantitative analysis indicated the uptake of ^99mTc‐HL91 in viable myocardium was increasing in the first 1–3 h and remained stable at the 3–4 h after injection. Conclusion: Functional SPECT imaging with ^99mTc‐HL91 and ^99mTc‐MIBI can be used to detect the seriously ischaemic but viable myocardium with a mismatched uptake character. The uptake of ^99mTc‐HL91 in the viable myocardium reached a stable level at 3–4 h after injection.