Case of the month Dr P Arumugam Consultant Nuclear Physician Nuclear Medicine Centre Central Manchester University Hospitals NHS Foundation trust

History 58 year old Female. Atypical chest pain. Status -post PCI mid LAD November 2009.LMS 50% lesion negative on IVUS. Equivocal DSE due to LBBB.

Stress /Imaging protocol Adenosine stress protocol (140mcg/kg/min over 4.5 minutes) without exercise due to LBBB. No ischaemic symptoms reported. Maximal HR 101. 2 day rest/stress with Tc- Myoview 640 MBq for stress and rest (as per BMI) Stress and rest images were acquired on GE Millennium Hawkeye 4 camera ( 120 minutes post stress due to extra cardiac activity and 70 minutes after rest injection). Images were reconstructed iteratively. Images were considered to be of good quality with no significant attenuation or scatter artefact.

Q – What is your interpretation of the perfusion study? Apparent (visual) stress induced cavity dilation. Moderate Anteroseptal reduction in perfusion post stress which completely normalises at rest ( 3 /20 segments).

Gated study screen capture

Q- What is your interpretation of the single frame captured gated study ? There appears to be reduced anterior and apical wall motion ‘post stress’ (images acquired 120 minutes post) with normal appearance at rest – ‘myocardial stunning’. There is a significant difference between post stress and resting ejection fraction, again consistent with prolonged post ischaemic stunning.

Q –What is your interpretation based on perfusion and wall motion assessment? A – Presence of reversible perfusion abnormality, reversible wall motion abnormality and drop in systolic function post stress suggests angiographically significant disease in the LAD.

Angiographic findings Patient underwent a repeat angiogram 1 month post SPECT study Reported to show proximal LAD stenosis but patent mid LAD stent. No significant LCx, RCA or LM stenosis. MDT – case discussed and being considered for single vessel CABG.

Teaching points Assessment of both perfusion and function provides additional information. Regional wall motion abnormality post stress in ischaemic segments has been described with exercise1,2 myocardial imaging due to stunning. True ischaemia is rare with vasodilator stress as it induces flow heterogeneity and hence wall motion abnormality is not expected with adenosine / dipyridamole. Steal phenomenon through collaterals is a rare exception.

In a recent publication 3 however, 1/3rd of patients had post vasodilator stress wall motion abnormalities which was proportional to the amount of ischaemia. In this patient, there is evidence of regional wall motion abnormality, elevated ESV and drop in ejection fraction post stress – all consistent with ischaemia induced LV dysfunction. This may be related to critical narrowing of the coronary artery involved 2 and may also be an indicator of multi vessel disease 4.

SPECT images are acquired 45 – 60 minutes post stress and do not reflect a true peak stress ejection fraction nor regional wall motion and in theory ,‘a resting one’. Hence some clinicians do not feel the need to perform 2 gated studies (i.e. at rest and post stress). However demonstration of wall motion abnormality several minutes post stress would be consistent with post ischemic stunning. As post stress gated information can be obtained without any additional radiation nor significant impact on throughput, it is useful to obtain this data .

References Louise Emmett et al. Reversible regional wall motion abnormalities on exercise technetium-99m–gated cardiac single photon emission computed tomography predict high-grade angiographic stenoses . J Am Coll Cardiol, 2002; 39:991-998 Sharir T, Bacher-Stier C, Dhar S, et al. Identification of severe and extensive coronary artery disease by postexercise regional wall motion abnormalities in Tc-99m sestamibi gated single photon emission computed tomography. Am J Cardiol 2000;86:1171-5. Druz et al. Postischemic stunning after adenosine vasodilator stress. Journal of Nuclear Cardiology 535 Volume 11, Number 5;534-41 Lima RS, Watson DD, Goode AR, et al. Incremental value of combined perfusion and function over perfusion alone by gated SPECT myocardial perfusion imaging for detection of severe three-vessel coronary artery disease. J Am Coll Cardiol 2003;42:64-70.