Case of the month

Dr P ArumugamConsultant Nuclear Physician

Nuclear Medicine CentreCentral 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?• A –

– 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 ?

• A- – 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 .

References1. 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

2. 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.

3. Druz et al. Postischemic stunning after adenosine vasodilator stress. Journal of Nuclear Cardiology 535 Volume 11, Number 5;534-41

4. 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.