Some Key questions regarding myocardial viability, its relevance and techniques for assessment.

1. Dr. Muhammad Ayub, FCPS
Diplomate Certification Board of Nuclear Cardiology
Diplomate Board of Cardiovascular Computed Tomography
Assistant Professor of Cardiology

2. Myocardial Viability
Key questions
 What is Viable Myocardium?
 Why to Detect?
 What can it predict?
 How to Detect?
 Which technique is better?

3. Viable Myocardium
 Normal
 Reversible Ischaemia
 Partial Thickness Infarction
 Partial Thickness Infarction + Ischaemia
 Hibernating
 Stunning

4. Why to Detect?
• Ischemic LV dysfunction is common cause of cardiac failure
resulting in bad prognosis.
• Patients with ischemic LV dysfunction and viable myocardium
often improve after revascularization.
• Numerous studies have suggested that identification of
viable myocardium also predicts improved survival following
revascularization

5. What it can predict?
Viability and Prognosis
Based on 20 Studies (n=2362)
Viable Myocardium Scarred Myocardium

6. Myocardial Viability and Cardiovascular Mortality
1.0
Without viability
With viability
Univariate Multivariable
0.8
Cardiovascular Mortality Rate
HR 95% CI P Chi-square p value Chi-square p value
0.61 0.44,0.84 0.003
8.81 0.003 0.91 0.339
0.6
0.4
0.2
0.0
0 1 2 3 4 5 6
Years from Randomization
Without viability 114 99 85 80 63 36 16
With viability 487 432 409 371 294 188 102

7. How to Detect viable Myocardium?
Physiological Basis
Contractile Reserve
Preserved Cellular Metabolism
Cell Membrane Integrity

8. Contractile Reserve
Dobutamine Stress Echocardiography
Gated Myocardial Perfusion SPECT
Dobutamine MRI

9. Dobutamine Echocardiography

10. Biphasic response to Dobutamine

11. Stress Echocardiography
Studies= 19 (n=448)
Sensitivity: 84%
Specificity: 81%

12. Contractile Reserve with Gated SPECT for
Myocardial Viability
Both perfusion and wall
motion detection.
LV EF and ventricular
volumes calculation.
3-D display of endocardial,
epicardial or of both.
Regional quantitation by its
polar map system.

13. GSPECT with Low Dose Dobutamine
 Baseline GSPECT study
 Low dose dobutamine SPECT study
 Areas with contractile reserve – Viable
 Areas without contractile reserve -- Scar

14. Preserved Cell Metabolism
Glucose F-18 FDG
Free Fatty Acids I-123 BMIPP
C-11 Palmitate
C-11 Acetate

15. PET Perfusion and Metabolism
Perfusion
Metabolism

16. PET Perfusion /Metabolism Mismatch
Ghosh N et al. Eur Heart J 2010;eurheartj.ehq361

17. PET Perfusion /Metabolism Match
Ghosh N et al. Eur Heart J 2010

18. F-18 FDG PET
Studies= 11 (n=332)
Sensitivity: 88%
Specificity: 73%

19. Cell Membrane Integrity
 Imaging of choice, where PET is not available.
 Thallium (Tl -201 ) or Tc-99m MIBI are commonly
radioisotopes used for this purpose.
 Cellular uptake of Tl-201 and Tc-99m Sestamibi is
dependant on intact cell membrane.

20. Protocol of Tl-201 for HM
Stress, redistribution, and 24 hours delayed imaging.
Stress, redistribution, and reinjection imaging.
Stress, immediate reinjection, and redistribution imaging.
Rest and redistribution imaging.

21. Rest Redistribution Tl-201 SPECT

22. Rest Redistribution Tl-201 SPECT
Scar Myocardium

23. Tc-99m MIBI
 Second most commonly used perfusion agent.
 It enters passively through the cell membrane.
 Concentration in cytosol is 5:1, whereas it increases
up to 300:1 in mitochondria.
 Tc-99m Sestamibi does not redistribute after initial
uptake
 Administration of nitrates prior to Sestamibi
injection improves uptake in viable areas

24. Nitrates and Viability

25. Other Agents
 Trimetazidine
 Tricardin
Improvement with administration of nitrates as well as trimetazidine

26. Comparison of various techniques for the prediction of
recovery of regional function after revascularization.
Ghosh N et al. Eur Heart J 2010

27. Cardiac MRI for myocardial viability
 One of the non-invasive technique for viability.
 High spatial and temporal resolution
 Significant concordance between Gated MRI and
post-revascularization findings.

28. MR Assessment of Myocardial Viability
N Myocardium
Gd
injection
infarct
1st pass Delayed time
enhancement

29. MDCT for Myocardial Viability

30. Final word
 All available techniques have good sensitivity and
specificity for detection of myocardial viability.
 Techniques using contractile reserve are more specific
but nuclear techniques are sensitive for assessment of
myocardial viability.