Viability assessment final new
Three key methods are used to identify myocardial viability non-invasively: echocardiography, single photon emission computed tomography (SPECT), and positron emission tomography (PET). Echocardiography techniques include dobutamine stress echocardiography to detect contractile reserve, myocardial contrast echocardiography to assess perfusion, and adenosine speckle tracking stress echocardiography. SPECT involves radioactive tracers like thallium-201 or technetium to identify preserved membrane integrity or improved uptake. PET assesses glucose metabolism, which can be preserved in hibernating myocardium despite reduced flow.
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Viability assessment final new
- 1. ASSESSMENT OFVIABILITY: which testfor whom ? PRESENTED BY – DR SIVANAND PATEL (DM CARDIOLOGY – MAMC & GB PANT , NEW DELHI )
- 2. Mechanisms of acuteand chronic adaptation to a temporary or sustained reduction in coronary blood flow include • Stunning • Hibernation • Ischemic preconditioning Braunwald’s Heart Disease_ A Textbook of Cardiovascular Medicine (2018, Elsevier) 11th edition ch 16 page 291 -294
- 3. Stunned myocardium • Observedafter transient period of ischemia followed by reperfusion (depressed function at rest but preserved perfusion) • Regional myocardial function remains depressed for up to 6 hours after resolution of ischemia following a 15-minute occlusion in the absence of tissue necrosis • Observed soon after coronary occlusion and reperfusion in the setting of acute MI. Braunwald’s Heart Disease_ A Textbook of Cardiovascular Medicine (2018, Elsevier) 11th edition ch 16 page 291 -294
- 4. Hibernating myocardium • Adaptiveresponse of myocardium to chronic or repetitive episodes of ischemia resulting in reduced myocardial function at rest (depressed function at rest and decreased perfusion) • Hibernation and stunning coexist Braunwald’s heart disease_ a textbook of cardiovascular medicine (2018, elsevier) 11th edition ch 16 page 291 -294
- 5. Myocardial Viability • Requirementsfor cellular viability include (1) sufficient myocardial blood flow (2) cell membrane integrity (3) preserved metabolic activity Braunwald’s Heart Disease_ A Textbook of Cardiovascular Medicine (2018, Elsevier) 11th edition ch 16 page 291 -294
- 6. Key non invasivemethods to identify viability • 1.Echocardiography • 2.Single Photon Emission Computed Tomography • 3.Positron Emission Tomography • 4.Magnetic Resonance
- 7. Echocardiography Major techniques employedinclude: • Dobutamine stress • Myocardial contrast • Adenosine speckle tracking stress echocardiography Assessment of Myocardial Viability: A Review of Current Non Invasive Imaging Techniques Ahmed talib et al march 2014
- 8. Echocardiography Resting echo: Diastolicwall thickness >= 6 mm supports viability Stress Echo: • Commonly used criterion to identify viable myocardium is by detection of contractile reserve • Stress achieved by using dobutamine, adenosine or dipyridamole • An infusion of low-dose dobutamine (5–10 mg/ kg/min) results in increased contractile function of viable segments whereas nonviable ones do not show such response • Myocardial viability can also be detected when using the biphasic response (enhanced activity at low dose dobutamine suggesting viability and reduced function at high dose dobutamine suggesting ischemia) Assessment of Myocardial Viability: A Review of Current Non Invasive Imaging Techniques Ahmed talib et al march 2014
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- 17. • Diagnostic accuracyof dobutamine echocardiography reduces with increasing severity of regional and global LV dysfunction • That is, the technique underestimates the extent of viability: 39% of all recovering LV segments failed to exhibit inotropic contractile reserve Pagano et al. Heart 1998;79:281-288 • Low-dose dobutamine failed to identify 45% of segments that ultimately regained function 6 month post revascularisation (poor sensitivity) • At the same time, specificity for identification of viability >90% Wiggers et al. Am. Heart. J. 2000, 140, 928– 936.
- 18. • Hence, whileevidence of viability on DSE is a strong predictor of likelihood of recovery post-revascularisation; absence of viability especially in severe LV dysfunction patients may not accurately predict those who will not benefit from revascularisation
- 19. CONTRAST ECHOCARDIOGRAPHY • Useintravenous micro-bubble contrast • Demonstrate viability qualitatively • Micro-bubbles are inert gases and stay in the vascular space behave like red blood cells • Segments that have normal or patchy perfusion - viable no perfusion - non-viable Assessment of Myocardial Viability: A Review of Current Non Invasive Imaging Techniques Ahmed talib et al march 2014
- 20. Wolfgang Lepper. Circulation.Myocardial Contrast Echocardiography, Volume: 109, Issue: 25, Pages: 3132-3135, DOI: (10.1161/01.CIR.0000132613.53542.E9)
- 21. ADENOSINE SPECKLE TRACKING •With adenosine stress Viable segments - increase their longitudinal strain Non-viable – Unchanged Ran H,et al. Clinic value of Two-Dimensional Speckle Tracking Combined with Adenosine Stress Echocardiography for Assessment of Myocardial Viability.Echocardiography 2012;29:688-94.
- 22. Limitation and advantages •Limitations of echocardiography ; • Operator dependence, both in data acquisition, and interpretation, • Adequate acoustic window acquisition - has greatly improved by using contrast agents. • Advantages of stress echocardiography • Good validity, • Wide availability, • Cost effectiveness, • Lack of ionizing radiation, and • Being friendly with implanted devices. Assessment of Myocardial Viability: A Review of Current Non Invasive Imaging Techniques Ahmed talib et al march 2014
- 23. Prognostic value • TheVIAMI-trial (2012), Viability-Guided Angioplasty After Acute Myocardial Infarction RCT • Investigating a viability-guided invasive approach in • 261 patients recruited • At least 48 hours after an acute MI who then underwent LDDE for the • Detection of viability within 72 hours of MI • Those with a viable myocardium randomized to invasive or conservative treatment • The primary endpoint was the composite of death from any cause, recurrent MI and unstable angina at 1-year follow-up. • An invasive approach in patients with a high viability score had a substantial reduction in ischemic events vis-à-vis conservative strategy • Patients with low / no viable myocardium had low recurrent ischemia rates despite conservative strategy Assessment of Myocardial Viability: A Review of Current Non Invasive Imaging Techniques Ahmed talib et al march 2014
- 24. SPECT • Administration ofa radioactive tracer - thallium-201 or technetium Tc-99m (sestamibi & tetrofosmin) • Criterion for viable myocardium: • Tracer activity of >50% and • Redistribution of >10% in dysfunctional segments used as markers of viability as a consequence of preserved membrane integrity (detected by thallium SPECT) • Tracer activity of >50% and improvement in tracer uptake after nitrates administration is also taken as a markers of viability (as detected by technetium SPECT). Assessment of Myocardial Viability: A Review of Current Non Invasive Imaging Techniques Ahmed talib et al march 2014
- 25. Standard SPECT imagingdisplay. A, The short-axis images represent a portion of the anterior, lateral, inferior, and septal walls. B, Vertical long-axis images represent the anterior wall, apex, and inferior wall. C, Horizontal long-axis images represent the septum, apex, and lateral walls.
- 26. Imaging Protocols forAssessmentof Myocardial Viability • Presence of 201Tl after redistribution implies preserved myocyte cellular viability • After 201Tl reinjection, approximately 50% of regions with fixed defects on stress-redistribution imaging show significant enhancement of 201Tl uptake -> improvement in regional LV function . • The presence of a severe 201Tl defect after reinjection -> very low probability of improvement in function . Assessment of Myocardial Viability: A Review of Current Non Invasive Imaging Techniques Ahmed talib et al march 2014
- 27. 201Tl rest redistribution •Here we compare images between 3- to 4-hour versus 15- to 20- minute images. • Identification of a "reversible resting defect” reflects preserved viability • Less sensitive but specific sign of potential improvement in regional function (good when shows viability)
- 28. 201Tl reinjection • Ifseverely hypoperfused, initial uptake very low & Redistribution depends on the continued delivery of the tracer over the 3–4 hr period • If blood concentration of tl- 201 decreases rapidly a fixed defect may be seen due to insufficient delivery of the tracer (false negative for viability) • Second low dose rest injection of thallium with delayed imaging after this repeat injection will give myocytes with reduced perfusion the opportunity to sequester thallium and unmask severely hypoperfused viable tissue.
- 29. Late redistribution images •Third set of images at 24 hours • Allow for redistribution of the tracer to very ischemic (yet viable) tissue • It has been shown that 22% of fixed defects (at early redistribution imaging) demonstrate normal tl-201 uptake at later redistribution • This may indicate a poorly perfused, yet viable region (increased sensitivity for viability prediction) Wu KC, et al. Noninvasive Imaging of Myocardial Viability: Current Techniques and Future Developments. Circulation Research. 2003;93(12):1146-58.
- 30. 99mTc-sestamibi and tetrofosmin Performance99mtc similar to 201tl. • Do not share redistribution properties of 201tl • Normal uptake -> preserved viability; • Moderate reduction in uptake is -> admixture of viable and infarcted tissue; and • Severe defect -> infarct. • Administration of nitrates to improve blood flow at rest before injection of sestamibi appears to improve ability of these tracers to detect myocardial viability Assessment of Myocardial Viability: A Review of Current Non Invasive Imaging Techniques Ahmed talib et al march 2014
- 31. Limitation and advantages Themain limitations of SPECT include • higher cost compared to echocardiography, • limited spatial resolution, • potential difficulty in interpreting results in patients with balanced myocardial ischemia (3-vessel disease) • risk of radiation. The main advantages include • extensive validation, • increasing availability, • good sensitivity and • lower cost compared to PET Assessment of Myocardial Viability: A Review of Current Non Invasive Imaging Techniques Ahmed talib et al march 2014
- 32. INFARCT STRESS INDUCEDISCHAEMIA
- 33. PET PERFUSION IMAGING IMAGINGOF GLUCOSE METABOLISM. Principle : -> glucose utilization may be preserved or increased relative to flow in hypoperfused but viable (hibernating) myocardium, termed metabolism perfusion mismatch. -> Myocardial glucose use is absent in scarred or fibrotic tissue, represented by metabolism-perfusion match
- 37. PET- Prognostic value •A meta-analysis by Beanlands et al of 10 studies involving 1046 patients, found that, the mortality rate was higher in those who did not undergo revascularization despite a PET scan confirming significant myocardial viability. • The annual death rate was 4% in those that had revascularization versus 17% in those who did not undergo revascularization. Beanlands RS, et al. Delay in revascularization is associated with increased mortality in patients with severe left ventricular dysfunction and viable myocardium. Circulation 2010: 108: 1151-6
- 38. SPECT VS FDGPET • Brunken et al published data from a comparison of tomographic thallium images with PET images; 47% of the irreversible thallium defects were identified as viable on PET images Circulation. Nov 2002;96(5):1357-69. • Tamaki et al subsequently confirmed these findings in 2 comparative studies of SPECT and PET in which 38-42% of the irreversible thallium defects had enhanced FDG uptake suggestive of viable myocardium. Am J Cardiol. Oct 2009;104(14):860-5
- 39. The Combined Valueof Perfusion/Metabolism PET • Combination of perfusion PET and FDG PET - gold-standard for the identification of hibernating myocardium; • Region with low perfusion reserve by 13NH3 despite normal FDG uptake is highly predictive of both functional recovery and survival post-revascularization.
- 40. Limitation and advantages Mainlimitations of PET include • high cost, • limited availability • the use of radio-active tracers Main advantages include • established validity • excellent sensitivity • Use in severe LV dysfunction as well as balanced ischemia • Compared with SPECT, PET has better spatial and temporal resolution, with better quality pictures and less radiation
- 41. MAGNETIC RESONANCE IMAGING Gd-DTPAresults in contrast enhancement by reducing the T1 of tissue in a concentration dependent fashion Healthy cells exclude Gd-DTPA and therefore this agent is restricted to the extravascular and interstitial spaces MRI modalities for viability assessment: • Delayed enhancement (DE), known as late-gadolinium enhancement (LGE) • Dobutamine stress (DS-MRI) and • End-diastolic wall thickness (EDWT)
- 42. Cardiovascular Magnetic ResonanceImaging • From early CMR studies: • End-diastolic wall thickness of 5.5 mm or more and Dobutamine-induced systolic wall thickening of 2 mm or more have excellent sensitivity and specificity in the prediction of segmental contractile recovery after revascularization • Transmural extent of myocardial scar depicts a progressive stepwise decrease in functional recovery despite successful coronary revascularization, especially in myocardial regions of akinesia or dyskinesia.
- 43. DE/LGE techniques ->myocardial perfusion and tissue enhancement by i.v. administration of gadolinium chelated contrast • After 5min of contrast agent images are acquired which show regions of myocardial infarction exhibiting high signal intensity i.e. high contrast enhancement. • This hyperenhancment is larger in scar tissue/non viable myocardium, than in normal viable myocardium and correlates inversely with functional recovery of the myocardium following revascularization.
- 46. AKINETIC SEGMENT SCAR ONMRI NON VIABLE SCAR AND AKINESIS WAS PERSISTENT POST REVASCULARISATION IRREVERSIBLE DYSFUNCTION
- 47. Limitation and advantages •The main limitations of CMR include; • high cost, • long study time, • requirement for breath-holding sequences and restrictions in patients with implant devices and impaired renal function. • However, advances in MRI technology are holding promises to reduce imaging time, increase spatial resolution and adapt to scan implanted devices. • The main advantages of CMR include • excellent anatomical details using steady state free precision (SSFP) cine sequences in EDWT, • good sensitivity/specificity with good interobserver/intraobserver agreement in DE imaging, and • excellent sensitivity offered with DS.
- 48. Prognostic value • Gerberet al studied 144 patients with ischemic lv dysfunction who had undergone DE imaging , then either received revascularization with PCI or CABG or were managed conservatively • It demonstrated good prediction of survival, which was significantly lower in patients who did not undergo revascularization. Gerber BL, et al. Prognostic value of myocardial viability by delayed enhanced magnetic resonance in patients with coronary artery disease and low ejection fraction: impact of revascularization therapy. JACC. 2012;59(9):825-35.
- 49. Meta-analysisdemonstratingoutcomeofpatientswithischemicleft ventriculardysfunctionafterviabilitytesting Gerber BL, etal. Prognostic value of myocardial viability by delayed enhanced magnetic resonance in patients with coronary artery disease and low ejection fraction: impact of revascularization therapy. JACC. 2012;59(9):825-35.
- 50. Comparison of ImagingTechniques for ViabilityAssessment • Dobutamine echocardiography is more specific and PET / CMR techniques have better accuracy • For patients with more severe LV dysfunction, in whom thinner myocardial walls are often present, an advantage of PET and CMR is their better spatial resolution for imaging thinner objects.
- 51. Ahmed talib etal march 2014
- 53. Conclusion • The recommendedapproach to assess myocardial viability begins with either dobutamine echocardiography or radionuclide myocardial perfusion imaging, depending upon availability . • With severe LV dysfunction and triple vessel disease, PET / CMR more suitable even as initial strategy • Before labelling a not-obviously scarred myocardial segment (echo diastolic thickness >= 6mm) as non-viable based on stress echo alone, testing with more sensitive modalities warranted • Hence, viable on DSE ----- Revascularise • Not viable on DSE (and not obviously scarred) ----- Assess further
- 54. Markers of ViableMyocardium
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- 56. ACC/AHA/ASNC Guidelines forthe Clinical Use of Cardiac Radionuclide Imaging—Executive Summary A Report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (ACC/AHA/ASNC Committee to Revise the 1995 Guidelines for the Clinical Use of Cardiac Radionuclide Imaging) ( Circulation. 2003;108:1404–1418.)