Viability assessment and its role in revascularization
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Viability assessment and its role in Revascularization. Review of evidence Dr. Nithin P G. Overview. Introduction Viability assessment by various investigations Comparisons Clinical correlations Benefits of viability assessment in clinical scenario Conclusion. Introduction. TERMS

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Viability assessment and its role in revascularization

Viability assessment and its role in Revascularization

Review of evidence

Dr. Nithin P G

Dr Nithin P G


Overview

Overview

  • Introduction

  • Viability assessment by various investigations

  • Comparisons

  • Clinical correlations

  • Benefits of viability assessment in clinical scenario

  • Conclusion

Dr Nithin P G


Introduction

Introduction

TERMS

  • ‘Stunning’

  • ‘C/C Stunning’

  • ‘Hibernation’

  • ‘Ischemic cardiomyopathy’

  • Viability???

Dr Nithin P G


Introduction1

Introduction

Viable vs Non- viable

Heart 2004;90(Suppl V):v26–v33

Dr Nithin P G


Introduction2

Introduction

33%

Contractile reserve vs. Metabolic parameters

52%

59%

59%

Heart 2004;90(Suppl V):v26–v33

Dr Nithin P G


Introduction3

Introduction

What to look for in viable tissues? [endpoints used in viability studies]

  • Improvement in regional LV function (segments)

  • Improvement in global LV function (LVEF)

  • Improvement in symptoms (NYHA functional class)

  • Improvement in exercise capacity (metabolic equivalents)

  • Reverse LV remodeling (LV volumes)

  • Prevention of sudden death (ventricular arrhythmias)

  • Long-term prognosis (survival)

Dr Nithin P G


Introduction4

Introduction

Pooled data-105 studies (n= 3,003) [Nucl. Im., DSE]

15,045 dysfunctional segments analyzed; 7,941 (53%) showed improvement in function after revasc. [84% detected prior as viable]

  • Segmental LV function

  • LVEF

  • LV volumes

  • Long-term prognosis (survival)

Curr Probl Cardiol. 2001;26:142–186

20%–30% of LV viable to allow improvement in the LVEF

Trials use criteria of >5% increase in EF

J Nucl Med 2007; 48:1135–1146

ESV ≥140 mL low improvement in LVEF post-revascularization [sens 68%; spec 65% to predict absence of global recovery]

J Thorac Cardiovasc Surg 2004;127:385-390

EDV 70% of patients with EDV 140-180 ml & 35% with EDV>180 mlimproved LVEF by 5%

Eur Heart J 2000;21:125-136

Dr Nithin P G


Viability assessment by different investigations

Viability assessment by different investigations

Dr Nithin P G


Viability assessment

Viability assessment

Nuclear imaging with PET

  • 18F-FDG tracer with oral glucose loading protocol most commonly used.

European Heart Journal (2010) 31, 2984–2995

Dr Nithin P G


Viability assessment1

Viability assessment

Ability to predict improvement in LVEF

Curr Probl Cardiol. 2001;26:142–186

J Nucl Med 2007; 48:1135–1146

J Nucl Med. 1994;35:707–715

J Nucl Med 2007; 48:1135–1146

Dr Nithin P G


Viability assessment2

Viability assessment

Viability, Trt. type & Event Rates in Pts with LVD and c/c CAD

J Nucl Med 2007; 48:1135–1146

Dr Nithin P G


Viability assessment3

Viability assessment

Nuclear imaging with SPECT

  • Tracers- 201Tl-Chloride & 99mTc-Labeled Agents [sestamibi]

    Viabilityassessment

  • Stress -Normal perfusion

  • Stress- defects with redistribution on delayed images

  • Delayed rest images or reinjection- fixed defect showing redistribution

  • Delayed rest images or reinjection- more than 50% tracer uptake

Dr Nithin P G


Viability assessment4

Viability assessment

Ability to predict improvement in LVEF

Curr Probl Cardiol. 2001;26:142–186

J Nucl Med 2007; 48:1135–1146

J Nucl Med. 1994;35:707–715

J Nucl Med 2007; 48:1135–1146

Dr Nithin P G


Viability assessment5

Viability assessment

DSE

  • Low dose- High dose dobutamine infusion best

    Viabilityassessment

  • Biphasic response- viability with superimposed ischemia

  • Worsening-severe ischemia with critical stenosis

  • Sustained improvement- subendocardial necrosis

  • No change- transmural scar

Dr Nithin P G


Viability assessment6

Viability assessment

Ability to predict improvement in LVEF

Curr Probl Cardiol. 2001;26:142–186

J Nucl Med 2007; 48:1135–1146

J Nucl Med. 1994;35:707–715

J Nucl Med 2007; 48:1135–1146

Dr Nithin P G


Viability assessment7

Viability assessment

Viability, Trt. type & Event Rates in Pts with LVD and c/c CAD

J Nucl Med 2007; 48:1135–1146

Dr Nithin P G


Viability assessment8

Viability Assessment

  • Contrast echocardiography

    • Myocardial perfusion correlate positively with microvascular density and capillary area and inversely with the extent of fibrosis

    • DSE, 201Tl imaging, and contrast echo [N=18], pts undergoing revascularization[contrast echo 89% sens., 51% spec.]

  • TDI- strain rate imaging

    • Augmentation of strain and strain rate with dobutamine is a marker of myocardial viability

    • PET detected viable segments compared with strain rate imaging during low-dose dobutamine stress test [N=37]. An increase in the longitudinal strain rate of more than -0.23 S-1 identified viable tissue [83% sens., 84% spec.]

J Am Coll Cardiol. 1997;29:985–993

J Am Coll Cardiol 2002;39:443-449

Dr Nithin P G


Viability assessment9

Viability Assessment

CMR

Viability criteria

  • End-diastolic wall thickening > 5.5 mm

  • Contrast enhanced CMR- delayed hyperenhancement

Heart 2005;91:1359–1365

 Addl. information on LVEF, LV volumes, ischaemic MR & LV shape

Heart 2005;91:1359–1365

Dr Nithin P G


Viability assessment10

Viability Assessment

DE CMR

Viability criteria

  • Increase in End-diastolic wall thickening > 2 mm

Heart 2005;91:1359–1365

Dr Nithin P G


Viability assessment11

Viability Assessment

ContrastCT

Dr Nithin P G


Comparison b w different investigations

Comparison b/w different investigations

Dr Nithin P G


Comparison

Comparison

Ability to predict improvement in LVEF

  • DSE vs. SPECT

  • Agreement b/w 60.8% - 72%

  • Segments with viability but no contractile reserve [rarely < 50% uptake but with contractile reserve]

  • 72% agreement [N=114]- 92% of segments without perfusion no contractile reserve, but 47% with perfusion also without contractile reserve

Curr Probl Cardiol. 2001;26:142–186

  • DSE vs. MRI

  • Agreement around 79%

  • More severe LV dysfunction [mean EF ~25%] and NYHA class > III have higher false negative rates with DSE

J Nucl Med 2007; 48:1135–1146

JACC 1996;28:530-535

J Am Coll Cardiol 1990;15:1021-1031

Circulation. 2002;106(suppl 1):14–18

Heart 1999;82;684-688

Dr Nithin P G


Comparison1

Comparison

DE-CMR vs 201Tl redistribution vs DSE

  • Ischemic cardiomyopathy 3 days before transplantation

  • Number of viable segments detected similar in DSE & DE CMR, but less than 201Tl, confirmed by HPE

Am J Cardiol 2002;90:455-459

Dr Nithin P G


Comparison2

Comparison

European Heart Journal (2010) 31, 2984–2995

Dr Nithin P G


Clinical correlation

Clinical correlation

Dr Nithin P G


How much viable tissue

How much viable tissue?

J Teh Univ Heart Ctr 1 (2009) 5-15

Dr Nithin P G


How much viable tissue1

How much viable tissue?

Non viable revasc- 17%

Non viable revasc- 50%

EF- 27%33%

NYHA-3.21.6

J Teh Univ Heart Ctr 1 (2009) 5-15

Dr Nithin P G


Timing of revascularization

Timing of revascularization

N=40

20+12 days

N=45

87+47 days

2 yr mort. 5%

2 yr mort. 20%

Circulation. 2003;108(suppl 1):II39–II42

Dr Nithin P G


Viability and coronary circulation

Viability and coronary circulation

Dr Nithin P G


Benefits of viability assessment

Benefits of Viability Assessment

Dr Nithin P G


Meta analysis

Meta-analysis

J Am Coll Cardiol 2002;39:1151– 8

  • Late survival with revasc. vs. medical therapy after myocardial viability testing in pts with severe CAD & LV dysfunction

  • 24 studies Thallium, PET & DSE

  • N= 3,088 (2,228 men), EF 32+8%, followed for 25+10 months

Dr Nithin P G


Meta analysis1

Meta-analysis

Dr Nithin P G


Meta analysis2

Meta-analysis

Dr Nithin P G


Meta analysis3

Meta-analysis

Drawbacks

  • Most studies very small (n < 100) Not randomized and highly selected

  • Most patients had angina; few had overt symptoms of heart failure

  • Most had only mild LV dysfunction

  • Most reported from imaging labs and surgical services

  • Decision for CABG may have been influenced by viability status

  • No (or inadequate) adjustment for key baseline variables (age, comorbidities)

  • Cohort studies carried out before modern aggressive medical therapy

Dr Nithin P G


Parr2

PARR2

  • [N=430]; EF ≤ 35% considered for revascularization, transplant, or HF work‐ up with high suspicion of CAD.

  • • Randomized patients to a PET‐guided therapy or “standard care” (no PET).

  • • Imaging physicians issued a therapy recommendation based on PET findings and treating physicians then made a decision regarding revascularization.

  • • Patients in the standard care arm had no PET, but could have another viability test, which was performed in 138 of 209 (66%) patients.

  • • Primary outcome: composite of cardiac death, myocardial infarction, or recurrent cardiac hospitalization within 1 year.

J Am Coll Cardiol 2007;50:2002-2012

Dr Nithin P G


Parr21

PARR2

Hazard ratio 0.78 [95% CI –(0.58 to1.1)] [p= 0.15]

Dr Nithin P G


Parr22

PARR2

Hazard ratio 0.62 [95% CI-(0.42 to 0.93)][p=0.019]

Dr Nithin P G


Heart trial

HEART Trial

  • RCT [N=800] symptomatic HF, EF ≤ 35%, and evidence of substantial myocardial viability to conservative vs. CAG with the intention of revascularization.

  • • Stopped early -138 pts enrolled, 69 randomized to revascularization, but only 45 underwent a procedure.

Eur J Heart Fail 2011;13:227-33

Dr Nithin P G


Heart trial1

HEART Trial

A conservative management strategy may not be inferior to one of coronary arteriography with the intent to revascularize in patients with HF, LV systolic dysfunction, and extensive myocardial viability

Dr Nithin P G


Viability assessment and its role in revascularization

N Engl J Med 2011;364:1617-25

  • The first prospective randomized trial testing the hypothesis that CABG improves survival in patients with ischemic LV dysfunction [EF-26.7%±8.6] compared to outcome with aggressive medical therapy

  • Myocardial viability identifies patients with CAD and LV dysfunction who have the greatest survival benefit with CABG compared to aggressive medical therapy

Dr Nithin P G


Stich trial substudy

STICH Trial- substudy

  • All pts eligible for viability testing with SPECT [Tl or Tc] or DSE

    • Viability testing optional

    • Criteria for myocardial viability were prospective and pre- specified [SPECT (11/17); DSE (5/16)]

  • Primary endpoint:

    • All cause mortality

  • Secondary endpoints:

    • Mortality plus cardiovascular hospitalization

    • Cardiovascular mortality

Dr Nithin P G


Viability assessment and its role in revascularization

1212

Patients with viability test

Patients with no viability test

618

594

Unusable test

17

Pateints with no usable viability test

611

Patients with usable viability test

601

150

321

130

DSE

471

Viable

Non-Viable

SPECT 471

487

114

243

60

54

244

MED

49.9%

MED

52.6%

CABG 47.4%

CABG 50.1%

Dr Nithin P G


Stich trial substudy1

STICH Trial- substudy

After multivariate analysis p=0.21

Dr Nithin P G


Stich trial substudy2

STICH Trial- substudy

Dr Nithin P G


Stich trial substudy3

STICH Trial- substudy

  • Substudy of a major trial

  • Viability study according to the judgement of physician

  • Small number of non viable group for comparison

  • Sx influenced by timing and results of viability test

  • Two types of viability tests-SPECT & DSE

  • Better medical therapy available

  • Combined procedure [CABG + SVR] done probably not optimum

    In patients with CAD and LV dysfunction, assessment of myocardial viability does not identify patients who will have the greatest survival benefit from adding CABG to aggressive medical therapy

Dr Nithin P G


Conclusions

Conclusions

Dr Nithin P G


Conclusions1

Conclusions

  • Limitations in study design and test inaccuracies -prevented the detection of a true interaction b/w viability & benefit of revascularization

  • Advances in medical therapy markedly reduced the added benefit of revascularization

  • The critical information may not lie in the presence but rather in the absence of viability.

  • The benefit of CABG may only be related to revascularization of potentially ischemic segments.

  • The greatest benefit of CABG may be limited to those patients with more advanced forms of the disease[those with relatively small amount of viable myocardium]

Dr Nithin P G


Conclusions2

Conclusions

  • Currently available evidence does not support the use of viability testing as the arbitrator in the decision making process regarding revascularization in ischemic cardiomyopathy

  • Ischemic cardiomyopathy [heterogeneous population] multiple factors play important prognostic role. Viability alone cannot provide an unequivocal answer

  • Prospective trials demystify the emphasis previously placed – without appropriate evidence‐‐ in the significance of myocardial viability

  • These observations urge physicians to consider the multiplicity of factors involved in the decision making process in this complex population of patients.

Dr Nithin P G


Thank you

Thank you

Dr Nithin P G


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