Noninvasive Imaging to Assess Viability

Noninvasive Imaging to Assess Viability

Christopher L. Hansen, MD

Professor of Medicine and Radiology

Thomas Jefferson University Hospital

Current Issues in Coronary and Structural Heart Disease

October 3, 2015

Myocardial ViabilityMyocardial Viability

• Clinically important problem– Epidemic of coronary disease

– Increasing incidence of heart failure

– Growing cohort of revascularized patients

• Difficult problem to address– What is viability?

• Myocardium that is alive?

• Myocardium that improves with revascularization?

• Non ischemic causes of heart failure– Not expected to improve with revascularization

• Effect on functional capacity and survival

Myocardial ViabilityMyocardial Viability

• Stunned myocardium– Based on animal models– Transient decrease in function due to ischemic

insult– Generally implies that the ischemia has resolved

• Hibernating myocardium– Compensatory down regulation of function due to

chronic ischemia– Implies the ischemia is ongoing

• Clinical overlap– Some studies suggest hibernation is just repeated

stunning

Effects of Myocardial StunningEffects of Myocardial Stunning

Canine model15’ occlusion of mid LAD Infarction excluded histologicallyCharlat, et al. JACC 1989; 13:185-94

Systolic Function Diastolic Function

Hibernating MyocardiumHibernating Myocardium

Rahimtoola, SH Circ. 1982; 65:225

What Are We Really Looking For?What Are We Really Looking For?

• Viable– Still alive, i.e. not scar

– No promise that it will improve with revascularization

• Recoverable– Function likely to improve with

revascularization

Hibernating MyocardiumHibernating Myocardium

• Two conditions– Still alive, i.e. not necrotic

– Resting hypoperfusion

• Most tests in isolation answer one question– Need more than one test to establish both

conditions

Change in EF Post RevascularizationChange in EF Post Revascularization

• Surrogate endpoints– Methodologically weaker

– Easier to perform study

– Cheaper to perform study

• Is change in EF post revascularization a meaningful endpoint?

Effect of Change in EF on SurvivalEffect of Change in EF on Survival

Samady, Circ 100:1298; 1999

• 104 pts isch CMP survived CABG & had pre & post EF– 68 EF ≥ 5%

– 36 no improvement

• Followed 32±23 mos

• No difference in survival

Tests For ViabilityTests For Viability

• Thallium-201– Reinjection (not used)

– Rest/Redistribution protocol

• PET– FDG

• Dobutamine echo

• MRI– Late enchancement with gadolinium

24 Hour Thallium Imaging

24 Hour Thallium Imaging

ASA MSA BSA

Stress

Delay

24 Hour

71 year old man with a history of hypertension, presented with a non-Q wave MI. Completed submaximal protocol without chest pain or ST segment changes.

J.A. 7/89

RAO of Left Coronary ArteryJ.A. 7/89

Area of Detail

MyocardialViability with

Thallium Reinjection

MyocardialViability with

Thallium Reinjection

Stress

24° Reinjection

Delay61 year old woman with a history of

HTN, DM and hypercholesterolemia. She had undergone a PTCA of the RCA at another institution 8 days earlier. She was admitted with chest pain and ruled in for a non-Q wave MI. She was stopped in Bruce 0 of a submaximal protocol because of achievement of target HR. She had no chest pain or ST changes.

KW 2/93

201Tl vs Mibi for Viability201Tl vs Mibi for Viability

Udelson, Circulation 89:2552; 1994

18FDG in Hibernating Myocardium18FDG in Hibernating Myocardium

Fasting Insulin Clamp

Mäki, et al Circulation 93:1658-1666; 1996

• 7 patients with coronary occlusion but no MI

• Glucose metabolism compared in normal and hibernating regions fasting and after insulin clamp

• Fasting Metabolism:– 15±10 µmol/100g•min (H)

– 11±10 µmol/100g•min (N)

• Insulin Clamp:– 72±22 µmol/100g•min (H)

– 79±21 µmol/100g•min (N)

• FA decreased from 670±170 µmol/L fasting to 70±30 µmol/L clamp

Myocardial Viability Using 18FDGMyocardial Viability Using 18FDG

• 17 patients undergoing CABG

• Wall motion analysis before and after CABG

• Uptake of FDG predicted viability

• 85% (35/41) with uptake of FDG improved

• 92% (24/26) without uptake of FDG did not improve

• 54% of regions with Q waves improved after CABG

Tillisch, et al. NEJM 1986; 314:884-8

A. Normal PatternB. Discordant uptake--viableC. Concordant uptake--not viable

Thallium Reinjection vs. 18FDGThallium Reinjection vs. 18FDG

• 16 patients• All had fixed defects at

3 hours• FDG and 15O labeled

H2O used with PET• FDG uptake correlated

with severity of fixed thallium defects

– 91% in mild defects

– 84% in moderate– 51% in severe

• FDG and Reinjection Tl were concordant in 88% of cases

Bonow, et al. Circulation 1991; 83:26-37

Viability by CMRIViability by CMRI

Shan, Circ 109:1328; 2004

Viability and Response to RxViability and Response to Rx

Allman, J Am Coll Cardiol, 39:1159; 2002

• Meta-analysis

• 24 Studies– 201Tl

– 18FDG

– Dobutamine Echo

• 3,088 pts– EF 32±8%

– Followed 25±10 mos

Viable Non-viable

p < 0.001

p = 0.23

Viability and PrognosisViability and Prognosis

Bonow N Engl J Med 2011;364:1617

• Stich Trial

• 1212 pts– Rand. Med v

CABG

– EF < 35%

– No LM

– No USA

• Viability– Optional

– Done in ~50%

– Tl, Mibi or DE

Viability and PrognosisViability and Prognosis

Bonow N Engl J Med 2011;364:1617

Medical vs Surgical TherapyMedical vs Surgical Therapy

Killip, Circulation 72V:102; 1985

3 Vessel CAD & EF < 50%

Open ArteryHypothesisOpen ArteryHypothesis

Kaul, Circulation, 92:2790-2793; 1995

Open Artery Hypothesis--OAT TrialOpen Artery Hypothesis--OAT Trial

Hochman, NEJM, 355:2395; 2006

• 2188 high risk pts– 3-28 days post MI

– EF < 50%

– Proximal occlusion

– 1082 PCI & Med Rx

– 1084 Med Rx

• Endpoints– Death

– MI

– FC IV CHF

Approach to the PatientApproach to the Patient

• What is the problem?– Ischemia

– Heart failure

• Extent & Severity of defects– The worse it is…

– …the worse it is

• Chamber size– Coexistent non ischemic processes