Myocardial Perfusion SPECT Should NOT Be Routine in Symptomatic Patients with

Excellent Exercise Capacity

V. Froelicher, MDProfessor of MedicineStanford UniversityVA Palo Alto HCS

Myocardial Perfusion SPECT Should NOT Be Routine in Symptomatic Patients with

Excellent Exercise Capacity

For simplicity sake let us avoid the philosophical issues regarding this:

• no test should be routine for all patients

• clinical judgment and the art of medicine (incldg patients own desires and needs) should be foremost in the decision to test or not to test.

• Quality of life issues: “are you able to do everything you want to do?”

Myocardial Perfusion SPECT Should NOT Be Routine in Symptomatic Patients with

Excellent Exercise Capacity

Assumptions:

• Symptoms equal chest pain

• Exercise capacity obtained from an exercise test.

• Excellent exercise capacity => 10 METs

What are the Questions being asked?

• Are these symptoms due to Coronary Disease?

• Do these symptoms put this patient at high risk for a Cardiac Event?

• Is a invasive intervention appropriate?• If due to CAD, what is the culprit

lesion?• Does the baseline ECG invalidate ST

analysis?

Regarding 2 of the Questions:

• If due to CAD, what is the culprit lesion?– ST depression does not localize, ST

elevation does but rare … Then yes, SPECT needed

• Does the baseline ECG invalidate ST analysis?– More than one mm ST depression, LBBB,

WPW, IVCD, paced rhythm …. Then yes, SPECT is needed

The other Questions• Are these symptoms due to Coronary

Disease?– If no resting ECG abnormalities and

scores used the exercise ECG sufficient … then No, SPECT not needed

• Do these symptoms put this patient at high risk for a Cardiac Event?– DTS and other prognostic scores

sufficient … then No, SPECT not needed

• Is an invasive intervention appropriate?

Comparison of Tests for Diagnosis of CAD

Grouping # of Studies

Total # Patients

Sens Spec Predictive Accuracy

Standard ET 147 24,047 68% 77% 73% ET Scores 24 11,788 80% Score Strategy 2 >1000 85% 92% 88%

Thallium Scintg 59 6,038 85% 85% 85% SPECT 16+14 5,272 88% 72% 80% Adenosine SPECT 10+4 2,137 89% 80% 85% Exercise ECHO 58 5,000 84% 75% 80% Dobutamine ECHO 5 <1000 88% 84% 86% Dobutamine Scintg 20 1014 88% 74% 81% Electron Beam Tomography (EBCT)

16 3,683 60% 70% 65%

Variable Circle response

Sum

Maximal Heart Rate Less than 100 bpm = 30

100 to 129 bpm = 24

130 to 159 bpm =18

160 to 189 bpm =12

190 to 220 bpm =6

Exercise ST Depression

1-2mm =15

> 2mm =25

Age >55 yrs =20

40 to 55 yrs = 12

Angina History Definite/Typical = 5

Probable/atypical =3

Non-cardiac pain =1

Hypercholesterolemia?

Yes=5

Diabetes? Yes=5

Exercise test Occurred =3

induced Angina Reason for stopping =5

Total Score:

MalesChoose

only one per

group

<40=low prob

40-60= intermediate probability

>60=high probability

Duke Treadmill Score (uneven lines)

Kaplan-Meier Survival curves for the “all-comers” prognostic score.

SCORE = (1=yes, 0=no)

METs<5 + Age>65 + History of CHF + History of MI or Q wave

a=0, b=1, c=2, d=more than 2

METs equally important to

clinical variables

Most pertinent: Snader CE, Marwick TH, Pashkow FJ, Harvey SA, Thomas JD, Lauer MS.JACC 1997;30(3):641-8 Cleveland Clinic: Importance of estimated functional capacity as a predictor of all-cause mortality among patients referred for exercise perfusion: 3,400 patients

CONCLUSIONS: In this clinically low risk group, estimated functional capacity was a strong and overwhelmingly important independent predictor of all-cause mortality among patients undergoing exercise Tl-201 SPECT testing.

Next Most pertinent: McCully RB, Roger VL, Mahoney DW, Burger KN, Click RL, Seward JB, Pellikka PA. J Am Coll Cardiol 2002 Apr 17;39(8):1345-52 Outcome after abnormal exercise echo for patients with good exercise capacity.

Methods: 1,874 patients with CAD who had good exercise capacity but abnormal exercise ECHOs; cardiac events (cardiac death or nonfatal MI).

CONCLUSIONS: ECHO descriptors of the extent and severity of exercise-related LV dysfunction were of independent and incremental prognostic value. Stratification of patients into low- and higher risk subgroups was possible.

Ventilatory (VO2) Cardiac Output x a-v O2 Difference

VE x (% Inspired Air Oxygen Content - Expired Air Oxygen Content)

External Work Performed

What is a MET?

Metabolic Equivalent Term

1 MET = "Basal" aerobic oxygen consumption to stay alive = 3.5 ml O2 /Kg/min

By convention just divide ml O2/Kg/min by 3.5

Key MET Values (part 1)

1 MET = "Basal" = 3.5 ml O2 /Kg/min

2 METs = 2 mph on level

4 METs = 4 mph on level

< 5METs = Poor prognosis if < 65; limit immediate post MI; cost of basic activities of daily living

Key MET Values (part 2)

♥ 10 METs = As good a prognosis with medical therapy as CABS

♥ 13 METs = Excellent prognosis, regardless of other exercise responses

♥ 16 METs = Aerobic master athlete

♥ 20 METs = Aerobic athlete

Importance of METs

10 to 15% increase in survival per MET

Can be increased by 25% by a training program

Medicare Reported Tests

-

200,000

400,000

600,000

800,000

1,000,000

1,200,000

1,400,000

1996 1997 1998 1999 2000

Office Exc Test

Hosp/clinic Exc Test

Hosp/clinic SPECT(7X)

Office SPECT

Office Stress ECHO(3X)

Hosp/clinic StressECHO

% change 1996 to 2000

0%

50%

100%

150%

200%

250%

300%

% change incardiology

% change non-Cards

Hosp/clinic SPECT(32% Cards)

Office SPECT (80%Cards)

Office Exc Test (75%Cards)

Hosp/clinic Exc Test(70% Cards)

Hosp/clinic StressECHO (75% Cards)

Office Stress ECHO(80% Cards)

Cause of change in Practice?

$Not reimbursement but obvious superiority or impression of superiority of other testing

$“The Doctor does the test he gets paid (the most) for” … the Doctor’s Dilemma, GB Shaw, 1926

$Are we getting our monies worth???

Medicare Costs and Savings(response to drop in TM reimbursement from $350 to $150)

1994 1998 Change cost

Treadmill test 875,000

($307 mil)

533,000

(80 mil)

-227 mil

Nuclear Perfusion

(5-7x cost)

889,000

($632 mil)

1.4 mil

($984 mil)

+352 mil

+126 mil