Transcript Slide 1

Myocardial Perfusion SPECT
Should NOT Be Routine in
Symptomatic Patients with
Excellent Exercise Capacity
V. Froelicher, MD
Professor of Medicine
Stanford University
VA 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
Standard ET
 ET Scores
 Score Strategy
Thallium Scintg
SPECT
Adenosine SPECT
Exercise ECHO
Dobutamine ECHO
Dobutamine Scintg
Electron Beam
Tomography (EBCT)
# of Total # Sens
Studies Patients
147
24,047 68%
24
11,788
2
>1000 85%
59
6,038 85%
16+14 5,272 88%
10+4
2,137 89%
58
5,000 84%
5
<1000 88%
20
1014 88%
16
3,683 60%
Spec Predictive
Accuracy
77%
73%
92%
85%
72%
80%
75%
84%
74%
70%
80%
88%
85%
80%
85%
80%
86%
81%
65%
Variable
Maximal Heart Rate
Circle response
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
Sum
Males
Choose
only one
per
group
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
induced Angina
Occurred =3
Reason for stopping =5
Total Score:
<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.
METs equally
important to
clinical variables
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
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
1,400,000
Office Exc Test
1,200,000
Hosp/clinic Exc Test
1,000,000
Hosp/clinic SPECT
(7X)
800,000
600,000
Office SPECT
400,000
Office Stress ECHO
(3X)
200,000
1996
1997
1998 1999
2000
Hosp/clinic Stress
ECHO
% change 1996 to 2000
Hosp/clinic SPECT
(32% Cards)
300%
250%
Office SPECT (80%
Cards)
200%
Office Exc Test (75%
Cards)
150%
100%
Hosp/clinic Exc Test
(70% Cards)
50%
0%
% change in
cardiology
% change non-Cards
Hosp/clinic Stress
ECHO (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)
1.4 mil
($984 mil)
+352 mil
889,000
($632 mil)
+126 mil