This document defines transient ischemic dilation (TID), which is the ratio of left ventricular size at stress compared to rest. The study found that the end-systolic volume ratio (ESVr) correlated most strongly with myocardial ischemia. Optimization analysis determined that a formula weighting the end-systolic volume by a factor of 5 provided the highest correlation between TID and ischemia. Therefore, the "complex average" that TID represents can be best described as stress (ESV x 5 + EDV) / rest (ESV x 5 + EDV).

2. Necessity is the Mother of Invention.
- Plato
The Bitterroot Mountains From Kellogg Peak

3. Defining Transient Ischemic Dilation
• Background
• Methods
• Results
• Conclusion

4. Transient Ischemic Dilation
• The ratio of the left ventricular size after
stress compared to rest
• The left ventricular size is determined
from the ungated SPECT data
• TID is the ratio of the average wall
position at stress compared to rest

5. Transient Ischemic Dilation
“As such, the volumes associated with this
measurement should not be considered to
represent either end-systolic or end-
diastolic volumes alone but rather a
complex average of the two.”
Dan Berman, Rory Hachamovitch, Guido Germano and others,
as quoted in the J Nucl Med. 2004 Dec;45(12):1999-2007.

6. Transient Ischemic Dilation

7. Defining the “Complex Average”
• What is the contribution of the ESV?
• What is the contribution of the EDV?
• Can this complex average be derived from
the gated SPECT data?

8. “When you cannot explain it in
numbers, your knowledge is of a
meager and unsatisfactory kind.”
– Lord Kelvin (William Thomson, 1824-1907)

9. Defining Transient Ischemic Dilation
• Background
• Methods
• Results
• Conclusion

10. Methods
• Retrospective review of 422 consecutive
patients
• Ischemia determined semi-quantitatively
using a 17 segment, 5 point scale
• Post-stress to rest ventricular volume
ratios correlated with ischemia

11. Defining Transient Ischemic Dilation
• Background
• Methods
• Results
• Conclusion

12. Ventricular Volume Ratios
ESVr EDVr LVEFr
Ischemia + 1.02 1.00 1.02
Ischemia – 0.84 0.92 1.06
Difference 0.18 ** 0.08 ** - 0.04 *
** p < 0.01, * p < 0.05 for the presence or absence of ischemia using
the independent samples t-test

13. Pearson Correlation Coefficients
ESVr EDVr LVEFr
Ischemia 0.259 ** 0.227 ** -0.112 *
** p < 0.01, * p < 0.05

14. Partial Correlation Coefficients
Corrected for Type of Stress
ESVr EDVr LVEFr
Ischemia 0.2560 ** 0.2252 ** -0.1239 *
** p < 0.001, * p < 0.05

15. Partial Correlation Coefficients
Corrected for Type of Stress and Sex
ESVr EDVr LVEFr
Ischemia 0.2504 ** 0.2092 ** -0.1319 *
** p < 0.001, * p < 0.05

16. Partial Correlation Coefficients
Corrected for Type of Stress, Sex, and Age
ESVr EDVr LVEFr
Ischemia 0.2427 ** 0.2085 ** -0.1191 *
** p < 0.001, * p < 0.05

17. Optimization
• Both the ESV and EDV contain significant
correlations
• The ESV is more highly correlated than is
the EDV
• The contribution of the ESV is greater than
that of the EDV to the TID ratio

18. Optimization
stress (ESV * X + EDV)
rest (ESV * X + EDV)
where X = the ESV weighing factor
What value of X will lead to the highest
correlation with myocardial ischemia?

19. Partial Correlation Coefficients
Controlling for Type of Stress
X=0 X=5 X = 10
Ischemia 0.2252 ** 0.2761 ** 0.2738 **
stress (ESV*X + EDV) / rest (ESV*X + EDV)
where X = the ESV weighing factor
** p < 0.001

20. Controlling for Type of Stress
0.28
Correlation Coeffient
0.26
0.24
0.22
0.2
0 5 10 15 20 25 30 35 40
ESV Weighing Factor
Ischemia SDS

21. Controlling for Type of Stress
0.2762
0.276
Correlation Coefficient
0.2758
0.2756
0.2754
3.4 3.8 4.2 4.6 5 5.4 5.8 6.2
ESV Weighing Factor
Ischemia

22. Linear Regression
30.905
30.9
F Score
30.895
30.89
30.885
4.5 5.0 5.5
ESV Weighing Factor
F Score

23. Defining Transient Ischemic Dilation
• Background
• Methods
• Results
• Conclusion

24. Conclusion
• The ESVr, EDVr, and LVEFr all are significantly
correlated with myocardial ischemia
• The ESVr is more highly correlated with
myocardial ischemia than the EDVr or LVEFr
• The stress (ESVx5 + EDV) / rest (ESVx5 + EDV)
has the strongest correlation with myocardial
ischemia

25. The “Complex Average” ?
stress ESV * 5 + stress EDV
rest ESV * 5 + rest EDV