Post on 14-Jul-2015
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The Bitterroot Mountains From Kellogg Peak
Necessity is the Mother of Invention.- Plato
Defining Transient Ischemic Dilation
• Background
• Methods
• Results
• Conclusion
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
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.
Transient Ischemic Dilation
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?
“When you cannot explain it in numbers, your knowledge is of a meager and unsatisfactory kind.”
– Lord Kelvin (William Thomson, 1824-1907)
Defining Transient Ischemic Dilation
• Background
• Methods
• Results
• Conclusion
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
Defining Transient Ischemic Dilation
• Background
• Methods
• Results
• Conclusion
Ventricular Volume Ratios
- 0.04 *0.08 **0.18 **Difference
1.060.920.84Ischemia –
1.021.001.02Ischemia +
LVEFrEDVrESVr
** p < 0.01, * p < 0.05 for the presence or absence of ischemia using the independent samples t-test
Pearson Correlation Coefficients
-0.112 *0.227 **0.259 **Ischemia
LVEFrEDVrESVr
** p < 0.01, * p < 0.05
Partial Correlation Coefficients
Corrected for Type of Stress
-0.1239 *0.2252 **0.2560 **Ischemia
LVEFrEDVrESVr
** p < 0.001, * p < 0.05
Partial Correlation Coefficients
Corrected for Type of Stress and Sex
-0.1319 *0.2092 **0.2504 **Ischemia
LVEFrEDVrESVr
** p < 0.001, * p < 0.05
Partial Correlation Coefficients
Corrected for Type of Stress, Sex, and Age
-0.1191 *0.2085 **0.2427 **Ischemia
LVEFrEDVrESVr
** p < 0.001, * p < 0.05
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
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?
Partial Correlation Coefficients
Controlling for Type of Stress
0.2738 **0.2761 **0.2252 **Ischemia
X = 10X = 5X = 0
stress (ESV*X + EDV) / rest (ESV*X + EDV)where X = the ESV weighing factor
** p < 0.001
Controlling for Type of Stress
0.2
0.22
0.24
0.26
0.28
0 5 10 15 20 25 30 35 40
ESV Weighing Factor
Correlation Coeffient
Ischemia SDS
Controlling for Type of Stress
0.2754
0.2756
0.2758
0.276
0.2762
3.4 3.8 4.2 4.6 5 5.4 5.8 6.2
ESV Weighing Factor
Correlation Coefficient
Ischemia
Linear Regression
30.885
30.89
30.895
30.9
30.905
4.5 5.0 5.5
ESV Weighing Factor
F Score
F Score
Defining Transient Ischemic Dilation
• Background
• Methods
• Results
• Conclusion
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
The “Complex Average” ?
stress ESV * 5 + stress EDVstress ESV * 5 + stress EDV
rest ESV * 5 + rest EDVrest ESV * 5 + rest EDV