redefining the transient ischemic dilation ratio

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


“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.

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)


• 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


• 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


Corrected for Type of Stress and Sex

-0.1319 *0.2092 **0.2504 **Ischemia

LVEFrEDVrESVr

** p < 0.001, * p < 0.05


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?


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


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


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


• 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

redefining the transient ischemic dilation ratio

Health & Medicine