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Phasic changes in arterial blood volume is influenced by collateral blood flow: implications for the quantification
Marco Pascotto1, Kevin Wei, Antonio Micari
1Division of Cardiovascular Medicine, Oregon Health & Science University, Portland, OR 97239, USA.
Insights
Collateral blood flow significantly influences the systolic to diastolic arteriolar blood volume (aBV) ratio in myocardial contrast echocardiography (MCE). This ratio may offer prognostic information beyond coronary anatomy, especially in cases of extensive collateralization.
Area of Science:
- Cardiovascular imaging
- Hemodynamics
- Echocardiography
Background:
- Myocardial contrast echocardiography (MCE) uses the systolic to diastolic arteriolar blood volume (aBV) ratio to detect coronary stenosis.
- Some patients with moderate to severe stenosis show a normal aBV ratio at rest.
Purpose of the Study:
- To investigate the influence of collateral blood flow on the systolic to diastolic aBV ratio.
- To assess MCE-defined phasic aBV changes in collateralized and non-collateralized regions under varying degrees of stenosis.
Main Methods:
- Phasic aBV changes were measured using MCE in 12 dogs at baseline and with induced non-critical stenosis.
- Measurements were taken in both collateralized and non-collateralized segments of the left anterior descending arterial bed.
Main Results:
- In non-collateralized regions, the systolic to diastolic aBV ratio significantly increased with stenosis (p=0.003).
- In collateralized regions, neither absolute aBV signals nor the systolic to diastolic ratio changed significantly with increasing stenosis.
Conclusions:
- Phasic aBV changes are modulated by collateral blood flow.
- The systolic to diastolic aBV ratio can underestimate stenosis severity if not accurately placed within the vascular bed.
- Extensive collateralization, indicated by this ratio, may predict excellent prognosis independently of coronary anatomy.
Background:
The systolic to diastolic arteriolar blood volume (aBV) ratio derived using myocardial contrast echocardiography (MCE) can identify the presence of coronary stenosis at rest. There are some patients with moderate to severe coronary stenosis who nonetheless exhibit a normal systolic to disatolic aBV ratio.
Aim:
To test the hypothesis that collateral blood flow influences the systolic to diastolic aBV ratio. MCE-defined phasic changes in aBV were recorded at baseline and up to 2 degrees of non-critical stenosis in 12 dogs. Measurements were made from MCE-defined collateralised and non-collateralised portions of the left anterior descending arterial bed.
Results:
Increases in both systolic and diastolic aBV were noted in the non-collateralised region with increasing degrees of stenosis. Although these increases in the absolute values did not reach statistical significance, the systolic to diastolic aBV signal ratio in the non-collateralised bed increased significantly between stages (analysis of variance, p = 0.003). In comparison, in the collateralised bed neither the absolute systolic nor diastolic aBV signals changed with increasing degrees of stenosis. Consequently, the aBV signal ratio between systole and diastole also did not change in this bed.
Conclusion:
Phasic changes in aBV are influenced by the degree of collateral blood flow. Thus, if the region of interest is not placed in the centre of the vascular bed, the degree of stenosis may be underestimated by the systolic to diastolic aBV ratio. On the other hand, as extensive collateralisation may indicate excellent prognosis, this ratio may provide prognostic information independent of the coronary anatomy.
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