Author + information
- Joseph Selvanayagam, DPhil⁎ ( and )
- Jayanth Ranjit Arnold, DPhil
- ↵⁎Department of Cardiovascular Medicine, Flinders Medical Centre, Bedford Park 5042, Adelaide, South Australia, Australia
We thank Dr. Sharma for his comments on our report (1). Although blood oxygen level-dependent (BOLD) imaging is unlikely to offer incremental diagnostic benefit above first-pass perfusion assessment, it is conceivable, in the future, that it could serve as a viable alternative, with the added benefit of avoiding extrinsic contrast. However, we acknowledge that before this prospect can be realized, the technique requires significant further development, notably improvement in specificity and spatial coverage.
Our study involved patients with stable angina: subjects with acute coronary syndromes were excluded, and the diagnostic performance of BOLD imaging in the setting of varying glucose levels was not examined specifically. However, it is difficult to envisage a mechanism whereby altered glucose or hemoglobin levels would affect the oxygenation saturation of the hemoglobin molecule or the sensitivity of the BOLD technique. Factors that shift the oxygen dissociation curve alter the affinity of hemoglobin for oxygen, and hence, the relative quantities of oxyhemoglobin and deoxyhemoglobin. However, there is no reason to suspect that they would affect oxygenation sensitivity of the BOLD technique per se, and experimental evidence demonstrates the correlation between BOLD signal intensity and oxygen saturation over a range of values (2,3).
- American College of Cardiology Foundation