European Heart Journal Advance Access originally published online on October 10, 2007
European Heart Journal 2007 28(21):2688; doi:10.1093/eurheartj/ehm382
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Is subendocardial ischaemia present in patients with chest pain and normal coronary angiograms? A cardiovascular MR study: reply
VU University Medical Centre
Nuclear Medicine and PET Research
de Boelelaan 1117
1007 MB Amsterdam
The Netherlands
Department of Nuclear Medicine & PET Research
VU University Medical Centre
de Boelelaan 1117
1007 MB Amsterdam
The Netherlands
Department of Physics and Medical Technology
VU University Medical Centre
de Boelelaan 1117
1007 MB Amsterdam
The Netherlands
Department of Cardiology
VU University Medical Centre
de Boelelaan 1117
1007 MB Amsterdam
The Netherlands
Tel: +31 20 4444214 Fax: +31 20 4443090 E-mail address: i.vermeltfoort{at}vumc.nl
We would like to thank Professor Axel for the comments related to our study.
The dark-rim artifact in cardiac first pass perfusion images has been related in the literature to a number of potential sources; cardiac motion of the heart walls,1 interface of susceptibility change,2 and Gibbs ringing.3 The intensity of the artifact due to motion is determined by the temporal resolution of the acquisition in combination with the image resolution, k-space order, and extent of motion. Spatial and temporal resolution and k-space order were comparable or better for our study compared to the study by Panting et al.4 The influence of the interface of susceptibility is determined by the applied pulse sequence technique, the echo time, voxel size, and contrast dose. Both studies used a spoiled gradient echo pulse sequence and similar settings for the contrast agent application. The settings for the voxel size and echo time were actually slightly better in our study. Finally, Gibbs ringing is mainly determined by the spatial resolution; again this was not worse in our study compared to the study of Panting et al. Considering this discussion on the imaging techniques applied in both studies, we do not expect to have significantly more dark-rim artifacts in our study compared to the study by Panting et al.
The goal of our study, however, was to measure the extent and frequency of a possible decreased subendocardial perfusion reserve with CMR in patients with syndrome X and not to evaluate possible artifacts. Despite the presence of artifacts, we found a clear and significant rise of the myocardial perfusion index (MPI) in the subendocardial region of all our patients without any evidence of subendocardial ischaemia. Imaging of a control group would have increased our understanding of artifacts but would not change the findings in our patients.
We dispute the argument of Axel that a shorter adenosine infusion may account for the differences between both studies. Maximum coronary flow occurs at an average of 84 s with a range of up to 125 s following the onset of intravenous adenosine infusion.5 Therefore, we consider our adenosine protocol sufficient to induce a steady state of maximal hyperaemia. This is illustrated by the 82% increase of the subepicardial MPI during adenosine infusion in both our patients and the patients group of Panting et al.
Finally, we agree with Axel that patient selection is different from the earlier study. In our study, more patients with syndrome X had an abnormal myocardial SPECT result, whereas in the study of Panting et al. more patients showed an abnormal ECG during exercise. However, the selection of syndrome X patients using both exercise- ECG and SPECT is an accepted method.6 All our patients with an abnormal exercise ECG had an increase of their subendocardial MPI, and a normal MPRI.
In conclusion, we consider it unlikely that the differences mentioned fully explain the contrast of results between the two studies.
We agree with Axel that more studies are necessary.
References
- Storey P, Chen Q, Li W, Edelman RR, Prasad PV. Band artifacts due to bulk motion. Magn Reson Med (2002) 48:1028–1036.[CrossRef][Web of Science][Medline]
- Schreiber WG, Schmitt M, Kalden P, Mohrs OK, Kreitner KF, Thelen M. Dynamic contrast-enhanced myocardial perfusion imaging using saturation-prepared TrueFISP. J Magn Reson Imaging (2002) 16:641–652.[CrossRef][Web of Science][Medline]
- Di Bella EV, Parker DL, Sinusas AJ. On the dark rim artifact in dynamic contrast-enhanced MRI myocardial perfusion studies. Magn Reson Med (2005) 54:1295–1299.[CrossRef][Web of Science][Medline]
- Panting JR, Gatehouse PD, Yang GZ, Grothues F, Firmin DN, Collins P, Pennell DJ. Abnormal subendocardial perfusion in cardiac syndrome X detected by cardiovascular magnetic resonance imaging. N Engl J Med (2002) 346:1948–1953.
[Abstract/Free Full Text] - Zipes DP, Braunwald E. Braunwald's heart disease a textbook of cardiovascular medicine (2005) 7th ed. Philadelphia, PA: Elsevier Saunders.
- Lanza GA. Cardiac syndrome X: a critical overview and future perspectives. Heart (2007) 93:159–166.
[Abstract/Free Full Text]
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