CORRESPONDENCE: LETTER TO THE EDITOR
Reply
Eftihia Sbarouni, MD, FESC*,
Panagiota Georgiadou, MD,
George N. Theodorakis, MD, FESC and
Dimitrios Th. Kremastinos, MD, FESC
* Onassis Cardiac Surgery Center, 2nd Department of Cardiology, 356 Syngrou Avenue, 176 74 Athens, Greece (Email: esbarouni{at}yahoo.gr).
We appreciate the interest of Dr. Kalay and colleagues in our study assessing ischemia-modified albumin (IMA) levels in exercise stress testing (1). We address their comments:- 1 All our patients had angiographically documented coronary artery disease, the exercise stress test (EST) being part of their regular follow-up, and the criteria we used for positivity were rather strict—2-mm horizontal or downsloping ST depression. In addition, our findings do not differ from Van der Zee et al. (2), who also observed a significant decrease of IMA plasma levels at peak exercise and subsequent return to baseline, without any difference between positive and negative exercise tests. In that study, single-photon emission computed tomography (SPECT) imaging, a more sensitive and specific method compared to treadmill testing, was used. Therefore, in that respect, we believe inaccuracies in the EST results (false positive or negative) cannot be substantiated.
- 2 Regarding the timing of IMA sampling, percutaneous coronary intervention (PCI) studies have shown a significant increase in IMA plasma levels immediately following balloon deflation and a return to baseline within 6 to 12 h (3,4), so we would think that peak exercise is the appropriate time point to assess whether IMA increases in exercise-induced ischemia.
- 3 Although we cannot exclude occult peripheral atherosclerosis in our patients, none of the study participants had clinically significant peripheral vascular disease, by history, physical examination or clinical presentation. Additionally, in no patient was the EST limited by skeletal muscle ischemia, rendering the mechanism of peripheral lactic acidosis as a cause of decreased exercise IMA levels extremely unlikely. Furthermore, a very recent report observed that the rise in IMA plasma levels after PCI parallels that of transmyocardial lactate, immediately after obstructive balloon inflation (5).
In the letter by Drs. Roy and Kaski regarding our study (1) they state that IMA decrease at exercise may relate to either albumin or lactate increase. Albumin plasma levels have been assessed during exercise (2) and have been nicely shown to correlate inversely with IMA changes, in patients with and without ischemia. Therefore, we believe that the IMA changes we observed are associated with hemoconcentration. It is well known that reactive oxygen species production during myocardial ischemia (PCI or acute coronary syndrome) may indeed induce changes in the amino terminus of albumin. In addition, we agree that further research regarding specific mechanisms is necessary.
In conclusion, our study demonstrated that IMA changes significantly during EST in patients with coronary disease but with no difference between positive and negative tests; these results, we believe, imply that IMA changes may not relate to myocardial ischemia.
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1. Sbarouni E, Georgiadou P, Theodorakis GN, Kremastinos DT. Ischemia-modified albumin in relation to exercise stress testing J Am Coll Cardiol 2006;48:2482-2484.[Abstract/Free Full Text]2. Van der Zee PM, Verberne HJ, Straalen JP, et al. Ischemia-modified albumin measurements in symptom-limited exercise myocardial perfusion scintigraphy reflect serum albumin concentrations but not myocardial ischemia Clin Chem 2005;51:1744-1746.[Free Full Text] 3. Bar-Or D, Winkler JV, VanBenthysen K, et al. Reduced albumin-cobalt binding with transient myocardial ischemia after elective percutaneous transluminal coronary angioplasty: a preliminary comparison to creatine kinase-MB, myoglobin, and troponin I Am Heart J 2001;141:985-991.[CrossRef][Web of Science][Medline] 4. Quiles J, Roy D, Gaze D, et al. Relation of ischemia-modified albumin (IMA) levels following elective angioplasty for stable angina pectoris to duration of balloon-induced myocardial ischemia Am J Cardiol 2003;92:322-324.[CrossRef][Web of Science][Medline] 5. Sinha MK, Vasquez JM, Calvino R, Gaze DC, Collinson PO, Kaski JC. Effects of balloon occlusion during percutaneous coronary intervention on circulating ischemia modified albumin and transmyocardial lactate extraction Heart 2006;92:1852-1853.[Free Full Text]
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