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Both groups had normal LV and right ventricular dimensions (data not shown). CFR All patients with TSC and controls reached >85% of calculated maximum MK-0518 solubility dmso heart rate during dobutamine stress without the addition of atropine. Resting heart rate was similar for the patients with TSC and controls (68?bpm for both) as well as during low-dose dobutamine (99 vs 94?bpm, p=non-significant). Maximum heart rate at high-dose dobutamine was also similar between the groups (131 vs 134?bpm, p=non-significant). CFR at low-dose dobutamine was significantly lower in patients with TSC compared with controls (1.51 and 1.72, p=0.017). Although the CFR was higher in controls during high-dose dobutamine, the results did not reach the significance level (table 2 and figure 2). Table?2 Coronary flow reserve (CFR) Figure?2 Results of coronary flow reserve. Thick horizontal line, median value; boxes, IQR and whiskers 95% CI. Discussion In this, to the best of our knowledge, first study on microvascular function in TSC performed with a catecholamine, we could not confirm that dobutamine induced microvascular dysfunction. However, we did find a significant difference between patients with TSC and controls at low-dose CO-1686 cell line dobutamine. Although the effects of dobutamine stress on CFR in TSC have not been studied previously, there are several studies where the effects of adenosine or dipyridamole have been studied. In a study by Kume et al, the effect of adenosine on CFR in eight patients with TSC was invasively measured. They found a reduced CFR in the acute phase with normalisation after 3?weeks.11 Similar results have been shown by Meimoun et al4 using non-invasive CFR to measure the effect of adenosine during the acute TSC event and after 4?weeks. In contrast to these results, a study by Sganzerla et al12 of seven patients with TSC, showed no difference in non-invasive CFR using adenosine on admission, compared with its use after 3?weeks. However, patients with hypertension, diabetes mellitus and present smoking were all excluded from participating in the latter study. It should Org 27569 be noted that no control group was used in any of these studies. Rigo et al8 measured CFR non-invasively using dipyridamole. They compared 30 patients with TSC against 30 reasonably matched controls (mean 68 and 56?years, respectively). CFR in the acute phase was lower in the TSC group compared with the controls, while measurements on day 7 and after 6?months showed a normalisation of CFR. In summary, in most previous studies, CFR was reduced in the subacute phase in patients with TSC but normalised after a few weeks or months. In contrast to CFR measured using adenosine, we found a small but significant difference using the catecholamine dobutamine more than 6?months after the acute event.