## Results
### Kinetics of Serum Serotonin  
Serum serotonin levels ranged between 21.3 and 325.3 ng/mL, with a median of 114.2 ng/mL (IQR: 71.9-135.3). Median and interquartile range were within the reference range for serum serotonin levels (70-270 ng/mL).  
The first samples were taken prior to coronary angiography (t = 0) and subsequently 8, 16 and 24 h later. We did not see any significant increase or decrease in serum serotonin levels during the observed 24 h interval. Moreover, all median values were within the reference range for serum serotonin (90.7 ng/mL, 108.0 ng/mL, 105.6 ng/mL, 87.6 ng/mL). Compared to serum serotonin levels, the currently used biomarkers for myocardial damage, myoglobin, troponin, and CK, showed a significant increase after myocardial infarction and PCI (Figure 1).  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Cardiovascular Risk Profile** & & & \\ \hline
**Diabetes** & 10 (26.3\%) \({}^{\text{c}}\) & **HbA1c [\%]** & 5.8 \(\pm\)1.3 \({}^{\text{a}}\) \\
**Hypercholesterolemia** & 19 (50\%) \({}^{\text{c}}\) & **total cholesterol** & 180.0 \(\pm\) 41.5 \({}^{\text{b}}\) \\  & & **low density** & \\  & & **lipoprotein (LDL)** & 120 \(\pm\) 40 \({}^{\text{b}}\) \\  & & **[mg/dL]** & \\
**Overweight** & 14 (36.8\%) \({}^{\text{c}}\) & **BMI [kg/m\({}^{2}\)]** & 28.6 \(\pm\) 5.05 \({}^{\text{a}}\) \\
**Arterial Hypertension** & 23 (60.5\%) \({}^{\text{c}}\) & & \\
**Positive Family History** & 13 (34.2\%) \({}^{\text{c}}\) & & \\
**Smoking** & current & 15 (39.5\%) \({}^{\text{c}}\) & & \\  & previous & 6 (15.8\%) \({}^{\text{c}}\) & & \\ \hline
**CAD Characteristics** & & & \\ \hline
**Number of Coronaries** & 1 & 11 (28.9\%) \({}^{\text{c}}\) & \\
**Affected** & 2 & 14 (36.8\%) \({}^{\text{c}}\) & \\  & 3 & 13 (34.2\%) \({}^{\text{c}}\) & \\
**Culprit Lesion** & RCA & 17 (44.7\%) \({}^{\text{c}}\) & \\  & LAD & 18 (47.4\%) \({}^{\text{c}}\) & \\  & LCX & 3 (7.9\%) \({}^{\text{c}}\) & \\
**CK Peak [U/L, reference** & & 740.0 \(\pm\) 2385.0 \({}^{\text{a}}\) \\ range \textless{} 170 U/L] & & & \\
**CK-MB Peak [U/L, reference** & & 85.0 \(\pm\) 251.0 \({}^{\text{a}}\) \\ range \textless{} 24 U/L] & & & \\
**Myoglobin Peak [ng/mL,** & & 181.0 \(\pm\) 734.5 \({}^{\text{a}}\) \\
**reference range 19-51 ng/mL]** & & & \\
**Troponin Peak [ng/L, reference** & & 2226.5 \(\pm\) 4930.0 \({}^{\text{a}}\) \\ range \textless{} 14 ng/L]** & & & \\
**BNP Peak [pg/mL, reference** & & 1365.0 \(\pm\) 1976 \({}^{\text{a}}\) \\ range \textless{} 125 pg/mL]** & & & \\
**left ventricular ejection** & & & \\
**fraction (LVEF) [\%]** & & 45.0 \(\pm\) 10.0 \({}^{\text{a}}\) & \\ \hline \hline \end{tabular}
\end{table}
Table 2: Coronary artery disease (CAD) characteristics in the ST-elevation myocardial infarction (STEMI) cohort. \({}^{\text{a}}\) Presented as median \(\pm\) interquartile range, \({}^{\text{b}}\) presented as mean \(\pm\) standard deviation, \({}^{\text{c}}\) number of patients (with percentage based on the number of patients with a non-missing value for that characteristic. Hypercholesterolemia was defined as total cholesterol \(>\)200 mg/dL or on medication. For creatine kinase (CK), creatine kinase myocardial band (CK-MB), myoglobin, troponin, and brain natriuretic peptide (BNP), the peak values within the first 24 h after myocardial infarction are listed.