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Characterization of Cardiac Troponin Elevation in the Setting of Pediatric Supraventricular Tachycardia

Cardiac troponin (cTn) is currently considered the gold standard biomarker for detection of myocardial necrosis. Patients with supraventricular tachycardia (SVT) often present with symptoms resulting in cTn assessment; however, there are no data on the results of such testing in childhood. We hypothesized that cTn elevation would be common in the pediatric SVT population and would portend a benign prognosis. A retrospective review of all pediatric patients (≤21 years) presenting with SVT was performed. Clinical and electrocardiographic variables from the emergency department (ED) presentation were reviewed and clinical outcomes during subsequent follow-up assessed. Of 128 patients seen in the ED for SVT, cTn was assessed in 48 (38 %). Of patients with cTn assessment, 14 (29 %) patients demonstrated cTn elevation. Univariate predictors of cTn elevation included presentation with respiratory or gastrointestinal symptoms (50 vs 12 % and 42 vs 9 %; p = 0.008 and p = 0.01, respectively), lower mean arterial blood pressure (73 vs 85 mm Hg, p = 0.009), higher age-adjusted tachycardia rate (z score 9.3 vs 7.2, p < 0.001), and longer tachycardia duration (4.2 vs 1.0 h, p = 0.02). Multivariate logistic regression confirmed the association of age-adjusted tachycardia rate (odds ratio [OR] 3.8 per heart rate z score, confidence interval [CI] 1.9-11.8, p = 0.003) and duration (OR 1.5 per hour, CI 1.1-2.5, p = 0.03). Clinical outcome was excellent with no adverse sequelae during a median of 2.9 years of follow-up. Cardiac Tn elevation is common in the pediatric population presenting with SVT. Episode severity, characterized by respiratory or gastrointestinal symptoms, lower mean blood pressure, and increased tachycardia rate and duration are predictive. Clinical follow-up is favorable.

Relationship of myocardial ischemia and injury to coronary artery disease in patients with supraventricular tachycardia

Increase of serum troponin I and ST-segment depression are objective markers of myocardial ischemia/injury. Abnormalities of the 2 indicators have been associated with supraventricular tachycardia (SVT) but their relevance for diagnosing acute coronary syndrome and the presence of coronary artery disease (CAD) in this setting have not been clarified. Therefore, we sought to evaluate the frequency of CAD based on increased troponin I and ST-segment depression during SVT. During a 5-year period, 104 patients were admitted with a diagnosis of SVT, 80 of whom had troponin I testing, and 70 of these patients could be assessed for ST-segment changes. Thirty-seven patients (48%) had increased troponin I (mean 1.54 +/- 2.7 ng/dl, normal <or=0.07 ng/dl) and 46 patients (57%) had ST-segment depression >or=1.0 mm. There were no significant differences in baseline characteristics and clinical presentation of patients with and without troponin I increase or ST-segment depression. There was no difference in the diagnosis of CAD by noninvasive or invasive testing in patients with and without increased troponin I. More patients with than without ST-segment depression had evidence of CAD (22% vs none, p = 0.01), but after adjusting for covariates, ST-segment depression was not a significant predictor of CAD. In conclusion, increased troponin I and ST-segment depression are not significant markers of acute coronary syndrome in patients with SVT.

Prognostic significance of cardiac troponin I levels in hospitalized patients presenting with supraventricular tachycardia

Although cardiac troponin I (cTnI) elevation in patients presenting to the hospital with supraventricular tachycardia (SVT) is well recognized, the prevalence, predictors, and prognostic significance of cTnI elevation associated with SVT presentation are not known. We screened records of all patients presenting to 2 hospitals over a 4-year period with the diagnosis of SVT confirmed by 12-lead electrocardiogram, and who had at least 1 measured cTnI level and at least 1 year of follow-up after discharge. The primary endpoint was the occurrence of 1 of the following outcomes: death, myocardial infarction, or cardiovascular rehospitalization. Seventy-eight patients met the study criteria (54% female; mean age, 62.2 +/- 15.8 yr), and 29 patients (37.2%) had an elevated cTnI level of > or =0.06 ng/mL (range, 0.06-7.78 ng/mL). Univariate predictors of elevated cTnI included left ventricular ejection fraction (LVEF) <50%, renal dysfunction, ST-segment depression or left bundle branch block on the electrocardiogram, and moderate or severe regurgitation of any cardiac valve. Predictors of elevated cTnI after multivariate analysis included peak heart rate during SVT (per 15 bpm) (odds ratio [OR], 1.58; 95% confidence interval [CI], 1.01-2.46; p = 0.04) and LVEF <50% (OR, 6.12; 95% CI, 1.40-26.7; p = 0.02). After multivariable adjustment, the presence of elevated cTnI with SVT was associated with increased risk of the primary endpoint of death, myocardial infarction, or cardiovascular rehospitalization (hazard ratio [HR], 3.67; 95% CI, 1.22-11.1; p = 0.02). Mild elevation of cTnI is common in patients presenting to the hospital with SVT, and is associated with increased risk of future cardiovascular events. Further study is needed to determine the mechanisms of SVT-related cTnI elevation and its association with elevated cardiovascular risk.