In Workup for New-Onset AF, What and What Not to Order?

November 15, 2013

In new-onset atrial fibrillation there is good evidence for obtaining a troponin T level. High levels are associated with highest rates of stroke, embolism, and cardiac mortality.

Mr Brown is a 55-year-old man with a history of hypertension who is otherwise healthy. He comes to your office complaining of 1 week of palpitations and intermittent light-headedness. On examination, you find that his heart sounds are irregularly irregular. ECG confirms that he is in atrial fibrillation (AF) with a ventricular rate of 110 to 130 beats/min. There are no other associated ST-T wave abnormalities when compared with his baseline ECG. His blood pressure is 122/83 mm Hg.

Which of the following tests is NOT indicated as part of your initial assessment of Mr Jones?

A. Serum electrolyte panel and complete blood cell count
B. Thyroid-stimulating hormone (TSH)
C. Transthoracic echocardiogram
D. Chest CT
E. Troponin T (TnT) level
F. All of the above are indicated in the initial workup of new-onset AF.

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Answer: D.  A chest CT is not indicated as an initial screening tool

A chest x-ray film can be obtained instead to assess for lung disease, such as pneumonia, that may be leading to atrial fibrillation (AF). In addition to an ECG, serial troponin measurements are indicated if there are ECG changes concerning for ischemia. However, a recent study has shown that troponin measurements can also offer prognostic information, especially in patients with low CHA2DS2-VASc scores.

Troponin measurements in AF in patients with CHADS2 score ≥ 1 were assessed in the ARISTOTLE study, a controlled trial that randomized 14,897 patients to apixaban or warfarin. This prespecified substudy analysis showed that 99.4% of patients had measureable troponin T (TnT) values and that higher TnT were independently associated with highest rates of stroke and systemic embolism (adjusted HR = 1.94 for the highest quartile) and cardiac mortality (adjusted HR = 4.31 in the highest quartile). In addition, adding TnT to the CHA2DS2-VASc score improved the C-statistic as well, suggesting that checking TnT may be useful for prognosis in patients with low CHA2DS2-VASc scores.

Reference:
Hijazi Z, Wallentin L, Siegbahn A, et al. High sensitivity troponin T and risk stratification in patients with atrial fibrillation during treatment with apixaban or warfarin. J Am Coll Cardiol. 2013. doi:10.1016/j.jacc.2013.07.093. (Abstract)