BNP and safety of cardioversion
PARIS, FRANCE. BNP (brain natriuretic peptide) is a hormone released by stretching of the walls of the ventricles. Thus, it is not surprising that elevated levels of BNP have been observed in patients with atrial fibrillation (AF). The serum level of BNP has been found to be highest in permanent afibbers and lowest in paroxysmal afibbers, with persistent afibbers falling somewhere in between. The observation that BNP increases with increasing duration of AF led a group of researchers at the Cochin Hospital to speculate that BNP level may be a useful indicator of how long a patient arriving in emergency has been in AF. As a general rule, cardioversion is not performed immediately if a patient has been in AF for more than 48 hours, unless a transesophageal echocardiogram (TEE) shows no evidence of thrombi (blood clots) in the left atrium and appendage. If a TEE is not performed, and a patient has been in AF for more than 48 hours, then a 3-week treatment with anticoagulants is required before cardioversion.

The French researchers included 45 patients arriving at the emergency department in AF. AF was paroxysmal in 21 patients, persistent in 6, and permanent in the remaining 18. Average BNP level (measured as NT-proBNP) was 1030 pg/mL for paroxysmal, 3658 pg/mL for persistent, and 4350 pg/mL for permanent (long-standing persistent) afibbers. Eighteen patients (40%) had been in AF for less than 48 hours upon admission (according to their own experience of symptoms, notably palpitations). These patients tended to have a higher average heart rate (136 bpm) than those who had been in AF for more than 48 hours (102 bpm).

Even more significant was the difference in BNP level. Patients who had been in AF for less than 48 hours (presumably all paroxysmal) had an average BNP level of 960 pg/mL, while those who had been in AF for more than 48 hours had an average level of 3695 pg/mL. No patients with a BNP level less than 304 pg/mL had been in AF for more than 48 hours. A cut-off value of 1328 pg/mL was associated with a sensitivity and a specificity of 74.1% and 72.2% respectively.The researchers conclude that AF patients presenting with low values of BNP are likely to have been in AF for less than 48 hours and can, therefore, be safely cardioverted. They do point out that their study involved only a small number of patients and that larger studies are needed to confirm their findings and fine-tune the cut-off point.

Meune, C, et al. N-Terminal-proBrain natriuretic peptide measurement at presentation to identify patients with recent onset of atrial fibrillation. International Journal of Cardiology, Vol. 154, January 26, 2012, pp. 208-09

Editor's comment: Most afibbers present for cardioversion with symptomatic AF so they know well how long they have been fibrillation. It would be very useful if their statement concerning how long they have been in AF could be confirmed with a simple blood test, so as to avoid a 3-week course of anticoagulation prior to cardioversion.