AUSTIN, TEXAS. Brain natriuretic peptide (BNP), a cousin of atrial natriuretic peptide (ANP), is a hormone released from the walls of the ventricles when stretched such as during unusually strenuous activity. It is stored as a prohormone within secretory granules in the ventricles and is secreted as an N-terminal fragment, N-terminal pro-brain natriuretic peptide (nt-pro-BNP), and the smaller active hormone BNP. BNP has effects similar to those of ANP, that is, it decreases sodium reabsorption rate, renin release, and aldosterone release; it also increases vagal (parasympathetic) tone and decreases adrenergic (sympathetic) tone. Because nt-pro-BNP is easier to measure than BNP it is often used as a marker for BNP.
It is well established that BNP and nt-pro-BNP levels are elevated in heart failure and that the degree of elevation is directly proportional to the seriousness of the failure. Researchers at the Massachusetts General Hospital have reported that lone afibbers also have elevated nt-pro-BNP values even when in sinus rhythm.
Now an international group of arrhythmia researchers led by Dr. Andrea Natale reports that pre-ablation BNP level predicts the risk of post-ablation recurrence in male afibbers. Their study included 568 consecutive lone AF patients (no structural heart disease) who underwent a radiofrequency catheter ablation between April 2008 and February 2010 at St. David's Medical Center. The average age of the patients was 62 years, 73% were male, and the average number of years they had suffered from AF was 6.6 years. Twenty-five per cent of the study participants had paroxysmal AF, 38% had the persistent variety, and 37% had permanent (long-standing persistent) AF.
All patients had their baseline BNP level measured. The average BNP level for men was 87 pg/mL and 126 pg/mL for women. After undergoing a standard pulmonary vein antrum isolation procedure (PVAI) with additional lesions as required, the study participants were followed up for 12 months and arrhythmia recurrences were recorded after a 2-month blanking period. At the end of the study, 73% of male patients and 64% of female patients were in normal sinus rhythm without the use of antiarrhythmic drugs. Statistically significantly predictors of AF recurrence for men were hypertension (associated with a reduced risk of recurrence) persistent or long-standing persistent AF, a BNP level above 50 pg/mL, and an enlarged atrium. Among women, the predictors were AF type and hypertension (associated with a reduced risk of recurrence).
The researchers conclude that a high baseline BNP level (greater than or equal to 50 pg/mL) is a strong independent risk factor for AF recurrence in men having undergone a PVAI. Eighty per cent of men with a baseline BNP level below 50 pg/mL were free of arrhythmia without the use of antiarrhythmics 12 months following a single PVAI. The corresponding success rates for men with a BNP level at or above 50 pg/mL and for women (irrespective of BNP level) were 67% and 64% respectively.Mohanty, S, Natale, A, et al. Baseline B-type natriuretic peptide: a gender-specific predictor of procedure-outcome in atrial fibrillation patients undergoing catheter ablation. Journal of Cardiovascular Electrophysiology, Vol. 22, August 2011, pp. 858-65 Editor's comment
: The role of BNP in atrial fibrillation was discussed in detail in my research report The Role of BNP in Atrial Fibrillation
. The conclusion of this report was that BNP is an important hormone released from the walls of the ventricles and, to some extent, the atria when stretched. It is well established that a high BNP level is associated with heart failure, but it is now also clear that elevated BNP levels are closely associated with atrial fibrillation including lone AF. BNP levels are higher in afibbers than in non-afibbers and those in permanent afibbers are higher than those in paroxysmal afibbers. A high BNP level is associated with a lower probability that cardioversion will be successful and also predicts a poor outcome of catheter ablation – at least for male afibbers. There is also evidence that an elevated BNP level in paroxysmal afibbers is associated with a quicker progression to the permanent state. Finally, some very recent research provides convincing evidence that an elevated BNP level is strongly associated with the risk of developing AF over a 10-year period following the baseline BNP determination. It is to be hoped that electrophysiologists will soon include a measurement of BNP or nt-pro-BNP in their initial evaluation of all afibbers and their relatives.