Published reports have indicated that the plasma levels of two hormones, atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP), are increased in patients with atrial fibrillation (af). Dr. Yokoyama's research group wondered whether the pressure overload in the left atrium that can induce paroxysmal atrial fibrillation (Paf) could also lead to an increase in the plasma levels of the two hormones. The current work was designed to test this hypothesis with a group of patients who were affected by the paroxysmal arrhythmia.

The researchers planned to study 41 consecutive patients who were admitted to their facility with cardiac symptoms of af and who were converted successfully to sinus rhythm. Means of cardioversion (antiarrhythmic therapy or electrical cardioversion) had no effect on patient eligibility for the study.

Plasma levels of ANP and BNP were scheduled to be drawn before cardioversion, 20 minutes after cardioversion, and for 5 consecutive days after cardioversion. On Day 7 after cardioversion, echocardiography would be done to determine trans-mitral flow (TMF).

After two patients were excluded for rapid recurrence of arrhythmia (within 24 hours of cardioverson), a total of 39 patients remained in the study. Blood samples and echocardiography was done as planned. Recurrent af developed in 13 patients within the first month after cardioversion, and these patients were termed R-group. The 26 patients who maintained sinus rhythm through that first month were termed the S-group. There was no difference in significant clinical characteristics between the two groups of patients.

In contrast, there were significant differences between patient groups in characteristics of the arrhythmia, itself. Patients whose Paf recurred (R-group) had a much longer duration of arrhythmia than patients who maintained sinus rhythm (S-group) (median duration, 91 hours and 18 hours, respectively).

Data on plasma ANP level in the immediate post-cardioversion period show that all patients had a significant decrease in plasma ANP level 20 minutes after cardioversion.

Dr. Yokoyama then explained the relationship between re-elevation of hormone level and recurrence of Paf. When the data were plotted to show change in BNP level compared with the level at 24 hours after cardioversion (a time point for which patients in both the R-group and S-group had a significant decrease from baseline), it became apparent that the R-group patients had re-elevation of BNP level before recurrence of their arrhythmia.

All 26 S-group patients underwent echocardiography on Day 7 as planned, whereas only the 7 patients in the R-group who were in sinus rhythm underwent examination. The researchers found that patients who would later develop recurrent Paf (those in the R-group) had a significant difference from those who would remain in sinus rhythm (those in the S-group): The R-group patients had a markedly lower A/E ratio than the patients in the S-group (0.5 ± 0.2 versus 1.2 ± 0.6).

Dr. Yokoyama concluded by noting that the current work is the first to establish that ANP and BNP levels re-elevate before recurrence of arrhythmia. In combination with the echocardiographic findings on A/E ratio, the data suggest that pressure overload of the left atrium can occur during sinus rhythm and that the overload increases plasma levels of ANP and BNP and triggers recurrent Paf.