LONG-TERM EFFECT OF CARDIOVERSION ON PEAK OXYGEN-CONSUMPTION IN CHRONIC ATRIAL-FIBRILLATION - A 2-YEAR FOLLOW-UP

Restoration of sinus rhythm may improve functional capacity in atrial fibrillation in the short-term. Little is known, however, about its lo ng-term effect on functional status. The aim of the present study was to evaluate the long-term effect of cardioversion on peak oxygen consu mption (VO2) in patients with chronic atrial fibrillation. Patients wi th such a condition and due to undergo electrical cardioversion were e ligible for the study. Patients underwent treadmill exercise testing w ith measurement of peak VO2 before cardioversion, and at 1 month and 2 years thereafter. Based on the rhythm present at those times after ca rdioversion, patients were categorized into three groups: those in sin us rhythm after 1 month and 2 years (Group I); those in sinus rhythm a fter 1 month, but with atrial fibrillation after 2 years (Group II); a nd those who were in atrial fibrillation both at 1 month and 2 years f ollowing cardioversion (Group III). Thirty-nine patients were included , and underlying heart disease was present in 24 of them (62%). In the comparison of the baseline characteristics of Group I (n=17), Group I I (n=11), and Group III (n=11), underlying heart disease was more freq uent in Group I (88%, 45%, and 36%, respectively); otherwise they were similar. In Group I, peak VO2 showed an insignificant increase from 2 1.1 +/- 5.0 to 22.3 +/- 5.0 ml. min-1 . kg-1 1 month after cardioversi on. After 2 years of sinus rhythm, peak VO2 showed a further increase to 23.8 +/- 5.0 ml . min-1 . kg-1 (P<0.05). In Group II patients, peak VO2 improved after 1 month of sinus rhythm (from 25.2 +/- 7 to 27.8 /- 8 ml. min-1. kg-1, P<0.05) but returned to baseline after 2 years, when atrial fibrillation had relapsed. In Group III patients, peak VO2 was unchanged 1 month after cardioversion, when atrial fibrillation h ad already relapsed. After 2 years, however, peak VO2 had decreased fr om 22.1 +/- 4.0 to 20.6 +/- 4.0 (P<0.05), when compared to baseline. I n conclusion, restoration of sinus rhythm is associated with a modest but significant improvement of peak VO2, which persists after the firs t month following cardioversion. In addition, in patients with sustain ed atrial fibrillation functional capacity decreases during long-term follow-up. These findings suggest that, to prevent progressive deterio ration of functional capacity in atrial fibrillation, a treatment appr oach aimed at restoring and maintaining sinus rhythm may be warranted.