HEMODYNAMIC
CHANGES AFTER CARDIOVERSION OF CHRONIC ATRIAL FIBRILLATION
This review (712 cases) defined
the hemodynamic changes occurring after cardioversion of chronic atrial fibrillation (AF)
—the most common sustained disorder of the heartbeat.
After the reversion of chronic AF to sinus rhythm there was a gradual and significant
increase in cardiac output during the next 4 weeks in patients who remained in sinus
rhythm. This was accompanied by, and probably caused by, the increasing strength of left
atrial contraction. Heart rate decreases in the majority of patients after restoration of
sinus rhythm, diastole is lengthened, increasing time for ventricular filling.
Return of normal left atrial function after cardioversion may take several weeks. This
suggests an atrial myopathy caused by the prolonged arrhythmia. This explains the
continued need for anticoagulation for at least 4 weeks after cardioversion of chronic AF
to prevent thromboembolism. (In patients with acute AF of less than 2 weeks, there is an
immediate return to vigorous left atrial mechanical activity after conversion.)
Chronic AF lasting for years is often associated with substantial fibrosis of the left
atrium and, even if reversion to sinus rhythm occurs, there is a permanent absence of
atrial mechanical activity.
A significant number of patients develop reduced cardiac output lasting up to 7 days after
cardioversion. Acute pulmonary edema after cardioversion is rare, but may be fatal. It may
occur within 3 hours, but may occur as late as 4 days. Virtually all these patients have
underlying heart disease.
With reversion to sinus rhythm, over 4 weeks there was a gradual increase of 56% in
cardiac output. In studies extending 20 months after cardioversion, left ventricular
function improved by 67%.
Archives Int. Med. May 26, 1997; 157: 1070-76 Review article from Piedmont Hospital,
Atlanta, GA
Comment: The heart in atrial fibrillation is an inefficient heart. Despite this, if
the ventricular rate is controlled, patients may remain asymptomatic for years.
Cardioversion is more successful if done early and leads to more sustained sinus rhythm
and a more efficient heart. RTJ
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