V. CLASSIFICATION AND MANAGEMENT A. Acute Atrial Fibrillation
An episode of atrial fibrillation observed within 48 h of its onset is described as acute. If the ventricular rate is greater than 160 beats per minute and results in acute cardio¬vascular decompensation manifested by hypotension, shortness of breath, chest pain, confusion, or heart failure, the rhythm should be converted to normal sinus rhythm. DC cardioversion is usually the initial treatment of choice.
Figure 3A shows the ECG tracing of a patient with acute atrial fibrillation and a fast ventricular rate of 160 beats per minute. Figure 3B shows the same patient hours later after the rate had been decreased by a beta-blocking drug. It also shows spontaneous reversion to normal sinus rhythm. The diagnostic points of the ECG are as follows: the rhythm is completely irregular, the R-to-R intervals are irregular, there are no visible P-waves, and the baseline shows irregular undulations.
If there are no signs of cardiovascular decompensation and the arrhythmia is well-tolerated, diltiazem (a calcium antagonist), esmolol, or other beta-blocking drugs administered intravenously can be used to slow the ventricular response to less than 110 beats per minute, with the hope that normal sinus rhythm may return spontaneously within 12–24 h of onset. Sinus rhythm may return spontaneously if atrial fibrillation is due to an extracardiac cause that is corrected or if the left atrium is not enlarged. If spontaneous sinus rhythm does not occur, conversion to sinus rhythm may be attempted with pharmacologic agents such as ibutilide.
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