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A new pacing method for rapid regularization and rate control in atrial fibrillation.

In 15 patients with atrial fibrillation (AF), a single right ventricular extrastimulus (intercalated pacing) was delivered after every sensed conducted beat resulting in a reduction in rate. This method was used in 10 patients with lone AF and the average success rate of inducing coupling was 86 +/- 14% (range 64 to 100), using a mean coupling interval of 232 +/- 28 ms (range 175 to 290). During intercalated pacing, the pulse rate of AF was reduced (from 137 +/- 26 to 75 +/- 14 beats/min, p less than 0.001). Intercalated pacing resulted in enhancement of mean stroke volume (28 +/- 6 vs 44 +/- 10 ml in AF, p less than 0.0001), pulse pressure and the pulse-to-pulse regularity. Both the systolic and diastolic arterial pressures were regularized. The reduction in pulse rate during intercalated pacing was determined by the coupling interval, and the induction of concealed ventriculoatrial conduction (82 +/- 44 ms). Myocardial lactate extraction was similar during AF and short-term intercalated pacing (28 +/- 10 vs 25 +/- 9%, difference not significant). In 5 patients with severe mitral stenosis in AF, intercalated pacing resulted in an improvement in the cardiac output (3.1 +/- 0.2 vs 3.4 +/- 0.2 liters/min, p less than 0.04), a reduction in the gradient across the mitral valve (16 +/- 8 vs 10 +/- 5 mm Hg, p less than 0.02), and a reduction in pulmonary arterial and wedge pressures. This new pacing method thus achieved rapid temporary control of rate, regularity and cardiac hemodynamics during AF, which were more prominent in patients with mitral stenosis and restricted left ventricular filling.