EFFECTS OF TEMPORAL DUAL-CHAMBER CARDIAC PACING IN REFRACTORY CARDIAC-FAILURE

The authors studied 18 patients (15 men, 3 women) with an average age of 67 +/- 8 years with refractory cardiac failure. In order to determi ne the potential of pacing to raise cardiac output in severe cardiac f ailure. The average ejection fraction was 26 +/- 6.5 %. All patients w ere in sinus rhythm : resting cardiac output was 3.35 l/min. Two tempo rary pacing catheters were positioned in the right atrium and at the a pex of the right ventricle for dual-chamber mode pacing triggered by t he spontaneous P waves. Changes in cardiac output were measured by Dop pler echocardiography at different Values of atrioventricular delay Pa tients were considered to be responders if their cardiac outputs rose by 15 %. In 7 patients meeting this criterion, the average increase in cardiac output was 27 % (2.99 +/- 0.7 to 3.81 +/- 0.86 l/mn; p < 0.01 ); all had dilated cardiomyopathies with left bundle branch block and the optimal AV delay was 103 +/- 21 ms (80-140 ms); the duration of di astolic filling increased from 212 +/- 98 to 292 +/- 116 ms (p = 0.02) . In the non-responding group (II patients with an increase of cardiac output of only 3.6 +/- 0.09 to 3.9 +/- 0.92 l/mn; p < 0.01), the unde rlying disease process was mainly ischaemic. Two predictive factors of efficacy of dual-chamber pacing were identified : a short ventricular filling period (29 +/- 8 % of the RR interval in the responders vs 44 +/- 9 % in the non-responders; p < 0.01) and the presence of Ist degr ee atrioventricular block. Dual-chamber pacing could be a valuable met hod of increasing resting cardiac outputs in a selected group of patie nts with severe, refractory, cardiac failure.