Atrial overdrive pacing increased the percentage of atrial pacing from 30 % to 80 % ( P < .0001 ) , was well tolerated , and did not interfere with ( a ) delivery of CRT ( 95 % mean ventricular pacing in both groups ) , ( b ) response to CRT ( 70 % responders in the control vs 67 % in the treatment group ) , or ( c ) cardiac function ( left ventricular ejection fraction increased from 24.5 % + / - 6.2 % to 32.7 % + / - 10.9 % in the control and from 25.8 % + / - 6.8 % to 33.1 % + / - 12.6 % in the treatment group ) .
