Utility of two-dimensional and Doppler echocardiography in dual-chamber pacing for the cardiomyopathies.

. The proposed mechanism for benefitis a reduction in left ventricular outflow tract obstructiondue to altered septal activation from pacing the right ven-tricular apex. This interrupts the sequence of events (septalencroachment into the outflow tract with resultant systolicanterior motion of the mitral valve) that causes the outflowobstruction. There may also be a longer term remodelingeffect from continuous pacing causing ventricular dilata-tion and even regression of hypertrophy