Left Ventricular Mechanics and Myocardial Blood Flow

Left Ventricular Mechanics and Myocardial Blood Flow The right ventricular apex is still the most usual site for the ventricular electrode in patients who have a permanent pacemaker. The asynchronous ventricular activation and contraction that can result from this kind of pacing have a negative effect on left ventricular (LV) systolic and diastolic function, while also causing regional changes in myocardial perfusion and adrenergic innervation, the pathophysiologic significance of which is not yet clear.
Furthermore, long-term asynchronous ventricular activation leads to remodeling of the LV, with thinning of early-activated regions and thickening of late-activated regions, and also can cause histopathologic lesions in the ventricular myocardium.

To date, it has not been determined whether these structural and functional disturbances that appear after long-term right ventricular apical stimulation are reversible, and if so, to what degree, following the restoration of a normal ventricular activation sequence. This is a matter of great clinical significance, since it is possible that a large number of patients with artificial pacemakers might benefit from a change in pacing mode or by adjustments that ensure as normal an activation sequence as possible.
In order to investigate the reversibility of these functional disturbances, we analyzed LV pressure-volume loops, and evaluated the LV systolic and diastolic function and ventriculoarterial coupling in patients who have received long-term pacing treatment with complete ventricular pacing capture and looked for changes immediately following the restoration of a normal activation sequence. We also studied changes in coronary flow and flow reserve, which may be related to the alteration of LV function.