AV-Delay Optimization According to the Right Ventricular Intracardiac Impedance

Since its advent in 1969, the dual-chamber pacing has been regarded as "physiologic pacing." This concept later evolved into "true physiologic pacing", when sensors for rate-adaptive pacing were added to dual-chamber devices to improve hemodynamic performance in chronotropically incompetent patients. The next step along the path of progress in physiologic pacing is optimization of atrioventricular (AV) synchrony in patients with impaired dromotropic response. In a normal heart, cardiac output (CO) is regulated by several physiologic factors, among them the AV delay. Optimization of the CO in DDD patients requires that atrial and ventricular contractions are appropriately timed. An optimal AV delay (OAVD) allows completion of the end-diastolic filling flow prior to ventricular contraction, thus providing the longest diastolic filling time. A long programmed AV delay would produce a mitral pre-systolic insufficiency, thus decreasing the ventricular filling. A short programmed AV delay would produce an early interruption of the active ventricular filling. Modern dual-chamber pacemakers provide a wide range of programmable AV intervals, fixed