the ventricular stimulus (Vp) is measured. 2. Then the preset AV delay (in this case 150 ms) is corrected by the amount the measured LA-Vp interval is deviating from the target value (70 ms in AV block and 50 ms in congestive heart failure patients, respectively). The resulting AV delay (prolonged if LA-Vp is shorter, shortened if LA-Vp is longer than the target value) is the approximate optimal AV interval for atrial sensing. After programming this optimal AV delay, the best possible approximation of the interval LA-Vp to the target value can be checked in the LAE. Measuring of „negative“ LA-Vp interval of -18 ms in VDD operation in a patient with Medtronic CRT system using the Biotronic ICS3000 programmers left heart electrogram feature. In this case, factory SAV of 100 ms presents an “unphysiologically short” AV delay truncating or even excluding an atrial contribution to the left ventricular filling. Approximation of the optimal sensed AV delay in the same CRT patient of the previous figure. Programming SAV of 170 ms instead of factory setting of 100 ms results into LA-Vp of 52 ms which represents approximately the mean value of a CRT patient cohort. In this case the ventricular stimulation starts immediately after the left atrial deflection has finished. The individually optimized electromechanical interval This is the AV delay component that can be individually optimized. During diastolic optimization, it can be determined from the difference of two time intervals that can be measured by echo. These are the following: 1. The duration of the left atrial electromechanical action (LA-EAClong) is measured during an AV interval programmed to be non-physiologically long (about 200 ms longer than As-LA). It is measured from the beginning of the left atrial deflection (LA) in the esophageal electrogram to the undisturbed end of the left atrial contribution to the left ventricular filling (EAClong), which can be detected in the mitral flow image. 2. The duration of the left ventricular latency period (Vp-EACshort) is measured during DDD pacing with an AV interval programmed to be non-¬physiologically short (about 20 ms shorter than Ap-LA). It is measured from the ventricular stimulus Vp and the prematurely truncated end of the left atrial contribution, to the left ventricular filling (EACshort) in the mitral flow. This description emphasises that the hemodynamic optimization of the AV delay always consists in the individual optimization of only its electromechanical share. The individual share