Vol. 8, No. 1, March 2003 51 Introduction In patients with atrioventricular (AV) block, AV syn- chrony can be restored by implanting biventricular DDD pacing systems if an individual optimization of the pacemaker AV delay is performed. If optimization is not performed, the remaining AV delay (AVD) is left at nominal settings and adverse hemodynamic effects may develop. Several methods have been proposed to calculate or estimate the individual hemodynamic opti- mal length of the AV interval. Depending on the avail- able technology, two principles can generally be applied: • An estimation of the optimal AV delay, which re- quires serial measurement of a hemodynamic para- meter at feasible AV delay steps. • A calculation of the optimal AV delay, which is based on the exact individual measurement of only a few parameters related to time. It is preferred if higher accuracy is required. Independent of the particular optimization method, the results provide either an approximate or exact length of the individual optimal AV delay at any heart rate. Generally, this hemodynamically optimal AV delay varies considerably and is based on the interindividual variation of the actual heart rate. Since automatic AV delay optimization is still under development and the methods discussed are time consuming and require additional procedures, a routine, individualized optimal AV coordination is usually neglected and AV delay is left at nominal settings that depend on the particular pacing system. Since biventricular pacing systems were found to be useful in cardiac resynchronization therapy of patients with chronic heart failure, an increased importance of AV delay optimization has been per- ceived. Thus, further simplification of the AV delay optimization remains a real and unsolved problem. To avoid the expense of a pre-discharge AV delay opti- mization procedure, the aim of our study was to search Progress in Biomedical Research Can the Optimal Atrioventricular Delay Be Predicted Intraoperatively by a Beat-to-Beat Recording of the Peak Endocardial Acceleration? B. ISMER, W. VOSS, J. PLACKE, T. KÖRBER, G.H. VON KNORRE, C.A. NIENABER University of Rostock, Clinic for Internal Medicine, Department of Cardiology, Rostock, Germany G. GAGGINI Sorin Biomedica Cardio, Saluggia, Italy Summary During a pilot study, special ventricular leads were implanted in patients with atrioventricular (AV) block to mea- sure the beat-to-beat recordings of the peak endocardial acceleration (PEA) sensor signal. These measurements were performed in order to assess the possibility of rapidly predicting the optimal intraoperative AV delay in indi- vidual patients. By manually increasing or decreasing the AV delay in a stepwise fashion in both the VDD and DDD modes, the PEA and left atrial esophageal electrogram were simultaneously recorded. These recordings were used to compare the PEA results with the approximate electrocardiographic results for the optimal AV delay. During pre-discharge tests, the results were also compared to the optimal AV delay using Doppler echocardiography. The PEA method yields comparable values to those of the other methods. Key Words Pacing, atrioventicular delay optimization, Peak Endocardial Acceleration (PEA)