of implant-related interatrial conduction times in the total duration of the optimal AV delay, can be considerably but must be accepted as a given. It can be influenced intraoperatively by the choice of the lead position in the right atrium. The overall duration of the optimal AV delay thus results for both modes as the sum of the implant-related individual interatrial conduction time (IACT) valid for the respective mode (VDD or DDD) and the individually optimal electromechanical interval. This advanced principle avoids all limitations and pitfalls of an AV delay optimization according to Ritter et al.. In contrast to the interatrial conduction intervals, the individually optimized electromechanical interval LA-Vp as the difference in the intervals LA-EAClong and Vp-EACshort, has always the same duration for VDD and DDD pacing. It could be shown that this duration is on average about 70 ms in patients with AV block and unimpaired left ventricular function. In patients with congestive heart failure and left bundle branch block, on the other hand, an average value of about 50 ms was found. References Ismer B, von Knorre GH, Voß W. Digitales Ösophagus-Speicher-EKG - Eine neue Methode zur Schrittmacher- und Rhythmusdiagnostik unter Langzeit- und Belastungsbedingungen. Biomedizinische Technik 1994; 39: 258-259 Ismer B, von Knorre GH, Voß W, Beyer F. Modifizierter Speicher-EKG-Rekorder zur Rhythmus- und Schrittmacherkontrolle durch Einbeziehung einer Ösophagusableitung. Herzschr Elektrophys 1992; 3: 28-33 Ismer B, von Knorre GH, Voß W. Eine kompakte Basiseinheit für die Ableitung von Elektrokardiogrammen zur Rhythmusanalyse. Z klin Med 1986; 41: 703-704 Ismer B, von Knorre GH, Voß W. Zur Optimierung intrakardialer Elektrogramme durch den Einsatz aktiver Filter mit variablen Frequenzgrenzen. Dt. Gesundh.-Wesen 1983; 38: 154-158 Ismer B: Utilization of the Esophageal Left Heart Electrogram in Cardiac Resynchronization and AV Block Patients. Hochschule Offenburg, Offenburg 2013, Cardiovascular physiology