Using telemetry, right atrial electrogram (RA), and marker channel of atrial sense events (MA) in combination with the left atrial electrogram (LA), recorded by a filtered bipolar esophageal lead, interatrial conduction during submaximal exercise and at rest was examined in 46 DDD pacemaker patients. The RA-LA and MA-LA conduction times measured in the presence of atrial sensing (VDD) as well as the conduction time SA-LA from atrial stimulus (SA) to LA, determined during atrial pacing (DDD) were found to be individual constants independent of exercise induced sympathetic influences. Thus, having determined an optimal mechanical interval (LA-LV)mech/opt from left atrium to ventricle by other methods, the optimal AV delay for DDD as well as for VDD operation can be calculated by the sum of the appropriate interatrial conduction time (SA-LA, respectively MA-LA) and the (LA-LV)mech/opt interval. Due to the constant SA-LA and MA-LA, the difference between these two values (AV delay correction interval) is a constant as well, which remains unchanged during exercise. Therefore, in selecting the rate responsive AV delay, only hemodynamic and not electrophysiological measurements need to be considered.

TI is a new method of evaluation based on baseline VCG analysis. It may be a useful diagnostic test for predicting acute hemodynamic response to CRT.

Cardiac resynchronization therapy (CRT) is an accepted treatment for congestive heart failure (NYHA III-IV), but a substantial number of patients show no response to therapy. LBB, QRS width and echocardiographic measurements are parameters for indication, but they are not valid to predict hemodynamic response. A new method based on vector ECG analysis can deliver additional information, such as: parts or areas with late excitation, and with slow or fast depolarization speed. Electrical excitation is a prerequisite for contraction; this leads to the hypothesis that areas with late electrical activation will contract later. Algorithms for analysis of the vector ECG (determination of the vector -- time, area and speed) may help to identify responders and non-responders.

The individual adjustment of the AV intervals is a prerequisite for the hemodynamic advantages of dual-chamber pacing. The methods for the optimization of the AV-Delay (AVD) applied so far are time intensive. A simple and fast method is the approximate adjustment of the AVD with the surface-ECG. The aim of this work is the conception and validation of this new method. The optimal AVD is given if at the end of the atrial contraction the mitral valve is closed by the ventricular increase of pressure. In order to achieve this with pacemaker patients, the individually different atrial and ventricular conduction times must be considered. The different conduction times can be determined from the surface-ECG. Intra- and interatrial conduction times can be defined by the beginning of the atrial spike up to the end of the p-wave. The beginning of ventricular pressure increase corresponds to the peak of the stimulated QRS complex (beginning of the Iso-Volumetric Contraction time, ISVC) and depends on the interventricular conduction time.¶   In the case of 100 patients, who did not receive a cardiac pacemaker, the interval at the end of the p-wave (left atrial excitation, EP) up to the peak of the r-wave (ISVC) during rest and exercise was measured and an age referred average value of 100ms determined; this serves as standard value if no AV-conduction is available. The approximated optimized AVD is given if the interval of the end at the p-wave to the peak of the QRS-Complex amounts to 100ms. By means of a simple algorithm, the optimized AVD can, thus, be calculated:¶   After programming a long AVD, the interval at the end of the native or paced p-wave up to the peak of the stimulated QRS-Complex (EP/ISVC) is determined. This value EP/ISVC is then taken from the long AVD, the 100ms standard value is added and one receives the approximately optimized AVD.¶   In order to validate the described method, 13 consecutive patients (2 female, 11 male, average age 67±7.8 years) were included, and received for different indication (7 sick sinus syndrome, 4 AV block III, 2 binode disease) a DDD pacemaker (Affinity, St. Jude Medical).¶   About 8 weeks after implantation all patients underwent a PA catheter investigation, in order to optimize the AV-/PV-Delay of the pacemaker regarding the maximum cardiac output (CO). For CO measurement the thermo dilution method was applied. Altogether 17 complete hemodynamic measurements (9 times with different PVDs, 8 times with different AVDs) were executed. The patients 10-13 could be examined both in the VDD and in the DDD mode.¶   The minimum determined CO amounted to 3.5 l/min, the maximal CO 7.1 l/min and the average value was 5.62±0.98 l/min. In all patients not only one optimal AVD was found but, moreover, a varied interval of AVDs with which optimal CO results could be obtained. The comparison of surface ECG optimized AVD with the PA catheter optimized AVD showed a statistically significant correlation (0.825PV, 0.982 AV, P<0.01). Sixteen out of seventeen measurements were at an interval whic...

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