Herzschr Elektrophys 2012 · 23:135–140 DOI 10.1007/s00399-012-0175-0 Received: 7 April 2012 Accepted: 28 April 2012 Published online: 3 June 2012 © Springer-Verlag 2012 S.S. Barold 1 · M. Steiner 2 · A. Kucher 3 · R.X. Stroobandt 4 1 Florida Heart Rhythm Institute, Tampa, USA 2 Cardiology, Kantonsspital, Aarau, Switzerland 3 Biotronik, Berlin, Germany 4 University Hospital Ghent, Belgium Unusual cause of desynchronization in a cardiac resynchronization device There are many causes of desynchroni- zation during pacing with cardiac resyn- chronization devices. In this report, we present a new cause of desynchronization that occurs under unusual circumstances and is related to device design. Case report Several years ago, a man with arrhyth- mogenic right ventricular dysplasia re- ceived an implantable cardioverter–defi- brillator (ICD). He was a survivor of sud- den death. The left ventricle eventual- ly became involved with the progression of disease (left ventricular ejection frac- tion 25%). At the time of the original ICD implantation, the right atrium was elec- trically silent with inability to pace or sense. Therefore, a single chamber ICD was implanted. The ICD was replaced in May 2011 with a Biotronik Lumax HF-T (Biotronik, Berlin, Germany) [1] cardi- ac resynchronization ICD device because the patient exhibited a junctional rhythm with a left bundle-branch block configu- ration. The atrial port was closed with a blind plug. The atrial blind plug has no in- built terminal resistor—electrically, like an open circuit. Initially, with an atrial sensi- tivity of 0.4 mV the atrial lead impedance was >3000 Ω. Several weeks later, the atri- al channel was deactivated according to a protocol provided by Biotronik. The pa- rameter “atrial sensing” was programmed to off. Therefore, the atrial channel did not display atrial electrograms, markers and impedance. There was no evidence of phantom crosstalk in the atrial channel [2, 3]. The low rate was programmed at 60 ppm, while the maximum sensor rate was programmed to 130 ppm (. Fig. 1). The device was initially programmed with a left ventricular (LV) maximum trigger rate of 150 ppm as recommended by Bio- tronik in this situation. The V-V interval remained at 5 ms throughout the follow- up period. The LV maximum trigger rate was reprogrammed to 100 ppm in Febru- ary 2012 without any documentation. A month later, the ICD delivered a shock for fast ventricular tachycardia. At this time, it was noticed that left ventricular pac- ing disappeared when the sensor-driven rate exceeded 100 ppm. LV sensing was preserved (. Fig. 2). The duration of the stored pre-episode was not long enough to determine when LV pacing disappeared. The original LV maximum trigger rate of 150 ppm rate was restored and no further episodes of desynchronization have oc- curred. During follow-up since implantation the patient received two appropriate suc- cessful shocks and effective antitachycar- dia therapy. There was no correlation be- tween these events and the development of desynchronization. The unusual loss of LV pacing was evaluated with a heart simulator and a working-demo to replicate the scenar- io. This required shaking of the working- demo for a long time until the accelerom- eter rate exceeded 100 ppm to show the sudden loss of LV pacing (. Fig. 3, 4). Discussion There was no evidence of phantom cross- talk so the device functioning in the VVIR mode did not sense the atrial rate [2, 3]. All atrial-related statistical information was not displayed in the pacemaker sta- tistics. A deactivated atrial sensing ampli- fier prevents any type of undesirable atri- al oversensing such as noise, far-field sig- nals and crosstalk in the atrial channel which would be a possible risk if retain- ing the high-ohmic input of the unused atrial amplifier. The mechanism of desynchroniza- tion was determined with an external de- vice of the same model. The same desyn- chronization switch was demonstrated with a programmed LV maximum trigger rate of 100 ppm and a rate adaptive max- imum rate of 130 ppm when the senor- driven rate was faster than the LV max- imum trigger rate. The simulation study also showed that return of effective LVp will occur at a rate substantially slower than the LV upper rate when the sensor- driven interval becomes longer than the sum of the LVURI+intraventricular con- duction time. This is simply due to a de- sign that inhibits LV pacing when the sen- sor-driven rate is faster than the LV max- imum trigger rate. As shown in Fig. 3 and Fig. 4, the LV maximum trigger rate in- terval is really an LV upper rate interval. Case Report 135 Herzschrittmachertherapie + Elektrophysiologie 2 · 2012 |