Andreas Kucher

Understanding the timing cycles of a cardiac resynchronization device designed with left ventricular sensing.

Some devices used for cardiac resynchronization therapy (CRT) can sense from the left ventricular (LV) lead as in Biotronik CRT devices (Biotronik GmbH, Berlin, Germany), whose special LV timing cycles form the basis of this report. LV sensing (LVs) was designed to prevent competitive pacing outside the LV myocardial absolute refractory period. LVs works by inhibiting the release of an LV pacemaker stimulus (LVp) in the vulnerable period of the LV during a programmable period. LVs with stored LV electrograms may also provide recordings of diagnostic value in tachyarrhythmias. LVs has added a new dimension to the evaluation of the function of CRT devices, because it is manifested by unfamiliar timing cycles. In this respect, Biotronik devices can initiate an LV upper rate interval (URI) upon sensing a right‐sided event when LVs is turned off. An inhibited LVp can also initiate an LVURI. The LVURI should generally be programmed to a relatively short duration and shorter than the right ventricular URI to prevent a special form of desynchronization arrhythmia sustained by LVs. This arrhythmia is characterized by recurring delayed LVs events in sequences associated with RV pacing followed by LVs events with loss of LVp.

Dissimilar ventricular rhythms: implications for ICD therapy.

Sensing of left ventricular (LV) activity in some devices used for cardiac resynchronization therapy (CRT) was designed primarily to prevent the delivery of an LV stimulus into the LV vulnerable period. Such a sensing function of the LV channel is not universally available in contemporary CRT devices. Recordings of LV electrograms may provide special diagnostic data unavailable solely from the standard right ventricular electrogram and corresponding marker channel. We used the LV sensing function of Biotronik CRT defibrillators to find 3 cases of dissimilar ventricular rhythms or tachyarrhythmias. Such arrhythmias are potentially important because concomitant slower right ventricular activity may prevent or delay implantable cardioverter-defibrillator therapy for a life-threatening situation involving a faster and more serious LV tachyarrhythmia. Dissimilar ventricular rhythms may not be rare and may account for cases of unexplained sudden death with a normally functioning implantable cardioverter-defibrillator and no recorded terminal arrhythmia.

Pacemaker Rhythm Recorded by a Cardiac Resynchronization Device Capable of Left Ventricular Sensing

A 60-year-old man received a transvenous cardiac resynchronization device (Biotronik Lumax 340 HF-T, Biotronik, Berlin, Germany)1 in 2009 for a nonischemic cardiomyopathy congestive heart failure (left ventricular [LV] ejection fraction = 26%), and complete left bundle branch block. LV pacing and sensing were performed from the tip and ring electrodes of the LV lead. Infrequent intermittent T-wave oversensing by the right ventricular (RV) channel involving only one or two spontaneous beats was first detected in November 2012. The RV sensitivity was left at 0.8 mV but the sensing LV amplifier was turned off. At the time of a follow-up 1 month later, the parameters were as follows: Low rate = 60 pulses per minute (ppm), RV and LV upper rate = 130 ppm (upper rate interval = 460 ms, RVURI = RV upper rate interval, LVURI = LV upper rate interval), postventricular atrial refractory period = 250 ms (475 ms after a ventricular premature complex [VPC]), paced atrioventricular (AV) delay = 100 ms, sensed AV delay = 80 ms, upper threshold = 75% (programmed sensitivity becomes 75% of the maximum, lasting for 350 ms), amplitude mode for detection of the peak R wave, and high pass 1 = 20 Hz, LV lead impedance = 545 Ohms. LV blanking after sensing was 200 ms before the LV-sensing amplifier was turned off. The AV control (AVC) window (discrimination after atrial sensing) was 350 ms, interventricular delay basically zero (triggered delay = 3–5 ms), and triggered function (LV-paced events [LVp]) after RV sensing (RVs) was within the AVC window. The LV sensitivity was not reprogrammed and

P-wave locking in the postventricular atrial refractory period of cardiac resynchronization devices

Electrical desynchronization in cardiac resynchronization therapy (CRT) occurs when sinus P waves are continually locked in the postventricular atrial refractory period (PVARP). This process is characterized by sequences of a P wave as an atrial event in the PVARP followed by a conducted and sensed ventricular event. Such sequences are more common in patients with a prolonged PR interval, often initiated by premature ventricular complexes (PVC) and terminated by PVCs or slowing of the sinus rate. Specific algorithms automatically identify a recurring pattern of P wave locking in the PVARP, whereupon they shorten the PVARP temporarily until atrial tracking is restored with the programmed sensed AV interval. The Biotronik family of Lumax CRT devices use an AV control window which is not an algorithm that “unlocks” P waves trapped in the PVARP. Rather, it prevents P waves from becoming trapped in the PVARP. A ventricular sensed event occurring within the AV control interval does not start a PVARP so that P wave locking cannot occur when the AV conduction time is shorter than the AV control interval.ZusammenfassungZur elektrischen Desynchronisation bei der kardialen Resynchronisierungstherapie („cardiac resynchronization therapy“, CRT) kommt es, wenn Sinus-P-Wellen kontinuierlich innerhalb der postventrikulären atrialen Refraktärzeit („postventricular atrial refractory period“, PVARP) wahrgenommen werden. Dieser Vorgang ist charakterisiert durch Sequenzen mit einer P-Welle als atriales Ereignis innerhalb der PVARP, ohne dass das programmierte AV-Intervall gestartet wird, gefolgt von einem intrinsisch übergeleiteten ventrikulären Ereignis. Solche Sequenzen treten meistens bei Patienten mit verlängerter PR-Zeit auf; sie werden häufig durch ventrikuläre Extrasystolen („premature ventricular complexes“, PVC) angestoßen und durch PVCs mit kompensatorischer Pause oder durch eine Verlangsamung der Sinusfrequenz beendet. Spezielle Algorithmen identifizieren solche rezidivierenden Muster, bei denen P-Wellen innerhalb der PVARP auftreten und verkürzen daraufhin temporär die PVARP, bis das atriale Tracking mit dem programmierten AV-Intervall wieder hergestellt ist. In der „Familie“ der Biotronik-Lumax®-CRT-Geräte wird ein AV-Kontrollfenster verwendet. Das AV-Kontrollfenster ist kein Algorithmus, welcher die P-Wellen aus der PVARP „befreit“, vielmehr verhindert es präventiv, dass P-Wellen in der PVARP wahrgenommen werden. Ein innerhalb des AV-Kontrollintervalls wahrgenommenes ventrikuläres Ereignis startet keine PVARP. Damit wird ein „P-wave locking“ vermieden, solange die AV-Überleitungszeit kürzer ist als das AV-Kontrollintervall.

Rise in ICD shock impedance: lead fracture or death?

Background: Remote monitoring allows for interrogation and extensive data retrieval of implantable cardioverter‐defibrillators (ICDs). Data on ICD parameters at the time of death and afterwards are limited. The purpose of this retrospective study was to examine the changes in lead impedances of ICDs at the time of death and afterwards.

Desynchronization by cardiac resynchronization device related to automatic sensing test

A 69-year-old female with refractory heart failure, left bundle branch block, and a left ventricular ejection fraction of 35% received a Biotronik Intica 7 HF-TQP device (Biotronik, Berlin, Germany) for cardiac resynchronization therapy (CRT) and defibrillation. The parameters wereDDDmode, lower rate 60 ppm, biventricular pacing left ventricle (LV) first, dynamic atrioventricular (AV) delay 130/100 ms, right ventricular upper tracking rate 130 ppm, LVmaximum trigger rate 150 beats/min (LV upper rate with LV upper rate interval [URI] = 400 ms), VV delay 40 ms. Home monitoring (HM) was activated. The device recorded several episodes of interruption of CRT. The monitoring episodes were triggered at 09:29 a.m., 03:29 p.m., and 09:29 p.m. The timedifferencewas exactly 6 hours. Thedesynchronization apparently always occurred during the day, when the heart rate was higher than expected during the night.

The Analog Blanking Period of Implantable Cardiac Rhythm Devices

Analog blanking periods (BPs) that hold down the display of electrograms (EGMs) in cardiac rhythm devices have received much less attention than the well‐known digital BPs which do not influence the EGM display. In Biotronik devices (Biotronik GmbH, Berlin, Germany), when a paced event initiates an analog BP in one chamber (right atrium, right ventricle [RV], or left ventricle [LV]), an identical cross‐chamber analog BP starts in the other two chambers.

Ventricular tachycardia with pseudo-2:1 right ventricular exit block

A 63-year-old man was hospitalized in February 2013 for cardiac resynchronization therapy because of refractory heart failure. The left ventricular (LV) fraction was 25%. He was in atrial fibrillation with a slow ventricular rate and RR pauses of 5 seconds unrelated to drug therapy. Occasional episodes of sustained monomorphic ventricular tachycardia (VT) were also documented. The patient received aBiotronik Lumax640HF-T cardiac resynchronizationdevice (Biotronik, Berlin, Germany) with a defibrillator (CRT-D).1–3 This device is capable of recording the LV electrogram (EGM) in addition to standard recordings (right atrial, right ventricular [RV], and farfield recordings4). Follow-up revealed many VT episodes easily terminated by antitachycardia pacing. In September 2014, stored data in the implantable cardioverter-defibrillator revealed an episode of VT with apparent RV 2:1 exit block.

Undetected ventricular fibrillation in a single-chamber implantable cardioverter-defibrillator: When the far-field channel sees more than the intraventricular channel

Introduction Implantable cardioverter-defibrillators (ICDs) represent the treatment of choice for the prevention of sudden cardiac death. Low signal amplitudes are occasionally encountered during placement of ICDs. ICD implant guidelines state that the amplitude of the sinus rhythm R-wave recorded from the ventricular electrogram should be higher than 5 mV. If no sufficient R signal amplitude can be found despite several attempts of repositioning the ICD lead, an induction of ventricular fibrillation (VF) is useful to ensure that the ICD will sense, detect, and defibrillate VF.

Alternans of the Ventricular Electrogram in Patients with an Implanted Cardioverter‐Defibrillator

The occurrence and significance of alternans of the ventricular electrogram (VEGM) in patients with an implanted cardioverter‐defibrillator (ICD) has been rarely reported.