Lead switching to resolve undersensing of ventricular tachycardia by a cardiac resynchronization therapy defibrillator.

A 63-year-old man was admitted to the hospital due to ventricular tachycardia (VT) undersensing, caused by decreased R-wave amplitude in a cardiac resynchronization therapy defibrillator. The R-wave amplitude of VT sensed by the left ventricular (LV) lead was markedly higher than that by the right ventricular (RV) lead; therefore, we reconnected the IS-1 RV lead to the LV IS-1 port and the IS-1 LV lead to the RV IS-1 port to resolve this issue. After discharge, it was confirmed that VT was successfully terminated by the second sequence of intrinsic ATP (iATP, Medtronic, Minneapolis, MN, USA) from the LV lead.

Adverse events of subcutaneous loop recorders: Insights from the MAUDE database.

BACKGROUND: Complications using internal cardiac monitors (ICM) have been reported at a low rate. Targeted analyses of complications have not been well described in the literature. OBJECTIVE: To investigate and describe complications associated with ICM events reported to the FDA's Manufacturer and User Facility Device Experience (MAUDE) database. METHODS: Our team reviewed all reported events for the Reveal LINQ loop recorder submitted to the MAUDE database over 7 years (1/1/2013-12/31/2019). A 5% random selection of reports was audited by two researchers to ensure report validity. Two cardiologists manually reviewed death and incongruent events for final interpretation. RESULTS: 12,652 records were obtained during the observed time period. A total of 15,587 device complications were reported. Of this, undersensing (n = 4509, 28.93%), premature discharge of battery (n = 3262, 20.93%), oversensing (n = 2788, 17.89%), and other sensing issues (n = 1532, 9.83%) were most commonly reported. Patient adverse events were reported 1,030 times. Pain or discomfort (n = 275, 26.70%), site infection (n = 213, 20.68%), erosion (n = 138, 13.40%), and impaired healing (n = 49, 4.76%) were most commonly reported to affect patients. Death was reported four times; after expert review, no reports justified the device or procedure as a reasonable cause. CONCLUSION: Several non-life-threatening ICM complications were commonly noted from the analysis. This study supports the safe use of ICMs. A better understanding of the complication profile will help providers select patients, provide informed consent, and expected management.

Leadless pacemaker implantation sites confirmed by computed tomography and their parameters and complication rates.

BACKGROUND: Implantations of leadless pacemakers in the septum lower the risk of cardiac perforation. However, the relationship between the implantation site and the success rate, complication rate, and pacemaker parameters are not well-investigated. METHODS: Patients who underwent leadless pacemaker implantation with postprocedural computed tomography (CT) between September 2017 and November 2020 were analyzed. Septum was targeted with fluoroscopic guidance with contrast injection. We divided patients into two groups based on the implantation site confirmed by CT: septal and non-septal, which included the anterior/posterior edge of the septum and free wall. We compared the complication rates and pacemaker parameters between the two groups. RESULTS: A total of 67 patients underwent CT after the procedure; among them, 28 were included in the septal group and 39 were included in the non-septal group. The non-septal group had significantly higher R wave amplitudes (6.5 ± 3.3 vs. 9.7 ± 3.9 mV, p = .001), lower pacing threshold (1.0 ± 0.94 vs. 0.63 ± 0.45 V/0.24 ms, p = .02), and higher pacing impedance (615 ± 114.1 vs. 712.8 ± 181.3 ohms, p = .014) after the procedure compared to the septal group. Cardiac injuries were observed in four patients (one cardiac tamponade, one possible apical hematoma, two asymptomatic pericardial effusion), which were only observed in the non-septal group. CONCLUSIONS: Leadless pacemaker implantation may be technically challenging with substantial number of patients with non-septal implantation when assessed by CT. Septal implantation may have a lower risk of cardiac injury but may lead to inferior pacemaker parameters than non-septal implantation.

Adverse device-device interaction between pacemaker and subcutaneous implantable cardiac defibrillator.

A 26-year-old patient with prior surgery for Ebstein's anomaly and a pacemaker (placed for post-surgical heart block and poor underlying rhythm) underwent SICD was placement. During defibrillation testing, device-device interaction led to undersensing of ventricular fibrillation with failure to shock. Increasing the pacemaker sensitivity resolved the problem but post shock pacing was unable to capture the heart after both shocks. The patient underwent removal of both the pacemaker and the SICD and placement of a transvenous ICD. Complex device-device interactions can occur in patients who are pacemaker dependent and undergo placement of a SICD.

Diagnostic accuracy of R-wave detection by insertable cardiac monitors.

BACKGROUND: Insertable cardiac monitors (ICM) allow prolonged rhythm monitoring, but the diagnostic performance can be hampered by false positive arrhythmia alerts related to inadequate R-wave sensing. This study assesses the prevalence and predictors of inadequate R-wave sensing (both over- and undersensing) among different ICM types. METHODS: Patients implanted with an ICM at Ghent University Hospital between January 2017 and August 2018 were included. ICM tracings recorded at interrogation or transmitted by remote monitoring were reviewed for inadequate R-wave sensing leading to false arrhythmia alerts. Patient and implant characteristics were retrieved from the medical records and implant reports. RESULTS: The study screened 135 patients (age 59 ± 19 years, 44% female) implanted with different ICM types: Reveal LINQ™ and XT (Medtronic): n = 92 (68%), Confirm and Confirm Rx (Abbott): n = 35 (26%), and BioMonitor 2 (Biotronik): n = 8 (6%). ICM tracings were analyzed in 112 patients (83%). False arrhythmia alerts occurred in 22 (20%) patients, most frequently related to undersensing (77%). False diagnosis of bradycardia or pause was documented in 64%, false high ventricular rates in 14%, and false atrial fibrillation alerts in 22%. Occurrence of R-wave changes was not related to patient characteristics or implant R-wave sensing. A trend toward higher number of inadequate R-wave sensing seems to occur with nonparasternal implant sites (P = .074). CONCLUSIONS: False arrhythmia alerts due to inadequate R-wave sensing occurred in 20% of ICM patients independent of implant features and patient characteristics.

Symptomatic atrioventricular block during biventricular pacing: Facing a double trouble.

Far-field R wave (FFRW) oversensing in atrial channel is known to cause inappropriate automatic mode switch. We describe a case of 63-year-old lady with dual-chamber permanent pacemaker implanted 2 years back for symptomatic infra-hisian complete heart block and normal biventricular function. After 6 months, she underwent upgradation to cardiac resynchronization therapy (CRT-P, Boston Scientific) for right ventricular pacing induced cardiomyopathy. Her LV function normalized after CRT. Later on, FFRW oversensing caused false triggering of an atrial tachycardia, which subsequently opened up an "atrial flutter response" window leading to symptomatic inadvertent atrioventricular block at frequent intervals. Common ways to troubleshoot FFRW oversensing are either by increasing post-ventricular atrial blanking or reducing atrial channel sensitivity. In her case, concomitant P wave under-sensing made the situation more challenging to manage.

Ventricular tachycardia secondary to leadless pacemaker implantation in the setting of myocardial ischaemia.

Leadless pacemakers are increasingly part of the electrophysiology practice and offer an interesting pacing alternative for patients who have a history of CIED infection. We present the case of a patient who developed life-threatening ventricular arrythmias after a leadless pacemaker implant, in the context of previously unrecognised coronary artery disease.

Sensing and Detection Functions in Implantable Cardioverter Defibrillators: The Good, the Bad and the Ugly.

Implantable cardioverter defibrillators are small devices that have been proven to be beneficial by preventing sudden cardiac death, whether in primary or secondary prevention. Appropriate functioning of implantable cardioverter defibrillators is mainly dependent on the "good" sensing of ventricular electrogram waves, allowing for the adequate detection of ventricular arrhythmias in order to deliver appropriate therapy of either antitachycardia pacing or by delivering a shock according to the detected rhythm. Basic sensing function in defibrillators is based on detection rate and detection duration; additional parameters that are involved in the process of adequate detection include ventricular electrogram sensing, auto-adjusting sensitivity, supraventricular arrhythmia discrimination criteria, noise detection, and various dedicated algorithms. Defective sensing may result in the delivery of inappropriate therapy (oversensing) or inappropriate withholding of therapy (undersensing); the latter of which may lead to sudden cardiac death. This paper describes different clinical scenarios and programming tips to avoid abnormal or critical clinical situations.

Switch between AAI and DDD mode pacing-What is the mechanism?

The electrocardiogram (ECG) interpretation in patients with implantable pacemaker is often a perplexing problem. The difficulty in the device evaluation increases in the presence of novel timing cycles and additional functions. Authors describe a special function frequently encountered in Medtronic dual-chamber pacemakers and implantable cardioverter-defibrillator devices called managed ventricular pacing (MVP) and demonstrate its performance in the patient with undersensing episodes in ventricular channel. Intermittent ventricular undersensing in the device with MVP feature turned on caused repetitive mode switches between AAI and DDD mode. This report shows unexceptional occurrence of tricky ECG findings in patient with Medtronic dual-chamber device.

Transient under-sensing of the ventricular lead during abdominal ultrasound as cause of ventricular fibrillation.

Pacemaker-induced arrhythmias represent a very rare complication. Algorithm-induced ventricular tachycardias have been described but this report is the first to describe a ventricular fibrillation caused by transient undersensing of the ventricular lead during an abdominal ultrasound.

Atrial undersensing secondary to quiet timer blanking in pediatric and congenital heart disease patients.

BACKGROUND: Atrial undersensing despite normal atrial lead parameters and high amplitude electrograms has been described in adult patients as a consequence of atrial amplifier saturation. Repetitive inputs cause amplifier ringing and undersensing occurs as a consequence of quiet timer blanking. High amplitude ventricular electrograms can also result in atrial blanking secondary to cross-chamber effect. This has not been described in pediatric patients or epicardial pacing systems and specific risk factors are not known. We describe five cases of atrial undersensing in pediatric and congenital heart disease patients with epicardial dual-chamber systems and high ventricular lead outputs. METHODS: This was a retrospective cohort study of all patients with dual-chamber pacing systems cared for at the Heart Institute at Children's Hospital Colorado. RESULTS: Five cases of atrial undersensing with normal atrial lead parameters were found. All were epicardial systems with acceptable lead parameters at implantation and Medtronic (Medtronic, Inc., Minneapolis, MN, USA) generators with unipolar leads. Ventricular pacing outputs were elevated at presentation, median 5.5 V (5-7.5). Presenting symptoms were exercise intolerance (four) and detection on routine monitoring (one). Successful interventions included reduction in ventricular lead pacing output (one), programming of rate response (two), and implantation of an alternative generator manufacturer (two). CONCLUSION: Atrial undersensing secondary to amplifier ringing and quiet timer blanking is an uncommon presentation but may be clinically important in patients with unipolar epicardial atrial leads and high pacing outputs from ventricular leads.

Spike on T wave! What went wrong?

An 80-year-old male, who previously received a dual chamber pacemaker, was referred to our ambulatory for dizziness and fatigue. The ECG obtained showed sinus rhythm, highly variable atrioventricular (AV) interval and alternation between spontaneous and paced ventricular complexes. A spike on the ascending part of the T wave was observed, suggesting ventricular undersensing. However, telemetry-supported pacemaker control showed inconstant atrial undersensing.

Functional atrial undersensing associated with device algorithm promoting AV conduction.

A 58-year-old woman received a dual chamber pacemaker (Medtronic) for sick sinus syndrome. Given intact AV conduction the Managed Ventricular Pacing mode algorithm (MVP) was programmed. The day after, she suffered from palpitations. Her ECG showed a possible loss of atrial capture accompanied by atrial undersensing. Telemetry-supported pacemaker control confirmed the loss of capture. Undersensing of atrial signal was functional, related to long atrial refractory period in MVP mode algorithm. Device algorithms could induce false suspicions. Awareness about the different pacing algorithms can be useful in order to avoid erroneous interpretations and to correct potential malfunctioning.

A Synergy-Based Optimally Designed Sensing Glove for Functional Grasp Recognition.

Achieving accurate and reliable kinematic hand pose reconstructions represents a challenging task. The main reason for this is the complexity of hand biomechanics, where several degrees of freedom are distributed along a continuous deformable structure. Wearable sensing can represent a viable solution to tackle this issue, since it enables a more natural kinematic monitoring. However, the intrinsic accuracy (as well as the number of sensing elements) of wearable hand pose reconstruction (HPR) systems can be severely limited by ergonomics and cost considerations. In this paper, we combined the theoretical foundations of the optimal design of HPR devices based on hand synergy information, i.e., the inter-joint covariation patterns, with textile goniometers based on knitted piezoresistive fabrics (KPF) technology, to develop, for the first time, an optimally-designed under-sensed glove for measuring hand kinematics. We used only five sensors optimally placed on the hand and completed hand pose reconstruction (described according to a kinematic model with 19 degrees of freedom) leveraging upon synergistic information. The reconstructions we obtained from five different subjects were used to implement an unsupervised method for the recognition of eight functional grasps, showing a high degree of accuracy and robustness.

Delayed AICD therapy and cardiac arrest resulting from undersensing of ventricular fibrillation in a subject with hypertrophic cardiomyopathy-A case report.

Defibrillation testing is no longer routinely performed after automatic implantable cardioverter-defibrillator (AICD) implantation. However, certain subjects undergoing AICD implantation may be at higher risk of undersensing of ventricular arrhythmias resulting in potentially fatal outcomes. We present the case of a 30-year-old woman with hypertrophic cardiomyopathy (HCM; 'asymmetric septal hypertophy' morphologic variant) and prophylactic AICD who experienced an out of hospital cardiac arrest. AICD interrogation revealed undersensing as a result of intermittent high amplitude electrograms during an episode of ventricular fibrillation (VF). The subject underwent replacement and repositioning of the AICD lead along with pulse generator replacement (that utilized a different VF sensing algorithm) with appropriate sensing of VF and successful defibrillation testing. The presence of intermittent high amplitude electrograms during episodes of VF in AICDs using the AGC function should be recognized as a situation that may necessitate interventions to prevent undersensing and consequent delay in therapy.

Detecting deceased patients on cardiac device remote monitoring: A case series and management guide for cardiac device services.

BACKGROUND: Remote monitoring (RM) of implantable cardiac devices provides substantial and complex information, presenting new challenges such as detection of a patient's death. OBJECTIVE: This study aims to describe RM transmissions indicating death and propose a management strategy for services. METHODS: The study included consecutive ambulatory outpatients whose deaths were detected via RM. Clinical and device data were collected from electronic records, and ethical approval was obtained from the service's institutional review board. RESULTS: Over a 9-year period (2014-2023), 28 patients were detected. The deceased patients had implantable cardioverter-defibrillators, pacemakers, and implantable loop recorders. In 54% of the cases, the patient's death had already been recognized. Alert transmissions indicating death were commonly related to ventricular arrhythmia events, but also due to lead measurements, and implantable loop recorder battery status. Several diagnostic features may indicate a patient's death. The most reliable was the presenting electrogram, demonstrating base rate pacing with no capture. Device diagnostics, lead parameters, and arrhythmia recordings may indicate death; however, not all cases present with recordings and diagnosis may not be conclusive. A majority (82%) had ventricular arrhythmia at the time of death. In cases where defibrillator shocks were delivered, the arrhythmia reinitiated shortly after successful cardioversion. Delayed therapy was observed, and some patients did not receive defibrillator shocks because of discriminators or because the arrhythmia rate fell below the shock zone. CONCLUSION: Detecting a patient death via RM presents unique challenges and considerations for services. Standard operational policies and legal consultation should be established to address the implications.

Failure to treat ventricular tachycardia or ventricular fibrillation by implantable cardioverter-defibrillators.

BACKGROUND: Normally functioning implantable cardioverter-defibrillators (ICDs) with intact lead systems occasionally fail to deliver therapy for ventricular tachycardia/fibrillation (VT/VF) or deliver it only after clinically significant delays (failure-to-treat). OBJECTIVE: We aimed to investigate ICD failure-to-treat VT/VF in a large patient cohort. METHODS: We searched the US Food and Drug Administration's online Manufacturer and User Facility Device Experience (MAUDE) database from 2019 to 2023 for manufacturer-verified reports in which normally functioning ICDs failed to treat VT/VF. RESULTS: We identified 854 reports classified as deaths (n = 96 [11.2%]), injuries (n = 585 [68.5%]), or malfunctions (n = 173 [20.3%]) for normally functioning ICDs. The most common causes were misclassification as supraventricular tachycardia (SVT) or atrial fibrillation (AF; 54.8%), undersensing (21.1%), and failure to satisfy programmed rate/duration criteria (8.7%). Most events caused by misclassification as SVT/AF (89.5%) and failure to satisfy rate/duration criteria (70.3%) were VT; most caused by undersensing were either VF (54.4%) or not specified as VT or VF (19.4%). Undersensing caused 65.6% of deaths, although it represented only 21.1% of reports. In the United States, the number of reports increased faster than that of ICD patients. CONCLUSION: In the largest reported series of failure-to-treat VT/VF by normally functioning ICDs, the most common cause was misclassification of VT as SVT/AF; the most common cause of death was undersensing of VF. Although relatively few patients with normally functioning ICDs experience failure-to-treat VT/VF, the absolute number of verified MAUDE reports suggests that more work is needed to quantify the magnitude of the problem, to identify root causes, and to develop solutions.