Failure to defibrillate or cardiovert due to premature truncation of biphasic shocks from implantable defibrillators.

BACKGROUND: In 2022 and 2023, Medtronic recalled implantable defibrillators because they may deliver less than full-energy shocks. The 2022 problem truncates the second phase of the waveform (SCP-T2), resulting in ∼32-J shocks, and is mitigated by downloadable software. The 2023 malfunction truncates the first phase of the waveform, resulting in 0- to 12-J shocks due to a glassed feedthrough problem (GFT-T1) that might be avoided by programming B>AX shock polarity. OBJECTIVE: The purpose of this study was to assess the consequences of GFT-T1 and SCP-T2 shocks in the Food and Drug Administration's Manufacturers and User Facility Device Experience (MAUDE) database and to estimate the incidences of GFT-T1 and SCP-T2. METHODS: We analyzed MAUDE reports supplemented by Medtronic data; lead failures were excluded. The incidences of SCP-T2 and GFT-T1 were estimated using USA volumes for devices with glassed feedthroughs. RESULTS: One hundred thirty-two devices delivered truncated shocks: 27 (20.5%) were GFT-T1; 103 (78.0%) were SCP-T2; and 2 (1.5%) truncated both phases (BOTH-T1&2). Of 54 ventricular fibrillation (VF) patients, 21 (38.9%) were not defibrillated by truncated shocks: 8 (38.1%) received GFT-T1 shocks, 12 (57.1%) received SCP-T2 shocks, and 1 received a BOTH-T1&2 shock; 2 patients suffered unrelated deaths; 1 was externally rescued; 1 outcome was unknown; the others were defibrillated by subsequent shocks or terminated spontaneously. The majority of patients (79.1%) shocked for ventricular tachycardia (VT) were converted, primarily (94.1%) by SCP-T2 shocks. Estimated incidences of GFT-T1 and SCP-T2 were 0.0078%-0.0088% and 0.1062%-0.1110%. CONCLUSION: GFT-T1 and SCP-T2 shocks can result in failure to terminate VF/VT, but they may be preventable. Although the incidences of these truncated shocks are very low, heightened surveillance is warranted.

Post-Shock Asystole in Patients Dying Out of Hospital While Wearing a Cardioverter Defibrillator.

BACKGROUND: The wearable cardioverter-defibrillator (WCD) prevents sudden cardiac death due to ventricular tachycardia (VT) or ventricular fibrillation (VF) but does not pace for post-shock asystole (PS-A) or bradycardia (PS-B;<50 beats/ min). OBJECTIVES: The purpose of this study was to assess PS-A and PS-B in patients dying out of hospital (OOH) while wearing a WCD. METHODS: The database of the U.S. Food and Drug Administration Manufacturers and User Facility Device Experience (MAUDE) was queried for manufacturers' reports of OOH deaths while patients were wearing a WCD. Excluded were patients who did not receive a shock or were initially shocked for asystole or during resuscitation. RESULTS: From January 2017 to March 2022, 313 patients received an initial WCD shock for VF (n = 150), VT (n = 90), and non-VF/VT rhythms (n = 73). PS-A occurred in 204 patients (65.2%), and PS-B occurred in 111 (35.5%); 85 (41.7%) PS-A patients also had PS-B. Most PS-A patients (n = 185; 90.7%) had an initial shocked rhythm of VF or VT, but 19 patients (9.3%) were initially inappropriately shocked for atrial fibrillation/supraventricular tachycardia (n = 7) and idioventricular (n = 8) or sinus (n = 4) rhythm. PS-A occurred after the first WCD shock in 118 (63.8%) and after the first, second, or third shocks in 159 patients (85.9%). Seven patients had post-shock heart block. Eight patients had permanent pacemakers; 1 became nonfunctional after 1 shock, and 7 showed noncapture and/or asystole after 1 to 4 shocks. CONCLUSIONS: Post-shock asystole appears to be common in patients who die OOH after being shocked by a WCD for VF or VT. PS-A also occurs after inappropriate WCD shocks for non-VF/VT rhythms. Implanted pacemakers may not prevent PS-A after a WCD shock. WCD backup pacing should be explored.

Causes and clinical consequences of inappropriate shocks experienced by patients wearing a cardioverter-defibrillator.

BACKGROUND: The LifeVest® wearable cardioverter-defibrillator (WCD) prevents sudden cardiac death in at-risk patients who are not candidates for an implantable defibrillator. The safety and efficacy of the WCD may be impacted by inappropriate shocks (IAS). OBJECTIVE: The purpose of this study was to assess the causes and clinical consequences of WCD IAS in survivors of IAS events. METHODS: The Food and Drug Administration's Manufacturers and User Facility Device Experience database was searched for IAS adverse events (AE) that were reported during 2021 and 2022. RESULTS: A total of 2568 IAS-AE were found (average number of IAS per event: 1.5 ± 1.9; range 1-48). IAS were caused by tachycardias (1255 [48.9%]), motion artifacts (840 [32.7%]), and oversensing (OS) of low-level electrical signals (473 [18.4%]) (P <.001). Tachycardias included atrial fibrillation (AF) (828 [32.2%]), supraventricular tachycardia (SVT) (333 [13.0%]), and nonsustained ventricular tachycardia/fibrillation (NSVT/VF) (87 [3.4%]). Activities responsible for motion-induced IAS included riding a motorcycle, lawnmower, or tractor (n = 128). In 19 patients, IAS induced sustained ventricular tachycardia or ventricular fibrillation that subsequently were terminated by appropriate WCD shocks. Thirty patients fell and suffered physical injuries. Conscious patients (n = 1905) did not use the response buttons to abort shocks (47.9%) or used them improperly (20.2%). IAS resulted in 1190 emergency room visits or hospitalizations, and 17.3% of patients (421/2440) discontinued the WCD after experiencing IAS, especially multiple IAS. CONCLUSIONS: The LifeVest WCD may deliver IAS caused by AF, SVT, NSVT/VF, motion artifacts, and oversensing of electrical signals. These shocks may be arrhythmogenic, result in injuries, precipitate WCD discontinuation, and consume medical resources. Improved WCD sensing, rhythm discrimination, and methods to abort IAS are needed.

Leadless pacemaker perforations: Clinical consequences and related device and user problems.

BACKGROUND: Cardiac perforation during leadless pacemaker implantation is more likely to require intervention than perforation by a transvenous lead. This study reports the consequences of Micra pacemaker perforations and related device and operator use problems based on information the manufacturer has submitted to the Food and Drug Administration (FDA). METHODS: FDA's Manufacturer and User Facility Device Experience (MAUDE) database was searched for Micra perforations. Data extracted included deaths, major adverse clinical events (MACEs), and device and/or operator use problems. RESULTS: Between 2016 and July 2021, 563 perforations were reported within 30 days of implant and resulted in 150 deaths (27%), 499 cardiac tamponades (89%), 64 pericardial effusions (11%), and 146 patients (26%) required emergency surgery. Half of perforations were associated with 139 (25%) device problems, 78 (14%) operator use problems, and 62 (11%) combined device and operator use problems. Inadequate electrical measurements or difficult positioning were the most frequent device problems (n = 129); non-septal implants and perforation of other structures were the most frequent operator use problems (n = 69); a combined operator use and device problem resulted in 62 delivery system perforations. No device or operator use problem was identified for 282 perforations (50%), but they were associated with 78 deaths, 245 tamponades, and 57 emergency surgeries. CONCLUSION: The Micra perforations reported in MAUDE are often associated with death and major complications requiring emergency intervention. Device and use problems account for at least half of perforations. Studies are needed to identify who is at risk for a perforation and how MACE can be avoided or mitigated.

Acute Myocardial Infarction-Like Events in Related Patients With a Desmoplakin-Associated Arrhythmogenic Cardiomyopathy.

Patients with familial arrhythmogenic cardiomyopathy typically present with ventricular arrhythmias or progressive heart failure. This paper characterizes a rare presentation of an underlying genetic cardiomyopathy with clinical manifestations mimicking an acute myocardial infarction in 2 siblings, each with the same mutation in the desmoplakin (DSP) gene. (Level of Difficulty: Advanced.).

Major adverse clinical events associated with implantation of a leadless intracardiac pacemaker.

BACKGROUND: Leadless intracardiac pacemakers were developed to avoid the complications of transvenous pacing systems. The Medtronic Micra™ transcatheter pacemaker is one such system. We found an unexpected number of major adverse clinical events (MACE) in the Food and Drug Administration's Manufacturers and User Facility Device Experience (MAUDE) database associated with Micra implantation. OBJECTIVE: The purpose of this study was to describe these MACE and compare them to implant procedure MACE in MAUDE for Medtronic CapSureFix™ active-fixation transvenous pacing leads. METHODS: During January 2021, we queried the MAUDE database for reports of MACE for Micra pacemakers and CapSureFix leads using the simple search terms "death," "tamponade," and "perforation." Reports from 2016-2020 were included. RESULTS: The search identified 363 MACE for Micra and 960 MACE for CapSureFix leads, including 96 Micra deaths (26.4%) vs 23 CapSureFix deaths (2.4%) (P <.001); 287 Micra tamponades (79.1%) vs 225 tamponades for CapSureFix (23.4%) (P <.001); and 99 rescue thoracotomies for Micra (27.3%) vs 50 rescue thoracotomies for CapSureFix (5.2%) (P <.001). More Micra patients required cardiopulmonary resuscitation (21.8% vs 1.1%) and suffered hypotension or shock (22.0% vs 5.8%) than CapSureFix recipients (P <.001). Micra patients were more likely to survive a myocardial perforation or tear if they had surgical repair (P = .014). CONCLUSION: Micra leadless pacemaker implantation may be complicated by myocardial and vascular perforations and tears that result in cardiac tamponade and death. We estimate the incidence is low (<1%). Rescue surgery to repair perforations may be lifesaving. MACE are significantly less for implantation of CapSureFix transvenous ventricular pacing leads.

Reliability and longevity of implantable defibrillators.

PURPOSE: We hypothesized that data in manufacturers' product performance reports (PPRs) can provide clinically valuable ICD and cardiac resynchronization defibrillator (CRT-D) reliability and longevity information. METHODS: Data were obtained from 2019 PPRs. Kaplan-Meier (K-M) probabilities of freedom from malfunction, normal battery depletion (NBD), and NBD + malfunction were calculated for ICD and CRT-D pulse generators (PGs) with LiMnO2 or LiSVO/CFx batteries marketed in the USA from 2010 to 2019 and compared using the log-rank test. Malfunctions (MAL) included PGs that were found outside specifications. RESULTS: Study population included 1,149,803 ICD and CRT-D PGs: Abbott (ABT; 35.1%), Biotronik (BIO; 4.6%), Boston Scientific (BSC; 23.5%), and Medtronic (MDT; 36.9%). Significant differences in reliability (p < 0.001), defined by freedom from MAL, were found between manufacturers; the majority of 6808 MAL occurred in ABT devices (n = 4045; 59.4%), followed by BSC (n = 2384; 35.0%), MDT (n = 338;5.0%), and BIO (n = 41; 0.6%). Battery failure (n = 890; 57.9%) was the most common cause of MAL compromising therapy; analysis of unique ABT battery MAL-indicated problem appeared a year prior to advisory. Significant differences (p < 0.001) in battery longevity, as defined by freedom from NBD, were found between manufacturers. Overall performance (freedom from NBD + MAL) favored BSC for CRT-D PGs and MDT and BIO for ICDs. BSC subcutaneous ICD reliability was inferior to its transvenous ICD (p < 0.001). CONCLUSION: PPRs contain valuable data that can be aggregated and analyzed to inform physicians. Differences in product reliability exist between manufacturers. Battery longevity has improved, but MAL have significantly impacted performance. PPR data may be useful for assessing product problems and new technology.

Autosomal-dominant biventricular arrhythmogenic cardiomyopathy in a large family with a novel in-frame DSP nonsense mutation.

A novel autosomal-dominant in-frame deletion resulting in a nonsense mutation in the desmoplakin (DSP) gene was identified in association with biventricular arrhythmogenic cardiomyopathy across three generations of a large Caucasian family. Mutations that disrupt the function and structure of desmosomal proteins, including desmoplakin, have been extensively linked to familial arrhythmogenic right ventricular cardiomyopathy (ARVC). Analysis of data from 51 individuals demonstrated the previously undescribed variant p.Cys81Stop (c.243_251delCTTGATGCG) in DSP segregates with a pathogenic phenotype exhibiting variable penetrance and expressivity. The mutation's pathogenicity was first established due to two sudden cardiac deaths (SCDs), each with a biventricular cardiomyopathy identified on autopsy. Of the individuals who underwent genetic screening, 27 of 51 were heterozygous for the DSP mutation (29 total with two obligate carriers). Six of these were subsequently diagnosed with arrhythmogenic cardiomyopathy. An additional nine family members have a conduction disorder and/or myocardial structural changes characteristic of an evolving condition. Previous reports from both human patients and mouse studies proposed DSP mutations with a premature stop codon impart mild to no clinical symptoms. Loss of expression from the abnormal allele via the nonsense-mediated mRNA decay pathway has been implicated to explain these findings. We identified an autosomal-dominant DSP nonsense mutation in a large family that led to SCD and phenotypic expression of arrhythmogenic cardiomyopathy involving both ventricles. This evidence demonstrates the pathogenic significance of this type of desmosomal mutation and provides insight into potential clinical manifestations.