Repolarization Injury and Occurrence of Torsades de Pointes During Acute Takotsubo Syndrome.

Background: During takotsubo syndrome (TS), QTc prolongation is common, reflecting repolarization injury and providing the substrate for torsades de pointes (TdP). TdP has been reported sporadically in TS, yet QTc prolongation and TdP risk are often overlooked during management. Objectives: In TS patients, we sought to document TdP incidence, characteristics of patients with TdP, and association of QTc with postdischarge survival. Methods: Among consecutive TS patients at a single institution, we documented admission and discharge QTc, TdP incidence, and postdischarge 1-year mortality from 2006 to 2019. For perspective regarding TdP-TS risk, we characterized all published TdP cases from 2003 to 2022. Results: Of 259 patients, median age was 68 (range: 59-77) years; 92% were female. The QTc interval was prolonged (≥460 ms) on admission in 129 (49.8%) patients and at discharge in 140 (54%) patients. QTc was ≥500 ms either on admission or at discharge in 98 (37.8%) patients. In-hospital TdP incidence was 0.8%. Postdischarge mortality was associated with admission but not discharge, QTc: <460 ms (1.6%); 460-499 ms (12.6%); ≥500 ms (8.8%); P = 0.0056. Among 38 published TdP-TS cases, 80% of TdP events were within 48 hours of hospitalization, 90% of events occurred with QTc ≥500 ms, and 47.5% of events occurred with QTc ≥600 ms. Conditions associated with TdP risk were present in fewer than one-third of patients. Conclusions: During TS, QTc ≥500 ms was frequent. TdP incidence was low, with unpredictable occurrence and observed almost entirely with QTc ≥500 ms. A normal admission QTc was associated with >98% survival at 1-year postdischarge.

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.

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.

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.

High shocking and pacing impedances due to defibrillation lead calcification.

PURPOSE: We have reported the calcification of Endotak defibrillation leads that required replacement. The aim of this study was to assess calcified Endotak Reliance leads in the Food and Drug Administration Manufacturer and User Facility Device Experience (MAUDE) database and compare them to calcified Sprint Fidelis, Sprint Quattro Secure, Riata, and Durata leads in MAUDE. METHODS: We searched the MAUDE database from 2008 to 2019 for defibrillation lead calcification using the terms "calcium," "calcification," and "calcified". Included were explanted leads whose manufacturers found calcium on the shocking and/or pacing electrode. RESULTS: The MAUDE search identified 113 calcified defibrillation leads that qualified for the study, including 109 Endotak Reliance leads, 1 Sprint Quattro Secure lead, 2 Durata leads, 1 Riata ST lead, and no Sprint Fidelis lead. The sign of calcification was a gradual increase in shocking or pacing impedance. Average implant time was 7.4 ± 3.1 (range: 1.3-16.5) years. Only Endotak Reliance leads had shocking coil calcification (n = 72; 66.0%) and five (6.9%) of these failed defibrillation threshold (DFT) testing. Distal pacing electrode calcification affected 55 (50.4%) Endotak Reliance leads. The four other leads had pacing ring electrode calcification only. CONCLUSION: Endotak Reliance defibrillation leads appear prone to shocking coil and/or distal pacing electrode calcification. High impedances may compromise defibrillation and pacing therapy. Patients who have these leads should be monitored; those exhibiting high shocking impedances should be considered for DFT testing. Lead replacement should be considered for pacemaker-dependent patients whose leads exhibit progressively high impedances.

Outcomes Before and After the Recall of a Heart Failure Pacemaker.

Importance: Timely and complete disclosure of medical device defects is necessary to manage patient care safely and effectively. Objectives: To determine if the manufacturer's recommendations following the recall of a medical device were timely and complete, the follow-up information and data provided to patients and physicians were adequate for managing patient care, and the actions taken by the US Food and Drug Administration (FDA) regarding the recall were appropriate. Design, Setting, and Participants: This single-center retrospective case series included 90 of 448 patients who were implanted with a cardiac resynchronization therapy pacemaker at the Minneapolis Heart Institute from May 2003 through January 2011; this pacemaker was recalled in November 2015. In addition, returned product reports submitted by the manufacturer to the FDA via the Manufacturer and User Facility Device Experience (MAUDE) database from January 2008 through December 2018 were analyzed. Main Outcomes and Measures: Clinical outcomes were serious adverse clinical events that occurred before and after the November 2015 recall notifying physicians and patients that the device's battery could fail unexpectedly because of high internal impedance. Technical outcomes were signs and causes of failure. Results: Five of 90 patients observed during 2015 experienced syncope when their pacemakers stopped pacing owing to battery or wire connection defects prior to the recall. Of the 90 patients, 37 (41%) were men, and the median (interquartile range) age at implantation was 71.3 (66.1-78.2) years. Analysis of the MAUDE data revealed that battery failures prior to the recall were associated with serious adverse events that included 1 death, 1 cardiac arrest, 5 syncopal attacks, and 6 heart failure exacerbations; 3 additional prerecall syncopal events were caused by wire connection defects. The manufacturer and the FDA were aware of the battery and wire connection defects for 19 months before issuing the recall, yet the wire connection problem was not included in the advisory and physicians were not informed that interrogating the pacemaker could result in loss of pacing. The FDA classified the recall as class II rather than the more critical class I. Conclusions and Relevance: This case series study of patients implanted with a defective pacemaker found that the pacemaker recall was delayed and that subsequent communications did not include all critical information needed for safe and effective patient care. These findings should prompt reforms in how the medical device industry and the FDA manage future medical device recalls.

Internal insulation breaches in an implantable cardioverter-defibrillator lead with redundant conductors.

BACKGROUND: Internal insulation breaches (IBR) may result in implantable cardioverter-defibrillator lead failure and adverse clinical events. Concerns exist that the Durata lead may be prone to IBR. OBJECTIVE: The goals of this study were to assess Durata failures in the Food and Drug Administration Manufacturer and User Facility Device Experience (MAUDE) database and compare them to failures in MAUDE for Endotak Reliance and Sprint Quattro Secure (QS) leads. METHODS: We searched the MAUDE database from 2008 to 2018 for IBR and other failure modes. Included were explanted leads whose manufacturers found an insulation or conductor defect not caused by extrinsic factors. RESULTS: The MAUDE search found 1011 qualifying leads. The cause of failure differed among leads (P < .001). The primary cause of Durata failure was IBR (293 of 316 leads [93%]), with IBR accounting for 47% (137 of 293); few QS (9 of 523 [1.7%]) and no Endotak Reliance leads failed because of IBR (P < .001). Durata IBR were responsible for 11 failures to treat ventricular tachycardia/ventricular fibrillation, and all were caused by high-voltage (HV) shorts between the proximal superior vena cava coil and a distal right ventricular coil cable (n = 10) or sensing conductor (n = 1); low values of HV impedance were found in these leads during defibrillation threshold testing (n = 3), after a shock or aborted shock (n = 7), and by an alert (n = 1). Inappropriate therapy was caused by 51 Durata IBR, but no QS IBR. CONCLUSION: Durata implantable cardioverter-defibrillator leads are susceptible to IBR that may result in failure to treat ventricular tachycardia/ventricular fibrillation or inappropriate therapy; such failures may occur without forewarning. HV testing of Durata leads may be indicated during pulse generator replacement or when an insulation defect is suspected.

Eligibility and utilization of implantable cardioverter-defibrillators in a regional STEMI system.

BACKGROUND: Studies have shown mortality benefit for implantable cardioverter-defibrillators (ICDs) in ST-elevation myocardial infarction (STEMI) patients with reduced left ventricular ejection fraction (LVEF), but contemporary eligibility and appropriate utilization of ICDs is unknown. OBJECTIVE: The purpose of this study was to determine the contemporary eligibility and appropriate utilization of ICDs post-STEMI. METHODS: Using the prospective Minneapolis Heart Institute regional STEMI registry, LVEF before discharge and at follow-up were stratified into 3 groups: normal (LVEF ≥50%), mildly reduced (LVEF 35%-49%), and severely reduced (LVEF <35%). RESULTS: From March 2003 to June 2012, 3626 patients were treated. Patients with in-hospital death (n = 187), ICD in place (n = 21), negative cardiac biomarkers (n = 337), and undocumented in-hospital LVEF (n = 9) were excluded, leaving 3072 patients in the final analysis, including 1833 (59.7%) with LVEF ≥50%, 875 (28.5%) with LVEF between 35% and 49%, and 364 (11.8%) with LVEF <35% before hospital discharge. Overall, 1029 patients (33.5%) underwent follow-up echocardiography ≥40 days post-STEMI, including 140 of the 364 patients (38.5%) discharged with LVEF <35%. In total, 73 patients (7.1%) with follow-up echocardiography ≥40 days post-STEMI met criteria for an ICD (68 LVEF ≤30%, 5 LVEF 30%-35%, and New York Heart Association class II or greater). Only 26 of these patients (35.6%) underwent ICD placement within 1 year post-STEMI. Overall, only 10% to 15% of potentially eligible patients had an ICD implemented. CONCLUSION: Rates of ICD implantation in appropriate STEMI patients after 40 days are low. Strategies are needed to identify and expand access to these high-risk patients.

Transvenous Implantable Cardioverter-Defibrillator (ICD) Lead Performance: A Meta-Analysis of Observational Studies.

BACKGROUND: Despite the widespread use of implantable cardioverter-defibrillators (ICDs) in clinical practice, concerns exist regarding ICD lead durability. The performance of specific lead designs and factors determining this in large populations need clarification. METHODS AND RESULTS: The Medline, Embase, and Cochrane Collaboration databases were searched for studies including ≥2 of the most commonly implanted leads. The Mantel-Haenszel random-effects model was used. Seventeen studies were selected, including a total of 49 871 patients-5538 implanted with Durata (St. Jude Medical Inc), 10 605 with Endotak Reliance (Boston Scientific), 16 119 with Sprint Quattro (Medtronic Corp), 11 709 with Sprint Fidelis (Medtronic Corp), and 5900 with Riata (St. Jude Medical Inc)-with follow-up of 136 509 lead-years. Although the Durata lead presented a numerically higher rate, no statistically significant differences in the mean incidence of lead failure (0.29%-0.45% per year) were observed in comparison of the 3 nonrecalled leads. A higher event rate was documented with the Riata (1.0% per-year increase) and Sprint Fidelis (>2.0% per-year increase) leads compared with nonrecalled leads. An indication of increased incidence of Durata lead failure versus Sprint Quattro and Endotak Reliance leads was observed in 1 of 3 included studies, allowing for comparison of purely electrical lead failure, but this requires further evaluation. CONCLUSIONS: Endotak Reliance (8F), Sprint Quattro (8F), and Durata (7F) leads displayed low annual incidence of failure; however, long-term follow-up data are still scarce. More data are needed to clarify the performance and safety of the Durata lead.