Association between COVID-19 vaccination and atrial arrhythmias in individuals with cardiac implantable electronic devices.

INTRODUCTION: The impact of mRNA-based coronavirus disease-2019 (COVID-19) vaccines on atrial arrhythmias (AA) and ventricular arrhythmias incidence is unknown. METHODS: BIOTRONIK Home Monitoring data and Medicare Claims data were utilized to identify individuals implanted with a cardiac implantable electronic device (CIED) between 2010 and 2020 who received one or more doses of COVID-19 vaccine in 2021. The burden of AA (%) in the 3 months postvaccination was compared to those noted in the preceding 3 months using the Wilcoxon signed rank test. Sub-analyses comparing the effects of the influenza vaccine against the COVID-19 vaccine were also evaluated for individuals who received the influenza vaccine in 2020. A 1:1 propensity score match comparison between COVID-19 vaccine and non-vaccinated patients was also performed. RESULTS: First and second doses of the COVID-19 vaccine were administered to 7757 and 6579 individuals with a CIED (age 76.2 ± 9.0 years, 49% males), respectively. While a small but statistically significant increase in the burden of AA was noted in the 3 months postvaccination compared to the preceding 3 months after the first dose of the COVID-19 vaccine (0.43 ± 9.04%, p = .028) a similar rise in AA was found following the influenza vaccine and for matched patients who did not receive the COVID-19 vaccine. No significant difference in device therapies was seen pre- and postvaccination. CONCLUSIONS: Though we report a small but significant increase in the number of CIED-detected AAs following vaccination for COVID-19 over a 3-month window, we believe these results correlate more with time and the progressive nature of AF rather than the vaccine itself. While these data should not dissuade from the use of these vaccines, increased vigilance and prompt treatment of AF is required for high-risk groups, specifically males over 70 years of age, following vaccination.

Trends of Cardiovascular Implantable Electronic Device Infection in 3 Decades: A Population-Based Study.

OBJECTIVES: This study assessed trends in the incidence of cardiovascular implantable electronic device (CIED) infection in the last 3 decades using a population-based records linkage study. BACKGROUND: Infection remains an important issue associated with increased implantation rate and dwell time of CIEDs. METHODS: We identified a cohort of all adults with CIEDs who resided in Olmsted County, Minnesota, from 1988 to 2015, using the medical linkage system of the Rochester Epidemiology Project. Standardized criteria were used to identify all CIED infection cases. The cumulative rate of CIED infection was estimated using the Kaplan-Meier method, and the trends of CIED infection incidence were calculated with person-years of follow-up after device implantation. RESULTS: The cumulative probabilities of overall CIED infection were 6.2% (95% confidence interval [CI]: 4.0% to 8.4%) at 15 years and 11.7% (95% CI: 6.8% to 17.3%) at 25 years of follow-up. The incidence of CIED infection every 7 years from 1988 to 2015 was 1.3, 5.7, 4.1, and 4.7 per 1,000-person years, respectively. The 15-year cumulative probabilities of CIED infection after the initial, second, and third procedures were 2.6% (95% CI: 1.4% to 3.8%), 2.7% (95% CI: 1.2% to 4.2%), and 24.1% (95% CI: 3.8% to 44.4%), respectively. Generator changes (hazard ratio [HR]: 3.91; 95% CI: 1.47 to 10.37; p = 0.006) and upgrades (HR: 3.08; 95% CI: 1.24 to 7.62; p = 0.02) were significantly associated with infection. CONCLUSIONS: The incidence of CIED infection had a trend of increasing in the past 2 decades. Contemporary implantable cardioverter-defibrillator and cardiac resynchronization therapies and repeated manipulation of device pockets introduced a greater risk of CIED infection.

Putting down the phone: the obsolescence of transtelephonic monitoring for pacemaker follow-up.

PURPOSE: The evolution of heart rhythm monitoring technology over the past few decades has seen a decline in the use and need of transtelephonic monitoring (TTM). We sought to establish a predicted date for the sun setting of TTM at our institution, as well as establish the current demographics of the patients still using this technology. METHODS: We retrospectively reviewed all patients with permanent pacemakers receiving routine device follow-up at our institution (Mayo Clinic-Rochester) between 2015 and 2018. From this cohort, we reviewed and analyzed patients using TTM for device follow-up and utilized projected battery longevity to determine cessation date. Pacemaker implantation date, underlying arrhythmia, and most recent device interrogation reports were also collected. RESULTS: As of March 2018, a total of 3543 patients with permanent pacemakers were being followed at our institution and 289 (8.2%) are using TTM for monitoring device function (147 male, mean age 79.9 ± 12.0 years). Of those currently using TTM, by January of 2020, only 122 (42.2%) are predicted to be using this technology for device follow-up, 40 (13.8%) by January 2022, with zero patients by November of 2024. CONCLUSIONS: The use of TTM will continue to significantly diminish over the next few years. Based on battery longevity estimates, we predict that by the end of 2024 TTM will no longer be used for device follow-up at our institution.

Incidence and Clinical Significance of New-Onset Device-Detected Atrial Tachyarrhythmia: A Meta-Analysis.

BACKGROUND: Despite the clear association between atrial fibrillation and risk for thromboembolic events (TEs), the clinical significance of new-onset device-detected atrial tachyarrhythmia (DDAT) and TE remains disputed. We aimed to determine the risk of TE in patients with new-onset DDAT. METHODS AND RESULTS: The OVID Medline, Cochrane, and Scopus databases (inception to November 2016) were searched. Randomized controlled trials, prospective, or retrospective studies of pacemaker or defibrillator patients reporting incidence of DDAT were selected. Summary statistics were used for analysis. Of 4893 reports identified, 28 studies following 24 984 patients were included: average age 69.9 years, 34.7% women, mean study duration 21.8±18.6 months. New-onset DDAT was observed in 23% of patients. Among 9 studies (n=8181) reporting TE, the absolute incidence was 2.1%. TE risk was significantly greater among patients with new-onset DDAT (relative risk [RR], 2.88; 95% CI, 1.79-4.64; P<0.001). TE risk was correlated with DDAT duration, with an increased risk associated with DDAT ≥5 minutes (RR, 3.86; 95% CI, 2.04-7.30; P<0.001) compared with <1 minute (RR, 1.77; 95% CI, 1.15-2.74; P=0.01). Notably, the risk of TE was also increased in patients with adjudicated atrial electrograms (RR, 3.60; 95% CI, 2.06-6.30; P<0.001) compared with nonadjudicated electrograms (RR, 2.05; 95% CI, 1.06-3.97; P=0.03), even when lower mean thresholds for detection were used. CONCLUSIONS: New-onset DDAT is common, affecting close to one quarter of all patients with implanted pacemakers or defibrillators. Adjudication of atrial electrograms further identifies at-risk patients, even when relatively short detection thresholds are used.

Oversensing of transthoracic excitation stimuli in contemporary pacemakers.

BACKGROUND: Transthoracic impedance measurements (TIM) is primarily used for minute ventilation rate adaptive sensors in pacemakers. With elevated impedance, the TIM electrical signal itself is oversensed, causing device malfunction. OBJECTIVE: We report an increased incidence of TIM oversensing. METHOD: Retrospective chart review. We review existing records of 18 patients who have demonstrated device malfunction with TIM oversensing. RESULTS: We have found a 1.8% incidence of TIM-related oversensing in our patient population of 959 patients with contemporary Boston Scientific (Marlborough, MA, USA) pacemakers and cardiac resynchronization therapy pacemakers. One patient experienced a syncopal episode. CONCLUSION: Oversensing with pacing inhibition is apparent with the potential of adverse effects to patients.

Mayo Clinic Care Network: A Collaborative Health Care Model.

By leveraging its experience and expertise as a consultative clinical partner, the Mayo Clinic developed an innovative, scalable care model to accomplish several strategic goals: (1) create and sustain high-value relationships that benefit patients and providers, (2) foster relationships with like-minded partners to act as a strategy against the development of narrow health care networks, and (3) increase national and international brand awareness of Mayo Clinic. The result was the Mayo Clinic Care Network.

Implantable Cardioverter Defibrillator Programming Characteristics, Shocked Rhythms, and Survival Among Patients Under Thirty Years of Age.

INTRODUCTION: Indications for implantable cardioverter defibrillators (ICDs) in young patients have expanded and differ from those in older adults. We sought to provide descriptive characteristics and data regarding ICD therapy and outcomes among younger and older ICD recipients. METHODS AND RESULTS: Demographics, device type and programming, remotely transmitted data, shock events, and survival were compared among younger (≤30 years) and older (>30 years) cohorts with ICDs from a single manufacturer followed on a remote network. The younger cohort included 904 patients (1.6% of all implants). This group had more females (46% vs. 25%; P < 0.01), single-coil leads (21% vs. 4%; P < 0.01), and single-chamber devices (46% vs. 34%; P < 0.01). Shock incidence was higher (40% younger vs. 32% older at 4 years; P < 0.01) and survival was better over comparable follow-up (88% vs. 72%; P < 0.01). Remote monitoring was associated with improved survival in both groups (93% vs. 86% ≤ 30 years, P < 0.01; 73% vs. 66% > 30 years, P < 0.01). Shock for polymorphic ventricular tachycardia/fibrillation (VT/VF) was more frequent in younger patients (12% vs. 5%; P < 0.01); 39% of all shocks were inappropriate. A 10-fold increased risk of mortality was seen among young patients with shocks for atrial fibrillation/flutter (AF/AFL). CONCLUSIONS: Differences in survival, shock incidence, and prognostic significance of VT/VF and AF/AFL exist between younger and older ICD recipients. These suggest distinct differences in myocardial substrates and diseases that ultimately impact ICD management.

Atrioventricular and ventricular-to-ventricular programming in patients with cardiac resynchronization therapy: results from ALTITUDE.

PURPOSE: Cardiac resynchronization therapy (CRT) improves outcomes in patients with heart failure, yet response rates are variable. We sought to determine whether physician-specified CRT programming was associated with improved outcomes. METHODS: Using data from the ALTITUDE remote follow-up cohort, we examined sensed atrioventricular (AV) and ventricular-to-ventricular (VV) programming and their associated outcomes in patients with de novo CRT from 2009-2010. Outcomes included arrhythmia burden, left ventricular (LV) pacing, and all-cause mortality at 4 years. RESULTS: We identified 5709 patients with de novo CRT devices; at the time of implant, 34% (n = 1959) had entirely nominal settings programmed, 40% (n = 2294) had only AV timing adjusted, 11% (n = 604) had only VV timing adjusted, and 15% (n = 852) had both AV and VV adjusted from nominal programming. Suboptimal LV pacing (<95%) during follow-up was similar across groups; however, the proportion with atrial fibrillation (AF) burden >5% was lowest in the AV-only adjusted group (17.9%) and highest in the nominal (27.7%) and VV-only adjusted (28.3%) groups. Adjusted all-cause mortality was significantly higher among patients with non-nominal AV delay >120 vs. <120 ms (adjusted heart rate (HR) 1.28, p = 0.008) but similar when using the 180-ms cutoff (adjusted HR 1.13 for >180 vs. ≤180 ms, p = 0.4). CONCLUSIONS: Nominal settings for de novo CRT implants are frequently altered, most commonly the AV delay. There is wide variability in reprogramming. Patients with nominal or AV-only adjustments appear to have favorable pacing and arrhythmia outcomes. Sensed AV delays less than 120 ms are associated with improved survival.

Patient Activity and Survival Following Implantable Cardioverter-Defibrillator Implantation: The ALTITUDE Activity Study.

BACKGROUND: Physical activity data are collected automatically by implantable cardioverter-defibrillators (ICDs). Though these data potentially provide a quantifiable and easily accessible measure of functional status, its relationship with survival has not been well studied. METHODS AND RESULTS: Patients enrolled in the Boston Scientific LATITUDE remote monitoring system from 2008 to 2012 with ICDs were eligible. Remote monitoring data were used to calculate mean daily activity at baseline (30 to 60 days after implantation), and longitudinally. Cox regression was used to examine the association between survival and increments of 30 minutes/day in both (1) mean baseline activity and (2) time-varying activity, with both adjusted for demographic and device characteristics. A total of 98 437 patients were followed for a median of 2.2 years (mean age of 67.7±13.1 years; 71.7% male). Mean baseline daily activity was 107.5±66.2 minutes/day. The proportion of patients surviving after 4 years was significantly higher among those in the most versus least active quintile of mean baseline activity (90.5% vs. 50.0%; log-rank P value, <0.001). Lower mean baseline activity (i.e., incremental difference of 30-minutes/day) was independently associated with a higher risk of death (adjusted hazard ratio [AHR], 1.44; 95% confidence interval [CI], 1.427 to 1.462). Time-varying activity was similarly associated with a higher risk of death (AHR, 1.48; 95% CI, 1.451 to 1.508), indicating that a patient having 30 minutes per day less activity in a given month has a 48% increased hazard for death when compared to a similar patient in the same month. CONCLUSIONS: Patient activity measured by ICDs strongly correlates with survival following ICD implantation.

Usefulness of sonication of cardiovascular implantable electronic devices to enhance microbial detection.

The cardiovascular implantable electronic device (CIED) infection rate is rising disproportionately to the rate of device implantation. Identification of microorganisms that cause CIED infections is not always achieved using present laboratory techniques. We conducted a prospective study to determine whether device vortexing-sonication followed by culture of the resulting sonicate fluid would enhance microbial detection compared with traditional swab or pocket tissue cultures. Forty-two subjects with noninfected and 35 with infected CIEDs were prospectively enrolled over 12 months. One swab each from the device pocket and device surface, pocket tissue, and the CIED were collected from each patient. Swabs and tissues were cultured using routine methods. The CIED was processed in Ringer's solution using vortexing-sonication and the resultant fluid semiquantitatively cultured. Tissue and swab growth was considered significant when colonies grew on ≥2 quadrants of the culture plate and device was considered significant when ≥20 colonies were isolated from 10 ml of sonicate fluid. In noninfected group, 5% of sonicate fluids yielded significant bacterial growth, compared with 5% of tissue cultures (p = 1.00) and 2% of both pocket and device swab cultures (p = 0.317 each). In infected group, significant bacterial growth was observed in 54% of sonicate fluids, significantly greater than the sensitivities of pocket swab (20%, p = 0.001), device swab (9%, p <0.001), or tissue (9%, p <0.001) culture. In conclusion, vortexing-sonication of CIEDs with semiquantitative culture of the resultant sonicate fluid results in a significant increase in the sensitivity of culture results, compared with swab or tissue cultures.

Correlation of geomagnetic activity with implantable cardioverter defibrillator shocks and antitachycardia pacing.

OBJECTIVE: To investigate a potential relationship between implantable cardioverter defibrillator (ICD) therapies and daily geomagnetic activity (GMA) recorded in a large database. PATIENTS AND METHODS: The ALTITUDE database, derived from the Boston Scientific LATITUDE remote monitoring system, was retrospectively analyzed for the frequency of ICD therapies. Daily GMA was expressed as the planetary K-index and the integrated A-index and was graded as levels I (quiet), II (unsettled), III (active), and IV (storm). RESULTS: A daily mean ± SD of 59,468±11,397 patients were monitored between January 1, 2009, and May 15, 2012. The distribution of days according to GMA was as follows: level I, 924/1231 (75%); level II, 226/1231 (18%); level III, 60/1231 (5%); and level IV, 21/1231 (2%). The daily mean ± SD numbers of ICD shocks received per 1000 active patients in the database were 1.29±0.47, 1.17±0.46, 1.03±0.37, and 0.94±0.29 on level I, II, III, and IV days, respectively; the daily mean ± SD sums of shocks and antitachycardia pacing therapies were 9.29±2.86, 8.46±2.45, 7.92±1.80, and 7.83±2.28 on quiet, unsettled, active, and storm days, respectively. A significant inverse relationship between GMA and frequency of ICD therapies was identified, with the most pronounced difference between level I and level IV days (P<.001 for shocks; P=.008 for shocks + antitachycardia pacing). CONCLUSION: In a large-scale cohort analysis, ICD therapies were delivered less frequently on days of higher GMA, confirming the previous pilot data and suggesting that higher GMA does not pose an increased risk of arrhythmias using ICD therapies as a surrogate marker. Further studies are needed to gain an in-depth understanding of the underlying mechanisms.

Femoral approach to lead extraction.

Laser and radiofrequency energy-assisted lead extraction has greatly facilitated this complex procedure. Although success rates are high, in some instances alternate methods of extraction are required. In this review, we discuss techniques for femoral extraction of implanted leads and retained fragments. The major tools available, including commonly used snares and delivery tools, are discussed. We briefly describe combined internal jugular and femoral venous extraction approaches, as well as complimentary utilization of more than one technique via the femoral vein. Animated and procedural sequences are included to help the reader visualize the key components of these techniques.

Predicting risk of endovascular device infection in patients with Staphylococcus aureus bacteremia (PREDICT-SAB).

BACKGROUND: Prompt recognition of underlying cardiovascular implantable electronic device (CIED) infection in patients presenting with Staphylococcus aureus bacteremia (SAB) is critical for optimal management of these cases. The goal of this study was to identify clinical predictors of CIED infection in patients presenting with SAB and no signs of pocket infection. METHODS AND RESULTS: All cases of SAB in CIED recipients at Mayo Clinic from 2001 to 2011 were retrospectively reviewed. We identified 131 patients with CIED who presented with SAB and had no clinical signs of device pocket infection. Forty-five (34%) of these patients had underlying CIED infection based on clinical or echocardiographic criteria. The presence of a permanent pacemaker rather than an implantable cardioverter-defibrillator (odds ratio, 3.90; 95% confidence interval, 1.65-9.23; P=0.002), >1 device-related procedure (odds ratio, 3.30; 95% confidence interval, 1.23-8.86; P=0.018), and duration of SAB ≥4 days (odds ratio, 5.54; 95% confidence interval, 3.32-13.23; P<0.001) were independently associated with an increased risk of CIED infection in a multivariable model. The area under the receiver operating characteristics curve for the multivariable model was 0.79, indicating a good discriminatory capacity to distinguish SAB patients with and without CIED infection. CONCLUSIONS: Among patients presenting with SAB and no signs of pocket infection, the risk of underlying CIED infection can be calculated based on the type of device, number of device-related procedures, and duration of SAB. We propose that patients without any of these high-risk features have a low risk of underlying CIED infection and may be monitored closely without immediate device extraction. Prospective studies are needed to validate this risk prediction model.

Clinical presentation and outcomes of cardiovascular implantable electronic device infections in hemodialysis patients.

BACKGROUND: Infection is a serious complication of cardiovascular implantable electronic device (CIED) implantation. Kidney failure is as an independent risk factor for CIED infection and associated mortality. The presence of multiple comorbid conditions may contribute to varied clinical presentations and poor outcomes in hemodialysis (HD)-dependent patients with cardiac device infection. STUDY DESIGN: Case series. SETTING & PARTICIPANTS: CIED infections in HD patients (n=17) and non-HD patients (n=398) at Mayo Clinic in Rochester, MN, between 1991 and 2008. OUTCOMES: Surgical management and death. MEASUREMENTS: Clinical presentations, microbial organisms. RESULTS: Of 415 patients admitted with CIED infection, 17 (4%) were receiving maintenance HD therapy. Among those on HD therapy, mean age was 72±15 (SD) years, 59% were women, and 53% had a central venous catheter for dialysis access. All 17 patients receiving HD therapy presented with CIED-associated bloodstream infection and 41% of these had infected vegetations on CIED leads or cardiac valves. A majority (82%) were managed with complete device removal and almost half (43%) received a replacement device when bloodstream infection cleared. Device infection was associated with significant short-term mortality in HD patients and 90-day survival was only 76% in this group of patients. LIMITATIONS: Smaller sample size, majority white cohort, observational study. CONCLUSIONS: CIED infection in patients receiving HD usually is associated with bloodstream infection and frequently is complicated with device-related endocarditis. Despite complete device removal in the majority of HD patients with infection, mortality remains high.

Features and outcomes of patients who underwent cardiac device deactivation.

IMPORTANCE: Little is known about patients who undergo cardiovascular implantable electronic device deactivation. OBJECTIVE: To describe features and outcomes of patients who underwent cardiovascular implantable electronic device deactivation. DESIGN, SETTING, AND PARTICIPANTS: Retrospective review of medical records of 150 patients at a tertiary academic medical center (Mayo Clinic, Rochester, Minnesota). EXPOSURE Cardiovascular implantable electronic device deactivation. MAIN OUTCOMES AND MEASURES: Demographic and clinical data and information regarding advance directives, ethics consultations, palliative medicine consultations, and cardiovascular implantable electronic device deactivations. RESULTS: Of the 150 patients (median age, 79 years; 67% were male), 149 (99%) had poor or terminal prognoses. Overall, 118 patients (79%) underwent deactivation of tachycardia therapies only, and 32 (21%) underwent deactivation of bradycardia therapies with or without tachycardia therapies (6 patients [4%] were pacemaker-dependent). Half of the deactivation requests (51%) were made by surrogates. A majority of deactivations (55%) were carried out by nurses. Although 85 patients (57%) had advance directives, only 1 mentioned the device in the directive. Ethics consultations occurred in 3 patients (2%) and palliative medicine consultations in 64 (43%). The proportions of patients who died within 1 month of device deactivation were similar for those who underwent deactivation of tachycardia therapies only and those who underwent deactivation of bradycardia therapies with or without tachycardia therapies (85% vs 94%; P = .37). CONCLUSIONS AND RELEVANCE: Most requests for cardiovascular implantable electronic device deactivation were for implantable cardioverter-defibrillator-delivered tachycardia therapies only. Many of these requests were made by surrogates. Advance directives executed by patients with these devices rarely addressed device management. Regardless of device therapy, most patients died shortly after device deactivation. Hence, a device deactivation decision may reflect the seriousness of a given patient's underlying illness. Patients with devices should engage in advance care planning to ensure that future care is consistent with their preferences.

Meta-analysis of symptomatic response attributable to the pacing component of cardiac resynchronization therapy.

AIMS: Prognostic benefit from CRT compared with controls is well established. Symptomatic response rates, however, are controversial and have never been systematically evaluated with standard subtraction of control rates to establish the incremental symptomatic response effect of CRT pacing. METHODS AND RESULTS: First, we identified 150 consecutive CRT papers and assessed researchers' perceptions of the symptomatic response to CRT. The mean quoted response rate was 66%. Only 26 studies acknowledged the existence of response without the device. Secondly, we examined actual symptomatic response rates in the randomized trials (CARE-HF, COMPANION, CONTAK-CD, MIRACLE, MIRACLE-ICD, MIRACLE-ICD II, MUSTIC, and REVERSE) totalling 3904 patients. The NYHA status improved in 51% of those randomized to CRT vs. 35% of controls (incremental effect 16%). This incremental improvement was significantly greater in open studies (with no device for controls) than in blinded studies (control arm receiving a device but no CRT, such as a defibrillator or a CRT programmed off), 20% vs. 13%, P < 0.001. CONCLUSIONS: Quoting CRT responder rates in isolation without recognizing spontaneous 'response' is common but unwise. The incremental symptomatic response rate from CRT pacing is ∼16%, much lower than widely reported. This value is similar to that for drugs in heart failure and should not be considered disappointing: they both exert powerful prognostic benefits. For scientific purposes, e.g. to explore potential improvements, symptomatic benefit from CRT should be quantified, like all other effects, by comparison with a control.

Survival after shock therapy in implantable cardioverter-defibrillator and cardiac resynchronization therapy-defibrillator recipients according to rhythm shocked. The ALTITUDE survival by rhythm study.

OBJECTIVES: This study sought to determine if the risk of mortality associated with inappropriate implantable cardioverter-defibrillator (ICD) shocks is due to the underlying arrhythmia or the shock itself. BACKGROUND: Shocks delivered from ICDs are associated with an increased risk of mortality. It is unknown if all patients who experience inappropriate ICD shocks have an increased risk of death. METHODS: We evaluated survival outcomes in patients with an ICD and a cardiac resynchronization therapy defibrillator enrolled in the LATITUDE remote monitoring system (Boston Scientific Corp., Natick, Massachusetts) through January 1, 2010. First shock episode rhythms from 3,809 patients who acutely survived the initial shock were adjudicated by 7 electrophysiologists. Patients with a shock were matched to patients without a shock (n = 3,630) by age at implant, implant year, sex, and device type. RESULTS: The mean age of the study group was 64 ± 13 years, and 78% were male. Compared with no shock, there was an increased rate of mortality in those who received their first shock for monomorphic ventricular tachycardia (hazard ratio [HR]: 1.65, p < 0.0001), ventricular fibrillation/polymorphic ventricular tachycardia (HR: 2.10, p < 0.0001), and atrial fibrillation/flutter (HR: 1.61, p = 0.003). In contrast, mortality after first shocks due to sinus tachycardia and supraventricular tachycardia (HR: 0.97, p = 0.86) and noise/artifact/oversensing (HR: 0.91, p = 0.76) was comparable to that in patients without a shock. CONCLUSIONS: Compared with no shock, those who received their first shock for ventricular rhythms and atrial fibrillation had an increased risk of death. There was no significant difference in survival after inappropriate shocks for sinus tachycardia or noise/artifact/oversensing. In this study, the adverse prognosis after first shock appears to be more related to the underlying arrhythmia than to an adverse effect from the shock itself.