Subcutaneous Implantable Cardioverter-defibrillator Shock Research Articles

AP-518-02 ATRIAL PACING INDUCED OVERSENSING IN SUBCUTANEOUS IMPLANTABLE CARDIOVERTER DEFIBRILLATOR

A 23 year old male with hypertrophic cardiomyopathy, was implanted with a Subcutaneous Implantable Cardioverter Defibrillator (S-ICD) (Cameron Health SQ-RX 1010). Four years later the patient developed symptomatic bifascicular block and a dual chamber pacemaker (PPM) (Biotronik Epyra-6) was implanted. To highlight the potential challenge of interactions between an S-ICD and atrial pacing. N/A The PPM was programmed DDD with a lower rate of 60 bpm and an upper rate of 150 bpm. The S-ICD conditional and shock zones were set to 250 bpm, in the Secondary vector. Primary and Alternate vectors were not viable options due to oversensing of the patient's intrinsic rhythm and smart pass filtering unavailable on this device model. Two months post PPM insertion, an untreated episode was detected by the S-ICD displaying intermittent triple counting of the P, R and T-wave (figure 1). Consequently simultaneous interrogation of the PPM and S-ICD was performed. Upon conducting the atrial threshold test in AAI mode, the S-ICD P-wave oversensing was replicated (figure 2). The paced P-wave amplitude was similar to that of the intrinsic R-wave (figure 1 circled in red) resulting in sensing of both components. S-ICD sensing utilises auto gain control whereby the average amplitude of the last two sensed signals is taken and the decay to sensing floor begins at 75% of this calculated amplitude. As the interval between sensed beats decreases, the shorter the refractory period and more aggressive the decay to ensure appropriate sensing of small amplitude signals, typically seen during ventricular fibrillation. A fortuitous ventricular ectopic (figure 1 highlighted in green) resets the sensing profile as the amplitude is significantly greater and momentarily avoids further oversensing and inappropriate therapy. Following this episode, the PPM was reprogrammed with a reduced lower rate limit of 40 bpm and atrial auto-capture turned off allowing intrinsic P-wave sensing. No further untreated episodes due to oversensing were seen for the remainder of the S-ICD battery longevity of approximately 2 years. It is important to screen all possible paced morphologies from both the atrial and ventricular chambers to prevent S-ICD oversensing when concurrent devices are in situ.View Large Image Figure ViewerDownload Hi-res image Download (PPT)

Predictors of Subcutaneous Implantable Cardioverter-Defibrillator Shocks and Prognostic Impact in Patients With Structural Heart Disease

BackgroundIn this study we aimed to assess long-term outcomes in subcutaneous implantable cardioverter-defibrillator (S-ICD) recipients with structural heart disease by focussing especially on shock incidence, predictors, and associated prognoses. MethodsIn this multicenter registry‒based study, we retrospectively included all patients who underwent S-ICD implantation at 3 tertiary centers. The prognostic impact of S-ICD shock was assessed with a composite outcome that included all-cause death and hospitalisation for heart failure. ResultsA total of 351 patients with underlying cardiomyopathy were included in the investigation. Using multivariable Fine and Gray regression models, secondary prevention, left ventricular ejection fraction (LVEF), conditional shock threshold, and QRS duration appeared to be independent predictors of appropriate S-ICD shock occurrence. In the multivariate Cox regression model adjusted for age, baseline LVEF, underlying cardiomyopathy subtype, New York Heart Association class, and appropriate shocks were significantly associated with increased composite prognostic outcome risk (hazard ratio [HR], 2.61; 95% confidence interval [CI], 1.21-5.65; P = 0.014), whereas inappropriate shocks were not (HR, 1.35; 95% CI, 0.75-4.48; P = 0.18). The analysis of each component of the composite prognostic outcome highlighted that the occurrence of appropriate shocks was associated with an increased risk of hospitalisation for heart failure (HR, 3.10; 95% CI, 1.26-7.58; P = 0.013) and a trend for mortality (HR, 2.19; 95% CI, 0.78-6.16; P = 0.14). ConclusionsAppropriate S-ICD shocks were associated with a 3-fold increase in acute heart failure admission, whereas inappropriate shocks were not. Conditional shock threshold programming is an independent predictor of S-ICD shock, and its prognostic impact should be investigated further in patients with structural heart disease.

Refractoriness to subcutaneous implantable cardioverter defibrillator after frequent therapies for ventricular fibrillation storms in a Brugada syndrome case

BackgroundThe subcutaneous implantable cardioverter defibrillator (S-ICD) is an alternative to the transvenous implantable cardioverter defibrillator for the prevention of sudden cardiac death. Here, we report a rare case of refractoriness to an S-ICD after frequent therapies for ventricular fibrillation (VF) storms.Case presentationA 24-year-old man underwent a bout of syncope with vomiting and incontinence at home. He was brought to the emergency room and was witnessed to spontaneously go into VF successfully converted by external defibrillation. Previously, he was diagnosed with a type I Brugada electrocardiogram pattern by a pilsicainide administration test in another hospital. Although he had a family history of sudden cardiac death in 3 relatives, including his brother, he was followed closely without any therapies because he had never had an episode of syncope. He was implanted with an S-ICD without any trouble. Seven months later, frequent S-ICD shocks for VF storms occurred. His VF was controlled by using intravenous amiodarone, which was converted to an oral preparation. However, his VF recurred after another 2 months. The analysis of his S-ICD data revealed that 4 consecutive shock deliveries could not terminate his VF and the final shock delivered could fortunately terminate it because of a high defibrillation threshold test (DFT) due to an increasing shock impedance (64 to 90 Ω). First, we performed an epicardial Brugada syndrome ablation and subsequently replaced and repositioned the S-ICD lead from a left to a right parasternal site. After the re-implantation of the S-ICD, the DFT test improved to within normal range. According to the pathological analysis, infiltration of inflammatory cells and extensive fibrosis were confirmed in the subcutaneous tissue around the shock lead and S-ICD body.ConclusionFrequent S-ICD shocks for VF storms might cause various pathological changes around the device and lead to a high DFT.

Incidence, mechanisms, and clinical impact of inappropriate shocks in patients with a subcutaneous defibrillator.

Inappropriate shocks (IAS) remain a challenge for patients and physicians after implantation of the subcutaneous implantable cardioverter-defibrillator (S-ICD). The aims were to assess and characterize different patterns of IAS. Two hundred and thirty-nine patients were implanted with an S-ICD between 2010 and 2018 for primary and secondary prevention. Follow-up data of at least 6 months were analysed. During a mean follow-up of 34.9 ± 16.0 months, a total of 73 shocks occurred in 38 patients (6%). Forty-three (59%) shocks were considered appropriate due to ventricular tachycardia/ventricular fibrillation, while 30 (41%) were inappropriate and occurred in 19 patients (8%). Myopotentials/noise was the most frequent cause of inappropriate shocks (n = 8), followed by T-wave oversensing (n = 6) and undersensing of the QRS, resulting in adaptation of the automatic gain control and inappropriate shock (n = 5). Seventy-four percent of all IAS occurred on the primary vector, while no IAS occurred on the alternate vector. In seven of eight patients (88%), IAS related to myopotentials have occurred on the primary sensing vector. Multivariate analysis identified taller patients, primary sensing vector and first-generation S-ICD device as predictors for IAS. SMART pass effectively reduced the occurrence of IAS in the second-generation S-ICD system. Inappropriate therapies are less frequently observed on the alternate vector. The primary vector seems to be unfavourable with regard to oversensing caused by myopotentials. Inappropriate shocks were associated with an increased rate of rehospitalization but not mortality. These observations have implications for the prevention of inappropriate S-ICD shocks.

CPR Induced Inappropriate Shocks from a Subcutaneous Implantable Cardioverter Defibrillator during Out-of-Hospital Cardiac Arrest

We present the case of a 30-year-old man with a subcutaneous implantable cardioverter defibrillator (S-ICD) who suffered sudden out-of-hospital cardiac arrest. During resuscitation, the patient received inappropriate shocks due to oversensing by the S-ICD of chest compression induced artifact. The rhythm on the EMS monitor showed asystole throughout the period of resuscitation. Placement of a magnet over the S-ICD generator failed to inhibit the delivery of S-ICD shocks. Information regarding inappropriate S-ICD shocks may be useful during resuscitation of patients with sudden cardiac arrest.

Factors Associated With High-Voltage Impedance and Subcutaneous Implantable Defibrillator Ventricular Fibrillation Conversion Success.

The ability to predict defibrillation efficacy at the time of subcutaneous implantable cardioverter-defibrillator implantation without the need to induce ventricular fibrillation might eliminate the need for defibrillation testing. The purpose of this study was to determine the association of high-voltage impedance and system implant position on ventricular fibrillation conversion success with a submaximal 65-J shock. In the subcutaneous implantable cardioverter-defibrillator IDE study (Investigational Device Exemption), a successful conversion test required 2 consecutive ventricular fibrillation conversions at 65 J in either shock vector. Chest radiographs were obtained after implantation. Patients with imaging and impedance data were included. Suboptimal device position was defined as an inferior electrode or pulse generator or electrode coil depth >3 mm anterior to the sternum. Absence of suboptimal positional parameters was defined as appropriate position. Conversion success rate was calculated among all 65-J tests. Of 314 patients who underwent subcutaneous implantable cardioverter-defibrillator implantation, 282 patients were included in this analysis. There were 637 inductions to test defibrillation at 65 J. Sixty-two conversion failures (9.7%) occurred in 42 (14.9%) patients. Lower body mass index and lower shock impedance were associated with higher conversion success rate, whereas white race was associated with lower conversion success rate. Suboptimal position was more common in obese patients. Inferior electrode and greater distance between the lead and sternum were associated with a higher impedance. When appropriate system position was achieved, conversion failure was not associated with high body mass index. Subcutaneous implantable cardioverter-defibrillator shock efficacy is associated with system position and high-voltage system impedance. A high impedance is associated with inferiorly placed pulse generator and electrode system, inadequate coil depth, and a lower rate of defibrillator success. URL: https://www.clinicaltrials.gov . Unique identifier: NCT01064076.

Effects of defibrillation shock in patients implanted with a subcutaneous defibrillator: a biomarker study.

AimsImplantable cardioverter defibrillator (ICD) shocks are associated with a subsequent increased risk of death, and an elevation of cardiac enzymes has been measured after defibrillation testing (DFT). In an experimental swine study, subcutaneous ICD (S-ICD) shocks caused less myocardial damage than traditional ICD shocks. The aim of our study was to investigate the association between S-ICD shock and acute cardiac damage in humans, as evaluated by means of sensitive and highly specific circulating biomarkers.Methods and resultsWe calculated the variation in the serum levels of high-sensitivity cardiac troponin I (hs-CTnI) and creatine kinase-MB mass concentration (CK-MB mass), measured before and after an S-ICD shock delivered during intraoperative DFT. We also measured the degree of haemodynamic stress, as the variation in the serum levels of N-terminal pro-B-type natriuretic peptide (NT-proBNP) and copeptin (CP), after the S-ICD shock. We analysed 30 consecutive patients who received an S-ICD and who underwent DFT by means of a single 65 J shock. The levels of biomarkers did not change from baseline to 1 h post-shock, i.e. hs-CTnI (from 0.029 ± 0.005 ng/mL to 0.030 ± 0.005 ng/mL, P = 0.079) and CK-MB mass (from 1.37 ± 0.17 ng/mL to 1.41 ± 0.18, P = 0.080) and remained stable 6 and 24 h after DFT. The plasma NT-proBNP did not change, whereas CP levels were significantly higher at 1 h post-shock evaluation. However, 6 h after DFT, the levels had returned to the baseline and remained stable at 24 h.ConclusionThe S-ICD shock did not seem to cause myocardial injuries. Although CP levels temporarily rose after DFT, they returned to basal levels within 6 h, which suggests that DFT does not have long-term prognostic implications. ICD shocks are associated with a subsequent increased risk of death, and an elevation of cardiac enzymes has been measured after DFT. We showed that serum levels of biomarkers of myocardial damage did not increase after high-energy DFT in patients who had undergone S-ICD device implantation. This suggests that S-ICD shock does not have long-term prognostic implications.

Sensitivity and specificity of the subcutaneous implantable cardioverter defibrillator pre-implant screening tool

BackgroundThe sensitivity and specificity of the subcutaneous implantable cardioverter defibrillator (S-ICD) pre-implant screening tool required clinical evaluation. MethodsBipolar vectors were derived from electrodes positioned at locations similar to those employed for S-ICD sensing and pre-implant screening electrodes, and recordings collected through 80-electrode PRIME®-ECGs, in six different postures, from 40 subjects (10 healthy controls, and 30 patients with complex congenital heart disease (CCHD); 10 with Tetralogy of Fallot (TOF), 10 with single ventricle physiology (SVP), and 10 with transposition of great arteries (TGA)). The resulting vectors were analysed using the S-ICD pre-implant screening tool (Boston Scientific) and processed through the sensing algorithm of S-ICD (Boston Scientific). The data were then evaluated using 2×2 contingency tables. Fisher exact and McNemar tests were used for a comparison of the different categories of CCHD, and p<0.05 vs. controls considered to be statistically significant. Results57% of patients were male, mean age of 36.3years. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of the S-ICD screening tool were 95%, 79%, 59% and 98%, respectively, for controls, and 84%, 79%, 76% and 86%, respectively, in patients with CCHD (p=0.0001). ConclusionThe S-ICD screening tool was comparatively more sensitive in normal controls but less specific in both CCHD patients and controls; a possible explanation for the reported high incidence of inappropriate S-ICD shocks. Thus, we propose a pre-implant screening device using the S-ICD sensing algorithm to minimise false exclusion and selection, and hence minimise potentially inappropriate shocks.

Inappropriate subcutaneous implantable cardioverter-defibrillator shocks due to T-wave oversensing can be prevented: Implications for management

Inappropriate shocks (IASs) complicate implantable cardioverter-defibrillator (ICD) therapy. The management of IASs in patients with a subcutaneous ICD (S-ICD) differs from that in patients with a conventional ICD because of different sensing algorithms and programming options. To describe the management of IASs in patients with an S-ICD. Patients were implanted with an S-ICD between February 2009 and July 2012. The prevalence data and clinical determinants of IASs were prospectively collected. In the case of T-wave oversensing (TWOS), an exercise test was performed, and all possible sensing vectors were screened for TWOS. The absence of TWOS defined a suitable vector. Eleven of 69 patients (54% men; mean age 39 ± 14 years; 73% primary prevention) received IASs after 8.9 ± 10 months of implantation (10.8% annual incidence rate). In 8 cases, TWOS caused IASs. Seven of these IASs occurred during exercise and 1 during atrial fibrillation with a high ventricular rate. To manage TWOS, in 7 of 8 patients the sensing vector was changed and in 5 of 8 patients the (un)conditional zone was changed. Hereafter, IASs recurred in 3 of 8 patients, in 2 because of programming errors. Hence, after reprogramming, we observed no IASs in 87.5% of the patients with TWOS during a follow-up of 14.1 ± 13 months. IASs due to TWOS in the S-ICD can be managed by reprogramming the sensing vector and/or the therapy zones of the device using a template acquired during exercise. Exercise-optimized programming can reduce future IASs, and standard exercise testing shortly after the implantation of an S-ICD may be considered in patients at an increased risk for TWOS.

Evaluation of Acute Cardiac and Chest Wall Damage after Shocks with a Subcutaneous Implantable Cardioverter Defibrillator in Swine

A subcutaneous implantable cardioverter defibrillator (S-ICD) could ease placement and reduce complications of transvenous ICDs, but requires more energy than transvenous ICDs. Therefore we assessed cardiac and chest wall damage caused by the maximum energy shocks delivered by both types of clinical devices. During sinus rhythm, anesthetized pigs (38 ± 6 kg) received an S-ICD (n = 4) and five 80-Joule (J) shocks, or a transvenous ICD (control, n = 4) and five 35-J shocks. An inactive S-ICD electrode was implanted into the same control pigs to study implant trauma. All animals survived 24hours. Troponin I and creatine kinase muscle isoenzyme (CK-MM) were measured as indicators of myocardial and skeletal muscle injury. Histopathological injury of heart, lungs, and chest wall was assessed using semiquantitative scoring. Troponin I was significantly elevated at 4hours and 24hours (22.6± 16.3 ng/mL and 3.1± 1.3 ng/mL; baseline 0.07± 0.09 ng/mL) in control pigs but not in S-ICD pigs (0.12± 0.11 ng/mL and 0.13± 0.13 ng/mL; baseline 0.06± 0.03 ng/mL). CK-MM was significantly elevated in S-ICD pigs after shocks (6,544± 1,496 U/L and 9,705± 6,240 U/L; baseline 704± 398 U/L) but not in controls. Electrocardiogram changes occurred postshock in controls but not in S-ICD pigs. The myocardium and lungs were histologically normal in both groups. Subcutaneous injury was greater in S-ICD compared to controls. Although CK-MM suggested more skeletal muscle injury in S-ICD pigs, significant cardiac, lung, and chest wall histopathological changes were not detected in either group. Troponin I data indicate significantly less cardiac injury from 80-J S-ICD shocks than 35-J transvenous shocks.