Recurrent Shocks Research Articles

5203Ablation of scar-related ventricular tachycardia: paced electrogram feature analysis (PEFA) is a novel and effective substrate based strategy

Abstract Background Ablation of scar related ventricular tachycardia (VT) has been shown to be superior to escalation of drug therapy. However, the incremental benefit remains modest, with 42% experiencing recurrent shocks and 64% appropriate anti-tachycardia pacing (ATP) in the VANISH study. Improved ablation strategies are needed. Paced electrogram feature analysis (PEFA) is a novel substrate based ablation technique. Purpose To investigate the effectiveness of the PEFA based VT ablation technique. Methods A single centre, prospective study. Consecutive cases of scar related VT that had an implantable cardiac defibrillator (ICD) and no prior ablations were recruited. Close coupled pacing was performed at the right ventricular apex and the VT isthmus(es) identified on high density mapping catheters by increased electrogram (EGM) duration and latency. A algorithm was developed to identify the latest EGM component after the S2 pacing artefact,. This millisecond value was displayed on the geometry as a colour (PEFA map) (St Jude Ensite Precision Electroanatomic Mapping). PEFA identified VT isthmus sites were targeted for ablation (Figure 1). Follow up ICD interrogation data was utilized to assess for VT recurrence. Results A total of 20 patients were recruited. These comprised ischaemic cardiomyopathy (CM) (17/20), dilated CM (2/20), and arrhythmogenic CM (1/20), male (18/20), and endocardial only approach (19/20). Mean age was 64.3±11.3 years, ejection fraction 24.4% ± 14.4, and ablation time was 1989.9±1078.1 seconds. Non-inducibility was demonstrated at the end of the case in 18/20. A class I or III anti-arrhythmic drug was continued in 50%. VT recurred in three cases (Day 28,30,55). One death occurred following a stroke on day 181. Mean follow up was 437.5±231.7 days. Figure 1 Conclusion This is the largest study to date on PEFA based VT ablation, the first to include non-ischaemic aetiologies, and reports a longer mean follow up. A high proportion of cases were non-inducible, and low VT recurrence rates were observed. PEFA appears to be a promising tool to guide VT ablation targets. Acknowledgement/Funding This research was funded in part by the Canadian Institute for Health Research (139080) and a grant from St. Jude Medical.

Rare but lethal short QT syndrome: most recent understanding of the disease

Short QT syndrome (SQTS) is a rare genetic channelopathy that affects the repolarization of cardiac cells and is associated with cardiac arrhythmia and sudden cardiac death (SCD). “Abbreviated repolarization” is the hallmark of the disease, which is secondary to genetic defects; mutations in several genes that encode different cardiac ion channels have been identified in individuals with the disease. Presentations of the disease include syncope, atrial or ventricular arrhythmia and SCD. SQTS is diagnosed with a corrected-QT (QTc) interval of <340 milliseconds (ms) or a QTc of 340-360 ms and either personal or family history of SCD, family history of SQTS or an identified genetic mutation. Implantable cardioverter-defibrillator (ICD) is the main treatment used in the secondary prevention of SCD in patients with the disease who have experienced previous major arrhythmic events. Pharmacological treatment with quinidine is used as an adjuvant therapy to ICD in the setting of recurrent shocks or as an alternative treatment when ICD is not feasible. The goal of this review article is to describe this rare and under-studied condition, highlight steps to diagnosis and describe treatment modalities, particularly in South America where there is a lack of studies and understanding of this disease.

Abstract 816: Surgical Bilateral Stellate Ganglionectomy Reduces Mitochondrial Reactive Oxygen Species (mROS) and Prevents Sudden Cardiac Death (SCD) in Non-ischemic Heart Failure (HF)

Introduction: Current therapies for SCD are limited. Bilateral sympathetic stellate ganglionectomy ( BSG ) is a promising new adjunctive therapy in patients with ischemic HF who have incessant ventricular tachyarrhythmias ( VT/VF ) despite optimal medical management. The underlying mechanisms are unknown. The effect of BSG in non-ischemic HF is unclear. Hypothesis: BSG prevents VT/VF and SCD in non-ischemic HF by restoring sympathovagal balance and reducing mROS. Methods: We used a unique pressure-overload guinea pig model that closely mimics human non-ischemic HF, including a high incidence of spontaneous VT/VF/SCD. We randomized the animals to non-failing controls, HF+Sham, or HF+BSG surgery. We used intention to treat analysis to evaluate VT/VF-free survival. We analyzed continuous ECG (VT/VF burden, heart rate variability, QT variability) and echo (cardiac function). In isolated left ventricular (LV) myocytes, we measured Ca 2+ transients and mitochondrial reactive oxygen species (mROS) using targeted ratiometric probes. Results: Half of the HF+Sham animals experienced SCD in 4 weeks. In contrast, BSG abolished SCD, reduced VT/VF, and increased parasympathetic tone (beyond corresponding reductions in sympathetic tone). Fractional shortening of the LV was markedly reduced in HF+Sham (0.28±0.02) vs. control (0.50±0.01), but preserved by BSG (0.45±0.02). Whereas HF+Sham increased mROS levels in LV myocytes (fractional oxidation, F ox : 0.53±0.015) compared to control (0.29±0.020), BSG reduced mROS (0.38±0.035). Mitochondrial antioxidant capacity, as indexed by H 2 O 2 challenge of LV myocytes, was compromised in HF+Sham (F ox : 0.81±0.040) compared to control (0.44±0.061), but preserved by BSG (0.48±0.023). Conclusions: Surgical BSG prevents SCD in non-ischemic HF by reducing mROS, decreasing sympathetic tone, and by increasing parasympathetic tone (possibly by facilitating cholinergic transdifferentiation). This promising new minimally-invasive surgical therapy may be particularly useful in patients with non-ischemic HF on optimal medical therapy who require recurrent ICD shocks to prevent SCD. Patients in the early stages of HF who are not eligible for ICDs but remain at higher SCD risk may also benefit from BSG surgery.

Abstract 115: Surgical Bilateral Stellate Ganglionectomy Reduces Mitochondrial Reactive Oxygen Species (mROS) and Prevents Sudden Cardiac Death (SCD) in Non-ischemic Heart Failure (HF)

Introduction: Current therapies for SCD are limited. Bilateral sympathetic stellate ganglionectomy ( BSG ) is a promising new adjunctive therapy in patients with ischemic HF who have incessant ventricular tachyarrhythmias ( VT/VF ) despite optimal medical management. The underlying mechanisms are unknown. The effect of BSG in non-ischemic HF is unclear. Hypothesis: BSG prevents VT/VF and SCD in non-ischemic HF by restoring sympathovagal balance and reducing mROS . METHODS: We used a unique pressure-overload guinea pig model that closely mimics human non-ischemic HF, including a high incidence of spontaneous VT/VF/SCD. We randomized the animals to non-failing controls, HF+Sham, or HF+BSG surgery. We used intention to treat analysis to evaluate VT/VF-free survival. We analyzed continuous ECG (VT/VF burden, heart rate variability, QT variability) and echo (cardiac function). In isolated left ventricular (LV) myocytes, we measured Ca 2+ transients and mitochondrial reactive oxygen species (mROS) using targeted ratiometric probes. Results: Half of the HF+Sham animals experienced SCD in 4 weeks. In contrast, BSG abolished SCD, reduced VT/VF, and increased parasympathetic tone (beyond corresponding reductions in sympathetic tone). Fractional shortening of the LV was markedly reduced in HF+Sham (0.28±0.02) vs. control (0.50±0.01), but preserved by BSG (0.45±0.02). Whereas HF+Sham increased mROS levels in LV myocytes (fractional oxidation, F ox : 0.53±0.015) compared to control (0.29±0.020), BSG reduced mROS (0.38±0.035). Mitochondrial antioxidant capacity, as indexed by H 2 O 2 challenge of LV myocytes, was compromised in HF+Sham (F ox : 0.81±0.040) compared to control (0.44±0.061), but preserved by BSG (0.48±0.023). Conclusions: Surgical BSG prevents SCD in non-ischemic HF by reducing mROS, decreasing sympathetic tone, and by increasing parasympathetic tone (possibly by facilitating cholinergic transdifferentiation). This promising new minimally-invasive surgical therapy may be particularly useful in patients with non-ischemic HF on optimal medical therapy who require recurrent ICD shocks to prevent SCD. Patients in the early stages of HF who are not eligible for ICDs but remain at higher SCD risk may also benefit from BSG surgery.

Productivity Shocks and Repayment Behavior in Rural Credit Markets: A Framed Field Experiment

Improving rural credit markets requires a good understanding of the root causes of market failures and taking necessary steps to address them. This paper investigates the role of productivity shocks in borrowers repayment choices. Using a framed field experiment that simulated a repeated interaction in an input credit market, the analysis finds strong evidence that adverse productivity shocks lead to higher default, even when they do not induce negative returns. This relationship is robust to the presence of an information exchange system enforcing dynamic incentives. The findings suggest that recurrent shocks such as those resulting from the harmful effects of climate change could exacerbate failures in rural credit markets, undermining hard-won progress toward rural financial inclusion.

Exploring households' resilience to climate change-induced shocks using Climate Resilience Index in Dinki watershed, central highlands of Ethiopia.

This study assessed households’ resilience to climate change-induced shocks in Dinki watershed, northcentral highlands of Ethiopia. The data were collected through a cross-sectional survey conducted on 288 households, three focus group discussions, and 15 key informant interviews. The Climate Resilience Index (CRI) based on the three resilience capacities (absorptive, adaptive and transformative) frame was used to measure households’ resilience to climate change-induced shocks on an agro-ecological unit of analysis. A principal component analysis (PCA) and multiple regression analysis were used to identify determinant factors and indicators to households’ resilience, respectively. Findings indicate that the indexed scores of major components clearly differentiated the study communities in terms of their agro-ecological zones. Specifically, the absorptive capacity (0.495) was the leading contributing factor to resilience followed by adaptive (0.449) and transformative (0.387) capacities. Likewise, the Midland was relatively more resilient with a mean index value of 0.461. Both the PCA and multiple regression analysis indicated that access to and use of livelihood resources, such as farmlands and livestock holdings, diversity of income sources, infrastructure and social capital were determinants of households’ resilience. In general, it might be due to their exposure to recurrent shocks coupled with limited adaptive capacities including underdeveloped public services, poor livelihood diversification practices, among others, the study communities showed minimal resilience capacity with a mean score of 0.44. Thus, in addition to short-term buffering strategies, intervention priority focusing on both adaptive and transformative capacities, particularly focusing on most vulnerable localities and constrained livelihood strategies, would contribute to ensuring long-term resilience in the study communities.

Strategies to Reduce Recurrent Shocks Due to Ventricular Arrhythmias in Patients with an Implanted Cardioverter-Defibrillator

Ventricular arrhythmias are a therapeutic challenge, owing to their relatively unpredictable and deadly nature. Many patients are treated with an implantable cardioverter-defibrillator for either primary or secondary prevention of ventricular arrhythmias, meaning those who are at high risk of versus those who have experienced ventricular arrhythmias or sudden cardiac arrest, respectively. Despite the life-saving benefit, ICD comes with the risk of recurrent shocks for both appropriate and inappropriate rhythms. Patients with recurrent shocks have a poor quality of life and increased mortality rates. In this article, we review data for optimal device settings, medical management and radiofrequency ablation strategies to minimise the frequency of ICD shock, with a focus on treatment of ventricular arrhythmias, to reduce patient morbidity and mortality, and to maximise wellbeing and quality of life.

Global warming impairs stock–recruitment dynamics of corals

Changes in disturbance regimes due to climate change are increasingly challenging the capacity of ecosystems to absorb recurrent shocks and reassemble afterwards, escalating the risk of widespread ecological collapse of current ecosystems and the emergence of novel assemblages1-3. In marine systems, the production of larvae and recruitment of functionally important species are fundamental processes for rebuilding depleted adult populations, maintaining resilience and avoiding regime shifts in the face of rising environmental pressures4,5. Here we document a regional-scale shift in stock-recruitment relationships of corals along the Great Barrier Reef-the world's largest coral reef system-following unprecedented back-to-back mass bleaching events caused by global warming. As a consequence of mass mortality of adult brood stock in 2016 and 2017 owing to heat stress6, the amount of larval recruitment declined in 2018 by 89% compared to historical levels. For the first time, brooding pocilloporids replaced spawning acroporids as the dominant taxon in the depleted recruitment pool. The collapse in stock-recruitment relationships indicates that the low resistance of adult brood stocks to repeated episodes of coral bleaching is inexorably tied to an impaired capacity for recovery, whichhighlights the multifaceted processes that underlie the global decline of coral reefs. The extent to which the Great Barrier Reef will be able to recover from the collapse in stock-recruitment relationships remains uncertain, given the projectedincreased frequency of extreme climate events over the next two decades7.

Redde Rationem: Keynes, Minsky and the Collapse of Long-Term Capital Management Twenty Years Later

The aim of this paper is to indicate, through study of the Long-Term Capital Management near-bankruptcy case, fallacies of modern financial theory. Model assumptions that determine the validity of theory must be realistic. The responsibility of academic community in the process of creating economic policy is significant since only valid theory could result in economic policies that would successfully deal with the instability of global world economy. On the other hand, if this fact remains ignored, it is reasonable to expect recurrent financial shocks in the future.

Impact of Formal Climate Risk Transfer Mechanisms on Risk-Aversion: Empirical Evidence from Rural Ethiopia

This study examines the effect of smallholder farmers’ access to a formal climate risk transfer mechanism on their risk preferences. Survey and experimental data were collected from smallholder farmers that have access to weather index-based crop insurance (WICI) in Ethiopia. We use an endogenous switching (ESP) model to address self-selection and simultaneity bias. Results from the ESP model show that farmers who purchased WICI are less likely to be risk-averse compared with non-purchaser farmers. Similarly, non-purchasers would have attained a significant reduction in their risk-aversion if they had taken up the insurance product. We also find that WICI has a positive and statistically significant effect on farmers’ real-life risk-taking behavior as exemplified by mineral fertilizer use. The implication of our findings is that formal climate risk transfer mechanisms can positively influence households’ economic decisions and outcomes, through reducing risk aversion. Therefore, they can possibly contribute to poverty alleviation and economic development within agrarian economies that are exposed to recurrent and severe climate shocks.

Indigenous Knowledge for Resilience and Adaptation in Pastoral Production System of Somali Regional State in Ethiopia

The study attempts to highlight the importance and opportunities of indigenous knowledge for resilience and adaptation of the pastoral production system in the Sheygosh woreda of Somali region of Ethiopia. The study used data from primary and secondary sources. The primary data collected through key informants, focus group discussions, observations, ranking, and life history. The study highlights the fact that indigenous knowledge for resilience and adaptation contributes to reducing of vulnerability results from climate variability and also plays a critical role in adaptation, mitigation and coping with hazards and shocks in the past time. However, due to recurrent hazards and prolonged shocks and climate change, the use of traditional knowledge of coping mechanisms are under tremendous threats and will not be viable and sustainable in the coming years. In conclusion, the indigenous knowledge in the pastoral community deserves to recognize and support in view of their coping with, adapting to and withstand to hazard and climate chance. Thus, it needs to integrate in policies of the country.

Vulnerability to recurrent shocks and disparities in gendered livelihood diversification in remote areas of Nigeria

New multidimensional indicators of vulnerability to disaster from external shocks were constructed using survey data covering 1750 respondents from rural Nigeria. Simple ordinary least squares and decomposition analysis were then used to examine the effect of recurrent shocks on livelihood diversification. The results elicited several findings. Although findings from the constructed vulnerability indices revealed overall high risks of disasters, females were disproportionally more vulnerable to cattle rustling. Conversely, both natural hazard-induced and cattle rustling-driven shocks have a strong negative impact on livelihood diversification. This effect is invariant regardless of the perceived gender of the respondents. Decomposition results show that recurrent shocks have moderate influences on inter-gender income disparities, as a larger proportion of the inequalities are explained by demographic characteristics. The findings point to a number of policy recommendations, most notably that the disaster prevention and management strategies should prioritise interventions that have a direct bearing on an individual's economic, human, and social capitals.

Monetary policy and business cycle fluctuations of the Lebanese economy

The aim of this paper is to analyze how aggregate activity in Lebanon fluctuates with regard to recurrent shocks. The research starts by identifying the Lebanese economic business cycle from the first quarter of 1998 to the fourth quarter of 2015 adopting a statistical method. Furthermore, this research studies the relationship between the capacity utilization rate and the inflation rate to explore theoretically and empirically how monetary and real shocks account for the disturbances that affect the economic activity. Findings prove that, over the studied period, the Lebanese economy performs largely under its full capacity and that the capacity utilization rate is related to inflation in the short run, but not in the long run. In other terms, findings prove that monetary factors account for business cycle disturbances of the Lebanese economy in short run, but not in the long run.

Recurrent shocks from implantable cardiac defibrillator implanted 6months ago. What is the mechanism?

Recurrent shocks from implantable cardiac defibrillator implanted 6months ago. What is the mechanism?

Trends and Outcomes of Catheter Ablation for Ventricular Tachycardia in a Community Cohort.

This study examined the trend in growth of catheter ablation for ventricular tachycardia (VT) performed in the United States with analysis of rates and predictors of major adverse events. Sustained VT is a significant cause of sudden death, heart failure (HF), and recurrent shocks in implantable cardioverter-defibrillator (ICD) recipients. Catheter ablation for VT reduces arrhythmia recurrence. Limited data are available regarding the use, safety, and long-term outcomes after VT ablation. Using the U.S. Medicare database linked to the Social Security Death Index, we examined the annual use of VT ablation in 21,073 patients over 12 years, with 30-day risk of mortality, nonfatal major adverse events (MAEs), 1-year risk of mortality, re-hospitalization, repeat ablation, and factors associated with adverse outcomes. Among 21,073 patients (age 70 ± 9 years; 77% men; 90% white), there were 1,581 (7.5%) non-fatal MAEs within 30 days. There were 963 (4.6%) vascular complications, 485 (2.3%) pericardial complications, and 201 (1%) strokes and/or transient ischemic attacks. Mechanical circulatory support use was infrequent (2.3%). The 30-day and 1-year mortality rates were 4.2% and 15.0%, respectively. The 1-year incidence of repeat ablation was 10.2 per 100 person-years and re-hospitalization for HF or VT was 15.4 per 100 person-years and 18 per 100 person-years, respectively. Patients with an ICD had increased 30-day (4.9% vs. 0.86%) and 1-year mortality (17.5% vs. 2.54% [22.9 per 100 person-years vs. 3.1 per 100 person-years]; hazard ratio [HR]: 2.93; 95% confidence interval [CI]: 2.21 to 3.88). Rates of hospitalization for HF (18 per 100 person-years vs. 1.8 per 100 person-years; HR: 4.00; 95% CI: 2.78 to 5.78) or VT recurrence (22.7 per 100 person-years vs. 2.1 per 100 person-years; HR: 5.70; 95% CI: 4.09 to 7.96) were also higher at 1year. Between 2000 and 2012, annual VT ablation volumes increased >4-fold. Catheter ablation for VT is frequently performed. Short-term MAEs and 1-year mortality is significant and is highest in patients with an ICD. These findings may provide greater insight of outcomes in an unselected real-world population undergoing VT ablation.

Primary prevention with the implantable cardioverter-defibrillator in high-risk long-QT syndrome patients.

Prospective data regarding the role of implantable cardioverter-defibrillator (ICD) for the primary prevention of sudden cardiac death in patients with long QT syndrome (LQTS) is scarce. Herein, we explore the prospective Rochester LQTS ICD registry to assess the risk for appropriate shock in primary prevention in a real-world setting. We studied 212 LQTS patients that had ICD implantation for primary prevention. Best-subsets proportional-hazards regression analysis was used to identify clinical variables that were associated with the first appropriate shock. Conditional models of Prentice, Williams, and Peterson were utilized for the analysis of recurrent appropriate shocks. During a median follow-up of 9.2 ± 4.9 years, there were 42 patients who experienced at least one appropriate shock and the cumulative probability of appropriate shock at 8 years was 22%. QTc ≥ 550 ms [hazard ratio (HR) 3.94, confidence interval (CI) 2.08-7.46; P < 0.001) and prior syncope on β-blockers (HR 1.92, CI 1.01-3.65; P = 0.047) were associated with increased risk of appropriate shock. History of syncope while on β-blocker treatment (HR 1.87, CI 1.28-2.72; P = 0.001), QTc 500-549 ms (HR 1.68, CI 1.10-2.81; P = 0.048), and QTc ≥ 550 ms (HR 3.66, CI 2.34-5.72; P < 0.001) were associated with increased risk for recurrent appropriate shocks, while β-blockers were not protective (HR 1.03, CI 0.63-1.68, P = 0.917). LQT2 (HR 2.10, CI 1.22-3.61; P = 0.008) and multiple mutations (HR 2.87, CI 1.49-5.53; P = 0.002) were associated with higher risk for recurrent shocks as compared with LQT1. In this prospective ICD registry, we identified clinical and genetic variables that were associated appropriate shock risk. These data can be used for risk stratification in high-risk patients evaluated for primary prevention with ICD.

Left Lateral Fluoroscopy and Xiphisternum Removal to Avoid Bowel Perforation and Enable Epicardial Ventricular Tachycardia Ablation

An 81-year-old gentleman with idiopathic nonischemic dilated cardiomyopathy was admitted for endocardial and epicardial ablation of sustained ventricular tachycardia and fibrillation that had resulted in frequent recurrent implantable cardioverter-defibrillator shocks despite amiodarone therapy.

ELECTRICITY LOSSES AND POLITICAL REGIMES IN LATIN AMERICA

Here I discuss the idea that irregular access to electricity can be understood as a program of informal social transfers to provide insurance in volatile, developing countries. I analyze the expected consequences of democratization for the provision of irregular electricity. In democracies from developing countries, incumbents are challenged with the need to provide insurance given the highly volatile contexts in which they rule, and the absence of consumption-smoothing mechanisms to protect the population against recurrent negative shocks. I show descriptive evidence that transmissions and distribution (T\&amp;D) losses of electricity are counter-cyclical in democratic countries but are not in autocracies.

30-Year-Old Man With Outside-of-Hospital Cardiac Arrest

30-Year-Old Man With Outside-of-Hospital Cardiac Arrest

Update Ventricular Tachycardia

Idiopathic ventricular tachycardia: Frequent monomorphic premature ventricular contractions or non-sustained ventricular tachycardia without underlying structural heart disease is not a rare condition and may cause significant symptoms. A subgroup of patients develops IVT-associated cardiomyopathy. Current ESC guidelines recommend primary catheter ablation in symptomatic patients with right ventricular outflow tract IVT. Catheter ablation is also recommended in symptomatic patients with a left ventricular outflow tract (or other rare) origin, if antiarrhythmic drugs are ineffective or not desired.Ventricular tachycardia associated with structural heart disease: Scar-associated ventricular arrhythmias may cause sudden cardiac death in a variety of heart diseases. While ICD implantation has been shown to reduce mortality, repetitive ICD shocks impact on survival and quality of life. In a recent meta-analysis, both amiodarone and catheter ablation reduce the incidence of recurrent ICD shocks. Discontinuation of amiodarone due to side effects is common. Current ESC guidelines recommend both strategies (class 1 indication). Catheter ablation is also recommended in drug-resistant VT or electrical storm. A totally subcutaneous ICD is a novel option in patients not requiring pacing.