Cardiac dysfunction and prolonged hemodynamic deterioration after implantable cardioverter-defibrillator shock in patients with systolic heart failure

Defibrillation Testing in Patients Undergoing Replacement of the S-ICD Generator: Is There Still a Need?

BACKGROUND

Noninferiority of omitting intraoperative defibrillation threshold (DFT) testing has been documented for transvenous implantable cardioverter defibrillators (ICD) whereas data for the subcutaneous-ICD (S-ICD) regarding the need for DFT testing, especially during S-ICD generator replacement, is not available.

METHODS

A total of 112 consecutive patients who underwent S-ICD generator replacement and routine testing were included in this retrospective single-center study and analyzed regarding the outcome of intraoperative DFT.

RESULTS

The majority of patients (87.3%) were successfully tested during generator replacement with no major adverse events. PREATORIAN score was generally lower, while high voltage (HV) impedance increased compared to first implantation. The risk of conversion failure increased with the PRAETORIAN risk class, whereas patient characteristics did not impact conversion rates. PRAETORIAN score and HV impedance were shown to be the most accurate factors when predicting conversion failure. In all patients with an HV impedance <70 Ohm and a PREATORIAN score < 90 at the time of initial implantation DFT was successfully performed during generator replacement.

CONCLUSION

General omittance of DFT in S-ICD generator replacement is not advisable. New algorithms for low impedance DFT measurements during S-ICD query and PREATORIAN score at first implantation can be used to predict conversion failure. An impedance <70 Ohm and a PRAETORIAN score < 90 show a very low risk of conversion failure. In patients with a PRAETORIAN score > 150 DFT testing should be performed when the S-ICD generator is replaced until randomized data is available.

Cardiac arrest, stony heart, and cardiopulmonary resuscitation: An updated revisit

The post-resuscitation period is recognized as the main predictor of cardiopulmonary resuscitation (CPR) outcomes. The first description of post-resuscitation syndrome and stony heart was published over 50 years ago. Major manifestations may include but are not limited to, persistent precipitating pathology, systemic ischemia/reperfusion response, post-cardiac arrest brain injury, and finally, post-cardiac arrest myocardial dysfunction (PAMD) after successful resuscitation. Why do some patients initially survive successful resuscitation, and others do not? Also, why does the myocardium response vary after resuscitation? These questions have kept scientists busy for several decades since the first successful resuscitation was described. By modifying the conventional modalities of resuscitation together with new promising agents, rescuers will be able to salvage the jeopardized post-resuscitation myocardium and prevent its progression to a dismal, stony heart. Community awareness and staff education are crucial for shortening the resuscitation time and improving short- and long-term outcomes. Awareness of these components before and early after the restoration of circulation will enhance the resuscitation outcomes. This review extensively addresses the underlying pathophysiology, management, and outcomes of post-resuscitation syndrome. The pattern, management, and outcome of PAMD and post-cardiac arrest shock are different based on many factors, including in-hospital cardiac arrest vs out-of-hospital cardiac arrest (OHCA), witnessed vs unwitnessed cardiac arrest, the underlying cause of arrest, the duration, and protocol used for CPR. Although restoring spontaneous circulation is a vital sign, it should not be the end of the game or lone primary outcome; it calls for better understanding and aggressive multi-disciplinary interventions and care. The development of stony heart post-CPR and OHCA remain the main challenges in emergency and critical care medicine.

The validity of current implantable cardioverter-defibrillator guidelines in a real-world population of adults with congenital heart disease: A single-center experience

Aims

Sudden cardiac death (SCD) is a major cause of mortality in adults with congenital heart disease (ACHD). The role of implantable cardioverter-defibrillator (ICDs) in preventing SCD has been established, however, robust, clinical evidence-based guidelines are lacking in ACHD. The aim of this study was to evaluate the ICD guidelines in ACHD patients.

Methods and Results

A total of 131 ACHD patients (male: n = 96 (73.3%), mean age: 42.8 ± 14.7 years, mean follow-up: 40.9 ± 28.3 months) undergoing ICDs implantation between 2010 and 2017 were reviewed. Sixty-nine patients (52.6%) received ICDs for a primary prevention indication. 122 (93.3%) patients had congenital heart disease of moderate to severe complexity. CRT-D (implantable cardiac resynchronization defibrillator) was implanted in 55 (42.0%) patients. During follow-up, 23 patients (17.6%) received appropriate ICD therapy. According to the current guideline (PACES/HRS 2014), 84 (64.1%), 8 (6.1%), and 39 (29.8%) could be classified as Class Ⅰ, Class Ⅱa, and Class Ⅱb indication, respectively. Compared to patients with Class Ⅱa and IIb indication, those with Class Ⅰ indication received more appropriate therapy (P = 0.030). Multivariate analysis showed that age (per 10-years decrease; P = 0.015, HR 1.254 CI; 1.045-1.505) and creatinine (per 100-μmol/L increase; P = 0.019, HR 1.555 CI; 1.076-2.247) were associated with appropriate therapy.

Conclusion

Implantation of ICDs for preventing SCD based on current guidelines is reasonable. For patients with a borderline indication, younger age and renal dysfunction may aid in the selection of ICDs candidates.

The Defibrillation Conundrum: New Insights into the Mechanisms of Shock-Related Myocardial Injury Sustained from a Life-Saving Therapy

Implantable cardiac defibrillators (ICDs) are recommended to prevent the risk of sudden cardiac death. However, shocks are associated with an increased mortality with a dose response effect, and a strategy of reducing electrical therapy burden improves the prognosis of implanted patients. We review the mechanisms of defibrillation and its consequences, including cell damage, metabolic remodeling, calcium metabolism anomalies, and inflammatory and pro-fibrotic remodeling. Electrical shocks do save lives, but also promote myocardial stunning, heart failure, and pro-arrhythmic effects as seen in electrical storms. Limiting unnecessary implantations and therapies and proposing new methods of defibrillation in the future are recommended.

Acute pathophysiological myocardial changes following intra-cardiac electrical shocks using a proteomic approach in a sheep model

Implantable cardioverter-defibrillators (ICD) are meant to fight life-threatening ventricular arrhythmias and reduce overall mortality. Ironically, life-saving shocks themselves have been shown to be independently associated with an increased mortality. We sought to identify myocardial changes at the protein level immediately after ICD electrical shocks using a proteomic approach. ICD were surgically implanted in 10 individuals of a healthy male sheep model: a control group (N = 5) without any shock delivery and a shock group (N = 5) with the delivery of 5 consecutive shocks at 41 J. Myocardial tissue samples were collected at the right-ventricle apex near to the lead coil and at the right ventricle basal free wall region. Global quantitative proteomics experiments on myocardial tissue samples were performed using mass spectrometry techniques. Proteome was significantly modified after electrical shock and several mechanisms were associated: protein, DNA and membrane damages due to extreme physical conditions induced by ICD-shock but also due to regulated cell death; metabolic remodeling; oxidative stress; calcium dysregulation; inflammation and fibrosis. These proteome modifications were seen in myocardium both "near" and "far" from electrical shock region. N-term acetylated troponin C was an interesting tissular biomarker, significantly decreased after electrical shock in the "far" region (AUC: 0.93). Our data support an acute shock-induced myocardial tissue injury which might be involved in acute paradoxical deleterious effects such as heart failure and ventricular arrhythmias.

Impact of Implantable Cardioverter-Defibrillator Interventions on All-Cause Mortality in Heart Failure Patients: A Meta-Analysis

Implantable cardioverter-defibrillators (ICDs) have a unique role in the primary and secondary prevention of sudden cardiac death. However, appropriate and inappropriate ICD interventions [antitachycardia pacing (ATP) or shocks] can result in deleterious effects. The aim of our study was to systematically review the existing data about the impact of ICD interventions on all-cause mortality in heart failure patients with reduced ejection fraction (HFrEF). We systematically searched MEDLINE (by using PubMed Web-based search engine) without any limits until September 30, 2017. After screening 17,752 records, a total of 17 studies met our inclusion criteria and were included in our meta-analysis. Our data showed that in patients with HFrEF, appropriate [hazard ratio (HR), 2.00; 95% confidence interval (CI), 1.52-2.63; P < 0.01; I 88%] and inappropriate [HR, 1.30; 95% CI, 1.07-1.58; P < 0.01; I 26%] ICD interventions were significantly associated with increased all-cause mortality. However, neither appropriate ATP [HR, 1.27; 95% CI, 0.80-2.02; P = 0.30; I 62%] nor inappropriate ATP [HR, 1.01; 95% CI, 0.49-2.07; P = 0.98; I 46%] were significantly associated with all-cause mortality in this patient population. In conclusion, ICD shocks are associated with a worse prognosis in HFrEF.

The Value of the Tei Index in Predicting Implantable Cardioverter Defibrillator Shocks

Objectives:

An implantable cardioverter defibrillator (ICD) decreases the risk of sudden death in the appropriate patients. However, a relationship between ICD shocks and increased mortality and morbidity has been suspected. This report is an investigation of an association between ICD shocks and the Tei index, an echocardiographic parameter now commonly used to predict cardiovascular events.

Methods:

The basic characteristics of 250 patients with chronic heart failure who had an ICD implanted and 2 years of follow-up device recordings were retrospectively analyzed. Patients who received shock therapy during follow-up were compared with those who did not, based on demographic and other characteristics and the Tei index.

Results:

The mean Tei index value of ICD shock recipients was significantly higher than the score of non-recipients of ICD shock (0.70±0.10 vs 0.56±0.10; p<0.001). The percentage of patients for whom it was primary prevention who received either appropriate or inappropriate ICD shocks was 28.9%, whereas in those who received an ICD for secondary prevention, the percentage was 71.1% (p<0.001). ICD shock recipient patients were older, and had a greater rate of hypertension and smoking pack-years compared with those to whom an ICD shock was not delivered (p<0.001).

Conclusion:

The results of this study demonstrated a relationship between the Tei index and ICD shocks, either appropriate or inappropriate. The Tei index is a simple method to predict ICD shocks.

The Significance of Shocks in Implantable Cardioverter Defibrillator Recipients

Large-scale implantable cardioverter defibrillator (ICD) trials have unequivocally shown a reduction in mortality in appropriately selected patients with heart failure and depressed left ventricular function. However, there is a strong association between shocks and increased mortality in ICD recipients. It is unclear if shocks are merely a marker of a more severe cardiovascular disease or directly contribute to the increase in mortality. The aim of this review is to examine the relationship between ICD shocks and mortality, and explore possible mechanisms. Data examining the effect of shocks in the absence of spontaneous arrhythmias as well as studies of non-shock therapy and strategies to reduce shocks are analysed to try and disentangle the shocks versus substrate debate.

The Effects of Shock from Defibrillation Threshold Testing on Cardiac Systolic and Diastolic Function

BACKGROUND

Inappropriate implantable cardioverter defibrillator (ICD) shocks are associated with increased overall mortality. However, it remains unclear whether shocks from defibrillation threshold (DFT) testing directly impair cardiac function.

METHODS

DFT testing was performed in 34 patients who underwent ICD/cardiac resynchronization therapy with a defibrillator implantation/generator exchange. Heart rate and cardiac function, including left ventricular (LV) systolic pressure, LV end-diastolic pressure, peak positive and negative dp/dt ( + dp/dt and -dp/dt, respectively) of LV pressure, and the tau index, were assessed with a Mikro-Cath™ diagnostic pressure catheter (CD Leycom, Zoetermeer, the Netherlands). These parameters were measured before and 1 minute, 3 minutes, 5 minutes, 10 minutes, and 15 minutes after DFT testing.

RESULTS

Peak positive dp/dt increased over baseline at each interval (976 ± 229 mm Hg/s vs 1,039 ± 258, 1,049 ± 245, 1,042 ± 247, 1,037 ± 259, and 1,034 ± 254 mm Hg/s, respectively; P < 0.01). Furthermore, peak negative dp/dt (-1,140 ± 397 mm Hg/s vs -1,185 ± 447, 1,193 ± 435, -1,195 ± 434, -1,189 ± 449, and -1,186 ± 459 mm Hg/s, respectively; P < 0.01) and the tau index (65.1 ± 18.5 vs 62.5 ± 16.8*, 62.4 ± 15.9(**) , 63.0 ± 16.8*, and 62.8 ± 18.7*, respectively; *P < 0.05, (**) P < 0.01) decreased compared to those at baseline at each interval.

CONCLUSION

Shock after DFT testing improved LV systolic and diastolic function immediately, especially in patients with preserved LV ejection fraction.

Myocardial Dysfunction and Shock after Cardiac Arrest

Postarrest myocardial dysfunction includes the development of low cardiac output or ventricular systolic or diastolic dysfunction after cardiac arrest. Impaired left ventricular systolic function is reported in nearly two-thirds of patients resuscitated after cardiac arrest. Hypotension and shock requiring vasopressor support are similarly common after cardiac arrest. Whereas shock requiring vasopressor support is consistently associated with an adverse outcome after cardiac arrest, the association between myocardial dysfunction and outcomes is less clear. Myocardial dysfunction and shock after cardiac arrest develop as the result of preexisting cardiac pathology with multiple superimposed insults from resuscitation. The pathophysiology involves cardiovascular ischemia/reperfusion injury and cardiovascular toxicity from excessive levels of inflammatory cytokine activation and catecholamines, among other contributing factors. Similar mechanisms occur in myocardial dysfunction after cardiopulmonary bypass, in sepsis, and in stress-induced cardiomyopathy. Hemodynamic stabilization after resuscitation from cardiac arrest involves restoration of preload, vasopressors to support arterial pressure, and inotropic support if needed to reverse the effects of myocardial dysfunction and improve systemic perfusion. Further research is needed to define the role of postarrest myocardial dysfunction on cardiac arrest outcomes and identify therapeutic strategies.

Current treatment of ventricular arrhythmias: state of the art

Ventricular arrhythmias may be benign, requiring only evaluation for associated risks and then reassurance, or associated with a risk of sudden death or significant morbidity. Therapies for these arrhythmias have evolved considerably over the past 20 years. For some, a definitive, curative therapy is available in the form of catheter ablation. Others are best managed with an implantable cardioverter-defibrillator that provides effective arrhythmia termination and protection from sudden death, with antiarrhythmic drugs or ablation to control recurrent arrhythmias. Although progress has been substantial, many challenges remain.

Usefulness of high-sensitivity cardiac troponin T and brain natriuretic peptide as biomarkers of myocardial fibrosis in patients with hypertrophic cardiomyopathy

Myocardial fibrosis assessed by late gadolinium enhancement cardiac magnetic resonance imaging is associated with cardiovascular events in patients with hypertrophic cardiomyopathy (HC), but few data are available regarding the utility of biomarkers for detecting late gadolinium enhancement. The aim of this study was to examine serum levels of myoglobin, cardiac myosin light chain I, high-sensitivity cardiac troponin T (hs-cTnT), and creatine kinase-MB isoenzyme and plasma levels of brain natriuretic peptide (BNP) in relation to late gadolinium enhancement in 53 patients with HC. Levels of hs-cTnT and BNP were higher in 23 patients with late gadolinium enhancement than in 30 patients without it (p <0.01 for both). An hs-cTnT level ≥0.007 ng/ml or a BNP level ≥70 pg/ml had good diagnostic value for detecting late gadolinium enhancement, with sensitivity of 96% or specificity of 90% with the combination of these 2 biomarkers. The extent of late gadolinium enhancement was correlated with BNP level (p <0.01) but not with hs-cTnT level in 23 patients with HC with late gadolinium enhancement. The increase in the extent of late gadolinium enhancement was related to hs-cTnT level in 8 patients during 22 months of follow-up (p = 0.02). In conclusion, the combination of hs-cTnT and BNP is useful in detecting myocardial fibrosis in patients with HC. The findings of this study indicate that hs-cTnT is a direct marker of ongoing myocardial fibrosis and that BNP is a marker of left ventricular overload partially associated with myocardial fibrosis.