Interventional treatment of ventricular tachycardia and electrical storm: From ablation of substrate and triggers to autonomic modulation by renal denervation

Effect of Renal Denervation on Cardiac Function and Inflammatory Factors in Heart Failure After Myocardial Infarction

Supplemental Digital Content is Available in the Text.

Heart failure (HF) affects around 100 million people and is a staggering burden for health care system worldwide. Rapid and sustained activation of inflammatory response is an important feature of HF after myocardial infarction. Sympathetic overactivation is also an important factor in the occurrence and progression of HF. The beneficial effect of renal denervation (RDN) has been demonstrated in HF. In the current study, we hypothesized that RDN improves cardiac function in HF canine models due to acute myocardial infarction (AMI) and reduced inflammation might be involved. Twenty-four beagles were randomized into the control (n = 8), HF (n = 8), and HF + RDN group (n = 8). The HF model after AMI was established by embolization the anterior descending distal artery with anhydrous ethanol in the HF and HF + RDN group. Bilateral renal artery ablation was performed in the HF + RDN group. Cardiac function, serum creatine kinase, creatine kinase-MB and NT-Pro BNP level, and expression of inflammation-related proteins in myocardial were examined. Because the paraventricular nucleus of the hypothalamus might be involved in inflammation-induced central neural excitation in HF and plays an important role in regulating extracellular fluid volume and sympathetic activity, expression of inflammation-related proteins in hypothalamus was also examined. AMI and post-AMI HF model was created successfully. Compared with the HF group, dogs in the HF + RDN group showed better cardiac function 4 weeks after AMI: lower left ventricular end-diastolic pressure, left ventricular end-diastolic dimension, and left ventricular end-systolic dimension and higher LEVF and left ventricular systolic pressure (P < 0.05 for all) were observed in the HF + RDN group. In addition, dogs in the HF + RDN group had slightly less ventricular fibrosis. Interestingly, RDN had lower expression of inflammation-related proteins including interleukin-6, tumor necrosis factors-α, nuclear factor κB, and monocyte chemotactic protein 1 (P < 0.05 for all) in both myocardial tissue and hypothalamus. RDN can improve cardiac function in dogs with HF after myocardial infarction. Our results suggested that RDN might affect cytokine-induced central neural excitation in HF and later affect sympathetic activity. Our results suggested a potential beneficial mechanism of RDN independent of mechanism involving renal afferent and efferent sympathetic nerves.

Renal Denervation Reduced Ventricular Arrhythmia After Myocardial Infarction by Inhibiting Sympathetic Activity and Remodeling

Background Ventricular arrhythmia after myocardial infarction is the most important risk factor for sudden cardiac death, which poses a serious threat to human health. As the correlation between autonomic nervous systemic dysfunction and heart rhythm abnormality has been gradually revealed, remedies targeting autonomic nervous system dysfunction, especially the sympathetic nerve, have emerged. Among them, renal denervation is noted for its powerful effect on the inhibition of sympathetic nerve activity. We aim to investigate whether renal denervation can reduce ventricular arrhythmia after myocardial infarction and thus decrease the risk of sudden cardiac death. In addition, we explore the potential mechanism with respect to nerve activity and remodeling. Methods and Results Twenty-four beagles were randomized into the control (n=4), renal denervation (n=10), and sham (n=10) groups. Permanent left anterior descending artery ligation was performed to establish myocardial infarction in the latter 2 groups. Animals in the renal denervation group underwent both surgical and chemical renal denervation. Compared with dogs in the sham group, dogs in the renal denervation group demonstrated attenuated effective refractory period shortening and inhomogeneity, flattened restitution curve, increased ventricular threshold, and decreased ventricular arrhythmia. Heart rate variability assessment, catecholamine measurement, and nerve discharge recordings all indicated that renal denervation could reduce whole-body and local tissue sympathetic tone. Tissue analysis revealed a significant decrease in neural remodeling in both the heart and stellate ganglion. Conclusions Surgical and chemical renal denervation decreased whole-body and local tissue sympathetic activity and reversed neural remodeling in the heart and stellate ganglion. Consequently, renal denervation led to beneficial remodeling of the electrophysiological characteristics in the infarction border zone, translating to a decrease in ventricular arrhythmia after myocardial infarction.

Propranolol Versus Metoprolol for Treatment of Electrical Storm in Patients With Implantable Cardioverter-Defibrillator

BACKGROUND

Electrical storm (ES), characterized by unrelenting recurrences of ventricular arrhythmias, is observed in approximately 30% of patients with implantable cardioverter-defibrillators (ICDs) and is associated with high mortality rates.

OBJECTIVES

Sympathetic blockade with β-blockers, usually in combination with intravenous (IV) amiodarone, have proved highly effective in the suppression of ES. In this study, we compared the efficacy of a nonselective β-blocker (propranolol) versus a β₁-selective blocker (metoprolol) in the management of ES.

METHODS

Between 2011 and 2016, 60 ICD patients (45 men, mean age 65.0 ± 8.5 years) with ES developed within 24 h from admission were randomly assigned to therapy with either propranolol (160 mg/24 h, Group A) or metoprolol (200 mg/24 h, Group B), combined with IV amiodarone for 48 h.

RESULTS

Patients under propranolol therapy in comparison with metoprolol-treated individuals presented a 2.67 times decreased incidence rate (incidence rate ratio: 0.375; 95% confidence interval: 0.207 to 0.678; p = 0.001) of ventricular arrhythmic events (tachycardia or fibrillation) and a 2.34 times decreased rate of ICD discharges (incidence rate ratio: 0.428; 95% CI: 0.227 to 0.892; p = 0.004) during the intensive care unit (ICU) stay, after adjusting for age, sex, ejection fraction, New York Heart Association functional class, heart failure type, arrhythmia type, and arrhythmic events before ICU admission. At the end of the first 24-h treatment period, 27 of 30 (90.0%) patients in group A, while only 16 of 30 (53.3%) patients in group B were free of arrhythmic events (p = 0.03). The termination of arrhythmic events was 77.5% less likely in Group B compared with Group A (hazard ratio: 0.225; 95% CI: 0.112 to 0.453; p < 0.001). Time to arrhythmia termination and length of hospital stay were significantly shorter in the propranolol group (p < 0.05 for both).

CONCLUSIONS

The combination of IV amiodarone and oral propranolol is safe, effective, and superior to the combination of IV amiodarone and oral metoprolol in the management of ES in ICD patients.

Management of monomorphic ventricular tachycardia electrical storm in structural heart disease

Electrical storm (ES) is a life-threatening condition that is defined by three or more episodes of sustained ventricular tachycardia (VT), ventricular fibrillation (VF), or appropriate shocks from an implantable cardioverter defibrillator (ICD) within 24 hours. The most common form of ES is monomorphic VT. It carries poor outcome despite all available intervention therapies. The therapies include rapid recognition of the condition, treatment of the reversible causes, ICD-reprogramming, antiarrhythmic drugs, sedation, and catheter ablation (CA). The first line antiarrhythmic drugs are amiodarone and β-blockers with superiority of propranolol over the others. The long-term use of the antiarrhythmic drugs is limited due to their adverse effects and drug-related proarrhythmic effect. The basic mechanism of monomorphic VT is re-entry pathway which can be targeted by CA. CA should be considered in drug refractory ES and patients should be referred in early course of disease. There are reported studies which showed the superiority of CA over the medical treatment in reducing the arrythmia burden and ICD appropriate shock. The survival benefit has been reported after successful ablation of ES in case series but to date no randomized control trial shows mortality benefit.

Catheter ablation in the treatment of electrical storm: Integrative review

BACKGROUND

The incidence of electrical storm (ES) has been increasing with the rise of the indicated uses of implantable cardioverter defibrillators (ICDs). It is estimated that 20% of patients will evolve to have this complication. Ablative therapy stands out as the treatment for this condition when it is refractory to antiarrhythmic treatment. The objective was to define the current role of catheter ablation in the treatment of electrical storm.

METHODS

An integrative literature review was performed using the PubMed and BVS databases. All identified articles were screened and verified for eligibility by the authors.

RESULTS

Twenty-five out of the initial 951 articles were used in the final analysis. The categories listed for analysis included indication for ablation in ES, modality of the approach, therapeutic success, complications related to the procedure, mortality and cardiovascular follow-up and alternative therapeutic modalities by frequency of these categories in the articles researched.

CONCLUSION

Catheter ablation is the initial therapy for patients with ischemic cardiomyopathy (ICM) and ES. The endocardial approach presents more relevant success rates than the other therapeutic methods presented.

The clinical challenge of preventing sudden cardiac death immediately after acute ST-elevation myocardial infarction

Unfortunately, of all patients experiencing acute myocardial infarction (MI), usually in the form of ST-elevation MI, 25-35% will die of sudden cardiac death (SCD) before receiving medical attention, most often from ventricular fibrillation. For patients who reach the hospital, prognosis is considerably better and has improved over the years. Reperfusion therapy, best attained with primary percutaneous coronary intervention compared to thrombolysis, has made a big difference in reducing the risk of SCD early and late after ST-elevation MI. In-hospital SCD due to ventricular tachyarrhythmias is manageable, with either preventive measures or drugs or electrical cardioversion. There is general agreement for secondary prevention of SCD post-MI with implantation of a cardioverter defibrillator (ICD) when malignant ventricular arrhythmias occur late (>48 h) after an MI, and are not due to reversible or correctable causes. The major challenge remains that of primary prevention, that is, how to prevent SCD during the first 1-3 months after ST-elevation MI for patients who have low left ventricular ejection fraction and are not candidates for an ICD according to current guidelines, due to the results of two studies, which did not show any benefits of early (<40 days after an MI) ICD implantation. Two recent documents may provide direction as to how to bridge the gap for this early post-MI period. Both recommend an electrophysiology study to guide implantation of an ICD, at least for those developing syncope or non-sustained ventricular tachycardia, who have an inducible sustained ventricular tachycardia at the electrophysiology study. An ICD is also recommended for patients with indication for a permanent pacemaker due to bradyarrhythmias, who also meet primary prevention criteria for SCD.