Justin Hayase

Percutaneous Stellate Ganglion Block Suppressing VT and VF in a Patient Refractory to VT Ablation

Electrical storm is a condition characterized by multiple episodes of ventricular tachycardia (VT) or ventricular fibrillation (VF) in a short period of time.

Rotor Stability Separates Sustained Ventricular Fibrillation From Self-Terminating Episodes in Humans

OBJECTIVES This study mapped human ventricular fibrillation (VF) to define mechanistic differences between episodes requiring defibrillation versus those that spontaneously terminate. BACKGROUND VF is a leading cause of mortality; yet, episodes may also self-terminate. We hypothesized that the initial maintenance of human VF is dependent upon the formation and stability of VF rotors. METHODS We enrolled 26 consecutive patients (age 64 ± 10 years, n = 13 with left ventricular dysfunction) during ablation procedures for ventricular arrhythmias, using 64-electrode basket catheters in both ventricles to map VF prior to prompt defibrillation per the institutional review board-approved protocol. A total of 52 inductions were attempted, and 36 VF episodes were observed. Phase analysis was applied to identify biventricular rotors in the first 10 s or until VF terminated, whichever came first (11.4 ± 2.9 s to defibrillator charging). RESULTS Rotors were present in 16 of 19 patients with VF and in all patients with sustained VF. Sustained, but not self-limiting VF, was characterized by greater rotor stability: 1) rotors were present in 68 ± 17% of cycles in sustained VF versus 11 ± 18% of cycles in self-limiting VF (p < 0.001); and 2) maximum continuous rotations were greater in sustained (17 ± 11, range 7 to 48) versus self-limiting VF (1.1 ± 1.4, range 0 to 4, p < 0.001). Additionally, biventricular rotor locations in sustained VF were conserved across multiple inductions (7 of 7 patients, p = 0.025). CONCLUSIONS In patients with and without structural heart disease, the formation of stable rotors identifies individuals whose VF requires defibrillation from those in whom VF spontaneously self-terminates. Future work should define the mechanisms that stabilize rotors and evaluate whether rotor modulation may reduce subsequent VF risk.

A case of a human ventricular fibrillation rotor localized to ablation sites for scar-mediated monomorphic ventricular tachycardia

Ventricular tachycardia (VT) and ventricular fibrillation (VF) are the most common causes of sudden cardiac death. Currently, knowledge of the reentrant mechanism of monomorphic VT circuits in relation to complex scar anatomy allows for various mapping techniques including electroanatomic and entrainment mapping to accomplish catheter ablation of VT.1, 2 Clinically, it may be observed that ablation to eliminate recurrent macro-reentrant VT may also eliminate recurrent VF, as defined for instance by electrograms from implanted cardioverter-defibrillators (ICD).3, 4 However, whether this represents elimination of the VT trigger for VF, or directly of the substrate for VF, is unclear since the mechanism of VF in relation to scar is not known. Recent work targeting localized rotors in atrial fibrillation ablation has shown promise,5 but its implications for VF are unknown. We report here a case where VT termination and a VF rotor occurred at spatially coincidental sites in a patient with ischemic cardiomyopathy, suggesting that VF rotors may localize to the same anatomic substrate that promotes VT.

Comparative efficacy of stellate ganglion block with bupivacaine vs pulsed radiofrequency in a patient with refractory ventricular arrhythmias

There is increasing interest in interventional therapies targeting the cardiac sympathetic nervous system to suppress ventricular arrhythmias. In this case report, we describe an 80-year-old patient with ischemic cardiomyopathy and multiple implantable cardioverter-defibrillator shocks due to refractory ventricular tachycardia and ventricular fibrillation who was unable to continue biweekly stellate ganglion block procedures using bupivacaine 0.25% for suppression of his arrhythmias. He had previously failed antiarrhythmic drug therapy with amiodarone, catheter ablation, and attempted surgical autonomic denervation. He underwent pulsed radiofrequency treatment (3 lesions, 2 minutes each, temperature 42°C, 2-Hz frequency, 20-millisecond pulse width) of the left stellate ganglion resulting in persistent arrhythmia suppression for more than 12 months duration. This represents the first report of a pulsed radiofrequency stellate ganglion lesion providing long-term suppression of ventricular arrhythmias. Further study of this technique in patients with refractory ventricular tachycardia or ventricular fibrillation is warranted.

Rotors exhibit greater Surface ECG variation during ventricular fibrillation than focal sources due to wavebreak, secondary rotors, and meander

Ventricular fibrillation is a common life‐threatening arrhythmia. The ECG of VF appears chaotic but may allow identification of sustaining mechanisms to guide therapy.

Defibrillation Testing During ICD Implantation – Should we or Should we Not?

The implantable cardioverter defibrillator (ICD) is an established therapy for improving mortality for primary and secondary prevention of sudden cardiac death. Whether to perform defibrillation threshold testing (DFT) either intraoperatively or post-operatively remains a controversial issue. The DFT is defined as the minimum energy required at which two shocks can successfully terminate ventricular fibrillation and dates from the era of surgically implanted devices with epicardial patches. Typically, a safety margin of at least 10J is employed for device programming, though some trial data suggest that a margin of 5J could be just as effective. Various methods have been utilized to perform DFT testing, and no particular method has been shown to be superior to another [Figure 1]. Previously, guideline recommendations addressed the indications for ICD implantation but did not comment on DFT testing. Recent consensus statements now provide some guidance as to when it is appropriate to perform or not perform DFT testing in light of new trial data. This review will address some of the risk factors for having a higher DFT, impact of DFT testing on patient outcomes, and some of the risks and contraindications of DFT testing.

Ventricular fibrillation: triggers, mechanisms and therapies.

Ventricular fibrillation (VF) is a common, life-threatening arrhythmia responsible for significant morbidity and mortality. Due to challenges in safely mapping VF, a comprehensive understanding of its mechanisms remains elusive. Recent findings have provided new insights into mechanisms that sustain early VF. Notably, the central role of electrical rotors and catheter-based ablation of VF rotor substrate have been recently reported. In this article, we will review data regarding four stages of VF: initiation, transition, maintenance and evolution. We will discuss the particular mechanisms for each stage and therapies targeting these mechanisms. We also examine inherited arrhythmia syndromes, including the mechanisms and therapies specific to each. We hope that the overview of VF outlined in this work will assist other investigators in designing future therapies to interrupt this life-threatening arrhythmia.