Stellate ganglion block and cardiac sympathetic denervation in patients with inappropriate sinus tachycardia.

BACKGROUND: Inappropriate sinus tachycardia (IST) remains a clinical challenge because patients often are highly symptomatic and not responsive to medical therapy. OBJECTIVE: To study the safety and efficacy of stellate ganglion (SG) block and cardiac sympathetic denervation (CSD) in patients with IST. METHODS: Twelve consecutive patients who had drug-refractory IST (10 women) were studied. According to a prospectively initiated protocol, five patients underwent an electrophysiologic study before and after SG block (electrophysiology study group). The subsequent seven patients had ambulatory Holter monitoring before and after SG block (ambulatory group). All patients underwent SG block on the right side first, and then on the left side. Selected patients who had heart rate reduction ≥15 beats per minute (bpm) were recommended to consider CSD. RESULTS: The mean (SD) baseline heart rate (HR) was 106 (21) bpm. The HR significantly decreased to 93 (20) bpm (P = .02) at 10 minutes after right SG block and remained significantly slower at 97(19) bpm at 60 minutes. Left SG block reduced HR from 99 (21) to 87(16) bpm (P = .02) at 60 minutes. SG block had no significant effect on blood pressure or HR response to isoproterenol or exercise (all P > .05). Five patients underwent right (n = 4) or bilateral (n = 1) CSD. The clinical outcomes were heterogeneous: one patient had complete and two had partial symptomatic relief, and two did not have improvement. CONCLUSION: SG blockade modestly reduces resting HR but has no significant effect on HR during exercise. Permanent CSD may have a modest role in alleviating symptoms in selected patients with IST.

Modulation of the autonomic nervous system through mind and body practices as a treatment for atrial fibrillation.

Atrial fibrillation is the most common symptomatic arrhythmia that is associated with stroke. Contemporary management of the disease is focused on anticoagulation to prevent stroke, coupled with catheter ablation to limit symptoms and prevent deleterious cardiac remodeling. Emerging data highlights the importance of lifestyle modification by managing sleep apnea, increasing physical activity, and weight loss. There is significant data that supports a link between the autonomic nervous system, arrhythmia development, and atrial fibrillation therapy. It is likely that lifestyle modification through these techniques that are aimed to reduce stress may also mediate atrial fibrillation development through this mechanism. This review examines how mind and body practices such as meditation, yoga, and acupuncture may influence the autonomic nervous system and mitigate atrial fibrillation progression and regression. Available evidence from molecular and anatomical levels through to clinical observations and translational clinical trials were scrutinized and a case established for these interventions as potential powerful mediators of anti-arrhythmic benefit.

Elimination of Purkinje Fibers by Electroporation Reduces Ventricular Fibrillation Vulnerability.

Background The Purkinje network appears to play a pivotal role in the triggering as well as maintenance of ventricular fibrillation. Irreversible electroporation ( IRE ) using direct current has shown promise as a nonthermal ablation modality in the heart, but its ability to target and ablate the Purkinje tissue is undefined. Our aim was to investigate the potential for selective ablation of Purkinje/fascicular fibers using IRE . Methods and Results In an ex vivo Langendorff model of canine heart (n=8), direct current was delivered in a unipolar manner at various dosages from 750 to 2500 V, in 10 pulses with a 90-µs duration at a frequency of 1 Hz. The window of ventricular fibrillation vulnerability was assessed before and after delivery of electroporation energy using a shock on T-wave method. IRE consistently eradicated all Purkinje potentials at voltages between 750 and 2500 V (minimum field strength of 250-833 V/cm). The ventricular electrogram amplitude was only minimally reduced by ablation: 0.6±2.3 mV ( P=0.03). In 4 hearts after IRE delivery, ventricular fibrillation could not be reinduced. At baseline, the lower limit of vulnerability to ventricular fibrillation was 1.8±0.4 J, and the upper limit of vulnerability was 19.5±3.0 J. The window of vulnerability was 17.8±2.9 J. Delivery of electroporation energy significantly reduced the window of vulnerability to 5.7±2.9 J ( P=0.0003), with a postablation lower limit of vulnerability=7.3±2.63 J, and the upper limit of vulnerability=18.8±5.2 J. Conclusions Our study highlights that Purkinje tissue can be ablated with IRE without any evidence of underlying myocardial damage.

Mortality and Cerebrovascular Events After Heart Rhythm Disorder Management Procedures.

BACKGROUND: Recognition of rates and causes of hard, patient-centered outcomes of death and cerebrovascular events (CVEs) after heart rhythm disorder management (HRDM) procedures is an essential step for the development of quality improvement programs in electrophysiology laboratories. Our primary aim was to assess and characterize death and CVEs (stroke or transient ischemic attack) after HRDM procedures over a 17-year period. METHODS: We performed a retrospective cohort study of all patients undergoing HRDM procedures between January 2000 and November 2016 at the Mayo Clinic. Patients from all 3 tertiary academic centers (Rochester, Phoenix, and Jacksonville) were included in the study. All in-hospital deaths and CVEs after HRDM procedures were identified and were further characterized as directly or indirectly related to the HRDM procedure. Subgroup analysis of death and CVE rates was performed for ablation, device implantation, electrophysiology study, lead extraction, and defibrillation threshold testing procedures. RESULTS: A total of 48 913 patients (age, 65.7±6.6 years; 64% male) who underwent a total of 62 065 HRDM procedures were included in the study. The overall mortality and CVE rates in the cohort were 0.36% (95% confidence interval [CI], 0.31-0.42) and 0.12% (95% CI, 0.09-0.16), respectively. Patients undergoing lead extraction had the highest overall mortality rate at 1.9% (95% CI, 1.34-2.61) and CVE rate at 0.62% (95% CI, 0.32-1.07). Among patients undergoing HRDM procedures, 48% of deaths directly related to the HDRM procedure were among patients undergoing device implantation procedures. Overall, cardiac tamponade was the most frequent direct cause of death (40%), and infection was the most common indirect cause of death (29%). The overall 30-day mortality rate was 0.76%, with the highest being in lead extraction procedures (3.08%), followed by device implantation procedures (0.94%). CONCLUSIONS: Half of the deaths directly related to an HRDM procedure were among the patients undergoing device implantation procedures, with cardiac tamponade being the most common cause of death. This highlights the importance of the development of protocols for the quick identification and management of cardiac tamponade even in procedures typically believed to be lower risk such as device implantation.

Electrophysiologic characteristics of ventricular arrhythmias arising from the aortic mitral continuity-potential role of the conduction system.

INTRODUCTION: Catheter ablation of ventricular arrhythmia (VA) at the fibrous aortic mitral continuity (AMC) has been described, yet the nature of the arrhythmogenic substrate remains unknown. METHODS: Procedural records of 528 consecutive patients undergoing ablation of VA at Mayo Clinic, Rochester, MN, were reviewed. The electrocardiographic and electrophysiologic characteristics of patients with successful ablation at the AMC were analyzed to characterize the underlying arrhythmogenic substrate. RESULTS: Of the 21 patients (mean age 53.2 ± 13.4 years, 47.6% male) who underwent ablation of VA at the AMC with acute success, prepotentials (PPs) were found at the ablation sites preceding the ventricular electrogram (VEGM) during arrhythmias in 13 (61.9%) patients and during sinus rhythm in 7 (53.8%) patients. VAs with PPs were associated with a significantly higher burden of premature ventricular complexes (PVCs; 26.1 ± 10.9% vs. 14.9 ± 10.1%, P = 0.03), shorter VEGM to QRS intervals (9.0 ± 28.5 milliseconds vs. 33.1 ± 8.8 milliseconds, P = 0.03), lower pace map scores (8.7 ± 1.6 vs. 11.4 ± 0.8, P = 0.001), and a trend toward shorter V-H intervals during VA (32.1 ± 38.6 milliseconds vs. 76.3 ± 11.1 milliseconds, P = 0.06) as compared to those without PP. A strong and positive correlation was found between V-H interval and QRS duration during arrhythmia in those with PPs (B = 2.11, R(2) = 0.97, t = 13.7, P < 0.001) but not in those without PPs. CONCLUSION: Local EGM characteristics and relative activation time of the His bundle suggest the possibility of conduction tissue as the origin for VA arising from the fibrous AMC. Specific identification and targeting of PPs when ablating VAs at this location may improve procedural success.

Parahisian pacing: technique, utility, and pitfalls.

Several observations and maneuvers in the electrophysiology (EP) laboratory are employed to identify whether retrograde ventriculoatrial conduction is via the atrioventricular (AV) node or an accessory pathway. Parahisian pacing is a unique maneuver where there is no change in the position of the catheter, the position of the stimulating electrode, nor the cycle length for pacing, but rather the pacing output is varied. The primary value for parahisian pacing is to distinguish between a septal accessory pathway and AV nodal conduction. However, more nuanced but just as reliable interpretation is possible to also help identify free-wall accessory pathways, intermittently conducting pathways, multiple accessory pathways, and various combinations of pathway and AV nodal retrograde conduction. In this review, we discuss the importance of correct technique and explain with examples some uncommon, yet instructive, findings when performing parahisian pacing.

Hypokalemia during the cooling phase of therapeutic hypothermia and its impact on arrhythmogenesis.

BACKGROUND: Mild to moderate therapeutic hypothermia (TH) has been shown to improve survival and neurological outcome in patients resuscitated from out-of-hospital cardiac arrest (OHCA) with ventricular fibrillation (VF) as the presenting rhythm. This approach entails the management of physiological variables which fall outside the realm of conventional critical cardiac care. Management of serum potassium fluxes remains pivotal in the avoidance of lethal ventricular arrhythmia. METHODS: We retrospectively analyzed potassium variability with TH and performed correlative analysis of QT intervals and the incidence of ventricular arrhythmia. RESULTS: We enrolled 94 sequential patients with OHCA, and serum potassium was followed intensively. The average initial potassium value was 3.9±0.7 mmol l(-1) and decreased to a nadir of 3.2±0.7 mmol l(-1) at 10 h after initiation of cooling (p<0.001). Eleven patients developed sustained polymorphic ventricular tachycardia (PVT) with eight of these occurring during the cooling phase. The corrected QT interval prolonged in relation to the development of hypothermia (p<0.001). Hypokalemia was significantly associated with the development of PVT (p=0.002), with this arrhythmia being most likely to develop in patients with serum potassium values of less than 2.5 mmol l(-1) (p=0.002). Rebound hyperkalemia did not reach concerning levels (maximum 4.26±0.8 mmol l(-1) at 40 h) and was not associated with the occurrence of ventricular arrhythmia. Furthermore, repletion of serum potassium did not correlate with the development of ventricular arrhythmia. CONCLUSIONS: Therapeutic hypothermia is associated with a significant decline in serum potassium during cooling. Hypothermic core temperatures do not appear to protect against ventricular arrhythmia in the context of severe hypokalemia and cautious supplementation to maintain potassium at 3.0 mmol l(-1) appears to be both safe and effective.