Ripple mapping in ventricular tachycardia substrate mapping and ablation of nonischemic ventricular tachycardia.

INTRODUCTION: Substrate-based ablation for ventricular tachycardia (VT) using Ripple map (RM) is an effective treatment strategy for patients with ischemic cardiomyopathy but has yet to be evaluated in patients with nonischemic cardiomyopathy (NICMO). The aim of this study is to determine the feasibility and effectiveness of an RM-based ablation for NICMO patients. METHODS AND RESULTS: This was a single-center, retrospective study including all NICMO patients undergoing VT ablation at St Vincent Hospital between January 1, 2018 and January 12, 2019. Retrospective RM analysis was performed on those that had a substrate-based ablation to identify the location and number of Ripple channels as well as their proximity to ablation lesions. Thirty-three patients met the inclusion criteria and had a median age of 65 (58, 73.5) with 15.2% of the population being female, and were followed for a median duration of 451 (217.5, 586.5) days. Of these patients, 23 (69.7%) had a substrate-based ablation with a median procedural duration of 196.4 (186.8, 339) min, 1946 (517, 2750) points collected per map, and 277 (141, 554) points were within the scar. Two (8.6%) procedural complications occurred, and 7 (30.4%) patients had VT recurrence during follow-up. RM analysis revealed an average of two Ripple channels and the patients without VT recurrence had ablation performed closer to the Ripple channels: 0 (0, 4.7) versus 14.3 (0, 23.5) cm; p = .02. CONCLUSION: An RM-based substrate ablation can be performed in NICMO patients and ablation within Ripple channels is a predictor of VT freedom.

Rapid detection of isthmus block and rhythm change using local electrogram changes during complex atrial flutter ablation.

AIMS: Multiple re-entry circuits may operate simultaneously in the atria in the form of dual loop re-entry using a common isthmus, or multiple re-entrant loops without a common isthmus. When two or more re-entrant circuits coexist, ablation of an individual isthmus may lead to a seamless transition (without significant changes in surface electrocardiogram, coronary sinus activation or tachycardia cycle length) to a second rhythm, and the isthmus block can go unnoticed. METHODS AND RESULTS: We hypothesize and subsequently illustrate in three patient cases, methods to rapidly identify a transition in the rhythm and isthmus block using local electrogram changes at the ablation site. CONCLUSION: Local activation sequence changes, electrogram timing, and the behaviour of pre-existing double potentials can reveal isthmus block promptly when rhythm transitions occur during ablation of multiloop re-entry tachycardias.

Mechanism and interpretation of two-for-one response to premature atrial complexes during atrioventricular node re-entry tachycardia.

AIMS: The response to premature atrial complexes (PACs) during tachycardia has been shown to differentiate atrioventricular nodal re-entrant tachycardia (AVNRT) from focal junctional tachycardia (JT). His refractory PAC (HrPACs) perturbing the next His (resetting with fusion) is diagnostic of AVNRT and such a late PAC fusing with the native beat cannot reset the focal source of JT. Early PAC advancing the immediate His with continuation of tachycardia suggests JT but can also occur in AVNRT due to simultaneous conduction through the AV nodal fast and slow pathways [two-for-one response (TFOR)]. The objective of this study was to evaluate the incidence and mechanism of TFOR after early premature atrial complexes (ePACs) during AVNRT and to differentiate it from the known response to ePACs during JT. METHODS AND RESULTS: Typical AVNRT cases were diagnosed using standard criteria. We evaluated the responses to scanning PACs delivered during tachycardia in 100 patients undergoing AV node slow pathway modification for AVNRT. The responses to HrPACs and ePACs delivered from coronary sinus os or high right atrium were retrospectively reviewed. In 10 patients, ePACs advanced the immediate His with continuation of tachycardia. In all 10 cases, HrPACs advanced the next His, confirming AVNRT as the mechanism, and indicating a TFOR. CONCLUSION: A TFOR can occur in a small number of patients during AVNRT and is therefore not diagnostic of JT. However, HrPACs always perturbed the next His in these cases, confirming the diagnosis of AVNRT and allowing for differentiation from JT.

Predictors of successful ultrasound-guided lead implantation.

BACKGROUND: Technical advances have improved the safety of cardiac implantable electronic device (CIED) insertion, but periprocedural complications persist. Despite ultrasound (US) guidance for vascular access being feasible and exhibiting shorter fluoroscopy times, it is not widely adopted for insertion of CIEDs. Thus, we studied the use of US for CIED insertion to (1) quantify the success rate of venous cannulation, (2) identify predictors of failed cannulation, and (3) quantify the rate of complications using US guidance. METHODS: We studied 166 consecutive patients who underwent US-guided CIED implantation. Anatomic parameters of the axillary vein were measured. The primary outcome was success (group 1) or failure (group 2) to obtain vascular access utilizing US guidance. Secondary outcomes included pneumothorax and hematoma. RESULTS: Successful US-guided cannulation occurred in 154 of 166 patients (93%). No patient had a pneumothorax. Hematoma occurred in 1 of 166 patients (0.01%). Group 2 exhibited higher male proportion at 11 of 12 (92%) compared with 94 of 154 (61%) in group 1 (P = .03), increased vein depth at 3.84 versus 2.85 cm (P = .003), more right-sided implants (P = .03), higher weight at 104.6 versus 85.3 kg (P = .017), higher body mass index at 35.6 versus 29.2 kg/m2 (P = .049), and higher body surface area at 2.24 versus 1.99 m2 (P = .013). Other parameters were statistically nonsignificant. In multivariate analysis, vein depth remained significantly associated with failure. CONCLUSION: Using US guidance for CIED implantation is successful in the vast majority (93%) of patients. Rare cases of unsuccessful cannulation were associated with right-sided implants and increased venous depth.

Slow atrioventricular nodal pathway affecting fast pathway conduction.

A 15-year-old girl with a history of paroxysmal supraventricular tachycardia underwent an electrophysiology study (EPS) for diagnosis and ablation. Her baseline electrocardiogram and echocardiogram were normal. At EPS, she had dual atrioventricular nodal (AVN) conduction, but isoproterenol was needed to initiate the slow-fast form of AVN reentry. Before ablation without any isoproterenol, she began to have a spontaneous block in the fast pathway with continuous conduction over the slow pathway. After ablation of the slow pathway, all complexes conducted over the fast pathway during a 25-year follow-up. Possible electrotonic interaction between the slow and fast pathways is proposed as the mechanism for this phenomenon.

Cardiac resynchronization therapy reverses severe dyspnea associated with acceleration-dependent left bundle branch block in a patient with structurally normal heart.

A 55-year-old woman presented with severe dyspnea during acceleration-dependent left bundle branch block (LBBB). Metoprolol initially ameliorated symptoms by preventing the heart rate at which LBBB occurred. Over time LBBB presented at slower heart rates and the patient developed recurrent dyspnea during an activity that correlated with the development of LBBB on event monitors and exercise stress testing. A biventricular pacemaker was implanted, and the patient's symptoms remain resolved after a follow-up of over 4 years. More research is needed to define the use of cardiac resynchronization therapy in patients with normal heart function.

Single-center experience of the FIRM technique to ablate paroxysmal and persistent atrial fibrillation.

INTRODUCTION: Focal impulse and rotor modulation (FIRM)-guided ablation has had mixed results of published success, and most studies have had a follow-up for a year or less. We aimed to study a consecutive group of patients followed for at least 1.5 years, subgrouped into those with an initial FIRM ablation and those with a previous, failed ablation who now received a FIRM guided one, to evaluate for success in each group and factors that might affect success. METHODS: Of 181 patients, 167 were available for analysis. Group 1 (n = 122) had a first or primary ablation (paroxysmal atrial fibrillation [PAF] 51; persistent atrial fibrillation [PeAF] 71) and group 2 (n = 45) had a redo ablation (PAF 18; PeAF 27). All patients were done under general anesthesia. FIRM mapping was done in the right atrium first and then the left, and only rotors consistently seen on multiple epochs were ablated, using 15 to 30 W. Rotor ablation was discontinued when remapping showed elimination of rotational activity at the site. Wide area catheter ablation was done for pulmonary vein isolation (PVI). Routine follow-up was at 3, 6, and 12 months of the first year, with a Holter monitor at 6 months, and then every 6 months thereafter. Event recorders were given to patients with potential arrhythmic symptoms. RESULTS: Mean follow-up was 16 months. Nearly 40% of patients had obstructive sleep apnea; mean body mass index was 32; and average left atrial size was 39.7 mm and 46.2 mm for PAF and PeAF patients, respectively. Freedom from atrial arrhythmia recurrence was: in group 1 patients, 82.4% for PAF and 67.6% for PeAF patients; in group 2 patients, 83.3% for PAF, but only 40.7% for PeAF patients. Comparing outcomes for the first 10 patients studied to the next 20 or more done by three operators showed no difference, suggesting no learning curve affecting the ablation results. Furthermore, the univariate analysis did not show any demographic factor to have an independent significance for ablation success or failure. Spontaneous termination during rotor ablation occurred in 76.8% of PAF and 27.6% of PeAF patients but did not affect the long-term outcomes for maintenance of sinus rhythm. CONCLUSIONS: FIRM-guided atrial ablation plus PVI in our patient population resulted in good success from a recurrence of atrial arrhythmias in patients undergoing an initial ablation procedure. For those with persistent AF undergoing a second procedure now using FIRM guidance plus PVI, the results are lower. Further research is needed to define better the appropriate population for FIRM-guided ablation and the degree of ablation needed for success in these patients.

Arrhythmia induction using isoproterenol or epinephrine during electrophysiology study for supraventricular tachycardia.

BACKGROUND: Electrophysiology study (EPS) is an important part of the diagnosis and workup for supraventricular tachycardia (SVT). Provocative medications are used to induce arrhythmias, when they are not inducible at baseline. The most common medication is the ß1-specific agonist, isoproterenol, but recent price increases have resulted in a shift toward the nonspecific agonist, epinephrine. OBJECTIVE: We hypothesize that isoproterenol is a better induction agent for SVT during EPS than epinephrine. METHODS: We created a retrospective cohort of 131 patients, who underwent EPS and required medication infusion with either isoproterenol or epinephrine for SVT induction. The primary outcome was arrhythmia induction. RESULTS: Successful induction was achieved in 71% of isoproterenol cases and 53% of epinephrine cases (P = 0.020). Isoproterenol was significantly better than epinephrine for SVT induction during EPS (odds ratio [OR], 2.35; 95% confidence interval [CI], 1.14-4.85; P = 0.021). There was no difference in baseline variables or complications between the two groups. Other variables associated with successful arrhythmia induction included a longer procedure duration and atrioventricular nodal re-entry tachycardia as the clinical arrhythmia. In a multivariable model, isoproterenol remained significantly associated with successful induction (OR, 2.57; 95% CI, 1.002-6.59; P = 0.05). CONCLUSIONS: Isoproterenol was significantly better than epinephrine for SVT arrhythmia induction. However, epinephrine was safe and successfully induced arrhythmias in the majority of patients who received it. Furthermore, when atropine was added in epinephrine-refractory cases, in a post hoc analysis there was no difference in arrhythmia induction between medications. Cost savings could thus be significant without compromising safety.

Troubleshooting electromagnetic interference in a patient with centrifugal flow left ventricular assist device and subcutaneous implantable cardioverter defibrillator.

A 25-year-old man with severe nonischemic dilated cardiomyopathy underwent subcutaneous implantable cardioverter defibrillator (S-ICD) implant and subsequently underwent HeartWare ventricular assist device (HVAD) placement. Postoperative interrogation revealed both primary and secondary S-ICD vectors inappropriately regarded sinus rhythm as "noise," and the alternate vector significantly undersensed sinus rhythm. The S-ICD was reinterrogated using high-resolution capture to visually confirm EMI with a dominant frequency in both the primary and secondary vectors of 46.67 Hz that fell within the S-ICD operational range of 9-60 Hz. The 46.67 Hz frequency correlated with the HVAD operational speed of 2,800 RPM. The HVAD pump speed was increased from 2,800 to 3,000 RPM, resulting in a dominant frequency of 50 Hz. The notch filter is nonprogrammable in S-ICDs. However, the built-in filter is 50 Hz for countries in European time zones as opposed to 60 Hz in US time zones due to differences in the anticipated noise from electrical sources within each continent. Thus, the S-ICD time zone was reprogrammed from EST to GMT, which reduced the notch filter from 60  to 50 Hz, resulting in S-ICD successfully eliminating EMI when the patient was in a supine position. The EMI interference was still intermittently present in the upright patient position. This case demonstrates the utility of high-resolution electrogram capture to identify the source and frequency of EMI in S-ICD and offers a potential avenue to troubleshoot dominant frequency oversensing by changing the device time zone.

Unknown Intracardiac Electrogram.

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Unknown Intracardiac Electrogram.

Watch a video presentation of this article. For additional educational resources, please visit Medtronic Academy .

Unknown Intracardiac Electrogram.

Watch a video presentation of this article. For additional educational resources, please visit Medtronic Academy .

Unknown Intracardiac Electrogram.

Watch a video presentation of this article. For additional educational resources, please visit Medtronic Academy .

Treatment of Atrial Fibrillation.

IMPORTANCE: Atrial fibrillation is a common arrhythmia that affects more than 2.5 million people in the United States and causes substantial morbidity and mortality, especially regarding the increased risk of stroke. OBJECTIVE: To summarize atrial fibrillation treatment exclusive of stroke prevention. EVIDENCE REVIEW: An Ovid MEDLINE comprehensive literature search was performed on atrial fibrillation therapy excluding anticoagulation and emphasizing studies published within the last 5 years through April 2015 (N = 5044 references). The 2014 atrial fibrillation guideline from the American Heart Association, the American College of Cardiology, and the Heart Rhythm Society also was reviewed. FINDINGS: Reversible causes of atrial fibrillation should be identified. Risk factor modification, including weight loss and treatment of hypertension, diabetes, and obstructive sleep apnea can reduce atrial fibrillation episodes. Appropriate anticoagulation is necessary for patients at substantial stroke risk regardless of rate or rhythm treatment strategy. Sinus rhythm is often needed to control symptoms; however, an alternative strategy for atrial fibrillation is appropriate rate control. Rate control is safe in older patients (those who are about age ≥65 years) followed up for a few years, but no such safety data exist for patients younger than 60 years or for those followed up for longer periods. Thus, selection of therapy is individualized, taking into account present and future medical problems for the patient. Choice of an antiarrhythmic drug is based on safety first vs efficacy. Catheter ablation is an effective nonpharmacological alternative that is often, but not always, the second-line treatment. Reduction of the frequency and duration of atrial fibrillation episodes that result in a significant improvement in quality of life is a good marker of drug treatment success and complete elimination of atrial fibrillation is not required in many patients. Rate control is usually achieved with a ß-blocker or non-dihydropyridine calcium channel blockers. It is important to assess adequate rate control during both rest and activity. If the ventricular rate goes uncontrolled for a prolonged period, tachycardia-mediated cardiomyopathy can occur. CONCLUSIONS AND RELEVANCE: Therapy for atrial fibrillation includes prevention and modification of inciting causes and appropriate anticoagulation. Rate control is necessary for all patients. Maintenance of sinus rhythm with drugs or catheter ablation should be considered based on the individual needs of each patient.