Benzy J. Padanilam

Differentiating junctional tachycardia and atrioventricular node re-entry tachycardia based on response to atrial extrastimulus pacing.

OBJECTIVES The purpose of this study was to differentiate non-re-entrant junctional tachycardia (JT) and typical atrioventricular node re-entry tachycardia (AVNRT). BACKGROUND JT may mimic AVNRT. Ablation of JT is associated with a lower success rate and a higher incidence of heart block. Electrophysiologic differentiation of these tachycardias is often difficult. METHODS We hypothesized that JT can be distinguished from AVNRT based on specific responses to premature atrial complexes (PACs) delivered at different phases of the tachycardia cycle: when a PAC is timed to His refractoriness, any perturbation of the subsequent His indicates that anterograde slow pathway conduction is involved and confirms a diagnosis of AVNRT. A PAC that advances the His potential immediately after it without terminating tachycardia indicates that retrograde fast pathway is not essential for the circuit and confirms a diagnosis of JT. This protocol was tested in 39 patients with 44 tachycardias suggesting either JT or AVNRT based on a short ventriculo-atrial interval and apparent AV node dependence. Tachycardias were divided into 3 groups: clinically obvious AVNRT, clinically obvious JT, and clinically indeterminate rhythm. RESULTS In the 26 cases of clinically obvious AVNRT, the sensitivity and specificity of the test were 61% and 100%, respectively. In the 9 cases of clinically obvious JT, the sensitivity and specificity were 100% and 100%, respectively. In the 9 cases of clinically indeterminate rhythm, the technique indicated AVNRT in 1 patient and JT in 7 patients, and the test was indeterminate in 1 patient. CONCLUSIONS The response to PACs during tachycardia can distinguish JT and AVNRT with 100% specificity in adult patients.

Ventricular arrhythmias in the absence of structural heart disease.

Ventricular arrhythmia (VA) in structurally normal hearts can be broadly considered under non-life-threatening monomorphic and life-threatening polymorphic rhythms. Monomorphic VA is classified on the basis of site of origin in the heart, and the most common areas are the ventricular outflow tracts and left ventricular fascicles. The morphology of the QRS complexes on electrocardiogram is an excellent tool to identify the site of origin of the rhythm. Although these arrhythmias are common and generally carry an excellent prognosis, rare sudden death events have been reported. Very frequent ventricular ectopy may also result in a cardiomyopathy in a minority of patients. Suppression of VA may be achieved using calcium-channel blockers, beta-adrenergic blockers, and class I or III antiarrhythmic drugs. Radiofrequency ablation has emerged as an excellent option to eliminate these arrhythmias, although certain foci including aortic cusps and epicardium may be technically challenging. Polymorphic ventricular tachycardia (VT) is rare and generally occurs in patients with genetic ion channel disorders including long QT syndrome, Brugada syndrome, catecholaminergic polymorphic VT, and short QT syndrome. Unlike monomorphic VT, these arrhythmic syndromes are associated with sudden death. While the cardiac gross morphology is normal, suggesting a structurally normal heart, abnormalities exist at the molecular level and predispose them to arrhythmias. Another fascinating area, idiopathic ventricular fibrillation and early repolarization syndrome, are undergoing research for a genetic basis.

Clinical Experience with Dofetilide in the Treatment of Patients with Atrial Fibrillation

Introduction: Dofetilide is the newest drug approved by the United States Food and Drug Administration for the treatment of patients with atrial fibrillation (AF). Few data on the efficacy and safety of dofetilide in a diverse group of patients are available. The aim of this study was to evaluate the results of dofetilide in a consecutive series of 69 patients with AF.

Complications associated with generator replacement in response to device advisories.

Introduction: Device recalls create problems for patients and physicians, for the risks associated with replacement may be greater than the device failure rate. In 2005, Medtronic, Guidant, and St. Jude had implantable cardioverter defibrillator (ICD) recalls on several of their devices. There were no national standards to guide physicians on the management of such patients. We report the reasons for and outcomes of ICD and pacemaker generator changes from our practice resulting from these advisories.

Association Between Left Ventricular Ejection Fraction Post-Cardiac Resynchronization Treatment and Subsequent Implantable Cardioverter Defibrillator Therapy for Sustained Ventricular Tachyarrhythmias

Background—Although cardiac resynchronization therapy (CRT) can improve left ventricular ejection fraction (LVEF), it is not known whether a specific level of improvement will predict future implantable cardioverter defibrillator (ICD) therapy. Methods and Results—CRT-defibrillator (CRT-D) was implanted in 423 patients at 1 institution between October 2, 2001 and January 19, 2007. A retrospective analysis was performed to evaluate the relationship between post–CRT-D LVEF and ICD therapy for ventricular tachyarrhythmias. A landmark population of 270 patients, with post–CRT-D LVEF measured and no ICD therapy within 1 year of device implantation, was followed for subsequent outcomes. Of these, 22 patients (8.2%) had subsequent appropriate ICD therapy over a median follow-up of 1.5 years. The estimated 2-year risk of appropriate ICD therapy is 3.0% (95% confidence interval [95% CI], 0%–6.3%), 2.1% (95% CI, 0%–5.0%), and 1.5% (95% CI, 0%–3.9%) for post–CRT-D LVEF of 45%, 50%, and 55%, respectively. In patients with a primary prevention indication for CRT-D, the estimated 2-year risk is 3.3% (95% CI, 0%–7.3%), 2.5% (95% CI, 0%–6.1%), and 1.9% (95% CI, 0%–5.1%) for post–CRT-D LVEF of 45%, 50%, and 55%, respectively. Conclusions—When a CRT responder demonstrates near normalization in LVEF to ≥45%, the incidence of ICD therapy for ventricular arrhythmias becomes low. Future studies are needed to determine whether an ICD is still needed in some of these patients at the time of generator replacement.

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 β-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.

Should Ablation Be First-Line Therapy and for Whom: The Antagonist Position

Atrial fibrillation (AF), the commonest cardiac arrhythmia with an adverse prognosis, has an estimated prevalence of 0.4% in general population.1 The disease is associated with significant morbidity related to symptoms, heart failure, and thromboembolism.2 Although AF is generally considered a non–life-threatening arrhythmia, it was associated with a 1.5- to 1.9-fold excess mortality after adjustment for preexisting cardiovascular conditions in the Framingham Heart Study.3 In the Atrial Fibrillation Follow-up Investigation of Rhythm Management (AFFIRM) study, a strategy of heart rate control was equivalent to heart rhythm control in terms of quality of life and all-cause mortality but superior in reducing hospitalizations.4 Anticoagulation with warfarin is maintained in either strategy if the patient has risk factors for thromboembolism. The major reason to pursue sinus rhythm in patients with AF is to improve their symptoms and quality of life. No studies have shown a reduction in stroke or heart failure when rhythm control is attempted in patients with AF. Once the decision to achieve rhythm control in a given patient has been made, physicians have to determine the best means of achieving this objective. Multiple randomized trials have demonstrated a modest but highly significant efficacy for antiarrhythmic medications.5 The limited long-term efficacy and high incidence of side effects of antiarrhythmic medications have prompted physicians to consider nonpharmacological therapies for AF.6 It has also been postulated, in a retrospective subanalysis of the AFFIRM study, that a strategy to maintain sinus rhythm without the adverse effects of antiarrhythmic medications may confer a survival advantage.7 In a nonrandomized study, Pappone et al8 compared the outcomes in a selected group of 589 patients who underwent circumferential pulmonary vein ablation with 582 age- and gender-matched cohort patients who received antiarrhythmic medications to maintain sinus rhythm. After a median follow-up of …

The Surface Electrocardiogram Predicts Risk of Heart Block During Right Heart Catheterization in Patients With Preexisting Left Bundle Branch Block: Implications for the Definition of Complete Left Bundle Branch Block

LBBB and Heart Block. Background: Patients with left bundle branch block (LBBB) undergoing right heart catheterization can develop complete heart block (CHB) or right bundle branch block (RBBB) in response to right bundle branch (RBB) trauma. We hypothesized that LBBB patients with an initial r wave (≥1 mm) in lead V1 have intact left to right ventricular septal (VS) activation suggesting persistent conduction over the left bundle branch. Trauma to the RBB should result in RBBB pattern rather than CHB in such patients.

Atrial fibrillation: goals of therapy and management strategies to achieve the goals.

The primary goals in the management of patients who have atrial fibrillation are prevention of stroke and tachycardia-induced cardiomyopathy and amelioration of symptoms. Each patient presents to a physician with a specific constellation of symptoms and signs, but, fortunately, most patients can be assigned to broad categories for therapy. For some, anticoagulation and rate control suffice, whereas others require attempts to restore and maintain sinus rhythm. Physicians and patients should be willing to alter therapeutic plans if an initial strategy of rate or rhythm control is unsuccessful.

Development of Rapid Preexcited Ventricular Response to Atrial Fibrillation in a Patient with Intermittent Preexcitation

Intermittent preexcitation during sinus rhythm is indicative of an accessory pathway at a very low risk for sudden death. We present the case of a 49‐year‐old man with intermittent preexcitation who subsequently developed rapid atrial fibrillation with a shortest preexcited R–R interval of 230 milliseconds. Electrophysiology study showed intermittent preexcitation at baseline and 1:1 anterograde accessory pathway conduction to 220 milliseconds in the presence of 1 mcg/min isoproterenol infusion. The pathway was successfully ablated at the lateral mitral annulus. Accessory pathways highly sensitive to catecholamines may show intermittent preexcitation at baseline with potential for rapid conduction during atrial fibrillation and sudden death. (J Cardiovasc Electrophysiol, Vol. 24, pp. 347‐350, March 2013)