Inappropriate sinus tachycardia: a review.

Inappropriate sinus tachycardia (IST) has been defined as a resting heart rate of >100 beats per minute and an average 24-hour heart rate >90 bpm with distressing symptoms resulting from the persistent tachycardia. IST is prevalent in 1% of the middle-aged population, mostly females. Rarely can elderly patients also present with IST. Possible mechanisms of IST include intrinsic sinus node abnormality, beta-adrenergic receptor stimulating autoantibody, beta-adrenergic receptor supersensitivity, muscarinic receptor autoantibody, or hyposensitivity, impaired baroreflex control, depressed efferent parasympathetic/vagal function, nociceptive stimulation, central autonomic overactivity, aberrant neurohumoral modulation, etc. Symptoms associated with IST are palpitations, chest pain, fatigue, shortness of breath, presyncope, and syncope. Despite these distressing symptoms, IST has not been associated with tachycardia-associated cardiomyopathy or increased major cardiovascular events. Various treatment options for patients with IST are ivabradine, beta-adrenergic blockers, calcium channel blockers, psychiatric evaluation, and exercise training. Although, endocardial radiofrequency ablation targeting the sinus node has been used as a treatment modality for otherwise treatment-refractory IST, the results have been dismal. The other modalities used for refractory IST treatment are endocardial modification of the sinus node using radiofrequency energy, combined endo and epicardial ablation of the sinus node, thoracoscopic epicardial ablation of the sinus node, sinus node sparing thoracoscopic and endocardial hybrid ablation. The goal of this review is to provide the readership with the pathophysiological basis of IST and its management options.

The Role of High-output His-bundle Pacing During Atrioventricular Node Ablation.

Atrioventricular (AV) junction ablation (AVJA) is an acceptable strategy to control the heart rate in atrial fibrillation (AF) with a high procedural success rate. However, a small subset of patients pose a technical challenge with the standard right-sided approach. High-output His-bundle pacing has been shown to help localize the His bundle in a difficult-to-ablate AV junction. We report a case series of patients with difficult-to-ablate AVJA and present strategies to troubleshoot them. In this small series of patients, we found that high-output His pacing can be an effective alternative for successfully localizing the AVJA site. In this series, we also observed that an inability to achieve His capture from the right side can predict failure of ablation using the standard right-sided approach and the consequent need for a left-sided approach.

Outcomes of hospitalizations with acute respiratory distress syndrome with and without atrial fibrillation - Analyses from the National Inpatient Sample (2004-2014).

BACKGROUND: Acute respiratory distress syndrome (ARDS) is associated with high mortality. Atrial fibrillation (AF) is a common arrhythmia seen in critically ill patients. The impact of AF on the outcomes in patients with ARDS is less understood. In this analysis we attempt to evaluate the association of concurrent AF and various clinical outcomes in patients with ARDS. METHODS: We conducted a retrospective analysis of adult discharges from the National Inpatient Sample (NIS) between 2004 and 2014. International Classification of Disease codes were used to identify those with ARDS and AF. RESULTS: We found 1,200,737 hospitalizations with ARDS, out of which 238,455 had concomitant diagnosis of AF. Hospitalizations with AF had higher prevalence of comorbidities including chronic pulmonary disease, diabetes mellitus, hypertension, obesity, congestive heart failure and renal failure. On adjusted analysis, AF was associated with increased odds of acute myocardial infarction, cardiogenic shock, pressor use, acute kidney injury, permanent pacemaker implantation, cardiac arrest, mechanical circulatory support use and higher length of stay and inflation-adjusted cost in hospitalizations with ARDS. However, there was no significant difference in adjusted all-cause mortality in ARDS with and without AF (25.42% vs 20.23%, p=0.53). CONCLUSIONS: AF is associated with worse clinical outcomes, higher length of stay and cost in ARDS hospitalizations as compared to those without AF.

Left-sided Macro-reentry or Right-sided Focal Tachycardia in Patients with Prior Pulmonary Vein Isolation: A Tale of Two Atria.

We report on three patients with prior pulmonary vein isolation who presented with atrial tachycardia/atrial flutter. During electrophysiology study, the whole tachycardia cycle length was mapped to the left atrium. Multiple ablation attempts failed to terminate the tachycardia and, subsequently, right atrial mapping revealed a focal early site of origin near the superior vena cava-right atrial junction in two patients and outside the coronary sinus ostium in one patient. In this report, we discuss the probable mechanism of these tachycardias.