Appropriate treatment for an inappropriate disease?

Abstract

Inappropriate sinus tachycardia (IST) is a poorly defined malady, of unclear provenance, whose utterance can incite heated debate among cardiologists and even electrophysiologists as to the diagnosis and management of this peculiar syndrome. Indeed, some believe that the only thing “inappropriate” about IST is its designation as a disease. However, despite our inability to reach an agreement, patients continue to suffer. But when all has been ruled out and the patient remains tortured by sinus tachycardia; when the “inappropriate” is affixed and rendered a “diagnosis”; relief must be offered. The standard “reassurance” and β‐ adrenergic blockade will sometimes suffice, but there are a number of patients whose symptoms remain despite all pharmacologic intervention. Many will accept their fate and be somewhat heartened by the knowledge that theirs is a benign condition. For some, however, the symptoms will exert such a toll on daily life that they would undergo invasive procedures in the hopes of relief. For these unfortunate few, sinus node ablation has been developed. The 2015 heart rhythm society expert consensus statement on the diagnosis and treatment of postural tachycardia syndrome, inappropriate sinus tachycardia, and vasovagal syncope suggests a Class III, level of evidence E (expert opinion) designation for sinus node modification/ ablation as “not recommended as a part of routine care for patients with IST” (emphasis mine), but “ablations may be offered in highly select circumstances or as part of research protocols.” This is appropriate, given the lack of randomized studies and consensus of approach for sinus node ablation. However, rather than representing a moratorium on ablation, perhaps this should be a call to improve our techniques. It is upon this background that Aalaei‐Andabili et al share their experience with a minimally invasive surgical approach in this issue of the Journal of Cardiovascular Electrophysiology. The authors report on 10 patients (eight female), all of which had undergone at least one prior attempt at standard endocardial catheter ablation. Three of these initial ablations were limited by phrenic nerve proximity to desired ablation sites. These patients underwent a thoracoscopically guided epicardial ablation with a bipolar radiofrequency (RF) clamp guided by activation mapping. Generally, the right atrium (RA)‐superior vena cava junction was encircled with the clamp. The stated endpoint was two‐fold: (a) abolition of p wave activity resulting in a junctional rhythm; or, (b) at least 20% decrease in atrial rate on isoproterenol ≥4 μg/min. Additional ablation was guided by additional mapping: If the focus migrated anteromedially between the RA appendage (RAA) and septum, this area was encircled by the clamp and ablated. In two patients, ablation was extended to the medial portion (I assume posteriorly) of the crista terminals (CTs) near the right pulmonary veins (PVs) and autonomic ganglion (AG) by encircling the right hilum (including the mass of tissue including the right PV, RA, and CT). If, however, the focus shifted toward the inferior vena cava, both epicardial RF and cryoablation were performed at this site. How many patients required this, or anteromedial RF, was not stated by the authors. Postoperatively, most patients were in sinus or ectopic atrial rhythms, while only two had resultant junctional rhythm. By 1‐2 month follow‐up, all displayed sinus or ectopic atrial rhythms. All patients experienced a significant decrease in heart rate, from 113.8 ± 21.8 (pre) to 79.8 ± 8.2 (mean ± SD) at postoperative day 1 (P < .001) and to a mean of 75.8 ± 8.1 on Holter at 30 days (P < .001; mean ± SD) bpm. Two patients had a recurrence and underwent repeat endocardial catheter ablation, one at 5 months and one at 13 months. The former required another endocardial ablation for both IST and a new atrial tachycardia. Complications were reported (pneumonia/reintubation, pericarditis, pulmonary embolism [PE]) but all recovered and no phrenic injury, pacemaker need, or death occurred. The single procedure success rate at 6 months was 88%. The authors should be congratulated for providing data on the surgical approach to the management of IST, for which only case reports had previously been published. While certainly superior to endocardial catheter ablation alone, the surgical success rate is