The autonomic nervous system plays a central role in the pathogenesis of multiple cardiac arrhythmias, including atrial fibrillation and ventricular tachycardia. As such, autonomic modulation ...represents an attractive therapeutic approach in these conditions. Notably, autonomic modulation exploits the plasticity of the neural tissue to induce neural remodeling and thus obtain therapeutic benefit. Different forms of autonomic modulation include vagus nerve stimulation, tragus stimulation, renal denervation, baroreceptor activation therapy, and cardiac sympathetic denervation. This review seeks to highlight these autonomic modulation therapeutic modalities, which have shown promise in early preclinical and clinical trials and represent exciting alternatives to standard arrhythmia treatment. We also present an overview of the various methods used to assess autonomic tone, including heart rate variability, skin sympathetic nerve activity, and alternans, which can be used as surrogate markers and predictors of the treatment effect. Although the use of autonomic modulation to treat cardiac arrhythmias is supported by strong preclinical data and preliminary studies in humans, in light of the disappointing results of a number of recent randomized clinical trials of autonomic modulation therapies in heart failure, the need for optimization of the stimulation parameters and rigorous patient selection based on appropriate biomarkers cannot be overemphasized.
In patients with coronary artery disease (CAD) undergoing percutaneous coronary intervention (PCI), dual antiplatelet therapy has been shown to effectively prevent stent thrombosis and other ischemic ...cardiovascular events. The frequent occurrence of atrial fibrillation (AF) and concomitant CAD in the same individuals, suggests that clinicians will encounter many patients treated with PCI who will require anticoagulant treatment for the prevention of the thromboembolic complications of AF.
In this narrative review we provide an overview and update of evidence regarding antiplatelet therapy in patients with AF undergoing PCI.
The combination of dual antiplatelet therapy with anticoagulants may further protect a patient from ischemic complications, at the cost, however, of a several-fold increased bleeding risk. The introduction of novel pharmaceutical agents in both categories implies that there is paucity of data regarding the efficacy and, more importantly, the safety of between-drug combinations.
Careful consideration of the patient's individual characteristics and assessment of the risk for bleeding and thrombotic events using validated risk prediction tools is of great importance in order to maximize the benefits for each patient, while minimizing the risk for hemorrhage.
Atrioventricular nodal reentrant tachycardia (AVNRT) should be classified as typical or atypical. The term 'fast-slow AVNRT' is rather misleading. Retrograde atrial activation during tachycardia ...should not be relied upon as a diagnostic criterion. Both typical and atypical atrioventricular nodal reentrant tachycardia are compatible with varying retrograde atrial activation patterns. Attempts at establishing the presence of a 'lower common pathway' are probably of no practical significance. When the diagnosis of AVNRT is established, ablation should be only directed towards the anatomic position of the slow pathway. If right septal attempts are unsuccessful, the left septal side should be tried. Ablation targeting earliest atrial activation sites during typical atrioventricular nodal reentrant tachycardia or the fast pathway in general for any kind of typical or atypical atrioventricular nodal reentrant tachycardia, are not justified. In this review we discuss current concepts about the tachycardia circuit, electrophysiologic diagnosis, and ablation of this arrhythmia.
Several trials have addressed whether bifurcation lesions require stenting of both the main vessel and side branch, but uncertainty remains on the benefits of such double versus single stenting of ...the main vessel only.
We have conducted a meta-analysis of randomized trials including patients with coronary bifurcation lesions who were randomly selected to undergo percutaneous coronary intervention by either double or single stenting. Six studies (n=1642 patients) were eligible. There was increased risk of myocardial infarction with double stenting (risk ratio, 1.78; P=0.001 by fixed effects; risk ratio, 1.49 with Bayesian meta-analysis). The summary point estimate suggested also an increased risk of stent thrombosis with double stenting, but the difference was not nominally significant given the sparse data (risk ratio, 1.85; P=0.19). No obvious difference was seen for death (risk ratio, 0.81; P=0.66) and target lesion revascularization (risk ratio, 1.09; P=0.67).
Stenting of both the main vessel and side branch in bifurcation lesions may increase myocardial infarction and stent thrombosis risk compared with stenting of the main vessel only.
Background
Recent anatomic and electrophysiologic evidence has provided new insight into the anatomic substrate. Previous reports on electroanatomic mapping (EAM) of the circuit of atrioventricular ...nodal reentrant tachycardia (AVNRT) have been limited by mapping only the triangle of Koch on the right side of the septum and by the use of conventional mapping tools. The objectives are to obtain comprehensive high-resolution mapping of typical AVNRT and to investigate the role of the atrioventricular ring tissues in the circuit.
Methods
We employed EAM with the use of novel modules and algorithms for studying typical AVNRT from the right and the left sides of the septum.
Results
We performed extensive mapping of both the atrial septum and the septal vestibule of the tricuspid valve during typical AVNRT in 9 (6 females) patients, aged 49.6 ± 12.1 years. In two of these, left septal mapping was also obtained through the aorta. The earliest initial activation was variable, emanating from the superior or medial septum. The impulse consistently appeared below the orifice of the coronary sinus, at the site where its inferoanterior margin merged with the septal vestibule of the tricuspid valve at its entrance to the right atrium. It then returned to the initial activation site, presumably through the septal vestibular myocardium. The left septal activation area corresponded to that recorded on the right side.
Conclusions
Typical AVNRT uses a circuit confined within the pyramid of Koch from the AV node to the septal isthmus, involving the myocardial walls of the pyramidal space.
Connexin staining and genotyping studies have identified the left inferior extension and the AV node itself as areas of low connexin 43 (Cx43) expression, and consequently slow conduction, thus ...suggesting that this is the main substrate of the slow pathway (Figure 1).24 The inferior nodal extensions at the inferior (posterior) part of the triangle of Koch and below the coronary sinus ostium, as depicted in the right anterior oblique projection, are the appropriate targets for successful ablation, either from the right or left septal side.18–20,25 Slow pathway ablation or modification as described is effective in both typical and atypical AVNRT.19 It is no longer necessary to create higher lesions or perform mapping during tachycardia. Recurrence rates are 2 % in typical and 5 % in atypical AVNRT.18,19 Recurrence is usually seen within the 3 months following a successful procedure in symptomatic patients with frequent episodes of tachycardia.20,25,29,30 However, in those aged ≤18 years, recurrence may occur up to 5 years post-ablation.31 Success rates are lower (82 %) and the risk of heart block higher (14 %) in patients with complex congenital heart disease.32 Advanced age is not a contraindication for slow pathway ablation.33 The pre-existence of first-degree heart block carries a higher risk of late AV block and the avoidance of extensive slow pathway ablation is preferable in this setting.34 Cryoablation may carry a lower risk of AV block, but this mode of therapy is associated with a significantly higher recurrence rate.35–37 Its favourable safety profile and higher long-term success rate in younger people make it especially attractive in children.38 There is no procedure-related mortality in most published studies, although in the Latin American Catheter Ablation Registry there was one death (corresponding to 0.02 % mortality) following tamponade.39 I believe that there is no such risk associated with AVNRT ablation in experienced centres today. Radiofrequency catheter ablation versus medical therapy for initial treatment of supraventricular tachycardia and its impact on quality of life and healthcare costs. Long-term outcomes on quality-of-life and health care costs in patients with supraventricular tachycardia (radiofrequency catheter ablation versus medical therapy).
This study aimed at assessing the prevalence, electrophysiologic characteristics, and mechanism of atypical atrioventricular nodal reentrant tachycardia (AVNRT).
We studied 925 consecutive patients ...with AVNRT. Atrial-His (AH) and His-atrial (HA) intervals were measured during atypical AVNRT (HA > 70 ms), and compared with measurements in 34 patients with typical (slow-fast) AVNRT. Assuming that conduction velocity over the fast pathway is similar in the anterograde and retrograde directions, the AH interval during the fast-slow form should be smaller than the HA during slow-fast. Atypical AVNRT was diagnosed in 59 patients (6.4%), median age 50 years (range 19-79 years), and 37 (59.7%) of them female. Fast-slow AVNRT was diagnosed in 44 patients (74.5%), and slow-slow AVNRT in 9 patients (15.2%). The remaining six patients (10.2%) could not be reliably classified due to inconsistent AH, and HA/AH patterns or variable intervals. Tachycardia induction with anterograde conduction jumps was seen in two patients with the fast-slow, and in three patients with slow-slow or intermediate forms. Atrial-His in the fast-slow group was significantly longer than HA in the slow-fast group, 99.7 ± 40.5 ms vs. 45.8 ± 7.7 ms, P < 0.001. Tachycardia cycle length was longer in fast-slow compared with slow-fast, 379.1 ± 68.5 ms vs. 317.1 ± 42.8 ms, P < 0.001.
Of AVNRT cases, 6.4% are atypical and may display patterns that do not necessarily correspond to the fast-slow or slow-slow conventional types. Atypical fast-slow and typical AVNRT do not appear to utilize the same limb for fast conduction.
The aim of this study was to assess whether small creatine kinase-MB isoenzyme (CK-MB) elevations after percutaneous coronary intervention (PCI) affect the subsequent mortality risk.
Several studies ...have evaluated the relationship of CK-MB levels after PCI with the subsequent risk of death. While there is consensus that elevations exceeding 5 times the upper limit of normal increase mortality significantly, there is uncertainty about the exact clinical impact of smaller CK-MB elevations.
We performed a meta-analysis of seven studies with CK-MB measurements and survival outcomes on 23,230 subjects who underwent PCI. Data were combined with random effects models.
Mean follow-up was 6 to 34 months per study. By random effects, 19% (95% confidence interval CI, 16% to 23%) had one- to five-fold CK-MB elevations, while only 6% (95% CI, 5% to 9%) had >5-fold elevations. Compared with subjects with normal CK-MB, there was a dose-response relationship with relative risks for death being 1.5 (95% CI, 1.2 to 1.8, no between-study heterogeneity) with one- to three-fold CK-MB elevations, 1.8 (95% CI, 1.4 to 2.4, no between-study heterogeneity) with three- to five-fold CK-MB elevations, and 3.1 (95% CI, 2.3 to 4.2, borderline between-study heterogeneity) with over five-fold CK-MB elevations (p < 0.001 for all).
Any increase in CK-MB after PCI is associated with a small, but statistically and clinically significant, increase in the subsequent risk of death.
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