Cardiovascular responses to low-level transcutaneous vagus nerve stimulation.

AIMS: The aim was to determine cardiovascular responses to an arbitrary protocol of transcutaneous low-level vagus nerve electrical stimulation (tVNS). METHODS: Study was performed in 15 male volunteers, mean age 23 years. Data were collected during two sessions - sham stimulation (no stimulation) and stimulation. Each session included one-hour resting phase followed by 15-min autonomic nervous system testing phase (Valsalva, deep breathing, wet-cold face tests), all in supine position. The right tragus stimulation parameters were: 20 Hz, constant current at sensation threshold, 1 ms rectangular pulse width. The ECG, noninvasive arterial blood pressure and thoracic impedance cardiography measurements were recorded and analyzed continuously with the Task Force® Monitor (CNSystems Medizintechnik GmbH, Graz, Ver. 2.2.10.0). t-Test for paired samples, paired Wilcoxon signed-rank, and one-way ANOVA for repeated measurements were carried out. P < 0.05 was considered significant. RESULTS: We demonstrated significant reductions of left ventricular contractility and output parameters, a trend for heart rate reduction, and resulting beneficial reduction of left ventricular work load. However, significant increases of blood pressure and total peripheral resistance were recognized, possibly as a reflex response. CONCLUSION: It seems that our tVNS protocol has a potential for cardiac autonomic modulation. This gives us opportunity to advance our stimulation parameters with participant-specific adjustments. Further studies are however needed to prove the therapeutic potential of such approach in different patient groups.

Low rate of atrial fibrillation recurrence verified by implantable loop recorder monitoring following a convergent epicardial and endocardial ablation of atrial fibrillation.

OBJECTIVE: Evaluate long-term outcomes in patients undergoing the Convergent procedure (CP) for the treatment of atrial fibrillation (AF). BACKGROUND: The CP provides a multidisciplinary approach, combining endoscopic creation of epicardial linear lesions followed by endocardial mapping and ablation and targets persistent and longstanding persistent AF patients who are at increased risk of heart failure, stroke, and mortality. METHODS: Outcomes from a prospective nonrandomized study were recorded for consecutive patients by interrogation of implanted Reveal monitors. Rhythm status and AF burden were quantified 6-24 months postprocedure, and compared relative to AF type, gender, age, body mass index, left atrial size, left ventricular ejection fraction, and congestive heart failure, hypertension, age >75 years, age between 65 and 74 years, stroke/TIA/TE, vascular disease (previous MI, peripheral arterial disease or aortic plaque), diabetes mellitus, female (CHA(2) DS(2) VASc). RESULTS: A total of 50 patients were enrolled with 94% having persistent or longstanding persistent AF. There were 2 atrioesophageal fistulas reported. In one patient, the fistula resulted in death at 33 days postprocedure; in the second, the fistula was surgically repaired but patient died 8 months postprocedure from a CVI. After CP, 95% of patients were in sinus rhythm at 6-month follow-up; 88% at 12 months; and 87% at 24 months. The median AF burden recorded with Reveal XT monitors was 0.0%, 0.1%, and 0.1% at 6, 12, and 24 months with 81%, 81%, and 87% of patients reporting a burden less than 3%, respectively. CONCLUSION: Using 24 × 7 continuous loop recording, the CP demonstrated success in treating persistent and longstanding persistent AF patients. Endocardial mapping and catheter ablation with diagnostic confirmation of procedural success complemented the endoscopic creation of epicardial linear lesions in restoring sinus rhythm.

Electrophysiology of anterograde right-atrial and left-atrial inputs to the atrioventricular node in patients with atrioventricular nodal re-entrant tachycardia.

AIMS: To study anterograde atrioventricular (A-V) nodal electrophysiological properties through the right-atrial (Ri) and left-atrial inputs (Li) under the pharmacological autonomic blockade (AUB) in patients with slow-fast A-V nodal re-entrant tachycardia (AVNRT) and in controls. METHODS AND RESULTS: Twenty-nine patients with slow-fast AVNRT and 15 control subjects were included. Programmed stimulation with single extrastimulus was performed from the right atrial appendage to test the Ri, and from the posterolateral coronary sinus to test the Li. The AUB was induced with intravenous atropine (0.04 mg/kg) and metoprolol (0.15 mg/kg). The A-V nodal conduction times, refractoriness, discontinuous conduction (≥ 40 ms atrial-His interval 'jump'), and inducibility of AVNRT or reciprocating beats were compared. The A-V nodal conduction times were longer: (i) through the Ri than Li, (ii) in patients than controls, and (iii) in baseline than after AUB--at slow rates in both groups and at fast rates in patients through the right input only (P < 0.05-0.001). A significantly longer slow pathway effective refractory period was demonstrated through the Li than the Ri in patients in baseline (P < 0.05). The discontinuous conduction was demonstrated 94 times in 25 of 29 (83%) patients and 15 times in 6 of 15 (40%) controls (P < 0.01), and was most frequently encountered with the Ri testing. Likewise, inducibility was manifested most frequently with the Ri testing (P = 0.08), and decreased after AUB during this testing only (P = 0.05). CONCLUSION: The inherent magnitude of discordance of A-V nodal conduction velocity, refractoriness, and parasympathetic modulation between the Ri and Li to the A-V node may play a role in the aetiology of AVNRT.