Idiopathic isolated fibrotic atrial cardiomyopathy underlies unexplained scar-related atrial tachycardia in younger patients.

Aims: Unexplained scar-related atrial tachycardia (AT) has been frequently encountered in clinical practice. We hypothesized that idiopathic, isolated fibrotic atrial cardiomyopathy (ACM) underlies this rhythm disorder. This study was aimed to characterize the underlying substrate and to explore the aetiology of this unexplained scar-related AT. Methods and results: Twenty-six (11 men, aged 46 ± 13 years) of 52 non-surgical scar-related AT patients identified by three-dimensional voltage mapping were enrolled in this prospective observational study. Multimodality image examinations (echocardiography, cardiac magnetic resonance, 99Tc single-photon emission computed tomography), ventricular voltage mapping, and intracardiac pressure curve recording ruled out ventricular involvement. Catheter ablation was acutely successful for all the patients, and pacemaker implantation was performed in seven patients who presented sinus node dysfunction or atrial standstill after termination of the AT. In three patients with multiple AT recurrences, the diseased areas of the right atrium were resected and dechannelled via mini-invasive surgical interventions. Histological examinations revealed profound fibrosis without amyloidosis or adipose deposition. Viral and familial investigations yielded negative results. Fibrosis progression over a median of 45 (5-109) months of follow-up manifested as atrial arrhythmia recurrence in seven patients and atrial lead non-capture due to newly developed atrial standstill in two patients. Two patients suffered four ischaemic stroke events before receiving anticoagulation treatment. Conclusion: Isolated, fibrotic ACM may underlie the idiopathic scar-related ATs. This novel cardiomyopathy has unique clinical characteristics with high morbidity including stroke and warrants specific therapeutic strategies. Further investigations are required to determine the aetiology and mechanism.

Safety and feasibility of chronic transvenous phrenic nerve stimulation for treatment of central sleep apnea in heart failure patients.

INTRODUCTION: Central sleep apnea (CSA) is common in patients with heart failure (HF) and is associated with poor quality of life and prognosis. Early acute studies using transvenous phrenic nerve stimulation (PNS) to treat CSA in HF have shown a significantly reduction of CSA and improvement of key polysomnographic parameters. In this study, we evaluated the safety of and efficiency chronic transvenous PNS with an implanted neurostimulator in HF patients with CSA. METHODS: This study was a prospective, nonrandomized evaluation of unilateral transvenous PNS in eight HF patients with CSA. The stimulation lead, which connected to a proprietary neurostimulator, was positioned in either the left pericardiophrenic or right brachiocephalic vein. Monitoring during implantation and 6-monthly follow-ups were performed. RESULTS: Six of the implanted eight patients completed the study (one was lost to follow-up; one died from pneumonia). Neither side effects nor adverse events related to stimulation occurred. During the 6-monthly follow-ups, one patient had a lead dislodgement in the first month and the lead was subsequently repositioned. No additional lead dislodgements occurred. There were no significant changes in sleep habits, appetite, bleeding or infections. Compared with the parameters before stimulator implantation, there were significant improvement in apnea-hypopnea index, central apnea index, left ventricular ejection fraction and 6-min walk distance (all P < 0.01). CONCLUSIONS: Use of chronic transvenous PNS appears to be safe and feasible in HF patients with CSA. Large multicenter studies are needed to confirm safety and efficacy in this population.

Prevention of postsurgical atrial tachycardia with a modified right atrial free wall incision.

BACKGROUND: Most postsurgical macroreentry atrial tachycardias (PS-MATs) are atriotomy related; however, underlying mechanisms and prevention remain undefined. OBJECTIVE: The purpose of the present study was to investigate the electrophysiological and histologic bases of right atriotomy incision arrhythmogenicity and whether a modified atriotomy that extends the incisional line to the tricuspid annulus (TA) and inferior vena cava (IVC) prevents PS-MAT. METHODS: Atrial arrhythmia induction and electrophysiological and histologic characteristics were studied 8 weeks after right atriotomy in 30 adult swine according to incision distance to TA or IVC (groups A, B, and C: broad, narrow, and closed corridors, respectively; group D, no-incision sham; n = 6 per group, except n = 12 for group B). RESULTS: Sustained PS-MATs were induced and mapped in the broad- and narrow-corridor groups (A, 1 of 6 [16.7%] vs B, 5 of 12 [41.7%]) but not in the closed-corridor (C) or sham (D) groups (P = .087). With 20-ms pacing cycle-length decrements (from 350 to 270 ms), mean conduction time over 20 mm at the atriotomy-to-TA corridor was 29.2 ± 2.2, 31.0 ± 4.2, 26.0 ± 1.9, and 17.0 ± 1.4 ms for 5 and 10 mm (both group B), 15 mm (group A), and sham incision (P = .017), respectively. Conduction properties correlated with histologic findings: the wider the corridor, the healthier its tissue. In group C (modified atriotomy), both corridors were replaced by dense scar with complete conduction block. CONCLUSION: Atriotomy corridor width determines conduction properties and contributes to arrhythmogenicity. A modified right atriotomy that extends to the TA and IVC prevents PS-MAT.

Electroacupuncture improves cardiac function and remodeling by inhibition of sympathoexcitation in chronic heart failure rats.

Chronic heart failure (CHF) is responsible for significant morbidity and mortality worldwide, mainly as a result of neurohumoral activation. Acupuncture has been used to treat a wide range of diseases and conditions. In this study, we investigated the effects of electroacupuncture (EA) on the sympathetic nerve activity, heart function, and remodeling in CHF rats after ligation of the left anterior descending coronary artery. CHF rats were randomly selected to EA and control groups for acute and chronic experiments. In the acute experiment, both the renal sympathetic nerve activity and cardiac sympathetic afferent reflex elicited by epicardial application of capsaicin were recorded. In the chronic experiment, we performed EA for 30 min once a day for 1 wk to test the long-term EA effects on heart function, remodeling, as well as infarct size in CHF rats. The results show EA significantly decreased the renal sympathetic nerve activity effectively, inhibited cardiac sympathetic afferent reflex, and lowered the blood pressure of CHF rats. Treating CHF rats with EA for 1 wk dramatically increased left ventricular ejection fraction and left ventricular fraction shortening, reversed the enlargement of left ventricular end-systolic dimension and left ventricular end-diastolic dimension, and shrunk the infarct size. In this experiment, we demonstrated EA attenuates sympathetic overactivity. Additionally, long-term EA improves cardiac function and remodeling and reduces infarct size in CHF rats. EA is a novel and potentially useful therapy for treating CHF.

Transvenous phrenic nerve stimulation in patients with Cheyne-Stokes respiration and congestive heart failure: a safety and proof-of-concept study.

BACKGROUND: Cheyne-Stokes respiration (CSR), which often occurs in patients with congestive heart failure (CHF), may be a predictor for poor outcome. Phrenic nerve stimulation (PNS) may interrupt CSR in patients with CHF. We report the clinical use of transvenous PNS in patients with CHF and CSR. METHODS: Nineteen patients with CHF and CSR were enrolled. A single stimulation lead was placed at the junction between the superior vena cava and brachiocephalic vein or in the left-side pericardiophrenic vein. PNS stimulation was performed using Eupnea System device (RespiCardia Inc). Respiratory properties were assessed before and during PNS. PNS was assessed at a maximum of 10 mA. RESULTS: Successful stimulation capture was achieved in 16 patients. Failure to capture occurred in three patients because of dislocation of leads. No adverse events were seen under maximum normal stimulation parameters for an overnight study. When PNS was applied following a series of central sleep apneic events, a trend toward stabilization of breathing and heart rate as well as improvement in oxygen saturation was seen. Compared with pre-PNS, during PNS there was a significant decrease in apnea-hypopnea index (33.8 ± 9.3 vs 8.1 ± 2.3, P = .00), an increase in mean and minimal oxygen saturation as measured by pulse oximetry (89.7% ± 1.6% vs 94.3% ± 0.9% and 80.3% ± 3.7% vs 88.5% ± 3.3%, respectively, all P = .00) and end-tidal CO2 (38.0 ± 4.3 mm Hg vs 40.3 ± 3.1 mm Hg, P = .02), but no significant difference in sleep efficiency (74.6% ± 4.1% vs 73.7% ± 5.4%, P = .36). CONCLUSIONS: The preliminary results showed that in a small group of patients with CHF and CSR, 1 night of unilateral transvenous PNS improved indices of CSR and was not associated with adverse events.