Outcomes of posterior wall isolation with pulmonary vein isolation for paroxysmal atrial fibrillation.

INTRODUCTION: Prior studies have shown that addition of posterior wall isolation (PWI) may reduce atrial fibrillation recurrence in patients with persistent atrial fibrillation. No data on PWI in paroxysmal AF (pAF) patients with normal left atrial voltage is available, to date. OBJECTIVE: This study sought to evaluate the efficacy of PWI in addition to pulmonary vein isolation (PVI) in patients presenting with pAF and normal left atrial voltage. METHODS: Consecutive patient registry analysis was performed on all patients with pAF and normal left atrial voltage undergoing initial radiofrequency ablation from November 1, 2018 to November 15, 2019. Primary endpoint was recurrence of atrial arrhythmia including AF, atrial tachycardia (AT), or atrial flutter (AFL). RESULTS: A total of 321 patients were studied, 214 in the PVI group and 107 in the PWI + PVI group. Recurrence of any atrial arrhythmia occurred in 18.2% of patients in the PVI group and 16.8% in the PVI + PWI cohort (p = 0.58). At 1 year, recurrence was 14.0% in the PVI group and 15.0% in the PWI + PVI group (p = 0.96). There was a lower AT/AFL recurrence in the PVI + PWI group, not reaching significance (3.7% in the PWI + PVI group vs. 7.9% in PVI group, p = 0.31). Need for carina lesions predicted recurrence in the PVI-only group. CONCLUSIONS: Addition of PWI to PVI in pAF patients undergoing their first ablation did not reduce the frequency of atrial arrhythmia recurrence. This warrants further study in a prospective trial.

Laser linewidth characterization via self-homodyne measurement under nearly-coherent conditions.

In this work we propose a novel and efficient characterization scheme for a narrow linewidth laser using a nearly-coherent delayed self-homodyne (NC-DSH) technique. The modulated signal of an analog coherent optics (ACO) transceiver, configured in optical loop-back, and the local oscillator (LO) are mixed after a very short optical path difference (OPD), corresponding to an interferometer operating in its nearly-coherent regime. The phase noise is extracted from a digital signal processing algorithm of carrier phase estimation (CPE), while data is transmitted. The interferometric pattern's E-field power spectral density (PSD) enables the extraction of the OPD and the linewidth of the transceiver's laser source in high accuracy. The proposed technique is demonstrated using a commercial integrated coherent transmitter and receiver optical sub-assembly (IC-TROSA).

Stealth and secured optical coherent transmission using a gain switched frequency comb and multi-homodyne coherent detection.

A novel all-optical stealth and secured transmission is proposed and demonstrated. Spectral replicas of the covert signal are carried by multiple tones of a gain switched optical frequency comb, optically coded with spectral phase mask, and concealed below EDFA's noise. The secured signal's spectrum is spread far beyond the bandwidth of a coherent receiver, thus forcing real time all-optical processing. An unauthorized user, who does not possess knowledge on the phase mask, can only obtain a noisy and distorted signal, that cannot be improved by post-processing. On the other hand, the authorized user decodes the signal using an inverse spectral phase mask and achieves a substantial optical processing gain via multi-homodyne coherent detection. A transmission of 20 Gbps under negative -7.5 dB OSNR is demonstrated here, yielding error-free detection by the eligible user.

Predicting Working Memory Capacity Based on Glutamatergic Concentration and its Modulation of Functional Connectivity.

Working memory (WM) capacity, the amount of information one can hold online in mind, has a central role in cognition. Previous electrophysiological and imaging studies revealed the pivotal role of persistent activity within parietal and frontal regions as the neural foundations underpinning WM capacity. The best candidate molecules determining persistent activity are the brain's major excitatory and inhibitory neurotransmitters, glutamate and gamma-aminobutyric acid (GABA), respectively. However, our knowledge of these neurophysiological determinants in forming WM capacity is still poor. Using magnetic resonance spectroscopy (MRS), we examined the contribution of glutamate and GABA within the left intraparietal sulcus (IPS) and the left inferior/middle frontal gyrus (FG) in tracking WM capacity. A positive association was found between glutamate within the left IPS and WM capacity. By utilising resting-state functional MRI, we identified a negative association between parieto-cingulate connectivity and WM capacity. Individual variation in parieto-cingulate connectivity was explained by glutamatergic concentration in the IPS. Moreover, we found that parieto-cingulate connectivity mediated the relationship between interparietal sulcus glutamate and WM capacity. This set of findings reveals a novel mechanistic insight by which glutamatergic concentration within the IPS shapes WM capacity via parieto-cingulate connectivity.

QT interval dynamics and triggers for QT prolongation immediately following cardiac arrest.

BACKGROUND: The prolongation in QT interval typically observed following cardiac arrest is considered to be multifactorial and induced by external triggers such as hypothermia therapy and exposure to antiarrhythmic medications. OBJECTIVE: To evaluate the corrected QT interval (QTc) dynamics in the first 10 days following cardiac arrest with respect to the etiology of arrest, hypothermia and QT prolonging medications. METHODS: We enrolled 104 adult survivors of cardiac arrest, where daily ECG was available for at least 3 days. We followed their QT and QRS intervals for the first 10 days of hospitalization. We used both Bazett and Fridericia formulas to correct for heart rate. For patients with QRS < 120 we analyzed the QTc interval (n = 90) and for patients with QRS > 120 ms we analyzed the JTc (n = 104) vs. including only the narrow QRS samples (n = 89). We stratified patients by 3 groups: (1) presence of ischemic heart disease (IHD) (2) treatment with hypothermia protocol, and (3) treatment with QTc prolonging medications. Additionally, genetic information obtained during hospitalization was analyzed. RESULTS: QTc and JTc intervals were significantly prolonged in the first 6 days. Maximal QTc/JTc prolongation was observed in day 2 (QTcB = 497 ± 55). There were no differences in daily QTc/JTc and QRS intervals in the first 2 days post arrest between patients with or without hypothermia induction but such difference was found with QT prolonging medications. All subgroups demonstrated significantly prolonged QTc/JTc interval regardless of the presence of IHD, hypothermia protocol or QTc prolonging medication exposure. Our results were consistent for both Bazetts' and Frediricia correction and for any QRS duration. Prolongation of the JTcB beyond 382 ms after day 3 predicted sustained QTc/JTc prolongation beyond day 6 with an ROC of 0.78. CONCLUSIONS: QTc/JTc interval is significantly and independently prolonged post SCA, regardless of known QT prolonging triggers. Normalization of the QTc post cardiac arrest should be expected only after day 6 of hospitalization. Assessment of the QTc for adjudication of the etiology of arrest or for monitoring the effect of QT prolonging medications may be unreliable.

Electrocardiographic Risk Stratification in COVID-19 Patients.

Background: The COVID-19 pandemic has resulted in worldwide morbidity at unprecedented scale. Troponin elevation is a frequent laboratory finding in hospitalized patients with the disease, and may reflect direct vascular injury or non-specific supply-demand imbalance. In this work, we assessed the correlation between different ranges of Troponin elevation, Electrocardiographic (ECG) abnormalities, and mortality. Methods: We retrospectively studied 204 consecutive patients hospitalized at NYU Langone Health with COVID-19. Serial ECG tracings were evaluated in conjunction with laboratory data including Troponin. Mortality was analyzed in respect to the degree of Troponin elevation and the presence of ECG changes including ST elevation, ST depression or T wave inversion. Results: Mortality increased in parallel with increase in Troponin elevation groups and reached 60% when Troponin was >1 ng/ml. In patients with mild Troponin rise (0.05-1.00 ng/ml) the presence of ECG abnormality and particularly T wave inversions resulted in significantly greater mortality. Conclusion: ECG repolarization abnormalities may represent a marker of clinical severity in patients with mild elevation in Troponin values. This finding can be used to enhance risk stratification in patients hospitalized with COVID-19.

QT interval prolongation and torsade de pointes in patients with COVID-19 treated with hydroxychloroquine/azithromycin.

Background: There is no known effective therapy for patients with coronavirus disease 2019 (COVID-19). Initial reports suggesting the potential benefit of hydroxychloroquine/azithromycin (HY/AZ) have resulted in massive adoption of this combination worldwide. However, while the true efficacy of this regimen is unknown, initial reports have raised concerns about the potential risk of QT interval prolongation and induction of torsade de pointes (TdP). Objective: The purpose of this study was to assess the change in corrected QT (QTc) interval and arrhythmic events in patients with COVID-19 treated with HY/AZ. Methods: This is a retrospective study of 251 patients from 2 centers who were diagnosed with COVID-19 and treated with HY/AZ. We reviewed electrocardiographic tracings from baseline and until 3 days after the completion of therapy to determine the progression of QTc interval and the incidence of arrhythmia and mortality. Results: The QTc interval prolonged in parallel with increasing drug exposure and incompletely shortened after its completion. Extreme new QTc interval prolongation to >500 ms, a known marker of high risk of TdP, had developed in 23% of patients. One patient developed polymorphic ventricular tachycardia suspected as TdP, requiring emergent cardioversion. Seven patients required premature termination of therapy. The baseline QTc interval of patients exhibiting extreme QTc interval prolongation was normal. Conclusion: The combination of HY/AZ significantly prolongs the QTc interval in patients with COVID-19. This prolongation may be responsible for life-threatening arrhythmia in the form of TdP. This risk mandates careful consideration of HY/AZ therapy in light of its unproven efficacy. Strict QTc interval monitoring should be performed if the regimen is given.

Implicit death primes increase alcohol consumption.

OBJECTIVE: The authors examined whether priming thoughts of death are associated with increases in alcohol consumption. METHOD: Research assistants handed out fliers that were stacked in a random order to pedestrians walking through campus (N = 377). These fliers served to remind them of either their death or of an aversive condition unrelated to death (severe back pain), which served as the control. Then they were solicited to purchase an alcoholic or nonalcoholic beverage. RESULTS: The authors used a 2 × 2 log-linear analysis, with type of prime (death-pain) and beverage type (alcoholic-nonalcoholic) as the independent variables and consumption (yes-no) as the outcome measure (11.9% of the total sample consumed a beverage). RESULTS revealed that a greater percentage of students who received the death prime consumed alcohol (36.59%) versus students in the pain prime condition (8.94%), G²(4, N = 377) = 64.8, p < .001, W = .41. The type of prime (death-pain) did not influence the consumption of nonalcoholic beverages. CONCLUSION: The current research indicates that death-related concerns may play a role in increasing the consumption of alcoholic beverages.