Venus steep-sided domes: Relationships between geological associations and possible petrogenetic models

Venus domes are characterized by steep sides, a circular shape, and a relatively flat summit area. In addition, they are orders of magnitude larger in volume and have a lower height/diameter ratio than terrestrial silicic lava domes. The morphology of the domes is consistent with formation by lava with a high apparent viscosity. Twenty percent of the domes are located in or near tessera (highly deformed highlands), while most other (62 percent) are located in and near coronae (circular deformational features thought to represent local mantle upwelling). These geological associations provide evidence for mechanisms of petrogenesis and several of these models are found to be plausible: remelting of basaltic or evolved crust, differentiation of basaltic melts, and volatile enhancement and eruption of basaltic foams. Hess and Head have shown that the full range of magma compositions existing on the Earth is plausible under various environmental conditions on Venus. Most of the Venera and Vego lander compostional data are consistent with tholeiitic basalt; however, evidence for evolved magmas was provided by Venera 8 data consistent with a quartz monzonite composition. Pieters et al. have examined the color of the Venus surface from Venera lander images and interpret the surface there to be oxidized. Preliminary modeling of dome growth has provided some interpretations of lava rheology. Viscosity values obtained from these models range from 10(exp 14) - 10(exp 17) pa*s, and the yield strength has been calculated to be between 10(exp 4) and 10(exp 6) Pa, consistent with terrestrial silicic rocks. The apparent high viscosity of the dome lavas suggests that the domes have a silicic composition or must augment their viscosity with increased visicularity or crystal content. Sixty-two percent of the Venus domes are associated with coronae, circular features that have been proposed as sites of mantle upwelling, and 20 percent of the domes are located near tessera, relatively high areas of complex deformed terrain. We have investigated several models that are consistent with these geologic associations. The first case involves the differentiation of basalt in a magma reservoir in the crust, perhaps produced by partial melting within a mantle plume. The second case is melting at the base of thickened basaltic crust, and the final case is volatile exsolution and enhancement within a basaltic magma reservoir. The association of domes with tessera might be explained by crustal remelting, while the association with coronae may be consistent with chemical differentiation of a magma reservoir or the exsolution and concentration of volatiles in the reservoir before eruption

Validation of a Novel, Non-Invasive System for Autonomic Profiling in Healthy Volunteers

Noninvasive profiling of the autonomic nervous system has been shown to have prognostic value in patients with myocardial infarction, CHF and diabetes. The ANSAR system (ANX 3.0, Philadelphia, PA) is a new commercially available system that utilizes respiratory rate, HR and BP to assess on-going sympathovagal modulation during various maneuvers known to evoke autonomic perturbations. Instead of using conventional Fast Fourier Transform for frequency domain analysis, a Continuous Wavelet Transform (CWT) is used to generate numerical and graphical data. The system calculates Low Frequency Area (LFA, analogous to LF Power) and Respiratory Frequency Area (RFA, analogous to High Frequency Power.) A time domain index (pNN50 is also calculated

Evaluation of Ventricular Repolarization in Patients Undergoing Cardiac Resynchronization Therapy (CRT) Using Two Modalities: Conventional Biventricular Pacing vs. His-Bundle Pacing

Introduction: Permanent His-bundle pacing (HBP) is being used as an alternative to biventricular pacing (BiVP) for CRT. HBP preserves the physiologic pattern of ventricular activation and markedly reduces ventricular dyssynchrony. While ventricular depolarization with HBP vs. BiVP has been studied, the effects of the 2 modalities on repolarization have not been compared. The purpose of this study was to compare ventricular repolarization in patients with HBP and BiVP. We hypothesize that HBP provides more physiologic repolarization as compared to BiVP. Methods: ECG repolarization parameters were analyzed in patients who underwent HBP and BiVP using the first available ECG post implant. Parameters included: 1) T Peak – T End (Tp-TeApical): Tp-Te in lead V5, and if not measurable, then in V4/V6 2) Tp-TeTotal: Earliest T peak to the latest T end across all precordial leads 3) T Peak Dispersion: Absolute difference between the earliest and latest T peaks across all precordial leads. Data was compared using a two-tailed unequal variance Student’s t-test. Results: Data from 23 HBP patients and 23 BiVP patients was analyzed. The average HBP Tp-TeApical of 74 ± 7ms was less than the BiVP Tp-TeApical of 112 ± 15ms (p\u3c0.01). Similarly, average HBP Tp-TeTotal of 106 ± 11ms was smaller than the BiVP Tp-TeTotal of 145 ± 17ms (p\u3c0.01). The difference between Tpeak dispersion between the two groups was not significant. Conclusion: Tp-Te interval, a known measure of dispersion of repolarization and marker of arrhythmic risk, is more physiologic (lower) with HBP as compared to BiVP. These data suggest that in addition to physiologic depolarization, HBP also provides physiologic repolarization and potentially lower arrhythmic risk compared to BiVP

MK-0448, a Specific Kv1.5 Inhibitor: Safety, Pharmacokinetics and Pharmacodynamic Electrophysiology in Experimental Animal Models and in Humans.

BACKGROUND: -We evaluated the viability of I(Kur) as a target for maintenance of sinus rhythm in patients with a history of atrial fibrillation through the testing of MK-0448, a novel I(Kur) inhibitor. METHODS AND RESULTS: -In vitro MK-0448 studies demonstrated strong inhibition of I(Kur) with minimal off-target activity. In vivo MK-0448 studies in normal anesthetized dogs demonstrated significant prolongation of the atrial refractory period compared with vehicle controls without affecting the ventricular refractory period. In studies of a conscious dog heart failure model, sustained AF was terminated with bolus intravenous MK-0448 doses of 0.03 and 0.1 mg/kg. These data led to a two-part first-in-human study: Part I evaluated safety and pharmacokinetics, and Part II was an invasive electrophysiologic (EP) study in healthy subjects. MK-0448 was well-tolerated with mild adverse experiences, most commonly irritation at the injection site. During the EP study, ascending doses of MK-0448 were administered, but no increases in atrial or ventricular refractoriness were detected despite achieving plasma concentrations in excess of 2 μM. Follow-up studies in normal anesthetized dogs designed to assess the influence of autonomic tone demonstrated that prolongation of atrial refractoriness with MK-0448 was markedly attenuated in the presence of vagal nerve simulation, suggesting that the effects of I(Kur) blockade on atrial repolarization may be negated by enhanced parasympathetic neural tone. CONCLUSIONS: -The contribution of I(Kur) to human atrial electrophysiology is less prominent than in preclinical models and therefore is likely to be of limited therapeutic value for the prevention of atrial fibrillation

Serendipitous Supernormality

We describe a patient who underwent AV node modification to create complete heart block in the setting of incessant, ablation-and-drug-refractory, symptomatic atypical atrial flutter. His dual chamber defibrillator (previously implanted for resuscitated cardiac arrest) was programmed to the VVIR mode at a faster pacing rate of 85 bpm. Serendipitously, this rate was an almost exact factorial of his flutter rate of 250-260 bpm. This resulted in every 6th flutter wave falling in the supernormal period, resulting in fixed-coupled supraventricular bigeminy and trigeminy in the setting of complete heart block. Reprogramming the pacing rate to 75 bpm abolished bigeminy and trigeminy

Cryo vs RF p-wave Characteristics Comparative Analysis

Introduction: Atrial fibrillation (AF) is the leading cause of stroke. Patients with drug-refractory AF are managed with Radiofrequency (RF) or Cryoballoon (Cryo) pulmonary vein isolation (PVI). Approximately 30% of PVIs result in AF recurrences. There is clinical utility in identifying patients at higher risk of AF recurrence with readily available ECG parameters. Methods: This retrospective study analyzed the ECG characteristics and AF recurrence of 86 paroxysmal AF patients who underwent PVI. Baseline characteristics were collected by chart review and p-wave parameters were measured with electronic calipers in the MUSE (GE) ECG database. AF recurrence was defined as any documented atrial tachyarrhythmia. Statistical analyses performed in SPSS included t-tests and ROC curves to compare group means and to select parameter cutoffs to predict AF recurrence, respectively. Results: There were no differences in % AF recurrences (Cryo: 26% vs RF: 37%; P = 0.25) or Dp-wave parameters (pre-PVI values - post-PVI values) except for DPwD(III) (Cryo: 11ms vs RF: -3ms; P = 0.023). Patients with AF recurrences had greater CHA2DS2-VASc scores (P = 0.014), Left atrial volume (P = 0.031), Pre-PR-intervals (P = 0.006), Pre-PwD(III) (P = 0.013), Pre-PwD(V1) (P = 0.001), Pre-PwD(V2) (P = 0.02), Pre-PwD-terminal (P = 0.0002), Post-PR-intervals (P = 0.038), Post-PwD(III) (P = 0.002), and Post-PwD(aVF) (P = 0.009). Patients whose p-wave duration (PwD) increased in V1 were less likely to have a recurrence (P = 0.01). Pre-PwD(V1) \u3e 120ms yielded a sensitivity of 68.4% and specificity of 67.6% for predicting AF recurrence. Discussion: Cryo is non-inferior to RF regarding AF recurrence. This finding is further supported by similar PVI-induced Dp-wave parameters between the two modalities. Pre-PwD(V1), along with other parameters can be used in combination to reasonable predict recurrence and to guide clinical management of AF

Safety of Adenosine for the Treatment of Supraventricular Tachycardia in Hospitalized Patients with COVID-19 Pneumonia

Coronavirus disease 2019 (COVID-19) is associated with pulmonary involvement and cardiac arrhythmias, including supraventricular tachycardia (SVT). Adenosine is commonly used to treat SVT and is generally safe, but is rarely associated with bronchospasm. There are no data regarding the safety of adenosine use in patients with COVID-19 pneumonia and physicians may hesitate to use it in such patients. We surveyed resident physicians and cardiology attendings regarding their level of comfort in administering adenosine to hospitalized COVID-19 patients. We compared a study group of 42 COVID-19 hospitalized patients who received adenosine for SVT to a matched (for age, sex, and co-morbidities) control group of 42 non-COVID-19 hospitalized patients during the same period, all of whom received IV adenosine for SVT. Escalation of care following intravenous adenosine administration was defined as increased/new pressor requirement, need for higher O2 flow rates, need for endotracheal intubation, new nebulizer therapy, or transfer to intensive care unit within 2 h of adenosine administration. Survey results showed that 82% (59/72) of residents and 62% (16/26) of cardiologists expressed hesitation/significant concerns regarding administering adenosine in hospitalized COVID-19 patients. Adenosine use was associated with escalation of care in 47.6% (20/42) COVID-19 as compared to 50% (21/42) non-COVID-19 patients (odds ratio 0.95, 95% CI 0.45-2.01, p = NS). Escalation of care was more likely in patients who were on higher FiO2, on prior nebulizer therapy, required supplemental oxygen, or were already on a ventilator. In conclusion, we identified significant hesitation among physicians regarding the use of adenosine for SVT in hospitalized COVID-19 patients. In this study, there was no evidence of increased harm from administering adenosine to patients with SVT and COVID-19. This finding needs to be confirmed in larger studies. Based on the current evidence, adenosine for treatment of SVT in this setting should not be avoided. Key Points: Question: Given the known bronchospastic effects of adenosine, is the use of adenosine safe for treatment of supraventricular tachycardia in hospitalized patients with COVID-19? Findings: A survey of residents and cardiology attending identified that a majority expressed some level of apprehension in using adenosine for SVT in COVID-19 patients. In our matched cohort study, we found adenosine use to be comparably safe in COVID-19 and non-COVID-19 hospitalized patients. Meaning: Based on current evidence, adenosine for treatment of SVT in this setting should not be avoided

A Shock to the Heart? A Case of Phantom Shocks in a Patient with Brugada Syndrome

Brugada syndrome is an inherited condition characterized by an increased risk of sudden cardiac death (SCD) secondary to lethal ventricular arrhythmias occurring most often in the fourth decade of life. Implantable cardioverter-defibrillators (ICDs) are recommended in patients who have documented ventricular tachycardia (VT) or ventricular fibrillation (VF) and in patients presenting with a spontaneous type 1 Brugada pattern on electrocardiogram (ECG) and a history of arrhythmic-sounding syncope.1 However, patients with ICDs are at risk of developing “phantom shocks” which occur when a patient reports the sensation of receiving a shock that is not confirmed upon subsequent device interrogation.2 One retrospective study of 38 patients demonstrated that patients who reported phantom shocks had a higher prevalence of documented depression, anxiety and substance use and that patients who had previous ICD shocks for “arrhythmia storm” were more likely to experience phantom shocks.3 Prior studies have described the increased incidence of anxiety and decreased quality of life in patients diagnosed with Brugada syndrome alone with some patients developing post-traumatic stress disorder (PTSD).4 We present a case of a patient with previously diagnosed Brugada syndrome who suffered from phantom shocks after a defibrillation event. This case highlights the importance of recognizing phantom shocks for improving patient outcomes, to provide a multidisciplinary approach and to optimize both cardiac and psychological well-being of these patients

A Shocking Case of Far-Field Atrial Oversensing in Giant-Cell Myocarditis

We report a unique case of delivery of inappropriate implantable cardioverter-defibrillator therapies related to a “perfect storm”: presence of an integrated lead, insufficient lead slack related to right heart dilation resulting in shock coil misplacement, myocarditis with loss of R waves, and the concomitant occurrence of an incessant atrial tachycardia. (Level of Difficulty: Advanced.

The Pulmonary Venous Ridge Length to Stratify Stroke Risk in Atrial Fibrillation

Purpose of Study: To evaluate the left superior pulmonary venous ridge length (RL) and the left atrial appendage fractal dimension (LAA FD) as predictors of cardioembolic ischemic stroke (CVA) and transient ischemic attack (TIA) in patients with atrial fibrillation (AF). Materials, Methods and Procedures: A multicenter, retrospective multicenter study was conducted on patients with AF who underwent cardiac CT prior to catheter ablation between 01/01/2010 and 12/31/2015. Patients were grouped by the presence or absence of prior CVA/TIA. Patients with mitral stenosis, prior mechanical aortic valve replacement, ascending aortic arch atheroma, highrisk patent foramen ovale, history of atrial septal repair or device, preexisting LAA thrombus or intra-cardiac tumor, or prior open-heart surgery were excluded. Further exclusion was performed for patients with sub-optimal or unavailable cardiac CT imaging by investigators blinded to clinical data. Blinded investigators obtained RL by measuring the distance between the left superior pulmonary venous ostium and the internal ostium of the left atrial appendage. LAA FD was calculated using semi-automated volume rendering and processing software (ImageJ, Bethesda, MD) [1] and LAA FD are presented as means (95% confidence interval) and were compared between groups using unpaired t-tests. Logistic regression analysis was used to construct receiver operating curves and to assess the abilities of RL and LAA FD to predict prior CVA/TIA. Results: 225 patients met inclusion criteria. Mean RL were 4.32 (3.80-4.93) and 5.20 (4.93-5.48) for patients with (n=24; mean age: 59.4; 70.8% male) and without (n=165; mean age: 59.3; 75.4% male) prior CVA/TIA, respectively(p=0.033). Mean LAA FD were 2.29 (95% CI: 2.24-2.34) and 2.33 (2.32-2.34) for patients with (n=22; mean age: 60.3; 68.2% male) and without (n=171; mean age: 59.3; 74.9% male) prior CVA/TIA, respectively (p=0.052). In a regression model including LAA FD, RL, and established predictive markers, only RL predicted prior CVA/TIA (OR 0.73; 0.54 to 0.98; p=0.034). Discussion: Lower RL values were associated with prior CVA/TIA, whereas LAA FD values were similar between patients with AF with and without prior CVA/TIA. RL is a novel marker that may refine clinical decision-making regarding anticoagulation goals and treatment decisions for patients with AF. Future studies with larger samples should investigate the clinical utility of RL to improve CVA/TIA risk stratification of patients with AF and prospectively reduce the incidence of CVA/TIA in this population