Retreating blade stall control on a NACA 0015 aerofoil by means of a trailing edge flap

Trailing edge flaps may provide a mechanism for alleviating retreating blade stall. In the present investigation numerical simulations were conducted involving a NACA 0015 aerofoil section fitted with a plain trailing edge (TE) flap. All simulations were conducted using DIVEX, a tool being developed at the University of Glasgow, Department of Aerospace Engineering. In summary, the code uses a surface shedding discrete vortex method (DVM) for the simulation of 2-D incompressible flows around pitching aerofoils. The aero-foil is oscillating in pitch about its quarter chord axis and the clap undergoes negative pitch inputs, i.e. upward. An interesting feature appears to be that the cause of the severe nose down pitching movement introduced during dynamic stall is due to the cortical pair of the DSV and TEV where it is shown that the former feeds the latte in the case of the clean aerofoil for the range of reduced frequencies varying between k = 0.128 and k = 0.180. This fact suggests that manipulation of the vorticity in the vicinity of the trailing edge may be a mechanism for modification of the dynamic stall vortex (DSV) trajectory. This was found to relieve the aerofoil from severe pitching moment undershoot occurring during dynamic stall under appropriately phased flap actuations. Results obtained so far encourage the employment of a flap with fairly small size, 15% of the aerofoil chord. A parametric study is described which identifies the proper aerodynamic and actuation parameters for the current problem. In addition a simple open loop control scheme is developed based purely on rotor and flap related quantities

Typical Atrial Flutter Ablation: Demonstration of Cavo-Tricuspid Isthmus Block Aided by a Halo Catheter

A 61-year-old gentleman with one-year history of atrial flutter (see typical saw-tooth appearance of flutter –F waves in the inferior ECG leads in Panel A) refractory to antiarrhythmic agents was submitted to cavotricuspid isthmus ablation. During the procedure, use of an eicosapolar halo catheter (Panel B, arrow) helped to demonstrate the counterclockwise direction of activation (from proximal pole pairs Halo 10 toward Halo 1, Panel D). Upon completion of the ablation line along the isthmus, conversion of atrial flutter into sinus rhythm was noted (Panel C, arrow). With the aid of the halo catheter, bidirectional block could be easily determined by pacing near the coronary sinus os (Panel E, arrow) and recording the late activation of Halo 1, which was withdrawn to the lateral wall of the low right atrium, and finally pacing at the low lateral wall (Panel F, arrow) and recording late activation by the catheter near the coronary sinus os... (excerpt

Pathophysiology of Resistant Hypertension: The Role of Sympathetic Nervous System

Resistant hypertension (RH) is a powerful risk factor for cardiovascular morbidity and mortality. Among the characteristics of patients with RH, obesity, obstructive sleep apnea, and aldosterone excess are covering a great area of the mosaic of RH phenotype. Increased sympathetic nervous system (SNS) activity is present in all these underlying conditions, supporting its crucial role in the pathophysiology of antihypertensive treatment resistance. Current clinical and experimental knowledge points towards an impact of several factors on SNS activation, namely, insulin resistance, adipokines, endothelial dysfunction, cyclic intermittent hypoxaemia, aldosterone effects on central nervous system, chemoreceptors, and baroreceptors dysregulation. The further investigation and understanding of the mechanisms leading to SNS activation could reveal novel therapeutic targets and expand our treatment options in the challenging management of RH

Ablation Techniques in a Patient with a Right Accessory Pulmonary Vein. Is it Always Feasible?

A 32-year-old woman with lone paroxysmal atrial fibrillation had two pulmomary vein isolation procedures over 1 year, by means of the circular multipolar duty-cycled radiofrequency PVAC in the first and the Thermocool® SmartTouchTM catheter in the second procedure. Following both procedures, the patient remained highly symptomatic on a weekly to monthly basis and a third procedure by using the second generation of cryoballoon Arctic Front AdvanceTM. Right inferior pulmonary vein was completely reconnected and an extreme hockey stick configuration was necessary in order to achieve complete occlusion and isolation. Thirty months later the patient remains symptom free in the absence of any therapy

Ablation Techniques in a Patient with a Right Accessory Pulmonary Vein. Is it Always Feasible?

A 32-year-old woman with lone paroxysmal atrial fibrillation had two pulmomary vein isolation procedures over 1 year, by means of the circular multipolar duty-cycled radiofrequency PVAC catheter in the first and the Thermocool® SmartTouchTM catheter in the second procedure. Following both procedures, the patient remained highly symptomatic on a weekly to monthly basis and a third procedure was performed by using the second generation of cryoballoon Arctic Front AdvanceTM. Right inferior pulmonary vein was completely reconnected and an extreme hockey stick configuration was necessary in order to achieve complete occlusion and isolation. Thirty months later the patient remains symptom free in the absence of any therapy. Rhythmos 2016;11(4):96-97

Redo Ventricular Tachycardia Ablation in a Frail Patient with Ischemic Cardiomyopathy. Benefit of Survival versus Risk of Complications

We present a case of repeated successful ventricular tachycardia ablation in an elderly frail post-myocardial infarction patient who presented with recurrent and often incessant episodes of slow ventricular tachycardia. An 85-year old thin male was presented with a hemodynamically stable, slow ventricular tachycardia, temporarily terminated after multiple anti-tachycardia pacing attempts. A previous recent ventricular tachycardia ablation procedure due to multiple ICD activations yielded poor result. Identification and elimination of late potentials was accompanied by final non-inducibility and a free from ventricular tachycardia mid-term outcome

Doppler tissue imaging unmasks right ventricular function abnormalities in HIV-infected patients

Background: We sought to investigate right ventricular (RV) function with Doppler tissue imaging (DTI) in human immunodeficiency virus (HIV)-infected patients receiving highly-active antiretroviral treatment, without any heart-related symptoms. Methods: We studied 38 asymptomatic HIV patients (aged 44.5 ± 9.2 years, 22 of them men) and 25 age-matched and sex-matched controls. All subjects underwent conventional and DTI estimation of left ventricular (LV) systolic and diastolic function, measuring peak systolic and diastolic myocardial velocities at the mitral annulus (Sm, Em, Am). Two-dimensional (2-D) echocardiographic study of the right ventricle (RV) was performed from the four-chamber view, and RV end-diastolic dimensions were measured. DTI recordings from the RV free wall at the tricuspid annulus were used to determine systolic (SmRV) and diastolic function (EmRV and AmRV). Results: HIV-infected patients compared to controls exhibited significantly lower peak systolic velocities at the septal-SmIVS (7.9 ± 1.3 vs 9.1 ± 1.4 cm/s, p = 0.002) and lateral mitral annulus - SmLAT (9.8 ± 1.7 vs 11.2 ± 1.3 cm/s, p = 0.025); no difference was observed regarding conventional 2-D examination of LV systolic and diastolic function and DTI-derived Em and Am. No significant difference occurred between HIV patients and controls regarding RV end-diastolic dimensions and pulmonary artery systolic pressure. However, SmRV (13.8 ± 1.6 vs 14.9 ± 2.2 cm/s, p = 0.040), EmRV (11.6 ± 3 vs 13.5 ± 2.6 cm/s, p = 0.028) and AmRV (10.9 ± 2.5 vs 13.8 ± 4 cm/s, p = 0.003) were significantly reduced in HIV patients as compared to controls. Conclusions: DTI unmasks subtle and otherwise undetectable abnormalities of the longitudinal LV systolic function and both RV systolic and diastolic function, in asymptomatic HIV patients receiving highly-active antiretroviral treatment. (Cardiol J 2010; 17, 6: 587-593

Cardiac Resynchronization Therapy and Proarrhythmia: Weathering the Storm

In patients with significant left ventricular (LV) dysfunction and congestive heart failure despite optimal medical therapy, implantation of cardiac resynchronization therapy-defibrillator (CRT-D) devices has been shown to improve symptoms and diminish ventricular tachyarrhythmia susceptibility.We describe the case of a patient with dilated cardiomyopathy who developed ventricular tachycardia storm (VTS) one month after the implantation of a CRT-D device. VTS was initially controlled with pharmacotherapy, allowing the patient to continue with biventricular pacing. Two months later the patient was readmitted due to multiple episodes of polymorphic ventricular tachycardia. VTS was refractory to various intravenous antiarrhythmic drugs and it was finally controlled only when LV pacing was turned off.In patients with heart failure treated with CRT-D, VTS can occur and is best managed by turning off LV pacing. Our report raises an important and concerning issue of biventricular pacing causing ‘proarrhythmia’ in rare instances