Monetization in online streaming platforms: an exploration of inequalities in Twitch.tv.

The live streaming platform Twitch underwent in recent years an impressive growth in terms of viewership and content diversity. The platform has been the object of several studies showcasing how streamers monetize their content via a peculiar system centered around para-sociality and community dynamics. Nonetheless, due to scarcity of data, lots is still unknown about the platform-wide relevance of this explanation as well as its effect on inequalities across streamers. In this paper, thanks to the recent availability of data showcasing the top 10,000 streamers revenue between 2019 and 2021, as well as viewership data from different sources, we characterized the popularity and audience monetization dynamics of the platform. Using methods from social physics and econometrics, we analyzed audience building and retention dynamics and linked them to observed inequalities. We found a high level of inequality across the platform, as well as an ability of top streamers to diversify their revenue sources, through audience renewal and diversification in monetization systems. Our results demonstrate that, even if the platform design and affordance favor monetization for smaller creators catering to specific niches, its non-algorithmic design still leaves room for classical choice biases allowing a few streamers to emerge, retain and renew a massive audience.

Stiff knots.

We report on the geometry and mechanics of knotted stiff strings. We discuss both closed and open knots. Our two main results are that (i) their equilibrium energy as well as the equilibrium tension for open knots depends on the type of knot as the square of the bridge number and (ii) braid localization is found to be a general feature of stiff string entanglements, while angle and knot localizations are forbidden. Moreover, we identify a family of knots for which the equilibrium shape is a circular braid. Two other equilibrium shapes are found from Monte Carlo simulations. These three shapes are confirmed by rudimentary experiments. Our approach is also extended to the problem of the minimization of the length of a knotted string with a maximum allowed curvature.

Limited posterior left atrial cryoablation in patients with chronic atrial fibrillation undergoing valvular heart sugery.

OBJECTIVES: We sought to evaluate whether a limited surgical cryoablation of the posterior region of the left atrium was safe and effective in the cure of atrial fibrillation (AF) in patients with associated valvular heart disease. BACKGROUND: Extensive surgical ablation of AF is a complex and risky procedure. The posterior region of the left atrium seems to be important in the initiation and maintenance of AF. METHODS: In 32 patients with chronic AF who underwent heart valve surgery, linear cryolesions connecting the four pulmonary veins and the posterior mitral annulus were performed. Eighteen patients with AF who underwent valvular surgery but refused cryoablation were considered as the control group. RESULTS: Sinus rhythm (SR) was restored in 25 (78%) of 32 patients immediately after the operation. The cryoablation procedure required 20 +/- 4 min. There were no intraoperative and perioperative complications. During the hospital period, one patient died of septicemia. Thirty-one patients reached a minimum of nine months of follow-up. Two deaths occurred but were unrelated to the procedure. Twenty (69%) of 29 patients remained in SR with cryoablation alone, and 26 (90%) of 29 patients with cryoablation, drugs and radiofrequency ablation. Three (10%) of 29 patients remained in chronic AF. Right and left atrial contractility was evident in 24 (92%) of 26 patients in SR. In control group, two deaths occurred, and SR was present in only four (25%) of 16 patients. CONCLUSIONS: Linear cryoablation with lesions connecting the four pulmonary veins and the mitral annulus is effective in restoration and maintenance of SR in patients with heart valve disease and chronic AF. Limited left atrial cryoablation may represent a valid alternative to the maze procedure, reducing myocardial ischemic time and risk of bleeding.

The Marfan syndrome: surgical technique and follow-up in 50 patients.

Fifty patients with Marfan's syndrome underwent operation at the National Heart Hospital because of cardiovascular complications. Forty-six had an aneurysm of the ascending aorta, 13 had chronic dissection, and 6 had acute dissection of the aortic wall. Forty-three aortic valves were incompetent, and five were stenotic and incompetent. One mitral valve had minor regurgitation. The Starr-Edwards prosthesis was used in 36 patients, homograft valves in 4, fascia lata valves in 2, and xenograft valves in 6. The ascending aorta was replaced with a Dacron tube in 40 patients and with an aortic homograft in 2. Three patients required Dacron patches over the aneurysm, and 1 patient had plication of the aortic wall. Early mortality totaled 12% (6 patients). Only 1 of these patients died in the last five years. Reoperations for homograft incompetence, periprosthetic leak, and acute dissection of an unreplaced aorta resulted in 1 hospital death (33%). Forty-three patients have been followed for up to 8.5 years (mean, 3.5 years), with 7 late deaths (46.2%). The improvement in recent surgical results with decreased operative mortality supports an aggressive surgical approach to Marfan's syndrome in view of the poor prognosis for the natural history of this disease.

Left ventricular hemangioma.

Cardiac hemangiomas are rare, primary benign cardiac tumors. The authors report their experience of diagnosis and treatment of an hemangioma localized into the left ventricle. The tumor could be successfully resected and there is no recurrence at 1 year follow-up.

Coronary artery spasm after coronary artery bypass grafting.

We report a case of a 62-year-old man with severe manifestations of postoperative coronary artery spasm following effective coronary artery bypass grafting. The coronary artery spasm was manifested by ST segment elevation, hypotension and wall motion abnormalities on echocardiography. Urgent angiography confirmed the diagnosis and intracoronary infusion of nitroglycerine and verapamil relieved the coronary spasm.

Severe cutaneous cholesterol emboli syndrome after coronary angiography.

Cholesterol embolization syndrome is due to dislodgment of cholesterol crystals from the atherosclerotic plaques lining the walls of major arteries resulting in an occlusion of small arteries. We describe a case of severe cutaneous cholesterol emboli syndrome following repeat coronary angiography showing by our observation that this syndrome is often unrecognized or misdiagnosed and that a better evaluation of risks factors in patients undergoing invasive procedures could prevent this severe complication.

Left atrial epicardial ablation associated to a Bentall procedure.

Aortic coarctation is quite a common congenital disease and very often associated with other cardiac malformations. A 21-year-old patient presented to our observation with aortic coarctation, aortic valve regurgitation on a dilated aortic root and chronic atrial fibrillation. We performed a two-step operation: the aortic coarctation was treated first and 1 month later a Bentall procedure associated to an epicardial ablation was performed. Since most of the ablation was performed before aortic cross clamping, the ischemic time was only slightly increased. At 3 months follow-up the patient is still on normal sinus rhythm.

Clinical histopathology and ultrastructural analysis of myocardium following microwave energy ablation.

OBJECTIVE: Due to weaknesses of conventional modes for treating atrial fibrillation (AF), surgical energy ablation methods and tools to cure AF have been under rapid development. One of these methods, microwave energy, is beginning to be applied clinically. The purpose of this study was to examine histology and ultrastructure of lesions produced by microwave energy in the myocardium. METHODS: Fifteen consecutive patients underwent surgical microwave energy ablation (Microwave Ablation System with FLEX 4 probe, AFx Inc., Fremont, CA) concomitant to a valve procedure. Epicardial ablation was carried out on the beating normothermic heart prior to performing the valve procedure. Two tissue specimens (1cm(2)) were obtained from each patient; one from the lesion site (right appendage) and the other from an adjacent, non-ablated site, which was used as control. Tissue samples were fixed and stained as appropriate for histological and ultrastructural analysis. RESULTS: All ablated samples revealed observable microscopic alteration, including loss of nuclei, foci of coagulative necrosis or induced irregular bands of contraction. Ultrastructurally, ablated cells demonstrated architectural disarray, loss of contractile filaments, mitochondrial swelling and focal interruption of plasma membrane. CONCLUSIONS: Histologic appearance of lesions created by epicardial microwave energy ablation was consistent over tissue samples, although acute findings demonstrated differences from cryoablation. In most of the cases, lesions were transmural, as was demonstrated by loss of cellular viability throughout the depth of tissue specimens.

Partial anomalous left pulmonary venous return.

We report the case of a 52-year-old woman with partial left anomalous pulmonary venous return who was successfully treated surgically without the use of extracorporeal circulation by diverting the anomalous left vertical vein into the left atrium through a postero-lateral thoracotomy.

Reoperation for myocardial revascularization using the internal mammary artery.

From October 1984 up to February 1989, 40 patients had "redo" myocardial revascularizations using one or both internal mammary arteries (IMA) in over 1000 cases operated upon in our Department for coronary bypass grafts. Thirty-one patients had a further operation for unstable angina difficult to control with drugs. Mean interval of recurrence of angina after previous surgery was 48.5 months for all the cases, but the mean interval before the second bypass operation was 68 months. Severe disease of previous vein grafts was the reason for surgery in 25 patients and progressive atherosclerosis in native coronary arteries in 15 patients. Twenty-one patients had a single mammary artery; both mammary arteries were used in 19. Two cases had endarterectomy on left anterior descending (LAD). Four patients had peroperative acute myocardial infarction (AMI), 3 a low cardiac output syndrome, postoperative bleeding occurred in 3 cases and wound infection in one case. An intraaortic balloon pump was used preoperatively in one case and coming off bypass in two others. One patient died on the second day postoperatively from cardiac arrest following bilateral pneumothorax. There were no late deaths. At a mean follow-up of 20.5 months, 28 patients are free of symptoms but 11 are complaining of angina, 5 during exercise and 6 at rest. An exercise test was positive in 8 patients.

Port-access cardiac surgery: clinical experience with first 50 cases.

BACKGROUND: Minimally invasive cardiac surgery constitutes an expanding field for the treatment of many cardiac diseases. We analyze our experience with the first 50 patients operated upon using the port-access system. METHODS: From October 1999 to October 2000, 50 patients underwent cardiac operations with the port-access technique, for the correction of mitral and tricuspid disease, atrial septal defect closure, and removal of cardiac tumors. The mean age was 56.5 years. In 23 patients the mitral valve was repaired, in 14 cases a prosthetic replacement was performed, in 2 patients a paravalvular leak was resutured, 1 patient had a cardiac myxoma removed, and 1 patient had a correction of tricuspid regurgitation. In 9 cases an atrial septal defect closure was performed. RESULTS: One redo patient, with severe tricuspid regurgitation, needed conversion to sternotomy; in all the other cases the results of surgery were good and there were no surgical limitations. The mean cross-clamping time and bypass time were 53 +/- 19 and 77 +/- 27 min respectively. The mean in-hospital stay was 6 days. Re-exploration for bleeding was required in 7 patients (14%). Three patients (6%) presented with a postoperative neurological lesion; 2 recovered completely within 48 hours whereas 1 patient had permanent hemiplegia at discharge. There was one hospital death (an 81-year-old patient died of multiorgan failure on the thirteenth postoperative day). CONCLUSIONS: Minimally invasive port-access surgery is a reliable alternative to conventional surgery for the treatment of mitral and tricuspid disease, the removal of cardiac tumors, and the correction of atrial septal defects. It reduces trauma to the patient, provides a better cosmetic result and also allows for a faster recovery. Careful patient selection is important to avoid complications. Redo patients can be successfully treated and the risks of re-sternotomy avoided.

"Hybrid" percutaneous and surgical coronary revascularization: selection criteria from a single-center experience.

BACKGROUND: The association of minimally invasive direct coronary artery bypass (MIDCAB) to percutaneous transluminal coronary angioplasty (PTCA) of large arteries with focal lesions can be an alternative therapeutic method for patients with multivessel coronary artery disease. We reviewed our experience regarding 42 patients treated at our Institute. METHODS: MIDCAB and PTCA of the circumflex or right coronary arteries > 3 mm were performed in 42 patients from September 1997 to December 1999. RESULTS: One patient died after MIDCAB in the operating room because of rupture of the left anterior descending anastomosis. Postoperative angiography confirmed patency of the internal mammary artery (IMA) graft in 92.3% of cases: 3 early IMA graft failures occurred. The success rate for PTCA was 98%: in 1 case the wire just would not cross a chronically and totally occluded right coronary artery. The in-hospital morbidity was 12.2%: 2 patients required urgent sternotomy respectively for cardiac tamponade and coronary artery bypass grafting on cardiopulmonary bypass. One patient developed atheroembolism after PTCA with recurrence of symptoms, progressive multiorgan failure and death. Two patients required PTCA on the IMA anastomosis because of early failure of the arterial graft. At a medium follow-up of 535 days, all 40 survivors are in Canadian Cardiovascular Society class I. CONCLUSIONS: Hybrid revascularization appears to be an effective treatment for selected patients with multivessel coronary artery disease. The immediate success seems related to the learning curve for MIDCAB.

[The correction of pulmonary insufficiency with a cryopreserved homograft: an optimal solution to a postoperative problem not rare]. / Correzione dell'insufficienza polmonare con homograft criopreservato: ottima soluzione ad un problema post-chirurgico non raro.

Although the results of surgical repair for congenital pulmonary stenosis are generally good, some patients develop progressive symptoms related to pulmonary regurgitation and right ventricular dilation. Pulmonary homograft implantation may have a beneficial effect on these symptoms, due to a reduction in the volume overload of the right ventricle and hemodynamic improvement. We describe our experience of one patient with severe pulmonary regurgitation following pulmonary valvotomy performed with the Brock technique during childhood because of pulmonary valve stenosis. The patient was admitted to our Institution because of dyspnea on exertion (NYHA functional class II-III) and paroxysmal episodes of supraventricular arrhythmias. Echocardiography showed severe pulmonary regurgitation, an important right ventricular dilation associated with severe tricuspid insufficiency and a patent foramen ovale without any significant shunts. Surgical repair was performed through a median sternotomy with cardiopulmonary bypass and moderate hypothermia. The right ventricular infundibulum was opened and a cryopreserved pulmonary homograft was implanted with continuous sutures. De Vega annuloplasty was performed on the tricuspid valve and the patent foramen ovale was closed with a running suture. Postoperative course was uneventful and the patient was discharged on the seventh postoperative day. Three months after surgery the patient is asymptomatic and echocardiographic evaluation shows no evidence of pulmonary or tricuspid regurgitation, a decrease in right ventricular dilation and a significant improvement in biventricular systolic and diastolic function. In conclusion, pulmonary regurgitation after surgical valvotomy can be treated with the implantation of a cryopreserved pulmonary homograft with satisfactory results. It would appear advisable to perform surgical repair of concomitant right heart anomalies, such as secondary tricuspid insufficiency, to obtain both a decrease in right ventricular overload and a regression of its preoperative dilation.

[Organic subaortic stenosis. Surgical indications, surgical technic, late results]. / Stenosi subaortiche organiche. Indicazioni operatorie, tecnica chirurgica, risultati a distanza.

Between 1966 and 1979 60 patients underwent resection of organic subaortic stenosis at the National Heart Hospital. There was a male:female ratio of 40:20 and an age range of 4 to 56 years (mean 18 years). 22 patients (36.7%) had a single or multiple additional cardiac abnormalities including left ventricular outflow tract obstruction (12 cases), right ventricular outflow tract obstruction (3 cases), ventricular septal defect (6 cases), patent ductus arteriosus (5 cases), aortic coarctation (1 case), congenital mitral stenosis (1 case) and mitral atresia associated with a single ventricle (1 case). Isolated resection of the organic sub-aortic with myotomy and wedge resection was performed in 47 patients and Cooley technique in 2 patients. Total aortic root replacement with a homograft valve was necessary in 4 patients and the 22 patients additional cardiac abnormalities received concomitant surgery. There was one early death (2.6%) amongst the 38 patients with isolated organic sub-aortic stenosis and no late deaths. There were 3 early deaths (13.7%) amongst the 22 patients with additional cardiac abnormalities and one late sudden death after 14 months. There were 7 non-fatal complications: a myocardial infarction, AV block and pacemaker insertion; three mild aortic regurgitations; one mild mitral regurgitation; an arrhythmia due to Wolf Parkinson White syndrome; and an aortic and mitral valve replacement after 9 years. 43 other patients have been followed for 1 to 14 years and are symptom free. Left bundle branch block is present in two of them. Resection of organic sub-aortic stenosis with myotomy and wedge resection is a safe technique and offers an excellent prognosis for this group of congenitally compromised patients.

How to determine the correct placement of the retrograde cardioplegia catheter.

Besides the surgeon's experience, there is no objective method to detect whether the retrograde cannula is inserted correctly before injecting the cardioplegia and measuring the coronary sinus pressure after the aorta cross-clamp. Repositioning of the retrograde cannula once extracorporeally is not always an easy maneuver and may include the risk of venous air suction. Manual detection of the cannula's position may jeopardize the stability of an ischemic heart (Ann Thorac Surg 50(6) (1990) 882; J Cardiothorac Vasc Anesth 5(6) (1991) 646; Ann Thorac Surg 52(4) (1991) 879). Determining the retrograde cannula position avoiding unnecessary prolongation of the ischemia would allow a better protection of the heart. To our knowledge such a method has not yet been published.

[Rupture of interventricular septum secondary to blunt chest trauma. Report of a case surgically treated with success (author's transl)]. / Rottura del setto interventricolare da trauma chiuso del torace. A proposito di un caso operato con successo

A case of interventricular septal defect secondary to blunt chest trauma is reported. It was characterized by a disconnection of the interventricular muscolar septal in the anterosuperior part of the heart wall. The diagnosis, suspected by clinical and instrumental parameters, was definitely confirmedy by hemodynamic and contrastographic examination. Repair surgery of the defect with a dacron patch was performed, using extracorporea normothermic circulation seven months after the accident. The patient was examined three months and twelve months after the operation; the clinical examinations did not reveal any cardiac murmur and the patient's health was satisfactory. The incidence, mechanism of rupture of interventricular septum and the main surgical and clinical aspects of this type of pathology are discussed.