Decrement Evoked Potential Mapping to Guide Ventricular Tachycardia Ablation: Elucidating the Functional Substrate
Despite advances in mapping and ablation, the long-term success of ventricular tachycardia (VT) ablation is moderate at best.1 The high recurrence rate could be attributed to either the evolving scar or inadequate ablation of pre-existing potential scar channels. Substrate-based ablation strategies have been shown to be as equally effective as activation mapping, which is often limited by haemodynamic instability and non-inducibility.2 (Source: Radcliffe Cardiology)
Source: Radcliffe Cardiology - December 24, 2020 Category: Cardiology Source Type: research

Anisotropic Cardiac Conduction
Anisotropy is the property of directional dependence. In cardiac tissue, conduction velocity (CV) is anisotropic, that is, the magnitude of CV depends on the direction of a wave of activation. Anisotropic conduction facilitates prompt and synchronised cardiac chamber activation. In disease states, anisotropic conduction is implicated in the genesis of pathological arrhythmias. (Source: Radcliffe Cardiology)
Source: Radcliffe Cardiology - December 24, 2020 Category: Cardiology Source Type: research

Frequency and Determinants of Spontaneous Conversion to Sinus Rhythm in Patients Presenting to the Emergency Department with Recent-onset Atrial Fibrillation: A Systematic Review
In patients presenting at the emergency department (ED) with symptomatic recent-onset AF, immediate restoration of sinus rhythm by pharmacological cardioversion (PCV) or electrical cardioversion (ECV) is frequently performed.1,2Nevertheless, most of these patients convert spontaneously to sinus rhythm without the need of additional interventions.3 –7 Several studies have indicated that rate control to manage symptoms and waiting for spontaneous conversion (SCV) to sinus rhythm is a (Source: Radcliffe Cardiology)
Source: Radcliffe Cardiology - December 24, 2020 Category: Cardiology Source Type: research

Anisotropic Conduction and Re-entry in the Heart
Following the seminal paper by Madison Spach and Mark Josephson, clinicians have been aware of anisotropic re-entry as an established mechanism of arrhythmogenesis, although the exact mechanisms responsible remain uncertain.1 Nevertheless, changes in microanatomical structures, such as cellular coupling, gap junction distribution and function and fibre disarray, lead to anisotropic conduction, i.e. (Source: Radcliffe Cardiology)
Source: Radcliffe Cardiology - December 24, 2020 Category: Cardiology Source Type: research

Cardiac MRI to Manage Atrial Fibrillation
AF is a common arrhythmia in clinical practice, with a prevalence of 2.7 –6.1 million that is expected to rise to 5.6–12 million by 2050 in the US alone.1,2 Patients with AF have an increased risk of stroke and mortality and a decreased quality of life.3 In addition, management of AF increases the cost of healthcare.4,5,6 The mechanisms of AF are complex and are associated with electric and structural remodelling.7,8 (Source: Radcliffe Cardiology)
Source: Radcliffe Cardiology - December 7, 2020 Category: Cardiology Source Type: research

Sudden Cardiac Death Risk Stratification and Prevention in Chagas Disease: A Non-systematic Review of the Literature
Chagas disease is an important public health problem in Latin America. Almost 25% of the population (approximately 65 million individuals) are at risk of infection and another 6 million people are affected.1 However, migration and globalisation have resulted in the increased presence of Chagas disease worldwide, particularly in the US and Europe. (Source: Radcliffe Cardiology)
Source: Radcliffe Cardiology - November 30, 2020 Category: Cardiology Source Type: research

Management of Cardiac Sarcoidosis in 2020
Sarcoidosis is an inflammatory granulomatous disease that can affect any organ. (Source: Radcliffe Cardiology)
Source: Radcliffe Cardiology - November 24, 2020 Category: Cardiology Source Type: research

Type and Duration of Dual Antiplatelet Therapy in Complex Percutaneous Coronary Intervention
Complex percutaneous coronary intervention (PCI) usually refers to procedures that include bifurcation with two stents implanted, the treatment of three or more lesions, the implantation of three or more stents, total stent length>60 mm, or a chronic total occlusion (CTO).1 However, as there is no universal definition, other features, such as left main (LM) or proximal left anterior descending (LAD) lesions, bifurcation, vein bypass graft PCI, lesion length ≥30 mm, rotational atherectomy use for severely calci (Source: Radcliffe Cardiology)
Source: Radcliffe Cardiology - November 23, 2020 Category: Cardiology Source Type: research

Acute Heart Failure in Coronavirus Disease 2019 and the Management of Comedications
Dear Editor, (Source: Radcliffe Cardiology)
Source: Radcliffe Cardiology - November 23, 2020 Category: Cardiology Source Type: research

Sodium –Glucose Co-transporter 2 Inhibitors in Heart Failure: Recent Data and Implications for Practice
Heart failure (HF) is a shared chronic phase of many cardiac diseases, including ischaemic heart disease, chronic obstructive pulmonary disease and hypertension. (Source: Radcliffe Cardiology)
Source: Radcliffe Cardiology - November 13, 2020 Category: Cardiology Source Type: research

Rhythm Control in Heart Failure Patients with Atrial Fibrillation
Sir James Mackenzie, famous for describing the first mechanistic insights into AF in 1902 using his polygraph, also reported that AF was present in 80 –90% of patients who had congestive heart failure (HF) in 1920.1 Today, the conditions are the two ‘epidemics’ of cardiovascular disease.2 They are dominating cardiovascular care and, with increasing longevity, they will become more prevalent and place an even greater burden upon healthcare resources over the coming decades. (Source: Radcliffe Cardiology)
Source: Radcliffe Cardiology - November 5, 2020 Category: Cardiology Source Type: research

Big Data and Artificial Intelligence: Opportunities and Threats in Electrophysiology
Clinical research that uses artificial intelligence (AI) and big data may aid the prediction and/or detection of subclinical cardiovascular diseases by providing additional knowledge about disease onset, progression or outcome. Clinical decision-making, disease diagnostics, risk prediction or individualised therapy may be informed by insights obtained from AI algorithms. (Source: Radcliffe Cardiology)
Source: Radcliffe Cardiology - November 5, 2020 Category: Cardiology Source Type: research

Impact of Micro-, Mini- and Multi-Electrode Mapping on Ventricular Substrate Characterisation
Accurate substrate characterisation is important for depicting scar-related re-entrant tachycardia to optimise ablation targets and strategies. (Source: Radcliffe Cardiology)
Source: Radcliffe Cardiology - November 5, 2020 Category: Cardiology Source Type: research

In Search of Homo Deus
If you search “artificial intelligence” in PubMed today (16 October 2020), you end up with 110,855 results! It is more than obvious that advanced computing is entering our lives – perhaps not yet as much as Yuval Noah Harari has predicted in his bookHomo Deus, but definitely to an extent that our medical practice is substantially affected, as van de Leur and colleagues discuss in this issue of the journal. (Source: Radcliffe Cardiology)
Source: Radcliffe Cardiology - November 5, 2020 Category: Cardiology Source Type: research

Corrigendum to: Pulmonary Hypertension in Heart Failure Patients
In the article by Rao et al. entitled Pulmonary Hypertension in Heart Failure Patients (Cardiac Failure Review 2020;6:e05.https://doi.org/10.15420/cfr.2019.09), the following correction should be made. (Source: Radcliffe Cardiology)
Source: Radcliffe Cardiology - October 23, 2020 Category: Cardiology Source Type: research

Determinants of Functional Capacity and Quality of Life After Implantation of a Durable Left Ventricular Assist Device
According to the third report from the International Society for Heart and Lung Transplantation (ISHLT) Mechanically Assisted Circulatory Support Registry, more than 15,500 left ventricular assist devices (LVADs) were implanted worldwide between 2013 and 2017.1 Originally, LVADs were exclusively implanted as part of a bridge to transplantation (BTT) strategy, but in recent years a large proportion of patients undergoing LVAD implantation received the device as final treatment for advanced heart failure (HF), so-ca (Source: Radcliffe Cardiology)
Source: Radcliffe Cardiology - October 16, 2020 Category: Cardiology Source Type: research

Heart Failure With Mid-range or Recovered Ejection Fraction: Differential Determinants of Transition
Heart failure (HF) is a complex syndrome caused by functional and structural abnormalities of the left ventricle (LV) resulting in a combination of typical signs and symptoms. (Source: Radcliffe Cardiology)
Source: Radcliffe Cardiology - October 16, 2020 Category: Cardiology Source Type: research

Effects of Exercise Training on Cardiac Function in Heart Failure with Preserved Ejection Fraction
Nearly half of patients with heart failure (HF) in the community have HF with preserved ejection fraction (HFpEF) and mortality and morbidity in this group of patients is high.1 –4 However, to date, there is no established pharmacotherapy to improve survival in HFpEF.5 –9 Patients with HFpEF are often elderly and their primary chronic symptom is severe exercise intolerance, which results in a reduced quality of life.10,11 There is much evidence that l (Source: Radcliffe Cardiology)
Source: Radcliffe Cardiology - October 16, 2020 Category: Cardiology Source Type: research

The Role of Hemodynamic Support in High-risk Percutaneous Coronary Intervention
Coronary artery disease (CAD) is a leading cause of morbidity and mortality globally, despite advances in medical and preventive therapy. (Source: Radcliffe Cardiology)
Source: Radcliffe Cardiology - October 13, 2020 Category: Cardiology Source Type: research

Feasibility, Safety, and Clinical Performance of Self-apposing Stents for Left Main Stenosis
Significant stenosis of the left main (LM) coronary artery is observed in 7% of coronary angiographies.1 Coronary artery bypass grafting has traditionally been the treatment of choice. (Source: Radcliffe Cardiology)
Source: Radcliffe Cardiology - September 29, 2020 Category: Cardiology Source Type: research

Percutaneous Coronary Intervention for Chronic Total Occlusion
Coronary chronic total occlusion (CTO), defined as complete occlusion of a coronary artery for at least 3 months with thrombolysis in myocardial infarction (TIMI) grade 0 flow, represents one of the most complex situations in the field of interventional cardiology.1 Despite an incidence of CTO in patients with stable coronary artery disease (CAD) undergoing coronary angiography of 18 –46%, the number of percutaneous coronary interventions (PCIs) for CTO is still less than 4% of all percutaneous revascularizations. (Source: Radcliffe Cardiology)
Source: Radcliffe Cardiology - September 29, 2020 Category: Cardiology Source Type: research

Obstructive Sleep Apnoea Syndrome: Continuous Positive Airway Pressure Therapy for Prevention of Cardiovascular Risk
The WHO has established that coronary artery and cerebrovascular disease represent the main causes of premature death and disability in developed countries.1 However, the incidence and prevalence of cardiovascular and cerebrovascular disease is also increasing in developing countries as a result of population ageing and changes in lifestyle. For these reasons, the prevention and treatment of cardiovascular disease continues to be one of the key objectives of global health policies. (Source: Radcliffe Cardiology)
Source: Radcliffe Cardiology - September 29, 2020 Category: Cardiology Authors: mehul Source Type: research

What is the Real Message of the International Study of Comparative Health Effectiveness with Medical and Invasive Approaches (ISCHEMIA) Trial for Academic and Practising Cardiologists?
Defining the best management strategies for patients with stable ischaemic heart disease (SIHD) has been the subject of scientific study for nearly 50 years since the advent of coronary artery bypass grafting (CABG) surgery by Favaloro in 1967 and, a decade later, the development of percutaneous coronary intervention (PCI) by Gruentzig in 1977.1,2 Randomised controlled trials of CABG surgery versus medical therapy were initiated in the late 1970s and 1980s in patients with SIHD and showed that revascularisation re (Source: Radcliffe Cardiology)
Source: Radcliffe Cardiology - September 29, 2020 Category: Cardiology Authors: mehul Source Type: research

Differential Diagnosis of Wide QRS Tachycardias
The term narrow QRS tachycardia indicates individuals with a QRS duration ≤120 ms, while wide QRS tachycardia refers to tachycardia with a QRS duration>120 ms.1 Narrow QRS complexes are due to rapid activation of the ventricles via the His –Purkinje system, suggesting that the origin of the arrhythmia is above or within the His bundle. (Source: Radcliffe Cardiology)
Source: Radcliffe Cardiology - September 28, 2020 Category: Cardiology Source Type: research

Gone, but not Forgotten
The direct impact of coronavirus disease 2019 (COVID-19) has resulted in a shift from inpatient to offsite care, as bed utilisation is appropriated to COVID-19 patients or potential COVID-19 patients. (Source: Radcliffe Cardiology)
Source: Radcliffe Cardiology - September 28, 2020 Category: Cardiology Source Type: research

Congestion and Diuretic Resistance in Acute or Worsening Heart Failure
From Acute Heart Failure Towards Worsening or De Novo Heart FailureThe natural history of heart failure (HF) is characterised by disease progression and episodes of worsening HF and acute decompensation requiring outpatient treatment intensification, emergency department or in-hospital care. (Source: Radcliffe Cardiology)
Source: Radcliffe Cardiology - September 28, 2020 Category: Cardiology Source Type: research

Transcriptomic Research in Heart Failure with Preserved Ejection Fraction: Current State and Future Perspectives
Heart failure with preserved ejection fraction (HFpEF) is a common disease with rapidly increasing incidence and prevalence due to demographic changes.1 Well-known risk factors, such as metabolic syndrome (arterial hypertension, diabetes, obesity and dyslipidaemia), chronic kidney disease and AF, predispose to the development of HFpEF, especially in older people. (Source: Radcliffe Cardiology)
Source: Radcliffe Cardiology - September 28, 2020 Category: Cardiology Source Type: research

A New Era in Zero X-ray Ablation
X-rays used in interventional cardiology are proven (class I) carcinogens, and the electrophysiology community should make every effort to give “the right imaging exam, with the right dose, to the right patient”.1 This may be an effective strategy for the primary prevention of cancer for physicians, medical staff and patients (particularly children, young adults and women).2 The impact of X-rays on male and female reproductive health is well known.3 (Source: Radcliffe Cardiology)
Source: Radcliffe Cardiology - September 15, 2020 Category: Cardiology Source Type: research

What is the Real Message of the ISCHEMIA Trial from a Clinician ’s Perspective?
Management goals in patients with stable coronary disease or chronic coronary syndrome include controlling symptoms and reducing the risk of future cardiovascular events.1,2 Randomised trials conducted in the bare metal stents era have indicated that an invasive management strategy, which includes coronary angiography, followed by percutaneous or surgical revascularisation, if indicated, was not superior to optimal medical therapy (OMT) alone in reducing the risk of cardiovascular death or MI. (Source: Radcliffe Cardiology)
Source: Radcliffe Cardiology - August 31, 2020 Category: Cardiology Authors: mehul Source Type: research

Atrial Fibrillation Structural Substrates: Aetiology, Identification and Implications
AF is the most common sustained cardiac rhythm disorder and is associated with increased morbidity and mortality. Since the first description of AF initiation by triggers from pulmonary veins sleeves, pulmonary vein isolation (PVI) has become the standard ablation strategy in patients with AF.1 However, freedom from the arrhythmia, particularly in non-paroxysmal AF, remains suboptimal, and it is now clear that, in these patients, AF is maintained by an atrial substrate beyond the pulmonary veins. (Source: Radcliffe Cardiology)
Source: Radcliffe Cardiology - August 31, 2020 Category: Cardiology Source Type: research

Electrophysiology in the Era of Coronavirus Disease 2019
Coronavirus disease 2019 (COVID-19) is caused by the novel betacoronavirus officially named by the WHO as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). (Source: Radcliffe Cardiology)
Source: Radcliffe Cardiology - August 31, 2020 Category: Cardiology Source Type: research

His –Purkinje Conduction System Pacing: State of the Art in 2020
Right ventricular apical pacing (RVAP) results in dyssynchronous ventricular activation that can lead to impairment of ventricular function. (Source: Radcliffe Cardiology)
Source: Radcliffe Cardiology - August 31, 2020 Category: Cardiology Source Type: research

Pregnancy in Women with Congenital Heart Disease: A Guide for the General Cardiologist
Dyspnea, palpitations, edema, and fatigue are common symptoms during pregnancy. For women with congenital heart disease (CHD), it may be difficult to discern whether symptoms are due to normal pregnancy or underlying cardiac disease. (Source: Radcliffe Cardiology)
Source: Radcliffe Cardiology - August 25, 2020 Category: Cardiology Source Type: research

The Coronavirus Disease 2019 Outbreak Highlights the Importance of Sex-sensitive Medicine
While 2020 is only halfway through, we have already experienced a historical year in global healthcare with a high societal impact. When the first severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections were reported in China at the end of 2019, few people realised we would all be affected by a global pandemic several months later. (Source: Radcliffe Cardiology)
Source: Radcliffe Cardiology - August 24, 2020 Category: Cardiology Authors: mehul Source Type: research

The Impact of Ethnicity on Cardiac Adaptation
Athletes may occasionally succumb to sudden cardiac arrest because of a quiescent cardiac abnormality. (Source: Radcliffe Cardiology)
Source: Radcliffe Cardiology - August 24, 2020 Category: Cardiology Authors: mehul Source Type: research

The Role of Nocturnal Blood Pressure and Sleep Quality in Hypertension Management
Hypertension is a major independent risk factor for cardiovascular (CV) diseases, including cardiac death, coronary heart disease, heart failure, stroke and chronic kidney disease. (Source: Radcliffe Cardiology)
Source: Radcliffe Cardiology - August 24, 2020 Category: Cardiology Authors: mehul Source Type: research

Overview of Quantitative Flow Ratio and Optical Flow Ratio in the Assessment of Intermediate Coronary Lesions
Physiological lesion assessment is recommended for the identification of intermediate coronary lesions that might benefit from percutaneous coronary intervention (PCI).1 The quantitative flow ratio (QFR) was developed to derive coronary physiology from angiographic images, whereas the optical flow ratio (OFR) is a more recent approach for the rapid and automated assessment of coronary physiology from intracoronary optical coherence tomography (OCT).2 –5 The aim of this article is to (Source: Radcliffe Cardiology)
Source: Radcliffe Cardiology - August 14, 2020 Category: Cardiology Source Type: research

Clinical Trial Perspective: Cost-effectiveness of Transcatheter Mitral Valve Repair Versus Medical Therapy in Patients with Heart Failure and Secondary Mitral Regurgitation. Results From the COAPT Trial
In the wake of transcatheter aortic valve replacement revolutionizing the treatment of aortic stenosis, sizeable interest has arisen in the development of percutaneous technologies to treat patients with mitral valve disease. Thus, when a percutaneous method of edge-to-edge mitral valve repair (TMVr) using the MitraClip device (Abbott Vascular) was introduced, this device was met with considerable enthusiasm. (Source: Radcliffe Cardiology)
Source: Radcliffe Cardiology - August 14, 2020 Category: Cardiology Source Type: research

Neprilysin as a Biomarker: Challenges and Opportunities
Neprilysin (NEP) was more or less unrecognised by the cardiovascular community until 2014 when the Prospective Comparison of ARNi With ACEi to Determine Impact on Global Mortality and Morbidity in Heart Failure (PARADIGM-HF) study reported impressive clinical benefits resulting from the combination of an angiotensin receptor blocker (ARB) with a neprilysin inhibitor (angiotensin receptor neprilysin inhibitor [ARNi]) over angiotensin-converting enzyme (ACE) inhibition in heart failure with reduced ejection fraction (HFrEF). (Source: Radcliffe Cardiology)
Source: Radcliffe Cardiology - August 14, 2020 Category: Cardiology Source Type: research

Coronavirus Disease 2019 and Heart Failure: A Multiparametric Approach
This review focuses on the implications of coronavirus disease 2019 (COVID-19) in the heart failure (HF) population. First of all, we will describe the cardiovascular implications of COVID-19 and the new practices surrounding the use of telehealth to follow up and triage patients with HF. (Source: Radcliffe Cardiology)
Source: Radcliffe Cardiology - August 14, 2020 Category: Cardiology Source Type: research

Cryoballoon Ablation of Atrial Fibrillation in Octogenarians
AF is a common and clinically impactful arrhythmia. Given both the association of AF with aging and the increasing number of elderly people in the general population, it follows that many AF patients are of advanced age. (Source: Radcliffe Cardiology)
Source: Radcliffe Cardiology - August 13, 2020 Category: Cardiology Authors: mehul Source Type: research

Hybrid Catheter-Based and Surgical Techniques for Ablation of Ventricular Arrhythmias
Catheter-based ablation has been a well-established tool in the treatment of ventricular tachycardia (VT). However, the effectiveness of catheter ablation may be limited by its ability to access sites of arrhythmogenic tissue and achieve adequate lesion size in target areas without risking collateral damage. Antiarrhythmic surgery would be an effective alternative in such situations. (Source: Radcliffe Cardiology)
Source: Radcliffe Cardiology - August 13, 2020 Category: Cardiology Authors: mehul Source Type: research

Applications of Machine Learning in Cardiac Electrophysiology
Artificial intelligence (AI) has recently become a popular term in the technological world. AI refers to the simulation of human intelligence with the capacity for achieving goals within computers. Machine learning (ML) – a subtype of AI – refers to a statistical model that is able to independently learn to make inferences on new data based on data it has previously analysed. (Source: Radcliffe Cardiology)
Source: Radcliffe Cardiology - August 13, 2020 Category: Cardiology Authors: mehul Source Type: research

Atrial Myopathy Underlying Atrial Fibrillation
AF is the most common sustained cardiac rhythm disturbance.1 Worldwide, there is an estimated 33.5 million people with AF as of 2010.2 While there are multiple estimates, the yearly incidence in the US is expected to grow, for example, from 1.2 million cases in 2010 to 2.6 million cases in 2030 and upwards of 6 –12 million cases by 2050.1,3 It is associated with increased morbidity and mortality4 and diminished qualit (Source: Radcliffe Cardiology)
Source: Radcliffe Cardiology - August 11, 2020 Category: Cardiology Authors: mehul Source Type: research

Atrial Tachycardias After Atrial Fibrillation Ablation: How to Manage?
AF is the most common clinical arrhythmia that causes severe adverse cardiovascular events, such as ischaemic stroke and acute heart failure.1 Triggers from the pulmonary vein (PV) have been identified as crucial ectopic sources that initiate AF and pulmonary vein isolation (PVI) is the cornerstone for catheter ablation of AF.2,3 Per the European and US AF guidelines, catheter ablation of AF is currently recommended as the first-line therapy if anti-arrhythmic agents fail to mainta (Source: Radcliffe Cardiology)
Source: Radcliffe Cardiology - August 11, 2020 Category: Cardiology Authors: mehul Source Type: research

The Human Atrioventricular Node: Oedipus and the Riddle of the Sphinx
Cardiac pathologists and electrophysiologists have studied the atrioventricular (AV) node for more than 100 years, since 1906, when Tawara first described the inferior extensions of the AV node in the human heart.1 Still, this important cardiac structure remains “a riddle wrapped up in a mystery, inside an enigma”, to recall the famous Churchill quotation. (Source: Radcliffe Cardiology)
Source: Radcliffe Cardiology - August 11, 2020 Category: Cardiology Authors: mehul Source Type: research

Treatment of Coronavirus Disease 2019: Shooting in the Dark
“When the cause of the sickness is unknown, only a miracle can cure it.”Don Quixote, Miguel de Cervantes, 1605. (Source: Radcliffe Cardiology)
Source: Radcliffe Cardiology - August 10, 2020 Category: Cardiology Authors: mehul Source Type: research

Anticoagulant Therapy for Patients with Coronavirus Disease 2019: Urgent Need for Enhanced Awareness
Coronavirus disease 2019 (COVID-19), which is caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has generated a pandemic that has heavily affected the global population, with more than 5.2 million infected and more than 337,000 deaths worldwide recorded between the end of 2019 and 24 May 2020.1 In the absence of vaccines or specific targeted treatments, strategies to reduce the COVID-19 mortality rate have gained importance as a global need. (Source: Radcliffe Cardiology)
Source: Radcliffe Cardiology - August 7, 2020 Category: Cardiology Authors: mehul Source Type: research

Cardiac Transthyretin-derived Amyloidosis: An Emerging Target in Heart Failure with Preserved Ejection Fraction?
Heart failure with a preserved ejection fraction (HFpEF) comprises half of the heart failure population, and is associated with high morbidity and mortality. HFpEF is induced by multiple coexisting comorbidities, mostly of non-cardiac origin, leading to increased stiffness of the myocardial wall, diastolic dysfunction, elevated filling pressures and eventually to heart failure.1 The interplay between comorbidities greatly differs among patients; however, increasing age is a major driving force. (Source: Radcliffe Cardiology)
Source: Radcliffe Cardiology - August 6, 2020 Category: Cardiology Source Type: research