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Dive into the research topics where Robert K. Clemens is active.

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Featured researches published by Robert K. Clemens.


Vasa-european Journal of Vascular Medicine | 2015

Vascular malformations revisited

Robert K. Clemens; Thomas Pfammatter; Thomas O. Meier; Ahmad I. Alomari; Beatrice Amann-Vesti

Vascular malformations are congenital anomalies that can affect each part of the vasculature. Combined forms are common and they are often part of complex syndromes. Most malformations are diagnosed during infancy, but some get obvious only later in life. The field of vascular malformations is emerging with recently described new entities and treatments. Still, misdiagnosis is common in this field, leading to nosologic confusion and wrong treatment. Clinical evaluation and imaging are the gold standard for diagnostic confirmation. Sclerotherapy and embolization are the main treatment techniques but are also used preoperatively to reduce blood loss and shrink the lesion if surgery is planned. Despite new treatment options, especially if extensive in size or involving vulnerable structures, vascular malformations are still considered chronic diseases and cause significant morbidity. Common understanding and agreement on terminology and a multidisciplinary approach are the basis of successful treatment and long-term support for these patients. Continuing research in the field of vascular anomalies will improve knowledge and create further treatment options.


Journal of Vascular and Interventional Radiology | 2013

The Use of Endovenous Laser Treatment in Toddlers

Kendall King; Mary Landrigan-Ossar; Robert K. Clemens; Gulraiz Chaudry; Ahmad I. Alomari

The use of endovenous laser ablation therapy in children is limited. Klippel-Trenaunay syndrome (KTS) is associated with persistent ectatic anomalous veins within the affected extremity, with increased risk of thromboembolism. The present report describes four toddlers (<20 kg) with KTS of the lower extremity who underwent a total of five endovenous laser procedures for treatment of ectatic anomalous marginal venous system, without complications.


Vasa-european Journal of Vascular Medicine | 2015

Combined and complex vascular malformations.

Robert K. Clemens; Thomas Pfammatter; Thomas O. Meier; Ahmad I. Alomari; Beatrice Amann-Vesti

The correct diagnosis of vascular malformations is obtainable by clinical assessment and patient history in the majority of cases. Nonetheless, confusion in nomenclature, existence of multiple classifications and rarity of these lesions leads to misdiagnosis and related wrong treatment. This is especially the case in combined or complex vascular malformations or vascular malformations that are part of syndromes as these have overlapping clinical and imaging features. New entities in the field of vascular anomalies have been described recently like fibro-adipose vascular anomaly or central conducting lymphatic anomalies.


Vasa-european Journal of Vascular Medicine | 2016

Vertebral and internal mammary artery steal syndrome in patients with hemodialysis access

Christoph Thalhammer; Robert K. Clemens; Marie-Luise Valentin; Elena Alonso; Stephan Segerer; Marc Husmann; Beatrice Amann-Vesti

BACKGROUND Increased flow in the subclavian artery feeding a vascular access for hemodialysis can induce steal phenomena in the vertebral (VA) and internal mammary artery (IMA). The aim of this study was to describe the hemodynamic effects of access flow on the VA and IMA in patients with native fistulas and grafts. PATIENTS AND METHODS Peak systolic (PSV) and end diastolic (EDV) velocity measurements of the VA, IMA and carotid arteries, as well as flow volume measurements of the subclavian artery, were performed. Flow measurements at the side of the vascular access were compared with the contralateral side. Fifty-five patients were consecutively included, most with a radio-cephalic fistula on the left arm with a mean shunt volume of 1156 ml/min. RESULTS Pathologic flow patterns were observed in the ipsilateral VA in four patients (7.3 %); contralateral VA flow was normal in all patients. Peak systolic velocity of the VA was significantly decreased at the side of the shunt arm with a PSV of 42.6 ± 11.8 cm/s compared to 48.4 ± 15.6 cm/s contralateral (p < 0.05). The IMA flow pattern were normal in all patients. The PSV of the IMA was significantly decreased (p < 0.01) at the side of the shunt arm (87.5 ± 29.1 cm/s) compared to the non-shunt arm (95.9 ± 27.4 cm/s). CONCLUSION We describe significant hemodynamic effects of fistulas to the vertebral and internal mammary arteries. Doppler spectral analysis of the vertebral and internal mammary arteries should be integrated in ultrasound, especially in patients with cerebrovascular or cardiac symptoms.


Vasa-european Journal of Vascular Medicine | 2015

Nitrous oxide/oxygen inhalation provides effective analgesia during the administration of tumescent local anaesthesia for endovenous laser ablation

Thomas O. Meier; Vincenzo Jacomella; Robert K. Clemens; Beatrice Amann-Vesti

BACKGROUND Tumescent anaesthesia (TA) is an important but sometimes very painful step during endovenous thermal ablation of incompetent veins. The aim of this study was to examine whether the use of fixed 50% nitrous oxide/oxygen mixture (N2O/O2), also called equimolar mixture of oxygen and nitrous oxide, reduces pain during the application of TA. PATIENTS AND METHODS Patients undergoing endovenous laser ablation (EVLA) of incompetent saphenous veins were included. Thirty consecutive patients inhaled N2O/O2 during the application of TA. Thirty consecutive patients received TA alone (controls). Patients were asked to complete a questionnaire immediately after the intervention to assess satisfaction with the intervention and pain-levels during the different steps of the intervention (0=not at all, 10=very much). Adverse events during the treatment were monitored. RESULTS 30 patients (14 men, mean age of 44 years) were included in the N2O/O2 group and 30 patients (9 men, mean age 48 years) were included in the control group. In the N2O/O2 group a significantly lower pain score was noted (mean 2.45 points, range 0-6) compared to the controls (mean 4.3 points, range 1-9, p<0.001). Overall, 64.5% of the patients were perfectly satisfied with the N2O/O2-Inhalation. Only 4 patients receiving N2O/O2 complained of adverse effects such as unpleasant loss of control (2 patients), headache (1 patient) and dizziness (1 patient). CONCLUSIONS N2O/O2 is a safe and effective method to reduce pain during the application of tumescent anaesthesia for EVLA.


Nephrology | 2015

Acute effects of haemodialysis on central venous and arterial pressure characteristics

Christoph Thalhammer; Stephan Segerer; Marlene Augustoni; Vincenzo Jacomella; Robert K. Clemens; Rudolf P. Wüthrich; Beatrice Amann-Vesti; Marc Husmann

Haemodynamic stability of patients during haemodialysis (HD) sessions is of pivotal importance and accurate determination of dry weight remains a challenge. Little information is available about central venous and aortic pressure during dialysis. In this pilot study we used a non‐invasive technique to describe the changes in central venous pressure (CVP) during dialysis.


Case Reports | 2016

Assessment of PTEN-associated vascular malformations in a patient with Bannayan–Riley–Ruvalcaba syndrome

Sandra Anusic; Robert K. Clemens; Thomas O. Meier; Beatrice Amann-Vesti

Misdiagnosis of phosphatase and tensin homologue hamartoma syndromes is common. Correct diagnosis has a relevant impact on patients, as the risk of malignancies is high and treatment options are limited. We report the case of a 24-year-old man who presented with symptomatic vascular intramuscular lesions of the left forearm and right calf, macrocephaly, post Hashimoto thyroiditis, a multicystic intracranial paratrigonal lesion, lentiginous hyperpigmented maculae on the foreskin and multiple skin lesions. MRI showed extended fibrofatty changes and malformed vessels in the forearm and calf lesions, also, arteriovenous shunting was present in these lesions. The patient had been treated by embolisation and surgically in the past, with limited results. A multidisciplinary assessment and genetic counselling were undertaken and a surveillance programme was initiated. Treatment options of the symptomatic vascular lesions include excision or possibly cryoablation. Physiotherapy to prevent progression of the contractures should be initiated meanwhile.


Vasa-european Journal of Vascular Medicine | 2017

Percutaneous sclerotherapy for spongiform venous malformations – analysis of patient-evaluated outcome and satisfaction

Robert K. Clemens; Frederic Baumann; Marc Husmann; Thomas O. Meier; Christoph Thalhammer; Gail MacCallum; Beatrice Amann-Vesti; Ahmad I. Alomari

BACKGROUND Congenital venous malformations are frequently treated with sclerotherapy. Primary treatment goal is to control the often size-related symptoms. Functional impairment and aesthetical aspects as well as satisfaction have rarely been evaluated. PATIENTS AND METHODS Medical records of patients who underwent sclerotherapy of spongiform venous malformations were reviewed and included in this retrospective study. The outcome of sclerotherapy as self-reported by patients was assessed in a 21 item questionnaire. RESULTS Questionnaires were sent to 166 patients with a total of 327 procedures. Seventy-seven patients (48 %) with a total of 159 procedures (50 %) responded to the survey. Fifty-seven percent of patients were male. The age ranged from 1 to 38.1 years with a median age of 16.4 years. The lower extremities were the most common treated area. Limitations caused by the venous malformation improved in the majority of patients (e.g. pain improvement 87 %, improvement of swelling 83 %) but also worsening of symptoms occurred in a minority of cases. Seventy-seven per cent would undergo sclerotherapy again. CONCLUSIONS Sclerotherapy for treatment of venous malformations results in significant reduction of symptoms. Multiple treatments are often needed, but patients are willing to undergo them.


Vasa-european Journal of Vascular Medicine | 2016

Long-term follow-up after endovascular revascularisation for acute limb ischaemia - a retrospective single-centre cohort

Fabian Johner; Robert K. Clemens; Marc Husmann; Christoph Thalhammer; Burkhardt Seifert; Beatrice Amann-Vesti

BACKGROUND We evaluated the long-term outcome after endovascular revascularisation for acute limb ischaemia (ALI). PATIENTS AND METHODS From a prospectively maintained database, 318 endovascular interventions for ALI were identified between 2004 and 2010. Event history and survival were analysed using the Kaplan-Meier method and Cox regression. Endpoints were target vessel revascularisation (TVR), non-target extremity revascularisation (NTER), amputation, major vascular events, coronary artery revascularisation and amputation-free survival. RESULTS Follow-up data of 303 patients (mean age 68.5 ± 12.7 years, 40% female) were available. The mean follow-up time was 38.7 ± 26.2 months. TVR was performed in 40.1 ± 2.9% at 1 year and 66.5 ± 3.8% at 5 years. NTER at 1 and 5 years were 7.1 ± 1.5% and 29.2 ± 4%, respectively. The proportion of patients who needed major or minor amputation was 4.3 ± 1.2% after 1 year and 9 ± 2.1% after 5 years. Amputation-free survival at 1 year was 90.3 ± 1.8% and 74.8 ± 3.2% at 5 years. Coronary artery disease (HR 2.22, 95% CI 1.33 to 3.7, p = 0.002) and atrial fibrillation (HR 2.56, % CI 1.3 to 5.04, p = 0.007) were independently associated with a worse amputation-free survival. The cumulative proportion surviving one year following acute limb ischemia was 95.4 ± 1.2% and 79.7 ± 3.1% after 5 years. CONCLUSIONS Long-term amputation-free survival after successful revascularisation for ALI is high; negative predictors are coronary artery disease and atrial fibrillation.


Praxis Journal of Philosophy | 2016

CME: Vaskuläre Malformationen

Dimitri Patriki; Beatrice Amann-Vesti; Thomas O. Meier; Christoph Thalhammer; Thomas Pfammatter; Robert K. Clemens

Zusammenfassung. Vaskulare Missbildungen entstehen kongenital und konnen jedes Strombett betreffen. Trotz ihrer Benignitat konnen sie einen destruktiven Verlauf nehmen, indem sie umliegende Strukturen verdrangen. Die Unterteilung erfolgt nach Stromgebiet und Morphologie. In mehr als 50 % der Falle ist die Zuweisungsdiagnose trotz adaquater Bildgebung inkorrekt. Haufig werden falschlicherweise Begriffe wie «Hamangiom» oder das Eponym «Klippel-Trenaunay-Syndrom» verwendet. Da uber 80 % der korrekten Diagnosen klinisch gestellt werden konnten, ist die klinische Untersuchung und Beschreibung der beteiligten Gefasse von entscheidender Bedeutung.

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Ahmad I. Alomari

Boston Children's Hospital

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Anna P. Lillis

Boston Children's Hospital

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