Cassius Iyad Ochoa Chaar MD, MS, RPVI

Assistant Professor of Surgery (Vascular)

Research Interests

Premature peripheral vascular disease; Endovenous ablation of varicose veins; Endovascular aortic aneurysm repair; Deep vein thrombosis; Catheter-directed thrombolytic therapy

Current Projects

Research Projects for Medical Students

Project 1:

Title: Thrombus Resolution on Ultrasound as a Guide to Anticoagulation Therapy for Provoked Lower Extremity Deep Vein Thrombosis (TRU-DVT)

Description: This is a prospective pilot study looking at provoked deep vein thrombosis resulting from trauma, surgery, and short-term immobilization. Lower extremity deep vein thrombosis is typically treated for 3 months with anticoagulation. This trial attempts to treat patients with DVT due to a reversible factor for one month instead of 3 months. The study is enrolling patients currently.

Project 2:

Title: Guideline Implementation in treating lower extremity Deep vein thrombosis

Description: Periodically, the American college of chest physicians (ACCP) publishes guidelines for treatment of deep vein thrombosis. In real practice, the guidelines are not always strictly followed and treatment may vary depending on the hospital and the provider. This study aims at looking at the modalities of treatment of DVT at Yale New Haven Hospital and assess for the implementation of ACCP guidelines among different providers.

Project 3:

Title: Retrieval of IVC filters: the patients’ perspective

Description: Inferior vena cava (IVC) filters are placed in a select patient population who develop deep vein thrombosis and have contraindication for anticoagulation to prevent development of pulmonary embolism. Most IVC filters are retrievable and should be removed after the risk period resolves because they can cause long-term complications (thrombosis, perforation, migration) when left for a prolonged period of time. This project aims at conducting a questionnaire with the patients that were lost to follow up and did not have retrieval of the IVC filter. The goal is to assess possible reasons for loss of follow up and find ways to improve compliance with the FDA recommendations to retrieve the IVC filter when risk of pulmonary embolism resolves. This study is enrolling patients.

Project 4:

Title: Endovascular IVC filter retriever

Description: Inferior vena cava (IVC) filters are placed in a select patient population who develop deep vein thrombosis and have contraindication for anticoagulation to prevent development of pulmonary embolism. Despite the FDA recommendation to retrieve the IVC filters after the period of risk is resolved, a significant proportion of patients fail to follow up. They frequently present with late complications (thrombosis, perforation migration). Delayed retrieval is very challenging because of tilting or scarring of the struts of the device in the wall of the IVC. There are no devices on the market that are dedicated for that task. In collaboration with Yale school of engineering, design of a new retrieving tool is being developed. The medical student will help with the initial in vitro / animal trialing of the device.

Project 5:

Title: IVC filter removal: survey of vascular specialist practice patterns

Description: Inferior vena cava (IVC) filters are placed in a select patient population who develop deep vein thrombosis and have contraindication for anticoagulation to prevent development of pulmonary embolism. The FDA recommends retrieval of the IVC filter from patients deemed not at risk for pulmonary embolism any more. However, there is no consensus in the community of vascular specialist on when is the best time to retrieve IVC filters and how aggressive to be in removing them when they are “stuck” and not retrieved easily. This project will administer a survey to vascular specialists about their practice pattern with respect to retrieval of IVC filters.

Project 6:

Title: Impact of distal embolization during catheter-directed thrombolytic therapy for lower extremity ischemia

Description: Thrombosis of a lower extremity bypass remains a major challenge for vascular surgeons and a reason for limb loss. Most of bypass thrombosis are treated with catheter directed thrombolysis (administration of alteplase into the thrombus using an infusion catheter). The incidence of embolization (dislodgement of thrombus to block more distal arteries) during thrombolytic therapy and its effect on overall outcomes have not been studies in the literature. This study aims at finding the incidence of distal embolization and its impact on bypass patency and limb loss. Also, evaluate the effectiveness of repeat catheter directed thrombolysis and its long-term outcomes. This project is best for medical students who had some exposure to vascular surgery and have interest in the specialty. (Third and fourth years)

Project 7:

Title: May Thurner syndrome – review of the world’s Literature

Description: May Thurner syndrome is a relatively rare entity where the right iliac artery compresses the left iliac vein at the bifurcation of the Aorta and Inferior vena cava. That can lead to stenosis of the iliac vein, swelling of the left leg and sometimes deep vein thrombosis. The literature has mostly case reports describing this entity and different modalities of treatment. The project involves review of the cases available in the literature and summary of patient demographics, presentation and treatment.

Project 8:

Title: Smoking cessation in vascular patients

Description: Smoking is very prevalent in patients with vascular disease. Patients get advised about smoking cessation all the time. This study is a randomized study to look at whether referring the vascular patients to a smoking cessation clinic would improve the smoking cessation rate compared to just regular reminders and advice during vascular surgery follow up visits. There will be also a survey of the patients to assess for factors associated with success and failure in smoking cessation.


Research Summary

Premature peripheral vascular disease; Endovenous ablation of varicose veins; Endovascular aortic aneurysm repair; Deep vein thrombosis; Catheter-directed thrombolytic therapy

Extensive Research Description

Premature peripheral vascular disease; Endovenous ablation of varicose veins; Endovascular aortic aneurysm repair; Deep vein thrombosis; Catheter-directed thrombolytic therapy


Selected Publications

  • Ochoa Chaar, C.I., Eid, R.E., Tzeng, E., Chaer, R.A., Makaroun, M.S., Cho, J.S. Open Secondary Interventions after Endovascular Abdominal Aortic Aneurysm Repair. Manuscript submitted
  • Chaar, C.I., Hirsch S.A., Cwenar, M., Rhee, R.Y., Chaer, R.A., Abu-Hamad, G., Dillavou E.D. Expanding the role of Endovenous Laser Ablation (EVLT): Results in Large Diameter, Small Saphenous and Anterior Accessory Veins. 2011 Jul;25(5):656-61
  • Makaroun MS, Ochoa Chaar CI. Should we treat type I endoleaks? Definitely. In Controversies and Updates in Vascular Surgery 2010. Editors:Becquemin JP, Alimi YS, Gerard JL. Edizioni Minerva Medica.Torino 2010. PP 279-82
  • McGillicuddy E.A., Chaar C.I., Flynn C., Villalona G., Longo W.E. Cologastric fistula with a foreign body in a patient with Crohn's disease. Yale J Biol Med. 2010 Sep;83(3):113-7.
  • Chaar, C.I., Wexelmann, B., Zuckerman, K., Longo, W.E. Intussusception of the Appendix: Comprehensive Review of the Literature. Am J Surg. 2009 Jul;198(1):122-8.
  • Chaar, C.I., Bell, RL., Duffy, TP., Duffy AJ. Guidelines for safe surgery in patients with systemic mastocytosis. Am Surg. 2009 Jan;75(1):74-80.
  • Ochoa Chaar, C.I., Fitzgerald, T.N., Dewan, M., Huddle, M., Perkal, M., Muhs, B.E., Dardik, A. EVAR is associated with less malnutrition than open AAA repair. Am J Surg. 2009 Nov; 198(5):623-7.
  • Chaar, C.I., Attanasio, P., Detterbeck, F. Disruption of the costal margin with transdiaphragmatic abdominal herniation induced by coughing. Am Surg 74 (4): 350-3, 2008.
  • Safieh-Garabedian, B., Ochoa-Chaar, C.I., Poole, S., Massaad, C.A., Atweh, S.F., Jabbur, S.J. and Saade, N.E. Thymulin reverses inflammatory hyperalgesia and modulates the increased concentration of proinflammatory cytokines induced by intracerebroventricular endotoxin injection. Neuroscience, 121: 865-873, 2003.
  • Massaad, C.A., Ochoa-Chaar, C.I., Jabbur, S.J., Safieh-Garabedian, B. Atweh, S.F. Upregulation of pro-inflammatory cytokines and nerve growth factor by intraplantar injection of capsaicin. Journal of physiology 545: 241-53, 2002

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