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Abdominal Aortic Aneurysm
- 1. Shibu Chacko abdominal aortic aneurysms
- 2. • Definition • Diameter > 1.5 times normal vessel diameter (Aorta>3cm) • Sex • 1.2% male deaths, 0.6% female deaths • Age • men start at 50 yrs, peak incidence 80 yrs • female start at 70 yrs, peak incidence 90 yrs aortic aneurysms 1
- 3. aortic aneurysms 2 • Family history • 15-20% of patients with AAA have a first degree relative with AAA: compared to 2% of controls • Incidence • increasing death rate from rupture over last 30yrs (increasingly elderly popln, [65+yrs to double by 2025]) • 5% men over 65yrs have AAA (screening)
- 4. aneurysm
- 5. aneurysm histology Lumen Thrombus Lumen Intima atherosclerotic Media thin fibrous replacement of SMC disrupted elastic fibres reduced elastin content increase in collagen Adventitia thickened increase in collagen inflammation Normal Aneurysm Endothelium/Intima Media Adventitia
- 6. Aneurysm Ehlers Danlos IV mutation Type III collagen Marfans mutation Fibrillin Hypertension increase in pressure Smoking damage to arterial wall Gelatinase Elsatase Metalloproteinases degrade elastin Genetic EnvironmentBiomechanical Strength Compliance Elastance causes of aortic aneurysm
- 7. aneurysm rupture • Occurs when the tension in the aneurysm wall exceeds the tensile strength of the aneurysm wall • Depends on : – size diameter, wall thickness (Laplace) – shape symmetric, asymmetric – pressure hypertension, Bernouilli – material loss of elastin, increase in collagen
- 8. aneurysm rupture Overall mortality 80% – 60% die at home – 40% reach hospital operative mortality 30-60% Elective repair mortality 2-6% – age < 60 yrs 3.3% – age > 80 yrs 12%
- 9. annual risk of rupture Size matters – < 5.5cm: low risk 1% per year – 5-6cm: 5-10% per year – >7cm: 20%
- 10. indications for repair • All symptomatic aneurysms Back pain & tender aneurysms • Size >6cm: poor risk patient >5cm: good risk patient • Expansion >1cm/year • All saccular aneurysms • Contraindications limited life expectancy severe irreversible CAD dementia • All symptomatic aneurysms Back pain & tender aneurysms • Size >6cm: poor risk patient >5cm: good risk patient • Expansion >1cm/year • All saccular aneurysms • Contraindications limited life expectancy severe irreversible CAD dementia
- 11. clinic • Symptomatic 40% – Back pain – Pulsatile mass – Inflammatory • back pain, malaise, ureteric obstruction, raised ESR – Fistula: aorto-enteric, aorto-caval • Asymptomatic 60% – Screening – Ultrasound
- 12. preoperative tests • Ultrasound – measures size • CT scan – defines anatomy and extent • 95% infrarenal; 5% suprarenal • 12% also have thoracic aortic aneurysm • Cardiac, lung and renal function
- 13. CT scan of aortic aneurysm
- 14. 3D reconstruction from CT scan
- 16. preoperative evaluation 1 Risk factors Age > 70 Cardiac Diuretics / CCF P.H. ventricular arrythmia Q waves on ECG Angina Diabetes Renal failure
- 17. operative management 1 • Epidural catheter improves pulmonary function • Feel pulses • DVT prophylaxis Heparin , compression boots • Drape Nipples-Femorals • Incision Midline Transverse Oblique retroperitoneal
- 18. incision
- 19. operative management 2 • Laparotomy • Expose aneurysm neck ( ? ligate L renal vein) • Expose iliacs • Administer heparin • Clamp iliac arteries avoiding iliac veins • Clamp aorta slot the neck
- 20. laparotomy
- 21. operative management 3 • Open aneurysm sac kit ready • Remove thrombus • Ligate lumbar arteries, clamp IMA 2/0 silk • Proximal anastomosis cont Surgilene • Check integrity of anastomosis pledget sutures • Distal anastomosis flush & check • Blood flow to one internal iliac maintain BP
- 22. aortic clamp
- 23. lumbar vessels
- 24. anastomoses
- 25. operative management 4 • Check perfusion of colon IMA Carrell patch • Check femoral pulses • Check for haemorrhage • Cover prosthesis with sac & peritoneum
- 26. tube graft
- 27. closing the sac
- 28. complications of aneurysm repair 1 Cardiac 15% (MI 2-8%) Pulmonary 8-12 % (Pneumonia 5%) Renal function 5-12% (Dialysis1-6%) DVT 8% Bleeding 2-5% Stroke 1%
- 29. complications of aneurysm repair 2 Ureteric injury <1% Leg ischaemia 1-4% Colon ischaemia 1% Wound infection 5% Spinal cord ischaemia 1%
- 30. late complications of aneurysm repair Anastomotic false aneurysm 0.2% aorta 1.2% iliac 3% femoral Graft infection 0.5% aortoiliac Aortoenteric fistula 0.9% Graft Thrombosis Rare Other aneurysms 5%
- 31. prognosis after aneurysm repair 5 year survival 70% 10 year survival 40% Late deaths: cardiac 44% cancer 15% rupture another aneurysm 11% stroke 9% pulmonary 6%
- 33. endovascular repair 2 small groin incisions
- 36. stents deployed
- 40. aneurysm formation • Failure of elastin (age, BP, genetic) • Aneurysm formation • Tensile load taken by collagen • Biomechanical properties of collagen/fibrillin vary with genotype • Influence on expansion and rupture
- 41. 30 day mortality Cause Elective Rupture Cardiac 58% 20% Pulmonary 6% 3% Renal 4% 9% Colon infarction 1% 9% Haemorrhage 0% 18% MSOF 1% 35% Other 24% 6%
- 42. preoperative evaluation 2 Risk factor Cardiac Investigation complication Low risk 0 0% None Intermediate 1-2 3% Non invasive negative 30% Non invasive positive High 3+ 50% Coronary angiogram
- 43. physics
- 44. physics: aortic wall tension Law of Laplace T= P x r For a given pressure the tension in the aortic wall is proportional to the radius of the aorta P r T P r T
- 45. physics: blood flow If blood flow (mls/min) is constant, the velocity of blood must increase in a narrower vessel A B A B 1s 1s
- 46. physics:energy in blood 1 Bernouilli’s equation The total fluid energy = kinetic energy + potential energy velocity pressure
- 47. Conservation of energy physics:energy in blood 2 Aorta Aneurysm Pressure Velocity Slower flowing blood in the aneurysm exerts a greater pressure