cardiovascular risk

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Chapter 27:  Evaluation, Risk Assessment &  Anesthesia for Cardiovascular Procedures

 

 

  •   Rationale for Concern:
    •  Vascular surgery is unique since vital organs may be completely deprived of their blood supply during surgery
    •  Highest  surgical mortality/morbidity is associated with vascular procedures
  •  Basis for morbidity/mortality associated with vascular surgery:
    1.  myocardial failure
    2.  myocardial ischemia
    3.  myocardial infarction
Surgical Procedures of Special Concern
Coronary bypass surgery Carotid vessel surgery Aorta surgery Major vascular surgery (supplying viscera/limbs)
  •  Pathophysiology: Coronary Artery Disease (CAD): The major cause of death in the United States
    •  Major risk factors in development and progression of atherosclerosis
      •  obesity
      •  tobacco use
      •  inactivity
    • Atherosclerotic lesions:
      • Fatty streaks
      •  Atheromatous plaques

"Aorta of a  young man.  It shows fatty streaks (elongated, flat, yellow lesions) and early fibrotic plaques, (broader and slightly elevated lesion)"(Left); Fatty streak of the aorta, histology Lipid containing cells (probably macrophages) are present in the intima of the aorta"(Right)-- courtesy of Jim Fishback, M.D., Department of Pathology, University of Kansas Medical Center

  •  Atheromatous plaques 
    • Reduces vessel diameter (luminal diameter)
    • Location of thrombosis, vessel wall calcification, vessel wall weakening 
    •  Clinical Consequences:
      • Occlusion
      • Vessel rupture
      • Aneurysmal dissection
    •   Distribution of atheromatous plaques: Factors--
      • Regions of disturbed blood flow; shear stresses
        • Lower descending aorta {ostia of the major branches}
        • First  3 inches of coronary arteries
        • Descending aorta
        • Internal carotids
        • Circle of Willis
        • Leg arteries
    •  Atherogenesis: multistep process probably involving: (a)  Dysfunctional endothelial cells, (b) induction of growth & coagulation factors, (c) macrophage & monocyte involvement in injury response)
      •  Risk factors (hypolipidemia, smoking, hypertension) affect multiple steps
      •  Hypertension promotes endothelial damage
      •  Abnormal flow/perfusion characteristics increase atherosclerosis development
      •  Hyperlipidemia promotes atherosclerosis

"Aneurysm of the aorta with a thrombus.  On opening of the aneurysm at autopsy, a mural thrombus was found partially occluding the lumen of the blood vessel." (Left);"Severe atherosclerosis of the aorta..  The intima of the aorta is eroded and ulcerated, appears rough, and is totally covered with clotted blood." (Right)-- courtesy of Jim Fishback, M.D., Department of Pathology, University of Kansas Medical Center

"Atherosclerosis of the order with narrowing and thrombosis.  Narrowing of the aorta is one of the common complications of atherosclerosis.  Thrombi overlying the ulcerated endothelium contributes to the narrowing of the lumen and may completely block the blood flow through the narrow part of the blood vessel."-- courtesy of Jim Fishback, M.D., Department of Pathology, University of Kansas Medical Center

  • Prominent risk factors for atherosclerosis: hypercholesterolemia, tobacco smoking, hypertension

    •  Hypercholesterolemia:  reduction in cholesterol concentration may slow/reverse atherosclerosis

      •  Individuals with lower cholesterol exhibited reduction in all-cause mortality {30-year Framingham subject follow-up}

      •  Significant lowering of total cholesterol & low-density lipoproteins (LDL) cholesterol associated with:

        • reduced total mortality (33%)

        • reduced coronary  mortality (42%)

        • reduced non-fatal coronary infarctions (33%) reduced requirement for coronary revascularization (30%)

    •  Hypertriglyceridemia:

      •   Possible independent risk fact for coronary disease

        •  hypertriglyceridemia--independent risk factor in women {Framingham study}

      •   Hypertriglyceridemia associated with reduced high-density lipoproteins levels (HDL levels)

    •  Tobacco Smoking: Cardiovascular systemic effects

      •   increased sympathetic tone secondary to nicotine absorption

      •   increased platelet adhesiveness

      •   displacement of O2 by CO

      •   possible immunological reaction in vessel wall

      • Most preventable risk factor for cardiovascular disease

    •  Hypertension --major risk factor independent of gender, age groups, race

      • Frequency: 10%-20% (USA): elevated blood pressure

      • Hypertension has additive effects with respect to other risk factors

 

 

  • Primary Reference: Katz, J.,  Evaluation Risk Assessment of Patients with Vascular Disease in Principles and Practice of Anesthesiology (Longnecker, D.E., Tinker, J.H. Morgan, Jr., G. E., eds)  Mosby, St. Louis, Mo., pp. 201-218, 1998.

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