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Common Congenital Heart Lesions - page 64 / 126

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Endothelial Cell Dysfunction: Æ problems with inappropriate vasoconstriction and loss of antithrombic properties

  • Inappropriate vasoconstriction

    • o

      With dysfunctional endothelium, release of NO (and others) is impaired

      • o

        This shifts the balance over to the vasoconstrictors

      • o

        Results in a decrease in coronary blood flow

      • o

        In some patients with no evidence of plaque formation but with big risk factors for CAD, impaired vasodilation can be noted

        • Thought that endothelial dysfunction may happen early in the atherosclerotic process

      • o

        When platelets being to aggregate after plaque disruption, they release metabolites (5-HT, ADP) that stimulate release of NO.

        • If NO release is impaired, then vasoconstriction predominates, and flow is further restricted.

  • Platelet aggregation

      • o

        Endothelial cells release substances that interfere with platelet aggregation

      • o

        The release of these substances is reduced with endo dysfunction

Consequences of Ischemia

DyspneaÆ transient reduction in systolic contraction = LV diastolic pressure, increased LA pressure, pulm congestion via pulm veins PainÆ accumulation of metabolic products activates pain receptors (C7-T4) Arrhythmias MOSTLY DETERMINED BY SEVERITY AND DURATION OF IMBALANCE. Options:

  • o

    Irreversible myocardial necrosis

    • o

      Rapid full recovery

    • o

      Prolonged contractile dysfunction without necrosis, recovery possible

“stunned myocardium”= reversible , likely to be response to severe ischemia that just falls short of irreversible necrosis but only gradually

  • o

    “hibernating myocardium”

    • results from multivessel CAD

    • persistently reduced blood supply

    • readily reversed when blood flow is improved

This stuff is important in deciding on a treatment plan. In imaging, we can now tell the difference between these types of tissues. Since hibernating or stunned myocardium would respond well to surgery, but necrotic tissue would not, we would make a decision about surgery based on the imaging studies.

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