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Common Congenital Heart Lesions - page 35 / 126

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  • Substances released from WBCs within the plaque itself that impair the integrity of the fibrous cap surrounding the plaque

  • Physical stresses (ie. physical activity or emotional stress)Æactivation of the Sympathetic NSÆincreases in HR, BP, & contractilityÆplaque rupture

*Note that most MIs occur in the morning because many of these stressors (ie. systolic BP, circulating epinephrine, & blood viscosity) are elevated during this time of the day.

  • Upon rupture, thrombus formation is triggered by:

    • Intraplaque hemorrhageÆvessel lumen narrowing

    • Turbulent blood flowÆplatelet activation

    • Release of TFÆactivation of coagulation (it’s VIIa’s cofactor!)

    • Exposure of subendothelial collagenÆplatelet activation

  • Platelet activationÆrelease of granular contents:

    • Facilitators of platelet aggregation (ie. ADP & fibrinogen)

    • Activators of coagulation (ie. Va)

    • Vasoconstrictors (ie. TXA2 & serotonin)

Dysfunctional Endothelium

  • Platelet-associated vascular response is impairedÆless release of NO & prostacyclinsÆless vasodilatation & less inhibition of platelet aggregation

  • Unopposed vasoconstriction (mediated by platelet-derived TXA2 & serotonin and thrombin within the forming clot)Æthrombus formation

*REFER TO FIGURE 7.3 (p. 160) FOR A SCHEMATIC OF THIS!!!

Consequences of Coronary Thrombosis (what type of ACS to expect)

  • Dependent upon the size and the extent of thrombus occlusion

    • Small: Typically non-occlusive & self-limited; may grow into the growing atheromatous plaque, resulting in its enlargement; does NOT result in ECG changes

    • Larger, Partially occlusive OR Transiently Totally Occlusive: Characterized by ST depression &/or inverted T waves (no Q waves!); typical outcomes are either UA or NSTEMI, which are distinguished from each other by the presence of myocardial necrosis (positive serum biomarkers for NSTEMI & negative for UA)

    • Larger, Totally Occlusive: Characterized by ST elevation (w/Q waves developing later) & positive for serum biomarkers

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