Myocardial Infarction: Findings on History

Yu Yan – MI Findings on History – FINAL.pptx –
Myocardial Infarction: Findings on HistoryLegend:Published January 30, 2013 on www.thecalgaryguide.comMechanismPathophysiologySign/Symptom/Lab FindingComplicationsAuthor: Yan YuReviewers:Sean SpenceTristan JonesNanette Alvarez** MD at time of publication Systolic function(necrotic myocardium cannot contract as well)Reflexive ? in sympathetic activity (to try to maintain CO)Clammy skin? stroke volume (SV), ? cardiac output (CO)Myocardial infarction (tissue necrosis)Note: Myocardial ischemic pain may differ between patients, but recurrences usually feel the same in any given patient.Generalized vasoconstrictionVasoconstriction of skin arteriolesCool skinLocal myocardial inflammationIrritation of T1-T4 sympathetic afferentsIrritation of cardiac branches of vagus nerveSignals enter spinal cord, mixes with T1-T4 dermatomesCrushing, Diffuse “Pain” or “tightness”: Often retrosternal, with radiation to shoulder, neck, and inner aspect of both arms (R > L).(Onset: often at rest; crescendo)Activation of reflexive vagal responses (listed below)Weakness, dizziness, nausea, vomitingInflammatory mediators irritates nerves innervating the heart (the cardiac plexus)Cytokines act on hypothalamic T0 regulatorMild fever? Sweating (diaphoresis)Inflammatory cytokines can spread systemicallyBrain perceives nerve irritation as pain coming from T1-T4 dermatomesBlood backs up from the LV, into the left atrium and eventually accumulates in the pulmonary vasculatureHigh pulmonary venous blood pressure forces fluid out of capillaries, into pulmonary interstitium & alveoliRespiratory muscles work harder to ventilate lungsSoggier lung interstitium ? lung complianceDyspnea(Shortness of breath)Fluid compresses airways, ? resistance to airflow
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