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Ischemic Heart Disease Metabolic 02 supply < Metabolic 02 demand

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general
unstable angina
chronic stable angina
myocardial infarction

general

Increased myocardial metabolic oxygen demand
-severe hypertension
-tachycardia
-severe aortic stenosis
-coronary artery vasosparm

Decreased myocardial metabolic oxygen supply
-anatomical obstruction
-severe hypotension
-hypoxemia
-severe aortic stenosis or aortic regurgitation

Coronary Artery Disease
-atherosclerosis is the most common cause of coronary artery disease
-approximately 1/3 of all deaths in the western society is attributed to CAD
-major casue of perioperative morbidity and mortality
- 5-10% incidence within the surgical patient population

Major risk factors for CAD
-hypertension
-diabetes mellitus
-hypercholestrolemia
-cigarette smoking
-male sex
-family history of heart disease

Other risk factors for CAD
-obesity
-history of CVA
-history of PVD
-anuerysm

Signs/symptoms
-angina
-myocardial ischemia
-myocardial infarction
-dysrhythmias
-ventricular dysfunction ---> "Ischemic Cardiomyopathy" when symptoms of CHF predominate

unstable angina
-abrupt increase in severity, frequency (x > 3 episodes/day), and duration of aninal attacks
-angina at rest
-new onset angina within the past 2 months with severe or frequent episodes x > 3/ day

abrupt increase in severity, frequency and duration usually reflects severe underlying CAD esp assoc. with ST seg changes
frequently precedes myocardial infarction

Pathophysiology
-plaque dissruption with platelet aggregation or thrombus
-vasospasm

Treatment
-approximately 80% of patients have critical stenosis of one or more arteries therefore require admission to CCU
Generally treated with unless contraindicated:
-anticoagulation: ( i.v heparin, asprin)
-vasodilation (nitroglycerin)
-beta blocker
-calcium channel blocker

chronic stable angina

Signs/symptoms
generally absent when atherosclerotic lesions are < 50 - 75% occlusion of the coronary artery
when coronary artery occlusion is approximately 70%, maximal compensatory dilation occurs
chest pain generally occurs when occlusion of the coronary artery exceeds 50-75%

Chest pain usually:
-substernal
-exertional
-radiating to the neck or arm
-relieved by rest or nitroglycerin

Variation of associated chest pain:
-epigastric pain
-back pain
-neck pain
-silent: no pain ex. diabetic patients

At rest: coronary blood flow is usually adequate therefore oxygen supply >/= oxygen demand
With activity: coronary blood flow is usually inadequate therefore oxygen supply < oxygen demand

ex of decreased supply: vasospasm
ex of increased demand: increased metabolic demand (stress, physical activity, fever)

Variable Threshold: patients who have a variable level of activity or varying level of emotional stress
ex. Printzmetal Angina

Fixed Threshold: patients who have a relatively fixed level of activity or emotional stress
ex. Classic Exertional Angina

Treatment (5 fold)
-correction of coronary risk factors (smoking, high cholesterol intake, DM)
-lifestyle modification (eliminate stress and improve exercise tolerance)
-correct underlying medical problems (HTN, anemia, thyrotoxicosis, fever, infection, adverse drug effects)
-drug therapy (nitrates, beta blockers, calcium channel blockers, other)
-surgical correction of coronary lesion (percutaneous angioplasty +/- stenting, CABG)

Prognosis
overall prognosis depends on:
-number and severity of coronary artery obstruction/s
-ventricular function