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Coronary circulationIschemic Heart Diseases

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Anatomic considerations

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Normal coronary blood flow The resting coronary blood flow= 225 ml/min

In strenuous exercise = increase three to four

folds.

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Phasic changes in coronary blood flow

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Epicardial Vs. subendocardial blood

flow

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Control of coronary blood flow

Metabolic regulation Nervous control

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Metabolic regulation Blood flow through coronary system is

regulated almost entirely by local arterial

vasodilatation in response to cardiac muscle

need for nutrients.

Increased contraction

Increase in rate of coronary

blood flow

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Oxygen demand.

Vasodilator substances:

Adenosine.

Potassium ions.

Hydrogen ions.

Carbon dioxide.

Bradykinin.

Prostaglandins.

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Indirect effect:

Symp stimulation HR & contractility

Rate of metabolism. activity local blood flow regulatory

mechanisms blood flow increases.

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Ischemic heart disease

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Ischemia: Lack of oxygen due to inadequate perfusion of

the myocardium, which causes imbalance

between oxygen supply and demand.

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Etiology of ischemic heart disease

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Coronary atherosclerosisThe most common cause of myocardial

ischemia.

Epicardial coronary arteries are the

major site.

Major risk factors:

Increase in LDL.

Decrease in HDL.

Cigarette smoking.Hypertension.

DM.

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Normal function of vascular

endothelium Local control of vascular

tone.

Maintenance of ananticoagulant surface.

Defense against

inflammatory cells.

Loss of these defenses

Inappropriate constriction.

Luminal clot formation.

Abnormal interactions with

blood monocytes &

platelets.

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Acute coronary occlusionThrombosis.Embolism.

Local spasm:Direct irritation of thesmooth muscle.Nervous reflexes.

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Location of the obstruction Influence the quantity of myocardial ischemia.

Determines the severity of the clinical

manifestations.

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Collateral

circulationWith sudden

occlusion.

With gradualdeveloping

atherosclerosis.

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Effects of ischemia Disturbances of myocardial functions:

Mechanical function.

Biochemical function.

Cell membrane function.

Electrical function.

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Effect of ischemia1)Mechanical function:

Failure of normal muscle

contraction & relaxation.

Ischemia of large portions ofventricle : left ventricular

failure.

Regional disturbances: Systolic stretch.

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Effect of ischemia2) Biochemical function:

Fatty acid cant be oxidized.

Glucose is broken down to lactate.

Reduced intracellular PH and ATP stores.

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Effect of ischemia3) Cell membrane function:

Leakage of potassium and uptake of sodium by

myocytes.

4) Electrical function:

ECG changes:

Repolarization abnormalities.

Transient ST segment depression.

Electrical instability:

Ventricular tachycardia and fibrillation.

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Ischemic heart disease

Stable angina

(chronic artery disease)

Acute coronary syndrome:

Unstable angina.

Acute MI.

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Stable anginaAn effort-related chest

discomfort.

Characteristics:

Heaviness.

Pressure.

Squeezing.

Smothering.

Choking pain.

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Stable anginaCauses:

CAD.

Other heart diseases:

Aortic valve disease.

Hypertrophic cardiomyopathy.

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Stable anginaHistory:

A man > 50 years.

A woman > 60 years.

Pain with physical & emotional

exertion.

Last to 5-10 min.

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Stable angina Radiating pain to the left shoulder, both arms,

back, interscapular region, root of the neck,

jaw and teeth.

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Stable anginaphysical examination:

Atherosclerotic disease at other sites.

Important risk factors:

Hyperlipidemia

DM.

Left ventricular dysfunction.

Conditions that may exacerbate angina: Anemia.

Thyroid disease.

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Stable anginaLaboratory examination:

Urine analysis ( DM and renal

disease).

Full blood count.

Measurements of:

lipids,.

Glucose. Createnine.

Hematocrite.

Thyroid function test.

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Stable anginaOther investigations:

Resting ECG: most important

baseline investigation.

Stress testing.

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Stable anginaOther investigations:

Coronary arteriography.

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Stable anginaManagement:

A careful assessment.

Identification and control of aggravating

conditions.

Identifications of high risk pts.

Application of treatment to improve life

expectancy.

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Stable anginaDrug therapy:

nitrates.

-adrenergic blockers.

Calcium antagonist.

Antiplatelet drugs.

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Unstable anginaAngina pectoris that is rapidly worsening.

Characteristics:

Occurs at rest, usually lasting >10 min.

Sever and of new onset.

Crescendo pattern.

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Unstable anginaCauses:

Shares commonpathophysiological

mechanisms with acute MI. Plaque rapture or erosion.

Dynamic obstruction (coronary spasm).

Rapidly advancing coronaryatherosclerosis.

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Unstable anginaHistory:

History of chronic stable angina.

May present as new phenomena.

Chest pain ( substernal region, radiating to the

neck, left shoulder and left arm).

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Unstable anginaPhysical examination:

Diaphoresis.

Pale cool skin.

Sinus tachycardia.

3rd or 4th heart sound.

Biochemical markers:

Troponin I & T.

CK.

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Unstable anginaECG changes:

12 lead ECG is mandatory.

ST elevation or depression.

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Unstable anginaManagement:

Urgent admission to hospital.

Bed rest.

Antiplatelet.

-blockers (atenolol).

IV or buccal nitrates.

Revascularization.

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Stableangina

Fixed stenosis.

Demand-led ischemia.

Predictable.

Exercise tolerance test.

Unstable angina

Dynamic stenosis.

Supply-led ischemia.

Unpredictable.

Clinical features.

ECG changes.

Biochemical markers.

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Myocardial infarction Occurs when there are zero flow or so

little flow that it cant sustain cardiac

muscle function.

Occlusive thrombus in a coronary

artery.

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Myocardial infarctionClinical features:

Pain (sever, last longer).

Breathlessness.

Vomiting.

Collapse.

Syncope.

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Myocardial infarction Investigations:

ECG:

Partial thickness infarctionST/T wave changes.

Transmural infarctionST elevation and Q waves.

Biochemical markers.

Chest radiography.

Cardiac US.

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Myocardial infarctionManagement:

Immediate access to hospital.

High-flow oxygen.

ECG monitoring. I.V analgesia and antiemetic.

Detect and manage acutecomplications:

Arrhythmia.

Ischemia.

Heart failure.

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Myocardial infarctionComplications of infarction:

Arrhythmia.

Ischemia.

Acute circulatory failure.

Pericarditis.

Embolism.

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Myocardial infarctionCauses of death in MI:

Decreased CO.

Damming of blood in the pulmonary or systemic

veins.

Fibrillation.

Rupture of the heart.

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Surgical treatment of coronary disease Aortic-coronary bypass surgery.

Coronary angioplasty.

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Aortic coronary bypass surgery

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Coronary angioplasty