CORONARY ARTERY DISEASE (CAD)

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CORONARY ARTERY DISEASE (CAD)

• DR ZAHOOR ALI SHAIKH

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CORONARY ARTERY DISEASE (CAD)

• What is Coronary Artery Disease?
• CAD is heart disease due to impaired coronary
  blood flow.

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CORONARY ARTERY DISEASE (CAD)

• CAD can cause
• - Myocardial ischemia or Angina called
• Ischemic heart disease (IHD)
• - Myocardial infarction or Heart attack
• - Conduction effect
• - Heart failure
• - Sudden death

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• First we will discuss normal coronary circulation
  and factors affecting it.
• Then we will discuss Ischemic heart disease.

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CORONARY CIRCULATION

• Coronary vessels travel across the surface of
  heart under epicardium.
• Heart is supplied by TWO CORONARY arteries
• 1- Left coronary artery---(LCA)
• 2- Right coronary artery---(RCA)
• These coronary arteries arise at the root of the
  aorta.

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• Coronary artery their branches
• Left coronary artery is about 3.5cm and then
  divides into
• LCA---- -Lt Anterior Descending (LAD)
• -Circumflex Artery
• Right Coronary Artery
• RCA ---- -Marginal Artery
• -Posterior descending branch

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LEFT CORONARY ARTERY

• LAD--- Supplies anterior and apical parts of
  heart ,and Anterior 2/3rd of interventricular
  septum.
• Circumflex branch-- supplies the lateral and
  posterior surface of heart.

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• Right coronary artery(RCA) supplies
• Right ventricle
• Part of interventricular septum (posterior 1/3rd)
• Inferior part of left ventricle
• SA Node
• AV Node

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• Diagram of coronary circulation

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• Venous return of Heart
• Most of the venous blood return to heart
  occurs through the coronary sinus and anterior
  cardiac veins, which drain into the right atrium

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• Blood flow to Heart during Systole Diastole
• During systole when heart muscle contracts it
  compresses the coronary arteries therefore blood
  flow is less to the left ventricle during systole
  and more during diastole.
• To the subendocardial portion of Left ventricle
  it occurs only during diastole

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• Coronary blood flow to the right side is not much
  affected during systole.
• Reason---Pressure difference between aorta and
  right ventricle is greater during systole .

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• CORONARY BLOOD FLOW DURING SYSTOLE AND DIASTOLE

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• Effect of Tachycardia on coronary blood flow
• During increased heart rate, period of
  diastole is shorter therefore coronary blood flow
  is reduced to heart during tachycardia.

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• As we know blood flow to subendocardial surface
  of left ventricle during systole is not there,
  therefore, this region is prone to ischemic
  damage and most common site of Myocardial
  infarction.

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• Other causes of decreased blood flow to left
  ventricle
• 1-Aortic stenosis
• Reason---As left ventricle pressure is very
  high during systole, therefore, it compresses the
  coronary arteries more.
• 2-When aortic diastolic pressure is low,
  coronary blood flow is decreased

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CORONARY BLOOD FLOW

• Coronary blood flow in Humans at rest is about
  225-250 ml/minute, about 5 of cardiac output.
• At rest, the heart extracts 60-70 of oxygen from
  each unit of blood delivered to heart other
  tissue extract only 25 of O2.

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CORONARY BLOOD FLOW

• Why heart is extracting 60-70 of O2?
• Because heart muscle has more mitochondria, up to
  40 of cell is occupied by mitochondria, which
  generate energy for contraction by aerobic
  metabolism, therefore, heart needs O2.
• When more oxygen is needed e.g. exercise, O2 can
  be increased to heart only by increasing blood
  flow.

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• Factors Affecting Blood Flow to CORONARY ARTERIES
• -Pressure in aorta
• -Chemical factors
• -Neural factors
• NOTECoronary blood flow shows considerable
  Autoregulation.

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• Chemical factors affecting Coronary blood flow
• Chemical factors causing Coronary vasodilatation
  (Increased coronary blood flow)
• -Lack of oxygen
• -Increased local concentration of Co2
• -Increased local concentration of H ion
• -Increased local concentration of k ion
• -Increased local concentration of Lactate,
  Prostaglandin, Adenosine, Adenine nucleotides.
• NOTE Adenosine, which is formed from ATP during
  cardiac metabolic activity, causes coronary
  vasodilatation.

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• Neural factors affecting Coronary Blood Flow
• -Effect of Sympathetic stimulation
• -Effect of Parasympathetic stimulation
• Sympathetic stimulation
• Coronary arteries have
• Alpha Adrenergic receptors which mediate
  vasoconstriction
• Beta Adrenergic receptors which mediate
  vasodilatation

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• Sympathetic stimulation------Cont
• Effect of sympathetic stimulation in intact
  body---Epinephrine and Norepinephrine causes
  VASODILATATION.
• HOW ?
• But the Direct effect of sympathetic on Coronary
  arteries is VASOCOSTRICTION.
• WHY ?

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• Effect of Parasympathetic stimulation
• -Vagus nerve stimulation (Parasympathetic) causes
  coronary vasodilatation

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NEUTRIENT SUPPLY TO HEART

• Heart uses primarily free fatty acids and to
  lesser extent glucose and lactate for metabolism.

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CORONARY ARTERY HEART DISEASE

• ISCHEMIC HEART DISEASE (IHD) (ANGINA PECTORIS)
• MYOCARDIAL INFARCTION
• ANGINA PECTORIS
• THERE IS REDUCED CORONARY ARTERY BLOOD FLOW DUE
  TO ATHEROSCLEROSIS (CHOLESTROL DEPOSITION
  SUBENDOTHELIAL)

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• CAUSES OF IHD
• CIGARETTE SMOKING
• HYPERTENSION
• DIABETES MELLITUS
• INCREASED LIPIDS ( CHOLESTROL)
• OTHER FACTORS LACK OF EXERCISE, ANXIETY etc.

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• IHD
• IHD IS USED TO DESCRIBE DISCOMFORT IN THE CHEST
  DUE TO DECREASED CORONARY BLOOD FLOW (TRANSIENT
  MYOCARDIAL ISCHEMIA).
• PATIENT COMPLAINS OF TIGHTNESS OR PAIN IN THE
  MIDDLE OF CHEST (RETROSTERNAL) FOR FEW MINUTES.
  PAIN OFTEN RADIATES TO INNER SIDE OF LEFT ARM.
• PAIN IS PRECIPETED BY EFFORT AND RELIEVED BY REST.

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• MYOCARDIAL INFARCTION (MI)
• IT IS DUE TO OBSTRUCTION TO THE CORONARY BLOOD
  FLOW, ATLEAST 75 OF LUMEN OF CORONARY ARTERY IS
  BLOCKED BY THROMBUS.
• MI IS THE COMMEN CAUSE OF DEATH.

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Applied Aspect THE C A D.
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Electrocardiographic changes duringexercise
test. Upper trace significant horizontal ST
segment depression during exercise.
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• INVESTIGATIONS
• ECG
• CARDIAC ENZYMES e.g. CK, LDH, TROPONIN etc.
• ECHOCARDIOGRAPHY
• TREADMILL EXERCISE TEST
• THALLIUM STRESS TEST
• CORONARY ANGIOGRAPHY
• NOTE
• ECG CHANGES IN IHD
• ST DEPRESSION OCCURS IN ECG IN RESPECTIVE LEADS
• ECG CHANGES IN MI
• ST ELEVATION OCCURS IN ECG IN RESPECTIVE LEADS

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• TREATMENT
• CORONARY DILATORS E.g. NITRATES
• BETA-BLOCKERS
• ANGIOPLASTY (DILATE AREA OF CONSTRICTION)
• STENT
• BYPASS SURGERY

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Percutaneous transluminal coronary angioplasty
(PTCA). (a) Coronary angiography demonstrates a
severe stenosis in the proximal left anterior
descending artery. (b) During PTCA a soft
guidewire is passed across the stenosis and then
a balloon is expanded that dilates the stenosis.
(c) Post-PTC
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An intracoronary stent.
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THANK YOU