Objectives

• Recognize the importance of phasic changes in coronary blood flow

• Describe the factors affecting the coronary blood flow

• Recognize the clinical significance (IHD)

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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 FLOWWhy heart is extracting 60-70% of O2?• Because heart muscle has more

mitochondria, • When more oxygen is needed e.g.

exercise, O2 can be increased to heart only by increasing blood flow.

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Blood flow to Heart during Systole & Diastole

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Phasic changes in coronary bld flowEffect of cardiac muscle contraction

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• Coronary blood flow to the right side is not much affected during systole.

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• As we know during systole blood flow to subendocardial surface of left ventricle is almost not there, –therefore,

• this region is prone to ischemic damage and most common site of Myocardial infarction.

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• Effect of Tachycardia on coronary blood flow:

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Minimal requirements for normality include the following criteria:

(1) the dual aortic origin is from right and left coronary ostia (2) the course of the right coronary artery follows the right atrioventricular

groove (3) the course of the left coronary artery follows the left atrioventricular

groove and anterior interventricular Groove(4) the posterior descending branch originates from either theright or left coronary artery (5) the major coronary branches flow Epicardially(6) the coronary arteries terminate at the myocardialcapillary level

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• The left and right coronary arteries occasionally arise by a common trunk

• their number may be increased to three; the additional branch being the posterior coronary artery (which is smaller in size).

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Coronary artery dominance

• The artery that supplies the posterior descending artery (PDA) determines the coronary dominance.

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• right coronary artery (RCA) • circumflex artery (CX),• supplied by both

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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 SUBENDOCARDIALLY -- Plaque)

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RISK FACTORES OF IHD:

– CIGARETTE SMOKING– HYPERTENSION– DIABETES MELLITUS– INCREASED LIPIDS ( CHOLESTROL)– OTHER FACTORS: LACK OF EXERCISE,

ANXIETY etc.

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IHD:IHD IS 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 COMMON CAUSE OF DEATH.

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Applied AspectTHE C A D.

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INVESTIGATIONS:ECGCARDIAC ENZYMES e.g. CK, LDH, TROPONIN etc.ECHOCARDIOGRAPHYTREADMILL EXERCISE TESTTHALLIUM STRESS TESTCORONARY 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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CORONARY ARTERY BYPASS SURGERY

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Keep your USP flash awayAnd you can check our

presentation online

Thanks

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