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Cardiovascular physiology. Dr James Ker
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2 scenario`s in cardiology: Systemic diseases affecting the cardiovascular system. Systemic diseases affecting the cardiovascular system. Primary cardiovascular diseases. Primary cardiovascular diseases.
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How can these diseases affect the cadiovascular system ? Components of the cardiovascular system: Myocardium: myocarditis, cardiac failure etc Myocardium: myocarditis, cardiac failure etc Valves: Stenosis, incompetence etc Valves: Stenosis, incompetence etc Electrical system: Dysrhythmias. Electrical system: Dysrhythmias. Vessels: Arteries, veins, lymphatic vessels. Vessels: Arteries, veins, lymphatic vessels.
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Physiological disturbances: Disturbances in the following may occur: Disturbances in the following may occur: Blood pressure Blood pressure Cardiac rhythm Cardiac rhythm Valvular function Valvular function Cardiac systole and diastole Cardiac systole and diastole Blood flow Blood flow
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Blood pressure: BP = Cardiac output (CO) x peripheral vascular resistance (PVR) BP = Cardiac output (CO) x peripheral vascular resistance (PVR) 3 components of blood pressure: 3 components of blood pressure: Systolic component Systolic component Diastolic component Diastolic component Mean arterial pressure Mean arterial pressure
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BP = 120/80 mmHg BP = 120/80 mmHg Mean arterial pressure = (S + 2D)/3 or Mean arterial pressure = (S + 2D)/3 or D + 1/3 PP D + 1/3 PP Pulse pressure=S – D (120-80=40 mmHg) Pulse pressure=S – D (120-80=40 mmHg)
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Cardiac output: CO = Stroke volume x heart rate CO = Stroke volume x heart rate Thus: Thus: 2 ways to increase CO: SV vs CO Determines systolic BP Systolic vs diastolic HT Normal CO: 5L/min Cardiac index=CO corrected for body surface area
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Causes of increased CO: Fever Fever Anaemia Anaemia Hyperthyroidism Hyperthyroidism Pregnancy Pregnancy Exercise Exercise Etc.. Etc..
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Presents as: Systolic HT with: Systolic HT with: ↑ pulse pressure ↑ pulse pressure Stroke volume: Volume of blood pumped by ventricle during systole (70 ml at rest) Stroke volume: Volume of blood pumped by ventricle during systole (70 ml at rest)
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Physiological control of CO: Preload: Venous filling Preload: Venous filling Afterload: BP against which LV must expel stroke volume Afterload: BP against which LV must expel stroke volume Inotropy: Strength of myocardial contraction. Starling`s law, catecholamines Inotropy: Strength of myocardial contraction. Starling`s law, catecholamines
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Physiological control of heart rate: Intrinsic: SA node Intrinsic: SA node Extrinsic: Extrinsic: Hormonal: thyroid, catecholamines Neurological: Autonomic nervous system Fever, electrolytes
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Peripheral vascular resistance: Determined by diameter of peripheral arteries. Determined by diameter of peripheral arteries. Determines diastolic blood pressure Determines diastolic blood pressure
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Control of PVR: Hormonal: AT II, endothelins, NO, bradykinin, catecholamine etc Hormonal: AT II, endothelins, NO, bradykinin, catecholamine etc Neurological: Autonomic nervous system Neurological: Autonomic nervous system Myogenic/Local. Myogenic/Local.
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The ECG: Einthoven`s trangle Einthoven`s trangle Einthoven`s law Einthoven`s law
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Einthoven`s triangle: I II III +-+- ---- +
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Einthoven`s law: Lead II = Lead I + Lead III Lead II = Lead I + Lead III Standard limb leads: I, II, III Standard limb leads: I, II, III Lead I: connects 2 arms Lead I: connects 2 arms Lead II: connects right arm with left leg Lead II: connects right arm with left leg Lead III: connects left arm with left leg Lead III: connects left arm with left leg
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aV leads: Limb leads are bipolar Limb leads are bipolar Unipolar limb leads=aV leads: aVR, aVL and aVF Unipolar limb leads=aV leads: aVR, aVL and aVF
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Precordial (V) leads: V1: Just to the right of the sternum in the 4`th intercostal space. V1: Just to the right of the sternum in the 4`th intercostal space. V2: Just to the left of the sternum in the 4`th intercostal space. V2: Just to the left of the sternum in the 4`th intercostal space. V3: Halfway between V2 and V4 V3: Halfway between V2 and V4
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V4: Left midclavicular line in the 5`th intercostal space V4: Left midclavicular line in the 5`th intercostal space V5, 6: 5`th intercostal space in anterior and midaxillary line respectively V5, 6: 5`th intercostal space in anterior and midaxillary line respectively
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Physiological use of the ECG: Rhythm: Sinus vs other Rhythm: Sinus vs other Chamber thickening: Atrial and ventricular hypertrophy Chamber thickening: Atrial and ventricular hypertrophy Damage: Endocardial, myocardial, pericardial Damage: Endocardial, myocardial, pericardial Info on systemic conditions: Hypothermia, electrolyte disturbances, pH disturbances Info on systemic conditions: Hypothermia, electrolyte disturbances, pH disturbances
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Rate, complexes, intervals: P-wave: Atrial depolarization P-wave: Atrial depolarization QRS-complex: Ventricular depolarization QRS-complex: Ventricular depolarization T-wave: Ventricular repolariation T-wave: Ventricular repolariation
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