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Cardiac Output & Heart Rate introduction
- 1. Cardiac Output, ECG& Shock DEPARTMENT OF PHYSIOLOGY Shweta kanwar
- 2. Learning Objectives • Whatis cardiac output ? • Measurement of cardiac output • Heart rate & its regulating factors • Normal ECG • Shock
- 3. Cardiac Output What makesthe heart a good pump?
- 4.
- 5. What Is CardiacOutput? •Cardiac Output •Amount of blood pumped out by each ventricle per minute = 5 to 6 lit /min A measure of cardiac performance Stroke volume Amount of blood pumped by each ventricle per beat = 70ml Heart Rate Cardiac output = Stroke Volume x Heart Rate
- 6. CARDIAC OUTPUT CO =SV X HR cardiac output = stroke volume X heart rate (ml/minute) (ml/beat) (beats/min) • Average heart rate 70 bpm • Average stroke volume = 70-80 ml/beat • Average cardiac output = 5000 ml/minute • Cardiac output varies widely with the level of activity of the body. Cardiac output = Stroke Volume x Heart Rate
- 7. Factors affecting cardiacoutput • Heart rate - When HR ↑es - CO also ↑es. Any factor which changes heart rate will also changes cardiac Output. • SNS has positive Chronotropic effects , PNS has negative Chronotropic effects • Force of contraction of heart - When the force of contraction of the heart ↑es, stroke volume will ↑es. Therefore cardiac output will increase. • Blood volume - When blood volume ↑es cardiac output ↑es. • Venous return- Increased venous return also increases CO.
- 8. Factors affecting cardiacoutput CO = SV X HR cardiac output = stroke volume X heart rate (ml/minute) (ml/beat) (beats/min) Stroke Volume:- • Volume of blood pumped out of each ventricle per beat • 70 ml in a healthy human SV EDV – ESV Factors affecting affecting SV: • Heart size • Gender • Fitness levels • Contractility • Duration of contraction • Preload (EDV) • Afterload (PR) Factors affecting HR: • Autonomic innervation • Hormones Fitness levels • Age
- 9. When does CardiacOutput Change? • All situations where tissue demand for blood changes i.e. change in metabolism • Exercise • Pregnancy • After a meal • Sleep • Usually always by changes in stroke volume & heart rate Cardiac output = Stroke Volume x Heart Rate
- 10. Factors influencing CO •Physiological:- • Age - More in adults than in children because blood volume is more • Gender - CO is more in male than females • Surface area – Increase CO • Emotions - CO increases during emotional expressions • Pregnancy - CO increases during pregnancy. • Muscular exercise - CO increases during exercise • Sleep • Pathological:- • Hyperthyroidism, Anemia, Fever • Hypovolemia • Hemorrhage • Myocardial infarction
- 11. How Is CardiacOutput Distributed? Organs Blood Flow Blood Flow ml/Min % GIT & Liver 1400 24 Skeletal Muscles 1200 21 KIDNEY 1100 19 Brain 750 13 Skin 500 9 Heart 250 4 Other organs 600 10 Total organs 5800 100 Most tissues receive blood in proportion to their metabolic demand
- 13. How Is ItMeasured? • Direct:- Cannula e.g. experimental animals • Indirect:- • Fick’s principle • Indicator / Dye dilution method • Thermal dilution method • Radioactive nucleotides • Echocardiography + Doppler method • Ballistocardiography – Not practically used
- 14. Measurement of CardiacOutput Fick’s principle Blood flow=Amt. of O2 absorption from lungs per min./A-V O2 CO = 200/40 = 5 lit/min measured by collecting expired air Arterial blood sample Mixed venous blood sample
- 15. Disadvantages & Advantages •Disadvantages • Invasive • Slow • Steady state required • Advantages • Quite accurate
- 16. Other Methods • Indicatordilution method • Dilution of a measured volume of dye • Thermal dilution method • Dilution of a bolus volume of cold saline • Radioactive nucleotides
- 18. THERMODILUTION PRINCIPLE–same as indicatordye dilution method except cold saline is used. Resultant change in blood temperature in pulmonary artery is determined. Thursday, November , 18, 2024
- 19. Other Methods • Echocardiographywith Doppler • Measure velocity of flow in aorta • Measure volume of the flow through valves • Measure stroke volume • Difference in end-diastolic and end-systolic volumes
- 20.
- 21. CARDIAC OUTPUT STROKEVOLUME Arterial Pressure Filling Pressure Atrial Stretch Parasympathetic Nerve activity End- diastolic volume HEART RATE Sympathetic Nerve activity End- systolic volume = x Summary
- 22.
- 23. Heart Rate • Numberof heart beats per minute. • Normal Value: 60 – 100 beats / minute (average 72) in adults • < 60 is called: Bradycardia • > 100 is called: Tachycardia
- 24. Factors affecting Heartrate • I. Age • II. Gender • III. Body temperature • IV. Disease • V. Drugs • VI. Emotions • VII. Exercise
- 25. I. Age • Afterbirth, as age ↑ vagal tone ↑ and HR ↓, but in old age HR is slightly higher due to fall in vagal tone • Fetal HR : 140-150 beats/min • At Birth beats/min : 130 – 140 beats/min • Adults : 70-80 beats/min • Old age : up to 100 beats/min
- 26. II. Gender • HRis slightly higher in females as compared to males. •III. Body temperature • HR is directly related to the body temp • ↑ Temp - ↑ HR • ↓ Temp. - ↓ HR
- 27. IV. Disease • THYROTOXICOSIS:It is associated with ↑ resting HR V. Drugs • Drugs like epinephrine ↑HR VI. Emotions • like Excitement, fear, anger etc. are associated with tachycardia • Sudden shock etc. are associated with bradycardia
- 28. VII. Exercise • HRincreases in linear pattern with the severity of the exercise because : • Increase in sympathetic activity • Decrease in vagal tone • Increase in Release of catecholamine's and thyroxine • Change in blood chemistry (hypoxia and hypercapnia)
- 29. Control of Heartrate 1. Neural regulation • Autonomic nervous system • Reflex regulation • Higher centers 2. Hormoral regulation
- 30. Neural regulation –Autonomic Nervous System • Parasympathetic nervous system: - Right Vagus innervate SA node, Left Vagus innervate AV node - With dominating effect of vagal tone on SA node HR would be 72 beats/min, without domination HR would be 110 beats/min - On stimulation - ↓ in hear rate
- 31. Neural regulation –Autonomic Nervous System • Sympathetic nervous system: -Spinal nerves from lower cervical segment & upper thoracic segments Inhibit the vagus nerve activity. -On stimulation - ↑ in heart rate
- 32. Neural regulation –Reflex regulation •Baroreceptor Reflex: 个B.P. ― ↑HR •Chemo receptor Reflex: ↑ pco2 ― 个HR •• Bain bridge Reflex : ↑ Blood volume ― 个HR
- 33. Neural regulation –Higher centers •Stimulation of motor cortex, frontal lobe, thalamus - ↑HR •↑HR in emotional status is due to stimulation of limbic system.
- 34. Hormoral regulation •Thyroxin &catecholamine’s → ↑HR
- 35.
- 36. Electrocardiography ECG /EKG ◼ Twocommon abbreviations for : ◼ ECG - Electrocardiogram ◼ EKG – Electrokardiogram - German language ◼ The ECG records the electrical activity of the heart. ◼ Heart is a generator & body is a volume conductor ◼ Electrical activity of the heart is sensed by echocardiography. ◼ Einthoven willem is known as father of ECG
- 37. ECG • Electrocardiograph –the machine by which the electrical activities of heart are recorded. • Electrocardiographic Paper- used for recording ECG is called ECG paper.
- 38. Clinical Importance • Ionicchanges • Ischemia, infarction • Arrhythmias • Conduction defects • Hypertrophy • Damage to cardiac muscles
- 39. Electrophysiology ◼ If waveof depolarization spreads toward the recording electrode-positive deflection. ◼ If wave of depolarization spreads away from recording electrode, a negative deflection
- 40. Leads • ECG measuresthe potential difference between 2 points: • LEADS :- Combination of 2 wires & their electrodes to make a complete circuit with electrocardiograph • Nature of electrodes :- a) Exploring b) Indifferent • Exploring electrode :- Records potential at point of application • Indifferent electrode :- Kept at zero potential (high resistance)
- 41. Classification of leads •a) Unipolar – one electrode is exploring & another one is indifferent : • Augmented limb leads (aVR, aVL, aVF ) • Chest leads ( V 1 to V 6 ) • b) Bipolar – both electrodes are exploring • standard limb leads I, II , III • Total 12 ECG Leads.
- 42. Normal ECG PQRST wavesrepresent one complete cardiac cycle
- 43. Electrophysiology ◼ Isoelectric lineWhen myocardial muscle is completely polarized or depolarized. ◼ P wave represents depolarization of atria - has amplitude of ≤ 0.25 mV • Repolarization of atria not normally detectable on an ECG • Excitation of bundle of His and bundle branches occur in middle of PR interval • QRS complex reflects depolarization of ventricles - Q& S waves are downward deflections • T wave reflects repolarization of ventricular muscles
- 44. Circulatory Shock Generalized inadequacy of bloodflow or Inadequate tissue perfusion
- 45. Pump-Heart Pipe -vessels Fluid -blood What Is Needed For Perfusion? How Can Perfusion Fail ? • Inadequate fluid - • Vascular Vasodilatation • Obstruction to blood flow Cardiogenic Hypovolemic Obstructive Distributive Inadequate pumping of heart
- 46. Shock Neurogenic Anaphylactic Septic Hypovolemic •In most typesof shock CO & arterial pressure decreases •Shock is a life-threatening condition of circulatory failure. How Is Shock Classified?