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Module outline - Anatomy - Myocytes - Cardiac cycle - Haemodynamics & blood pressure - Coronary circulation - Capillaries One 2 One Medicine: Pre-clinical revision course One 2 One Medicine: Pre-clinical revision course Cardiac cycle


  1. Module outline - Anatomy - Myocytes - Cardiac cycle - Haemodynamics & blood pressure - Coronary circulation - Capillaries One 2 One Medicine: Pre-clinical revision course

  2. One 2 One Medicine: Pre-clinical revision course

  3. Cardiac cycle End diastolic volume Stroke volume End systolic volume One 2 One Medicine: Pre-clinical revision course

  4. 16 Frank-Starling law of the heart 100 Force of contraction - Preload/EDV 80 Increased determines SV Contractility sympathetic activity Stroke volume (ml) - Length tension 60 relationship = EDV 40 - Filament overlap 20 - Symp ↑ SV for any given EDV 0 0 20 40 60 80 100 120 140 160 180 200 End-distastolic volume (ml) One 2 One Medicine: Pre-clinical revision course

  5. Frank-Starling law of the heart 100 Factors affecting EDV: Force of contraction 80 - Venous tone Increased Contractility sympathetic activity Stroke volume (ml) - Blood volume 60 - Skeletal muscle pump 40 - Respiratory pump 20 - Posture 0 0 20 40 60 80 100 120 140 160 180 200 End-distastolic volume (ml) One 2 One Medicine: Pre-clinical revision course

  6. 17 Heart failure - = Cannot meet metabolic demand (at normal CVP) - Causes of heart failure: - Ischaemic heart disease - Hypertension - Valvular disease One 2 One Medicine: Pre-clinical revision course

  7. Heart failure 100 80 Stroke volume (ml) Heart 60 failure 40 20 0 0 20 40 60 80 100 120 140 160 180 200 End-distastolic volume (ml) One 2 One Medicine: Pre-clinical revision course

  8. Heart failure - Fluid retention → ↑ blood vol ∴ CVP - → RIGHT on Starling’s curve - Initially: ↑ SV - Late: dilated w/o ↑ SV - Remodelling (RAAS) One 2 One Medicine: Pre-clinical revision course

  9. Heart failure RAAS: ( ↓ renal perfusion) Sympathetic activation - Fluid & Na + retention - A ➙ Renin ( β 1) - ↑ Contractility - Ang-II ➙ Constriction - ↑ HR (inc. ↓ Vagus) - NA ➙ Vasoconstriction ∴ ↑ AFTERLOAD* ➙ ↑ ENERGY & ↓ *Afterload = total peripheral resistance One 2 One Medicine: Pre-clinical revision course

  10. Heart failure Right-sided heart failure Left-sided cardiac failure Raised jugular venous Pulmonary oedema pressure Hepatomegaly Peripheral hypoperfusion Peripheral oedema Orthopnoea Ascites Paroxysmal nocturnal dyspnoea Fatigue Cough & wheeze One 2 One Medicine: Pre-clinical revision course

  11. Key points - Pacemaker cells have a depolarising pre-potential due to high sodium permeability - End-diastolic volume (pre-load) determines force of contraction by controlling myocyte length - Sympathetics increase SAN rate, reduce AVN delay and increase ventricular contractility - Heart failure causes right- & down-wards shift on Frank-Starling curve One 2 One Medicine: Pre-clinical revision course

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