Cardiac Physiology & Pathologies

Cardiac anatomy

Blood Flow through the Heart

  • heart is a double pump, R side pumps blood into pulmonary circuit, L side pumps blood into the systemic circuit

Right side                           Left Side

Vena Cava                          Pulmonary veins

Atrium                                 Atrium

Tricuspid valve                   Mitral valve

Ventricle                             Ventricle

Pulmonary valve                Aortic valve

Pulmonary artery               Aorta

Cardiac Cycle

  • diastole: chamber at rest & filling with blood

    • both atria and ventricles can be in diastole at the same time

  • systole: chamber contracting & ejecting blood

    • atria and ventricle CANNOT be in systole at the same time

Term Association/ Cycle

  • mechanical event

    • contraction generated by calcium influx in cell (DEpolarization)

  • Cardiac cycle event

    • systole

  • Electrical event

    • depolarization: change in cell membrane electrical charge (- → +) that allows calcium influx

      • if contraction is in atria it is the P wave

      • if contraction is in ventricles its QRS complex

  • Mechanical event

    • relaxation as calcium is reduced

  • Cardiac cycle event

    • diastole

  • Electrical event

    • repolarization ( + → -) that allows calcium influx

EKG

  • EKG meaasures electric activity in heart

  • P wave is electric change in atria initiating contraction (SA node to AV node

  • T wave represents electric change in ventricles initiating relaxation

  • QRS represents atrial repolarization and ventricular depolarization (atria relax, ventricles contract)

Atrial & Ventricular Systole

  • SA node in the R. atrium wraps around the atria and triggers contraction on the way to the AV node

  • AV node in R. atrium wraps around ventricles & triggers their contraction

Cardiac Pathologies

Cardiac Hypertrophy

  • concentric hypertrophy: results from pressure overload, MAP is too high

  • eccentric hypertrophy: too much blood volume getting into ventricle and stretching out tissue

  • both can be adaptations to exercise, thats when they are good

  • BOTH can result in heart failure when pathologic, w/ either preserved ejection fraction (HFpEF) or reduced ejection fraction (HFrEF)

Mechanical Event Pathology

  • there’s a disturbance in the chain

    • electric normal,

    • mechanic eccentric hypertrophy from volume overload

    • causes stretching and weakening of ventricles,

    • insufficient ventricular pressure

    • blood flow: reduced ejection fraction (HFrEF)

      • normal ejection fraction = 70% of LVEDV (left ventricular end diastolic volume (most blood L. ventricle will ever have))

      • heart failure = <40% of LVEDV

Pressure Event Pathology

  • electric normal

  • mechanical normal

  • pressure: elevated ventricular pressure to overcome arterial pressure (Pventricle>Partery)

    • chronic hypertension

    • valvular stress

    • diabetes, obesity

  • blood flow is initially maintained (concentric hypertrophy)

    • over time HFpEF occurs

    • progression to true heart failure

Blood Flow Event Pathology

  • electric normal

  • mechanical normal

  • pressure normal

  • blood flow: moves backwards instead of forward due to a valvular disease (regurgitation)

    • blood flows back into atrium, but theres still blood coming from pulmonary veins that all needs to be pushed back into the ventricle, causing stretching

  • can lead to overload of the ventricle HFrEF