Cardiac System

Fetal Circulation

Heart Embryology

Mnemonic Embryonic structure Derivatives
Small Sinus venosus Smooth part of RA & Coronary sinus
Pump Primitive atrium Trabeculated part of RA & LA
Produces Primitive ventricle Trabeculated part of RV & LV
Big Bulbus cordis Smooth part of RV & LV
Turbulence Truncus arteriosus Aortic & Pulmonary trunk

Action Potential of Cardiac Muscle Cells

Phase SA & AV Nodes Atria & Ventricles
0 Ca current Na current
1 - K current
2 - Ca & K current
3 K current K current
4 Funny current: Na & K current Leak current: K current

Fick Principle

Parameter CO = VO2 ÷ (CaO2 - CvO2)
CO Cardiac output (dL/min)
VO2 O2 consumption rate (mL-O2/min)
CaO2 Arterial O2 content (mL-O2/dL)
CvO2 Venous O2 content (mL-O2/dL)

Factors Affecting Stroke Volume {CAP}

  • Contractility
  • Afterload
  • Preload

Cardiac & Vascular Function Curves

Label Examples
1 Catecholamines & Digitalis
2 Heart failure & Narcotics
3 Venopressors & Infusion
4 Venodilators & Hemorrhage & Spinal anesthesia
5 Vasopressors
6 Vasodilators & AV shunt

Effects of Adrenergic Receptors

Receptor CO SVR MAP
α1 ↑ (1°)
α2
β1 ↑ (1°) -
β2 ↓ (1°)

Effects of Special Maneuvers

Maneuver Effect
Valsalva ↓ Preload
Standing ↓ Preload
Squatting ↑ Preload
Leg rasie ↑ Preload
Hand grip ↑ Afterload

Heart Sounds

Heart Sound Mechanism
S1 MV & TV closure
S2 AV & PV closure

Approach to ECG

  • Rate
  • Rhythm
  • Axis
  • Interval
  • Morphology

Bazett's Formula of Corrected QT Interval (QTc)

Parameter QTc = QT ÷ √RR
QT QT interval
RR RR interval

ECG Localization of Coronary Blood Supply

Location Artery Leads
Septal LAD V1 & V2
Anterior LAD V3 & V4
Apical LAD / LCX / RCA V5 & V6
Lateral LCX I & aVL
Inferior RCA & LCX II & III & aVF
Posterior RCA / LCX V1 & V2 & V3

Views of Echocardiography

Cardiac Stress Test

Stress

  • Exercise :: treadmill & bicycle
  • Dobutamine
  • Vasodilators :: Dipyridamole & Adenosine

Imaging

  • Electrocardiography (ECG)
  • Echocardiography
  • Myocardial Perfusion Imaging (MPI)
    • Thallium-201
    • Technetium-99 sestamibi
    • Technetium-99m tetrofosmin