Cardiovascular System

Last updated: November 10, 2024
  • Outline the cardiovascular changes that occur at birth
    • Closure of the foramen ovale due to increased left atrial pressure
    • Reversal of blood flow in the ductus arteriosus, from the descending aorta to pulmonary trunk
    • Left ventricular hypertrophy and right ventricular atrophy
    • Pulmonary vascular resistance decreases
    • Pulmonary blood flow increases
    • The walls of pulmonary arteries progressively become thin
    • Constriction of the ductus arteriosus – bradykinin (potent vasoconstrictor)
    • Constriction of umbilical arteries
  • Describe the development, folding and septation of the primitive heart tube
    • Development
      • The heart tube is of mesodermal origin
        • Mesoderm forms the myocardium, mesothelium (pericardium) and endothelium (endocardium, blood vessels, lymphatics)
      • Cardiac progenitor cells are located cranial to the buccopharyngeal membrane of the epiblast
      • These progenitor cells ingress through the primitive streak and settle cranially at the splanchnic mesoderm
      • The cells organize into 2 solid cords known as the angioblastic cords. The ends of the angioblastic cords connect to sinusoidal capillaries (formed during vasculogenesis in the walls of the yolk sac. They later coalesce to form blood vessels connecting to the heart).
      • The angioblastic cords become canalized to form endocardial tubes.
      • Lateral embryonic folding at week 4 causes the 2 endocardial tubes to approach each other and fuse to form 1 primitive heart tube. The fusion happens in a craniocaudal direction.
      • Craniocaudal folding due to enlargment of the brain vesicles causes the heart to relocate to the pleuropericardial cavity
      • The medium septum of the primitive heart undergoes apoptosis, forming the definitive heart tube.
      • The walls of the definitive heart tube differentiate into 3 layers (epicardium ,myocardium, endocardium)
      • The tube develops 5 primary dilations: The Truncus Arteriosus, The Bulbus Cordis, The Primitive Ventricle, The Primitive Atrium, and the Sinus Venosus
      • The Aortic Sac is located outside the pericardium and it gives 6 branches corresponding to the pharyngeal arches (Pharyngeal arch arteries)
      • Blood entering the primitive heart comes from 3 sources: The body of the embryo (Anterior and posterior cardinal veins), Yolk sac (Vitelline veins), Placenta (Umbilical veins)
      • At this point, the heart is able to pump blood in a peristaltic flow (Ebb and Flow mechanism)
      • Inside the pleuropericardial cavity, the dorsal medocardium suspends the heart tube. It undergoes apoptosis, leaving the layer of the pericardium lining the heart to form the visceral pericardium. The fibrous pericardium is derived from the paraxial mesoderm of the cervical myotomes (septum transverum)
      • As the dorsal mesocardium undergoes apoptosis, a free space is left between the inflow and outlow tracts. This forms the transverse pericardial sinus.
      • The straight tube transforms into an S-shaped Heat loop
      • Endocardial cushions grow towards each other and fuse to separate
    • Folding (Cardiac Looping)
      • Cardiac looping establishes left-right polarity of the heart
      • Laterality sequences establish the polarity of the heart
      • The cranial portion (The Truncus arteriosus, Bulbus Cordis) loop ventrally, caudally, and to the right
      • The caudal portion (Pulmonary artery, Sinus Venosus) moves dorsally, cranially, and to the left
    • Septation
      • Atrial septation
        • Septum primum (SP) forms from the atrial endocardial cushion
        • Ostium primum forms between SP and Atrioventricular Endocardial Cushion (AVEC)
        • SP extends to AVEC obliterating ostium primum
        • Foramen secundum form as the superior part of SP undergoes apoptosis
        • Septum secundum forms from the Atrial endocardial cusion and approaches AVEC but does not obliterate the cavity
        • Foramen ovale is the oblique formen extending from the RA to LA via foramen secundum
        • During birth LA pressure is greater than RA pressure causing septum primum to fuse with septum secundum thus closing the foramen ovale
      • Ventricular septation
        • Muscular interventricular septum forms from the floor of the ventricles
        • The membranous interventricular septum froms from the right and left bulbur ridges
        • The muscular and membranous interventricular septum approach each other and fuse forming the IV septum
        • Septum primum (SP) forms from atrial endocardial cushion
        • Ostium primum btw SP and AVEC
        • SP extends to AV endocardial cushion (AVEC) obliterating ostium primum
        • Foramen secundum form as superior part of SP undergoes apoptosis
        • Septum secundum forms from Atrial endocardial cusion and approaches AVEC but does not obliterate the cavity
        • Foramen ovale is the oblique formaen extedning from the RA to LA via foramen secundum
        • During birth LA pressure is greater than RA pressure causing septum primum to fuse with septum secundum thus closing the foramen ovale
  • Describe the fate of the primitive veins that drain into the sinus venosus
    • Right sinus horn – Sinus venarum
    • Right anterior cardinal vein – SVC
    • Right vitelline vein – IVC
    • Right umbilical vein – Obliterated
    • Left sinus horn – Coronary sinus and oblique vein of LV
    • Left common cardinal vein, umbilical vein and vitelline vein – obliterated
  • Describe the septation of the primitive heart chambers
    • Atrial septation
      • Septum primum (SP) forms from the atrial endocardial cushion
      • Ostium primum forms between SP and Atrioventricular Endocardial Cushion (AVEC)
      • SP extends to AVEC obliterating ostium primum
      • Foramen secundum form as the superior part of SP undergoes apoptosis
      • Septum secundum forms from the Atrial endocardial cushion and approaches AVEC but does not obliterate the cavity
      • Foramen ovale is the oblique foramen extending from the RA to LA via foramen secundum
      • During birth LA pressure is greater than RA pressure causing septum primum to fuse with septum secundum thus closing the foramen ovale
    • Ventricular septation
      • Muscular interventricular septum forms from the floor of the ventricles
      • The membranous interventricular septum froms from the right and left bulbur ridges
      • The muscular and membranous interventricular septum approach each other and fuse forming the IV septum
  • What are the structural anomalies in tetralogy of fallot?
    • Right Ventricular Outflow Tract Obstruction (RVOTO) aka Infundibular stenosis
    • RV hypertrophy
    • Ventricular Septal Defect (VSD)
    • Aortic dextroposition (Overriding aorta)
    ***There exists a rare form known as the Pentalogy of Fallot. It has an ASD or Patent foramen Ovale in addition to the defects mentioned above
Reference Intervals ›
Biochemistry
ACTHP: <80 ng/L
ALTP: 5–35 U/L
AlbuminP: 35–50 g/L
AldosteroneP: 100–500 pmol/L
Alk. phosphataseP: 30–130 U/L
α-AmylaseP: 0–180 IU/dL
α-FetoproteinS: <10 kU/L
Angiotensin IIP: 5–35 pmol/L
ADHP: 0.9–4.6 pmol/L
ASTP: 5–35 U/L
BicarbonateP: 24–30 mmol/L
BilirubinP: 3–17 μmol/L
BNPP: <50 ng/L
CRPP: <10 mg/L
CalcitoninP: <0.1 mcg/L
Calcium (ionized)P: 1.0–1.25 mmol/L
Calcium (total)P: 2.12–2.60 mmol/L
ChlorideP: 95–105 mmol/L
CholesterolP: <5.0 mmol/L
VLDLP: 0.128–0.645 mmol/L
LDLP: <2.0 mmol/L
HDLP: 0.9–1.93 mmol/L
Cortisol AMP: 450–700 nmol/L
Cortisol MidnightP: 80–280 nmol/L
CK ♂P: 25–195 U/L
CK ♀P: 25–170 U/L
CreatinineP: 70–100 μmol/L
FerritinP: 12–200 mcg/L
FolateS: 2.1 mcg/L
FSHP: 2–8 U/L ♂; >25 menopause
GGT ♂P: 11–51 U/L
GGT ♀P: 7–33 U/L
Glucose (fasting)P: 3.5–5.5 mmol/L
Growth hormoneP: <20 mu/L
HbA1C (DCCT)B: 4–6%
HbA1C (IFCC)B: 20–42 mmol/mol
Iron ♂S: 14–31 μmol/L
Iron ♀S: 11–30 μmol/L
Lactate (venous)P: 0.6–2.4 mmol/L
Lactate (arterial)P: 0.6–1.8 mmol/L
LDHP: 70–250 U/L
LHP: 3–16 U/L
MagnesiumP: 0.75–1.05 mmol/L
OsmolalityP: 278–305 mosmol/kg
PTHP: 0.8–8.5 pmol/L
PotassiumP: 3.5–5.3 mmol/L
Prolactin ♂P: <450 U/L
Prolactin ♀P: <600 U/L
PSAP: 0–4 mcg/mL
Protein (total)P: 60–80 g/L
Red cell folateB: 0.36–1.44 μmol/L
Renin (erect)P: 2.8–4.5 pmol/mL/h
Renin (recumbent)P: 1.1–2.7 pmol/mL/h
SodiumP: 135–145 mmol/L
TBGP: 7–17 mg/L
TSHP: 0.5–4.2 mU/L
T4P: 70–140 nmol/L
Free T4P: 9–22 pmol/L
TIBCS: 54–75 μmol/L
TriglyceridesP: 0.50–2.3 mmol/L
T3P: 1.2–3.0 nmol/L
Troponin TP: <0.1 mcg/L
Urate ♂P: 210–480 μmol/L
Urate ♀P: 150–390 μmol/L
UreaP: 2.5–6.7 mmol/L
Vitamin B12S: 0.13–0.68 nmol/L
Vitamin DS: 50 nmol/L
Arterial Blood Gases
pH7.35–7.45
PaCO₂4.7–6.0 kPa
PaO₂>10.6 kPa
Base excess±2 mmol/L
Urine
Cortisol (free)<280 nmol/24h
Hydroxyindole acetic acid16–73 μmol/24h
Hydroxymethylmandelic acid16–48 μmol/24h
Metanephrines0.03–0.69 μmol/mmol cr.
Osmolality350–1000 mosmol/kg
17-Oxogenic steroids ♂28–30 μmol/24h
17-Oxogenic steroids ♀21–66 μmol/24h
17-Oxosteroids ♂17–76 μmol/24h
17-Oxosteroids ♀14–59 μmol/24h
Phosphate (inorganic)15–50 mmol/24h
Potassium14–120 mmol/24h
Protein<150 mg/24h
Protein/creatinine ratio<3 mg/mmol
Sodium100–250 mmol/24h
Haematology
WCC4.0–11.0 ×10⁹/L
RBC ♂4.5–6.5 ×10¹²/L
RBC ♀3.9–5.6 ×10¹²/L
Hb ♂130–180 g/L
Hb ♀115–160 g/L
PCV ♂0.4–0.54 L/L
PCV ♀0.37–0.47 L/L
MCV76–96 fL
MCH27–32 pg
MCHC300–360 g/L
RDW11.6–14.6%
Neutrophils2.0–7.5 ×10⁹/L (40–75%)
Lymphocytes1.0–4.5 ×10⁹/L (20–45%)
Eosinophils0.04–0.44 ×10⁹/L (1–6%)
Basophils0–0.10 ×10⁹/L (0–1%)
Monocytes0.2–0.8 ×10⁹/L (2–10%)
Platelets150–400 ×10⁹/L
Reticulocytes0.8–2.0% / 25–100 ×10⁹/L
Prothrombin time10–14 s
APTT35–45 s
Paediatric
Pulse Rate (bpm)
Neonate140–160
Infant <1yr120–140
1–5 years110–130
5–12 years80–120
>12 years70–100
Respiratory Rate (tachypnoea)
0–2 months≥60/min
2–12 months≥50/min
1–5 years≥40/min
>5 years≥30/min
Blood Pressure (mmHg)
Term65/45
1 year75/50
4 years85/60
8 years95/65
10 years100/70
Weight Formulas
3–12 months(a + 9)/2 kg
1–6 years2a + 8 kg
>6 years(7a − 5)/2 kg
Haemoglobin (g/dL)
Term newborn13–20
1 month11–18
2 months10–15
1–2 years10–13
>2 years11–14
MUAC (6 months–5 years)
Obese>17.5 cm
Normal13.5–17.4 cm
At risk12.5–13.4 cm
Moderate malnutrition11.5–12.4 cm
Severe malnutrition<11.5 cm
Developmental Milestones
Social smile1.5 months
Head control4 months
Sits unsupported7 months
Crawls10 months
Stands unsupported10–12 months
Walks12–13 months
Talks18 months
CSF WBC (/mm³)
Term newborn0–25
>2 weeks0–5
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