Cardiovascular System

InCheat Sheets / Embryology

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

Dr Jeffrey Kalei

Author and illustrator for Hyperexcision. Interested in emergency room medicine. I have a passion for medical education and drawing.

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Biochemistry

Adrenocorticotrophic hormone	P: <80 ng/L
Alanine aminotransferase (ALT)	P: 5–35 U/L
Albumin	P: 35–50 g/L
Aldosterone	P: 100–500 pmol/L
Alkaline phosphatase	P: 30–130 U/L (adults)
α-Amylase	P: 0–180 IU/dL
α-Fetoprotein	S: <10 kU/L
Angiotensin II	P: 5–35 pmol/L
Antidiuretic hormone (ADH)	P: 0.9–4.6 pmol/L
Aspartate transaminase	P: 5–35 U/L
Bicarbonate	P: 24–30 mmol/L
Bilirubin	P: 3–17 μmol/L
BNP	P: <50 ng/L
C-reactive protein	P: <10 mg/L
Calcitonin	P: <0.1 mcg/L
Calcium (ionized)	P: 1.0–1.25 mmol/L
Calcium (total)	P: 2.12–2.60 mmol/L
Chloride	P: 95–105 mmol/L
Cholesterol	P: <5.0 mmol/L
VLDL	P: 0.128–0.645 mmol/L
LDL	P: <2.0 mmol/L
HDL	P: 0.9–1.93 mmol/L
Cortisol	P: AM 450–700 nmol/L, Midnight 80–280 nmol/L
Creatine kinase (CK)	P: ♂ 25–195 U/L, ♀ 25–170 U/L
Creatinine	P: 70–100 μmol/L
Ferritin	P: 12–200 mcg/L
Folate	S: 2.1 mcg/L
FSH	P/S: 2–8 U/L ♂ (luteal); >25 U/L menopause
Gamma-glutamyl transpeptidase	P: ♂ 11–51 U/L, ♀ 7–33 U/L
Glucose (fasting)	P: 3.5–5.5 mmol/L
Growth hormone	P: <20 mu/L
HbA1C (DCCT)	B: 4–6%
HbA1C (IFCC)	B: 20–42 mmol/mol
Iron	S: ♂ 14–31 μmol/L, ♀ 11–30 μmol/L
Lactate	P: Venous 0.6–2.4 mmol/L, Arterial 0.6–1.8 mmol/L
Lactate dehydrogenase (LDH)	P: 70–250 U/L
Lead	B: <1.8 mmol/L
LH	P: 3–16 U/L (luteal)
Magnesium	P: 0.75–1.05 mmol/L
Osmolality	P: 278–305 mosmol/kg
Parathyroid hormone (PTH)	P: 0.8–8.5 pmol/L
Potassium	P: 3.5–5.3 mmol/L
Prolactin	P: ♂ <450 U/L, ♀ <600 U/L
PSA	P: 0–4 mcg/mL
Protein (total)	P: 60–80 g/L
Red cell folate	B: 0.36–1.44 μmol/L
Renin	P: Erect 2.8–4.5, Recumbent 1.1–2.7 pmol/mL/h
Sodium	P: 135–145 mmol/L
TBG	P: 7–17 mg/L
TSH	P: 0.5–4.2 mU/L
Thyroxine (T4)	P: 70–140 nmol/L
Free T4	P: 9–22 pmol/L
Total iron-binding capacity	S: 54–75 μmol/L
Triglycerides (fasting)	P: 0.50–2.3 mmol/L
Triiodothyronine (T3)	P: 1.2–3.0 nmol/L
Troponin T	P: <0.1 mcg/L
Urate	P: ♂ 210–480 μmol/L, ♀ 150–390 μmol/L
Urea	P: 2.5–6.7 mmol/L
Vitamin B12	S: 0.13–0.68 nmol/L
Vitamin D	S: 50 nmol/L

Arterial Blood Gases

pH	7.35–7.45
PaCO₂	4.7–6.0 kPa
PaO₂	>10.6 kPa
Base excess	±2 mmol/L

Urine

Cortisol (free)	<280 nmol/24h
Hydroxyindole acetic acid	16–73 μmol/24h
Hydroxymethylmandelic acid	16–48 μmol/24h
Metanephrines	0.03–0.69 μmol/mmol creatinine
Osmolality	350–1000 mosmol/kg
17-Oxogenic steroids	♂ 28–30 μmol/24h, ♀ 21–66 μmol/24h
17-Oxosteroids (neutral)	♂ 17–76 μmol/24h, ♀ 14–59 μmol/24h
Phosphate (inorganic)	15–50 mmol/24h
Potassium	14–120 mmol/24h
Protein	<150 mg/24h
Protein/creatinine ratio	<3 mg/mmol
Sodium	100–250 mmol/24h

Haematology

WCC	4.0–11.0 ×10⁹/L
Red cell count	♂ 4.5–6.5 ×10¹²/L, ♀ 3.9–5.6 ×10¹²/L
Haemoglobin	♂ 130–180 g/L, ♀ 115–160 g/L
PCV / Haematocrit	♂ 0.4–0.54 L/L, ♀ 0.37–0.47 L/L
MCV	76–96 fL
MCH	27–32 pg
MCHC	300–360 g/L
RDW	11.6–14.6%
Neutrophils	2.0–7.5 ×10⁹/L (40–75%)
Lymphocytes	1.0–4.5 ×10⁹/L (20–45%)
Eosinophils	0.04–0.44 ×10⁹/L (1–6%)
Basophils	0–0.10 ×10⁹/L (0–1%)
Monocytes	0.2–0.8 ×10⁹/L (2–10%)
Platelet count	150–400 ×10⁹/L
Reticulocyte count	0.8–2.0% / 25–100 ×10⁹/L
ESR	Depends on age
Prothrombin time	10–14 s
APTT	35–45 s

Paediatric

Pulse Rate (beats per minute)
Neonate (<1 month)	140–160
Infant (<1 year)	120–140
1–5 years	110–130
5–12 years	80–120
>12 years	70–100
Temperature
Normal range	36.6–37.2 °C
38.0 °C	Fever (infant)
38.5 °C	Fever (>3 months)
Respiratory Rate (tachypnoea)
Neonate (0–2 months)	≥60 breaths/min
2–12 months	≥50 breaths/min
1–5 years	≥40 breaths/min
>5 years	≥30 breaths/min
Blood Pressure (mmHg)
Term	65/45
1 year	75/50
4 years	85/60
8 years	95/65
10 years	100/70
Head Circumference
Term	35 cm ± 2
1 year	+1 cm/month
2–3 years	+2 cm/year
4–5 years	+1 cm/year
5 years	~53 cm
10 years	56–57 cm
Height
Term	52–55 cm
1 year	75 cm
2–12 years	6a + 77 cm
Weight Formulas
3–12 months	(a + 9)/2 kg
1–6 years	2a + 8 kg
>6 years	(7a − 5)/2 kg
Developmental Milestones
Social smile	1.5 months
Head control	4 months
Sits unsupported	7 months
Crawls	10 months
Stands unsupported	10–12 months
Walks	12–13 months
Talks	18 months
MUAC (6 months–5 years)
Obese	>17.5 cm
Normal	13.5–17.4 cm
At risk	12.5–13.4 cm
Moderate malnutrition	11.5–12.4 cm
Severe malnutrition	<11.5 cm
Blood Transfusion
Whole blood	20 mL/kg
pRBC	10 mL/kg
Formula	6 × (weight in kg) × Hb deficit
Normal Paediatric Lab Values
Haemoglobin (g/dL)	Hematocrit (%)
Term newborn: 13–20	40–58
1 month: 11–18	32–54
2 months: 10–15	28–44
1–2 years: 10–13	32–40
>2 years: 11–14	33–42
CSF WBC (/mm³)
Term newborn	0–25
>2 weeks	0–5

Dr Jeffrey Kalei

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