Cardiac

Question 1

Left coronary artery: origins

Answer 1

Left aortic sinus

Question 2

Right coronary artery: origins

Answer 2

right aortic sinus

Question 3

Left coronary artery branches

Answer 3

Left anterior descending (LAD)
Left marginal artery
Left circumflex artery

Question 4

Right coronary artery branches

Answer 4

Right marginal artery

Posterior interventricular artery

Question 5

Left anterior descending

Answer 5

Areas: Right ventricle
Left ventricle
Interventricular septum

ECG: V1-V4 (anterior MI)

Question 6

Left circumflex artery

Answer 6

Areas: Left atrium and ventricle
ECG: I, aVL, V5, V6 (anterolateral)

Question 7

Left marginal artery

Answer 7

Areas: left ventricle
ECG: lateral (I, aVL), posterior (V7-9, ST depression V1-3), inferior: 10% (II, aVF, III)

Question 8

Right coronary artery

Answer 8

Areas: right atrium, right ventricle
Sinoatrial node (60%), Atrioventricular node (90%)
ECG: Inferior (II, III, aVF), bradycardia (2nd/3rd degree heart block)

Question 9

Right marginal artery

Answer 9

Areas: right ventricle and apex

Question 10

Posterior inter ventricular artery

Answer 10

Areas: right and left ventricles, inter ventricular septum (posterior 1/3)

Question 11

Venous drainage of the heart

Answer 11

Drains into coronary sinus:
Great cardiac vein
Small cardiac vein
Middle cardiac vein
Posterior cardiac vein

Drains directly into right atrium:
Anterior cardiac veins

Question 12

Cardiac conduction system

Answer 12

Sinoatrial node
Atrioventricular node
Atrioventricular bundle (bundle of His)
Purkinje fibres

Question 13

Heart conduction

Answer 13

Creates excitation potentials
Wave of excitation spreads across atria causing atrial contraction
Reaches AV node, signal is delayed
Conducted into bundle of His down inter ventricular septum
Purkinje fibres spread wave impulses along ventricles causing them to contract

Question 14

Sinoatrial node

Answer 14

Specialised cells. Located in upper wall of right atrium. Can spontaneously generate impulses.
Sympathetic: increases firing of SA
Parasympathetic: decreases firing of SA

Question 15

Atrioventricular node

Answer 15

Delays impulses to ensure full atrial contraction

Question 16

Atrioventricular bundle (bundle of His)

Answer 16

Continuation of specialised tissue of AV node. Transmits electrical impulse from AV node to Purkinje fibres.
Descends down membranous part of septum before dividing into right bundle branch and left bundle branch

Question 17

Phases of cardiac action potential

Answer 17

Phase 0 - 4
Phase 0: Na in
Phase 1: K/Cl out
Phase 2: Ca in
Phase 3: K out
Phase 4: K rectifies

Question 18

Drugs and where they act in the cycle

Answer 18

Phase 0: Na in (Na channel blocker: lidocaine, phenytoin, flecanide)
Phase 1: K/Cl out
Phase 2: Ca in (Calcium channel blocker: Diltiazem, verapamil)
Phase 3: K out (K channel blocker: amiodarone)
Phase 4: K rectifies (beta blocker: propanolol)

Question 19

Foetal circulation adaptations

Answer 19

Umbilical arteries and vein
Ductus venosus (left portal vein to IVC)
Foramen ovale (right to left atrium)
Ductus arteriosus (pulmonary artery to aorta)

Question 20

Foetal circulation in utero

Answer 20

Gas exchange at placenta
O2 blood travels via umbilical vein to liver. Right umbilical vein provides liver with O2 blood. Left umbilical vein branches into ductus venosus, bypassing straight to IVC.
Mixed blood (O2 from LUV and deO2 from body) enters right atrium.
Pulmonary arterioles are hypoxic causing vasoconstriction increasing vascular resistance. Generates right to left shunt.
Blood preferentially shunts to left via ductus arteriosus and foramen ovale.
Internal iliac arteries given rise to umbilical artery, carrying deO2 blood to placenta.

Question 21

Foetal circulation after birth

Answer 21

After birth, air flows into lungs. Results in significant rise in O2 levels.
Pulmonary vascular resistance falls after reduction in hypoxic vasoconstriction
Changes in pressure gradients cause closure of foramen ovale and shift in blood flow across ductus arteriosus.
As O2 rises, smooth muscle wall of ductus arteriosus contracts, closing completely.
Umbilical vessels constrict forming round ligament of liver, ligamentum venous, superior vesical arteries.

Question 22

Ventricular septal defect (VSD)

Answer 22

Acyanotic.
Pansystolic murmur LLSE
L to R shunt, pulmonary HTN, RV hypertrophy, can develop shunt reversal.
Causes: foetal alcohol, Down’s (21), Edward’s (18), Patau’s (13)
Rx: surgical repair

Question 23

Persistent ductus arteriosus

Answer 23

Acyanotic.
Continuous ULSE “Gibson’s” murmur
Kept patent by Prostaglandin in utero.
Causes left to right shunt, SOB, HF, cyanotic lower extremities (Eisenmenger’s Syndrome)

Question 24

Patent foramen ovale/Atrial septal defect

Answer 24

Acyanotic.
Split S2 with ejection systolic murmur ULSE
Left to right atrial shunt.
Causes: Down’s (21), foetal alcohol syndrome
HF, SOB, recurrent chest infections, paradoxical embolus.
Rx: surgery w. patch/plug

Question 25

Tetralogy of Fallot

Answer 25

Cyanotic. (Tet spells)
1. Narrowing of RV outflow tract (PV stenosis)
2. RV hypertrophy
3. Ventricular septal defect
4. Aorta overrides septal defect
Causes: Chromosome 22 deletion, DiGeorge syndrome
Rx: VSD repair, pulmonary stenosis widening

Question 26

Transposition of great vessels

Answer 26

Cyanotic.
Aorta attached to RV, pulmonary artery attached to LV. 2 parallel circuits created.
Causes: maternal DM.
Rx: maintain ductus arteriosus with prostaglandins. Surgery.

Question 27

Coarctation of aorta

Answer 27

Acyanotic
Ejection systolic murmur left infraclavicular area. Weak or absent femoral pulses
Rx: conservative or resection if severe.