Differential Diagnosis of Chest Pain

Question 1

describe visceral afferent nerves

Answer 1

pain fibres travel to spinal cord alongside sympathetic nerves
visceral reflex afferents (e.g. from baroreceptors) travel mainly in vagus nerve (some in CN XI)
reach heart via cardiac plexus (sympathetic fibres, parasympathetic fibres and visceral afferent fibres)

Question 2

explain how sympathetic nerve fibres get from CNS to organs

Answer 2

CNS

presynaptic fibre/preganglionic fibre (connecting CNS and ganglion)
ganglion (synapse) - between axon of presynaptic neurone and cell body of postsynaptic neurones
ACh - neurotransmitter
postsynaptic fibre (connecting ganglion and organ)
noradrenlaine - neurotrasmitter

Question 3

explain how sympathetic signals from CNS reach organs

Answer 3

travel from brain inferiorly within spinal cord tracts and exit spinal cord in one of T1-L2/3 spinal nerves
they then either;
go into ganglion of that level and synapse
travel superiorly in sympathetic change to another ganglion and synapse
travel inferiorly in he sympathetic chain to another ganglion and synapse

Question 4

explain how postsynaptic sympathetic fibres reach organs

Answer 4

T1-T5 ganglia and cervical ganglia - cardiopulmonary splanchnic nerves (sympathetic nerves to heart and lungs) (postsynaptic fibres from cervical and upper thoracic sympathetic changes)
to a midline organ (e.g. heart) there will be bilateral sympathetic innervation (predominately left sided for heart)
L2/L3 spinal nerve level - abdominopelvic splanchnic nerves

Question 5

how do parasympathetic signals from CNS reach organs

Answer 5

CNS

presynaptic fibre (connecitng CNS and ganglion)

parasympathetic ganglion (synapse) between axon of presynaptic neurone and cell body of postsynaptic neurone 
ACh - neurotransmitter

postsynaptic fibre (connecting ganglion and organ) 
ACh - neurotransmitter

Question 6

explain how parasympathetic signals reach organs

Answer 6

via cranial nerves;
III (oculomotor nerve)
VII (facial nerve)
IX (glossopharyngeal nerve)
X (vagus nerve) - presynaptic parasympathetic fibres in vagus nerve then synapse onto postsynaptic neurones (with short axons in ganglia within walls of organs of the chest and upper abdomen e.g. heart, lungs)
to organs of the lower abdomen, pelvis and perineum (pelvic splanchnic nerves are parasympathetic)

Question 7

describe somatic pain

Answer 7

muscular
joint
bony
IV disc
fibrous pericardial 
nerve 

nature is sharp, stabbing, well localised
skin mechanoreceptors stimulated in right T5 dermatome
action potential propagated centrally
pain pathway crosses in spinal cord
sensation reaches consciousness at cerebral cortex

Question 8

describe visceral pain

Answer 8

heart and great vessels
trachea
oesophagus
abdominal viscerae

nature is dull, aching, nauseating, poorly localised

Question 9

describe radiating pain

Answer 9

pain felt in centre of chest and felt spreading from there;
upper limbs
back
neck

Question 10

describe referred pain

Answer 10

pain only felt at site remote from area of tissue damage in chest;
upper limbs
back
neck

Question 11

describe acute or chronic pain

Answer 11

repeated acute episodes versus chronic pain

Question 12

describe postcentral gyrus of partial lobe (somatosensory) -

Answer 12

action potentials arrive here bring body wall (somatic) sensations into consciousness

Question 13

describe precentral gyrus of frontal lobe (somatosensory)

Answer 13

action potentials originating here bring about contractions of body wall (somatic) skeletal muscle

Question 14

describe postcentral gyrus of right cerebral hemisphere

Answer 14

sensory action potentials arrive here when left side of chest wall is touched

Question 15

describe sensory homunculus

Answer 15

areas of cerebral neocortex (outermost layer of cerebral hemispheres) where sensations from different body wall structures (soma) reach consciousness
there is an equivalent somatic motor homunculus

Question 16

describe sharp (somatic) central chest pain sources

Answer 16

herpes zoster (shingles);
reactivation of dormant virus in posterior root ganglion
pain felt anywhere in that dermatome
pain precedes blisters
present if shingles developing in T4/5 dermatome

muscle, joint, bone;
pectoralis major or intercostal muscle strain
dislocated costochondral joint
costovertebral joint inflammation 
slipped thoracic IV disc

parietal pleura, fibrous pericardium;
pleurisy
pericarditi

Question 17

describe dull (visceral) central chain pain sources

Answer 17

aorta - ruptured aneurysm of aortic arch
trachea - tracheitis
oesophagus - oesophagitis
heart - angina and MI
abdonial viscerae - gastritis, cholecystitis, pancreatitis, hepatitis

Question 18

describe how pain signals from the organs reach the brain

Answer 18

visceral afferent action potentials pass bilaterally to thalamus and hypothalamus then diffuse areas of the cortex

cardiopulmonary splanchnic nerves (sympathetic nerves to chest organs) plus pain visceral afferents from chest organs

Question 19

describe sources of radiating pain

Answer 19

pain is felt both at the actual site of the pathology and also radiating
if pain is originating in a somatic structure the radiation is along the affected dermatome
if from the heart the radiation is to the dermatome supplied by the spinal cord levels at which the cardiac visceral afferents enter the sympathetic chain/spinal cord - bilaterally to cervical and upper thoracic dermatomes
visceral radiating pain is visceral in nature - although it is felt in a dermatomal pattern, it is still dull, aching and poorly localised in nature

Question 20

describe referred pain

Answer 20

sensation of pain is felt only at a site remote from the actual area of injury or disease, otherwise it is very similar to radiating pain
due to afferent fibres from soma and afferent fibres form viscera entering the spinal cord at same levels, the brain chooses to believe that the pain signals coming from the organ are actually coming form the soma

Question 21

describe a heart attack

Answer 21

irreversible death (necrosis) of part of myocardium due to occlusion of its arterial blood supply
type of MI is described clinically according to which surface of the heart has been affected;
anterior
inferior
anterolateral

Question 22

describe coronary atherosclerosis - common sites of narrowing/occlusion

Answer 22

1. anterior interventricular branch (LAD) of left coronary artery
2. right coronary artery
3. circumflex branch of left coronary artery
4. left (main stem) coronary artery

Question 23

describe coronary artery bypass grafting

Answer 23

commonly used grafts - radial artery/internal thoracic artery (by pedicle), great saphenous vein (leg)
grafts anastomosed to coronary artery distal to narrowing hence the narrowing is bypassed

Question 24

describe arrhythmia

Answer 24

if conducting tissue of the heart i damaged by ischemia, results in arrhythmia
most commonly damaged at;
AV nodal brnach from right coronary artery near origin of PIV artery
SA nodal branch from right coronary arteries near its origin

Question 25

describe blood supply to interventricular septum

Answer 25

left anterior descending or anterior interventricular artery
left and right bundle branches (conducting system)
posterior inteventricular artery