032
Pages 776-800
Upper limb anatomy
The information below contains selected facts which commonly appear in examinations:
Nerve
Motor
Sensory
Musculocutaneous
nerve (C5-C7)
Elbow flexion (supplies
biceps brachii) and
supination
Axillary nerve
(C5, C6)
Shoulder abduction
(deltoid muscle)
Radial nerve (C5C8)
Extension (forearm,
wrist, fingers, thumb)
Median nerve (C6,
C8, T1)
LOAF* muscles
Features depend on the
site of the lesion:
•
wrist: paralysis of
thenar muscles,
opponens pollicis
•
elbow: loss of
pronation of
forearm and
weak wrist
flexion
Ulnar nerve (C8,
T1)
Intrinsic hand muscles
except LOAF*
Wrist flexion
Long thoracic
nerve (C5-C7)
Serratus anterior
Often during sport e.g.
following a blow to the ribs.
Also possible complication
of mastectomy
Damage results in a
winged scapula
*LOAF muscles
•
Lateral two lumbricals
•
Opponens pollis
•
Abductor pollis brevis
•
Flexor pollis brevis
Notes & Notes for MRCP
By Dr. Yousif Abdallah Hamad
Typical mechanism of injury & notes Lateral part of the forearm Isolated injury rare - usually injured as part of brachial plexus injury Inferior region of the deltoid muscle Humeral neck fracture/dislocation Results in flattened deltoid Small area between the dorsal aspect of the 1st and 2nd metacarpals Humeral midshaft fracture Palsy results in wrist drop Palmar aspect of lateral 3 and half fingers Wrist lesion → carpal tunnel syndrome Medial 1and half fingers Medial epicondyle fracture Damage may result in a 'claw hand'
Notes & Notes for MRCP
By Dr. Yousif Abdallah Hamad
Chapter 4
Neurology
Radial nerve Overview • arises from the posterior cord of the brachial plexus (C5-8) • It is susceptible to compression or traumatic damage as it winds around the humerus (including ‘Saturday night palsy’, a pressure palsy sustained while sleeping in an awkward position under the influence of alcohol), • may also be compressed in the axilla (eg from using a crutch). Regions innervated Motor (main nerve) • Triceps • Anconeus • Brachioradialis • Extensor carpi radialis Motor (posterior interosseous branch) • Supinator • Extensor carpi ulnaris • Extensor digitorum • Extensor indicis • Extensor digiti minimi • Extensor pollicis longus and brevis • Abductor pollicis longus Sensory • Dorsal aspect of lateral 3 1/2 fingers • The commonest site of sensory loss is at the anatomical snuffbox (small area between the dorsal aspect of the 1st and 2nd metacarpals) Patterns of damage • wrist drop with hand pronation and thumb adduction • sensory loss to small area between the dorsal aspect of the 1st and 2nd metacarpals Axillary damage • as above • paralysis of triceps Features according to site of damage
Site of lesion
Sensory symptoms
Motor symptoms
Axilla
•
All below
•
All below
•
Paralysis of triceps
m
Mid-arm
•
All below
•
Numbness, paresthesia, pain along
lateral posterior arm
extensors
(hand, finger
and wrist joint).
Elbow (radial tunnel)
•
Pain and tenderness following
extension or repetitive
pronation/supination
•
Sometimes
weakness of
extension and
supination,
secondary
to pain (not to
missing
innervation)
Deep Forearm (posterior
interosseous nerve)
•
None
•
Paralysis of the
finger extensors
(no true wrist
drop)
Superficial forearm and
wrist (superficial radial
nerve)
•
Deficits on the radial side of the dorsum
of the hand (thumb, index finger, and
the radial half of the middle finger)
Common questions about radial nerve:
Question
Answer
Rout?
C5-8
Typical injury
•
Fractured midshaft of humerus/compression of axilla by chaircrutches. ‘Saturday night palsy’,
Motor loss?
extensor muscles (forearm, wrist, fingers, thumb)
Sensory loss?
•
dorsal aspect of lateral 3 1/2 fingers
•
anatomical snuffbox
The commonest site of
sensory loss
anatomical snuffbox (small area between the dorsal aspect of the
1st and 2nd metacarpals)
Sign?
wrist drop
Notes & Notes for MRCP
By Dr. Yousif Abdallah Hamad
• All below • Wrist drop weakness of • None
Notes & Notes for MRCP
By Dr. Yousif Abdallah Hamad
Chapter 4
Neurology
Median nerve Overview • arises from lateral and medial cords of the brachial plexus (C6-8, T1) • Motor to (LOAF) When look at hand in this position, can see this makes an "L" shape, since L Lumbrical. Lateral two lumbricals Opponens pollicis →rotates and flexes the thumb Abductor pollicis brevis →Abduction and opposition of the thumb Flexor pollicis brevis →Flexes the thumb at the first metacarpophalangeal joint • the above three form the thenar eminence muscles • also supplies flexor muscles of the forearm • Sensory to → palmar aspect of lateral (radial) 3 1/2 fingers Patterns of damage • Damage at wrist e.g. carpal tunnel syndrome paralysis and wasting of thenar eminence muscles sensory loss to palmar aspect of lateral (radial) 3 1/2 fingers • Damage at elbow, as above plus: unable to pronate forearm weak wrist flexion ulnar deviation of wrist • Anterior interosseous nerve (branch of median nerve) leaves just below the elbow results in loss of pronation of forearm and weakness of long flexors of thumb and index finger Common questions about median nerve: Question Answer Rout C6-8, T1 Typical injury? Fracture of supracondylar humerus/ Carpal tunnel syndrome Motor deficit? Opposition of thumb/Lateral finger flexion (ulnar deviation of wrist)/wrist flexion /(LOAF) muscles Sensory deficit Dorsal-palmar lateral 3.5 fingers/thenar eminence Sign? Ape hand (loss of Opponens pollicis)/Pope's hand (open digits 1-3 when trying to make fist)
Notes & Notes for MRCP
By Dr. Yousif Abdallah Hamad
Carpal tunnel syndrome Overview • Carpal tunnel syndrome is caused by compression of median nerve in the carpal tunnel. • More common in females (F:M, up to 8:1). • Commonly bilateral with dominant hand typically affected first. Causes • idiopathic • pregnancy • oedema e.g. heart failure • lunate fracture • rheumatoid arthritis History • pain/pins and needles in thumb, index, middle finger • unusually the symptoms may 'ascend' proximally • patient shakes his hand to obtain relief, classically at night Examination • weakness of thumb abduction (abductor pollicis brevis) • wasting of thenar eminence (NOT hypothenar →supplied by ulnar nerve ) • Tinel's sign: tapping causes paraesthesia • Phalen's sign: flexion of wrist for 60 seconds causes symptoms • Which area supplied by the median nerve will be spared if the problem is at the carpal tunnel? the skin over the thenar eminence The palmar cutaneous branch of the median nerve lies superficial to the flexor retinaculum and does not pass through the carpal tunnel. It supplies the skin over the thenar eminence, which is therefore spared in carpal tunnel syndrome. Electrophysiology • The most appropriate further investigation Electromyogram (EMG)/nerve conduction studies (EMG)/nerve conduction study is useful for confirming clinical diagnosis prior to actual surgery. nerve conduction studies show: decreased conduction velocity in the median nerve. prolongation of the action potential Treatment • In patients with mild carpal tunnel syndrome the management should be behavior modification. • corticosteroid injection • wrist splints at night • surgical decompression (flexor retinaculum division)
Notes & Notes for MRCP
By Dr. Yousif Abdallah Hamad
Chapter 4
Neurology
Pronator teres syndrome Definition • entrapment of the median nerve between the two heads of the pronator teres muscle at the elbow Features • The characteristic physical finding is tenderness over the proximal median nerve, which is aggravated by resisted pronation of the forearm. Diagnosis • Examination involves excluding carpal tunnel syndrome and pronation of the affected forearm against resistance, which brings on the pain. Unlike carpal tunnel syndrome, the median nerve proximal to the wrist may be tender to palpation. Treatment • Injection of corticosteroids into the pronator teres muscle may produce relief of symptoms, but a strong response to a steroid injection would be more consistent with carpal tunnel syndrome
Anterior interosseous syndrome Definition • Anterior interosseous syndrome or Kiloh-Nevin syndrome is a damage to the anterior interosseous nerve, a motor branch of the median nerve, which arises just below the elbow. • innervates the long flexor muscles of the thumb (Flexor pollicis longus), index and middle finger (flexor digitorum profundus). Causes • neuritis (inflammation of the nerve) in most cases, compression or Trauma Feature • Pain in the forearm • Characteristic weakness of the pincer movement of the thumb and index finger. • If asked to make the "OK" sign, patients will make a triangle sign instead. This 'Pinch-Test' exposes the weakness of the Flexor pollicis longus muscle and the flexor digitorum profundus leading to weakness of the flexion of the distal phalanges of the thumb and index finger. • Difficulty picking up a small item, such as a coin, from a flat surface Diagnosis • Electromyography (EMG) is generally most useful and will reveal abnormalities in the flexor pollicis longus, flexor digitorum profundus I and II and pronator quadratus muscles.
Notes & Notes for MRCP
By Dr. Yousif Abdallah Hamad
Ulnar nerve Overview • Root arises from medial cord of brachial plexus (C8, T1) • Motor innervation Third and fourth lumbricals (medial two lumbricals) Flex at metacarpal phalangeal (MCP) joint Extend at proximal interphalangeal (PIP) joint Adductor pollicis: adducts the thumb Abductor digiti minimi: abducts the little finger Flexor carpi ulnaris: helps flex the wrist Dorsal and palmar interossei: finger abduction and adduction respectively Flexor digiti minimi brevis: flexes the MCP joint • Sensory innervation medial 1 1/2 fingers (palmar and dorsal aspects) Causes • The ulnar nerve is most commonly compressed at or near the cubital tunnel of the elbow and Guyon canal of the wrist. Cubital tunnel syndrome (ulnar nerve compression at the elbow) Leaning on the elbow or prolonged elbow flexion during occupational activities (e.g., leaning on a desk), athletic activities, or surgical procedures (e.g., during general anesthesia) Blunt trauma Masses (e.g., tumors, hematomas) Metabolic abnormalities (e.g., diabetes) Guyon canal syndrome (ulnar nerve compression at the wrist in Guyon's canal) Often associated with cycling, likely caused by direct pressure from the handlebars
Notes & Notes for MRCP
By Dr. Yousif Abdallah Hamad
Chapter 4
Neurology
Blunt trauma (e.g., hook of hamate fracture) Masses (especially ganglion cysts) • The most common ulnar neuropathies are cubital tunnel syndrome the commonest site for entrapment of ulnar nerve caused by ulnar nerve compression at the elbow may be due to chronic pressure, leaning on the elbows, and direct trauma. ulnar tunnel syndrome caused by ulnar nerve compression at the wrist in Guyon's canal Risk factors • Ulnar neuropathy is a common complication with ill patients in hospital. Features • Wasting and paralysis of intrinsic hand muscles (except lateral two lumbricals) • Claw hand (where the little and ring fingers curl into the palm). hyperextension of the metacarpophalangeal joints and flexion at the distal and proximal interphalangeal joints of the 4th and 5th digits • Weak pinch (Froment sign) little finger in persistent abduction due to weak third palmar interosseous muscle • Radial deviation of wrist • Wartenberg sign: little finger in persistent abduction due to weak third palmar interosseous muscle • Froment sign: The thumb flexes at the interphalangeal joint while pinching a piece of paper to compensate for a weak adductor pollicis muscle. • Sensory loss to the medial 1 1/2 fingers (palmar and dorsal aspects) Proximal and distal lesions of the ulnar nerve lead to claw hand deformity. Diagnosis • Nerve conduction studies will confirm the site of the lesion. Common questions about ulnar nerve Question Answer Rout ? C8-T1 Typical injury? Fracture of epicondyle of humerus Motor deficit? Medial finger flexion/wrist flexion Sensory deficit? Medial 1.5 fingers/hypothenar eminence Sign? Radial deviation of wrist upon flexion/claw hand MRCPUK-part-1-sep 2017: H/O dropping things on a frequent basis and muscle wasting at the back of the right hand. On examination, you note wasting of the dorsal interossei. What is the nerve supply of the dorsal interossei? C8/T1
Notes & Notes for MRCP
By Dr. Yousif Abdallah Hamad
& Notes for MRCP By Dr. Yousif Abdallah Hamad
Rotator cuff muscles Muscle Notes Supraspinatus aBDucts arm before deltoid Most commonly injured Infraspinatus Rotates arm laterally teres minor aDDucts & rotates arm laterally Subscapularis aDDuct & rotates arm medially
Klumpke’s palsy Definition • Injury to the lower trunk of the brachial plexus (C8–T1) • This root eventually supplies the median and ulnar nerves. • The ulnar nerve supplies all of the intrinsic hand muscles except for those of the thenar eminence and the first and second lumbricals which are innervated by the median nerve. Causes • Hyperabduction of the arm Trauma (e.g., breaking a fall by grabbing a branch) Birth injury: excessive upward traction on the arm during delivery • Compression of the lower trunk of brachial plexus (subacute to chronic onset) Pancoast tumor Cervical rib Features • Weakness of intrinsic hand muscles (thenar, hypothenar, lumbricals, interossei) → total claw hand (persistent flexion of the interphalangeal joints and extension of the metacarpophalangeal joints in the hand) • Preganglionic Horner syndrome if injury occurs proximal to the white ramus communicans • Decreased peripheral pulses if subclavian vessels are compressed by a Pancoast tumor or cervical rib. • Sensory loss in the C8 and T1 dermatomes (little finger and medial surface of the forearm and arm) Treatment • Splinting the hand to correct the claw hand • Physiotherapy • Surgery for severe nerve damage Stretch injury of the arm • Sudden upward movement of the abducted arm (fall that has been stopped by grasping a fixed object with one hand) → causes features of an ulnar nerve palsy which is supplied by the lower brachial plexus roots C8 and T1 (Klumpke's paralysis)
Chapter 4
Neurology
Commonly tested nerves of the lower limbs
The information below contains selected facts which commonly appear in
examinations:
Nerve
Motor
Sensory
Typical mechanism of injury & notes
Femoral
nerve
Knee
extension,
thigh flexion
Anterior and
medial aspect of
the thigh and lower
leg
Obturator
nerve
Thigh
adduction
Medial thigh
Anterior hip dislocation
Lateral
cutaneous
nerve of the
thigh
None
Lateral and
posterior surfaces
of the thigh
Tibial nerve
Foot
plantarflexion
and inversion
Sole of foot
•
Not commonly injured as deep and well
protected.
•
Popliteal lacerations, posterior knee
dislocation
Common
peroneal
nerve
Foot
dorsiflexion
and eversion
Extensor
hallucis longus
Dorsum of the foot
and the lower
lateral part of the
leg
Superior
gluteal
nerve
Hip abduction
None
•
Misplaced intramuscular injection
•
Hip surgery
•
Pelvic fracture
•
Posterior hip dislocation
•
Injury results in a positive
Trendelenburg sign
Inferior
gluteal
nerve
Hip extension
and lateral
rotation
None
•
Generally injured in association with the
sciatic nerve
•
Injury results in difficulty rising from seated
position. Can't jump, can't climb stairs
Notes & Notes for MRCP
By Dr. Yousif Abdallah Hamad
• Hip and pelvic fractures • Stab/gunshot wounds Compression of the nerve near the ASIS → meralgia paraesthetica, a condition characterised by pain, tingling and numbness in the distribution of the lateral cutaneous nerve • Injury often occurs at the neck of the fibula Tightly applied lower limb plaster cast • Injury causes foot drop
Notes & Notes for MRCP
By Dr. Yousif Abdallah Hamad
Sciatic nerve palsy Nerve root • L4–S3 • Sciatic nerve splits into tibial nerve and common peroneal nerve Causes • Total hip arthroplasty known complication of a total hip replacement (femoral nerve palsy can occur but is much less common). • Herniated lumbar disc • Posterior hip dislocation • Iatrogenic (misplaced intragluteal injection) Feature • Motor Impaired knee flexion and hip adduction Global weakness of the ankle due to the involvement of both of its branches: tibial nerve (plantaflexion and inversion) and common peroneal nerve (dorsiflexion and eversion). Absent ankle jerk is due to tibial nerve involvement. • Sensory Sensory loss is variable but most commonly occurs around the dorsum of the foot and lateral aspect of the leg Tibial nerve injury → Sensory loss over sole of the foot The skin over the medial malleolus and medial border of the foot is innervated by the saphenous nerve and is therefore spared.
Chapter 4
Neurology
Injuries of sciatic nerve branches Common peroneal nerve injury Tibial nerve injury Nerve root L4–S2 L4–S3 Common causes • Fracture of the fibular head • Compression: tight casts, sitting cross-legged, lithotomy position during surgery Motor deficit • Superficial peroneal nerve: paralysis of peroneus longus and peroneus brevis → impaired eversion of the foot • Deep peroneal nerve: paralysis of foot and toe extensors (dorsiflexors) (e.g., tibialis anterior), leading to: • Foot drop • Steppage gait Sensory deficit • Superficial peroneal nerve: lateral surface of the lower leg, dorsum of the feet and toes, except for the space between the first and second toe • Deep peroneal nerve: area between the first and second toes (flip-flop zone)
Common peroneal nerve lesion
The commonest cause of acute foot drop after prolonged bed rest is entrapment common
peroneal neuropathy at the neck of fibula.
Overview
•
The sciatic nerve divides into the tibial and common peroneal nerves in the popliteal fossa.
•
Nerve root → L4–S2
•
Common peroneal nerve divides into a superficial and a deep branch
Deep peroneal nerve supplies muscles, which dorsiflex the foot and toes:
tibialis anterior
extensor hallucis longus
extensor digitorum longus
Superficial nerve supplies the muscles, which evert the foot
peroneus longus and brevis
Notes & Notes for MRCP
By Dr. Yousif Abdallah Hamad
• Trauma of the knee or leg (e.g., tibial fracture) • Baker cyst (causes proximal lesion) • Tarsal tunnel syndrome (causes distal lesion) • Paralysis of biceps femoris (long head) • Paralysis of foot flexors (e.g., triceps surae) → inability to stand on or curl toes and to invert foot • Proximal lesions: eversion of the foot at rest • Sensory loss over sole of the foot
Notes & Notes for MRCP
By Dr. Yousif Abdallah Hamad
• Injury often occurs at the neck of the fibula. Causes • Fracture of the fibular head • Compression: tight casts, sitting cross-legged, lithotomy position during surgery Features • Foot drop (the most characteristic feature) Superficial peroneal nerve: paralysis of peroneus longus and peroneus brevis → impaired eversion of the foot Deep peroneal nerve: paralysis of foot and toe extensors (dorsiflexors) (e.g., tibialis anterior), leading to: Foot drop and Steppage gait • Sensory loss over the dorsum of the foot and the lower lateral part of the leg with sparing of the fifth toe. Superficial peroneal nerve: lateral surface of the lower leg, dorsum of the feet and toes, except for the space between the first and second toe Deep peroneal nerve: area between the first and second toes (flip-flop zone)
Femoral nerve palsy Nerve root • L2–L4 Causes • Compression: Prolonged pressure on the nerve: Psoas haematoma (due to anticoagulant therapy or haemophilia), Psoas abscess Tumours - eg: Synovial cyst, Sarcoma Aortic or iliac aneurysms • Trauma: Direct injury to the nerve Hip or pelvic fractures Iatrogenic: eg: Hip arthroplasty, pelvic surgery, femoral line placement, coronary angiography). • Diabetic amyotrophy (proximal neuropathy, in diabetic patients, causes burning pain in the hip and thigh and wasting of thigh muscles) • Foot-drop • Weakness of eversion + dorsiflexion + inversion →L4 - 5 radiculopathy • Weakness of eversion + dorsiflexion →common peroneal nerve palsy (ankle inversion is spared with common peroneal nerve palsy) Differences between tibial nerve and peroneal nerve injuries: • Tibial → impaired foot Inversion and Plantarflexion • Peroneal → impaired foot Eversion and Dorsiflexion
Notes & Notes for MRCP
By Dr. Yousif Abdallah Hamad
Chapter 4
Neurology Feature • Motor Paralysis of iliopsoas, pectineus, rectus femoris, and sartorius muscles → impaired hip flexion Paralysis of quadriceps femoris muscle → Impaired knee extension: instability of the knee (often described as 'buckling') on climbing stairs. Decreased patellar tendon reflex (absent knee jerk) • Sensory Decreased sensation in anterior thigh (meralgia paraesthetica) and medial distal leg (saphenous nerve) Obturator nerve injury • Root: L2–L4 • Common causes: Pelvic surgery, pelvic ring fractures • Motor deficits: Paralysis of hip adductors (adductor longus, adductor brevis, adductor magnus, obturator externus, gracilis, pectineus) • Sensory deficits: Howship-Romberg sign: pain and paresthesia over the inner aspect of the thigh.
Meralgia paraesthetica Nerve root • L2–L4 Pathology • compression of lateral cutaneous nerve of thigh Causes of compression • Most likely causes→ entrapment at the lateral inguinal ligament: Increased intra-abdominal pressure (e.g., pregnancy, obesity, ascites) External compression (e.g., tight belts, pants, or compression dressings) Local compression (e.g., tumors, hematomas) • Less likely causes →trauma, ischaemia, or a retroperitoneal lesion. Burning thigh pain - ? meralgia paraesthetica - lateral cutaneous nerve of thigh compression Hip weakness: • Weakness of hip Abduction (Gluteus medius) → superior gluteal nerve palsy • Weakness of hip adduction (Adductor magnus and minimus) Obturator nerve palsy • Weakness of hip flexion (iliopsoas muscle) →Femoral nerve palsy • Weakness of hip extension (Gluteus maximus) →inferior gluteal nerve
Notes & Notes for MRCP
By Dr. Yousif Abdallah Hamad
Features
•
typically burning sensation over antero-lateral aspect of thigh
•
pure sensory loss
•
numbness when tapping on the inguinal ligament
Treatment
•
Can be improved by wearing looser clothing and/or losing weight
Healthy patient came with burning thigh pain. What is the next step in management?
Advice the patient to wear loose pant
MRCPUK-part-1- May 2006 exam: A patient presents with a burning sensation over anterolateral aspect of thigh. Which nerve is most likely to be affected?
Lateral cutaneous nerve of thigh
Saphenous nerve injury
Overview
• Saphenous nerve is a terminal cutaneous branch of the femoral nerve.
•
It is supplies the skin over the anteromedial side of the knee, leg and medial
malleolus.
•
It is strictly a sensory nerve; it has no motor component.
•
It is commonly blocked to complement anesthesia of the lower leg.
Causes
•
Saphenous vein harvest for coronary artery bypass grafting (CABG) (most common).
•
Femoral artery catheterization for angiography.
•
Trochanter placement during knee arthroscopy.
•
Long saphenous vein stripping for varicose veins.
Features
•
Loss of sensation over the medial aspect of the lower leg.
Tarsal tunnel syndrome Overview • also, known as posterior tibial neuralgia • It is analogous to carpal tunnel syndrome of the wrist. Definition • peripheral neuropathy caused by compression of the tibial nerve by the flexor retinaculum of the foot at the medial ankle Tarsal tunnel syndrome entrapment of the posterior tibial nerve as it travels through the tarsal tunnel, this tunnel is found along the inner leg behind the medial malleolus →painful foot
Notes & Notes for MRCP
By Dr. Yousif Abdallah Hamad
Chapter 4
Neurology
Causes
•
Trauma (most common): fracture or sprain of the ankle (talus, calcaneus, medial malleolus)
•
Rheumatoid arthritis
Features
•
Symptoms develop in areas innervated by the tibial nerve (distal to the medial malleolus):
Neuropathic pain and paresthesia in the heel, sole of the foot, and first three toes
Weakness and atrophy of intrinsic foot muscles (severe cases)
•
Symptoms worsen with walking, prolonged standing, and at night
Diagnosis
•
•
Usually a clinical diagnosis
•
Positive Tinel sign: radiating paresthesia triggered by tapping the flexor retinaculum
posterior to the medial malleolus
•
Pain upon foot dorsiflexion with eversion
•
Diminished sensation on the plantar area of the foot
•
Nerve conduction studies: slow conduction velocity in the medial and lateral plantar nerves
Treatment
•
Initially conservative (Rest, NSAIDs, physiotherapy, use of orthotic shoes)
• Local injection of steroids into the tarsal canal (if no improvement)
•
Surgical decompression
Third edition Notes & Notes For MRCP part 1 & 11 By Dr. Yousif Abdallah Hamad Cardiology Updated
Notes & Notes for MRCP
By Dr. Yousif Abdallah Hamad
Chapter 5
Cardiology Coronary arteries: anatomy and clinical correlation • Right coronary artery (RCA) supplies: AV node, so heart block following inferior MI is common. However, heart block following anterior MI is a grave prognostic marker as this indicates a large anterior wall infarct. RCA supplies SA node in 60%, AV node in 90% Right ventricle, hence, problems relating to a right ventricular infarct are commonly associated with an inferior MI. Inferior myocardium and occlusion causes ST elevation in II, III and aVF. Posterior descending artery a branch of the right coronary artery in 85% of people (a branch of the circumflex in the remaining population). supplies the posterior left ventricular myocardium occlusion causes posterior MI (ST depression in V1-V4 with a dominant R wave in V1). The concept of coronary dominance refers to which coronary artery supplies the posterior descending coronary artery (PDA). 85% of patients having a dominant right coronary artery 15% of patients having a dominant left circumflex. • Left main stem left coronary artery (LCA) Supplies most of the left ventricle. Complete left main stem occlusion is invariably fatal. It would produce extensive ST elevation across all the chest leads, I and aVL and possibly aVR, too. LCA branches into → Left Anterior Descending (LAD) + Left Circumflex artery (LCX) Left Anterior Descending (LAD) artery supplies : anterior and septum Occlusion →ST segment elevation in leads V1-V4 Right bundle branch block in acute anterior myocardial infarction suggests obstruction prior to the first septal branch of the left anterior descending coronary artery Left Circumflex artery (LCX) Supplies : lateral Occlusion produces ST elevation in V5, V6, I and aVL. • ECG localization of STEMI ECG leads with ST elevation Infarction location V1 – V2 Anteroseptal (LAD) V3- V4 Antero-apical (distal LAD) V5- V6 Antero-lateral (LAD or LCX) I, aVL Lateral (LCX) II, III, aVF Inferior (RCA) V7 – V9, ST depression V1- V3 with tall R waves Posterior (PDA) ST-segment elevations or Q waves in leads II, III, and aVF on ECG signify a likely inferior MI, supplied by the right coronary artery.
Notes & Notes for MRCP
By Dr. Yousif Abdallah Hamad
Coronary arterial dominance • Right-dominant (∼85% of the population): posterior descending artery (PDA) supplied by the RCA • Left-dominant (∼8% of the population): PDA supplied by the left circumflex artery (LCX) • Codominant (balanced; ∼7% of people): PDA supplied by both RCA and LCX Coronary circulation The left atrium is the posteriormost part of the heart, located directly in front of the esophagus. It can be visualized using TEE. The right ventricle is the anteriormost part of the heart and is at greatest risk of injury following chest trauma.
Jugular venous pulse (JVP)
Notes & Notes for MRCP
By Dr. Yousif Abdallah Hamad
Chapter 5
Cardiology
Clinical importance of JVP • providing information on right atrial pressure, • may provide clues to underlying valvular disease. • A non-pulsatile JVP is seen in superior vena caval obstruction. • Kussmaul's sign describes a paradoxical rise in JVP during inspiration seen in constrictive pericarditis.
JVP waves and abnormalities Wave Description Abnormalities a wave • The first peak caused by atrial contraction c wave • The second peak caused by tricuspid valve closure, contraction of the right ventricle, and bulging of the tricuspid valve into the right atrium x descent • A drop in JVP caused by atrial relaxation during ventricular systole • Absent in: o Tricuspid valve regurgitation o Right heart failure v wave • The third peak caused by venous refilling of the right atrium against the closed tricuspid valve • Prominent in: o Tricuspid valve regurgitation o Right heart failure y descent • A drop in JVP caused by decreased right atrial pressure as blood flows into the right ventricle after opening of the tricuspid valve Cannon 'a' waves • Caused by atrial contractions against a closed tricuspid valve • Causes Regular cannon waves ventricular tachycardia (with 1:1 ventricular-atrial conduction) atrio-ventricular nodal re-entry tachycardia (AVNRT) Irregular cannon waves complete heart block A left sided internal jugular central venous catheter has been inserted and you are reviewing the chest radiograph to check the position of the tip of the catheter. What is the safest position to leave the catheter tip? In the lower superior vena cava
Central venous access of the Subclavian Vein
Anatomy
•
Each subclavian vein is a continuation of the axillary vein and runs from the outer
border of the first rib.
•
The subclavian and internal jugular vein unite to form the brachiocephalic vein,
subsequently the left and right brachiocephalic veins unite to form the superior vena cava.
Procedure
•
Left-sided subclavian access is associated with lower rates of catheter malposition
and vessel trauma. It is preferred when immediate cardiac access is needed (eg,
temporary transvenous pacer and pulmonary artery catheter insertion) since the guidewire
and catheter are more easily directed into the superior vena cava and right heart.
•
The optimal point of needle insertion :
1 cm inferior to the junction of the middle and medial third of the clavicle.
Notes & Notes for MRCP
By Dr. Yousif Abdallah Hamad
• Absent in atrial fibrillation • cv wave : severe tricuspid valve regurgitation • Prominent in: o Tricuspid valve regurgitation o Constrictive pericarditis • Absent in: o Cardiac tamponade o Tricuspid valve stenosis
Notes & Notes for MRCP
By Dr. Yousif Abdallah Hamad
Chapter 5
Cardiology
Advantages • the cleanest site for central venous access (lower potential for infection). • It also the most tolerated by patients. • consistent landmarks (lower potential for arterial injury compared with other sites of access). Complications • Arrhythmias (e.g. premature atrial and ventricular contractions) caused by contact of the guidewire to the right atrium. • Venous air embolism, pneumothorax, and pneumomediastinum are other common complications of central line placement. • subclinical pneumothorax even in the hands of experienced clinicians. Central venous access • Ultrasound guidance improves initial cannulation success. • Obtain a postprocedural chest x-ray to confirm catheter position and exclude pneumothorax in jugular and subclavian catheters. Femoral catheters do not require radiographic confirmation and can be used immediately following insertion. • The internal jugular vein are a commonly used site for central venous access. The distal tip of jugular catheters should lie in the lower superior vena cava. Carotid artery puncture is a well-recognized complication. • Femoral site cannulation is often recommended as a secondary site due to higher rates of delayed complications.
Subclavian steal syndrome Brainstem features (vertigo, diplopia, dysarthria, and drop attacks) with disparity in BP > 15 mm Hg and pain precipitated by exercise →Subclavian steal syndrome Pathophysiology • Stenosis of the subclavian artery proximal to the origin of the vertebral artery → hypoperfusion distal to the stenosis → reversal of blood flow in ipsilateral vertebral artery → compensation through collateral arteries → reduced blood flow in the basilar artery → reduced cerebral perfusion upon exertion involving the affected arm • characterized by retrograde flow into the vertebral or internal thoracic arteries, due to stenosis and/ or occlusion of the subclavian artery. What is the most likely mechanism that maintains blood flow to the affected extremity? • Blood from the contralateral vertebral artery is shunted away from the basilar artery (away from the brainstem) and retrograde into the ipsilateral vertebral artery to supply the affected arm . Causes • Atherosclerosis • Takayasu's arteritis Symptoms • The most common symptoms are those related to upper limb ischemia (arm pain and numbness, especially during exertion and exercise with the arm above the head, such as painting a wall.)
Notes & Notes for MRCP
By Dr. Yousif Abdallah Hamad
• brainstem features due to vertebrobasilar insufficiency such as: Vertigo, Diplopia, Dysarthria, and Drop attacks. • blood pressure is different between the upper limbs by at least 15 mmHg. Diagnosis • Duplex ultrasound is the best initial radiological test shows reversal of blood flow (retrograde flow in the ipsilateral vertebral artery) • Angiography of the subclavian vessels (MRA) is the most accurate test. Management • Most patients require no intervention • Symptomatic patients: angioplasty and stenting or surgical revascularization Pathophysiology of subclavian steal syndrome Under normal conditions, the subclavian artery distributes blood equally to the arteries in the brain and arms (A). If there is stenosis of the subclavian artery proximal to the origin of the vertebral artery, this leads to hypoperfusion of the upper extremities on the affected side (B). This is compensated by a contralateral circulation, in which there is increased blood flow from the unaffected side to the affected side via the vertebral arteries. As a result, there is hypoperfusion of the vertebrobasilar territory and corresponding central nervous system symptoms.
Atrial natriuretic peptide (ANP) Secretion • Released from atrial myocytes (right > left) in response to blood volume and atrial pressure. • Acts via cGMP
Notes & Notes for MRCP
By Dr. Yousif Abdallah Hamad
Chapter 5
Cardiology
ANP secretion pathway and actions • ↑ Volume → ↑ atrial stretch receptors stimulation→ release of ANP from atrial cardiomyocytes which results in: ↑ Excretion of NaCl and water by the kidneys (via afferent arterioles dilations and efferent arterioles constriction) ↓ Na+ reabsorption at the renal collecting tubule (via ↑ cGMP) Inhibition of renin Vasodilation of veins and arteries (↓ preload and ↓ afterload) • ↓ Volume → ↓ atrial stretch receptors stimulation → ↓ Release of ANP → ↓ excretion of NaCl and water by the kidneys How is the "aldosterone escape" mechanism mediated by atrial natriuretic peptide (ANP)? • ANP causes cGMP-mediated dilation of the afferent arteriole and constriction of the efferent arteriole, promoting diuresis and counteracting the effects of aldosterone
B-type (Brain) Natriuretic Peptide (BNP) Definition • B-type natriuretic peptide (BNP) is a hormone produced mainly by the left ventricular myocardium in response to strain (myocyte stretch). Mechanism of action • Similar physiologic action to ANP with longer half-life. • ↑ intracellular smooth muscle cGMP →arterial and venous smooth muscle vasodilatation →↓ pre-load → ↓BP • ↓ sodium reabsorption, leading to natriuresis and diuresis. • suppresses both sympathetic tone and the renin-angiotensin-aldosterone system Causes of raised BNP levels • heart failure is the most obvious cause • age over 70 years, • ventricular hypertrophy, ischaemia, tachycardia, hypoxaemia [including pulmonary embolism], chronic obstructive pulmonary disease, • renal dysfunction [eGFR less than 60 ml/minute/1.73 m2] • sepsis, • diabetes • cirrhosis of the liver • BNP synthesis is increased by thyroid hormones as well as glucocorticoids, endothelin-1, angiotensin-II, and tachycardia, independent of the haemodynamic effects of these factors. Factors which reduce BNP levels
Notes & Notes for MRCP
By Dr. Yousif Abdallah Hamad
• Obesity • African or African–Caribbean family origin • treatment with diuretics, angiotensin-converting enzyme (ACE) inhibitors, beta‑ blockers, angiotensin II receptor blockers (ARBs) or mineralocorticoid receptor antagonists (MRAs) Clinical uses of BNP • Diagnosing patients with acute dyspnoea (very good negative predictive value for heart failure). (NICE guidelines - 2018). NT-proBNP level Note ˃ 2,000 ng/litre Refer urgently to specialist and echocardiography within 2 weeks. Between 400 and 2,000 ng/litre Refer to specialist and echocardiography within 6 weeks. ˂ 400 ng/litre makes a diagnosis of heart failure less likely • Prognosis in patients with chronic heart failure: very high levels of NT-proBNP carry a poor prognosis • Guiding treatment in patients with chronic heart failure: effective treatment lowers BNP levels Brain natriuretic peptide (BNP) • BNP a hormone secreted from ventricular myocytes in response to ventricular volume overload, as seen in congestive heart failure. • BNP acts on the renal collecting duct to decrease sodium reabsorption and increases glomerular filtration rate, leading to urinary sodium loss. • BNP has a good negative predictive value, so a patient with a normal BNP likely does not have heart failure.
Cardiovascular physiology • The basic muscle unit of the myocardium Sarcomere • The normal resting cell membrane potential of a cardiac myocyte - 90 Mv • Left ventricular ejection fraction (LV EF) = ( Stroke volume/end diastolic volume ) * 100% • Cardiac output (CO) measure how much blood ejected by the heart in one minute. CO = Stroke volume (SV) x Heart rate (HR) • Stroke Volume (SV) volume of blood ejected per heart beat = CO/HR = End-Diastolic Volume (EDV) - End-Systolic Volume (ESV) • Stroke volume is decreased by hypovolaemia • normal ejection fraction is more than 55% of the blood volume. • In systolic dysfunction, EF is low. In diastolic dysfunction, EF is normal (called HF with preserved LV EF) e.g. hypertrophic heart failure • Pulse pressure = Systolic Pressure - Diastolic Pressure Factors which increase pulse pressure less compliant aorta (this tends to occur with advancing age) increased stroke volume Factors which reduced pulse pressure Reduced stroke volume, high aortic compliance,
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