Transcript B2B - Cardiac Surgery Dr. Khanh Lam

A Case Based Review of Cardiac
Surgery Objectives for the MCC
Qualifying Exam 2009
B-K Lam, MDCM
University of Ottawa Heart Institute
Objectives
• Using demonstrative cases, this lecture will highlight the
cardiac surgical aspects of the differential diagnoses
included in the MCC qualifying exam objectives
• MCC Objectives for the Qualifying Examination covered
in this review:
– Cardiac arrest (p. 13)
– Chest discomfort (p. 14)
– Dyspnea (p. 27)
• Acute (p. 27-1)
• Chronic (p. 27-2)
– Diastolic murmur (p. 62-1)
– Heart sounds pathological (p. 62-2)
– Systolic murmur (p. 62-3)
– Trauma
• Chest injuries – heart injury (p.109-4)
Case 1
• A 48 year-old man is awakened early in the
morning by sharp anterior chest pain that
radiates to his back. He presents to the
emergency room several hours later reporting
that his pain has subsided but he is very short of
breath. His past medical history is significant for
poorly controlled hypertension. On examination,
BP is 150/40, P100, RR 24, 88% on 2L/min of
O2. His cardiac exam is noticeable for an absent
S2, a loud 4/6 diastolic murmur; he also has an
accompanying systolic ejection murmur. You
also notice that his left carotid pulse is weaker
than his right.
Case 1 - Questions
•
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What is the differential diagnosis?
Why is this patient short of breath?
Why is his left carotid weak?
What diagnostic tests would you order?
In general, how do you classify this disorder?
How would you classify it in this patient?
What therapy would you implement in the
emergency room?
• How would you further manage this patient and
why?
“Top 3” DDx
•
•
•
•
MI
Aortic Dissection
PE
(Tension Pneumothorax)
Acute dyspnea - Ddx
• Cardiac
– Ischemic heart disease
(acute myocardial
ischemia)
– Myocardial dysfunction
(congestive heart failure)
• Ischemic/Hypertensive
cardiomyopathy
• Dilated (idiopathic,
alcoholic,
hemochromatosis)
• Pericardial disease
(tamponade)
• Valvular (Mitral
regurgitation, Aortic
Insufficiency)
• Pulmonary
– Upper airway
• Aspiration
• Anaphylaxis
– Ventilatory pump:
• Pleura (pneumothorax),
• Airways (bronchitis,
bronchospasm)
– Gas exchanger
• Pulmonary embolus
• Pneumonia (viral,
bacterial, atypical, fungus)
– ARDS
• Vasculitis (Wegener,
Goodpasture)
– Respiratory control
(metabolic acidosis, ASA
toxicity)
Weak L carotid
• Dissection flap causing obstruction of true
lumen
Diagnostic Tests
•
•
•
•
•
•
CK, TNt
ECG
CXR
TEE
CT
MRI
Classification
Debakey
A
Stanford
B
What type of dissection
• Stanford A
• Debakey I or II
Acute Management
• Beta Blockade
– Reduces wall stress on aorta
– dP/dT
– Rupture prevention
• Antihypertensives
– Reduces shear stress on the aorta
– Anti-impulse/propagation therapy
– Nitroglycerine
– Nitroprusside
Definitive Therapy
• Surgery
• Type A dissection is a surgical emergency
• Terrible natural history:
– “1%/hour” rule
• 50% dead in 48 hours
• 70% dead by 1 week
• Medical Tx = 60% mortality rate
– Modes of death
• Rupture with hemopericardium, hemomediastinum or
hemothorax
• Organ dysfunction
Case 2
• An 19 year old male is received a single stab
wound to the chest outside a night club. He is
brought to the ER, conscious and complaining of
pain and shortness of breath. On examination,
you observe a 3cm wound just left of his
sternum in the 5th interspace. His BP is 85/60,
P100, RR18, 95% on 2L/min of O2. His skin is
slightly mottled and cool; his JVP is 8cm. By
auscultation, air entry is fair bilaterally, heart
sounds are muffled and peripheral pulses are
weak. The rest of the physical is normal. Shortly
after arriving in the patient becomes
unresponsive. Pulses are not palpable, the
monitor shows normal sinus rhythm.
Case 2 - Questions
•
•
•
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What are the most concerning clinical signs?
What is the diagnosis?
What structure is most likely injured?
What other structure should you be worried
about?
• Prior to arrest what diagnostic tests would you
order?
• What type of cardiac arrest is this and why has it
occurred?
• How would you manage the arrest?
Concerning Clinical Signs
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•
•
Hypotension
Tachycardia
Muffled heart sounds
JVP elevated
Weak peripheral Pulses
CARDIAC TAMPONADE!
Commonly injured
• Right ventricular injury most common
– Sits anteriorly in the mediastinum / LV posterior
– RV 43%, LV 34%, RA 16%, LA 7%
• Fatality rate 70-80%
• Survival probability depends on:
– Degree of anatomic injury
– Occurrence of cardiac standstill
• Beck triad only in 10-30% of tamponade cases
• Pericardiocentesis: 80% false negative
• FAST U/S: 95% sensitivity
Associated Chest Injuries
• Cardiac
– Rule out LAD coronary artery injuries
– Valvular injury
• Lung (pneumo/hemothorax)
• Tracheobronchial
– 75-80% involvement of cervical trachea
• Esophagus (<1%)
• Diaphragm (45%)
– 15% >2cm, 13% missed with 85% returning with hernia)
• Thoracic great vessel (0.3-10%)
– 90% due penetrating trauma, 71% hospital survival
Diagnostic Tests
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•
•
•
•
Labs
ECG
CXR
Echo
FAST U/S
Cardiac Arrest
• PEA arrest
• Cardiac tamponade prevents adequate
cardiac filling and subsequently cardiac
output
• This is not hypovolemia
Arrest Management
•
•
•
•
ABC’s
Intubation
CPR
Manage underlying cause
– 5H’s & 5T’s
– ER thoracotomy
– pericardiocentesis
Copyright ©2005 American Heart Association
Circulation 2005;112:IV-58-IV-66
Case 3
• An unrestrained 23 year old driver ran a
red light and collided with another vehicle
in a t-bone fashion. He is brought to the
ER, conscious complaining of sternal pain.
On examination, you observe bruising on
his anterior chest. HR 115, BP 90/50 and
RR15. The patient’s JVP is flat and lungs
are clear. A CXR is performed and it
shows a widened mediastinum, a pleural
cap and a fracture of the first rib.
Case 3 - Questions
• Explain the physical findings.
• What is your differential diagnosis?
• What are the mechanisms of injury in blunt
trauma?
• What tests would you order?
• What are the classic CXR findings for this
condition?
• What is the usual anatomy and mechanism of
this injury? (Where does it occur and why?)
• What is the initial management?
• What are the definitive management options?
Symptoms
• Hypotension
• Tachycardia
• Low filling pressures
• Hypovolemic shock
Blunt thoracic trauma - Ddx
• Aorta
– Traumatic aortic disruption
• Cardiac
– Contusion
– Rupture
– MI
• Pulmonary
–
–
–
–
Pneumothorax
Hemothorax
Pulmonary contusion
Tracheobronchial injury
• Rib fracture/flail chest
• Diaphragm rupture
• Esophageal rupture
Mechanisms of Injury
• Compression
– sternum and vertebrae
• Fractured sternum
– RV or aorta
• Torsion: attachment points
–
–
–
–
Vena cavae to RA
PV’s to LA
Origin of arch vessels
Aortic isthmus
• Rise in pressure
– Chambers or valves
Pretre et al NEJM 97
Investigations
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CBC
ECG
CXR
FAST U/S
Echo/TEE
CT Thorax (if stable)
Angiogram
CXR findings
• Wide mediastinum (supine
CXR > 8 cm; upright CXR >6
cm)
• Obscured aortic knob;
abnormal aortic contour
• Left "apical cap" (ie, pleural
blood above apex of left lung)
• Large left hemothorax
• Deviation of nasogastric tube
rightward
• Deviation of trachea rightward
and/or right mainstem
bronchus downward
• Wide left paravertebral stripe
Anatomy and Mechanism
• Aortic isthmus
• Deceleration
• Greatest shear force
Initial management
• Advanced Trauma Life Support® (ATLS®)
• ABCD
• Secondary survey
Definitive Management
• Stat surgical consult as poor natural
history
• Conservative RX
• Open repair vs Stent graft
Surgery VS Stenting
*
• Endovascular stent:
– Location beyond
subclavian artery
– Minimum of 5mm
landing zone
– Diameter <36mm
– Absence of thrombus
in fixation areas
– Non-tortuous
– Adequate access
Case 4
• A surprisingly healthy and active 78 year old
female presents to you with chest heaviness
when she walks. On further questioning she
admits to some dyspnea as well and she has
been awakened from sleep with dyspnea
several times recently. Her only past medical
history is a hysterectomy. On physical
examination, the BP is 100/80 and the pulse is
80 and regular but slow and delayed in quality.
By auscultation, there is a 3/6 crescendodecrescendo systolic ejection murmur at the
right upper sternal border with radiation to the
neck. There is no diastolic murmur noted. The
rest of the physical exam is normal.
Case 4 - Questions
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What is your differential diagnosis?
What investigations would you order?
In order of prevalence, what are the three most
common causes of aortic stenosis?
In this patient, how do you explain the angina?
Name the two most commonly used types of valves in
aortic valve replacement surgery?
List the advantages and disadvantages of the valves
you identified in the previous question?
How is Coumadin monitored? What are the respective
therapeutic ranges for a patient with an aortic and
mitral prosthesis?
What type of valve would you recommend for this
woman?
Chronic Dyspnea - Ddx
Cardiac
• Valvular
– Aortic Stenosis
– MS, AI, MR
• Ischemic
– CAD with SEM
• Cardiomyopathic
Pulmonary
• Muscles/nerves/chest
wall
• Lungs/Pleura
– Restrictive
• Airways
– obstructive
• Gas exchange
Investigations
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•
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•
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CBC
CXR
ECG
Echo
Angiogram
AS Etiology
• Acquired
– Degenerative/Age related
• Congenital
– Bicuspid, unicuspid, quadracuspid
• Rheumatic
Angina in AS
Supply
Demand
• Increased LVEDP
• Hypertrophied
therefore decreased
• Increased LVEDP
diastolic coronary flow
• Decreased diastolic
pressure
Valve types
• Mechanical
• Bioprosthetic
Pros & Cons
• Mechanical
– Pros:
• Durability
• Large EOA
– Cons:
• Require anticoagulation
• Bioprosthetic
– Pros:
• Anticoagulation not
required
– Cons:
• Limited durability
• Smaller EOA
Coumadin
• Monitoring:
– INR
• Theraputic Range:
– Mechanical Aortic 2.0-3.0
– Mechanical Mitral 2.5-3.5