L32: Syncope (Swift) Flashcards
Presyncope
An incomplete form of syncope often involving hindlimb or generalized weakness
Seizure
- Abnormal excessive paroxysmal synchronous discharge in a population of neurons
- a dysfunction of grey matter which may be primary or secondary to metabolic abnormality
- can be tonic/clonic or psychomotor
Narcolepsy/cataplexy
- animal collapses into sleep or muscle paralysis respectively
- can be induced by excitement or eating
- can be roused by stimulation
- often many times daily
- inherited forms in poodles, labs, dobies
Neuro vs. cardiac localization
Neuro: usually occurs at rest, takes long time to recover, assoc. with seizures
Cardio: usually occurs with excitement, recovers quickly
PE in syncope/seizure patients
- mm color
- pulses: hypo or hyper kinetic?
- jugular veins: pulses and distention
- neuro deficits?
- auscultation (gallop rhythm? Murmur?)
PDA –> pulses?
Hyperkinetic pulse
Pulmonic stenosis –> pulses?
Weak, attenuated pulses
What can cause gallop rhythm?
DCM, HCM
2 things assoc. with Left basilar mumur
Aortic or pulmonic stenosis
Things to assess when you hear a murmur
1) Loudness (I-VI)
- grade III is as loud as heart sounds
2) point of maximal intensity
3) radiation
4) timing
5) character (does it get louder or quieter, or equally loud?)
Ddx for collapse (categories)
Cardiac** Resp Peripheral vascular Haematological Metabolic Endocrine Muscular Neurological Skeletal Neuromuscular Iatrogenic
Resp. Causes of collapse
Hypoxia (upper or lower tract dz, pleural dz) Pulmonary hypertension (ie. HWD) Hyperventilation Cough Oslerus osleri
Peripheral vascular dysfunction causes of collapse
- neurocardiogenic syncope (vasovagal syncope)
- carotic sinus hypersensitivity (ie. Pulling on leash causes bradycardic event)
- postural hypotension (BP low after lying down)
- hyperventilation
Neurocardiogenic syncope
Simultaneous Vasodilation and bradycardia, often in response to adrenergic surge
-mismatch between what body wants to do and what HR and BP are doing
Haemotological disorders causing collapse
- anemia
- polycythemia (thick blood)
- myeloproliferative diseases
Endocrine disorders causing collapse
- hypo (causes collapse) and hyperadrenocorticism (causes hypertension, arrhythmias)
- DM (both hypo or hyerglycemia)
- phaeochromocytoma (release of epi/norepi can cause sudden tachycardia and collapse)
- hypothyroidism (usually causes just weakness)
- DKA
Muscular disorders causing collapse
- polymyositis
- muscular dystrophy
- myopathy 2ary to hypoK, steroids, or myotonia
- labrador and retriever myopathy
- mitochondrial myopathy
Polymyositis
A systemic, noninfectious, maybe IM, inflammatory muscle disorder
-may be acute or chronic and progressive
Neuro disorders causing collapse
- cerebral emboli/thrombi/hemorrhage
- space occupying lesions
- atherosclerosis
- seizures
- vestibular or cerebellar dz
- spinal trauma
- narcolepsy/cataplexy
Skeletal disorders causing collapse
- degenerative joint dz
- polyarthritis
- hypertrophic osteodystrophy
- bilateral ACL rupture
Neuromuscular disorders causing collapse
- myasthenia gravis
- botulinism
- peripheral polyneuropathies
Iatrogenic causes of collapse
- Digoxin (CHF drug that can cause bradyarrhythmias)
- Vasodilators
- Quinidine (used to control A fib in horses)
Syncope
Sudden transient loss or depression of consciousness and postural tone resulting from transient and diffuse cerebral malfunction with spontaneous recovery
-often due to deprivation of energy substrates (glucose or oxygen) as a result of decreased or brief cessation of cerebral blood flow
Congenital cardiac causes of collapse
- obstruction to outflow (AS, PS, atrial tumor, valvular endocarditis)
- cyanotic heart disease (tetralogy of fallot, VSD/PDA)
- severe AV valve dysplasia
How does obstruction of outflow –> collapse?
Body needs more blood in circulation but heart can’t push against the obstruction to increase outflow. As a result, the body vasodilates and BP plummets
Heart is perfused during systole or dyastole?
Dyastole
Why have hard time perfusing the heart with AS?
LV can become thickened (more tissue to perfuse). If a tachycardic event occurs, HR increases and dyastole (the time when heart is perfused) gets shorter. Lack of perfusion can –> hypoxia
4 parts of tetralogy of fallot
- pulmonic stenosis
- RV hypertrophy
- large VSD
- overriding of the aorta
*creates resistance between pulmonary and systemic circulation
Consequences of tetralogy of fallot
- reduced pulmonary blood flow (fatigue, shortness of breath)
- generalize cyanosis due to mixing of blood from R and L ventricles
Mm in reverse shunting PDA
- peripheral mm can look normal while core mm will look cyanotic
- secondary to blood entering the brachiocephalic trunk
If have severe AV valve dysplasia, will demonstrate syncopal episode when?
When become very stressed
What things cause cyanosis?
Pulmonary hypertension
Pulmonic stenosis + VSD
Acquired cardiac diseases causing collapse
- severe AV valve dz
- systolic dysfunction - DCM
- pericardial disease
- pulmonary hypertension
- certain arrhythmias
What arrhythmias can cause collapse?
Bradyarrhythmias: 3rd degree AV block, and less commonly 2nd degree or sick sinus syndrome
Tachyarrhythmia: V tach and certain supraventricular arrhythmias
What is dilated in DCM?
LV and LA
4 main categories of ddx for collapse
1) cardiovascular
2) respiratory
3) internal medicine (haematological, metabolic, endocrine)
4) neuromuscular skeletal
Treatment of ventricular tachycardia that is affecting CO
- turn off anesthetic gases
- make sure oxygenated
- give IV lidocaine
- consider K if lidocaine doesn’t work
- other drugs: short acting beta blocker, esmolol, sotalol
Class 1 anti-arrhythmic drugs
Sodium channel blockers (ie. Lidocain, procainamide, etc.)
*used for muscles of ventricle
Class 2 anti-arrhythmics
Beta blockers
-esmolol, atenolol, propranolol, metopralol
*used for regulating SA and AV nodes
Class 3 anti-arrhythmics
K channel blockers
-sotalol, amiodarone
*used for muscles of ventricle
Class 4 anti-arrhythmics
Ca channel blockers
-diltiazem, verapamil, nefedipine
*used for regulating SA and AV nodes
Pimobendan
Increases contractility and dilates peripheral vascular system (vasodilator)
V tach can –> CHF
:)
Signs of atrial fibrillation on ECG
- no p waves
- supraventricular
- irregular
- fast (ie. 200 bpm)
How can neoplasia cause pericardial effusion?
Tumor rubbing up against heart wall can rupture vessels or obstruct lymphatic drainage to pericardium –> effusion
Causes of syncope (cardiac)
1) poor output (due to decreased contractility, poor diastolic filling with tachycardia, or reduced diastolic filling due to loss of atrial contraction)
2) undiagnosed ventricular arrhythmia
Treatment aims of preventing cardiac syncope
- slow HR
- convert to normal sinus rhythm
- provide inotropic support
- control CHF
- goal of drugs = prolong AV nodal refractory period
Tx of A fib
- digoxin
- Ca channel blocker (diltiazem)
- beta blockers (don’t use if CHF present; beware of negative inotropic actions)
- goals = control rate and rhythm; want to slow HR
Collapse that is preceeded by exercise, stress, cough, gagging, vomition, urination, or defecation is more likely to represent SYNCOPE than SEIZURE
:)
Pulse pressures are reduced with:
Poor CO often caused by systolic failure, aortic stenosis, pericardial effusion, or tachyarrhythmias
Pale mm (cyanosis) could be caused by:
Poor CO, often due to severe arrhythmias or poor contractile function ie. DCM
Ascites in heart failure is:
Modified transudate
Muscular and neuromuscular disorders tend to cause:
Episodic weakness and collapse
One of the most common cardiac causes of syncope
Advanced AV block
Dogs with advanced degenerative mitral valve disease can develop neurocardiogenic bradycardia, often in dogs with pulmonary hypertension. Causes episodic syncope/collapse
:)
T: any cause of hypoxia can cause syncope
:)
Hyperventilation results in:
Cerebral arterial vasoconstriction and peripheral vasodilation reducing cerebral perfusion
Drugs that can cause iatrogenic syncope
- Digoxin (toxicity can cause heart block, AV dissociation, or slow junctional rhythm)
- diuretics (due to volume depletion)
- vasodilators
- quinidine (can cause severe arrhythmia)
How does hypoadrenocorticism cause syncope?
- hypovolemia
- hyponatremia
- hyperkalemia
How does hypothyroidism cause syncope?
2ary to bradycardia or peripheral neuropathies
How does postural hypotension cause syncope?
Both systolic and diastolic pressures fall
Metabolic disorders –> syncope?
Hypo or hypercalcemia Hypo or hyperglycemia Hypo or Hyperkalemia Hyponatremia Acidosis Hyperthermia Hepatic encephalopathy
Hypercalcemia is most often caused by
- neoplasia
- hypoadrenocorticism
- renal disease
- primary or secondary hyperparathyroidism
- bone mets
Dogs with hepatic encephalopathy often have seizures following high protein meals (may be 2ary to congenital PSS or hepatic insufficiency and cirrhosis)
:)
