Cardio: Syncope Flashcards
Syncope
Partial or complete loss of consciousness due to an oxygen shortage to the brain - quick collapse, quick recovery
Weakness
Loss of muscular strength - either constant or episodic
What is weakness often associated with in diseased animals?
Systemic illness
Is cyanosis common with weakness, and when does it occur?
+/- Cyanosis - more prominent after collapse
How do you differentiate between syncope and seizures?
- BOTH = may see urination, defecation, or vocalization
- Seizures = post-ictal for a prolonged period of time
Differentials for syncope (16)
1) Decreased CO = poor systolic function, CHF, ouflow obstruction (stenosis)
2) Bradyarrhythmias = sick sinus, atrial standstill, 2nd/3rd AV block
3) Tachyarrhythmias = V-tach, V-fib, supraventricular v-tach
4) Pulmonary hypertension
5) Hypoglycemia
6) Vasovagal event
7) Embolism to the brain - air, bacteria, thrombus
8) Respiratory disease associated with hypoxia
9) Hypotension
10) Anemia
11) Metabolic = lyte abnormalities, Cushing’s, hypothyroidism
12) Neuro disease
13) Musculoskeletal disease
14) Neoplasia
15) Drugs and toxins
16) Infections
Sinus arrest - ECG
SA node’s failure to fire = results in a pause that is greater than two R-R intervals
Typical breeds for sick sinus syndrome
- Female miniature Schnauzers
- Westies
- Cocker Spaniels
Two things required (and found) to non-definitively diagnose sick sinus syndrome
- Bradyarrythmias
1) ECG findings = sinus arrest, +/- sinus tachycardia
2) Clinical signs = pre-syncopal ataxia and weakness + syncope
Helpful “definitive” diagnostic test for sick sinus syndrome
> Atropine response test = anticholinergic, removes any vagal tone
- Normal = see unleashed sympathetic tone and tachycardia
> SSS patients = won’t increase their HR by more than 50%
Treatment for sick sinus syndrome
Pacemaker placement
Typical breeds for atrial standstill
English Springer Spaniels - due to atrial fibrosis
Atrial standstill - ECG
- Bradycardia = 40-60 bpm
- Regular rhythm w/ ABSENCE OF P waves
- Supraventricular escape rhythm (coming from near the AV node, just above the Bundle of His) = upright and narrow QRS complexes (went through the His-Purkinje)
Two main causes for atrial standstill
1) Primary atrial fibrosis - common in English Spring Spaniels
2) Hyperkalemia (common in blocked cats) = paralyzes the atria
Result of an atrial standstill patient with an atropine response test
HR will not increase like normal
Treatment of atrial standstill
- Correct any hyperkalemia
- Pacemaker if there’s persistent atrial standstill
1st degree AV block - ECG
> Prolonged PQ interval (w/ or w/o bradycardia)
- “Lazy gatekeeper”
Causes of 1st degree AV block (4)
1) Drugs - Ex: B-blockers, Ca+ channel blockers, digoxin
2) Increased vagal tone - GI, respiratory, or neuro disease
3) Primary cardiac disease - degenerative AV changes
4) Tachycardias that shorter the PR/PQ interval
2nd degree AV block - ECG
- Intermittent failure of the AV nodal conduction (“sleepy gatekeeper”)
- Some P waves are conducted through to His-Purkinje fibers, some are not
» P waves associated with QRS, and some not
*May cause a ventricular escape complex if AV block causes significant bradycardia
Difference between Mobitz type I and II 2nd degree AV block on ECG
- Mobitz type I = variation in PR interval w/ some loss of AV node conduction
- Mobitz type II = fixed PR interval with some loss of AV conduction, +/- ventricular escape rhythms
Cause of Mobitz type I - 2nd degree AV block
Secondary to increases in vagal tone - drugs, respiratory or neuro disease
Cause of Mobitz type II - 2nd degree AV block
AV nodal pathology - fibrosis
How do we differentiate between Mobitz type I and II 2nd degree AV block?
Atropine response test - AV block is usually reconciled with type I (gets rid of the vagal tone), but persists with type II
Treatment for Mobitz Type I - 2nd degree AV block
Treat the underlying cause of vagal tone - treat GI, respiratory or neural disease, stop administering drugs
Treatment of Mobitz Type II - 2nd degree AV block
Pacemaker if bradycardic
3rd degree AV block - ECG
> COMPLETE AV block
- NO P waves are conducted through the AV node to the ventricles
+/- Ventricular escape rhythms may be present
Causes of 3rd degree AV block (2)
1) AV node pathology - fibrosis, infiltrative disease, VSD’s
2) Severe drug intoxication - beta or Ca++ channel blockers, digoxin
Response of patients with 3rd degree AV block to the atropine response test
Increased P wave rate (SA node fires more), but no increase in the ventricular escape rate
Treatment for 3rd degree AV block
Pacemaker
Three types of tachyarrhythmias that can cause syncope
1) V-tach
2) V-fib
3) Supraventricular tachycardia
Treatment for v-tach
Lidocaine
Treatment for v-fib
Defibrillation
Why does pulmonary hypertension cause syncope?
Right side of the heart cannot propel enough blood to the brain, against the high pulmonary pressure = hypoxia to the brain
What is a vasovagal event?
Low HR and low BP secondary to a reflex (defecating, etc)
Diagnostic tests for a patient with suspected syncope (8)
- PE and history
- ECG
- Thoracic rads
- Echocardiogram
- Blood pressure
- Blood work - CBC, chem
- Heart monitor = “Reveal”
- Atropine test
Diagnostic tests for a patient with collapsing weakness
- Metabolic work-up
- Neuro exam - Myasthenia gravis titers
- ECG
+/- Echo - Blood pressure
+/- Heart monitor
Diagnostic tests for a patient with suspected seizures
Neuro work up
Definition of heart disease
Physical or functional abnormality of a component of the cardiovascular system (mainly the heart)
Definition of heart failure
Physical state in which the CO is inadequate to meet the needs of organ systems for metabolism, despite adequate preload (not due to hypovolemia or dehydration) –> SHOWING clinical signs
What four variables play a role in determining stroke volume?
1) Systolic function = heart contractility
2) Pre-load = atrial pressure, end of diastole
3) After-load = resistance to blood leaving the heart (SVR)
4) Diastolic function = how fast and completely the heart relaxes
Difference between systolic and diastolic dysfunction
- Systolic = inadequate pumping, poor contractility, Ex: DCM
- Diastolic = inadequate relaxation, Ex: HCM
True or false - atrial pressures rise with both systolic and diastolic dysfunction
TRUE
Three main diagnostic techniques to differentiate heart disease from failures (and some others…)
1) History w/ more questions (Cough? Sleeping?)
2) PE
3) Thoracic radiographs
4) Echo
5) ECG
6) CBC, chem
Key words you may hear with heart failure (7)
- Weakness
- Exercise intolerance - do they have energy to exercise
- Cough
- Difficulty breathing
- Lethargy
- Collapse, syncope
- Abdominal swelling = ascites
Things to focus on in a PE, with a suspect cardio patient
- History, signalment
- Job or purpose
- Thoracic auscultation
- Peripheral pulses
FINISH THE WHOLE PE
What makes the heart sounds we auscult?
Blood stopping suddenly
What makes the S1 heart sound?
Blood stopping as it hits the AV valve - SYSTOLE
What makes the S2 heart sound?
Blood stopping as it hits the closed aortic and pulmonic valves - DIASTOLE
What makes the S3 heart sound?
Sudden end of rapid ventricular filling, pulling blood in from the atria - DIASTOLE
What makes the S4 heart sound?
Blood stopping as the atria contract, forcing it into the ventricles - DIASTOLE
What does a gallop rhythm indicate?
Stiff ventricles
What heart sounds do we normally hear in dogs?
S1 and S2
What heart sounds do we normally hear in cats?
S1 and S2, but it may summate into a single sound
What three things do we use to characterize heart murmurs?
1) Point of maximal intensity - where?
2) Loudness or grade
3) Timing - diastole, systole
What type of murmur is occurring if you hear the murmur while you feel a peripheral pulse?
Systolic murmur
What type of murmur is occurring if you hear the murmur in between heart beats?
Diastolic murmur
Four types of timing with heart murmurs
1) Diastolic
2) Systolic
3) Systolic-diastolic
4) Continuous
