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
