Atrial Arrhythmias Flashcards
What is ectopy? Single/couplet/triplet?
abnormal impulse formation not initiated by the SA node and rather from the atria, junctional, or ventricles
- SINGLE = 1 abnormal beat
- COUPLET = 2 abnormal beats
- TRIPLET = 3 abnormal beats
What are more than 3 abnormal beats in a row?
paroxysm
(aka: salvo, burst, run)
What is the difference between bigeminy and trigeminy?
BIGEMINY = normal beat followed by one abnormal beat (repetitive pattern)
TRIGEMINY = 2 normal beats then one abnormal beat (repetitive pattern)
Where does atrial/supraventricular ectopy come from? How does this affect the ECG?
above the ventricles - atrial myocardium or AV node
- P waves = abnormal morphology
- QRS = narrow (conduction still passes through AV node to bundle of His and Purkinje fibers)
What is the difference between atrial premature complexes (APCs) and atrial/supraventricular tachycardia (SVT)?
APC = one abnormal complex
SVT = multiple abnormal complexes
What are atrial premature complexes (APCs)? What are 4 signs on an ECG?
supraventricular premature beats usually occuring with normal sinus rhythm
- premature P and QRS +/- abnormal P wave abnormalities
- narrow, upright QRS complex resembling sinus beats
- short TP interval before QRS complex, which may bury previous T wave
- variable PR interval
What are APCs frequently associated with? Is treatment necessary?
atrial enlargement (not always pathologic)
treat underlying disorder
What is occurring in this ECG:
2 APCs
- premature P waves with abnormal morphology with non-compensatory pause
APCs vs. normal rhythm:
P wave came in too soon + pause for reset
APCs:
early P waves with abnormal morphology
What is occurring in this ECG?
APC @ 6th beat
What is atrial/supraventricular tachycardia?
rapid rhythm that originates above the ventricles, but not at the SA node —> ectopic focus = abnormal P waves, but hard to see during fast rates
- often starts with an APC (>3 is considered tachycardic)
- DOGS = >180 bpm
- CATS = >240 bpm
What is a paroxysmal atrial/supraventricular tachycardia?
abrupt stop and start to signs on ECG
What treatment is used for atrial/supraventricular tachycardia? In what patient is this most commonly seen?
slow HR to maintain cardiac output - vagal maneuvers, medication
dogs or cats with severe heart disease (LA enlargement)
What is the difference between supraventricular tachycardia and sinus tachycardia? How are each treated?
SVT = PATHOLOGICAL fast HR >200 bpm in dogs (rare in cats), where an APC initiates it and it has an abrupt start and stop; treat rhythm
ST = physiologic increase in SA nodal rate with upright P waves with HR usually <200 bpm in dogs and <240 bpm in cats; treat underlying cause
What is occurring in this ECG?
SVT
- APC initiates with abrupt start
- HR > 200 bpm
- cannot see P waves, but RR intervals are consistent
What is occurring in this ECG?
SVT —> sinus tachycardia
- 11 beats in 3 s = 220 bpm, then 8 beats in 3 s = 160 bpm
- look for underlying heart disease possibly causing SVT
What is occurring in this ECG?
sinus tachycardia
- upright P waves
- HR < 200 bpm
- consistent - no APC to start it off
When do signs of SVT occur? What are 3 options for treatment?
if cardiac output falls —> weakness, syncope
- correct underlying problem
- vagal maneuvers to increase vagal tone to slow conduction through AV node - ocular pressure, carotic sinus massage, diving reflex (sudden immersion of head in cold water)
- thump on chest, cardioversion
What are the main 2 acute pharmacologic therapies for SVT? Chronic therapy?
- calcium channel blockers (Diltiazem, Verapamil, Mexiltine) - minimal effect on vascular tone and inotropic state
- beta-blockers (Atenolol, Sotolol) - second option where vagal maneuvers and calcium channel blockers fail
Digoxin + beta-blockers + calcium channel blockers
What are 5 signs on ECG in cases of atrial fibrillation?
- rapid HR (~200-240 bpm)
- irregularly, irregular rhythm
- inconsistent RR intervals
- absent P waves
- F waves - chaotic electrical activity in atria with no discernable P waves
What is seen on physical exam in cases of atrial fibrillation? How does this affect cardiac output?
- irregularly feeling pulse (ventricular filling times vary)
- auscultation sounds like sneakers in a dryer
atrial muscle fibers are not coordinated and the atria no longer contribute to ventricular filling so there is decreased output
What is the most common cause of atrial fibrillation?
- pathologic, severe atrial enlargement —> common in dogs with DCM and cats with HCM
- cats may have one instance of Afib where there is no underlying disease
How are QRS complexes affected by atrial fibrillation?
- ventricular rate will be high, but the complexes are normal
- irregular rhythm due to AV activation of AV node randomly
What effect does atrial fibrillation have on the heart? What 3 things are seen with chronic cases?
increased myocardial oxygen consumption —> myocardial hypoxia due to little time for diastolic perfusion
- additional arrhythmias
- cardiac remodeling
- turbulent flow can lead to blood clots (need anticoagulants in these patients)
What is occurring in this ECG?
atrial fibrillation
- irregularly irregular QRS/HR
- absent P waves
- F waves
What is occurring in these ECGs?
atrial fibrillation
- irregularly irregular QRS!
What causes atrial flutter?
severe atrial enlargement causes rapid depolarization of atria (350-600/min) much faster than the ventricles causing up to 4 atrial beats (P) to every ventricular beat (QRS)
- types of SVT
What are 5 signs of atrial flutter on ECGs?
- rapid HR
- irregularly irregular rhythm
- inconsistent RR intervals
- absent P waves - F waves present (saw tooth pattern)
- multiple atrial beats to one ventricular beat
What is seen in this ECG?
atrial flutter
- inconsistent RR intervals
- very fast F waves, but not all are conducted
- several F waves for QRS complexes
What is seen in this ECG?
atrial flutter
- ~ 3 atrial beats per ventricular beat
What are the 3 key features for treating atrial fibrillation/flutter?
- lowering ventricular response
- slow conduction through AV node
- get the lowest HR possible without cardiovascular compromise (140-160 bpm)
What are 6 options for treating atrial fibrillation/flutter? When is treatment not necessarily needed?
- calcium channel blockers (Diltiazem)
- Digoxin + Diltiazem - better control of ventricular response rate, but more side effects
- beta-blockers (Atenolol, Sotalol) - use cautiously if systolic dysfunction is present
- Amiodarone - rate control, conversion of a lone AF to a sinus rhythm
- electrical cardioversion
- anticoagulants - prone to thromboemboli due to turbulent flow
normal HR and no structural disease —> optimal control is <150 bpm in hospital and 70-120 bpm at home
What is the goal of treating SVT? What are 5 options?
help AV node to slow the rate
- Amiodarone (potassiun channel blocker) - conversion in early disease
- Beta-blockers
- Calcium channel blockers (Diltiazem)
- Digoxin (Vagomimetic)
- Electrocardioversion under anesthesia
Atrial tachycardias:
What is atrial bradyarrhytmia? What are the most common primary and secondary causes?
atrial standstill resulting from failure of the atria to depolarize despite normal sinus node discharge (dogs > cats) = no P waves + regular junctional escape rhythm ~40 bpm
- primary atrial myopathy - muscular dystrophy in English Springer Spaniels
- secondary myopathy - sinoventricular rhythm from hyperkalemia
What are some causes of hyperkalemia? How does this affect the ECG?
- urinary obstruction
- iatrogenic (fluids, supplements)
- Addisonian crisis
- reperfusion injury
SINOVENTRICULAR RHYTHM - relatively normal QRS complexes lacking P waves —> 40 bpm —> treating hyperkalemia may bring back P waves
What are 5 signs of sinoventricular rhythm on ECGs?
- bradycardia
- tall T waves (spiked)
- small P waves (typically disappear)
- prolonged QRS complexes with reduced R waves (seems sinusoidal)
- eventual cardiac arrest if hyperkalemia is not reversed
Sinoventricular rhythm, hyperkalemia:
Hyperkalemia:
sinoventricular rhythm
- higher K = wider, more bizarre QRS complex
What treatments are indicated with sinoventricular rhythm?
decrease K
- unblock cat
- treat Addisons
- calcium gluconate - cardioprotective
- fluids with insulin - move K into cells
- Lasix - K excretion
