(!) Supraventricular tachycardia

Question 1

Define Supraventricular tachycardia

Answer 1

group of heart electrical abnormalities-defines as having normal sinus tachycardia with abnormal (often absent) p waves

AVRT-wolff parkinson white-via bundle of his

this focus on AV NODAL re-entry tachycardia (AVNRT

Question 2

Aetiology and risk factors of Supraventricular tachycardia

Answer 2

In AV node, 2 pathways-fast and slow that connect.Normally goes via fast, and fast stops slow. Fast repolarises slow, so can have premature signal-goes down slow pathway, and arrives at end as fast repolarises-> goes in circle-> activating ventricle everytime and escaping control

most common are focal atrial tachy-p waves present
Or AVNRT-no p waves

risk factors:
substance missuse (alcohol, cocaine)
Digoxin toxicity
Caffeine

Question 3

Epidiemology of Supraventricular tachycardia

Answer 3

Focal atrial tachy is relatively uncommon, but represent 10% of Supraventricular tachy

Question 4

Signs and Sx of Supraventricular tachycardia

Answer 4

Mainly based on ECG

Identify prior Hx of cardiac problems
or substance missuse

Sx-SOB, palpitations, dizziness/syncope, fatigue, nausea

ECG-AVNRT-sinus tachycardia, regular, but with no visible p waves
Focal atrial tachy-p waves visible, rate under 250bpm
Short duration with abrupt stop and start
P wave morphology weird-esp in v1 or aVL

response to vagal manoeuvres and adenosine are big diagnostic clues

Question 5

Investigations of Supraventricular tachycardia

Answer 5

ECG-AVNRT-sinus tachycardia, regular, but with no visible p waves. or p waves immediately before/after qrs. 140-280bpm
Focal atrial tachy-p waves visible, rate under 250bpm
Short duration with abrupt stop and start
P wave morphology weird-esp in v1 or aVL

rates should vary with pain, respirations and changes in ANS tone

response to vagal manoeuvres and adenosine are big diagnostic clues-
AVNRT will abruptly stop with vagal manoeuvres (only one to respond like that)

digoxin levels-can be high
Hypokalaemia can be cause

Question 6

Management of Supraventricular tachycardia

Answer 6

Differentiating between AVNRT and Sinus tachy (or A flutter)-AVNRT should stop abruptly after vagal manoeuvres (1st line) or use of adenosine (warn patient they’ll feel awful)

focal atrial tacky-respond to removal of causing agent (cocaine, alcohol, etc) but resistant to shock or drugs

Question 7

Complications of Supraventricular tachycardia

Answer 7

Congestive heart failure can be a consquence

resistance to therapy in longer term

cardiomyopathy

tachycardia induced ischemia/MI

Question 8

Prognosis of Supraventricular tachycardia

Answer 8

AVNRT-if not caused by structural defect-good-often stopped by vagal manoeuvres or adenosine

Focal AT-eventually always controlled but can take some time and combination of drugs