W9: Arrhythmia

Question 1

Explain 1st, 2nd and 3rd degree heart block: signs, possible aetiology complications and management

Answer 1

1º => Prolonging PR >200ms (5 small squares)
normal P+QRS; delayed AV conduction; COMMON + asympt.

• Athletes, Thyroid Dysfunction
• Post-MI; Lyme; SLE; Congenital; Myocarditis
• BB, Rate-limiting CCB (Verapamil)

> AF risk, otherwise nil compl. d/t asympt.
Withdraw causative drug or Pacing

2º =>
Mobz. T1/WB: prolonging PR then 6th QRS failure; nocturnal; brady + syncope

• Athletes
• Inferior MI, myocarditis
• Surgery, Drugs

> Pacing or nil (asympt.)

Mobz. T2: fixed PR, 2nd/8th P rails, symptomatic during day - palpitations, syncope; more P waves than QRS 2:1

• BoH, or bundle branches pathology
• MI; fibrosis of conducting system;
• thyroid or drugs

> complete block so PACING + MONITOR
haemodynamic disturb.

3º => complete block; AV dissociation; escape rhythm QRS; SYMPTOMATIC

• post-pacing/ablation
• pathology, inflamm, fibrosis, MI, congenital
• BB, CCB, Digoxin,

> PACING + MONITORING

Question 2

Describe atrial fibrillation and flutter.

Answer 2

1. AF => loss of regularity in atrial depol.; nil P, fine QRS (rapid ventr. rate); embolism risk!
   * ECG event recorder
2. Atrial Flutter => RA circulating wave, previous cardiac surgery (scarring source - IVC, tricuspid annulus valve); SAWTOOTH P. 150bpm.

Question 3

AF Tx

Answer 3

=> Rate Control: BB/ CCB/ Digoxin

=> Chem Cardiovert: Rhythm Control: 
Class 1C (Na+) FLEICANIDE and 
Class 3 (K+) AMIORODONE

+ ANTICOAG: Warfarin, Apixiban, Rivaroxiban (CHADSVASC2)

Question 4

Atrial Flutter Tx

Answer 4

=> Ablation of flutter circuit

=> Cardioversion

=> Thromboemb. risk: BB, CCB

Question 5

Explain “supraventricular tachycardia”

Answer 5

SVTs are tachys arising from accessory conduction pathways aboveventricles. Benign.

AV NODAL RE-ENTRY: 180BPM, nil P, simultaneous atr. and ventr. depol.

AV RE-ENTRY TACHY: accessory pathway

Question 6

Describe Wolff-Parkinson-White Syndrome

Answer 6

AV RE-ENTRY TACHY: accessory pathway, w/ ↑rate

• Younger Pt.
• Retrograde conduction

ecg:
-PR interval < 120ms
- Delta wave: slurring slow rise of initial portion of the QRS
- QRS prolongation > 110ms
- Discordant ST-segment and T-wave changes (i.e. in the opposite direction to the major component of the QRS complex)

Question 7

SVt Tx

Answer 7

=> VAGAL MANOEUVRES

=> ADENOSINE: symp. dyspnoea, palpitations, dizziness
** ACUTE => adenosine or verapamil (IV) **

=> CATHETER ABLATION

Question 8

Describe ventricular tachycardia and fibrillation: signs, possible syndromes

Answer 8

V TACH. => 100bpm+; broad QRS

• LONG QT SYNDROME: prolongation of depol.; CONGENITAL; drugs

TORSADE DE POINTE => shortlived, multiple ventircular foci

=> BB, inserted cardiac defib (ICD), withdrawal of drug
=> (2) underlying cause: antiarrhythmic, revasc

V FIB. => tachy+++, loss of CO, AV-dissociation; decreasing amplitutde; cardiac arrest

=> SHOCKABLE!!

Question 9

Understand the difference between atrial and ventricular ectopic beats.

Answer 9

1. ATRIAL ECTOPICS: abn p wave + normal QRS

2. VENTRICULAR ECTOPICS: broad QRS

Question 10

Discuss the prevalence of atrial fibrillation in the population.

Answer 10

AF increasing d/t ageing population, better care and management of acute MIs and heart failures therefore degenerative consequences on myocardium give rise to disruption to conducting system (fibrosis and scarring for example, or consequences of invasive Tx)

Question 11

TYPE 1 ANTIARRHYTHMICS

Answer 11

Na+ (fast) antagonists => membrane stabilisation
↓conduction velocity ↓AP amplitude
A: quinidine
B: lidocaine
C: flecainide - AF, SVT: maintain repol.

FLECAINIDE

Question 12

TYPE 2 ANTIARRHYTHMICS

Answer 12

B-Adrenergic Antagonist => block B1 stim.; ↓SA + AV cond.; ↓phase 2 plateau therefore ↓Ca2+ entry

*suppress ventricular ectopics and tachy

ATENELOL, BISOPROLOL (1st line AF), PROPRANOLOL

Question 13

TYPE 3 ANTIARRHYTHMICS

Answer 13

K+ Channel Blocker => ↑phase 3 refractory period. slowing K+ exit

• life threatening VF and VT, res. AF, VT, sustained VT = cardioversion
• AMIORODONE: toxicity, slate SFX, corneal deposit, pulm fibrosis, +/-thyroid

AMIORODONE, SOTALOL

Question 14

TYPE 4 ANTIARRHYTHMICS

Answer 14

(L)Ca2+ Channel Blocker => ↓phase 2 plateau therefore ↓Ca2+ entry, ↓HR; ↓conduction

*Paroxysmal SVT; AF; Flutter

VERAPAMIL, DILTIAZEM

Question 15

TYPE 5 ANTIARRHYTHMICS

Answer 15

1. DIGOXIN => Blocks K-Na-ATPase => ↑Ca accum.; ↑vagal tone, ↓refractory

*RENAL IMPAIRMENT. MONITORING K
↓↓K+ = DIGITOXICITY: xanthopsia, brady. + tachy., VT + VF

2. ADENOSINE => ↓/BLOCKS AV CONDUCTION; cardioversion
   * significant SFX: impending doom, nausea, asystole, AVOID IN ASTHMA

Question 16

ACOAG: WARFARIN: mech.; D-D

Answer 16

Vitamin K+ antag. => Vit K cofactor for clotting cascade

narrow Tx index = INR (norm.: 1; Tx 2.5-4)
TERATOGENIC (avoid 1st and 3rd trimester)

D-D: aspirin: ↓albumin binding = ↑warfarin activity
abx: inhibit degradation= ↑warfarin

Question 17

ACOAG: THROMBIN INHIBITOR

Answer 17

DABIGATRAN: ↓stroke risk but caution w/ renal impairment = bleeds risk

Question 18

ACOAG: Xa INHIBITOR

Answer 18

(1) EDOXABAN, RIVAROXABAN, APIXABAN: recent stroke, lesser risk to Pt.