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Bradyarrhythmia’s, Pacemaker’s & Complex Devices. Dr Chris McAloon Medical Student Teaching. Overview. Interpreting Bradyarrhythmia’s Different types of Bradyarrhythmia’s Pacemakers Complex Devices. First Rule. “ Always look at the patient”. Conducting system. Heart Blocks. NSR
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Bradyarrhythmia’s, Pacemaker’s & Complex Devices Dr Chris McAloon Medical Student Teaching
Overview • Interpreting Bradyarrhythmia’s • Different types of Bradyarrhythmia’s • Pacemakers • Complex Devices
First Rule “ Always look at the patient”
Heart Blocks • NSR • Sinus brady • SSS • Sinoatrial block • Sinus arrest
Heart Blocks • 1st degree • 2nd degree • Mobitz Type 1 • Mobitz Type 2 • 2:1, 3:1 AVB • 3rd degree • Fascicular block - LAD, RAD, TFB • LBBB, RBBB • AF, Flutter
Reversible Causes of Slow Heart Rate • Drug therapy • Acute Myocardial Infarction • Hypothermia • Hypothyroidism • Athletic Heart • Vaso-vagal mechanisms
Complete AV Block • All patients with persistent or intermittent complete AV block should be paced unless there is a reversible cause Irrespective of symptoms • Reversible causes include recent inferior MI, • hypothyroidism and drugs • This includes patients with congenital CHB • If you are not going to pace, you really need to be able to justify that decision
Sinus Node Dysfunction • Inappropriate bradycardia Intermittent – faintness / syncope Persistent – SOB / muscle fatigue / exhaustion • Associated atrial tachyarrhythmias / AV Block Intermittent – palpitations / faintness / syncope Persistent – SOB / muscle fatigue / exhaustion • Associated clinical syndromes Embolic Heart Failure
The ‘ALS’ Approach • Is there electrical activity? • What is the ventricular (QRS) rate? • Is the QRS rhythm regular or irregular? • Is the QRS complex width normal or prolonged? • Is there atrial activity present? • Is the atrial activity related to ventricular activity, if so how?
The Heart Block System • Are the P waves associated with the QRS complex at all? No = This is 3rd Degree Heart Block Yes= Move to Question 2
The Heart Block System • Is there one P wave to one QRS, with a prolonged PR interval that is not progressing (in length)? Yes= This is 1st Degree Heart block No = Go to question 3
The Heart Block System 3. Is there progression in PR interval duration until there is a non-conducted P wave? Yes= This is Wenckebach No = Go to question 4
The Heart Block System • Therefore it must be Mobitz type 2 • Mobitz type 2 difficult to explain • P waves conducted normal PR interval • There are P waves that are not conducted • Not always a specific block • 2:1 • 3:1 • 4:3
SA Slow Sinus Rate AV Block Atrial Tachy-arrhythmias
Paced Patients: Predominant ECG Indication BPEG / HRUK National Database 2003 - 4
Paced Patients: Predominant Presenting Symptom BPEG / HRUK National Database 2003-4
Pacing Indications • AV Block • Complete Heart Block • Second degree AV block (High block or symptoms) • Reversible: Inferior MI, Hypothyroidism • Sinus Node Disease • Chronotropic Incompetence • If resting HR in day time <30 • Atrial Fibrillation • Bradycardia • Bradycardia in presence drugs for uncontrolled Tachycardia
International Codes Pacemaker First Letter = Chamber(s) being PACED (A,V,D) Second Letter = Chamber(s) being SENSED Third Letter= How the device RESPONDS to SENSED Event (Inhibits, Triggers, Dual (I+T)) Fourth Letter = Added feature e.g R = Rate Response
Electrodes -- Fixation Mechanism • Passive Fixation Mechanism – Endocardial • Tined • Finned • Canted/curved
Electrodes – Fixation Mechanism • Active Fixation Mechanism – Endocardial • Fixed screw • Extendible/retractable
Pacemaker Prescription • Re-establish stable heart rate • Restore AV synchrony • Achieve chronotropic competence • Achieve normal physiological activation and timing • A lead if normal A function • V lead if actual / threatened AV HB • Rate modulation if slow
A 1% A Lead only 55% A + V Leads (Dual Chamber) 44% V Lead only (mostly in AF) V lead normally @ RV apex V
Heart Failure and CRT Heart failure common and disabling condition • Cardiac resynchronization therapy (CRT) • Applicable to ~1/3 of all symptomatic HF patients • Improvement in long term survival • NICE indications • NYHA III/IV, Optimal medical therapy • LVEF <35% • QRS > 120ms • However, 20-30% non responders to CRT