Heart blocks and pacemakers 2019

cardiology

1. Heart blocks and Pacemakers 2019 DR Ihab Suliman MBBS ECFMG MRCP(UK) ABcv MRCP spec (End and DM) CBNC FESC Abstract committee grader for ESC Conference 2019

2. First Degree AVB Conduction delay can occur in: Atrium: 3% of cases May be due to intratrial pathology EKG findings: widening of P wave and decreased P wave voltage AV node: Most common site Common causes: increased vagal tone, CCB, digoxin, BB EKG findings: long PR interval with a narrow or wide P wave and narrow QRS Bundle of His: Drugs that block sodium channels can impair depolarization and slow conduction (Quinidine, procainamide )

3. First Degree AVB Clinical significance – none Treatment – none May progress to 2 nd or 3 rd degree AVB

4. Second Degree AVB Some atrial impulses fail to reach the ventricles 2 types: Mobitz Type I (Wenckebach): progressive PR interval lengthening to a non-conducted P wave Mobitz Type II: PR interval constant prior to P wave that does not conduct to the ventricles.

5. SECOND DEGREE A-V BLOCK (MOBITZ I OR WENCKEBACH)

6. Mobitz Type I (Wenckebach) AVB Most often involves AV node Benign Features: Gradually increasing PR interval Gradually decreasing R-R interval Dropped beat Largest delay occurs in the first beat and then decreases beat to beat until block occurs and cycle is reset Group beating: 3:2,4:3 etc.

7. Second Degree Heart Block (2 º) Mobitz Type I (Wenkebach) PR PR PR DROPPED BEAT

8. Mobitz Type I Clinical implications: Often asymptomatic May have some symptoms eg lethargy, confusion If cardiac output is reduced, patient may experience angina, syncope or heart failure due to bradycardia and resultant hypoperfusion state. Can occur in athletes with high vagal tone Elderly: aging prolongs cycle length

9. Further implications: Underlying IHD: Mobitz type I can be complication of inferior MI as: RCA supplies inferior and posterior walls and AV and SA nodes Associated with increased mortality Treatment: Removing reversible causes (ischemia, increased vagal tone, medications Pacemaker if symptomatic during day No pacemaker is symptoms at night May progress to 3 rd degree AVB

10. MOBITZ TYPE II

11. Mobitz Type II AVB Always occurs below the AV node 20% within Bundle of His 80% in bundle branches Widened QRS PR interval may be normal or slightly prolonged but constant Non-conducted P wave on EKG Clinical implications: Dizziness Presyncope Syncope

12. Mobitz Type II AVB Type II is permanent and may progress to higher levels of block Treatment: Remove reversible causes Potential candidates for pacemaker insertion

13. Second Degree AVB 2:1 Unable to classify as Mobitz type I or II Ratio of 2 P waves to 1 QRS Clinical significance: Will be associated with symptoms (dizziness, lethargy etc.) May progress to 3 rd degree AVB Treatment - pacemaker

14. THIRD DEGREE A-V BLOCK

15. Third degree (complete) AVB No atrial impulses reach the ventricles due failure of AV node therefore no P wave conduction AV dissociation (Ps marching through…) QRS complex: Narrow: block at AV node to level of bundle of His Wide: block below level of bundle of His More distal the block the slower the escape rhythm If <40bpm: pacemaker is unreliable causing profound bradycardia or asystole Syncope is very common

16. Clinical Significance Clinical Implications: Dizziness Presyncope Syncope Ventricular tachycardia Ventricular fibrillation Confusion Can worsen angina and CHF Treatment: Pacemaker!

17. Class I Indications for Permanent Pacing in Adults per AHA/ACC 3 rd degree AVB at any anatomic level associated with any of the following: Symptomatic bradycardia (secondary to AVB) Symptomatic bradycardia (secondary to drugs required for management of dysrhythmias or other medical conditions) Documented asystole >3s or escape rate of <40 bpm in awake, asymptomatic patient After ablation of AV node Postoperative AVB that is not expected to resolve Neuromuscular disease with AVB (neuromuscular dystrophies)

18. 2. Symptomatic bradycardia from 2 nd degree AVB regardless of type or site of block. 3. Chronic bifascicular or trifascicular block with intermittent 3 rd degree AV block or type II 2 nd degree AVB. 4. After AMI with any of the following: Persistent 2 nd degree AVB at the His-Purkinje level with bilateral bundle branch block or 3 rd degree AVB at or below His-Purkinje system Transient 2 nd or 3 rd degree infranodal AVB and associated BBB Symptomatic, persistent 2 nd or 3 rd degree AVB 5. Sinus node dysfunction with symptomatic bradycardia or chronotropic incompetence. 6. Recurrent syncope caused by carotid sinus stimulation .

19. Pacemaker indications: Class IIa Complete AVB without symptoms: >40bpm while awake = Class IIa indication UNLESS: Activity or exercise is limited Heart begins to enlarge LV function is depressed LA enlargement is noted Intra- or infra-Hisian block issuspected with of without QRS widening QT interval prolongation Ventricular arrhythmias Episodic profound bradycardia (during sleep or awake)

20. Pacemaker indications: take home points! Complete AVB with: Associated symptoms Ventricular pauses >3s Resting HR <40 bpm while awake = pacemaker!

21. LBBB in NSR

22. RBBB

23. A Brief History of Pacemakers

24. Just kidding…but did you know? The implantable cardiac pacemaker was discovered by mistake! Wilson Greatbatch was building an oscillator to record heart sounds. When he accidentally installed a resistor with the wrong resistance into the unit, it began to give off a steady electrical pulse. Greatbatch realized that the small device could be used to regulate the human heart. After two years of refinements, he had hand-crafted the world's first successful implantable pacemaker (patent #3,057,356). Until that time, the apparatus used to regulate heartbeat was the size of a television set, and painful to use. Greatbatch later went one step further, inventing a corrosion-free lithium battery to power the pacemaker. All told, his pacemakers and batteries. Thus in 1985 the National Society of Professional Engineers named Greatbatch's invention one of the ten greatest engineering contributions to society of the last 50 years.

25. Pacemaker Functions Stimulate cardiac depolarization Sense intrinsic cardiac function Respond to increased metabolic demand by providing rate responsive pacing Provide diagnostic information stored by the pacemaker

26. Pulse generator: power source or battery Leads or wires Cathode (negative electrode) Anode (positive electrode) Apex of right ventricle IPG Lead Anode Cathode Pacemaker Components Combine with Body Tissue to Form a Complete Circuit