Term
| when should sinus node dysfunction be suspected |
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Definition
| SND should be suspected when a patient describes symptoms of fatigue, syncope, or presyncope or exercise intolerance and is noted to have sinus bradycardia or pauses on the 12 lead ECG or on holter. |
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Term
| sinus node dysfunction epidemiology |
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Definition
| Epidemiological studies have suggested SND for approximately 50% of the 300,000 new pacemakers in the US and 20-30% of the 900,000 new pacers in Europe. |
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Term
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Definition
• Blood supply is variable making it vulnerable to damage during operative procedures
• Sinus nodal artery (SNA), usually a branch of RCA in 55-60%, Left Circumflex in 40-45% |
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Term
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Definition
| Densely innervated with postganglionic adrenergic and cholinergic nerve terminals. (threefold greater density of B- adrenergic and muscarinic cholinergic receptors than adjacent atrial tissue) |
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Term
| medications that suppress automaticity and can cause SND |
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Definition
• β-blockers
• calcium channel blockers (diltiazem and verapamil)
• digoxin (especially in the presence of high vagal tone)
• class I and III antiarrhythmic medications (AMIODARONE, a big culprit)
• ivabradine (now available for heart failure, being used by EP for IST)
• sympatholytic drugs such as clonidine. |
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Term
| systemic illnesses or other extrinsic conditions that can cause SND |
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Definition
• hypothyroidism
• hypoxemia caused by sleep apnea
• increased intracranial pressure
• increased vagal tone that occurs, for example, during endotracheal suctioning, vomiting, and the Valsalva maneuver. |
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Term
| intrinsic cause of sinus node dysfunction |
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Definition
• Degenerativeprocessesinvolvingthesinusnode and the sinus node area.
-Usually acquired, Rarely be familial
• SNDispresentwheninappropriatesinus bradycardia, pauses in sinus rhythm (sinus arrest), sinus node block, or a combination of these exist.
• Thedegenerativeprocessandassociatedfibrosis may also involve the AV node and intraventricular conduction system.
-As many as 17% of patients with sick sinus syndrome have evidence of AV block and bundle branch block. |
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Term
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Definition
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Term
| what is tachy brady syndrome |
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Definition
• Special type of Sinus node dysfunction is Tachy-Brady Syndrome.
• It is reserved for when afib converts to sinus rhythm |
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Term
| SND pacemaker indications class I-III |
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Definition
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Term
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Definition
• Tadpole shaped
• 2x5mm
• Endocardial
• IA septum at the junction of atria and ventricles
• Blood supply
-RCA- 95%
-LCx-5% (left circumflex artery)
-Occasionally from both |
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Term
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Definition
• Activated by the the atrial depolarization
• Intrinsic rate 40-60bpm
• Delay of 0.15 seconds
-Time atrial take to expel blood
-Time for ventricular filling
-Protection to ventricles from atrial arrhythmias |
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Term
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Definition
• Directly continuous with the AV node
• 20 mm long
• Endocardial
• Within the IV septum
• Bundle of discreet fiber- crosses the AV ring
• No dedicated blood supply |
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Term
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Definition
-Only normal pathway Atria->Ventricles
-Intrinsic rate 30-50bpm
-Nervous stimulation – minor effect
-Depolarization cannot be seen on the ECG. |
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Term
| bundle branches anatomy and physiology |
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Definition
• HIS bundle separates into 2 main branches
-Left Bundle Branch
-Right Bundle Branch
• Left Bundle Branch
-Antero-Superior division known as Left Anterior Hemi-Branch
-Postero-Inferior division known as Left posterior Hemibranch
• No dedicated blood supply
• Intrinsic rate-40 bpm |
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Term
| purkinje fibers anatomy and physiology |
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Definition
• Bundle Branches divide further into small, dense network of conducting tissue
• Endocardiala->Epicardial
• No dedicated blood
supply
• Entire musculature depolarizes quickly
• Intrinsic rate-20 bpm
• Nervous stimulation has minor effect |
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Term
| depolarization vs repolarization ekg |
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Definition
depolarization- QRS, ventricles
repolarization- P, atria |
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Term
| what are AV Nodal Blocks (heart blocks) |
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Definition
• Disturbances of the conduction through the heart, occurring at the AV Node
• AV Node – damaged/diseased – delay or total block of impulses at the AV Node
• This conduction defect can be seen on the ECG |
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Term
| causes of AV nodal blocks |
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Definition
• Increased vagal tone
• Myocardial infarction
• Coronary spasm
• Highly trained athletes
• Digitalis intoxication
• Beta blockers
• Viral myocarditis
• Degeneration (age)
-Lev’s disease: calcification and sclerosis of fibrous cardiac cytoskeleton
-Lenegre’s-primary sclero-degenerative disease of conducting system. No involvement of fibrous skeleton of heart
• Sclerosis (Aortic)
• Cardiac surgery (trauma) |
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Term
| first degree heart block ekg findings |
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Definition
• SA Node – normal - Normal P wave
• AV Node conducts more slowly than normal
-Prolonged PR Interval, constant, PR Interval > 0.2 seconds (5 small sq)
• Rest of conduction is normal
-Normal QRS |
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Term
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Definition
| 1st degree heart block ekg |
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Term
| first degree heart block significance and treatment |
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Definition
• Clinical significance
-None
• Treatment
-None
• Note – this can progress to 2o or 3o heart block |
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Term
| types of second degree heart block |
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Definition
• Mobitz Type I (Wenkebach)
• Mobitz Type II
•2:1 |
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Term
| Second Degree Heart Block (2o) Mobitz Type I (Wenkebach) |
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Definition
• Conduction through the AV Node – progressively delayed until a drop beat is seen
• PR Interval prolongs with each beat until a dropped beat is seen
• The PR Interval is NOT constant
• After each dropped beat, the PR interval is normal and the cycle starts again |
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Term
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Definition
| second degree heart block mobitz type I |
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Term
| significant and treatment of second degree heart block mobitz type I (Wenkebach) |
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Definition
• Clinical Significance
-Slight symptoms e.g.. Lethargy, Confusion
• Treatment
-Pacemaker if during day &/or
symptoms
-No treatment if at night
• Note – this can progress to 3o Heart Block |
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Term
| Second Degree Heart Block (2o) Mobitz Type II |
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Definition
• Conduction through the AV node is constant.
• PR interval is normal and constant
• Occasionally a dropped beat is seen |
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Term
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Definition
| Second Degree Heart Block (2o) Mobitz Type II |
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Term
| significance, treatment of second degree heart block mobitz type II |
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Definition
• Clinical significance – this is more significant disease
• Treatment – pacemaker
• Note – this can progress to 3o Heart Block |
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Term
| Second Degree Heart Block (2o) 2:1 |
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Definition
• Unable to strictly classify as Mobitz Type I or II
• Particular type of second degree Heart Block
• Ratio2Pwaves:1QRS |
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Term
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Definition
| second degree heart block 2:1 |
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Term
| significance and treatment for second degree heart block 2:1 |
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Definition
• Clinical significance – unable to classify as Mobitz type I or II
-Will be associated with symptoms, dizziness, lethargy etc.
-normal QRS and long PR interval indicate AV nodal
-BBB inidates below AV node
• Treatment – pacemaker
• Note – this can deteriorate to 3o Heart Block |
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Term
| Third Degree Heart Block (3o) (Complete) |
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Definition
• Complete failure of the AV Node
• No impulses from Sinus Node will pass
through to the ventricles
• Some part if the conducting system will take over as pacemaker of the heart (even a myocardial cell 10-15 bpm) |
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Term
| Third Degree Heart Block (3o) (Complete) ekg findings |
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Definition
• P wave rate – normal
• Ventricular rate – slow
• Ventricular complex may be broad • Idioventricular rhythm
• Complete dissociation between P waves & QRS |
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Term
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Definition
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Term
| 3rd degree heart block significance and treatment |
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Definition
• clinical significance
-Symptoms LOC, Confusion, Dizziness, Low BP
-Can lead to standstill, VT or VF (stokes Adams)
• Treatment - pacemaker
medical treatment: atropine if block at av nodal level, isoproterenol iv infusion, caution in acute mi |
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Term
| congenital vs acquired complete heart block |
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Definition
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Term
| principles of pacing and types |
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Definition
-Transcutaneous
• Emergency use with external pacing/defib unit
-Transvenous
• Emergency use with external pacemaker
-Epicardial
• Wires sutured to right atrium & right ventricle
• Atrial wires exit on the right of the sternum
• Ventricular wires exit on the left of the sternum |
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Term
| pacemaker insertion sites |
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Definition
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Term
| complications of pacemakers |
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Definition
• Pericardial Effusion/Tamponade
• Pericarditis
• Infection
• Hematoma
• Pneumothorax
• Death |
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