Heart Rhythm disorders Flashcards
Arrhythmia Presentation
• Tachyarrhythmias
– Palpitation, skipped beat
• Bradyarrhythmias
─ Fainting
─ Sincope
─ Dizzy spells
• Other symptoms – Dizziness – Chest Pain – Dyspnea – Sudden cardiac death
Arrhythmia Etiology
• Physiological • Pathological ─ Structural heart disease Ischemic heart disease Hypertensive heart diseases Valvular heart disease Cardiomyopathies Miocarditis, Pericarditis Congenital heart disease RV dysplasia
─ Drug related
─ Pulmonary diseases
─ Others
Mechanism of Arrhythmogensis
- Disorder of impulse generation
a) Automaticity (Automatism crescut)
b) Triggered Activity (Activitate declansata)
1) Early after depolarization
2) Delayed after depolarization - Disorder of impulse conduction
a) Block – Reentry.
b) Reflection. - Combined disorder
Mechanism of Arrhythmogenesis
History taking
(1) documentation of initial onset of symptoms
(2) complete characterization of symptoms
(3) identifying conditions that initiate symptoms
(4) duration of episodes
(5) frequency of episodes
(6) pattern of symptoms over time→ better or worse
(7) effect of any treatment
(8) family history of a similar problem
►Asses Pt. past medical history
Arrhythmias
Physical Examination
─check for orthostatic hypotension
─ findings related to atherosclerosis & CAD
presence of a carotid bruit
decreased peripheral pulses
─ findings related to a cardiac cause→presence of
specific cardiac murmurs or
S3 or S4 gallop
─ patient’s sex and age
PSVT that occurs in a 7-year-old boy →AVRT
PSVT presenting in a 65-year-old woman →AVNRT
Arrhythmias
Clinical Presentations
a wide spectrum of clinical presentations
→ from asymptomatic ECG abnormalities
→ to cardiac arrest
Related to arrhythmia
Related to primary condition (the underlying
disease)
Arrhythmias
Diagnosis
- ECG
- 24h Holter Ecg monitor
- Head-Up Tilt Table Testing
- Electrophysiology study
Arrhythmias
Ecg
Normal Sinus Rhythm
P wave
positive in lead II
negative in lead aVR
heart rate (50) 60-100 bpm
Constant PP (constant RR)
Constant PR (normal range)
Ecg
Major Tachyarrhythmias
Narrow QRS complex • Sinus tachycardia • Paroxysmal supraventricular tachycardia (PSVTs) • Atrial flutter • Atrial fibrillation
Wide QRS complex • Ventricular tachycardia • Aberrant ventricular conduction • Bundle branch block • Atrioventricular bypass tract
Supraventricular Arrhythmias
Sinus Tachycardia
simply Sinus Rhythm + heart rate ≥ 100 bpm
- P waves have normal morphology, positive in lead II
- Atrial rate 100-200 beats/min (adults)
- One P wave precedes every QRS complex
- Fast rates: P merged with the preceding T wave
- Ventricular rate 100-200 beats/min
- Regular ventricular rhythm
- Symptoms: palpitation, anxiety
Respiratory / Sinus Arrhythmia
Normally
HR increases slightly with inspiration
HR decreases slightly with expiration
Atrial and Nodal (AV Junctional) Premature
Beats
APBs features
- premature atrial depolarization (occur before the next normal P wave
- ectopic atrial pacemaker
- ventricles depolarized in a normal way
P wave APB is before QRS APB
- slightly different shape and/or
- different PR interval (longer or shorter)
- may be “buried” in the T wave of the preceding beat
QRS APB usually identical or very similar to the QRS SR
slight pause After the APB before the normal sinus beat
Symptoms: palpitation, extra beat-skipped beat
Atrial bigeminy
each sinus beat is followed by an APB
Atrial tachycardia (AT)
3 or more consecutive APBs ectopic pacemaker (nonsinus) fires off "automatically" in a rapid way atrial rate ~ 200 beats/min (range: 100 to 250 beats/min) Abnormal P wave morphology Ventricular rhythm usually regular Symptoms: palpitation, light-headedness or even syncope
Paroxysmal Supraventricular Tachycardia
A sudden run of 3 or more beats - Notsustained (< 30 sec) (i.e., lasting from 3 beat up to 30 sec) - Sustained episodes > 30 sec.- may last minutes, hours, or longer
AV NODAL REENTRANT TACHYCARDIA
AVNRT
Rapid and Regular rhythm
Rates between 140 - 250 beats/min
generally initiated by an APB
may occur with normal hearts or with underlying heart disease reentry = a situations in which a cardiac impulse appears to “chase its own tail”
therapy = ↑ vagal tone ( Valsalva maneuver, carotid sinus massage)
(• slow and fast conduction routes
• final common pathway through the
lower part of the AV node and
bundle of His )
A premature atrial impulse finds the
fast pathway refractory,
allowing conduction only down the slow pathway (left). By the time the impulse reaches the His bundle, the fast pathway may have recovered, allowing retrograde conduction back up to the atria—the resultant “circus movement” gives rise to slow-fast atrioventricular nodal re-entrant tachycardia (right)
AV Junctional Rhythms
- Retrograde P waves (+ in lead aVR , - in lead II) Pattern 1. precede the QRS complex 2. immediately after the QRS 3. Absent P waves (buried in the QRS) - ventricles normally depolarized → narrow QRS complex - Mechanism: ectopic pacemaker - if AV junction=cardiac pacemaker → atria stimulated in a retrograde fashion, from bottom to top
Atrial Flutter
F “sawtooth” flutter waves instead of discrete P waves
Atrial Rate is about 300 beats/min (250 - 350 bpm)
*** IF atrial rate < 250 beats/min (eg 200 - 220 beats/min)
→ patient taking drugs that slow atrial conduction
Ventricular Rate:
Constant: 150, 100, or 75 beats/min (150 bpm → 2:1 flutter) variable
Eg
4:1 flutter →1 QRS complex with every 3 flutter wave,
2:1 flutter →1QRS with everyTwo flutter waves,
1:1 flutter → ventricles contract about 300 times a minute → rare
Atrial Fibrillation
most commonly seen arrhythmias
• fibrillatory or f waves
• irregular waves replace the normal P waves
• atria depolarized at a very rapid rate 400 - 600 min
• ventricular rate
- irregular
- normal AV junction → 110 - 180/min
Ventricular Premature Beats
premature depolarizations
arising in the ventricles (right or left ventricle)
QRS complexes → wide
( the stimulus spreads through the ventricles in an aberrant direction)
Ventricular Premature Beats
Characteristics:
premature occur before the next normal beat is expected aberrant in appearance wide QRS (> 120 ms) T wave usually point in opposite directions from QRS
Ventricular Premature Beats
Compensatory Pause
followed by a pause before the next normal beat
usually but not always > pause after an APB
fully compensatory pause:
Interval
[QRS before - QRS after VPB] = 2x basic RR interval
VPBs Clasification:
- Uniform
- Multiform
Uniform VPBs
arise from the same anatomic site (focus)
are uni focal
may occur in normal or pathological hearts
!! VPB
Two in a row are referred to as a pair or couplet
3 or more in a row are, by definition, VT
Ventricular Tachycardia
Definition
a run of 3 or more consecutive VPBs
Ventricular Tachycardia
Classification
Duration
Nonsustained (lasting 3 beats to 30 seconds)
Sustained (lasting 30 seconds or more)
Morphology
Monomorphic
Polymorphic
With long QT(U) syndrome: torsade de pointes
Without long QT(U) syndr.: polymorphic VT with acute ischemia
Ventricular tachycardia Sustained VT (lasting > 30 seconds)
→ potential life-threatening arrhythmia
hypotension
may degenerate into VF causing
cardiac arrest
Ventricular Tachycardia
Therapy
Pharmacologic /
implantable cardioverter defibrillator (ICD)
Accelerated Idioventricular Rhythm
heart rate : 50 - 100 beats/min without associated P waves wide QRS complexes Short duration lasting minutes or less no specific therapy required common with acute MI sign of reperfusion after the use of thrombolytic agents
Torsade de Pointes
Form of Polymorphic Ventricular Tachycardia
direction of the QRS complexes appears to rotate cyclically, pointing downward for several beats and then twisting and pointing upward in the same lead.
Favored by long QT intervals
Ventricular Fibrillation
fibrillatory waves → coarse or fine
irregular pattern
Most common cause of sudden cardiac death
Ventricles
Do not beat in any coordinated fashion
Fibrillate or vibrate asynchronously and ineffectively
No cardiac output occurs
Patient becomes unconscious immediately
Ventricular Fibrillation
There are 3 major ECG patterns in with cardiac arrest
- Brady-asystolic patterns
- Electromechanical dissociation
- Ventricular Fibrillation
Bradyarrhythmias
Sinus Bradycardia
sinus rhythm + heart rate < 60 beats/min
Many patients tolerate heart rates of 40 beats/min
surprisingly well, but at lower rates symptoms are likely
1. Dizziness
2. Near syncope
3. Syncope
4. Ischemic chest pain
5. Stokes-Adams attacks
6. Hypoxic seizures
- Some authors define sinus bradycardia as a heart rate of less than 50 bpm
Atrioventricular Heart Block
Heart block
= general term for atrioventricular (AV) conduction disturbances
occurs when transmission through the AV junction is impaired transiently or permanently
Classification of AV Heart Blocks
First-degree block =Uniformly prolonged PR interval
Second-degree block = Intermittent conduction failure
Mobitz type I = progressive PR prolongation
Mobitz type II: sudden conduction failure
Third-degree block =No atrioventricular conduction
First-Degree Heart Block (Prolonged PR
Interval)
prolonged PR interval
constant from beat to beat PR >200 msec
Second-Degree AV Block
Classification
Mobitz type I block (also called Wenckebach block)
Mobitz type II block.
Mobitz type I (Wenckebach AV block)
progressive lengthening of the PR interval from beat to beat until a beat is “dropped.”
The dropped beat is a P wave that is not followed by a QRS complex
failure of the AV junction to conduct the stimulus from A to V
MOBITZ Type II AV block
sudden appearance of a nonconducted sinus P wave
severe conduction system disease involving regions below the AV node (i.e., His-Purkinje system)
progressive → complete heart block
indication for a pacemaker may be seen with anterior wall MI
Advanced second-degree AV block
two or more consecutive nonconducted P waves
example with sinus rhythm and 3:1 block, every 3rd P wave is conducted with 4:1 block, every 4th P wave is conducted
Third-Degree (Complete) Heart Block
atria and ventricles are paced independently
no stimuli are transmitted from the atria to the ventricles
atria → paced by the or sinoatrial (SA)
ventricles → paced by an escape pacemaker below the AV junction
atrial rate > ventricular rate
resting ventricular rate
lower than 30 beats/min or
as high as 50 to 60 beats/min
Third-Degree (Complete) Heart Block
Classification
with narrow QRS generally stable
with wide QRS less stable
Sinus breaks, sinus arrest, and escape beats
The sinus impulse does not depolarize the atria
for one or more beats
An absent beat (without P wave or complex
Sinus break in a patient with sinus node disease
Atrioventricular Blocks
Signs and symptoms
1 th-degree AV block
- Generally not associated with any symptoms
* zan incidental finding on Ecg usually
Atrioventricular Blocks
Signs and symptoms
2 th-degree AV block
- Asymptomatic usually
- some: sensed irregularities of the heartbeat, presyncope, or syncope
- physical examination may manifest as bradycardia (Mobitz II) and/or irregularity of heart rate (especially Mobitz I )
Atrioventricular Blocks
Signs and symptoms
3 th-degree AV block
• associated with profound bradycardia unless the site of the block is located in the proximal
• Frequently associated with symptoms:
→ fatigue, dizziness, light-headedness, presyncope, and syncope;
The Stokes-Adams Syndrome
Definition
= an abrupt, transient loss of consciousness due to sudden but pronounced decrease in the cardiac output, which is caused by a sudden change in the heart rate or rhythm
* This definition does not include vasovagal syncope or epilepsy although patients with Stokes-Adams syncope may have seizures during periods of cerebral ischemia.
The Stokes-Adams Syndrome
Clinical Features
depend upon the duration and type of underlying arrhythmia
depend upon the status of the cerebral circulation
Symptoms
vary from slight faintness →loss of consciousness
with or’without convulsions.
The Stokes-Adams Syndrome
Attack Description
- Initial pallor
- A facial flush after the resumption of the normal circulation
- The abscence of an aura tend to separate seizures during Stokes Adams syncope from seizures of primary cerebral origin
- Stokes-Adams seizures usually commence and terminate abruptly
- The patient may resume a previous conversation or
activity without being aware of the pause produced by the period of arrythmia-induced cerebral ischemia - Physical exam.: A slow or a very rapid pulse during the period of unconsciousness
- Ecg during a syncopal episode demonstrates the responsible rythm
Rhythm disturbances Symptoms
Summary
Broad range • palpitation • skipped beat • awareness of heart palpitations • fluttering sensation in the chest or neck
Long lasting arrhythmias • Fatigue • Chest pain • Dizziness • Shortness of breath • Lightheadedness • Fainting (syncope) or near-fainting spells • Adam Stokes syndrome -> AV block -> Ventricular Fibrillation • extreme cases→ collapse and sudden cardiac arrest
Technical errors during Ecg Recording
- Errors in electrodes placement
- Inadequate filter application
- Artifacts due to device or to the pacient (cold
environement, Parkinson disease) - Misplacement of electrodes determine an incorrect
diagnosis (e.g.Q wave MI) - Inappropriate use of some filters may amplify ST
elevation in V1 to V2 or may suppress an otherwise
visible J wave” - Artifacts generally mimic arrhythmias: flutter or
ventricular tachycardia
