ECG and arrhythmia Flashcards
What are the 3 vectors for ventricular depolarization?
Q Septum
R Apex
S Base
Atrial flutter treatment?
DC synchronized cardioversion
Subendocardial ischaemia: why does repolarization occur in subendocardial cells before non ischaemic tissue?
shorter action potential duration
Define target vessel revascularization
repeat intervention of the same segment
What stimulates the septum?
L bundle branch
Differentiate coarse and fine VF
Coarse = recent onset & readily corrected by defibrillation
Fine = longer period of time since onset
What makes up an unstable plaque?
Fibrous cap and necrotic core
WBCs
Macrophages
Foam cells
What is CO for ventricular fibrillation?
CO = 0
What are 2 categories of tachyarrhythmias?
Supraventricular tachyarrhythmia
Ventricular tachyarrhythmia
What happens with atrial thrombus formation?
LA: PE
RA: Stroke
Why is CO reduced in VT
impaired ventricular relaxation and loss of AV synchrony (electrical coordination) leads to reduced CO
Outline ventricular extrasystole?
Ventricularly triggered extra beat
What is the normal PR interval?
0.12 - 0.2 sec
What is a significant difference between DES and BMS stents?
rate of target vessel revascularization
(BMS»_space; DES)
no difference in rate of death or MI
What are 2 supraventricular tacchyarrhythmias?
Atrial fibrillation
Atrial Tachycardia
What is the normal QRS width?
0.08 - 0.12 sec
Arrhytmia
Basic terms…
Narrow QRS (<0.08) =
Wide QRS = (> 0.12)
Narrow = supraventricular arrhythmia
Wide = ventricular arrhythmia
What is the commonest cause of palpitations in people with structurally normal hearts?
AV nodal reentry tachycardia
What causes involution of the collateral arterioles of the heart?
Decreased pressure gradient between coronary collaterals
e.g. due to percutaneous coronary intervention
Depolarization travels from and to where in myocardium?
inner to outer
List 3 defects causing variant / vasospastic angina?
1 calcium in vascular smooth muscle
2 hyperactive sympathetic nervous system
3 disturbances in production or release of NO
Symptoms and signs of arrhythmias?
SOB
Chest pain (radiating)
Decreased level of consciousness
Low BP
Palpitations
Slow/fast HR
Pre syncope / syncope
Pulmonary oedema
Heart congestion failure
Acute MI
Shock
What is the atrial and ventricular rate approximately in atrial flutter? Why?
Atrial = 250-350 bpm
Ventricular 150bpm
AV node protects ventricles by blocking most of the atrial impulses
Describe ECG of NSTEMI
NSTEMI - sub endocardial infarct (non transmural)
Depolarization travels to electrode (subendocardial infarct to non ischaemic tissue)
Results in baseline elevation and relative ST depression
What is the ECG characteristic of a sinus pause?
P and QRS wave
Long pause
P and GRS wave
What is the difference between atrial fibrillation and atrial flutter?
Fibrillation
- 400bpm
- grossly irregular
- irregular / almost flat baseline = irregularly irregular
Mechanism: reentry via macro re-entrant circuit
Flutter
- 250-400bpm (> ventricles)
- regular
- saw tooth appearance
Mechanism: typically multiple wavelet reentry
What makes up a stable plaque?
Rich in: ECM (collagen)
and smooth muscle
Thick fibrous cap
3 steps in the development of the collateral circulation of the heart
1 preexisting collateral arterioles
2 sheer stress (increased blood flow) and angiogenic growth factors from damaged myocardial tissue
3 remodelling of collateral arterioles
List the 4 different kinds of angina and outline.
Stable - pain when heart’s oxygen demands increase.
Unstable - can occur at rest with sudden onset of pain.
Variant/vasospastic angina - vasospasm interrupts oxygen supply and causes pain.
Silent myocardial ischaemia - no pain
What is an ECG characteristic of channelopathies?
Long QT interval
What are 2 categories of bradyarrhythmias?
Sinus block
AV conduction block
Briefly define
channelopathies?
A group of diseases (genetic, autoimmune or inflammatory) that alter cardiomyocyte ion channel function
What is a treatment option for ongoing atrial fibrillation, not responsive to beta blockers?
AV nodal ablation
+ pacing system
What ions do the AV nodal cells and Purkinje cells rely on respectively? What does this mean?
AV: calcium = slow
Purkinje: sodium = fast
What are 2 possible reasons for why there is no pain in silent myocardial ischaemia?
1 defects in pain threshold or transmission
2 autonomic neuropathy causing sensory loss
ECG characteristics of atrial fibrillation
Baseline is wavy with no P waves
Ventricular rhythm is irregular
QRS interval normal
Questions for ECG arrhythmia analysis
1) normal looking QRS complex?
2) is there a P wave associated with a narrow QRS?
3) what is the relationship between the P waves and QRS complexes?
Outline 3 steps in the remodelling process of collateral arterioles of the heart
1 Endothelial adhesion molecules bind monocytes
2 Monocytes differentiate to macrophages which secrete growth factors and cytokines
3 Attract further monocytes and proliferation of smooth muscle
What are drug eluting stents and bare metal stents?
DES - mesh tube that releases slow releasing anti proliferative drugs
BMS - mesh tube that keeps artery open
AF treatment
DC synchronized cardioversion
What are the 2 cardiac arrest rhythms?
Asystole
Ventricular fibrillation
What 2 arrhythmias require anticoagulation?
Atrial fibrillation and atrial flutter
Why does repolarization start in the epicardium?
The action potential of epicardial cells is shorter than that of endocardial cells. Therefore, repolarization occurs earlier
What is a possible outcome if a PVC falls on a T wave?
VT or VF
What is the first part of the heart to depolarize?
septum
List causes of artherosclerosis
Hypertension
Diabetes
High glucose levels
Turbulent blood flow (due to obstruction)
Smoking - nicotine
Infection
Elevated circulating lipid levels
What does the P waves and QRS complexes look like on ECG of VT?
P waves absent
QRS complexes wide and often bizarre with notching
If every QRS complex is not preceded by P wave in <0.20?
Heart block
Normal Sinus Rhythm
Rhythm is regular
60-100 bpm
P waves uniform and followed by QRS wave, 1:1
PR is 0.12-0.2
QRS complex is 0.08-0.12
Define premature ventricular contraction (PVC)
single irratable focus within the ventricle fires prematurely bypassing His-Purkinje conduction system giving rise to ectopic beat
If patient in AF > 48 hours?
Antigcoagulation for 4 weeks before attempted cardioversion (due to risk of intra atrial thrombus formation > 48 hours)
Outline 7 steps artherosclerotic plaque formation
1 Endothelial injury
2 Penetration of lipoproteins and subsequent LDL oxidation
3 Attracts monocytes and WBC adhesion
4 Macrophages consume Ox-LDL forming foam cells (cholesterol crystals) and cell debris into growing necrotic core
5 Triggers migration of smooth muscle cells from media to intima = collagen deposits and plaque formation
7 Fibrin infiltration generates fibrous cap
Define ventricular tachycardia?
a regular rhythm that occurs paroxysmally and is >120 bpm.
AV dissociation - ventricular rhythm proceeds independently of normal atrial rhythm
Differential diagnosis of regular broad complex tachycardia?
VT until proven otherwise
What are the shockable rhythms?
VF
Fast VT
Subendocardial ischaemia: what causes an inverted T wave?
If repolarization occurs in subendocardial cells before supeipethial cells
Name the condition when…
1- Every other beat is PVC
2- Every third beat is PVC
3- Every fourth beat is PVC
1- ventricular bigeminy
2 - ventricular trigeminy
3 - ventricular quadrigeminy
Why are the depolarization vectors stronger in LV vs RV?
LV is much thicker than RV
Describe ECG of STEMI
STEMI - trans-mural infarct
Downward shift of baseline due to ischaemic tissue depolarizing faster than non-ischaemic tissue.
Therefore, depolarization travels away from ischaemic tissue and results in baseline depression.
Relative to baseline, ST segment is elevated
What procedure can be performed to rule out intra atrial thrombus?
Trans-oesophageal echocardiogram
