Arrhythmias Flashcards
What are arrhythmias?
Any disturbances of the normal heart rhythm. - too fast, slow, or irregular.
What symptoms can arrhythmias cause?
Blackout, palpitations, death.
What is the resting membrane potential of a cardiomyocyte?
-80mV
What is the resting potential of a myocyte in the SAN?
-55mV
QRS complex is caused by
Ventricular depolarisation
P wave is caused by
Atrial depolarisation
T wave is caused by
Ventricular repolarisation
What does a long QT interval predispose someone to?
Long QT syndrome (LQTS) is a condition in which repolarization of the heart after a heartbeat is affected. It results in an increased risk of an irregular heartbeat which can result in fainting, drowning, seizures, or sudden death.
QRS duration should be less than 3 small squares.
QRS duration should be less than 3 small squares.
Structured approach to interpreting ECG’s.
- Is there organised electrical activity? 2. What is the ventricular rate? 3. Are the QRS complexes regular or irregular? 4. Are the QRS complexes broad or narrow? 5. Is atrial activity present? 6. Is atrial activity related to ventricular activity?
Ventricular fibrilation
Ventricular fibrillation is a heart rhythm problem that occurs when the heart beats with rapid, erratic electrical impulses. This causes pumping chambers in your heart (the ventricles) to quiver uselessly, instead of pumping blood.
Palpitation
Abnormally feeling your own heart beat. - sudden onset / offset.
Syncope
Blackouts - faints, falls, seizures.
What symptoms can arrhythmias cause?
Palpitations Syncope Chest tightness - exacerbation of angina. Breathlessness - chronotropic incompetence. Sudden death
How can you investigate ECG’s?
12 lead ECG Ambulatory ECG 3 year implantable loop recorder Smartphone monitor Exercise tolerance test
What effect do calcium channel antagonists have on heart rate?
Decrease heart rate.
What are examples of beta blockers?
Bisoprolol, atenolol, metoprolol
What are the effects of beta blockers?
Block effects of catecholamines Slower conduction through AV node Some effect at preventing arrhythmias Generally safe, caution in asthma or severe peripheral vascular disease.
Explain what happens in this image:
- Ca2+ moves into the cell through L Tide calcium channels.
- Ryanodine receptors respond to Ca2+ releasing large amount of Ca2+ into the cytoplasm.
- SERCA pump transports Ca2+ from the cytoplasm back into the sarcoplasmic reticulum.
- Sodium / Calcium exchange also pumps calcium out of the cell.
What do Ryanodine receptors do?
Ryanodine receptors (RyRs) are located in the sarcoplasmic/endoplasmic reticulum membrane and are responsible for the release of Ca2+ from intracellular stores during excitation-contraction coupling in both cardiac and skeletal muscle.
Ryanodine receptors are responsive to Ca2+ so a small influx of Ca2+ activates the RyRs causing a large Ca2+. Ca2+ induced Ca2+ release.
What does the SERCA pump do?
The sarcoendoplasmic reticulum (SR) calcium transport ATPase (SERCA) is a pump that transports calcium ions from the cytoplasm into the SR.
Diagnosis and response:
Asystole
No ventricular activity - urgent cardiopulmonary resuscitation.
What is shown in this ECG?
- what is the response?
Ventricular fibrilation - chaotic ventricular activity.
- emergency cardiopulmonary resuscitation
- ventricles quiver
- electrical defibrilation
What can cause bradycardias?
Damage to the SA node
What is shown on this ECG trace?
Atrial Fibrilation - big indicator is the unevenly spaced QRS complexes.
What does this ECG show?
Narrow complex tachycardia
What does this ECG show?
Broad complex tachycardia
What does this ECG show?
Atrial flutter
Atrial flutter
Re-entrace circuit confined to the right atrium.
What does this ECG show?
Sinus tachycardia
What does this ECG show?
Atrial fibrilation
What does this ECG show?
Prolonged PR interval -
1st degree AV block.
What does this ECG show?
Mobitz type I (Wenckebach)
What does this ECG show?
2nd Degree AV block
Mobitz 2
What do leads V1-V4 show on ECG?
Antero septal = Left anterior descending coronary artery
What does this ECG show?
3rd Degree AV block
What are the red flag signs to watch for in Afib with tachycardia?
- Syncope
- Low BP
- Shortness of breath
- Ischemic chest pain
What is the treatment for Afib with tachycardia?
Control rhythm and rate:
Bisoprolol and amiodarone.
What is amiodarone
Amiodarone is an antiarrhythmic medication used to treat and prevent a number of types of irregular heartbeats. This includes ventricular tachycardia, ventricular fibrillation, and wide complex tachycardia, as well as atrial fibrillation and paroxysmal supraventricular tachycardia.
What is the CHADvas score?
A score to determine the risk of stroke in patients with atrial fibrilation. Guides anti-coagulation treatment.
What is the HAS-BLED score?
What is the HAS-BLED score used for?
The HAS-BLED score also makes clinicians think about the potentially reversible risk factors for bleeding, e.g. uncontrolled blood pressure (the H in HAS-BLED), labile INRs if on warfarin (the L in HAS-BLED) and concomitant use of aspirin/NSAIDs (the D in HAS-BLED).
What effect does high potassium have on an ECG?
Effects of hyperkalaemia on the ECG
Serum potassium > 6.5 mEq/L is associated with progressive paralysis of the atria: P wave widens and flattens. PR segment lengthens. P waves eventually disappear.
What effect can low potassium have on an ECG?
EKG changes can include increased amplitude and width of P wave, T wave flattening and inversion, prominent U waves and apparent long QT intervals due to merging of the T and U wave.
Different classes of anti-arrhythmics:
Cardiac action potential refresher
Quinidine, Lidocaine, Flecainide and procainamide are examples of what class of drug?
Class 1 Na+ sodium channel blockers (anti-arrhythmics).
How do Class 1 anti-arrhythmics work?
Class 1 anti-arrhythmics are membrane stablising Na+ channel blockers.
They work by reducing the rate of phase 0 depolarisation.
Prolong the refractory period.
Increase the threshold for excitability.
Na+ channel blockers also have local anaesthetic properties e.g Lidocaine.
ECG Passmed
ECG repolarisation changes:
Brugada syndrome
Brugada syndrome - occurs due to a mutation in the cardiac sodium channel.
Brugada syndrome is a genetic disorder that can causes a dangerous irregular heartbeat. In many cases, a defect in the SCN5A gene causes the genetic form of this condition. When this defect occurs, it may cause a ventricular arrhythmia. This is a type of irregular heartbeat.
Presents with syncope / cardiac arrest.
What is the drug challenge test used to diagnose Brugada syndrome?
Flecainide IV or Ajmaline - continuous ECG monitoring.
Wolff-Parkinson-White syndrome
Wolff-Parkinson-White (WPW) syndrome is a relatively common heart condition that causes the heart to beat abnormally fast for periods of time. The cause is an extra electrical connection in the heart. This problem with the heart is present at birth (congenital), although symptoms may not develop until later in life.
What is PAF?
Paroxysmal atrial fibrillation occurs when a rapid, erratic heart rate begins suddenly and then stops on its own within 7 days. It is also known as intermittent A-fib and often lasts for less than 24 hours.
What is an AICD?
An implantable cardioverter-defibrillator or automated implantable cardioverter defibrillator is a device implantable inside the body, able to perform cardioversion, defibrillation, and pacing of the heart. The device is therefore capable of correcting most life-threatening cardiac arrhythmias.
ECG Diagnostic patterns of Brugada syndrome
What is meant by 1st degree heart block?
Prolonged PR interval (more than 0.2seconds)
Note each small square is 0.04 seconds.
Explain 2nd degree heart block type 1 aka wenckebach.
2nd degree heart block type 1 is a progressive form of heart block where the PRI becomes progressively longer and eventually the QRS drops.
What are the signs of an nstemi on an ecg?
St depression
T wave inversion
What is the treatment for 3rd degree heartblock?
Atropine / Isoprenaline
Insertion of a cardiac pacemaker.
How does atropine work treat heartblock.
The goal of atropine therapy is to improve conduction through the AVN by reducing vagal tone via receptor blockade. Atropine often improves the ventricular rate if the site of block is in the AVN. The peak increase in heart rate occurs in 2-4 minutes after IV administration; the half-life is 2-3 hours.
Atropine treats bradycardia.
Isoprenaline mechanism of action:
Isoproterenol is a beta-1 and beta-2 adrenergic receptor agonist resulting in the following: Increased heart rate. Increased heart contractility. Relaxation of bronchial, gastrointestinal, and uterine smooth muscle.
