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