Electricity and the Heart Flashcards
aVR signal on ECG is positive or negative?
Negative so the peaks are upside down because main electrical flow is going away from aVR
lead II is positive or negative?
Positive because main electrical impulses towards this electrode
How to calculate the rate on an ECG?
Count the number of large squares between the big peaks (QRS complex) and divide into 300
Or count small squares and dividie into 1500 so 1500/ number
What does P peak show on ECG?
Atrial depolarisation
What does QRS complex show on ECG?
Ventricular depolarization
What does T peak show on ECG?
Ventricular repolarization
A full thickness damage- STEMi will show what on the ECG?
ST segment elevation, damaged cells repolarize early
A subendocardial damage - NSTEMI will show what on an ECG?
ST segment depression - T wave inversion
If inferior atomic region of heart is affected which coronary artery is most likely affected?
Right coronary
If antero-septal atomic region of heart is affected which coronary artery is most likely affected?
Left anterior descending
If antero-apical region of heart is affected which coronary artery is most likely affected?
Left anterior descending
If antero-lateral atomic region of heart is affected which coronary artery is most likely affected?
Circumflex
If posterior atomic region of heart is affected which coronary artery is most likely affected?
Right coronary
An inferior myocardial infarction will affect which leads? and will show what?
ST elevation in leads II, III and aVF
An anterior/septal myocardial infarction will affect which leads and show what?
ST elevation in leads V2, V3, V4
What does a wide QRS complex show?
Problems with ventricles
What does a narrow QRS complex show?
Problem with SA node
Sign of hyperkalaemia in ECG
Tall T waves, QRS widening
Hypertrophy signs in ECG
Large amplitude of QRS complex
Signs of atrial fibrillation on ECG
No P waves
QRS normal, but irrregularly irregular
What treatment for atrial fibrillation?
Antithrombotic- warfarin, aspirin
Rhythm- digoxin, beta blockers, Ca2+ antagonist etc.
What does Digoxin do?
Slows conduction through AV node- reduces ventricular rate in AF
Signs of ventricular fibrilation?
Continuous bizarre irregular trace
What is a heart block?
Problem with conduction through AV node
What are the different types of heart block?
First degree- all transmission but delayed- long PR interval, normal PQRS complex
2nd degree- partial transmission, some P waves without associated QRS complex, regular or variable
3rd degree- none- no link between P waves and QRS complex, broad QRS complex
What is a bundle branch block?
A problem with conduction through the R or L bundle branch of Hiz
What does ventricular ectopic look on ECG?
Wide, bizarre QRS complex
No P wave
What does a pacing impulse (artefact) look like in an ECG
Instead of P wave have very brief impulse external impulse that stimulates ventricles
Wide QRS complex
