Cardiac Rhythms Flashcards
What effects cardiac output?
- Pregnancy
- Exercise
- Respiration
- Age
Right Coronary Arteries
Right coronary artery supply blood to right atrium, ventricle, SA node and AV node
Left circumflex artery
- Supply oxygen rich blood to surfaces of left atrium and ventricles
Cardiac veins
- Three major veins that empty into coronary sinus
Left anterior decending artery
- Supply right ventricle and left ventricle
Left marginal artery
- Supply of blood to the left ventricle
Right marginal artery
- Supply blood to right ventricle and apex
Type 1 MI effects which area of heart
- Athresclerosis in the anterior intraventricular branch of the coronary artery
- 50% of MI occour there
Where do STEMI occour in the heart
- Occour in the anterior intraventricular branch of left coronary artery
- ST elevation above isoelectric point
- Interval between depolarisation and repolarisation of ventricle
- Larger infarction more damage and higher mortality rate
Cardiac pacemaker cells
- Autorhymic pacemaker cells (1%) - unstable resting potential
- Gap junction cause movemet along cardio myoctes propogation of action potential
- Ion moves into cell becomes postive
Calcium channels
- Ryanodine receptors and inositol triphosphate activated calium channels enable conduction of action potential and contraction of myocardium
- L-type calcium channels important regualtion of vasular smooth muscle for cardiac rhythm
Depolarisation of pacemaker cells
- Funny current enter the cell via receptor initiating autorhythmic aspects
- Influx of calcium ions through the outside L type channels on the membrane
- Cause depolarisation
Repolarisation pacemaker cell
- L-Type calcium channels close
- Potassium channel open and coming out of cell causing repolarisation
Depolarisation wave into cardio myocte Phase 0
- Ion come in across gap junction as cardio myocytes recive action potential opening Na+ cause influx cause depolarisation
- 70mV threshold
Depolarisation wave into cardio myocte Phase 1
- Outflux of potassium causes decrease of levels in cell
Depolarisation wave into cardio myocte Phase 2
- Plataeu formation due to influx of calcium countacting eflux of potassium
Depolarisation wave into cardio myocte Phase 3
- Calcium channels close but potassium channels are still open leaving cell
- Repolarisation of cardiac myoctes occour
Action potential comparision to ECG
Absolute refractory
- Phase 1 two 2 represents QRS complex
Action potential comparision to ECG
Effective refractory
- Between 2 and 3 stimulus may cause cells to depolarise include qrs complex and a small part of T
Action potential comparision to ECG
Relative refractory period
- Greater than normal stimulus will depolarise the cell can cause action potential
- Ectopic firing of pacemake cells additional in phase 3
Sinus Node
- Primary pacemaker fires approx 60-100 depolarisations a minute
AV node
- Base of right atrium and fires at rate of 40-60dmp
- Allow ventricles to fill with blood
- Smaller diameter greater resistance and slow opening calcium channels
Ventricular bundle of His
- Right and left right branches fire rate 20-40 dpm
Ventricular purkinje fibres
- Less than 40dpm
- Normal sinus rhythm could have ectopic firing
Ischemic heart disease
- Ventricular fibrullation due to failure of heart muscles to contract
- No Oxygen cause apoptosis of cardiac cells unable to contract in coodinated way
P wave inn sinus rhythm
- Depolarisation of atrium
- Atrial systole 0.1s
QRS wave in sinus rhythm
- Depolarisation of ventricles
T wave in sinus rhythm
- Repolarisation of ventricles
Interpret ECG
- Speed is 25mm/s
- Small box represent 0.04s and big box is 0.2ms
- Shows in bradycardia or tachycardia
Check regularity of ECG
- Is R to R point evenly spaced out
- In bradycardia or tachycardia
Check P wave on ECG
- Is there a P wave before the QRS complex
- Is the PR interval long (>200ms) are they consistant
Check QRS complex on ECG
- Is QRS complex (<100ms) are they consistant looking the same following P wave
- After ST return to isoelectric point
- Aprox 2.5 little box
T wave in ECG
- Is the T wave after QRS complex and upwards not inverted or flattened
PR segment
- Pause between SA and AV
- May become longer possible blockage
- Sinus 3-5 boxes/0.12-0.2
ST segment
- Time between depolarisation of ventricle and repolerisation on isoeletric point
- If elevated by more than 2 boxes could be ischemia or infarction
QT interval with hypercalcemia
- Short QT interval
- Atrial eptopic firing
Hypocalcemia
- Long QT interval
- Possible ventricular tachycardia lead to sudden cadiac death Torsedes DE pointes
Caculations with ECG
- Count boxes between R to R
- Small box x 0.04 then 1/answer
- Multiply answer by 60s
- Alternative run 10 beats count no of R x 6
General Big Box to Beats per min
- 1 big box R-R is 300bpm
- 2 big box apart 150bpm
- 3 big box 100bpm
- 4 big box 75bpm
- 5 big box 60bpm
- 6 big box 50bpm
Dysrhythmia
- Impuse formation altered conduction
Abnormal ECG
- Shape change in ECG conditions changes of cardiac rhythm
Ishcemia
- Acute imaprement of blood flow to the heart
- Prior to evolving into acute MI
Arrhythmia
- Abnormal fast slow or irregular heart rhythms
- Abnormal conduction of heart rhythms
