Cardio 3
- Created by: Mohsin
- Created on: 09-04-18 13:09
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- Cardio Therapeutics 3
- ECG leads
- recorded using 3 limb electrodes
- one on each arm and one on the left leg
- each limb acts as an electrical conductor
- Form a triangle = Einthoven's triangles
- one on each arm and one on the left leg
- 6 skin electrodes used in clinical practice
- angle of the largest dipole = electrical axis of the heart
- recorded using 3 limb electrodes
- ECG
- T wave is upright - repolarisationoccurs in reverse sequence to de-polarisation
- due to short action potentials of epicardial and basal myocytes
- T wave is upright - repolarisationoccurs in reverse sequence to de-polarisation
- Cardiac excitation- contraction coupling
- Electrical excitation of the myocyte
- mishandling of Ca2+
- causes contractile dysfunction and arrhythmias
- myofilament Ca2+ sensitivity
- reduced by acidosis, elevated Mg2+ and P levels
- occurs during ischaemia
- mishandling of Ca2+
- Electrical excitation of the myocyte
- Effects of electrolytes on the myocardium
- Causes of voltage across a semi-permeable membrane
- Na
- 135 - 146 mmol/L
- K
- arrhythmia is associated with potassium disorders
- 3.5 - 5.0 mmol/L
- Potassium
- High intracellular conc.
- maintains the excitability of nerve and muscle cells
- regulated by: aldosterone, pH, catecholamines, insulin and levels of bicarbonate
- hyper/ hypo kalaemia can cause abnormalitiescardiac conduction
- HYPER- kalaemia
- suppressed conduction
- Peaked T wave or prolonged PR interval and widened QRS interval
- Cardiac arrest when serum conc. is greater than 0.8mmol/L
- repolarisationabnormalities
- HYPO- kalaemia
- affects conduction of action potential
- flattened T waves
- prolonged PR interval
- ST depression
- Predominent U waves
- ST depression
- prolonged PR interval
- can be caused by insulin, dopamine and B2 antagonists
- HYPER- kalaemia
- Mg
- 0.7 - 1.1 mmol/L
- Ca
- 2.20 - 2.67 mmol/L
- spontaneous release of Ca2+ can lead to tachycardia
- happens after a period of sympathetic nerve stimulation or adrenaline influx
- Generates action potential
- Muscle contraction
- Na
- Renal excretion = maintain electrolyte balance
- changes to renal function can affect electrolyte concentration
- Impaired balance of electrolytes caused by...
- Kidney disease
- Hypoaldesteronism
- adrenal insufficiency
- Impaired balance of electrolytes caused by...
- changes to renal function can affect electrolyte concentration
- Causes of voltage across a semi-permeable membrane
- Classification of SUPER ventricular dysrhythmias
- Atrial flutter
- caused by re-entry circuit within the RIGHT atrium
- Atria ventricular nodal reentry tachycardia (AVNRT)
- above bundle of His
- common cause palpitations in patients with no structural heart abnormalities
- Atrial fibrillation
- irregularly irregular rhythm
- No P waves
- absence of isoelectric baseline
- Atrial ectopic beat
- irregular P wave
- arise from ectopic pacemaking tissue within the atria
- Atrial flutter
- Classification - Ventricular Dysrhythmias
- Ventricular Tachycardia
- Rapid heart beat which starts in the ventricles
- pulse rate over 100bpm
- 3 irregular heartbeats in a row
- pulse rate over 100bpm
- Rapid heart beat which starts in the ventricles
- Ventricular fibrillation
- irregular electrical currents
- heart contracts in disorganised way
- lots of energy used but no function
- can cause sudden death
- lots of energy used but no function
- heart contracts in disorganised way
- irregular electrical currents
- Ventricular flutter
- loss of organised electrical activity
- extreme form of VT
- non identifiable P, QRS or T waves
- rate more than 200bpm
- non identifiable P, QRS or T waves
- extreme form of VT
- loss of organised electrical activity
- Torsade de Pointes
- Form of VT associated with long QT syndrome
- lots of drugs can cause this
- Long QT syndrome
- prolonged ventricular repolarisation
- caused by: TCA's, fluconazole, erythromycin, methadone, SSRI's, haloperidol
- prolonged ventricular repolarisation
- Form of VT associated with long QT syndrome
- Accelerated idio-ventricular rhythm
- ectopic ventricular pacemaker exceeds that of the sinus node
- ventricular rhythm between 40-120bpm
- benign rhythm usually self limiting
- ventricular rhythm between 40-120bpm
- ectopic ventricular pacemaker exceeds that of the sinus node
- Ventricular Tachycardia
- ECG leads
- Heart block (Atrio-ventricular)
- block in the electrical conduction system in the heart
- heart beats more slowly
- defined by PR interval
- 1st degree: benign. lengthening of the PR interval
- 2nd degree: Atrial flutter (2 P waves to every QRS)
- 3rd degree: drug induced (verapamil and b-blockers)
- 3 P waves to every QRS
- potentially fatal
- 3 P waves to every QRS
- block in the electrical conduction system in the heart
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