PHYL3002 Lecture Notes - Lecture 7: Long Qt Syndrome, Channelopathy, Torsades De Pointes
LECTURE SEVEN: Cardiac Arrhythmia and the Measurement of
Ion Transport
Ion Transport:
• Roles in
o Cellular excitability
o Contraction
o Secretion
o Activation of cellular second messengers
o Regulation of cell transcription
o Volume regulation
• Ions travel through
o Transporters
▪ Non-excitable cell transporters maintain concentration
gradients across apical and basolateral membranes
▪ Maintain Ca2+/pH/Vm in excitable cells
o Ion channels
▪ Mostly expressed in excitable cells
▪ Also present in non-excitable cells
Families of Gated Channels:
• Voltage sensitive gating
• Ligand sensitive gating
• Messenger-activated gating
• G-protein gating
• Stretch-activated gating
Cardiac Arrhythmia:
• Disorder in rate, rhythm, origin or conduction of impulses within the
heart
• Precipitating factors
o Hypoxia/ischaemia
o Excessive autonomic discharge
o Drugs (e.g. anaesthetic, cardiac glycosides etc.)
o Electrolyte imbalance
o Genetic mutation in an ion channel or heart function → e.g. SIDS,
familial hypertrophic cardiomyopathy
• Abnormalities in impulse formation
o Sinus bradycardia/tachycardia
o Ectopic pacemakers
• Abnormalities in impulse conduction
o AV block
o Slowed conduction with re-entry
Sudden Cardiac Death:
• Unexpected death defined as that occurring with the first hour of the
onset of symptoms
• Responsible for 250 000-300 000 deaths annually in the US
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