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ECG IN HYPERKALEMIA
• Potassium is most
abundant intracellular
cation
• Most important
determinant of resting
membrane potential
(RMP)
• Mild to moderate levels
of hyperkalemia
• Decrease TP(less
negative)
• Decrease RMP (less
negative)
• Decrease RMP more than
decrease TP
• Diminish difference
between two and
increase excitability
• Decrease in slope of
upstroke of AP (dV/dT)
• Major determinants of
conduction velocity
• Counterbalanced by
decrease in RMP to TP
difference
• Result in ultimate
increase in conduction
velocity initially
• Disproportional effects
of varying levels of
hyperkalemia on RMP
and the TP
• Initial increase in
excitability and
conduction velocity
followed by their
decrease as potassium
level increases further
• Severe hyperkalemia
• Associated with increase
in difference between
RMP and TP
• Leading to decrease in
excitability
• Further decrement in AP
upstroke (dV/dT)
overwhelms positive
effect of TP decrease on
conduction velocity
• Rate of rise of phase 0 of
AP (Vmax) is directly
proportional to value of
RMP at the onset of
phase 0
• Decrease in V max levels
causes a slowing of
myocardial conduction
manifested by progressive
prolongation of P wave,
PR interval and QRS
complex
• Mechanism for early ECG
manifestations of hyperkalemia
(ST depression, peaked T waves,
and short-QT)
• Ikr is mostly responsible for K+
efflux in phases 2 and 3
• Ikr currents are sensitive to
extracellular K+ levels
• As potassium levels increase in
extracellular space potassium
conductance through these
currents is increased
• Leads to increase in slope of
phases 2 and 3
• shorten repolarization time
Modulation of potassium currents by
electrolyte concentration
• Effects of hyperkalemia depend on tissue
involved
• Atrial myocardium most sensitive
• ventricular myocardium less sensitive
• Specialized tissue (SA node and His bundle)
least sensitive
• References
1.Electrolyte disorders and arrhythmogenesis ,Nabil El-Sherif1, Gioia
Turitto2, Cardiology Journal 2011, Vol. 18
2.Hyperkalemia Revisited, Walter A. Parham, MD,Ali A. Mehdirad, MD,
FACC ,Kurt M. Biermann, BS ,Carey S. Fredman, MD, FACC, Tex Heart Inst J
2006