Cardiac Arrhythmias

Alterations in impulse generation; abnormality in impulse conduction

Alterations in impulse generation; alterations in SAN frequency

Abnormality in impulse generation; alterations in AVN frequency

Decreased normal automaticity; abnormal automaticity (damaged myocardial cell remains partially depolarised)

Enhanced normal automaticity (competing stimuli); myocardium repolarises too early

Enhanced normal automaticity (competing stimuli); abnormal automaticity (damaged myocardial cell remains partially depolarised)

Unidirectional block leading to re-entry phenomenon

Bidirectional block leading to re-entry phenomenon

Unidirectional block leading to escape phenomenon

1 - Na blockers; 2 - B blockers; 3 - K blockers; 4 - Ca blockers; 5 - other

1 - K blockers; 2 - Ca blockers; 3 - other; 4 - Na blockers; 5 - B blockers

1 - Ca blockers; 2 - B blockers; 3 - Na blockers; 4 - K blockers; 5 - other

Bind most rapidly to open channels - greater degree of blockade when channels are opened frequently

Bind most rapidly to closed channels - greater degree of blockade when channels are closed frequently

Bind most rapidly to lesser-used channels - greater degree of blockade when channels are used less frequently

1a - moderate blockers, increase action potential duration and resting potential, e.g. procainamide; 1b - weak blockers , decrease action potential duration and resting potential, e.g. lidocaine, 1c - strong blockers, no change in action potential or resting potential duration, slows conductivity, e.g. flecainide

1a - moderate blockers, increase action potential duration and resting potential, e.g. procainamide; 1b - weak blockers , decrease action potential duration and resting potential, e.g. lidocaine, 1c - strong blockers, no change in action potential or resting potential duration, slows conductivity, e.g. flecainide

1a - weak blockers, decrease action potential duration and resting potential, e.g. procainamide; 1b - strong blockers , increase action potential duration and resting potential, e.g. lidocaine, 1c - moderate blockers, no change in action potential or resting potential duration, slows conductivity, e.g. flecainide

Increase automaticity and conduction velocity, increase refractory period

Increase automaticity and conduction velocity, decrease refractory period

Decrease automaticity and conduction velocity, increase refractory period

Prolong cardiac action potential and refractory period of cardiac muscle

Shorten cardiac action potential and refractory period of cardiac muscle

No effect on cardiac action potential but decrease refractory period of cardiac muscle

Prolong plateau phase of action potential and decrease force of contraction

Shorten plateau phase of action potential and decrease force of contraction

Shorten plateau phase of action potential and increase force of contraction

Supraventricular tachycardia

Atrial fibrillation

Life-threatening tachycardia