Cardiac arrhythmia

Abnormal cardiac rhythm usually involving a change in rate or regularity.

Synonym: dysrhythmia

EtiologyPhysiological:

-sympathetic or parasympathetic control changes eg. Stress , anxiety, exercise , smoking.Hypothyroidism, hyperthyroidism, hypoadrenalism,

hyperkalemia, hypokalemia and other electrolyte changes.

Pathological:

Valvular heart disease. Ischemic heart disease.----------MI causing death of

pacemaker cells or conducting tissue.Hypertensive heart diseases.Congenital heart disease.Cardiomyopathies.Carditis.RV dysplasia.Drug related.Pericarditis. Pulmonary diseases.Others.

CLINICAL EVALUATIONI. PHYSICAL FINDINGS

Palpitation.Dizziness.Chest Pain.Abnormal pulse rate , rhythm or amplitudeDyspnea.Anxiety and confusion (from reduced brain perfusion)Fainting (syncope)Skin pallor or cyanosisReduced blood pressureWeaknessConvulsionsDecreased urinary outputSudden cardiac death.

II. DIAGNOSTIC TEST RESULTS ECG

electrophysiological (EP) testing

His bundle studyIII. LAB FINDINGS:

hyperkalemia (>5mEq/L)Hypocalcemia

(<4.5mEq/L)

hypomagnesemia(<2.5mEq/L)

Mechanism of Arrhythmogensis1. Disorder of impulse formation.

a) Automaticity.b) Triggered Activity.

1) Early after depolarization.2) Delayed after depolarization.

2. Disorder of impulse conduction.a) Block – Reentry.

b) Reflection.

3. Combined disorder.

Nomenclature for describing arrhythmiasRate

tachycardiabradycardia

Origin:sinusatrialnodalsupraventricularre-entrantventricular

Pattern:ectopicPremature contractionparoxysmalflutterfibrillationblocktorsadeselectromechanical dissociation

Duration:i) paroxysmal- self terminating

episodes upto 7 daysii) persistent -non self

terminating more than 7 days

iii) permanent - not responding to cardioversion attempts

iv) recurrent: returning after once stopped.

Strategies of Antidysrhythmic Agents

A. Alter automaticityi. decrease slope of Phase 4 depolarizationii. increase the threshold potentialiii. decrease resting (maximum diastolic) potential

B. Alter conduction velocity i. mainly via decrease rate of rise of Phase 0

upstrokeii. decrease Phase 4 slopeiii. decrease membrane resting potential and

responsivenessC. Alter the refractory period

i. increase Phase 2 plateauii. increase Phase 3 repolarizationiii. increase action