2cardiac arrhytmia
TRANSCRIPT
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