Digoxin Digoxin

Cardiac glycosideCardiac glycoside

Heart Heart

Positive inotropicPositive inotropicDose dependent increase in force of Dose dependent increase in force of contractioncontractionSystole shortened ,diastole is Systole shortened ,diastole is prolongedprolongedStroke volume maintained upto Stroke volume maintained upto considerabe impedenceconsiderabe impedence

More complete emptying of ventricles—More complete emptying of ventricles—inc cardiac outputinc cardiac output

Tone-no effectTone-no effectRate HR is decreasd—improved Rate HR is decreasd—improved circulation restores the diminished vagal circulation restores the diminished vagal tone and abolishes sympathetic tone and abolishes sympathetic overactivityoveractivityPlus digitalis slows heart by vago mimetic Plus digitalis slows heart by vago mimetic and extra cardiac actionand extra cardiac action

Vagal tone is increased byVagal tone is increased by1.1. Reflexly thru nodose ganglion and Reflexly thru nodose ganglion and

sensitization of baroreceptorssensitization of baroreceptors2.2. Direct stimulation of vagal centrDirect stimulation of vagal centr3.3. Sensitisation of SA node to AchSensitisation of SA node to Ach

ExtravagalExtravagal1.1. A direct dippressent action on SA node A direct dippressent action on SA node

and AV nodeand AV node

Electorphysiological propertiesElectorphysiological properties

Action potentialAction potential

Effective refractory periodEffective refractory period

Atrium Atrium 1.1. Decreased by vagal actionDecreased by vagal action2.2. Increased by direct acctionIncreased by direct acction

Net effect more by vagus---excitatory Net effect more by vagus---excitatory and inhomogenous and inhomogenous

VentricleVentricle1.1. ERP reducedERP reduced

AV node and B of HisAV node and B of His1.1. increasedincreased

Excitability Excitability

Enhanced Enhanced

Conduction Conduction

AV conduction slowed-due to AV conduction slowed-due to reduction in rate of 0 phase reduction in rate of 0 phase depolerizationdepolerization

ECG changesECG changes

Decreasd amplitue or iversion of T Decreasd amplitue or iversion of T wavewaveIncreased PR intervelIncreased PR intervelAV block at toxic dosesAV block at toxic dosesShortening of QT intervalShortening of QT intervalDepression of ST segment (Salvador Depression of ST segment (Salvador Dali's mustache )Dali's mustache )

Salvador Dali's mustacheSalvador Dali's mustache

kidneykidney

Diuresis—increasd blood flowDiuresis—increasd blood flow

ADRADR

CardiacCardiac1.1. Tachy arryhthmiasTachy arryhthmias

if due to diuretics + digitoxin---if due to diuretics + digitoxin---hypo K---supply Khypo K---supply KK ---decrease binding of glycosides K ---decrease binding of glycosides to Na –K-ATPaseto Na –K-ATPaseAcute—donot give KAcute—donot give K

1.1. For ventricular arrythmiasFor ventricular arrythmiasLidocaineLidocaine

1.1. SVTSVTPropanololPropanolol

1.1. AV blockAV blockAtropineAtropine