long qt syndrome

ECG OF THE WEEK

-Dr. Devendra Patil

Prof. Dr. S.Magheshkumar’s Unit

Indira 70/ F Retd. Matron GSH came with chief complains of Fever since 20-25 days Intermittent ,high grade

asso. with chills n rigors

Taking some oral medication from pvt.

K/c/o SHT and DM since 15 yrs on Rx.

2 days later she had a cardiac arrest with the following ECG pattern

ECG findings :-

Heart Rate – 50 bpmRegular Sinus rhythmNormal Axis P wave - normalPR interval - 0.12 secQRS complex – normal width and shape

QT interval – 0.56 secQTc interval - 0.509 secT wave – normal

Impression :- Bradycardia with acquired prolonged QT syndrome

Pt. was shifted to ICCU.

She developed cardiac arrest .Pulse – not feltBP - not recordableECG showed Vent. Tachycardia

200 J Biphasic DC shock was given and was reverted to sinus rhythm

A Temporary Cardiac Pacemaker was inserted following Rt. Femoral Vein Catheterization and she was reverted to sinus rhythm over the next 2 days

QT interval : beginning of Q-wave upto the end of T-wave.

QT interval : total duration of ventricular activity.

Need for QTc Interval :The QT interval varies with

RR interval. False high values may be noted in Bradycardias.

LONG QT SYNDROME

Formula accepted for QTc is:

BAZETT’s Formula : QTc = QT ∕√ (RR)

A useful rule of thumb is that, with a normal heart rate ( 60 - 100 bpm), the QT interval SHOULD NOT exceed half the RR interval.

LONG QT SYNDROME

ACQUIREDCONGENITAL

Due to Genetic defects in K+ channels involved during repolarization.Severe form Includes: 1. Jervell Lange Syndrome (deafness, syncopal attacks , sudden death )

2. Romano Ward Syndrome (similar to Jervell Lange syndrome but without deafness )

•DRUGS •During Sleep•Hypocalcemia•Acute Myocarditis•Acute Myocadial Infarction• Hypothermia•HOCM•Cerebral Injury•Advanced AV Blocks

Congenital LONG QT SYNDROME

LQT1 GeneMost common typeQT interval fails to shorten post exerciseT wave is broad and occupies majority QT intervalMost common triggers: exercise, emotional stress.80% have first presentation < 20 yrsJervell Lange syndrome and Romano Ward syndrome are severe forms.

LQT2 Gene T wave tends to be bifid and notchedAdditional Triger factors are sleep, auditory stimulationRespond to B-Blockers

LQT3 GenePoorest prognosis amongst allT wave is asymmetrical or Late biphasicTrigger factor : Bradycardia ( sleep )B-Blockers ContraindicatedExercise is not Restricted

AntiarrhythmicsClass 1: ajmaline*, cibenzoline*, dihydroquinidine*, disopyramide, encainide*, flecainide, mexiletine, pirmenol*, procainamide, propafenone quinidine*Class 3: almokalant*, amiodarone, azimilide*, bretylium, dofetilide*, dronedarone*, d-sotalol*, ersentilide*, ibutilide*, nifekalant*, sematilide*, sotalol, terikalant*

Anti-anginals/vasodilatorsbepridil*, lidoflazine*, prenylamine*, ranolazine, terodiline*, vardenafil

Anti-hypertensivesindapamide, isradipine, moexipril/hydrochlorthiazide, nicardipine

Antihistaminesastemizole*, azelastine, diphenhydramine, ebastine*, hydroxyzine, terfenadine*

Serotonin agonists and antagonistscisapride*, dolasetron, granisetron, ketanserin*, ondansetron

AntimicrobialsMacrolide antibiotics: azithromycin, clarithromycin, erythromycin, roxithromycin*, spiramycin, telithromycin

Quinolone antibiotics: ciprofloxacin, gatifloxacin*, gemifloxacin*, grepafloxacin*, levofloxacin, moxifloxacin, ofloxacin, sparfloxacin*

Antifungals: cotrimoxazole, fluconazole Others: pentamidine, trimethoprim sulfa Antiviral: foscarnet (HIV)

DRUGS that may cause QT PROLONGATION

Antimalarials Chloroquine, halofantrine*, lumefantrine, quinine

Psychiatric drugsTricyclic antidepressants: amitriptyline, amoxapine*, clomipramine, desipramine*, doxepin, imipramine, nortriptyline, protriptyline*, trimipramine

Phenothiazines: chlorpromazine, fluphenazine, prochlorperazine, thioridazine*, trifluoperazine

Others: atomoxetine, citalopram, clozapine, droperidol*, fluoxetine, haloperidol, levomethadyl*, lithium, maprotiline, mesoridazine, methadone, paroxetine, pericycline, pimozide, quetiapine, risperidone, sertindole, sertraline, trazodone, venlafaxine, zimeldine*, ziprasidone

Anticonvulsantfelbamate*, fosphenytoin

Anti-migrainenaratriptan, sumatriptan, zolmitriptan

Anti-cancerarsenic trioxide, geldanamycin*, sunitib, tacrolimus, tamoxifen

Othersalfuzosin, chloral hydrate, clobutinol*, domperidone, galantamine, octreotide, organophosphates*, perflutren lipid microspheres, probucol, solifenacin, tizanidine, tolterodine, vasopressin

Stimulant drugsSome cold remedies contain these drugs so it is important always to check the label.adrenaline (epinephrine), amphetamine, cocaine, dexmethylphenidate, dobutamine, dopamine, ephedrine, fenfluramine, isoprenaline (isoproterenol), levalbuterol, metaproterenol, methylphenidate, midodrine, norepinephrine (noradrenaline), phentermine, phenylephrine, phenylpropanolamine, pseudoephidrine, ritodrine, salbutamol (albuterol), salmeterol, sibutramine, terbutaline

DRUGS that may cause QT PROLONGATION Continued…

COMPLICATIONS OF LONG QT SYNDROME Torsades des pointes ( polymorphic

ventricular tachycardia )More commonly seen in women

Manifestation of subclinical LQTS

Potentiated by bradycardia and hypokalemia

drug usually blocks Ikr channel

triggered by early afterdepolarizations due to intracellular Ca+ accumulation from a prolonged actin potential plateau

heterogenicity of myocardial repolarisation predisposes to polymorphic ventricular activity

TREATMENT Caution has to be exercised during

administering multiple drug regimes. They may cause QT Prolongation and TDP.

Correction of K+ and Mg++ levels Temporary Pacing Cautious Infusion of Isoprotenol Class 1B anti arrythmics (no QT

prolongation seen)

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