JH IM Board Review - Arrhythmias II Flashcards
What is the QRS morphology of VT?
Wide QRS complex.
What is the origin of the majority of wide-complex tachycardias?
85% ==> Ventricular.
***remainder are supraventricular w/ aberrant conduction.
What are the 4 types of VT?
- Non sustained (3 beats to 30sec).
- Sustained (>30sec).
- Monomorphic.
- Polymorphic.
What is the determinant of prognosis and Tx in VTs?
Dependent on presence of underlying structural heart disease.
What is the VT which may occur in otherwise healthy pts with structurally normal hearts?
Benign idiopathic VT.
What is the MC form of benign idiopathic VT?
RVOT VT.
What is the clinical presentation of nonsustained VT?
May be asx or cause occasional palpitations.
What is the clinical presentation of sustained VT?
More likely to cause palpitations, lightheadedness, near-syncope, syncope, cardiac arrest.
What is the 1st step in the diagnosis of VT?
Evaluation for structural heart disease.
==> Do echo.
What are the additional studies for the evaluation of structural heart disease besides echo in pts with VTs?
(3)
- Stress testing with imaging.
- CT or conventional coronary angio.
- Cardiac MRI.
What is the monitoring for a pt with VT?
Depending on sx frequency — May include 24-48h Holter monitor.
Or 30-day event monitor.
Or long-term implantable loop recorder (ILR).
What is the form of VT in which EPS is most useful?
In the evaluation of monomorphic VT.
What is the tx in an hemodynamically unstable pt with VT?
Emergent cardioversion/defibrillation.
What is the major determinant of chronic tx of most VTs?
The underlying presence of ischemic heart disease.
What is the prognosis in pts with monomorphic VT and no underlying structural heart disease (ie idiopathic VT)?
Good prognosis.
80-90% cure rates w/ ablation.
What are the target groups in which we should consider placing an ICD (shown to improve survival)?
(2)
- IHD w/ previous MI and LVEF 30% or less measured more than 3mo after revascularization + medical tx.
- Ischemic or non ischemic cardiomyopathy (LVEF <35%) and NYHA II or III despite at least 3mo of guideline-directed medical tx w/ beta-blockers and afterload-reducing agents.
What is the role of EP study in some pts w/ milder forms of cardiomyopathy who have non sustained VT or sx possibly related to VT (palpitations, syncope)?
May be useful for risk stratification.
What is a useful adjunctive therapy for recurrent VT in pts w/ ICDs that can help prevent sx and recurrent ICD shocks?
Catheter ablation.
What is torsades?
A form of polymorphic VT a/w prolonged V-repolarization, manifesting on ECG as a prolonged QT interval.
What are the main syndromes with which Torsades is a/w?
Both congenital + acquired long QT syndromes.
What is the usual cause of congenital LQT syndrome?
Mutations in cardiac ion channels affecting ventricular repolarization (MC K or Na channels).
What is the percentage of pts with congenital LQT syndrome in which a genetic mutation can be identified?
60-70%.
What are the 2 MC associations of acquired LQTS?
- Drugs.
2. Electrolyte disturbances (ie hypokalemia, hypomagnesemia).
What is the usual precipitant of torsades (Polymorphic VT)?
Premature ventricular contraction occurring on the preceding T wave (R-on-T wave).
What is the acute management of torsades?
4
- IV Mg (2g IV push, repeat as necessary).
- Correct underlying metabolic abnormality or stop offending meds.
- Consider IB antiarrhythmics (IV lidocaine 1-1.5 mg/kg over 2min).
- Increase HR to decrease QT duration.
What are the 2 ways by which you can increase HR therapeutically in order to decrease QT duration?
- IV isoproterenol.
2. Temporary pacer and overdrive pace to 90-100 beats/min.
What is the chronic management of torsades?
- Avoid QT prolonging drugs.
- Avoid hypokalemia and hypomagnesemia.
- Beta blockers in pts with congenital LQTS.
- Consider ICD placement in selected pts.
What are the high risk pts w/ congenital LQTS that may be helped by ICD placement?
- Pts w/ recurrent syncope.
- Torsades on beta blockers.
- Personal/FHx of cardiac arrest.
- Other high risk markers.
What is the definition of syncope?
Transient + involuntary LOC and postural tone (lasting seconds to minutes) caused by cerebral hypoperfusion, followed by full spontaneous recovery.
What is the percentage of syncopes in which the cause remains unknown?
25-40%.
What is NOT included in the definition of syncope?
LOC caused by seizure, hypoglycemia, cataplexy etc.
What is essential in all pts with syncope?
ECG.
What is the management in a pt with a vasovagal syncope?
5
- Incr. Fluid intake + salt intake.
- Advise pts to stand slowly from a seated position.
- Eliminate offending meds.
- Consider midodrine or SSRIs in refractory cases.
- Consider pacemaker placement in exceptional cases a/w prolonged asystole.
What is the definition of SCD?
Sudden, unexpected death that occurs within 1h of sx b/c of documented or presumed cardiac cause.
What is the percentage of SCDs for which V-fib or pulseless VT is responsible?
30-60%.
What is often the 1st manifestation of IHD?
SCD.
What is the use of ECG in the evaluation of SCD?
4
- Evidence of MI or ischemia.
- WPW syndrome.
- Prolonged QT.
- Brugada.
What are the indications for ICD implantation?
- Documented VT/VF cardiac arrest not caused by transient or reversible causes (ie MI, intoxication).
- Documented familial or inherited conditions w/ high risk of life-threatening arrhythmia, such as LQTS, HCM.
- Documented previous MI (>40 days), LVEF <40%, inducible sustained VT or VF at EPS (MADIT-1 criteria).
- Documented previous MI, LVEF<30% either 40 days following medically managed MI or 3mo following revascularization (PCI or bypass surgery).
- Pts w/ ischemic or nonischemic DCM, measured LVEF <35%, and NYHA II or III despite at least 3mo of guideline-directed medical tx.
- Pts w/ NYHA IV who meet other requirements for cardiac resync therapy.
