Electrical Myopathies Flashcards
Why might verapimil be useful for LQTS?
In 2014, researchers from Japan found the a specific mutation of KCNE1 (LQT type 5) results in rapid degradation of the mutant protein that participates in the assembly of the K+channel. Verapimil was shown to stabilize the protein and slow its degradation and improve channel performance. S SAKATA PACE 2014
Name 5 anti-epileptic medications that block sodium channels? why is knowing these important for an EP doc?
phenytoin, carbamazepine, oxcarbazepine, lamotrigine,and gabapentin
Describe the relationship between epilepsy, anti-seizure medications, and sudden death
Symptomatic (poorly controlled) epilepsy is associated with a 3-fold increased risk of VT, VF, and SCD. AEM’s (those which cause sodium channel blockade and carbamazepine in particular) are also associated with an independent risk of SCD. Source: Netherlands Integrated Primary Care Information (IPCI) project. Bardai Heart 2014.
What is the prevalence of LQTS?
1:2500 based on the newborn population study by Peter Schwartz in 2009 Circ.
This ECG pattern is most consistent with what type of LQTS
LQTIII
Both LQTIII and Brugada syndrome can involve mutations in the SCN5A gene. What is the difference?
LQTIII is a gain of function mutation whereby a small percentage of Na channels do not inactivate after repoloarization resulting in continued inward influx of sodium during the cardiac cycle. Brugada is a loss of function SCN5A mutation.
What are the therapies for VT storm in Brugada syndrome?
Quinidine (blocks Ito) and isuprel. In case of failure of these therapeutic options, ablation of the triggering ventricular ectopies should be attempted.
What form of LQTS is associated with bidirectional VT?
LQT type 7, Andersen-Tawil Syndrome (KCNJ2)
In which condition does a family hx of sudden death increase your risk of sudden death? LQTS Type I or HCM
HCM. (family history of SCD in LQT1 does not necessarily increase an individuals risk of an event)
Should all patients with AVNRT be screened for Brugada?
A theoretical link between AVNRT and Brugada has been proposed. A paper in July 2015 HR, purports to demonstrate an association between the 2. Sam Viskin and others wrote an editorial discretiting the paper and recommended against screening patients with AVNRT.
Measuring the QTc interval in a fetus is technically challenging and requires equipment not present at the majority of centers. What other routinely measured parameter might act as a suitable surrogate to identify patients at risk for long QT syndrome in the fetus?
Fetal heart rate. In the Aug 2015 issue of Circ A&E, researchers from Sweden found a strong correlation between fetal heart rate and presence and severity of LQT mutations (no mutation, 143±5 beats per minute; single mutation, 134±8 beats per minute; double mutations, 111±6 beats per minute; P<0.0001)
It is generally believed that patients w/LQT III are at lower risk for events during exercise compared with other LQT types. Why might this be so?
In a publication from Circ A&E published Aug 2015, researchers found that elevated intracellular Ca2+ suppresses mutant channel INaL and protects cells from delayed repolarization. These findings offer a plausible explanation for the lower arrhythmia risk in LQT3 subjects during fast heart rates.
To what electroanatomic finding does the surface ECG finding of an epsilon wave correspond?
In a study publised in JCE Jan 2016, Median endocardial scar burden was significantly higher in patients with epsilon waves even compared with patients with CRBBB (34.3 vs.11.3 cm2 , P<0.01). Timing of epsilon wave corresponded to activation of the subtricuspid region.
Bazett’s correction for LQTS is most linear over physiologic heart rates between 60 and 100 beats per minute. What correction formula works better at heart rates greater than 100 bpm?
Hodges formula has been shown in a large adult population study to more accurately reflect QT prolongation associated risk of adverse events. Bazett’s formula overestimated the QT interval and did not predict risk at faster heart rates. Not clear how this applies to kids with normal heart rates > 100 bpm.
