CC Jan 2017 Long QT syndrome

echoecho's version from 2017-03-26 23:31


Question Answer
Define QT interval?On EKG corresponds to the entire duration from depolarization to repolarization of the ventricular myocardium
Why is the "corrected QT interval" or QTC more useful?Because it corrects for the heart rate
How is QTc (corrected QT interval) calculated?By dividing the QT interval by the square root of the R-R interval (in seconds).
Are QTc intervals gender dependent?Yes
What would be an abnormal QTc for men? For women?440 milliseconds; 460 milliseconds
Which lead is usually the most useful for measuring QT?Lead II
Define congenital long QT syndrome (cLQTS)?It is a cardiac repolarization disorder resulting from a sodium, potassium or calcium channelopathy
Abnormal repolarization may manifest electrically as a ventricular arrhythmia, list these?1) polymorphic ventricular tachycardia (VT), 2) tornadoes de pointes. 3) ventricular fibrillation (VF) 4) sudden cardiac death
Is atrial fibrillation related to prolonged QT syndrome?No
How can patients present?1) palpitations 2)seizure 3)syncope (without any preceding prodrome) OR 4) sudden death
The trigger for syncope or sudden death may be what?1) physical stress (exercise) 2)emotional stress 3)loud noise
Although the mechanism is unclear, patients are more likely to develop tornadoes while doing what 2 activities than with other athletic activities?1) swimming 2)diving
Estimates show that one in ______ people in the US may have cLQTS?10,000
It is more common in what gender?women
Does pregnancy provide some protection for women with cLQTS? Is there a relatively greater risk in the postpartum period?yes; yes
Symptoms may appear at any age, including infancy, but are most likely to develop in what group of patients? 1) preteens 2) teenagers 3) young adults
There are links between the cLQTS and hundreds of mutations in ___ genes?10
Most cases are ______-____ syndrome? What type of autosomal form is it?1) Romano-Ward syndrome 2) autosomal dominant
Other primary clinic phenotype is____ and _____-_____ syndrome? What type of autosomal form is it?1) Jervell and Lange-Nielsen syndrome 2) autosomal recessive
What type of tests for mutations are available and may be useful to guide management in patients with suspected LQTS?genetic
Testing may also be helpful in persons with ______ clinical criteria (though neg mutation testing does not r/o the D.C.), as well as in family members of a patient with a known mutation?borderline
Schwartz proposed a scoring system in 1993 to aid clinicians in diagnosis, although it does not incorporate any genetic criteria, list the diagnostic criteria for LQTS as to the 3 categories?1) ECG findings. 2) clinical hx 3) family hx
Regarding the Schwartz scoring system, list the points in the category ECG? > 480 milliseconds (3 points); 460-469 milliseconds (2 points); 450-459 milliseconds (male only) (1 point); tornadoes de pointes (1 point); T-wave alternates (1 point); Notched T wave in 3 leads (0.5 points); low heart rate for age (< 2nd percentile)
Regarding the Schwartz scoring system, list the points in the category clinical history?syncope due to stress (2 points); syncope without stress (1 point); congenital deafness (0.5 point)
Regarding the Schwartz scoring system, list the points in the category family history?family hx of long QT syndrome (1 point); unexplained sudden death in an immediate family member < 30 years old (0.5 point)
Regarding the Schwartz scoring system, list the scoring?< 1 means low probability of LQTS; 2-3 means intermediate probability; > 4 points means high probability of LQTS
What is the only diagnostic test needed to make a diagnosis of LQTS? What other test may be helpful if the QTc is equivocal in a family member (440-460 milliseconds)?1) resting EKG. 2) ambulatory EKG
Ideally, an affected patient can be found to have an identified _____ mutation that allows directed testing of all immediate family members?LQTS
Why have beta blockers traditionally been the recommended therapy for cLQTS?because they blunt the dare Regiec surge that may predispose to cardiac dysrhythmias and can shorten QTc
List the two long-acting beta-blocker preparations that have been the most frequent choices?1) atenolol (Tenormin) 2)nadolol (Cougars)
Rarely, in those failing beta-blockade, what procedure may be an option?left cardiac sympathetic enervation (left stellate cardiac ganglionectomy)
Patients with cLQTS who are at high risk for sudden death (successfully resuscitated cardiac arrest, recurrent syncope or torsades de pointes) benefit from an implantable ______ _______?cardioverter-defibrillator (ICD) with continued beta-blocade
What other newer option needs additional testing to be used?radio frequency ablation
*** It is recommended that persons with cLQTS avoid ______ or ______ sports because exercise can precipate a cardiac event?competitive; strenuous
*** The American College of Cardiology, the American Heart Association and the European Society of Cardiology have rated the 3 following interventions for cLQTS, list these 3?1) Lifestyle modification is recommended for patients with an cLQTS diagnosis 2) Beta-blockade is recommended for patients with a clinical diagnosis of cLQTS (QTc > 460 milliseconds for women, > 440 milliseconds for men 3) implantation of an ICD with use of beta-blockers is recommended for survivors of cardiac carrest who have reasonable expectation of survival > 1 year and in patients with syncope or ventricular tachycardia while receiving beta-blockers
In addition to cLQTS, long QT can be an acquired conditions. A number of medications can prolong the QTC and increase the risk of syncope and sudden death. List the 6 classes of medications that can prolong the QT interval?1) fluoroquinolones 2) macrolide antibiotics 3) antiarrhythmics 4) antipsychotics 4)antidepressants 5) miscellaneous
List the examples of medications in the fluoroquinolone class?1)moxifloxacin (Avelox), 2) levofloxacin (Levaquin)
List the examples of medications in the macrolide antibiotics?1) erythromycin (E-mycin) 2) clarithromycin (Biaxin) 3)lower risk with azithromycin (Zithromax)
List the examples of medications in antiarrhythmics?1) sotalol (Betapace) 2) amiodarone (Cordarone) 3)procainamide (Pronestyl) 4)flecainide (Tambocor) 5) dofetilide (Tikosyn) 6) quinidine (Quinaglute) 7) disopyramide (Norpace)
List the examples of medications in the antipsychotics?1) haloperidol (Haldol) 2)chlorpromazine (Thorazine) 3) Thioridazine (Mellarill)
List the examples of medications in the antidepressants?1)citalopram (Celexa) 2) lower risk with escitalopram (Lexapro)
List the examples of medications in the miscellaneous?1) methadone 2) chloroquine (Aralen) 3) pentamidine (Pentam) 4)odansetron (Zofran)
The above medications may prolong the QT interval de novo, but they may also exacerbate the symptom in patients with ______ long QT syndrome?congenital
What is the intervention for drug-associated LQTS?discontinuation of the drug, if possible
Acquired long QT interval can also occur with what conditions?1) hypokalemia. 2) hypocalcemia 3) hypomagnesemia 4)hypothyroidism 5)cardiomyopathy 6) severe bradycardia 7) high-grade AV block
What is the treatment for acquired forms of long QT?correction of the underlying abnormality
*** SUMMARY = Prolonged QT interval on EKG is associated with a significant risk of ______ arrhythmia, ______ and sudden _______?ventricular; syncope; death
*** SUMMARY = The majority of cases are _____ (autosomal _____ inheritance) and involve a malfunction in the cardiac ion channels (channelopathy)?hereditary; dominant
*** SUMMARY = _____-_____ therapy is the primary therapeutic intervention, but invasive approaches such as implantation of _____-______ may be necessary when pharmacological control is not achieved?beta-blocker; cardioverter-defibrillator
*** SUMMARY = Acquired long QT can be seen with some medications including certain _______, _____ and ______?antiarrhythmics, antibiotics, psychotropics