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Long QT Syndrome Exposed by Effort: Difference between revisions
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== Editor's comments == | == Editor's comments == | ||
The congenital long QT syndrome (LQTS) is a genetically transmitted disease. Mutations causing LQTS have been identified in 5 genes each encoding a cardiac ion channel and its regulatory subunit | The congenital long QT syndrome (LQTS) is a genetically transmitted disease. Mutations causing LQTS have been identified in 5 genes each encoding a cardiac ion channel and its regulatory subunit <cite>Splawski</cite>. LQT1 is caused by mutations in the KCNQ1 gene encoding a potassium channel conducting the IKs potassium current. | ||
Detection of QTc prolongation in the basal ECG is the hallmark feature in the diagnosis of LQTS. However, studies that investigated QTc in genotyped LQTS families reported LQT1 patients having disease-causing mutations despite a normal QTc | Detection of QTc prolongation in the basal ECG is the hallmark feature in the diagnosis of LQTS. However, studies that investigated QTc in genotyped LQTS families reported LQT1 patients having disease-causing mutations despite a normal QTc <cite>Vincent</cite><cite>Zareba</cite><cite>Priori</cite>. | ||
Type 1 LQTS is characterized by QT-prolongation, in particular during exercise. The QT-interval fails to adapt to an increase in rate and therefore inappropriately prolongs during exercise | Type 1 LQTS is characterized by QT-prolongation, in particular during exercise. The QT-interval fails to adapt to an increase in rate and therefore inappropriately prolongs during exercise <cite>Vincent2</cite><cite>Moretti</cite>. In conjunction, events (dizziness, syncope and sudden death) are typically triggered by adrenergic stimuli like exercise, diving and swimming <cite>Schwartz</cite>, the age of onset of complaints is usually around 5 years. | ||
The present case exemplifies a LQT1 patient in whom QT prolongation only may be detected during an exercise test. In these cases, a careful family history should be taken and molecular genetic screening is mandatory. | The present case exemplifies a LQT1 patient in whom QT prolongation only may be detected during an exercise test. In these cases, a careful family history should be taken and molecular genetic screening is mandatory. | ||
In symptomatic patients with LQT1, treatment of choice is a ß-blocker titrated up to the highest possible tolerated dose | In symptomatic patients with LQT1, treatment of choice is a ß-blocker titrated up to the highest possible tolerated dose <cite>Villain</cite><cite>Priori2</cite>. Asymptomatic young patients should receive prophylactic treatment but asymptomatic individuals over 20 years of age with a QTc interval < 500 msec seem to be at low risk (see also case III-6). | ||
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#Zareba pmid=9753711 | #Zareba pmid=9753711 | ||
#Priori pmid=9927399 | #Priori pmid=9927399 | ||
# | #Vincent2 pmid=1872278 | ||
#Moretti Moretti P; Calcaterra G, Napolitano C, et al. High prevalence of concealed long QT syndrome among carriers of KVLQT1 defects. Circulation 2001; 201 (Suppl): II-584 (abstract). | #Moretti Moretti P; Calcaterra G, Napolitano C, et al. High prevalence of concealed long QT syndrome among carriers of KVLQT1 defects. Circulation 2001; 201 (Suppl): II-584 (abstract). | ||
#Schwartz Schwartz PJ, Priori SG, Spazzolini C, et al. Genotype-phenotype correlation in the long-QT syndrome. Gene-specific triggers for life-treating arrhythmias. Circulation 2001; 103: 89-95. | #Schwartz Schwartz PJ, Priori SG, Spazzolini C, et al. Genotype-phenotype correlation in the long-QT syndrome. Gene-specific triggers for life-treating arrhythmias. Circulation 2001; 103: 89-95. | ||