Diagnosis of congenital long QT interval syndrome in a 16-year old girl

The article presents a clinical case of a 16-year-old girl with clinical manifestations of congenital long QT interval syndrome in the form of syncope which were primarily diagnosed as epileptic syndrome for which the patient was taking anticonvulsant drugs having qualities of secondary prolongation of QT interval. At the same time, the data of family anamnesis (sudden death of the mother at a young age) in combination with typical manifestations of disease and electrocardiographic signs (prolonged QT interval measured from the standard electrocardiogram, paroxysms of spindle-shaped ventricular tachycardia accompanied with syncope conditions) made it possible to diagnose congenital long QT interval syndrome and implant an electric cardiac pacemaker.

Long QT interval syndrome

The article provides an analysis of modern literature on the problem of diagnosing the long QT syndrome. The diagnostic criteria of this syndrome, features of rare congenital and acquired forms of the disease are described in the article. Risk factors for the development and diagnostic criteria of this disease are presented.

Polymorphic ventricular tachycardia, ischaemic ventricular fibrillation, and torsade de pointes: importance of the QT and the coupling interval in the differential diagnosis

Aims Distinctive types of polymorphic ventricular tachycardia (VT) respond differently to different forms of therapy. We therefore performed the present study to define the electrocardiographic characteristics of different forms of polymorphic VT. Methods and results We studied 190 patients for whom the onset of 305 polymorphic VT events was available. The study group included 87 patients with coronary artery disease who had spontaneous polymorphic VT triggered by short-coupled extrasystoles in the absence of myocardial ischaemia. This group included 32 patients who had a long QT interval but nevertheless had their polymorphic VT triggered by ectopic beats with short coupling interval, a subcategory termed ‘pseudo-torsade de pointes] (TdP). For comparison, we included 50 patients who had ventricular fibrillation (VF) during acute myocardial infarction (‘ischaemic VF’ group) and 53 patients with drug-induced TdP (‘true TdP’ group). The QT of patients with pseudo-TdP was (by definition) longer than that of patients with polymorphic VT and normal QT (QTc 491.4 ± 25.2 ms vs. 447.3 ± 55.6 ms, P < 0.001). However, their QT was significantly shorter than that of patients with true TdP (QTc 564.6 ± 75.6 ms, P < 0.001). Importantly, the coupling interval of the ectopic beat triggering the arrhythmia was just as short during pseudo-TdP as during polymorphic VT with normal QT (359.1 ± 38.1 ms vs. 356.6 ± 39.4 ms, P = 0.467) but was much shorter than during true TdP (581.2 ± 95.3 ms, P < 0.001). Conclusions The coupling interval helps discriminate between polymorphic VT that occurs despite a long QT interval (pseudo-TdP) and polymorphic arrhythmias striking because of a long QT (true TdP).

Drug-induced long qt syndrome

In this review drug-induced long QT interval syndrome is described. The authors discuss approaches for the prevention, diagnosis, and treatment of this potentially fatal complication.

Licorice induced pseudohyperaldosteronism, severe hypertension, and long QT

Summary Excessive intake of licorice may cause pseudohyperaldosteronism which, in turn, may lead to hypertension and hypokalemia. Severe hypokalemia may lead to electrocardiogram (ECG) changes including long QT interval potentially progressing into malignant arrhythmias. Here we present a 43-year-old woman admitted to the hospital with chest pain and a stinging sensation in the upper extremities. Her peak blood pressure was 177/98 mmHg and the blood test revealed low plasma potassium of 1.9 mmol/L. The ECG revealed flattened T-waves and long QT interval. Prior to admission, the patient had increased licorice ingestion to a total of some 70 g daily. The licorice intake was stopped and potassium was administrated orally and intravenously. Plasma potassium normalized and the ECG changes remitted. To our knowledge a few other cases of licorice-induced pseudohyperaldosteronism and long QT interval have previously been reported. This underlines the importance of quantifying licorice intake in younger people with unexplained high blood pressure and low potassium. Learning points: Even small amounts of licorice daily may increase the risk of developing hypertension; therefore, licorice should be asked for specifically. Even though licorice intake is very easy to cover in the patient’s history, it is often missed. Excessive licorice intake may course severe hypokalemia causing long QT interval in the ECG recording, potentially progressing into arrhythmias and even cardiac arrest/sudden death. Hypokalemia <3 mmol/L and present ECG changes should be treated with potassium intravenously. Licorice-induced hypertension may be associated with syndrome of apparent mineralocorticoid excess (SAME). Plasma renin and aldosterone are both low at diagnosis and normalize when licorice is stopped.

P6583Prevalence of long QT interval in thailand and its association with all cause and cardiovascular mortality from a long-term cohort study

Background Long QT interval elevates risks of life-threatening arrhythmias, cardiovascular mortality and all-cause mortality. The prevalence of prolonged QTc among Caucasians is approximately 8.7%. In Thai population, the prevalence and prognosis of prolonged QTc remain unexplored. Objectives 1. To identify the prevalence of long QT interval in the Thai population without prior cardiovascular disease. 2. To evaluate the association between long QT interval and long-term cardiovascular (CV) event and all-cause mortality. Materials and methods A total of 2756 participants from the Electricity Generating Authority of Thailand (EGAT) study from 1997 to 2015 were studied. Among those, 2456 participants had completed EKGs and were included into the final analysis. The long QT interval was defined as QTc longer than 450 milliseconds (ms) in male and 460 ms in female respectively. Mortality endpoints included CV event and all-cause mortality were collected. Multivariable cox-proportional hazard model adjusted for all major CV risk factors was used to determine the association between prolonged QTc and outcomes. Results The majority of the population are male (N=1941, 79%). The mean QT interval calculated by Bazett's formula is 424±28.27 ms. Prolonged QTc was observed 12.5% in male and 17.7% in female. There were 509 (20.7%) deaths during the follow-up period. After 18 years of follow up, 10.5% of the prolonged QTc group had cardiovascular events, compared with 6.8% in the normal QTc group (P=0.09). All-cause mortality occurred in 30% of the prolonged QTc group and 19.3% in the normal QTc group (adjusted HR 1.33, 95% CI 1.05–1.68, P=0.018). After dividing QTc into deciles, the lowest mortality was observed in the 3rd to 7th deciles (17.6%, 19.7%, 16.3%, 23.2% and 18.9% respectively) and the highest mortality was observed in the 2nd deciles (22.09%) and the 8th to 10th deciles (22%, 27.15% and 28.38% respectively). Hazard function of prolonged QTc Conclusion(s) 1. In this worker cohort from Thailand, prolonged QTc was observed in 14% of the population. 2. During 18 years follow up, prolongation of QT interval is an independent risk factor for all-cause mortalities but not cardiovascular mortality. 3. There was a J-curve effect in association between the duration of QT interval and all-cause mortality.