Head-up tilt test induced shortened QT interval:a case report and literature review / 临床儿科杂志

Objective To explore the cause of secondary QT interval shortening. Method The data of a child with vasovagal syncope and cardiac depression in whom shortened QT interval was induced in head-up tilt test (HUTT) was analyzed retrospectively, and the related literatures were reviewed. Result A 12-year-old boy visited for fainting when brushing his teeth in the morning. ECG showed sinus bradycardia, heart rate at 55 times /min and normal QT and QTc interval. Dynamic electrocardiogram showed sinus rhythm, mean heart rate at 70 times/min, atrial anterior contraction 3 times, normal mean QT and mean QTc. UCG showed approximately normal heart structure and the left ventricular systolic function. There was no abnormality in EEG and cranial CT. His fasting blood glucose was 5.2 mmol/L. The basal tilt test was positive with vasovagal syncope and cardiac depression. During the tilt table test, Holter monitoring showed that sinus arrest occurred in the child when upright tilt for16 min, and then fainted. Time of sinus arrest was 2.9 s and 11.4 s, respectively, and artificial chest compressions were performed. The QT interval was shortened (QT=330 ms), and so was QTc interval (QTc=320 ms). The ratio of QT/QTp was 78% (the lower limit of normal QT interval was 88% of QTp) before sinus arrest occurred. Conclusion Increased vagal tone may induce QT interval shortening.

Síndrome de QT corto / Short QT syndrome

El síndrome de QT corto es una canalopatía hereditaria caracterizada por un anormal acortamiento del intervalo QT (IQT), por un riesgo incrementado para el desarrollo de fibrilación auricular y/o arritmias ventriculares malignas y por la ausencia de cardiopatía estructural. Es una enfermedad heterogénea y se han identificado mutaciones en los genes codificadores de los canales de potasio y de calcio. Un incremento en las corrientes neta de salida de potasio o una disminución en al entrada de calcio favorecen el acortamiento heterogéneo de la repolarización ventricular. La marcada abreviación de la longitud de onda del circuito es un factor arritmogénico adicional. El curso clínico oscila desde formas asintomáticas hasta fibrilación auricular paroxística o permanente, síncope, arritmias ventriculares y muerte súbita. El electrocardiograma muestra IQT 220-360 ms, ondas T altas y puntiagudas, prolongación del intervalo pico-final de la onda T e IQT rígido. Es poco frecuente, pero importante por el riesgo elevado de muerte súbita, que en ocasiones puede ser el debut. Puede presentarse solapado al síndrome de Brugada y a la repolarización precoz. El diagnóstico precisa excluir las causas secundarias que acortan el IQT y la no identificación de una mutación no lo excluye. La estimulación eléctrica programada tiene pobre valor diagnóstico y pronóstico. En los sujetos con muerte súbita abortada o con arritmias ventriculares con compromiso hemodinámica, el desfibrilador es la terapéutica de elección. La quinidina es una opción terapéutica alternativa

The short QT syndrome is an inherited channelopathy characterized by an abnormal shortening of the QT interval (QTI), an increased risk of developing atrial fibrillation and/or malignant ventricular arrhythmias, and the absence of structural heart disease. It is a heterogeneous disease and mutations have been identified in the genes encoding potassium and calcium channels. An increase in potassium net efflux or a decrease in calcium influx facilitate the heterogeneous shortening of ventricular repolarization. A marked shortening of the wavelength of the circuit is an additional arrhythmogenic factor. The clinical course ranges from asymptomatic forms to paroxysmal or permanent atrial fibrillation, syncope, ventricular arrhythmias and sudden death. The ECG shows QTI 220-360 ms, high and sharp T waves, prolongation of the final peak interval of the T wave, and QTI drive. It is a rare disease whose importance lies in the high risk of sudden death, which may sometimes be its debut. It may overlap Brugada syndrome and early repolarization. Diagnosis requires excluding secondary causes of QTI shortening. Failure to identify a mutation does not exclude it. Programmed electrical stimulation has a low diagnostic and prognostic value. Defibrillation is the therapy of choice for patients with aborted sudden death or ventricular arrhythmias with hemodynamic compromise. Quinidine is an alternative therapeutic option

Intervalo QT corto intermitente en un paciente con muerte súbita cardiaca / Intermittent short QT interval in a patient with sudden cardiac death

Se presenta el caso de un hombre de 21 años de edad, sin cardiopatía estructural demostrable por los métodos convencionales, reanimado de un episodio de muerte súbita cardiaca. Su historia familiar incluye dos hermanos muertos súbitamente en el primer año de vida. El paciente tuvo diez episodios de taquicardia ventricular (varios de ellos registrados), uno de ellos lo llevó al evento de muerte del cual fue reanimado. Las anormalidades electrocardiográficas fueron un intervalo QT corto intermitente (280 ms), un QT corregido de 320 ms y un segmento ST corto. Con posterioridad el intervalo QT retornó a cifras normales (360 ms o más); ocasionalmente midió 335 ms (no tan corto como el inicial). El estudio electrofisiológico fue normal (intervalos AH y HV, períodos refractarios, no inducibilidad de la arritmia). El paciente rechazó la opción de cardioversor desfibrilador automático implantable y recibe amiodarona hasta la actualidad (200 mg/día), no ha repetido la arritmia en cuatro años. Los electrocardiogramas seriados son muy importantes para identificar pacientes con intervalo QT corto intermitente. El acortamiento del intervalo onda J-T pico es relevante. La arritmia puede ser fibrilación o taquicardia ventriculares.

This paper presents a 21 years-old-male without structural heart disease who was reanimated from a sudden cardiac death event. His familial history included two siblings suddenly dead in their first year of life. The patient had 10 episodes of ventricular tachycardia (some of them were registered). Electrocardiographically abnormalities were an intermittent short QT interval (280 ms), short QTc (320 ms) and a short ST segment. QT interval subsequently returned to a normal range (360 ms or more), while occasionally a length of 335 ms was recorded. The electrophysiological study findings (AH and HV intervals, refractory periods) were normal. The patient refused the implantable cardioverter defibrillator and he is receiving oral amiodarone (200 mg/day). The evolution has been satisfactory along four years. Sequential electrocardiograms are very important to identify patients with an intermittent short QT interval. Shortening of the interval J wave-Tpeak is also relevant. Related arrhythmias could be ventricular tachycardia or fibrillation.