Electrocardiographic Markers of Appropriate Implantable Cardioverter-Defibrillator Therapy in Young People with Congenital Heart Diseases.

Implantable cardioverter-defibrillators (ICDs) are increasingly utilized in patients with congenital heart disease (CHD). Prediction of the occurrence of shocks is important if improved patient selection is desired. The electrocardiogram (ECG) has been the first-line tool predicting the risk of sudden death, but data in CHD patients are lacking. We aim to evaluate the predictive value of electrocardiographic markers of appropriate therapy of ICD in young people with CHD. We conducted a prospective, longitudinal study, in twenty-six CHD patients (mean age 24.7 ± 5.3 years) who underwent first ICD implantation. Forty-two age- and diagnosis-matched controls were recruited. Twelve-lead ECG and 24 h Holter analysis were performed during a mean follow-up of 38.9 months. Data included heart rate, heart rate variability, QRS duration (QRSd), QTc interval and its dispersion, Tpeak-Tend (Tp-Te) interval and its dispersion, presence of fragmented QRS (fQRS), T wave alternans, atrial arrhythmias, and non-sustained ventricular tachycardia. Implant indication was primary prevention in ten cases (38.5%) and secondary prevention in 16 (61.5%). Overall, 17 subjects (65.3%) received at least one appropriate and effective ICD discharge. fQRS was present in 64.7% of cases with ICD therapy compared with patients without events or controls (p < 0.0001). Tp-e and Tp-e dispersion were significantly prolonged in patients with recurrences (113.5 and 37.2 ms) versus patients without ICD discharge (89.6 and 24.1 ms) or controls (72.4 and 19.3 ms) (p < 0.0001 and p < 0.0001, respectively). On univariate Cox regression analysis QRSd (hazard ratio: 1.19 per ms, p = 0.003), QTc dispersion (hazard ratio: 1.57 per ms, p = 0.002), fQRS (hazard ratio: 3.58 p < 0.0001), Tp-e (hazard ratio: 2.27 per ms, p < 0.0001), and Tp-e dispersion (hazard ratio: 4.15 per ms, p < 0.0001), emerged as strong predictors of outcome. On multivariate Cox analysis fQRS, Tp-e and Tp-e dispersion remained in the model. The presence of fQRS, and both Tp-e and Tp-e dispersion are useful ECG tools in daily clinical practice to identify CHD patients at risk for appropriate ICD therapy.

[Ambulatory electrocardiographic recording (Holter) at the moment of a sudden death event]. / Registro ambulatorio electrocardiográfico Holter al momento de un evento de muerte súbita.

Arrhythmic sudden cardiac death due to electrical causes is an important clinical and public health problem, which is not yet solved. Ventricular fibrillation is the first cause of the event. It does not adjust to a single model, being a family with diverse electrocardiographic patterns that reveal different disorganization degrees. Many of these deaths happen without witness. We present a patient who was being studied after a first medical visit because of a previous syncope with spontaneous recovery, coursing with left bundle branch block. He was not receiving any antiarrhythmic drug and was asymptomatic at the time. He was wearing a long-term ambulatory electrocardiographic recorder (Holter), which became the sole witness of his death that occurred while he was alone at home. The recording revealed various malignant ventricular arrhythmia (torsades des pointes, ventricular flutter, ventricular fibrillation), immediately preceding events were an increased heart rate, extra-systoles, and left bundle branch block. This is the first recording of the whole sequence of malignant ventricular arrhythmias leading to death in a patient wearing a Hotter device obtained by our department, which has collected 750 Hotter ambulatory records per year for more than 20 years. The literature on the subject is reviewed.

Multiple serial ECGs aid with the diagnosis and prognosis of Brugada syndrome.

BACKGROUND: A spontaneous coved-type ST segment elevation in the electrocardiogram (ECG) has long been recognized as a risk stratification tool in patients with Brugada syndrome (BrS). This Type-I ST segment elevation is known to exhibit high dynamicity, fluctuating between coved-type and non-coved ST segment elevation. Our objectives in this study were to: 1) Compare ECG parameters in patients with spontaneous coved-type (Type-I) vs. non-coved-type ST segment ECGs; 2) Determine the variability of these ECG parameters with repeated measurements; and 3) Assess the predictive value of ECG parameters in these two groups during follow-up. METHODS: Forty-two consecutive patients with BrS and implanted ICD were studied between 2000 and 2017. Serial ECGs and clinical characteristics were obtained over a period of 199 months. RESULTS: QT-interval, QTc-interval, QRS duration, Tp-e interval and Tp-e dispersion were all significantly longer in spontaneous Type I vs. non-Type 1 ECGs and all ECG parameters displayed significant variability during serial recording obtained throughout the follow-up period. Patients with a spontaneous Type I ECG during the 114 ±â€¯56 months follow-up period were at a much higher risk for VT/VF than those without a Type I ECG (p = 0.016). Moreover, the risk for development of life-threatening ventricular arrhythmias was directly related to the fraction of ECGs displaying a spontaneous Type I pattern during follow-up. CONCLUSION: Our study illustrates the need for multiple ECGs to aid with both the diagnosis and prognosis of BrS. Serial ECGs can assist with risk stratification based on the fraction of ECGs that display a spontaneous Type-I BrS ECG.

[Non-invasive electrical markers in patients with the Brugada syndrome]. / Marcadores eléctricos no invasores en pacientes con síndrome de Brugada.

Throughout the 13 years of recognizing the Brugada syndrome as a separate entity, there has been a search for invasive and non-invasive markers for detecting risk of life-threatening arrhythmic events, particularly for asymptomatic individuals in whom the first manifestation may be sudden cardiac death. Hence, the preclinical diagnosis is pivotal for adequate and timely preventive measures. The objective of this study was to compare various non-invasive markers to characterize and stratify patients at risk. Late potentials, QT interval, QT dispersion, and heart variability were analyzed over a two-year period, in 20 patients (17 men and 3 women) with the Brugada syndrome (symptomatic and asymptomatic) and compared with 20 normal individuals similar in age and gender (control group). Late potentials were present in 80% of patients versus 5% in the control group (p < 0.0001); all of these with recurrent episodes had late potentials. In conclusion, this is the most important non-invasive marker for risk stratification, recurrences and inducibility of malignant arrhythmias during electrophysiological testing. Markers, invasive and non-invasive, should be considered integrally, for a better diagnostic and prognostic approach to reality.

Monomorphic ventricular tachycardia in patients with Brugada syndrome: A multicenter retrospective study.

BACKGROUND: Isolated cases of monomorphic ventricular tachycardia (MVT) in patients with Brugada syndrome (BrS) have been reported. OBJECTIVE: We aimed to describe the incidence and characteristics of MVT in a cohort of patients with BrS who had received an implantable cardioverter-defibrillator (ICD). METHODS: Data from 834 patients with BrS implanted with an ICD in 15 tertiary hospitals between 1993 and 2014 were included. RESULTS: The mean age of enrolled patients was 45.3 ± 13.9 years; 200 patients (24%) were women. During a mean follow-up of 69.4 ± 54.3 months, 114 patients (13.7%) experienced at least 1 appropriate ICD intervention, with MVT recorded in 35 patients (4.2%) (sensitive to antitachycardia pacing in 15 [42.8%]). Only QRS width was an independent predictor of MVT in the overall population. Specifically, 6 (17.1%) patients presented with right ventricular outflow tract tachycardia (successfully ablated from the endocardium in 4 and epicardial and endocardial ablation in 1), 2 patients with MVT arising from the left ventricle (1 successfully ablated in the supra lateral mitral annulus), and 2 (5.7%) patients with bundle branch reentry ventricular tachycardia. Significant structural heart disease was ruled out by echocardiography and/or cardiac magnetic resonance imaging. CONCLUSION: In this retrospective study, 4.2% of patients with BrS implanted with an ICD presented with MVT confirmed as arising from the right ventricular outflow tract tachycardia in 6, patients with MVT arising from the left ventricle in 2, and patients with bundle branch reentry ventricular tachycardia in 2. Endocardial and/or epicardial ablation was successful in 80% of these cases. These data imply that the occurrence of MVT should not rule out the possibility of BrS. This finding may also be relevant for ICD model selection and programming.

Papel del sistema Purkinje y del tracto de salida del ventrículo derecho en las arritmias ventriculares malignas y la muerte súbita / Role of the Purkinje system and right ventricular outflow tract in malignant ventricular arrhythmias and sudden death

RESUMEN El sistema Purkinje y el tracto de salida del ventrículo derecho tienen un papel trascendente en relación con las arritmias ventriculares malignas (taquicardia y fibrilación ventriculares, torsión de puntas) y con la muerte súbita cardíaca. Se discuten su fisiopatología, participación en el origen (extrasístoles desencadenantes) y mantenimiento de estas arritmias, y las posibilidades ablativas para disminuir las recurrencias y los episodios de tormenta eléctrica. Se expone el diagnóstico diferencial entre variantes benignas y malignas de la taquicardia ventricular relacionada con el tracto de salida del ventrículo derecho y la relación entre factores genéticos, estructurales, electroanatómicos y funcionales (inflamación, fibrosis), con los eventos clínicos y la vulnerabilidad a las arritmias. Se necesita reclasificar algunas de estas enfermedades, vistas ahora en su carácter orgánico-funcional (síndrome de Brugada, por ejemplo), lo cual implica cambios revolucionarios en algunos conceptos clásicos y una nueva visión en cuanto a la estratificación de riesgo y la conducta terapéutica.

ABSTRACT The Purkinje system and the right ventricular outflow tract play a pivotal role in relation to malignant ventricular arrhythmias (ventricular tachycardia and fibrillation, torsades de pointes) and sudden cardiac death. Details such as their pathophysiology, origin involvement (triggering extrasystoles) maintenance of such arrhythmias, and ablative possibilities to reduce recurrences and electrical storm events are discussed herein. The differential diagnosis between benign and malignant ventricular tachycardia related to the right ventricular outflow tract, and the relationship between genetic, structural, electroanatomical and functional factors (inflammation, fibrosis) with clinical events and vulnerability to arrhythmias are presented. Some of these diseases need to be reclassified as they are now seen in their organic-functional character (Brugada syndrome, for example), and this implies radical changes in some classical concepts as well as a new perspective on risk stratification and therapeutic management.

Taquicardia incesante del tracto de salida del ventrículo derecho - ¿Taquimiocardiopatía?: El enigma / Incessant right ventricular outflow tract tachycardia - Tachycardiomyopathy? The enigma

RESUMEN Las taquicardias ventriculares de larga duración o incesantes pueden causar insuficiencia cardíaca, disfunción del ventrículo izquierdo y cardiomiopatía, cuadros que revierten una vez resueltas las arritmias. Se trata de un diagnóstico de exclusión: puede existir una cardiopatía de base que empeora con la taquicardia y debe precisarse si la arritmia lleva a la cardiomiopatía (puede existir un subregistro) o viceversa. Se presenta un paciente con taquicardia incesante del tracto de salida del ventrículo derecho, de larga evolución, con repercusión hemodinámica, cardiomiopatía dilatada y disfunción grave del ventrículo izquierdo, rebelde a fármacos antiarrítmicos y con dos ablaciones fallidas, pendiente de biopsia endomiocárdica y nueva ablación de su taquicardia. Se discuten algunas pistas para diferenciar las arritmias del tracto de salida del ventrículo derecho, en sus variantes benignas (las más frecuentes) y malignas. Algunas pistas para diferenciarlas son: la duración del complejo QRS, el intervalo de acoplamiento de la extrasístole y la frecuencia de la taquicardia.

ABSTRACT Long-lasting or incessant ventricular tachycardias may cause heart failure, left ventricular dysfunction, and cardiomyopathy; conditions that reverse once the arrhythmias have been solved. This is a diagnosis of exclusion: there may be a basic heart disease that worsens with the tachycardia and it must be clarified whether the arrhythmia leads to cardiomyopathy (there may be an underregistration) or vice versa. A patient with incessant right ventricular outflow tract tachycardia, with long evolution, hemodynamic repercussion, dilated cardiomyopathy and severe dysfunction of the left ventricle, refractory to antiarrhythmic drugs and with two failed ablations, pending endomyocardial biopsy and new ablation of his tachycardia is presented. Some clues to differentiate right ventricular outflow tract arrhythmias, in their benign (most frequent) and malignant variants, are discussed. Some clues to differentiate them are: the duration of the QRS complex, the coupling interval of premature contractions and the heart rate of the tachycardia.

T-wave oversensing in patients with Brugada syndrome: true bipolar versus integrated bipolar implantable cardioverter defibrillator leads: multicenter retrospective study.

BACKGROUND: It is thought that dedicated bipolar are more susceptible to T-wave oversensing when compared with integrated bipolar leads. This could be of extreme importance in patients with Brugada syndrome (BrS) because T-wave oversensing in this population is more frequent when compared with other implantable cardioverter defibrillator (ICD) recipients without BrS. We aimed to compare the incidence of T-wave oversensing in patients with BrS according to the type of lead (integrated bipolar versus true/dedicated bipolar). METHODS AND RESULTS: All patients diagnosed with BrS with an ICD implant in 10 tertiary hospitals between 1993 and 2013 were included in the study. A total of 480 patients were included (mean age, 45.6±14 years). During a mean follow-up of 74.9±51.7 months (median, 69; range, 2-236), 28 patients had T-wave oversensing (5.8%), leading to inappropriate shock in 18 (3.8%). All these events occurred in patients with true bipolar ICD leads (P=0.01) and in 2 patients it was solved instantaneously by changing the configuration from a dedicated to an integrated bipolar sensing configuration. In the stepwise multivariate models, only integrated bipolar ICD leads (hazard ratio, 0.34; 95% confidence interval, 0.171-0.675; P=0.002) was independent predictor of non-T-wave oversensing. CONCLUSIONS: T-wave oversensing is a potential reason of inappropriate shocks in patients with BrS receiving ICDs. In the vast majority it can be solved by reprogramming. However, in some patients it still requires invasive intervention. Importantly, incidence is significantly lower using an integrated bipolar lead system when compared with a dedicated bipolar lead system and hence the latter should be routinely used in BrS cases.

[Brugada's syndrome: experience in Cuba in 2001]. / Síndrome de Brugada: experiencia Cubana 2001.

The Brugada syndrome is the most frequent electrical cause of sudden death in patients with structurally normal heart. It is characterized by ST segment elevation in V1-V3 leads, pseudo right bundle branch block and proneness for episodes of life-threatening ventricular cardiac arrhythmias. The aim of this study was to characterize patients with Brugada syndrome identified in Cuba between 1995 and 2001. Fourteen patients with these electrical signs (13 male and 1 female, mean age 42.8) were studied. Seven of them were symptomatic and seven were not. The pharmacological test with sodium channel blockers was very useful (it was positive for all the patients). HV interval was normal. Programmed ventricular stimulation was performed. Ventricular arrhythmia was inducible in 3 symptomatic patients and 2 asymptomatic. All the symptomatic patients and those asymptomatic in whom ventricular arrhythmia was inducible received automatic defibrillators. One clinical recurrence of ventricular arrhythmias was observed. Antiarrhythmic drugs were only used rarely. Clinical history and electrocardiographic tracings were very important to diagnose this syndrome. There were light, transient or masked electrical signs. The treatment of choice is the implantable cardioverter-defibrillator.

Terapia de resincronización cardíaca: Índice del QRS como predictor de respuesta / Cardiac resynchronization therapy: QRS index as a response predictor

RESUMEN Introducción: La terapia de resincronización cardíaca (TRC) es indicación en la insuficiencia cardíaca con QRS ancho y disminución grave de la fracción de eyección del ventrículo izquierdo. Objetivos: Definir los predictores de respuesta favorable a la TRC. Método: Se realizó un estudio observacional, descriptivo, retrospectivo, para evaluar el índice del QRS (diferencia entre anchura del QRS antes y después del implante, dividido entre su valor antes del implante, multiplicado por 100) como predictor de respuesta favorable a la TRC. Se realizaron electrocardiogramas antes del procedimiento, a los 6 y a los 12 meses del implante. Las mediciones se hicieron por dos observadores independientes, la primera digital en el monitor del salón de operaciones y el resto manual. Resultados: Se incluyeron 91 pacientes (edad media 61,2 años, 76% hombres), QRS mayor de 120 ms y fracción de eyección menor de 35%. Se obtuvo respuesta favorable en un 59%. No hubo diferencias significativas pre-implante en la duración del QRS entre respondedores y no respondedores (151,3 ms vs 151,34 ms, p=0,98), pero sí post-implante (100 vs 115 ms, p<0,0001), así como en el porcentaje de disminución del QRS (33,2% vs 24,3%, p<0,0001). La curva ROC mostró que un valor de corte del índice de QRS del 30% fue sensible (62%) y específico (75%), para predecir respuesta favorable. Conclusiones: La disminución de la anchura del QRS luego del implante de la TRC se relaciona con una respuesta favorable a la misma.

ABSTRACT Introduction: Cardiac resynchronization therapy (CRT) is an indication in heart failure with wide QRS and severely reduced left ventricular ejection fraction. Objectives: To define the response predictors favorable to CRT. Method: An observational, descriptive, retrospective study was conducted to evaluate the QRS index (difference between the QRS width before and after implantation, divided by its value before implantation, multiplied by 100) as a predictor of favorable response to CRT. Electrocardiograms were performed before the procedure, at 6 and 12 months after implantation. The measurements were made by two independent observers, the first digital on the operating room monitor and the rest manual. Results: A total of 91 patients (mean age 61.2 years, 76% men) were included, with QRS wider than 120 ms and ejection fraction less than 35%. A favorable response was obtained in 59%. There were no significant pre-implant differences in the QRS duration between responders and non-responders (151.3 ms vs. 151.34 ms, p=0.98), but there were differences post-implant (100 vs. 115 ms, p<0.0001), as well as in the QRS percentage of decrease (33.2% vs. 24.3%, p<0.0001). The ROC curve showed that a cut-off value of the QRS index of 30% was sensitive (62%) and specific (75%) in order to predict a favorable response. Conclusions: The decrease in the QRS width after the CRT implant is related to a favorable response to it.

Prolongación de la despolarización y la repolarización ventriculares en pacientes operados de cirugía cardíaca

Introducción: La cirugía cardíaca establece una serie de elementos mecánicos y químicos de agresión al musculo cardíaco, que pudiese verse reflejada en el electrocardiograma. Objetivo: Evaluar si las medidas electrocardiográficas que reflejan la despolarización y la repolarización ventriculares se prolongan posterior a la cirugía cardíaca. Método: Se estudiaron 51 pacientes con cirugía cardíaca, a quienes se les realizó electrocardiograma antes y después del procedimiento. Se comparó, mediante la prueba T, la diferencia de los valores de intervalo QT, QTc, dispersión del QT, intervalo TPICO-TFINAL (TP-F), dispersión del TP-F y duración del QRS, antes y después de la intervención quirúrgica. Resultados: Los valores del QTc, dispersión del QT, TP-F, dispersión del TP-F y duración del QRS fueron significativamente mayores (p<0,006) en el electrocardiograma posterior a la cirugía. El intervalo QT sin corregir fue mayor en el electrocardiograma posquirúrgico, sin diferencia estadísticamente significativa (p=0,49). Conclusiones: La agresión al músculo cardíaco durante la cirugía cardíaca modifica la actividad eléctrica ventricular y se constata en la prolongación significativa de las mediciones que reflejan la despolarización y repolarización ventriculares. Estas variables pudieran utilizarse en futuros estudios como predictores de eventos adversos de este procedimiento.

Introduction: Cardiac surgery involves a series of aggressive mechanical and chemical elements that affect the cardiac muscle; which may be shown by the electrocardiogram. Objective: To evaluate whether electrocardiographic measurements reflecting ventricular depolarization and repolarization are prolonged after cardiac surgery. Method: We studied 51 patients with cardiac surgery who underwent an electrocardiogram before and after surgery. The difference between QT, QTc, QT dispersion, TPEAK-TEND interval (TP-TE), TP-TE dispersion and QRS duration, before and after surgery was compared using the T test. Results: Electrocardiogram after surgery showed significantly higher QTc values, QT dispersion, TP-TE, TP-TE dispersion and QRS duration (p<0.006). The uncorrected QT interval was greater in the postoperative electrocardiogram, without statistically significant difference (p=0.49). Conclusions: Myocardial aggression during cardiac surgery modifies the ventricular electrical activity and is verified by the significantly prolonged depolarization and repolarization measurements. These variables could be used in future studies as predictors of adverse events in this procedure.

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

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.

Onda J transitoria después de reanimación por una fibrilación ventricular / Transient J Wave after Resuscitation from Ventricular Fibrillation

La repolarización precoz es un hallazgo electrocardiográfico benigno común, en ocasiones asociado con fibrilación ventricular idiopática. En esta presentación se describe el caso de una mujer de 38 años sin cardiopatía estructural ni historia familiar de muerte súbita cardíaca, reanimada de un episodio de fibrilación ventricular. Una semana antes tuvo extrasístoles ventriculares. Se detectaron la elevación del punto J, después del choque eléctrico, que disminuyó hasta desaparecer, y un intervalo QT corto transitorio. Se implantó un cardioversor-desfibrilador automático y se administró quinidina. Su evolución ha sido satisfactoria, sin recidivas. La repolarización precoz podría ser un signo, un síndrome o un marcador asociado con la fibrilación ventricular idiopática.

Early repolarization is a common benign electrocardiographic finding, sometimes associated with idiopathic ventricular fibrillation. We present the case of a 38-year-old woman, without structural heart disease and no family history of sudden cardiac death, who underwent resuscitation from an episode of ventricular fibrillation. One week before the episode she had ventricular extrasystoles. A transient and prominent J-wave, immediately after defibrillation, which subsequently decreased and disappeared and a transient short QT interval were detected. An automatic cardioverter-defibrillator was implanted and quinidine was administered. Her evolution has been satisfactory with no recurrences. Early repolarization could be a sign, a syndrome, or a marker associated to idiopathic ventricular fibrillation.

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.