Grapefruit juice prolongs the QT interval of healthy volunteers and patients with long QT syndrome.

BACKGROUND: The list of medications linked to drug-induced long QT syndrome (LQTS) is diverse. It is possible that food products too have QT-prolonging potential. OBJECTIVE: We tested the effects of grapefruit juice on the QT interval with the methodology used by the pharmaceutical industry to test new drugs. METHODS: This was an open-label, randomized, crossover study with blinded outcome evaluation, a thorough QT study of grapefruit juice performed according to the Guidelines for the Clinical Evaluation of QT/QTc for Non-antiarrhythmic Drugs. Thirty healthy volunteers and 10 patients with congenital LQTS were studied. Healthy volunteers drank 2 L of grapefruit juice (in divided doses), or received 400 mg oral moxifloxacin, in a randomized crossover study. Patients with LQTS were tested with only grapefruit. Repeated baseline, off-drug, and on-drug (grapefruit or moxifloxacin) electrocardiograms were scanned and coded. QT measurements were done with electronic calipers. RESULTS: In comparison to off-drug electrocardiograms, grapefruit juice led to significant rate-corrected QT (QTc) prolongation. The absolute net QTc prolongation from grapefruit was 14.0 ms (95% confidence interval 6.2-21.7 ms; P < .001). The QT-prolonging effects of grapefruit in healthy volunteers were comparable with those of moxifloxacin. The QT-prolonging effects of grapefruit juice were greater in female patients and particularly marked in patients with LQTS (net QTc prolongation 21.8 ms; 95% confidence interval 3.4-35.3 ms; P = .034). CONCLUSION: Grapefruit juice, at doses tested, prolongs the QT interval. The effect is significant in healthy volunteers, greater in female patients, and more so in patients with LQTS.

[Prevalence and implicated risk factors associated with the exteriorization of cardiac pacemakers: 5 year follow-up]. / Factores asociados e implicados en la exteriorización de marcapasos definitivo, seguimiento a cinco años.

BACKGROUND: Infection is the most common complication related to permanent pacemaker implantation. The objetive of this study is to establish the prevalence and determine the frequency of risk factors associated with exteriorization of cardiac pacemakers at the Department of Cardiac Electrophysiology at the UMAE Hospital de Especialidades "Dr. Antonio Fraga Mouret" Centro Médico Nacional La Raza, Instituto Mexicano del Seguro Social. METHODS: A descriptive cross-sectional study from September 2005 to September 2010, where, for the analysis of the risk factors we selected cases and controls by age, sex and the diagnosis of Diabetes, or not. Was calculated measures of central tendency (mean, median and mode) and chi-squared, Fisher exact test and exact odds ratio. RESULTS: 3192 cardiac pacemakers were implanted, identifying 83 exteriorization cases, where 46 of them were selected for cases and controls, and the mean age was 71 years. CONCLUSIONS: Our prevalence of exteriorization of cardiac pacemakers is 2.6 %, these results are similar to previously published studies. None of the risk factors described are present as a cause in our population. The surgical technique used may be an important risk factor, so further studies analysing all techniques are needed.

Introducción: el objetivo de este estudio es establecer la prevalencia y determinar la frecuencia de factores de riesgo de exteriorización de marcapasos definitivos (MPD), en el departamento de Electrofisiología Cardiaca de la UMAE Hospital de Especialidades "Dr. Antonio Fraga Mouret" del Centro Médico Nacional La Raza del Instituto Mexicano del Seguro Social.Métodos: se llevó a cabo un estudio transversal, descriptivo del periodo: septiembre del 2005 a septiembre del 2010, para el análisis de los factores se manejó como casos y controles; se eligieron emparejándose por edad, sexo y presencia, o no, de factores de riesgo. Se realizó el cálculo de medidas de tendencia central (media, mediana y moda), así como pruebas de chi cuadrada, test de Fisher y razón de momios.Resultados: se implantaron 3192 MPD, identificando 83 casos de exteriorizaciones, seleccionando 43 casos para casos y controles, la edad promedio fue de 71 años. Ninguno de los factores de riesgo ni el tipo de técnica quirúrgica presentó significancia estadística.Conclusiones: nuestra prevalencia de exteriorizaciones es del 2.6 %, valores muy similares a los reportes publicados. Ninguno de los factores de riesgo descritos se encuentra presente como causa de exteriorización en nuestra población. El análisis de la técnica quirúrgica utilizada puede ser un factor importante, por lo que se necesitan estudios posteriores.

Localización del electrodo de marcapasos definitivo en el tracto de salida del ventrículo derecho mediante tomografía axial computarizada / Determinating the location of the permanent pacemaker lead in the right ventricle outflow tract by computed tomography

Introducción: Precisar la ubicación del electrodo de marcapasos en el tracto de salida del ventrículo derecho (TSVD) es difícil mediante las técnicas convencionales (fluoroscopia y electrocardiografía). La tomografía permite determinar de forma tridimensional la relación del electrodo en el TSVD. Objetivo: Determinar la localización del electrodo de marcapasos mediante la tomografía axial computarizada y comparar los resultados con la localización electrocardiográfica y fluoroscópica. Material y métodos: Se incluyeron 36 pacientes portadores de marcapasos definitivo VVI con el electrodo localizado en el TSVD, a quienes se les tomó un electrocardiograma de 12 derivaciones, proyecciones fluoroscópicas convencionales y tomografía multicorte para determinar la posición del electrodo en el TSVD. Resultados: Mediante el electrocardiograma se localizó el electrodo septal en 58.3% y en pared libre en 41.7%. Por fluoroscopia en oblicua anterior izquierda (OAI) a 35° se localizó el electrodo en pared anterior 5.6%, en pared libre en 38.9% y septal en 55.6%; en OAI a 45° en pared anterior en 2.8%, en pared libre 44.4% y septal en 52.8%. Mediante tomografía se documentó la posición anterior del electrodo en 39%, pared libre en 48% y septal en 13%. El coeficiente Kappa de las 3 pruebas mostró una concordancia muy baja. Conclusión: La tomografía es un mejor método para determinar la posición del electrodo en TSVD comparado contra la fluoroscopia y el electrocardiograma.

Introduction: Determination of the location of the lead of the permanent pacemaker in the right ventricle outflow tract (RVOT) it's difficult with the conventional techniques (fluoroscopic images and electrocardiography). The computed tomography (CT) allows to determinate in three dimensions the relation between the lead and the RVOT. Objective: Determine the location of the electrode lead by computed tomography and compare the results with electrocardiographic and fluoroscopy images localization. Material and methods: 36 patients were included with VVI permanent pacemaker with the lead in the RVOT. A 12-lead electrocardiogram, fluoroscopy images and CT were performed to determine the position of the lead in the RVOT. Results: By electrocardiogram, we located the lead in septal wall 58.3% and free wall 41.7%. By fluoroscopy images in left anterior oblique (LAO) 35° the lead was located on the anterior wall 5.6%, free wall 38.9% and septal 55.6%; in LAO 45° anterior wall 2.8%, free wall 44.4% and septal 52.8%. By Tomography the lead was positioned on anterior wall in 39%, free wall 48% and septal 13%. The Kappa coefficient of the 3 tests showed very low concordance. Conclusion: CT is a better method for determining the position of the lead on the RVOT compared to fluoroscopy images an electrocardiogram.