RESUMEN
Atrial tachycardias (ATs) are relatively uncommon and their mechanisms include reentry or may be focal. The characteristics and radiofrequency (RF) ablation of adenosine-sensitive AT arising near the apex of Koch's triangle have been reported. We report a case of successful RF ablation of this tachycardia by using a retrograde transaortic/transmitral approach. An electrophysiological study performed during sinus rhythm showed continuous anterograde atrioventricular nodal and no ventriculoatrial conduction. The tachycardia could be induced and terminated by atrial extrastimulation and rapid atrial pacing. Although inverse resetting response pattern was observed, tachycardia termination by intravenous low-dose adenosine was rather suggestive of triggered activity as the mechanism. The earliest atrial activation was recorded in the His-bundle region. After ineffective right-sided attempts and failure to find earlier atrial activity during mapping the noncoronary sinus of Valsalva, this tachycardia was successfully ablated from the left atrial septum by using a retrograde transaortic/transmitral approach. This report demonstrates the feasibility of a novel retrograde left atrial approach for RF ablation of adenosine-sensitive AT originating from the apex of Koch's triangle.
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PURPOSE: To investigate whether the presence of endocardial leads has an impact on image quality in coronary computed tomography angiography (CCTA), when current technique is employed using a 320-row computed tomography and iterative reconstruction. MATERIALS AND METHODS: CCTA was performed in 1641 patients, from these we identified 51 patients (study group) with endocardial leads and 51 matched partners (control group) without endocardial leads. Noise was determined in the ascending aorta and the left ventricle; signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were determined in the left and right coronary artery. Subjective image quality was rated separately for the 15 segments of the coronary arteries by 2 radiologists. RESULTS: Current CCTA technique still shows slight impairment of objective image quality in patients with endocardial leads with inferior SNR in the aorta (median 15.04 versus 16.6; pâ¯=â¯0.004) and inferior SNR in the left/right coronary artery (median 15.3/13.81 versus 16.1/15.41; pâ¯=â¯0.013/0.002). CNR of the left/right coronary artery was also inferior (median 17.4/16.46 versus 19.26/19.24; pâ¯=â¯0.002/<0.001). The subjective image quality was rated significantly inferior only in segment 8 (pâ¯=â¯0.001) compared to the control group. Artifacts by ventricular leads were found in 65% of the patients in segment 8 with non-diagnostic rating in 9 cases (18%). Atrial leads resulted in artifacts predominantly in segment 1 (45%) with non-diagnostic rating in only 2 cases (4%). CONCLUSION: CCTA is feasible with slight restrictions for patients in the presence of implanted cardiac devices when current technique is used.
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Artefactos , Angiografía por Tomografía Computarizada/métodos , Angiografía Coronaria/métodos , Vasos Coronarios/diagnóstico por imagen , Marcapaso Artificial , Interpretación de Imagen Radiográfica Asistida por Computador/métodos , Relación Señal-Ruido , Anciano , Endocardio , Femenino , Humanos , Masculino , Persona de Mediana Edad , Dosis de Radiación , Cintigrafía , Tomografía Computarizada por Rayos X/métodosRESUMEN
INTRODUCTION: Decremental conduction in short anterograde atrioventricular accessory pathways (AV-APs) is rare. CASE PRESENTATION: We report on two cases with radiofrequency (RF) ablation of anterograde fast non-decremental AV-AP conduction. In Case 1, electrophysiological testing revealed fast non-decremental conduction over an anterograde short right posteroseptal AV-AP. During ablation, latent pre-excitation due to anterograde adenosine-sensitive slow decremental conduction over the same AV-AP manifested after eliminating its non-decremental conduction. Complete abolition of AP conduction was achieved by additional ablation. In Case 2, overt pre-excitation disappeared after the first ablation session for an anterograde short non-decremental right mid-septal AV-AP. However, latent pre-excitation due to markedly decremental conduction over the same AV-AP unmasked by intravenous adenosine and atrial pacing manoeuvers could be eliminated in a second session. DISCUSSION: This report describes unusual anterograde short non-decremental AV-APs, developing markedly slow adenosine-sensitive decremental conduction during ablation. Such AV-AP conduction properties due to RF injury may be overlooked and mask incomplete ablation and point-out careful testing including stimulation techniques and low and higher dose adenosine administration post-ablation.
RESUMEN
Most tachycardias in the pulmonary venous atrium are inaccessible by direct means and require either a retrograde approach or a transseptal approach for ablation. We present a case in which successful radiofrequency ablation of common atrioventricular nodal reentrant tachycardia was accomplished via a retrograde transaortic approach guided by nonfluoroscopic mapping with use of the NavX™ mapping system. The patient was a 49-year-old woman who at the age of 4 years had undergone Mustard repair for complete dextrotransposition of the great arteries. Three-dimensional reconstructions of the ascending aorta, right ventricle, systemic venous atrium, left ventricle, and superior vena cava-inferior vena cava baffle complex were created, and the left-sided His bundle was marked. After a failed attempt at ablation from the systemic venous side, we eliminated the atrioventricular nodal reentrant tachycardia by ablation from the pulmonary venous side. This case is, to our knowledge, the first report of successful radiofrequency ablation of common atrioventricular nodal reentrant tachycardia after Mustard repair for this congenital cardiac malformation in which ablation was guided by 3-dimensional nonfluoroscopic imaging. This imaging technique enabled accurate anatomic location of the ablation catheters in relation to the His bundle marked from the systemic venous side.
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Operación de Switch Arterial/efectos adversos , Ablación por Catéter , Técnicas Electrofisiológicas Cardíacas , Venas Pulmonares/cirugía , Taquicardia por Reentrada en el Nodo Atrioventricular/cirugía , Transposición de los Grandes Vasos/cirugía , Potenciales de Acción , Electrocardiografía , Femenino , Frecuencia Cardíaca , Humanos , Persona de Mediana Edad , Valor Predictivo de las Pruebas , Venas Pulmonares/fisiopatología , Taquicardia por Reentrada en el Nodo Atrioventricular/diagnóstico , Taquicardia por Reentrada en el Nodo Atrioventricular/etiología , Taquicardia por Reentrada en el Nodo Atrioventricular/fisiopatología , Transposición de los Grandes Vasos/diagnóstico , Resultado del TratamientoRESUMEN
We present the first description of successful radiofrequency (RF) ablation of a bidirectional atrioventricular accessory pathway (AP) guided by nonfluoroscopic mapping with use of three-dimensional magnetic resonance imaging integrated into the Nav-X system (MRI/Nav-X fusion) in a 13-year-old boy with remote surgical palliation for cyanotic criss-cross heart with atrioventricular discordance, double-outlet right ventricle, and a large ventricular septal defect. Due to complex anatomy, a unique finding was that the eliminated left lateral AP electrically connected the left atrium to the antero-superior morphologic right ventricle prior to ablation.
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Fascículo Atrioventricular Accesorio/cirugía , Mapeo del Potencial de Superficie Corporal/métodos , Ablación por Catéter/métodos , Corazón con Ventrículos Entrecruzados/cirugía , Imagen por Resonancia Magnética/métodos , Cirugía Asistida por Computador/métodos , Fascículo Atrioventricular Accesorio/diagnóstico , Fascículo Atrioventricular Accesorio/etiología , Adolescente , Corazón con Ventrículos Entrecruzados/complicaciones , Corazón con Ventrículos Entrecruzados/diagnóstico , Humanos , Masculino , Imagen Multimodal/métodos , Resultado del TratamientoRESUMEN
BACKGROUND AND PURPOSE: Vascular complications following transradial coronary angiography and coronary intervention could severely compromise perfusion of the hand. Drastic complications after cannulation of the radial artery (ischemia of the hand with occlusion of the digital arteries) are published only in brief reports. This study investigates whether percutaneous transradial artery coronary angiography/intervention results in vascular complications. PATIENTS AND METHODS: 93 patients were consecutively studied over a 4-month period. The following data were recorded before and after coronary angiography and/or intervention: diameter of the radial artery, blood volume, flow velocity, and occlusion pressure. Graduation of the stenosis after intervention was done according to the principle of the peak velocity ratio. RESULTS: A transradial coronary angiography/intervention was performed in 93 patients (75 men, mean age 62.5 years) in case of an unremarkable Allen test. Procedural success rate was 97.2%. The intervention could not be completed successfully in three patients (2.8%). Mean vessel diameter increased from 2.46 +/- 1.7 mm (standard deviation [SD]) before intervention to 2.78 +/- 0.69 mm (SD) after intervention; this increase was statistically significant (p = 0.002). Changes in blood flow, flow velocity and occlusion pressure did not reach significance. Vascular complications were seen in nine of 93 patients (10%) after the procedure. No patient mentioned discomfort. No perfusion deficit of the digital arteries was seen. CONCLUSION: The transradial coronary angiography and intervention is a safe method with a high procedural success rate.
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Angioplastia Coronaria con Balón/efectos adversos , Angiografía Coronaria/efectos adversos , Enfermedad Coronaria/diagnóstico por imagen , Dedos/irrigación sanguínea , Mano/irrigación sanguínea , Isquemia/diagnóstico por imagen , Arteria Radial/lesiones , Anciano , Velocidad del Flujo Sanguíneo/fisiología , Constricción Patológica/diagnóstico por imagen , Enfermedad Coronaria/terapia , Femenino , Estudios de Seguimiento , Humanos , Masculino , Persona de Mediana Edad , Pletismografía de Impedancia , Estudios Prospectivos , Arteria Radial/diagnóstico por imagen , Valores de Referencia , Ultrasonografía Doppler en Color , Resistencia Vascular/fisiologíaRESUMEN
Cardiovascular magnetic resonance (CMR) using contrast enhancement allows exact determination of the site and transmural extent of myocardial infarction (MI). We evaluated whether 12-lead electrocardiography can differentiate transmural from non-transmural MI or determine the site of MI by comparing the findings with those of contrast-enhanced CMR. A total of 27 patients (59.5+/-12.9 years) with a history of MI (6.4+/-2.9 months) underwent CMR (Magnetom, Siemens, Erlangen, Germany). Cine images were acquired in the horizontal and vertical long axes and short axis by TrueFISP. Contrast-enhanced CMR images were acquired in the same axes by segmented FLASH 15 min after administration of gadolinium-DTPA (0.15 mmol/kg). This showed the MI to be transmural in 11 patients and non-transmural in 16. An electrocardiogram (ECG) was recorded in all patients before CMR. T-wave alterations, descending ST-depression, pathological Q-waves and absent R waves were more frequent in non-transmural MI than transmural MI, as defined by contrast-enhanced CMR (p> or =0.618). However, none of the differences were statistically significant. R-wave reduction, q waves and horizontal ST-depression were more frequent in transmural than in non-transmural MI (p> or =0.157). Again, the differences were not significant. The sensitivity of the ECG for MI localization was highest in inferior infarctions (85.71%), the specificity was highest in anterior infarctions (100%), the best positive predictive value (80%) was achieved for anterolateral infarctions, and the best negative predictive value for lateral infarctions (95.83%). Transmural and non-transmural MI cannot be differentiated by ECG. The ECG is most accurate in detecting anterolateral MI.
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Medios de Contraste/farmacología , Electrocardiografía/normas , Imagen por Resonancia Magnética , Infarto del Miocardio/diagnóstico , Gadolinio DTPA/farmacología , Humanos , Aumento de la Imagen , Imagen por Resonancia Magnética/métodosRESUMEN
INTRODUCTION: Cardiovascular magnetic resonance (CMR) allows very accurate, but time-consuming, volume assessment by the short-axis slice summation technique. The single and biplane methods of volume assessment are used less, partly because FLASH cine imaging provides poor blood-myocardium contrast in long-axis views. TrueFISP gives excellent blood-myocardium contrast, even in patients with heart failure. We hypothesized that the single plane and biplane methods of volume assessment in TrueFISP images might provide an acceptable degree of accuracy and be quicker than the short axis method, and that single and biplane left ventricular volume assessment would be more accurate with TrueFISP than with FLASH in patients with impaired ventricular function. METHODS: Short- and long-axis CMR images were obtained by FLASH and TrueFISP with a 1.5-T scanner. We determined the accuracy of both single and biplane long-axis methods for left ventricular volume and ejection fraction (EF) measurements compared with the conventional short-axis method in 10 heart failure patients using both FLASH and TrueFISP and in 9 healthy subjects using TrueFISP. RESULTS: No difference in volumes and EF was found between the single plane method, the biplane method, and the short-axis method using TrueFISP for image acquisition, in both patients and healthy subjects. The same was true of the results obtained by FLASH in the patients with heart failure. CONCLUSIONS: The single and biplane methods, regardless of whether TrueFISP or FLASH is used, are a reasonable and rapid alternative to the conventional short-axis approach for left ventricular volume and EF assessment in patients with heart failure and impaired ventricular function.
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Volumen Cardíaco/fisiología , Insuficiencia Cardíaca/patología , Imagen por Resonancia Cinemagnética/métodos , Volumen Sistólico/fisiología , Disfunción Ventricular Izquierda/patología , Adulto , Anciano , Anciano de 80 o más Años , Circulación Coronaria/fisiología , Femenino , Insuficiencia Cardíaca/fisiopatología , Humanos , Procesamiento de Imagen Asistido por Computador , Masculino , Persona de Mediana Edad , Análisis de Regresión , Reproducibilidad de los Resultados , Disfunción Ventricular Izquierda/fisiopatología , Función Ventricular Izquierda/fisiologíaRESUMEN
BACKGROUND AND PURPOSE: Pharmacological treatment of atrial fibrillation (AF) is limited by induction of malignant ventricular arrhythmias. Developing new drugs, a promising strategy is a more specific treatment of the atria. Muscarinic potassium current (IK[ACh]) is predominantly expressed in supraventricular tissue and mediates the induction of vagus-induced AF. The authors investigated the profile of representative class III drugs in respect to their effect on IK(ACh). METHODS: In rat atrial myocytes, IK(ACh) was activated by acetylcholine (ACh) measured with the whole-cell voltage clamp method. Drugs used: selective IKs blocker chromanole 293B (Cro); IKr blockers sotalol (Sot), dofetilide (Dof), ibutilide (Ibu), and terikalant (Ter). Data are expressed as mean values +/- standard deviation (SD). RESULTS: ACh-induced IK(ACh) density was 73 +/- 9 pA/pF (n= 9). IK(ACh) was almost completely desensitized in the presence of 50 micro M Ter, Ibu, or Dof. IC(50) of IK(ACh) inhibition by the three drugs was 0.9, 2.8, and 4.2 micro M (Dof, Ibu, and Ter, respectively). Receptor-independent GTP-gamma-S-induced IK(ACh) was sensitive to Ter, Ibu, and Dof as well. Sot is known to be a weak inhibitor of IKr. Inhibition of IK(ACh) by Sot was much less potent (IC(50) = 35.5 micro M) than inhibition by the high-affinity IKr blockers Ter, Ibu, and Dof. Superfusion of the cells with the IKs blocker Cro showed no desensitization of IK(ACh). Applied via the patch pipette (< 40 min) none of the class III drugs were effective. CONCLUSION: The results indicate inhibition of IK(ACh) and IKr but not IKs to be of similar mechanism (direct ion channel inhibition from the external side of the membrane). Potent desensitization of muscarinic potassium current could be of clinical relevance especially in patients with vagus-induced AF.
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Antiarrítmicos/uso terapéutico , Fibrilación Atrial/tratamiento farmacológico , Atrios Cardíacos/efectos de los fármacos , Fenetilaminas/uso terapéutico , Bloqueadores de los Canales de Potasio/uso terapéutico , Sotalol/uso terapéutico , Sulfonamidas/uso terapéutico , Nervio Vago/fisiología , Adulto , Animales , Antiarrítmicos/administración & dosificación , Antiarrítmicos/farmacología , Fibrilación Atrial/fisiopatología , Células Cultivadas , Medios de Cultivo , Atrios Cardíacos/citología , Humanos , Potenciales de la Membrana/efectos de los fármacos , Fenetilaminas/administración & dosificación , Fenetilaminas/farmacología , Bloqueadores de los Canales de Potasio/administración & dosificación , Bloqueadores de los Canales de Potasio/farmacología , Ratas , Sotalol/administración & dosificación , Sotalol/farmacología , Sulfonamidas/administración & dosificación , Sulfonamidas/farmacología , Factores de TiempoRESUMEN
OBJECTIVES: To determine whether the biplane area-length method can be used for the evaluation of left atrial volumes and ejection fraction with cardiovascular magnetic resonance imaging (CMR) by TrueFISP in normal subjects and patients with atrial fibrillation. BACKGROUND: Atrial fibrillation is the most common arrhythmia in elderly patients. Left atrial size and volumes play an important role in predicting short and long-term success after cardioversion. METHODS: Fifteen healthy subjects (mean age 65.6+/-6.4 years) and 18 patients (mean age 67.2+/-8.8 years) with atrial fibrillation were examined by CMR (Magnetom, Siemens, Erlangen, Germany). Images were acquired by TrueFISP using the horizontal and vertical long-axis plane to measure left atrial end-diastolic and end-systolic areas and longitudinal dimensions. Volumes were determined with commercially available software. Left atrial end-diastolic volume (EDV), end-systolic volume (ESV), stroke volume (SV), and ejection fraction (EF) were determined by the biplane area-length method and compared to findings obtained by the standard short-axis method. Images were acquired and analyzed a second time in the patients with atrial fibrillation. RESULTS: There was no difference in age between men and women (p=0.147) and healthy subjects and patients (p=0.128) included in the study. EDV and ESV were significantly higher and SV and EF significantly lower in patients with atrial fibrillation than in healthy subjects (p < or = 0.009), regardless of the method used. The values obtained for EDV and ESV by the biplane area-length method were significantly higher in both healthy subjects (p<0.001) and patients with atrial fibrillation (p<0.001) than those obtained by the standard short-axis approach, whereas SV (p> or = 0.057) and EF (p> or = 0.118) did not differ significantly. In the second investigation in patients with atrial fibrillation, ESV, SV, and EF did not differ significantly between the two methods (p> or =0.481). Assessment of interobserver variability revealed good agreement in the findings of the two observers, both in normal sinus rhythm and atrial fibrillation (overall variability 0.8+/-6.5%). CONCLUSIONS: The biplane area-length method can be used in CMR images obtained by TrueFISP to assess left atrial volumes and ejection fraction in normal subjects and patients with varying cardiac cycle length, as in atrial fibrillation.
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Fibrilación Atrial/fisiopatología , Frecuencia Cardíaca , Imagen por Resonancia Magnética , Volumen Sistólico , Anciano , Diástole , Femenino , Atrios Cardíacos/fisiopatología , Humanos , Masculino , Persona de Mediana Edad , Variaciones Dependientes del Observador , Tamaño de los Órganos , Valor Predictivo de las Pruebas , Reproducibilidad de los Resultados , Sístole , Función Ventricular IzquierdaAsunto(s)
Endocarditis Bacteriana/diagnóstico , Imagen por Resonancia Magnética/métodos , Insuficiencia de la Válvula Mitral/diagnóstico , Infecciones Estreptocócicas/diagnóstico , Anciano , Aminoglicósidos/uso terapéutico , Antibacterianos/uso terapéutico , Cefalosporinas/uso terapéutico , Endocarditis Bacteriana/complicaciones , Endocarditis Bacteriana/tratamiento farmacológico , Endocarditis Bacteriana/microbiología , Humanos , Masculino , Insuficiencia de la Válvula Mitral/etiología , Infecciones Estreptocócicas/complicaciones , Infecciones Estreptocócicas/tratamiento farmacológico , Infecciones Estreptocócicas/microbiología , Resultado del Tratamiento , Disfunción Ventricular Izquierda/diagnóstico , Disfunción Ventricular Izquierda/etiología , Estreptococos Viridans/aislamiento & purificaciónAsunto(s)
Taponamiento Cardíaco/diagnóstico por imagen , Taponamiento Cardíaco/etiología , Imagen por Resonancia Magnética , Síndrome Pospericardiotomía/complicaciones , Síndrome Pospericardiotomía/diagnóstico por imagen , Corticoesteroides/uso terapéutico , Adulto , Antiinflamatorios/uso terapéutico , Taponamiento Cardíaco/terapia , Puente de Arteria Coronaria , Enfermedad de la Arteria Coronaria/diagnóstico por imagen , Enfermedad de la Arteria Coronaria/cirugía , Electrocardiografía , Humanos , Masculino , Derrame Pericárdico/diagnóstico por imagen , Derrame Pericárdico/terapia , Pericardiocentesis , Complicaciones Posoperatorias/diagnóstico por imagen , Complicaciones Posoperatorias/etiología , Complicaciones Posoperatorias/terapia , Síndrome Pospericardiotomía/terapia , Intensificación de Imagen Radiográfica , Reoperación , Disfunción Ventricular Izquierda/diagnóstico por imagen , Disfunción Ventricular Izquierda/cirugíaAsunto(s)
Ablación por Catéter , Cicatriz/diagnóstico por imagen , Cicatriz/cirugía , Enfermedad Iatrogénica , Imagen por Resonancia Magnética , Taquicardia Ventricular/diagnóstico por imagen , Taquicardia Ventricular/cirugía , Técnicas Electrofisiológicas Cardíacas , Gadolinio , Ventrículos Cardíacos/diagnóstico por imagen , Ventrículos Cardíacos/patología , Humanos , Masculino , Persona de Mediana Edad , Intensificación de Imagen RadiográficaRESUMEN
PURPOSE OF REVIEW: Atrial fibrillation, atrial flutter, AV-nodal reentry tachycardia with rapid ventricular response, atrial ectopic tachycardia, and preexcitation syndromes combined with atrial fibrillation or ventricular tachyarrhythmias are typical arrhythmias in intensive care patients. Most frequently, the diagnosis of the underlying arrhythmia is possible from the physical examination, the response to maneuvers or drugs, and the 12-lead surface electrocardiogram. In all patients with unstable hemodynamics, immediate DC-cardioversion is indicated. Conversion of atrial fibrillation to sinus rhythm is possible using antiarrhythmic drugs. Amiodarone has a conversion rate in atrial fibrillation of up to 80%. However, caution in the use of short-term administration of intravenous amiodarone in critically ill patients with recent-onset atrial fibrillation is absolutely necessary, and the duration of therapy should not exceed 24 to 48 hours. Ibutilide represents a relatively new class III antiarrhythmic agent that has been reported to have conversion rates of 50% to 70%; it seems that ibutilide is even successful when intravenous amiodarone failed to convert atrial fibrillation. RECENT FINDINGS: Newer studies compared the outcome of patients with atrial fibrillation and rhythm- or rate-control. Data from these studies (AFFIRM, RACE) clearly showed that rhythm control is not superior to rate control for the prevention of death and morbidity from cardiovascular causes. Therefore, rate-control may be an appropriate therapy in patients with recurrent atrial fibrillation after DC-cardioversion. Acute therapy of atrial flutter in intensive care patients depends on the clinical presentation. Atrial flutter can most often be successfully cardioverted to sinus rhythm with energies less than 50 joules. Ibutilide trials showed efficacy rates of 38-76% for conversion of atrial flutter to sinus rhythm compared with conversion rates of 5-13% when intravenous flecainide, propafenone, or verapamil was administered. In addition, a high dose (2 mg) of ibutilide was more effective than sotalol (1.5 mg/kg) in conversion of atrial flutter to sinus rhythm (70% versus 19%). SUMMARY: There is general agreement that bystander first aid, defibrillation, and advanced life support is essential for neurologic outcome in patients after cardiac arrest due to ventricular tachyarrhythmias. The best survival rate from cardiac arrest can be achieved only when (1) recognition of early warning signs, (2) activation of the emergency medical services system, (3) basic cardiopulmonary resuscitation, (4) defibrillation, (5) management of the airway and ventilation, and (6) intravenous administration of medications occurs as rapidly as possible. Public access defibrillation, which places automatic external defibrillators in the hands of trained laypersons, seems to be an ideal approach in the treatment of ventricular fibrillation. The use of automatic external defibrillators by basic life support ambulance providers or first responder in early defibrillation programs has been associated with a significant increase in survival rates. Drugs such as lidocaine, procainamide, sotalol, amiodarone, or magnesium were recommended for treatment of ventricular tachyarrhythmias in intensive care patients. Amiodarone is a highly efficacious antiarrhythmic agent for many cardiac arrhythmias, ranging from atrial fibrillation to malignant ventricular tachyarrhythmias, and seems to be superior to other antiarrhythmic agents.
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Antiarrítmicos/uso terapéutico , Arritmias Cardíacas/terapia , Cuidados Críticos , Anciano , Amiodarona/uso terapéutico , Arritmias Cardíacas/tratamiento farmacológico , Fibrilación Atrial/terapia , Aleteo Atrial/terapia , Desfibriladores Implantables , Cardioversión Eléctrica , Electrocardiografía , Hemodinámica , Humanos , Lidocaína/uso terapéutico , Sotalol/uso terapéutico , Taquicardia/terapia , Taquicardia Ventricular/terapiaRESUMEN
KB130015 (KB015), a new drug structurally related to amiodarone, has been proposed to have antiarrhythmic properties. In contrast to amiodarone, KB015 markedly slows the kinetics of inactivation of Na(+) channels by enhancing concentration-dependently (K(0.5) asymptotically equal to 2 microM) a slow-inactivating I(Na) component (tau(slow) asymptotically equal to 50 ms) at the expense of the normal, fast-inactivating component (tau(fast) asymptotically equal to 2 to 3 ms). However, like amiodarone, KB015 slows the recovery from inactivation and causes a shift (K(0.5) asymptotically equal to 6.9 microM) of the steady-state voltage-dependent inactivation to more negative potentials. Despite prolonging the opening of Na(+) channels KB015 does not lengthen but often shortens the action potential duration (APD) in pig myocytes or in multicellular preparations. Only short APDs in mouse are markedly prolonged by KB015, which frequently induces early afterdepolarizations. KB015 has also an effect on other ion channels. It decreases the amplitude of the L-type Ca(2+) current (I(Ca-L)) without changing its time course, and it inhibits G-protein gated and ATP-gated K(+) channels. Both the receptor-activated I(K(ACh)) (induced in atrial myocytes by either ACh, adenosine or sphingosylphosphorylcholine) and the receptor-independent (GTPgammaS-induced or background) I(K(ACh)) are concentration-dependently (K(0.5) asymptotically equal to 0.6 - 0.9 microM) inhibited by KB015. I(K(ATP)), induced in atrial myocytes during metabolic inhibition with 2,4-dinitrophenol (DNP), is equally suppressed. However, KB015 has no effect on I(K1) or on I(to). Consistent with the effects in K(+) currents, KB015 does not depolarize the resting potential but antagonizes the APD shortening by muscarinic receptor activation or by DNP. Intracellular cell dialysis with KB015 has marginal or no effect on Na(+) or K(+) channels and does not prevent the effect of extracellularly applied drug, suggesting that KB015 interacts directly with channels at sites more easily accessible from the extracellular than the intracellular side of the membrane. At high concentrations KB015 exerts a positive inotropic action. It also interacts with thyroid hormone nuclear receptors. Its toxic effects remain largely unexplored, but it is well tolerated during chronic administration.
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Amiodarona/análogos & derivados , Antiarrítmicos/farmacología , Benzofuranos/farmacología , Canales Iónicos/efectos de los fármacos , Miocardio/metabolismo , Potenciales de Acción/efectos de los fármacos , Amiodarona/efectos adversos , Amiodarona/farmacología , Animales , Antiarrítmicos/efectos adversos , Antiarrítmicos/farmacocinética , Benzofuranos/efectos adversos , Benzofuranos/farmacocinética , Canales de Calcio Tipo L/efectos de los fármacos , Canales de Calcio Tipo L/fisiología , Canales Iónicos/fisiología , Contracción Miocárdica/efectos de los fármacos , Canales de Potasio/efectos de los fármacos , Canales de Potasio/fisiología , Canales de Sodio/efectos de los fármacos , Canales de Sodio/fisiología , Estimulación QuímicaRESUMEN
OBJECTIVES: The purpose of this study was to answer the question of whether stimulation after administration of catecholamines is mandatory for identifying unsuccessful ablations of atrioventricular node re-entrant tachycardia (AVNRT). BACKGROUND: The success of radiofrequency (RF) catheter ablation in AVNRT is confirmed in many centers by noninducibility of tachycardias during stimulation after the administration of catecholamines. METHODS: A total of 131 patients (81 women and 50 men; mean age 53.6 +/- 13.7 years [range 20 to 77]) were studied. Electrical stimulation was performed without and with the beta-adrenergic amine Orciprenaline (metaproterenol) before and after RF catheter ablation. RESULTS: In 100 patients (76.3%; confidence interval [CI] 68.1% to 83.3%) an AVNRT was inducible without administration of Orciprenaline. Thirty minutes after the initially successful ablation in 95 patients, tachycardia was inducible in none of these patients, not even after Orciprenaline administration. In the 31 patients (23.7%; CI 16.7% to 31.9%) in whom there was no tachycardia inducible before ablation, Orciprenaline was given, and the stimulation protocol was repeated. In only five patients (3.8%; CI 1.3% to 8.7%) was there still no tachycardia inducible. After an initially successful ablation in the 26 patients who had inducible tachycardias with Orciprenaline before ablation, no tachycardia could be re-induced. After Orciprenaline, the tachycardia was inducible again in only one patient. CONCLUSIONS: Only patients who require catecholamines for tachycardia induction before ablation need catecholamines for control of the success of the ablation of AVNRT.