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INTRODUCTION: Inappropriate sinus tachycardia (IST) is a common condition with frequently not tolerated beta-blockers or ivabradine and a high rate of complication in ablation strategy; we describe an alternative anatomical approach of sinus node (SN) modulation. METHODS: This retrospective study describes a case series of 6 patients from two centers diagnosed with symptomatic IST undergoing SN ablation. RESULTS: The mean age was 40.6 ± 13.9 years; five of the six patients were female, 100% of patients reported heart palpitations, and 66% reported dizziness, the average heart rate (HR) on a 24-h Holter was 93.2 ± 7.9 bpm. HR during the first stage of a stress test using a standard Bruce protocol was 150 ± 70 bpm, The average HR on 24-h Holter postablation was 75 ± 5.6 bpm, the sinus rate HR during stage 1 of a Bruce protocol exercise stress test was 120 ± 10 bpm. CONCLUSION: This is the first case series reporting the acute and long-term results of a novel anatomical approach for SN modulation to treat IST targeting the arcuate ridge (AR) under intracardiac echography (ICE) guidance. The novel anatomic ICE-guided catheter ablation approach aimed to identify the earliest activation at the AR with an extension of RF lesions toward its septal region seems effective and safe to modulate the SN in symptomatic patients with IST refractory to medical treatment.

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OBJECTIVE: To date, no systematic work has been intended to describe spatio-temporal patterns of cardiac rhythms using only short series of RR intervals, to facilitate visual or computerized-aided identification of EKG motifs for use in clinical practice. The aim of this study was to detect and classify eye-catching geometric patterns of Poincaré time-delay plots from different types of cardiac rhythms and arrhythmias using short-term EKG signals. METHODS: Approximately 150-300 representative, consecutive beats were retrieved from 24-h Holter registers of 100 patients with different heart rhythms. Two-dimensional Poincaré charts were created, and the resulting geometric patterns were transformed into representative familiar eye-catching drawings to interpret different arrhythmias. RESULTS: Poincaré plot representation of RR interval data revealed a wide variety of visual patterns: (i) comet-shaped for sinus rhythm; (ii) torpedo-shaped for sinus bradycardia; (iii) cigarette-shaped for sinus tachycardia; (iv) butterfly-shaped for sinus tachycardia and isolated atrial premature complexes; (v) arrow-shaped for isolated premature complexes and inappropriate sinus tachycardia; (vi) inverted fan-shaped for sinus rhythm with frequent atrial premature complexes; (vii) tornado-shaped for atrial flutter and atrial tachycardia; and (viii) fan-shaped for atrial fibrillation. CONCLUSIONS: Modified Poincaré plots with smoothed lines connecting successive points could accurately classify different types of arrhythmias based on short RR interval sequence variability. Characteristic emergent patterns can be visually identified and eventually could be distinguished by an automatic classification system able to discern between arrhythmias. This work provides an alternative method to interpret time-delay plots obtained from short-term EKG signal recordings.

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A patient with palpitations and narrow QRS tachycardia was evaluated. In the EP study an atrioventricular reentrant tachycardia mediated by a left lateral accessory pathway was identified and catheter ablation was performed with success. A week later she returned with palpitations and pre-syncope. The resting ECG showed a sinus tachycardia with 110 bpm. After unsuccessful clinical treatment with beta-blockers, diltiazem and digoxin she underwent sinus node modification using radiofrequency catheter ablation with success. We postulated that RF application to ablate the lateral accessory pathway damaged the parasympathetic innervation in the left atrioventricular groove, causing inappropriate sinus tachycardia.

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INTRODUCTION: The aim of this study was to determine the characteristics of heart rate variability (HRV), blood pressure variability (BPV), and baroreflex gain (BRG) at rest and during orthostatic stress in patients with clinical criteria of inappropriate sinus tachycardia (IST). METHODS AND RESULTS: Beat-to-beat HRV and BPV, measured by time- and frequency-domain methods, and noninvasive BRG, calculated by cross-spectral analysis, were obtained during 10 minutes both at rest and during the stabilization phase (5-15 min) of orthostatic stress at 60 degrees in 8 patients with clinical criteria of IST and 9 healthy volunteers (CON). IST patients had a higher resting mean heart rate (78.8 +/- 5.3 vs 58.5 +/- 4.2 beats/min, P=0.01) and mean blood pressure (90.4 +/- 2.4 vs 72.0 +/- 4.2 mmHg; P=0.002). RMSSD, pNN50m, and BRG were significantly reduced in IST patients at rest. BRG during orthostatic stress (7.2 +/- 0.8 vs 20.3 (2.4 ms/mmHg, P <0.01) was significantly reduced in IST patients. Delta BRG (-16.9%+/- 11 vs -50.1%+/- 5, P=0.02) was markedly blunted during orthostatic stress in IST patients. CONCLUSION: BRG was markedly impaired both at rest and during orthostatic stress in IST patients. This alteration may be responsible for the higher resting heart rate and mean blood pressures seen at rest and may facilitate tachycardia during orthostatic stress. A primary alteration in sinus node automaticity coupled with impaired BRG determines heart rate response to orthostatic stress in patients with IST.

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INTRODUCCION: El síndrome de taquicardia inapropiada (STSI) se ha atribuído a un aumento de la frecuencia intrínseca del nódulo sinusal, asociado con hipersensibilidad -adrenérgica y atenuación de la respuesta a la estimulación vagal. No se ha explorado la posibilidad de que en su patogenia intervenga una alteración inmunorregulatoria que involucre a los receptores -adrenérgicos. OBJETIVO: Evaluar la presencia de anticuerpos antirreceptores -adrenérgicos (Ac anti-) y antirreceptores M2-colinérgicos (Ac anti-M2) en pacientes con STSI. MATERIAL Y METODOS: Se incluyeron 10 mujeres de 21 a 64 años portadoras del síndrome y 10 voluntarias sanas. La presencia de Ac anti- y Ac anti-M2 se determinó por el efecto cronotrópico de la IgG sobre cultivos de miocardiocitos de ratas neonatas en condiciones basales y luego de adicionar los bloqueantes atropina (10-7 mol/L) y propanolol (10-7 mol/L). RESULTADOS: La IgG de las voluntarias sanas no presentó anticuerpos antirreceptores autonómicos. En cambio, 8 de las 10 pacientes con STSI presentaron Ac anti- (80 por ciento, p= 0,0004), pero en ninguna de ellas se detectaron Ac anti-M2. CONCLUSION: Un porcentaje elevado de las pacientes con STSI presentan anticuerpos que reconocen y estimulan los receptores ß-adrenérgicos. Esta observación inédita sugiere la posibilidad de que en la patogenia de este síndrome participe una anormalidad inmunorregulatoria que involucra a esos receptores. (AU)

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Las taquicardias auriculares son aquellas taquicardias supraventriculares cuyo mecanismo de origen y mantenimiento se localiza exclusivamente a nivel auricular. Clínicamente plantean dificultades diagnósticas y terapéuticas. Su inadecuado manejo puede ocasionar compromiso de la función ventricular y comprometer el pronóstico vital. El tratamiento farmacológico, el más usado, es poco efectivo. La ablación por cateter con radiofrecuencia es una nueva arma terapéutica trascendente para la resolución de un grupo significativo de estos pacientes. En el presente artículo se realiza una revisión del concepto de taquicardias auriculares, se actualiza su clasificación y se repasan los mecanismos fisiopatológicos. Se analizan en detalle las taquicardias auriculares focales y las taquicardias por macrorrentrada, entre ellas el flutter atrial y sus diferentes tipos y las taquicardias incisionales relacionadas a cirugía de cardiopatías congénitas. Se describen las técnicas de ablación por cateter en estas arritmias y se revisan sus resultados en la literatura. Finalmente, se presenta la casuística del Servicio en el tratamiento de las taquicardias auriculares focales, incisionales y flutter atrial mediante ablación por cateter con radiofrecuencia(AU)

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To clarify the mechanism responsible for the transient sinus tachycardia in rats with acute chagasic myocarditis, we have examined the cardiac sympathetic-parasympathetic balance of 29 rats inoculated with 200,000 parasites (Trypanosoma cruzi). Sixteen infected animals and 8 controls were studied between days 18 and 21 after inoculation (acute stage). The remaining 13 infected animals and 9 controls were studied between days 60 and 70 after inoculation (sub-acute stage). Under anesthesia (urethane 1.25 g/kg), all animals received intravenous atenolol (5 mg/kg) and atropine (10 mg/kg). Acute stage: The baseline heart rate of the infected animals was significantly higher than that of the controls (P < 0.0001). The magnitude of the negative chronotropic response to atenolol was 4 times that of the controls (P < 0.00001). This response correlated with the baseline heart rate (r = -0.72, P < 0.001). The heart rate responses to the beta-blocker and to atropine, of the infected animals studied during the sub-acute stage, were not different from controls. These findings suggest that cardiac sympathetic activity is transiently enhanced and cardiac parasympathetic activity is not impaired, in rats with acute chagasic myocarditis. The transient predominance of cardiac sympathetic activity could explain, in part, the sinus tachycardia observed in the acute stage of experimentally-induced chagasic myocarditis.

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En 64 pacientes sin cardiopatía demostrada y con edades entre 8 y 82 años ; para evaluar presencia de arritmias cardiacas y sus variaciones según la edad, se efectuó Holter de 24 hrs.; correlacionando las arritmias con los síntomas referidos. Se encontró arritmias en un 90,7, de las cuales fueron supraventriculares en 17,3 ventriculares en 13,8 y ambas arritmias en un 68,9, hubo concordancia sintomática en un 37,5. Las arritmias aisladas más frecuentemente se presentaron en sujetos por debajo de 60 años; y las repetitivas por encima de ésa edad. Estas arritmias si son sintomáticas, deben ser tratadas; siendo el pronóstico bueno cuando no provocan síntomas.

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Los autores hacen una revisión de las arritmias propias de la infancia, en cuanto a etiología, patogenia, interpretación del CG. Manifestaciones clínicas, bases del tratamiento y prevención

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This case report describes a patient with chronic chagasic myocarditis who presented with a unique tachycardia-dependent or phase 3 aberrant ventricular conduction. The electrocardiogram showed sinus tachycardia with sequences of alternate and progressive right bundle branch block, that is, Wenckebach periods of alternate beats. We postulated the existence of functional longitudinal dissociation in atrioventricular conduction axis, responsible for the alternant normal and Wenckebach beats.

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Fourteen normal subjects were submitted to isometric exercise (IE), dynamic exercise (DE) and a combination of the two (IE + DE). The main purpose of the present study was to use IE as a means of evaluating the mechanism of the heart rate (HR) increase induced by DE. To this end, the magnitude of the IE (handgrip) was standardized so as to cause an elevation of HR almost exclusively by vagal withdrawal: IE was performed using a dynamometer strain-gauge system with a linear response at 75% of maximum voluntary contraction (MVC) for 10 s, repeated at 1 min intervals. The change in HR evoked by IE under control conditions was compared with that evoked during DE, and during the corresponding recovery period. DE was performed by the legs, with the subject in the seated position for 4 min, at workloads of 55 and 105 watts, separated by a rest period. In the combined protocol, IE was performed at the beginning of DE, as well as at 1, 2 and 3 min during DE, and at 0, 1, 2, 3 and 5 min during recovery period. The following results were obtained: (1) IE associated with DE always induced smaller increase in heart rate than IE alone, and this effect was more marked at 105 than at 55 W; this finding suggested a workload-dependent vagal withdrawal at the very beginning of DE that was sustained until the end of effort.(ABSTRACT TRUNCATED AT 250 WORDS)

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