RESUMEN

Erythropoiesis is finely regulated by two major cytokines, stem cell factor (SCF) and erythropoietin (Epo). Decrease levels of Epo result in caspase activation and erythroid progenitors apoptosis. However, normal erythroid cell maturation requests caspase activation and cleavage of various caspase substrates, except the erythroid transcription factor GATA-1, that is protected by interaction with the chaperone HSP70 in the nucleus. Therefore, molecular abnormalities associated with decrease of HSP70 expression in the nucleus may result in ineffective erythropoiesis characterized by apoptosis and impaired maturation of erythroid precursors. These findings open new potential targeted therapies for erythroid disorders.

Asunto(s)

RESUMEN

The sinus disease in children with "healthy hearts" is exceptional, and has never been documented by tracing of the sinus node. We are reporting two cases of two children, aged 4 and 14 years. An electrophysiological exploration with measurement of the direct activity of the sinus node, illustrates in one case the mechanism of sinus dysfunction. A review from the literature and our cases specifies some of the characteristics of this disease: 1) there are two forms: sporadic (case n. 1) 59 published cases, and familial (case n. 2) 28 published cases in 13 families; 2) the familial forms have a dominant autosomic transmission with variable penetration; 3) the disease may occur during the first days of life, suggesting a congenital origin (from the pathology findings, this disease may be one of the causes of the unexplained sudden death syndrome in infants; 4) association to atrio-ventricular conduction disorders and atrial and ventricular rhythm disorders; 5) frequent indication of stimulators, emphasizing the severity of this disease with a more severe course in sporadic forms (7 deaths in 59 cases).

Asunto(s)

RESUMEN

The authors report a case of sustained ventricular tachycardia which occurred seven years after complete surgical correction of Fallot's tetralogy in a 13 year old girl. This arrhythmia was well tolerated haemodynamically, showed right-sided delay and was associated with mitral valve prolapse. After reviewing the literature, several physiopathological mechanisms are discussed: --the role of residual intraventricular conduction defects in sustaining the tachycardia; --the role of the ventriculotomy scar or of other associated lesions (mitral valve prolapse in this case) in the genesis of ventricular extrasystoles; --the postoperative haemodynamic status in the tolerance of the arrhythmias. This is a rare complication with an incidence of less than 2% of survivors followed-up over long periods. There is a risk of sudden death in 38% of these patients with ventricular arrhythmias which justifies Holter monitoring and ECG stress testing for their detection.

Asunto(s)

RESUMEN

In order to determine the significance of prolongation of the direct sinoatrial conduction time (DSACT), an attempt was made to record the sinus node potential in 110 patients which was successful in 84 cases. The DSACT was normal in 45 cases (Group A) and prolonged (over 130 ms) in 39 cases (Group B). The symptomatology, standard ECG and the results of investigation of sinus node function by atrial stimulation of the two groups were compared. The DSACT was prolonged in all 13 patients with paroxysmal sinoatrial block or the sick sinus syndrome, in 71% of 15 patients with permanent sinus bradycardia, in 88% of 22 patients with a corrected sinus node recovery time of over 525 ms, in 82% of 38 patients with a sinoatrial conduction time estimated by the extrastimulus method of over 130 ms or an abnormal zone II, in 80% of 39 patients with sinoatrial conduction times estimated by Narula's method of over 130 ms; therefore, 87% of the 35 patients with probable sinus node dysfunction had long DSACT. On the other hand only 2 out of 35 patients (6%) with apparently normal sinus node function had prolonged DSACT. These results indicate that prolongation of the DSACT is a sensitive and specific criterion of sinus node dysfunction. In cases of sinus node dysfunction dizziness and/or syncope without any known cause were common complaints in patients in Group B but absent in patients in Group A. A prolonged DSACT could be of prognostic significance in sinus node dysfunction.

Asunto(s)

Asunto(s)

RESUMEN

Directly measured sinoatrial conduction time was compared with sinoatrial conduction time assessed simultaneously by the single premature atrial stimulus technique in 59 patients: 20 with normal sinus function, 35 with sinus dysfunction, and four with sinus bradycardia but negative indirect methods. In patients with normal sinus function direct sinoatrial conduction time was 102.5 +/- 34 ms (mean +/- 2 SD) and was identical to indirect sinoatrial conduction time. Neither direct sinoatrial conduction time in the basal and return cycle, nor post-return and basal cycle lengths were different. Sinoatrial and atriosinus conduction durations were similar. In sinus dysfunction direct sinoatrial conduction time (average 160 +/- 47 ms) was longer than in normal sinus function. Prolonged direct sinoatrial conduction time may therefore be considered as a criterion of sinus dysfunction. In sinus dysfunction no significant correlation was observed between direct and indirect sinoatrial conduction times. Direct sinoatrial conduction time was equal to (17 patients), longer than (12 patients), or shorter than (six patients) indirect sinoatrial conduction time. These differences can be explained by delayed or incomplete premature depolarisation penetration into the sinus node rather than by the classical pacemaker shift.

Asunto(s)

Asunto(s)

RESUMEN

The sino-atrial conduction time, measured by Narula's method (SACTN) is compared to the direct sino-atrial conduction time measured by recording the sinus potential (SACTD) in 55 patients, 20 with normal sinus function and 35 with sinus dysfunction. In the absence of sinus dysfunction, SACTN and SACTD are not significantly different and a significant but mediocre correlation (r = 0.57) is observed between the two parameters. Major discordances between the two methods are seen in 4 patients. In cases with sinus dysfunction, there was no correlation between SACTD and SACTN; SACTN is close to SACTD in 12 patients, but much shorter in 11 patients and much longer in 10 patients. These discordances raise the problem of the penetration of the sinus node by the extrastimulus in Narula's method. This method does not seem capable of giving a reliable evaluation of the duration of sino-atrial conduction.

Asunto(s)

RESUMEN

Sinus node function was evaluated by Mandel, Strauss and Narula's methods in 60 consecutive patients: 20 females, 40 males; average age 59 +/- 17 years. Three had second degree sinoatrial block, 2 had bradycardia-tachycardia syndromes and 10 had sinus bradycardia. The corrected sinus node recovery time was 414 +/- 417 ms. It exceeded 520 ms in 8 cases, 5 where the two other methods confirmed sinus node dysfunction, 1 where the two other methods showed no abnormality. In the last two patients pathological results with Narula's method coincided with normal values with Strauss' method but the basal sinus cycle and the post return cycle differed from one method to the other. The atriosinoatrial conduction time estimated by Narula's method was 274 +/- 117 ms. In the thirteen cases where it exceeded 300 ms abnormal results were also recorded with Strauss' (11 cases) and/or Mandel's method (7 cases). The atriosinoatrial conduction time assessed by Strauss' method was 239 +/- 106 ms. It exceeded 300 ms in 18 patients. In these patients the results of Narula and Mandel's methods were normal in 7 cases. This discordance cannot be explained either by variations in the catheter position, or by the duration of the basal sinus or the post return cycles. This raises the question of penetration of the sinus node by the last stimulus when Narula's technique is used. A significant linear correlation was observed between the atriosinoatrial conduction time assessed by Narula's method and the atriosinoatrial time assessed by Strauss' method (N = 60; r = 0,59) and with the corrected sinus node recovery time (N = 60; r = 0,43) and a double linear correlation was found with these two parameters (N = 60; r = 0,62). There was no significant linear correlation between the atriosinoatrial conduction time assessed by Strauss' method and the corrected sinus node recovery time (N = 60; r = 0,27). The atriosinoatrial conduction time evaluated by Narula's method seems to be intermediary between the two other parameters which seem to be independent of each other.

Asunto(s)

Asunto(s)

Asunto(s)