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 10,214 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cardiac rate and rhythm in 141 healthy infants, toddlers and schoolchildren during 24 hour ambulatory electrocardiographic monitoring are reported. Maximal and minimal heart rate (1/min) in infants 1 to 5 months of age were 204 +/- 17 and 105 +/- 13, in infants 6 to 12 months of age 187 +/- 19 and 101 +/- 15; in toddlers 177 +/- 17 and 66 +/- 10; in schoolchildren 158 +/- 24 and 54 +/- 6. A sizeable proportion of children of all age groups showed patterns of sinus arrhythmias indistinguishable from second degree sinuatrial block. Supraventricular escape beats and escape rhythms were frequent as well. The longest RR interval was 1.03 +/- 0.16 sec. in infants, 1.20 +/- 0.25 sec. in toddlers, and 1.35 +/- 0.15 sec., respectively, in schoolchildren. Two % of infants, 7% of toddlers, and 6% of schoolchildren had episodes of second degree atrioventricular block type I (Wenckebach) at rest. Supraventricular extrasystoles were found in 38%, 13% and 26%, respectively, and uniform ventricular extrasystoles in 18%, 20% and 16%, respectively, of infants, toddlers and schoolchildren. These data, together with similar information in the literature, can be taken as basis for the evaluation of ambulatory electrocardiograms in children.
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PMID:[Heart rate and heart rhythm in healthy infants and children]. 246 25

The cardiotoxic potential of the phenothiazine neuroleptic thioridazine and five of its metabolites, including two stereoisomeric forms of thioridazine 5-sulfoxide (ring sulfoxide), was characterized in the isolated perfused rat heart. Hearts from male Sprague-Dawley rats were perfused using a modified Langendorff technique. After a 30-min control period, hearts were perfused for 30 min with 15 or 30 microM thioridazine, racemic and isomeric forms of thioridazine 5-sulfoxide, or thioridazine 2-sulfoxide. Thioridazine disulfoxide, thioridazine 2-sulfone, and desmethylthioridazine 2-sulfoxide were perfused at 15 microM. Thioridazine (15 microM) severely reduced contractile tension and the rate of tension development (dT/dt), transiently increased coronary flow rate but prolonged conductance through the AV node. No arrhythmias were seen. At 30 microM, ventricular premature contractions and irregular rhythms occurred, progressing to asystole. Thioridazine 5-sulfoxide was arrhythmogenic at 15 and 30 microM. Atrial premature contractions and paroxysmal atrial tachycardia progressed to second degree AV block. Contractile tension and dT/dt declined although not as quickly when compared to thioridazine. Each isomeric form of thioridazine 5-sulfoxide was also cardiotoxic at 15 and 30 microM. There were minor differences in the onset and degree of toxicity but the overall results did not suggest a stereoselective effect. Lactic dehydrogenase and aspartate aminotransferase concentrations were unchanged after thioridazine 5-sulfoxide perfusion indicating no direct tissue damage. Thioridazine 5-sulfoxide induced arrhythmias could not be prevented or reversed by treatment with adrenergic agonists. They were reversible upon washout, however. The other metabolites were not arrhythmogenic at 15 microM. Racemic thioridazine 5-sulfoxide appears to be qualitatively and quantitatively more arrhythmogenic than thioridazine, an action that does not appear to be stereoselective.
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PMID:Cardiotoxicity of thioridazine and two stereoisomeric forms of thioridazine 5-sulfoxide in the isolated perfused rat heart. 376 35

Sixty-six patients in whom atrial pacemaker (AAI) were implanted were followed for one year to 5 years for the occurrence of pacing failure, sensing problems, and later AV block. Pacing failure occurred in only one patient and sensing problems occurred in 15 patients but 10 of them improved after a change of sensing. Temporal change of AV conductivity was not recognized in the majority of patients. Eighteen patients developed transient decrease in AV conductivity. Two patients developed persistent decrease in AV conductivity and ended in clinical AV block for which the pacemaker was implanted. Out of 66 patients, 22 had a history of paroxysmal atrial flutter or fibrillation (AFF) prior to AAI implantation. They were divided into two groups. Group I consisted of 20 patients in whom paroxysmal AFF disappeared after AAI implantation. Group II consisted of 22 patients in whom paroxysmal AFF persisted after AAI implantation. Electrophysiological studies prior to the AAI implantation showed that sinus rate at control was significantly slower (36.3 +/- 10.1 beats per min in Group I, 57.1 +/- 10.8 beats per min in Group II), atrial fragmented activity zone was significantly narrower (62.7 +/- 32.9 msec in Group I, 88.1 +/- 19.7 msec in Group II), and the occurrence of PAC was less at an atrial pacing rate of 70 beats per min (8% in Group I, 67% in Group II) in Group I compared to Group II.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Problems and anti-tachyarrhythmic effects of chronic atrial pacing. 398 96

In a prospective randomized study we searched for arrhythmogenic effects of the tetracyclic antidepressant, a maprotiline, and the tetrahydroisoquinoline derivative, nomifensine. Forty depressive patients from the psychiatric outpatients department were included in the study. Twenty patients in each group received maprotiline or nomifensine over three weeks in the recommended daily dosage of 75 mg. Rhythm analysis was performed before therapy, at the end of 3 weeks therapy, and 1 week after withdrawal from medication using a dual channel long-term ECG with monitoring periods of 10 h during normal daily activities. Before treatment, spontaneous incidence of all ventricular ectopics and of their complex forms was within the normal range when compared with ectopic activity of 121 "normal subjects" without detectable heart disease. No significant increase could be demonstrated during therapy with maprotiline or nomifensine, nor was any change observed 1 week after medication had been stopped. The same was true for supraventricular extrasystoles; atrial tachycardia, atrial flutter, and fibrillation were never seen. Sinoatrial (n=2) and atrioventricular block (n=1) were rare findings independent of and not affected by treatment. No bundle branch blocks were observed before, during, and after treatment. In contrast, despite the conservative dosage of both drugs, a therapy-dependent increase in average heart rate was found (p less than 0.001). This increase was significantly higher in patients receiving nomifensine than in those treated with maprotiline (p less than 0.001), suggesting a lower intrinsic anticholinergic activity of the latter compound.
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PMID:Incidence of cardiac arrhythmias during antidepressant therapy with maprotiline or nomifensine. 617 91

Twenty-four-hour ambulatory ECG recording was performed in 26 patients with variant angina to evaluate the diurnal distribution of ST-segment elevation in relation to chest pain and the incidence of arrhythmias during the episodes. During a recording period of 52 days, 364 ST-segment elevations of 1 mm or greater were observed and 79% were asymptomatic. ST-segment elevation frequently occurred between 0:00 and 9:00 hours (72%) and most frequently between 5:00 and 6:00 hours (13%). Only a few episodes occurred between 10:00 and 18:00 hours. Premature atrial contractions, premature ventricular contractions (PVCs), ventricular tachycardia (VT) and complete atrioventricular block occurred during 12% of the episodes and were more common during painful episodes (32%) than during painless ones (6%). However, VT and severe forms of PVCs (couplets and bigeminy) appeared eight times during painless episodes and nine times during painful ones. Arrhythmias occurred more frequently when the elevated ST segment started to return or was returning to the control level (n = 38) than when the ST segment was rising (n = 8). The incidence of arrhythmias was lower when the daily frequency of ischemic episodes was high. This study shows that episodes of asymptomatic coronary artery spasm predominantly occur early in the morning as symptomatic episodes; complex dysrhythmias appear during the asymptomatic episodes; arrhythmias occur predominantly during a "reperfusion period;" and more arrhythmias accompany infrequent daily episodes of ischemia than frequent ones.
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PMID:Diurnal distribution of ST-segment elevation and related arrhythmias in patients with variant angina: a study by ambulatory ECG monitoring. 668 20

Diastolic mitral valve "locking," defined as sustained diastolic closure of the mitral valve after atrial systole, was investigated by simultaneous hemodynamic and echocardiographic recordings during a protocol of programmed pacing in six dogs with surgically induced atrioventricular block. Atrial extrasystoles were introduced at progressively increasing coupling intervals during programmed prolonged pauses in ventricular pacing. As the coupling interval of the atrial extrasystole was increased, both the mitral reopening time (MRT) and the calculated left ventricular volume (LVV) at the end of the MRT increased proportionally. These interrelations could be best expressed by a general logarithmic function of the form y = a + b ln (x), where x = the coupling interval of the atrial extrasystole and y = the MRT or the LVV. Correlations between the measured data and the predicted data were excellent (r greater than or equal to 0.95). In each dog, a specific LVV had to be attained to allow a diastolic "locking" of the mitral valve. Atrial standstill and atrial fibrillation were also induced in each dog to study the relative role of atrial systole in locking of the mitral valve. During either atrial standstill or atrial fibrillation, the mitral valve closed transiently, but did not lock, despite the accumulation of a LVV larger than the LVV necessary to lock the valve during sinus rhythm. Thus, diastolic locking of the mitral valve has several determinants, including the presence of active atrial systole and the accumulation of a sufficient intraventricular volume.
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PMID:Diastolic "locking" of the mitral valve: the importance of atrial systole and intraventricular volume. 682 7

Reported here are 162 cases of atrial ectopic tachycardia, a specific type of the supraventricular arrhythmia, which is characterized by the distinct P waves on the ECG, which follow at the rate of 400 and more per minute. Although atrial ectopic tachycardia is similar to the supraventricular paroxysmal tachycardia and atrial flutter, it differs from them by the mechanism of the development. Atrial ectopic tachycardia is caused by the failure or weakening the sinus node and the appearance of the ectopic focus in the atria. Such arrhythmia occurs in the following 4 types: with atrial to ventricular excitation ratio 1:1; with incomplete atrio-ventricular block; with complete atrioventricular block; and in combination with atrial fibrillation. Atrial ectopic tachycardia often takes lingering course and is hardly responsive to the medical treatment. The cases of arrhythmia, characterized by the broad P waves on the ECG tend to the progressive course. 17 cases of atrial ectopic tachycardia treated by electrostimulation (ES) which had 100% positive effect are presented and ES advantages over the drug therapy are underlined. The frequent transition of this arrhythmia into the atrial fibrillation is outlined.
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PMID:[Diagnostic and treatment characteristics of ectopic atrial tachycardia]. 707 9

Aim of the present study was to evaluate 24 h electrocardiographic recording in 30 top athletes, 30 athletic students and 30 sedentary control subjects. Each group consisted of 15 males and 15 females and were matched for age (about 24 years). Training was not allowed during the recording. Top athletes had the lowest diurnal and nocturnal heart rate, but the difference between top athletes and athletic students was far less pronounced than between athletic students and controls. This may indicate that bradycardia reaches a lower limit with moderate degrees of training. Atrioventricular (AV) block II was found in 3 top athletes and 4 athletic students and in none of the subjects, the longest pause being 2.4 s in both athletic groups. Most episodes occurred during night and nearly all were Mobitz type I. In all cases of AV block II the QRS complexes were narrow and AV block III did not occur. SA block was found in 3 top athletes, 1 athletic student and 1 control subject, the longest pause being 3.1, 2.9 and 1.9 s, respectively. Ventricular premature beats were rare in all groups and complex ventricular arrhythmias were not found. Half of the subjects were in Lown class 0, the other half in Lown class 1. Supraventricular premature beats were also scarce and most frequent in top athletes, followed by athletic students and sedentary controls (2.0, 1.0, 0.7 beats/h, respectively).
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PMID:Ambulatory electrocardiographic findings in top athletes, athletic students and control subjects. 814 88

Continuous monitoring of the electrocardiogram has become a commonly used technique in the safety assessment of new drugs when these are administered to human beings for the first time. Disturbances of cardiac rhythm have been observed with cardiac monitoring during clinical pharmacology studies in normal healthy volunteers. It is often difficult to assess the clinical significance of these rhythms especially when these rhythms occur following the administration of new drugs to human beings for the first time. Certain arrhythmias are frequently noted in normal healthy adults, including sinus bradycardia, sinus arrhythmia, the Wenckebach type of second-degree AV block (Mobitz I), atrioventricular junctional rhythm, PAC's, and PVC's. PAC's and PVC's are commonly observed, although greater than 50 PVC's/24 hr and greater than 100 PAC's/hr are relatively rare. Atrial couplets/atrial tachycardia and ventricular couplets/nonsustained ventricular tachycardia are relatively rare, but nevertheless do occur on occassion in normal healthy adults. With these consideration in mind, a guideline for the interpretation and reporting of cardiac arrhythmias occurring during clinical pharmacology studies in normal healthy adults is presented. The absence of symptoms or structural heart disease are important considerations in the evaluation of arrhythmias in normal healthy adults. The severity and seriousness of the adverse experience should be left up to the investigator's discretion. Rechallenge with active drug or placebo should be considered on a case-by-case basis.
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PMID:Cardiovascular Monitoring in Normal Healthy Adults: A Literature Review and Recommendations for the Reporting of Disturbances of Cardiac Rhythm. 1185 4

Atrial Preference Pacing (APP) is a pacemaker (PM) algorithm that works by increasing the atrial pacing rate to achieve continuous suppression of a spontaneous atrial rhythm and prevent supraventricular tachyarrhythmias. We have previously shown that atrial preference pacing may significantly reduce the number and the duration of AF episodes in myotonic dystrophy type 1 (DM1) patients who are paced for standard indications.However, the role that APP therapies play in the prevention of AF in a long-term period remains still unclear. Aim of the present prospective study was to evaluate whether this beneficial effect is maintained for 24-months follow-up period.To this aim, 50 patients with Myotonic Dystrophy type 1 who underwent dual-chamber PM implantation for first- and second- degree atrioventricular block, were consecutively enrolled and followed for 2 years. One month later the stabilization period, after the implantation, they were randomized to APP algorithm programmed OFF or ON for 6 months each, using a cross-over design, and remained in the same program for the second year. The results showed that while the number of AF episodes during active treatment (APP ON phases) was lower than that registered during no treatment (APP OFF phases), no statistically significant difference was found in AF episodes duration between the two phases. Furthermore, during the APP OFF and APP ON phases, the percentage of atrial pacing was 0 and 99%, respectively, while the percentage of ventricular pacing did not show differences statistically significant (11 vs. 9%, P = 0.2). Atrial premature beats were significantly higher during APP OFF phases than during APP ON phases. Lead parameters remained stable over time and there were no lead-related complications. Based on these 24-months follow-up data, we can conclude that, in DM1 patients who underwent dual-chamber PM implantation, APP is an efficacy algorithm for preventing paroxysmal AF even in long term periods.
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PMID:Right atrial preference pacing algorithm in the prevention of paroxysmal atrial fibrillation in myotonic dystrophy type 1 patients: a long term follow-up study. 2309 6


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