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PubMed1985

Does the type of venous drainage or cardioplegia affect postoperative conduction and atrial arrhythmias?

Five consecutive patient groups undergoing coronary bypass surgery were studied for postoperative conduction disturbances and atrial arrhythmias. Group I (50 patients) had blood cardioplegic solution (25 meq/liter potassium) and unsnared venae cavae, group II (156 patients) had low-volume crystalloid cardioplegic solution (25 meq/liter potassium) and unsnared venae cavae, group III (56 patients) was similar to group II except that a single cavoatrial venous cannula was used instead of two separate cannulas, group IV (218 patients) had high-volume crystalloid cardioplegic solution (25 meq/liter potassium) and snared venae cavae, and group V (37 patients) was the same as group IV except that the cardioplegic solution contained 10 meq/liter potassium after the first dose, which contained 25 meq/liter. All postoperative electrocardiograms were analyzed for conduction disturbances and atrial arrhythmias. The results showed a significantly lower incidence of conduction disturbances in group I (12%) as compared with groups II to IV. In addition, groups IV and V (high-volume crystalloid cardioplegic solution) had a significantly higher incidence of conduction disturbances than groups II and III (lower-volume crystalloid solution) (55.0% and 62.1% vs 26.2% and 35.1%, respectively). The majority of these disturbances were temporary. Group I also had the lowest incidence of postoperative atrial arrhythmias (3.8%). There was no significant difference between the groups receiving high- and low-volume crystalloid solution. It is concluded that blood cardioplegic solution affords the best protection against postoperative conduction disturbances and atrial arrhythmias. High-volume crystalloid cardioplegic solution affords the least protection against conduction disturbances but has no effect on atrial arrhythmias.(ABSTRACT TRUNCATED AT 250 WORDS)

Arrhythmias, Cardiac↗
PubMed1992

Rate-dependent effects of diltiazem on human atrioventricular nodal properties.

BACKGROUND: Tachycardia enhances the channel-blocking effects of antiarrhythmic drugs. In contrast to the extensive data regarding the rate-dependent effects of sodium channel blockers in humans, little is known about the frequency-dependent effects of calcium channel blockers on human atrioventricular (AV) nodal properties. Accordingly, the purpose of this study was to evaluate the importance of heart rate in modulating the electrophysiological effects of diltiazem in humans. METHODS AND RESULTS: Electrophysiological studies were performed in 25 patients. Sinus node, atrial, and AV nodal function were evaluated at multiple atrial rates under control conditions and after administration of one of three intravenous doses of diltiazem designed to produce low, intermediate, and high stable plasma concentrations (designated doses 1, 2, and 3, respectively). Results were analyzed in terms of the longest and shortest cycle lengths obtainable in each patient under control and drug conditions. Plasma concentrations of diltiazem were stable and averaged 43 +/- 4, 73 +/- 6, and 136 +/- 11 ng/ml for doses 1, 2, and 3, respectively. Sinus node recovery time, intra-atrial conduction time, atrial effective refractory period, and HV interval were unaffected by diltiazem infusion. Effects of diltiazem were limited to changes in AV nodal parameters. Stable, dose-dependent increases in Wenckebach cycle length were observed after all three doses of diltiazem (increases of 54 +/- 13, 84 +/- 18, and 174 +/- 33 msec for doses 1, 2, and 3, respectively). Small nonsignificant increases in AH interval and atrioventricular effective refractory period (AVERP) were observed after dose 1 of diltiazem. At long cycle lengths, diltiazem caused modest increases in AH interval (3 +/- 4 and 25 +/- 8 msec for doses 2 and 3, respectively) and AVERP (36 +/- 12 and 70 +/- 25 msec). Drug effects were far greater at short cycle lengths (45 +/- 17 msec, 58 +/- 12 msec for AH interval and 80 +/- 24 msec, 163 +/- 41 msec for AVERP; p less than 0.05 versus values at long cycle lengths). At rapid rates, effects of diltiazem on AVERP substantially exceeded those on AV conduction, a result that could account for the beneficial effects of diltiazem during paroxysmal AV reentrant tachycardia by decreasing the excitable gap. CONCLUSIONS: Depressant effects of diltiazem on human AV nodal function are highly dependent on atrial rate; the rate-dependent actions on AV nodal refractoriness probably contribute to beneficial effects of diltiazem in patients with supraventricular arrhythmias.

Atrioventricular Node↗
PubMed1990

[Atrio-ventricular conduction in patients with permanent right- ventricular stimulation. II. Atrio-ventricular conduction time in patients with normal and impaired atrio-ventricular conduction].

UNLABELLED: We analyzed transesophageal ECG recordings of 79 patients (42 men and women aged 17-85 mean 61 +/- 16 yrs) with present ventriculo-atrial conduction phenomenon during permanent VVI stimulation. All measurements we performed on basic and magnetic rate of the pulse generator. V-a conduction time was defined as mean (from 5 measurements) time from spike of the pulse generator to the first deflection of P wave recorded from esophagus and expressed in miliseconds. We compared v-a conduction time (v-act) on basic and magnetic rates of a stimulator and between groups with normal (group A, 49 pts) and prolonged a-v conduction time (group B, 30 pts). Group B was divided on group B-1 (19 pts without bundle branch blocks) and B-2 (11 pts with bundle branch blocks during observations). V-act during magnetic rate (cycle 596 +/- 70 ms) was significantly longer than during basic rate (cycle 834 +/- 66 ms) (191 +/- 48 ms vs 185 +/- 44 ms, p 0.05). V-act in patients with a-v block (group B) was significantly longer than in patients with normal a-v conduction (group B) (219 +/- 45 ms vs 190 +/- 47 ms, p 0.02). The longest v-act was observed in group B-2 (236 +/- 32 ms). CONCLUSIONS: 1. Ventriculo-atrial conduction time could be measured in patients with permanent VVI stimulation using esophageal ECG recording. 2. Shortening of the stimulation cycle prolonges ventriculo-atrial conduction time. 3. Ventriculo-atrial conduction time is longest in group with atrio-ventricular conduction disturbances, especially in group with registered bundle branch block.

Adolescent↗
PubMed1983

Function of atrial preferential conduction routes under normal and abnormal conditions.

The function of the atrial preferential conduction routes was examined by the microelectrode technique under normal and abnormal conditions in excised rabbit hearts. The sinus impulse during normal conditions traveled faster along the left and the right branch of the crista terminalis (anterior and posterior preferential routes, respectively) in the atrium toward the A-V node. Cutting of either route caused a delay of the impulse arrival in the zone beyond the lesion. The internodal conduction time was delayed 12 msec upon cutting of the posterior route, but there was no conduction delay after cutting the anterior route. This indicates that the posterior path is the dominant conduction route under normal conditions. When both routes were cut, the internodal conduction time was delayed 33 msec from the control value. During abnormal conditions, an ectopic pacemaker was found to occur mainly in the regions of two routes, as well as in the coronary sinus region. The cutting of either route, combined with the application of acetylcholine or high external K+, resulted in easier provocation of re-entrant arrhythmias in response to premature-stimuli than before the cutting.

Animals↗
PubMed1985

Alternate ventriculo-atrial Wenckebach conduction during ventricular tachycardia.

Although pacing-induced ventriculo-atrial (VA) Wenckebach conduction has been previously described, the occurrence of this phenomenon during ventricular tachycardia has received little attention. The latter is defined as 2:1 VA block in which the conducted beats show progressive lengthening of VA conduction until the sequence is terminated by two or three blocked ventricular beats. This phenomenon was observed in a 16-year-old boy who underwent electrophysiologic study for ventricular tachycardia as a late complication of surgical correction of tetralogy of Fallot. During pacing-induced ventricular tachycardia with a morphology similar to that of the spontaneous tachycardia, 8:4 alternating VA block was observed. This sequence suggested that the AV node was the site of block, the 2:1 block being located at the upper level, and the VA Wenckebach block at the lower level. Alternate VA Wenckebach conduction appears as a possible cause of variation in atrial depolarization intervals during ventricular tachycardias with short cycle lengths.

Adolescent↗
PubMed2003

The influence of spontaneous termination of atrial fibrillation on P wave-triggered signal-averaged electrocardiogram.

BACKGROUND: Prolongation of total filtered P wave duration (Ad) and low root mean square voltages for the last 20 ms of the P wave (LP20) on a P wave-triggered signal-averaged electrocardiogram (PSAECG) are typically observed in paroxysmal atrial fibrillation (PAF) patients. A shortening of atrial refractoriness and intra-atrial conduction delay (atrial remodeling) have been shown to occur in response to PAF. We, therefore, investigated the effects of spontaneous termination of PAF on the parameters of PSAECG. METHODS: We measured the Ad, LP20 and left atrial (LA) diameter by ultrasonic echocardiography before, within 1 h after, and 3 and 12 months after PAF termination in patients with no structural heart disease (n=11). RESULTS: The PAF duration was 16+/-5 h. The Ads before, within 1 h after, and 3 and 12 months after PAF were 137+/-4, 148+/-4, 137+/-6, and 135+/-7 ms, respectively. The Ad within 1 h after PAF was significantly (P<0.01) longer than at the other three acquisition points. Although the LP20 within 1 h after PAF termination was not significantly different from the other three points, the change in LP20 (within 1 h after PAF-before PAF, -1.1+/-0.4 microV) in the long PAF duration group was significantly (P<0.05) greater than that of the short PAF duration group. LA diameter was unchanged at all points. CONCLUSION: These data suggest that PAF results in prolongation of Ad after termination of PAF.

Aged↗
PubMed1975

Electrophysiologic characteristics of Ebstein's anomaly of the tricuspid valve.

Electrophysiologic characteristics of five patients with Ebstein's anomaly of the tricuspid valve were defined with studies using luminal intracardiac electrode catheters. The diagnosis was made in each case from clinical data and confirmed at cardiac catheterization by the presence of an atrialized right ventricular chamber with atrial mechanical activity and ventricular electrical activity. In three cases intra-right atrial conduction was prolonged (P-A intervals of 50, 50, and 65 msec), a finding which reflected the presence of a characteristically large right atrium. The bundle of His electrogram was recorded in its usual anatomical location. Atrioventricular nodal conduction was prolonged in only one case. Intra-His delay was observed in two cases (bundle of His duration of 30 and 30 msec). Infranodal conduction was prolonged in four cases with H-V intervals of 60, 65, 65, and 80 msec. The anatomical abnormalities were least severe in the only patient with a normal H-V interval (50 msec). The prolonged H-V interval was thought to result from stretching of the conduction system over the atrialized right ventricle (ARV). The late depolarization during the splintered R' of the electrocardiogram found during intracardiac mapping of the ARV in three patients confirms the theory that the ARV produces the "second QRS" typically seen in this anomaly. The ARV was particularly irritable, and ventricular fibrillation was produced in two patients during catheter manipulation in this area. In one case the ARV had a shorter refractory period than the body of the right ventricle. Re-entrant supraventricular tachycardia was induced in the only patient with Wolff-Parkinson-White syndrome. In addition to the previously recognized electrophysiologic features reconfirmed here, patients with Ebstein's anomaly of the tricuspid valve usually have: normal position of the bundle of His, prolonged intra- right atrial conduction, prolonged infranodal conduction, and irritable ARV with delayed activation.

Adolescent↗
PubMed1991

Role of concealed and supernormal conductions during atrial fibrillation in the preexcitation syndrome.

The hypothesis that retrograde concealed and anterograde supernormal conductions over the accessory pathway are determinants of anterograde accessory pathway conduction during atrial fibrillation (AF) was prospectively tested. For 17 patients during AF, 90 +/- 13 (mean +/- standard deviation) consecutive beats were analyzed for morphology and VV interval preceding each QRS complex. In 15 patients with both preexcited and normal QRS complexes, after normal complexes, the cycle length preceding the first preexcited QRS complex was 389 +/- 69 ms, which was longer than the average cycle length of consecutive preexcited complexes (325 +/- 55 ms; p = 0.001). The mean difference was 61 +/- 53 ms. After preexcited QRS complexes, the cycle length preceding the first normal QRS complex averaged 423 +/- 65 ms, which was significantly longer than the average cycle length of 345 +/- 47 ms between consecutively conducted normal QRS complexes (p less than 0.001). The mean difference was 86 +/- 45 ms. These findings suggest retrograde concealed conduction of normally conducted QRS complexes to the accessory pathway can affect anterograde conduction over the accessory pathway, and vice versa. In 2 patients with multiple accessory pathways, 1 accessory pathway conducted only after short preceding cycle lengths (355 to 360 and 181 to 185 ms), which was consistent with supernormal conduction. In conclusion, retrograde concealed conduction to the accessory pathway conduction are factors that, in part, determine accessory and anterograde supernormal accessory pathway conduction are factors that, in part, determine accessory pathway conduction during AF.

Atrial Fibrillation↗
PubMed1996

[The electrophysiological bases of aberrant intraventricular conduction during atrial fibrillation].

Twenty-four hours electrocardiogram from 4 patients with chronic atrial fibrillation and intraventricular aberrant conduction were analyzed. Aim of the study was to evaluate the reliability of the Ashman's and Akthar's rules in electrocardiographic differential diagnosis between aberrancy and ectopy. We computed parameters related to 10 RR interval preceding the aberrant conduction (AB+ Group), normal complex QRS (AB-Group) and ectopic QRS (E Group): coupling interval (CI), preceding CI cycle (PCL1), preceding PCL1 cycle (PCL2), the difference between PCL1 an PCL2 (delta PCL1), the difference between CI an PCL1 (delta CI), the mean value (RR10) and the standard deviation (RR10SD) of the 10 QRS complexes preceding the end of the sequence. Specificity of Akthar's rule was 48.7% (range 45-50%), sensibility was 90.1% (range 75-100%). PCL2, delta PCL1 and RR10DS were significantly different between AB+ and AB- Group but not between AB+, AB- and E Group. In this work Akthar's rule showed a better reliability than Ashman's rule but specificity was low (probably related to concealed conduction in atrio-ventricular node). RR10DS, but not RR10, were significantly higher in AB+ Group than AB- Group suggesting that acceleration of the cycle length can provoke CVA by increasing the difference between the refractory period of His bundle branches. Aberrant ventricular conduction cannot be determined by a mathematical rule. In the differential diagnosis of wide QRS during atrial fibrillation only morphological analysis of QRS and the study of coupling interval and compensatory pause are helpful.

Atrial Fibrillation↗
PubMed2004

Effects of ablation, digitalis, and beta-blocker on dual atrioventricular nodal pathways and conduction during atrial fibrillation.

INTRODUCTION: Modification of AV nodal conduction by radiofrequency ablation (RFA) results in a variable reduction in heart rate during atrial fibrillation (AF). Using AF induced in patients with dual AV nodal pathways as a model, we tested the effect of additional treatment with digitalis (ouabain) and beta-blocker (esmolol). METHODS AND RESULTS: Ten patients were randomized to control (group I) and studied only before ablation. AF was induced in 30 patients before and after slow pathway ablation (group II). Mean ventricular cycle lengths (AF CLmean) were recorded. Slow pathway conduction was eliminated after ablation in 10 patients (group IIA), whereas slow pathway conduction was still present in 20 patients (group IIB). Compared to pre-RFA there was a 10% increase in AF CLmean post-RFA (P < 0.01). During isoproterenol infusion the increase was 8% (P = NS). Adding digitalis and beta-blocker during isoproterenol infusion increased AF CLmean by 75% (95% in group IIA) compared to 36% in group I (P < 0.001 II vs I). CONCLUSION: Slow pathway ablation reduces ventricular rate during AF. Addition of digitalis and beta-blocker during isoproterenol infusion significantly decreases ventricular rate after ablation compared to the control group. The finding suggests that beta-blocker has significant effects on fast AV nodal pathway conduction during induced AF with isoproterenol infusion.

Adrenergic beta-Antagonists↗
PubMed1989

Effects of verapamil, diltiazem and disopyramide on sinus function: a comparison with bepridil.

Cardiac drugs known to affect sinus function mostly exhibit negative chronotropic activity. However, impulse conduction within the sinus node can also be influenced. Recently we studied the direct effects of bepridil on rabbit sinus function. It appeared that sinoatrial impulse conduction was depressed markedly with drug concentrations that did not affect sinus automaticity. In the present study the direct effects of verapamil, diltiazem and disopyramide on rabbit sinus function and atrial conduction properties were studied. Verapamil (8.8 x 10(-8) M) reduced the sinoatrial impulse conduction velocity by 35% and prolonged sinoatrial refractoriness by 36%. On the other hand, the sinus rate and atrial conduction parameters were hardly affected. Diltiazem (5 x 10(-6) M) exerted similar actions on the sinoatrial impulse conduction velocity and caused a simultaneous reduction in the sinus rate of 48%. Atrial conduction remained unaffected. Disopyramide (5 x 10(-5) M) depressed both the atrial and nodal conduction properties markedly, whereas the sinus rate was reduced moderately, by almost 20%. Thus, verapamil, diltiazem and disopyramide act differently on sinus function and atrial conduction, whereby the predominant effect of verapamil and diltiazem on sinoatrial conduction properties favours the occurrence of a sinus exit block.

Animals↗
PubMed2004

Reversal of electrical remodeling after cardioversion of persistent atrial fibrillation.

INTRODUCTION: In animals, atrial fibrillation results in reversible atrial electrical remodeling manifested as shortening of the atrial effective refractory period, slowing of intra-atrial conduction, and prolongation of sinus node recovery time. There is limited information on changes in these parameters after cardioversion in patients with persistent atrial fibrillation. METHODS AND RESULTS: Thirty-eight patients who had been in atrial fibrillation for 1 to 12 months underwent electrophysiologic testing 10 minutes and 1 hour after cardioversion. At 1 week, 19 patients still in sinus rhythm returned for repeat testing. Reverse remodeling of the effective refractory period was not uniform across the three atrial sites tested. At the lateral right atrium, there was a highly significant increase in the effective refractory period between 10 minutes and 1 hour after cardioversion (drive cycle length 400 ms: 204 +/- 17 ms vs 211 +/- 20 ms, drive cycle length 550 ms: 213 +/- 18 ms vs 219 +/- 23 ms, P < 0.001). The effective refractory period at the coronary sinus and distal coronary sinus did not change in the first hour but had increased by 1 week. The corrected sinus node recovery time did not change in the first hour but was shorter at 1 week (606 +/- 311 ms vs 408 +/- 160 ms, P = 0.009). P wave duration also was shorter at 1 week (135 +/- 18 ms vs 129 +/- 13 ms, P = 0.04) consistent with increasing atrial conduction velocity. CONCLUSION: The atrial effective refractory period increases, sinus node function improves, and atrial conduction velocity goes up in the first week after cardioversion of long-standing atrial fibrillation in humans. Reverse electrical remodeling of the effective refractory period occurs at different rates in different regions of the atrium.

Adaptation, Physiological↗
PubMed2006

Diurnal variation of the P-wave dispersion in chronic ischemic heart diseases.

OBJECTIVE: Electrocardiographic indices like maximum P-wave duration (P(max)) and P-wave dispersion (PD) can be used to detect patients with atrial conduction disorders, myocardial ischemia and those at risk for atrial fibrillation. Considering the diurnal variation of ischemia in patients with significant coronary lesions, this study was designed to investigate the diurnal variation of eventual atrial conduction abnormalities. METHODS: Forty-eight patients (31 male) with typical angina were grouped according to coronary angiography results as group 1 - 70% or more luminal reduction in at least one of the coronary arteries (n=28), and group 2 - normal coronary arteries (n=20). The difference between the P(max) and minimum P-wave durations (P(min)) is designated as PD. The diurnal P(max), P(min) and PD values were compared between and within the groups. RESULTS: The morning P(max) value of group 1 was significantly higher than the value of group 2 (112+/-1 vs. 102+/-1 ms, P<0.001). The morning PD of group 1 was significantly higher than that of group 2 (54+/-9 vs. 48+/-1 ms, P<0.05). The morning P(max) of group 1 (112+/-1 ms) was significantly higher than its afternoon (102+/-9 ms) and night (102+/-1 ms) values (P<0.001). The morning PD of group 1 (54+/-9 ms) was higher than the afternoon (40+/-10 ms) and night (43+/-9 ms) PD (P<0.001). No significant difference was observed between the P(max), P(min) and PD values in group 2 (P>0.05). CONCLUSION: This study demonstrated that coronary heart disease patients have higher morning P(max) and PD values that may be important regarding prediction of timing and treatment of atrial conduction disorders in myocardial ischemia.

Chronic Disease↗
PubMed1968

Disturbances in atrial rhythm and conduction following the surgical creation of an atrial septal defect by the Blalock-Hanlon technique.

Disturbances in atrial conduction or rhythm, or both, were found in 16 of 27 patients undergoing the surgical creation of an atrial septal defect by the Blalock-Hanlon technique. These included P-wave aberrations of intra-atrial block and ectopic atrial rhythm, A-V rhythm, A-V dissociation, sinus bradycardia, atrial flutter, escape-capture bigeminy, and atrial premature beats. Some of these were transient and occurred within 2 weeks after surgery. It seems likely that tissue trauma engendered by the clamp and resection of the atrial septum with possible injury to the internodal conducting pathways may be the genesis of these early postoperative disturbances. Of the eight cases with transient disturbances, six occurred in this period. Later changes, such as intra-atrial block, sinus bradycardia, and atrial flutter, may be attributed to changes in atrial size secondary to the postoperative pathophysiology. Digitalis intoxication and congestive heart failure cannot be excluded as contributory factors in either the early or the late disturbances. It was not possible to correlate the incidence and nature of these disturbances with morbidity and mortality. In such severely ill, cyanotic infants, irregularities, however slight, may have altered cardiac function significantly and contributed to their deaths.

Bradycardia↗
PubMed1996

Electrophysiologic differences in young patients with atrial fibrillation. Influence of preexcitation.

Paroxysmal atrial fibrillation is a common arrhythmia, which may occur in young patients without known structural heart disease, with or without preexcitation. Elimination of an accessory pathway in these patients may prevent not only orthodromic and antidromic tachycardia but also atrial fibrillation. However, abnormalities of atrial conduction and refractoriness have been reported, suggesting that atrial fibrillation may still recur in these patients. In a review of all electrophysiologic studies performed at the authors' institution since January 1990 in patients under age 60 years of age without identifiable heart disease, 24 patients with atrial fibrillation were identified whose electrophysiologic measurements of a right atrial conduction and effective refractory period of the right atrium and accessory pathway were in sinus rhythm. Of these patients, 12 had preexcitation and the other 12 did not. These patients were compared with age- and sex-matched control subjects, 12 with preexcitation without atrial fibrillation and 13 without preexcitation or atrial fibrillation, respectively. Electrophysiologic abnormalities were noted in patients with atrial fibrillation depending on the presence or absence of preexcitation. In patients with preexcitation, these abnormalities were a shorter refractory period of the right atrium (212 +/- 33 ms) and of the accessory pathway (251 +/- 27 ms), compared with control subjects (241 +/- 27 ms, P < .05 and 306 +/- 61 ms, P < .02, respectively). In patients without preexcitation, conduction abnormality in the form of prolonged atrial conduction time when compared with control subjects (48 +/- 26 ms vs 31 +/- 10 ms, P < .05) was noted. These findings may influence the type of antiarrhythmic drug used in these patients, and if confirmed in a larger study, they may lead to a better understanding of factors influencing the development of atrial fibrillation in young patients.

Adult↗
PubMed2001

Analysis of P wave and P dispersion in children with secundum atrial septal defect.

BACKGROUND: P maximum and P dispersion are evaluated as predictors of paroxysmal atrial fibrillation in adults. In this study, these variables are being investigated in children with secundum ASD in comparison with that of normal controls and in relation to size of ASD and the presence or absence of atrial dilation. METHODS: Ninety-four children with isolated secundum ASD (33 boys, 60 girls; mean +/- SD age at diagnosis 2.9 +/- 4.1 years) and 65 age-matched controls (mean +/- SD age 4.2 +/- 4.2 years) were evaluated. Resting 12-lead ECG was used to measure P waves from which P maximum and P dispersion (difference between maximum and minimum P-wave duration) were derived. ASD children were arbitrarily subgrouped according to ASD sizes (small: 1-3 mm, moderate: 4-7 mm, large: > or = 8 mm). The presence of right atrial dilation was noted from echocardiography. RESULTS: Children with ASD had significantly longer mean P dispersion compared to controls (P dispersion: 30.2 +/- 11.1 vs 26.4 +/- 6.6 ms, P = 0.008). Mean P maximum and P dispersion were significantly prolonged with increasing ASD size (P < 0.001). Children with right atrial dilation had significantly longer P maximum (102.3 +/- 15.2 vs 82.8 +/- 13.4 ms, P < 0.001) and larger P dispersion (36.1 +/- 12.5 vs 27.6 +/- 9.4 ms, P = 0.003) compared to those without right atrial dilation. CONCLUSION: Prolonged atrial conduction time and inhomogeneity of atrial conduction may possibly be present in children with moderate to large sized ASD and in those with atrial dilation.

Analysis of Variance↗
PubMed1985

[A method of computer-assisted evaluation of programmed single stimulation for determination of sinoatrial conduction time].

The determination of the sino-atrial conduction time by means of premature individual atrial stimulation is an important partial function in the intracardial sino-atrial functional test and a reasonable parameter in selected diagnostic questions for the clarification of syncopic conditions under suspicion of a sick-sinus syndrome. In order to alleviate the clinical use and to reduce the considerable expenditure of time in the calculation of the results for the determination of the sino-atrial conduction time by about 60% a computerized evaluation method was elaborated. This methodology resulted in an exoneration from the manual graphic-calculatory expenditure and in comparison to the traditional calculation method it did not show any statistically significant differences.

Computers↗
PubMed2000

Prevention of the initiation of atrial fibrillation: mechanism and efficacy of different atrial pacing modes.

Several atrial pacing modes have been reported to be effective in the prevention of atrial fibrillation (AF); they included biatrial pacing, dual site right atrial pacing, Bachmann's bundle (BB) pacing, and coronary sinus pacing. However, the relative efficacy and electrophysiological mechanisms of these pacing modes in the prevention of AF are not clear. In 15 patients (age 54 +/- 14 years) with paroxysmal AF, P wave duration, effective refractory period, and atrial conduction time were determined with six different atrial drive pacings, that were right atrial appendage (RAA), BB, right posterior interatrial septum (RPS), distal coronary sinus (DCS), RAA plus RPS simultaneously (DSA), and RAA plus DCS simultaneously (BiA). All these patients consistently had AF induced with early RAA extrastimulation coupling to RAA drive pacing. No patient had AF induced with RAA extrastimulation coupled to BB, RPS, or DCS drive pacing, but seven and eight patients had AF induced with RAA extrastimulation coupled to DSA and BiA drive pacing, respectively. The P wave duration was longest during RAA pacing, and became shorter during other atrial pacing modes. Analysis of electrophysiological change showed that early RAA extrastimulation coupled to RAA drive pacing caused the longest atrial conduction delay among these atrial pacing modes; BB, RPS, and DCS drive pacing caused a greater reduction of this conduction delay than DSA and BiA drive pacing. In addition, the effective refractory periods of RAA determined with BB, RPS, and DCS drive pacing were similar and longer than that determined with DSA and BiA drive pacing. In patients with paroxysmal AF, this arrhythmia was readily induced with RAA extrastimuli coupled to RAA drive pacing. BB, RPS, and DCS pacing were similar and more effective than DSA and BiA pacing in preventing AF.

Adolescent↗