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PubMed2002

Effect of low-dose isoproterenol infusion on left atrial appendage function soon after cardioversion of chronic atrial tachyarrhythmias.

BACKGROUND: Cardioversion of chronic atrial fibrillation or atrial flutter to sinus rhythm is often associated with transient atrial mechanical dysfunction, i.e. 'atrial stunning', which may increase the risk of subsequent thromboembolic events. We hypothesized that, because of its positive inotropic action, a low-dose isoproterenol infusion might improve postcardioversion atrial mechanical function. METHOD: Eighteen patients (15 male, three female; 12 atrial fibrillation, six atrial flutter; mean age 65+/-10 years) exhibiting atrial postcardioversion stunning were included in the study. Isoproterenol was infused for 10 min at a dose sufficient to increase the heart rate by about 10%. Using transesophageal echocardiography, both the left atrial appendage emptying/filling flow velocity and function (fractional area change) were examined at baseline, before isoproterenol (immediately after cardioversion) and after isoproterenol. RESULTS: With infusion of 0.005-0.008 microg/kg/min isoproterenol, heart rate increased by 11.1+/-2.9%, and left atrial appendage emptying velocity, which was diminished following cardioversion, increased significantly (P<0.001) (baseline, before and after isoproterenol: 41.1+/-18.0, 20.3+/-8.5 and 27.3+/-9.6 cm/s, respectively). No major complications were associated with isoproterenol infusion. CONCLUSIONS: Short-term infusion of low-dose isoproterenol improved atrial function after cardioversion of chronic atrial fibrillation and atrial flutter.

Aged↗
PubMed1994

Incompetence of the foramen ovale in preterm infants supported by mechanical ventilation.

Fifty-one preterm infants (< 1500 gm) who were supported by mechanical ventilation were studied by use of serial color Doppler echocardiography to determine the hemodynamic impact of incompetence of the foramen ovale. Right and left ventricular stroke volume, measured by two-dimensional and Doppler echocardiography, were used to determine the ratio of pulmonary to systemic flow (Qp/Qs). The diameter of the color flow mapping of any interatrial shunt was measured together with pattern and velocity of that shunt. Ductal patency status was established. Most infants had some atrial shunting. The dominant direction of shunting was left to right within a bidirectional shunt pattern (75%). When the ductus was closed, there was a significant correlation between color Doppler diameter of the atrial shunt and Qp/Qs (r = 0.71). When this diameter was less than 2 mm, there was minimal impact on Qp/Qs. Measurable effects on Qp/Qs were usually seen at diameters > 3 mm when Qp/Qs ratios of up to 2:1 were recorded. Longitudinally, atrial shunting could be divided into four groups. Group 1 (n = 23) had minimal shunt or small shunts (< 3 mm) that resolved early, group 2 (n = 11) had small shunts that persisted, group 3 (n = 9) had large shunts (> 3 mm) that resolved, and group 4 (n = 6) had large shunts that persisted. Clinically there were no significant differences between the groups except that patients in groups 2 to 4 tended to having worse acute lung disease than patients in group 1 and had significantly more chronic lung disease. We conclude that many preterm infants have left-to-right atrial shunts that have a noninvasively measurable hemodynamic impact. This may have an effect on acute and chronic respiratory outcome and is likely to affect assessments of ductal shunting.

Atrial Function, Left↗
PubMed1991

The relationship between atrial pressure, atrial dimensions and atrial natriuretic factor during pacing tachycardia in dogs.

Acute supraventricular tachycardia is known to increase the plasma level of atrial natriuretic factor (ANF). The purpose of these experiments was to investigate if such an increase in plasma-ANF could be ascribed to changes in atrial pressure and atrial dimensions. Eight anaesthetized dogs were instrumented with atrial pressure catheters and sonomicrometers to measure left and right auricular and atrial free wall dimensions. An acute increase in atrial rate from 150 to 200 min-1 for 10 min did not change plasma-ANF or atrial haemodynamic variables. A further increase in atrial rate to 250 or 300 min-1 increased right and left atrial intracavitary pressures (P less than 0.01), both auricular diameters and right atrial free wall segment length (P less than 0.05). Left atrial free wall segment length remained unchanged. Plasma-ANF increased in all dogs (P less than 0.01). The change in plasma-ANF correlated well with changes in atrial pressures as well as with changes in atrial dimensions. These results support the hypothesis that release of ANF during acute atrial tachycardia may in part be attributed to atrial dilatation.

Animals↗
PubMed1995

Premature atrial beat eliciting atrial fibrillation after coronary artery bypass grafting.

Of patients undergoing coronary artery bypass grafting 30% develop atrial fibrillation (AF) or flutter. To determine if AF is initiated from the right or left atrium, atrial electrograms were continuously recorded in patients undergoing this procedure. In addition, to study whether the prematurity index of premature atrial contractions (PACs) eliciting AF differs from PACs not provoking AF, the distribution of prematurity indices was evaluated from R-R interval analysis. The right and left atrial recording electrodes were first activated by the ectopic beat provoking AF in six and eight patients, respectively. The prematurity index of the PAC eliciting AF was located in the middle (in half of the patients) or to the left of the median distribution of prematurity indices. The variability in activation of the atrial electrodes suggests that the PAC provoking AF can have its origin in the right, the septal, or the left region of the atrium. The initiation of AF depends on the prematurity index of the PAC.

Atrial Fibrillation↗
PubMed1993

Nonuniformity of AH intervals during stimulation at different left atrial sites.

Studies in humans have found left atrial stimulation via the coronary sinus (CS) to elicit significantly shorter atrium-His (AH) intervals as compared to right atrial stimulation, but whether pacing at different left atrial sites (anterior vs posterior left atrium, i.e., far distal vs proximal CS) affects the AH interval has not been studied. Hence, in 22 patients, we compared the effects of stimulation from various atrial sites, including anterior high right atrium (HRA), distal CS, mid-CS, and proximal CS, on: stimulus-atrium (SA), AH, and stimulus-His intervals on the His bundle electrogram. Paced cycle length differed for each patient (range 900-350 msec, mean 532 +/- 140 msec), but conduction intervals from different atrial sites were compared using identical cycle length in each patient. The mean SA intervals were 34 +/- 10 msec, 57 +/- 10 msec, 44 +/- 11 msec, and 32 +/- 8 msec with stimulation, respectively, from HRA, distal CS, mid-CS, and proximal CS (each significantly different except for HRA vs proximal CS). The mean AH intervals were 123 +/- 23 msec, 104 +/- 28 msec, 95 +/- 15 msec, and 90 +/- 18 msec with stimulation, respectively, from HRA, distal CS, mid-CS, and proximal CS (each significantly different except for mid-CS vs proximal CS). In 13 patients, the discrepancy in AH intervals during distal versus proximal CS stimulation was > or = 15 msec; in 9 patients this difference was only < or = 10 msec, considered within the range of measurement error. Thus, in a significant portion of patients, discrepant AH intervals were demonstrated during stimulation from the distal versus proximal CS. These previously undescribed observations suggest that electrophysiological studies on atrioventricular nodal conduction that involve left atrial stimulation must take into account actual location of the stimulation site (anterior or posterior) in order to properly interpret the findings.

Adolescent↗
PubMed2005

Comparison of tissue Doppler dynamics to Doppler flow in evaluating left atrial appendage function by transesophageal echocardiography.

Tissue Doppler imaging (TDI) patterns from the left atrial appendage (LAA) were evaluated by transesophageal echocardiography. Reproducible, characteristic triphasic or biphasic tissue velocities similar to Doppler flow of the LAA were obtained. Patient peak TDI velocities correlated well with flow and were measurable in atrial fibrillation. Patients with an embolic cerebrovascular accident and in sinus rhythm had higher tissue TDI velocities from the LAA compared with patients without an event, and the groups had similar flow velocities. Hence, Doppler tissue contraction dynamics determined by TDI may complement flow velocities in evaluating LAA function for risk assessment of thromboembolism.

Adult↗
PubMed1997

Hemodynamic changes after cardioversion of chronic atrial fibrillation.

After cardioversion of chronic atrial fibrillation to sinus rhythm, there is a gradual increase of 56% in cardiac output over 4 weeks. The increase is caused by the gradual return and increasing strength of left atrial mechanical activity as the atrial myopathy of chronic atrial fibrillation subsides. Cardiac output decreases after cardioversion of atrial fibrillation in more than a third of patients, and the decrease may last a week. Acute pulmonary edema is uncommon; 50% of cases occur within 3 hours of cardioversion, with a mortality of 18%. The reduced cardiac performance after cardioversion most likely results from the combination of heart disease and cardiac depressant effects of anesthetic drugs used. Pulmonary and/or coronary artery emboli and the resumption of right atrial mechanical activity before left atrial mechanical activity may be additional factors in the pathogenesis of pulmonary edema after cardioversion. Anticoagulant therapy should be continued for a month or longer after cardioversion in those patients who maintain sinus rhythm to prevent thromboembolism.

Anesthetics↗
PubMed1994

Impaired left atrial mechanical function after cardioversion: relation to the duration of atrial fibrillation.

OBJECTIVES: We hypothesized that the time course of the recovery of atrial systolic function may be related to the duration of atrial fibrillation before cardioversion and sought to study noninvasively the recovery of left atrial mechanical function utilizing serial transthoracic Doppler studies. BACKGROUND: Recovery of atrial mechanical function may be delayed for several weeks after successful cardioversion of atrial fibrillation to sinus rhythm. METHODS: After successful cardioversion, 60 patients with atrial fibrillation of brief (< or = 2 weeks, 17 patients), moderate (> 2 to 6 weeks, 22 patients) or prolonged (> 6 weeks, 21 patients) duration were followed up with serial transmitral pulsed Doppler echocardiography immediately (60 patients) and at 24 h (45 patients), 1 week (41 patients), 1 month (31 patients) and > 3 months (30 patients) after cardioversion. RESULTS: Atrial mechanical function is greater immediately and at 24 h and 1 week after cardioversion in patients with "brief" compared with "prolonged" atrial fibrillation. In all groups, atrial mechanical function increases over time, ultimately achieving similar levels. Full recovery of atrial mechanical function, however, is achieved within 24 h in patients with brief atrial fibrillation, within 1 week in patients with moderate-duration atrial fibrillation and within 1 month in patients with prolonged atrial fibrillation. CONCLUSIONS: Recovery of left atrial mechanical function is related to the duration of atrial fibrillation before cardioversion. These findings have important implications for assessing the early hemodynamic benefit of successful cardioversion.

Adult↗
PubMed1993

Effects of atrial fibrillation on left and right atrial dimensions, pressures, and compliances.

The effects of atrial fibrillation on left and right atrial dimensions, pressures, and compliances were examined in two groups of seven barbiturate-anesthetized open-chest pigs. Atrial diameters and pressures were recorded during atrioventricular (AV) pace and thereafter during atrial fibrillation. Both rhythms were studied with constant ventricular rate after complete AV block. Left atrial maximal diameter, which appeared at the end of the atrial filling phase, decreased from 32.4 (28.9-36.7; median and 95% confidence interval) to 31.3 (28.4-35.7) mm after induction of atrial fibrillation. The right atrial maximal diameter also decreased, although not significantly. Atrial pressure at the peak of the v wave rose from 7.0 (5.5-8.5) to 9.6 (8.3-11.2) mmHg in the left atrium and from 5.0 (4.3-5.6) to 7.3 (6.2-8.7) mmHg in the right atrium. Left and right atrial chamber stiffness constants increased from 0.25 (0.19-0.48) to 0.41 (0.28-0.66) mm-1 and from 0.21 (0.11-0.31) to 0.33 (0.30-0.39) mm-1, respectively. Instantaneous diastolic atrial compliance decreased in both atria after induction of atrial fibrillation. Thus, during atrial fibrillation with regular ventricular rate, changes in atrial diameter, pressure, and compliance take place.

Animals↗
PubMed1991

Assessment of left atrial appendage function by transesophageal echocardiography. Implications for the development of thrombus.

BACKGROUND: The predilection of the left atrial appendage (LAA) for thrombus formation has long been known. METHODS AND RESULTS: We prospectively studied the two-dimensional echocardiographic and Doppler patterns of LAA function in 82 patients by transesophageal echocardiography. In the 63 patients in sinus rhythm, LAA area was measured during LAA diastole at the onset of the electrocardiographic (ECG) P wave (LAAmax) and after LAA systole at the ECG R wave (LAAmin) and LAA ejection fraction was calculated as (LAAmax-LAAmin)/LAAmax; peak Doppler velocity was recorded from the LAA outlet. The 58 patients in sinus rhythm without LAA thrombus were grouped according to left atrial size on transthoracic echocardiography; 39 patients had a left atrial size of less than 40 mm (group 1) and 19 had a left atrial size of 40 mm or greater (group 2). Five patients in sinus rhythm had LAA thrombus. In the 19 patients with atrial fibrillation or flutter LAAmax was measured independent of the ECG; three of these patients had LAA spontaneous contrast, four had thrombus, and one had both. Patients in sinus rhythm without LAA thrombus demonstrated a characteristic pattern of a contractile LAA apex and a noncontractile base with color flow and pulsed Doppler evidence of LAA emptying that coincided with the P wave. Patients in sinus rhythm with LAA thrombus had a mean +/- SD LAAmax (8.0 +/- 1.5 cm2) larger than that in group 1 (5.0 +/- 1.9 cm2) (p less than 0.01) but not group 2 (6.7 +/- 3.1 cm2), LAAmin (6.5 +/- 1.0 cm2) larger than that in both group 1 (2.3 +/- 1.5 cm2) and group 2 (4.2 +/- 2.7 cm2) (p less than 0.01), and LAA ejection fraction (17 +/- 11%) and LAA velocity (0.24 +/- 0.10 m/sec) less than those in both group 1 (55 +/- 21% and 0.48 +/- 0.24 m/sec, respectively) and group 2 (45 +/- 27% and 0.46 +/- 0.24 m/sec, respectively) (p less than 0.01). Patients with atrial fibrillation or flutter with LAA spontaneous contrast and/or thrombus had LAAmax (10.4 +/- 6.6 cm2) greater than that in patients with atrial fibrillation or flutter without LAA contrast and/or thrombus (6.8 +/- 3.0 cm2) (p less than 0.05). The LAA appeared as a static pouch in seven of eight of the former compared with in two of 11 of the latter. When attempted, Doppler demonstrated a recognizable fibrillatory LAA outflow velocity pattern in none of three in the former versus four of seven in the latter group. CONCLUSIONS: We conclude that the LAA has a characteristic pattern of emptying in sinus rhythm. LAA thrombus formation in sinus rhythm and atrial fibrillation is associated with both poor LAA contraction and LAA dilation.

Adult↗
PubMed2004

Abnormal maternal cardiac function precedes the clinical manifestation of fetal growth restriction.

OBJECTIVE: To compare maternal hemodynamics in women whose fetuses are small-for-gestational age (SGA) with those in women with fetal growth restriction (FGR) before manifestation of the clinical disease. METHODS: Thirty-five normotensive pregnant women with fetal abdominal circumference < 10th centile, normal fetal anatomy and normal umbilical artery pulsatility index (PI) underwent maternal echocardiographic examinations between 27 and 30 weeks of gestation. Pregnancies were followed until delivery and fetuses were retrospectively classified as either SGA or FGR and the maternal hemodynamic data were compared. RESULTS: Nineteen SGA and 16 FGR patients were retrospectively identified after delivery. Heart rate, stroke volume, cardiac output, left atrial function and left ventricular mass index were higher, while mean blood pressure and total vascular resistance were lower in the SGA group compared with the FGR group. A significant inverse linear correlation was found between total vascular resistance and weight centile (r = 0.83; P < 0.0001). CONCLUSIONS: Mothers of SGA fetuses show hemodynamic features similar to those with physiological pregnancies suggesting that their fetuses are likely to be constitutionally small and not pathologically growth-restricted.

Adult↗
PubMed2002

Bi-atrial mapping of atrial arrhythmias.

Cardiac mapping of atrial activation was originally performed in animals during open chest preparations, using epicardial electrodes. The development of endocardial egg-shaped multiple electrodes provided detailed assessment of the minimum number of wavelengths required to sustain atrial fibrillation (AF), as well as the role of interatrial connections during AF. Subsequently, several studies on bi-atrial epicardial high-density mapping in animals and humans also reported on the importance of interatrial connections, as well as the specific characteristics of the left atrium as compared with the right atrium during chronic AF. Endocardial bi-atrial mapping studies using electrode catheters were reported using basket-shaped catheters carrying 64 electrodes. Animal studies suggested that septal activation was asynchronous and discordant, while a human study outlined the multiple origins of atrial ectopic beats following DC cardioversion in patients with chronic atrial fibrillation. The advent of non-fluoroscopic mapping systems significantly changed our approach to percutaneous endocardial mapping. Simultaneous bi-atrial studies using electroanatomic mapping were performed in sinus rhythm as well as in atrial flutter. These studies demonstrated the predominance of interatrial conduction over Bachmann's Bundle and the coronary sinus-left atrial connection during respectively, sinus rhythm and atrial flutter. Simultaneous bi-atrial non-contact mapping was initially performed during porcine studies and later in humans, demonstrating asynchronous and discordant septal activation both during sinus rhythm or left lateral atrial pacing. Preliminary studies from simultaneous bi-atrial non-contact mapping in humans in whom AF occurred spontaneously or was induced suggests three main types of atrial activation, consisting of left atrial drivers causing the right atrium to fibrillate following conduction over interatrial connections, the right atrium independently sustaining AF, even after pulmonary vein disconnection, and both atria fibrillating independently without activation over interatrial connections. Bi-atrial mapping has been essential for our understanding of normal and abnormal atrial activation, and ultimately may provide new approaches for ablation of atrial fibrillation.

Animals↗
PubMed1993

Significance of increased atrial pressure on stroke volume during atrial fibrillation in anaesthetized pigs.

During atrial fibrillation synchronized atrial contraction is lost and cardiac output declines. Concomitantly, atrial pressure increases. The significance of the increase in atrial pressure on stroke volume was examined before and after blood volume expansion. Atrial fibrillation was induced by rapid atrial pacing in seven anaesthetized, open-chest pigs. The increase in right atrial pressure subsequently was counteracted by an appropriate constriction of the inferior vena cava. To avoid the confounding effect of a rapid and irregular heart rate, ventricular rate was kept constant by separate His bundle pacing after complete atrioventricular block. When atrial fibrillation was induced, right and left atrial pressure at the top of the v-wave increased both during normovolaemia and during hypervolaemia. Concomitantly, stroke volume declined. When the increase in atrial pressure was prevented during atrial fibrillation, stroke volume declined further: by 35 (21-50) and 9 (2-17)% (difference: P = 0.01), during normo- and hypervolaemia, respectively. Thus, the increase in atrial pressure counteracts the decline in stroke volume after induction of atrial fibrillation and thereby represents an important compensatory mechanism. This mechanism is more important with normal blood volume than during hypervolaemia.

Animals↗
PubMed1996

Effect of pneumoperitoneum on interatrial pressure gradient during laparoscopic cholecystectomy.

Alterations of the left atrial/right atrial pressure gradient were determined using a Swan-Ganz thermodilution catheter in 20 patients who underwent laparoscopic cholecystectomy with 12 mmHg pneumoperitoneum (LAP) and 13 patients who underwent minilaparotomy cholecystectomy (MINI). Right and left atrial pressures were both elevated by pneumoperitoneum. A diminished or reversed left/right interatrial pressure gradient was recognized during pneumoperitoneum in 4 of the 20 patients (20%) in the LAP group, whereas it was not recognized during operation in any of the 13 patients in the MINI group. Evaluation of the elevation of intrathoracic pressure during pneumoperitoneum using peak inspiratory airway pressure or pulmonary arterial pressure could not predict the occurrence of this paradoxical interatrial pressure gradient.

Atrial Function, Left↗
PubMed1995

Atrial pressure and experimental atrial fibrillation.

A possible profibrillatory effect on the atria of an elevated atrial pressure and the site of atrial stimulation was examined. In 15 anesthetized dogs, right or left atrial or biatrial pacing was applied at a high rate (300-600/min) for 5 seconds at double threshold intensity under a wide range of atrial pressures achieved by venous or arterial transfusion or bleeding. Induction of atrial fibrillation in 236 of 1,971 pacing runs was associated with a significantly higher (P < 0.001) atrial pressure (21.6 +/- 12.2 mmHg, mean +/- SD) than maintenance of sinus rhythm (16.8 +/- 11.1 mmHg in 1,735 of 1,971 pacing runs). Stimulation of the right atrium resulted in atrial fibrillation more frequently than left atrial or biatrial stimulation, with biatrial stimulation less frequent than right or left atrial stimulation. The induction of atrial fibrillation was related to the atrial pressure and to the site of stimulation but not to the pacing rate or the prepacing heart rate. The prepacing heart rate, associated with failure to induce sustained atrial fibrillation, was higher than that associated with atrial fibrillation in 12 of 15 experiments (significantly in 6) and not significantly lower in 3 of 15. Atrial fibrillation lasting 1 minute or more was more frequently associated with simultaneous stimulation of both atria than of either atrium alone. Thus, an elevated atrial pressure may facilitate the induction of atrial fibrillation. The site of stimulation also plays an important role for both the induction and maintenance of atrial fibrillation in this model.

Animals↗
PubMed1998

Atrial electrical remodeling by rapid pacing in the isolated rabbit heart: effects of Ca++ and K+ channel blockade.

INTRODUCTION: Electrical remodeling describes atrial electrophysiologic changes that occur following atrial fibrillation. The mechanism(s) responsible for this phenomenon is not well understood. The purpose of this study was to examine the effects of rapid atrial pacing on atrial action potential duration, conduction time and refractoriness in the isolated rabbit heart. The effects of Ca++ and K+ blockade in this model were also studied. METHODS AND RESULTS: Monophasic action potential recordings were made from 12 epicardial atrial sites in 50 isolated perfused rabbit heart preparations. These recordings were analyzed for activation time (AT), 90% action potential duration (APD) and conduction times (CT) measured at a 250 msec cycle length. Atrial effective refractory periods (ERP) were determined at a 200 msec cycle length. All measurements were made at baseline and repeated after 2 hours of biatrial pacing at 250 msec (control group, n = 10) or 2 hours of rapid biatrial pacing (approximately 80 msec) in 4 groups: rapid pacing alone (rapid pacing group); rapid pacing in the presence of 0.1 mM verapamil (verapamil group) for L-type Ca++ channel blockade; rapid pacing with 1 mM 4-aminopyridine (4-AP group) for K+ channel blockade; and rapid pacing with 50 microM nickel chloride (Ni++ group) for T-type Ca++ channel blockade (n = 10 each group). All baseline and post pacing measurements were taken in the presence of Ca++ or K+ blockers for the respective groups. After rapid atrial pacing alone the average APD shortened by 8.2 +/- 10.4 msec compared to 3.6 +/- 12.5 msec shortening for control group (p = 0.002). The shortening of APD was uniform at all recording sites. For the rapid pacing group, CT was unchanged for right to left atrial conduction but shortened significantly for left to right atrial conduction (26.8 +/- 1.9 msec at baseline to 22.3 +/- 4.1 msec post pacing, p = 0.005). Conduction times were unchanged in the control group. The dispersion of repolarization was unchanged by rapid pacing alone. The decrease in APD from baseline to post rapid pacing was similar to the control group for those hearts treated with verapamil and 4-AP (1.5 +/- 12.3 and 4.7 +/- 10.4 msec, respectively, both p > or = 0.18 vs control group). The decrease in APD was significantly greater for the Ni++ group (11.8 +/- 14.3 msec) than for either the control group or rapid pacing group (both p < or = 0.023). The dispersion of repolarization was increased only in the 4-AP group post rapid pacing (41.7 +/- 6.2 msec at baseline to 53.5 +/- 9.6 msec post pacing, p = 0.01). ERPs were unchanged in any of the 5 groups except for a decrease in left atrial ERP in the Ni++ group after rapid pacing (98 +/- 14 msec at baseline to 88 +/- 8 msec post rapid pacing, p = 0.005). CONCLUSIONS: In the isolated rabbit heart model: 1) atrial APD is shortened after rapid pacing; 2) the shortening of APD is attenuated by verapamil and 4-AP but exaggerated by Ni++; 3) atrial conduction times are shortened in a direction specific manner after rapid pacing; and 4) shortening of ERP in this model is measured only in the presence of Ni++. These findings suggest that both L-type Ca++ and 4-AP sensitive channels may participate in atrial electrical remodeling.

4-Aminopyridine↗
PubMed1999

Atrial involvement in patients with progressive systemic sclerosis: relationship between ultrasonic tissue characterization of the atrium and interatrial conduction.

OBJECTIVE: The aim of this study was to assess atrial lesions using ultrasonic tissue characterization and to determine the contribution of atrial lesions to the interatrial electromechanical coupling conduction time in patients with progressive systemic sclerosis (PSS). METHODS: Twenty patients with PSS and 20 age-matched healthy controls were evaluated. The cyclic variation in integrated backscatter value (CV-IB) was measured at the interatrial septum (IAS) from apical four chamber view. M-modes of ventricular long axis motion along with phono- and electrocardiograms were recorded simultaneously at the right lateral (RT) and left lateral (LT) sites of the atrioventricular (AV) rings and central fibrous body (CFB) in the apical four-chamber view. Intervals from the P wave on ECG to the echocardiographic onset of atrial contraction as a point of inflection in long axis M-mode echocardiogram were measured at the RT and LT sites of AV rings and CFB (P-RT, P-LT, P-SEP, respectively). Interatrial electromechanical coupling conduction time was determined as [(P-LT) - (P-RT)]. RESULTS: In patients with PSS compared to normal controls, P-RT, P-SEP, P-LT, and interatrial conduction time were greater, while CV-IB in IAS decreased. Furthermore, CV-IB in IAS correlated well with interatrial conduction time (r = 0.7, p < 0.01) in patients with PSS. CONCLUSIONS: Interatrial electromechanical coupling times may be prolonged due to atrial tissue damage in patients with PSS.

Adult↗
PubMed1996

A new method for analysis of atrial activation during chronic atrial fibrillation in man.

To further clarify the mechanisms maintaining chronic atrial fibrillation (CAF), a method identifying preferable activation patterns of the atria during fibrillation, by time averaging of multiple discrete excitation vectors, was developed. Repeated recordings, each of 56 atrial bipolar electrograms simultaneously acquired during 8 s, were made at multiple sites in the right atrial free wall and the left atrial appendage in 16 patients with CAF using a 2.17 x 3.54 cm electrode array. The local activation times (LAT's) in each recording were estimated as the median activation time at the respective measurement point. By calculating the time difference between the LAT's at adjacent measurement points in two spatial dimensions, a direction vector was created for each activation wave passing each set of measurement points, a total of 42 sets. By time averaging of the individual direction vectors (typically n = 55) at each set of measurement points, preferable activation patterns were determined. Three types of activation patterns were found: 1) inconsistent activation (n = 5), 2) consistent activation with preferential propagation directions (n = 7) and 3) consistent activation with impulses originating from a localizable site within the recording area (n = 4). All activation patterns were reproducible and the two latter patterns were proven significant using statistical tests. We conclude that this new method is useful in further clarification of the mechanisms involved in the maintenance of atrial fibrillation.

Aged↗