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PubMed2003

Color Doppler tissue imaging to evaluate left atrial appendage function in mitral stenosis.

Two-dimensional color Doppler tissue imaging (CDTI) has so far been used, in general, to evaluate ventricular function. This study examined if the left atrial appendage tissue velocity could reproducibly be measured with CDTI and if they have any predictive value for left atrial appendage (LAA) function and former thromboembolism. Thirty-six patients (24 women, 12 men; mean age 45 +/- 12 years; 18 AF; 11 former thromboembolic stroke) with mitral stenosis undergoing transesophageal echocardiography were examined with CDTI. Peak systolic tissue velocity (m/sec, peak systolic velocity [PSV]) was measured at the tip of the LAA in the basal short-axis view. LAA flow emptying (LAAEV) and filling (LAAFV) velocities (m/sec) were also recorded 1 cm immediately below the orifice of the appendage. Interobserver and intraobserver variabilities were determined for the PSV. LAA ejection fraction was measured by Simpson's method. Mitral regurgitation, AF, transmitral mean gradient, left ventricular ejection fraction, mitral valve area, and left atrial diameter were used as a covariant for adjustment. The intraobserver and interobserver correlation coefficients for the PSV using CDTI was 0.64 and 0.60, respectively (bothP = 0.01). LAAEV(0.29 +/- 0.09 vs 0.19 +/- 0.04, P = 0.001)and LAA ejection fraction(44 +/- 12 vs 29 +/- 14, P = 0.004)were found to be significantly decreased in the patients with decreased PSV (<0.05 m/sec), even after adjustment. The decreased PSV was positively correlated with the low LAAEV (<0.25 m/sec) and history of thromboembolism (r = 0.59, r = 0.38, respectively), and remained a significant determinant of the low LAAEV (OR 50.03, CI 1.46-1738.11,P = 0.02), but not of history of thromboembolism (OR 4.29, CI 0.52-35.01,P = 0.08) after adjustment. In conclusion, these results suggest that CDTI provides a reproducible method for quantification of contraction at the tip of the LAA. Decreased PSV may be predictive of poor LAA function.

Adult↗
PubMed1988

Effects of left ventricular dysfunction on left atrial performance in previous myocardial infarction and during pacing-induced myocardial ischemia in angina pectoris.

This study aimed to evaluate acute and chronic response of left atrial function to left ventricular dysfunction in patients with coronary artery disease. We studied simultaneous measurements of left atrial volume by biplane cineangiography and left ventricular pressure at rest and after pacing in 59 patients with coronary artery disease and 11 normal subjects. At rest, 35 patients with previous myocardial infarction (MI group) had low left ventricular filling rate of the first third in diastolic time, large left atrial volume before contraction (LA pre-ACV) and large left atrial ejection volume (LAEV), compared with control group. Left atrial ejection fraction (LAEF), the ratio of LAEV to LA pre-ACV, was similar between both groups. LAEF was maintained within a wide range of values in accordance with left ventricular peak A pressure, except for 3 patients who had high values of left ventricular peak A pressure and low values of LAEF. After a right atrial pacing stress test, time constant was prolonged and mean emptying rate of left atrial volume during early diastole decreased in 11 patients with angina pectoris who had an increase greater than 5 mmHg in left ventricular end-diastolic pressure after pacing. In these group, LA pre-ACV increased, LAEF decreased and LAEV was unchanged. These results suggest that left atrial performance responds differently to acute and chronic left ventricular dysfunction in patients with coronary artery disease.

Angina Pectoris↗
PubMed2004

Left atrial conduit volume is generated by deviation from the constant-volume state of the left heart: a combined MRI-echocardiographic study.

Although modeling the four-chambered heart as a constant-volume pump successfully predicts causal physiological relationships between cardiac indexes previously deemed unrelated, the real four-chambered heart slightly deviates from the constant-volume state by ventricular end systole. This deviation has consequences that affect chamber function, specifically, left atrial (LA) function. LA attributes have been characterized as booster pump, reservoir, and conduit functions, yet characterization of their temporal occurrence or their causal relationship to global heart function has been lacking. We investigated LA function in the context of the constant-volume attribute of the left heart in 10 normal subjects using cardiac magnetic resonance imaging (MRI) and contemporaneous Doppler echocardiography synchronized via ECG. Left ventricular (LV) and LA volumes as a function of time were determined via MRI. Transmitral flow, pulmonary vein (PV) flow, and lateral mitral annular velocity were recorded via echocardiography. The relationship between the MRI-determined diastolic LA conduit-volume (LACV) filling rate and systolic LA filling rate correlate well with the relationship between the echocardiographically determined average flow rate during the early portion of the PV D wave and the average flow rate during the PV S wave (r = 0.76). We conclude that the end-systolic deviation from constant volume for the left heart requires the generation of the LACV during diastole. Because early rapid filling of the left ventricle is the driving force for LACV generation while the left atrium remains passive, it may be more appropriate to consider LACV to be a property of ventricular diastolic rather than atrial function.

Atrial Function, Left↗
PubMed1994

Clinical implications of left atrial appendage function: its influence on thrombus formation.

This study evaluated the relation between left atrial appendage (LAA) function and LAA spontaneous echo contrast (SEC) or thrombus formation. Seventy-five patients (45 men and 30 women, aged 14-79 years) referred for transesophageal echocardiography (TEE) were examined for LAA area (maximal and minimal), LAA ejection fraction ([LAA maximal area--LAA minimal area]/LAA maximal area), LAA peak emptying velocity, and these patients were classified into three groups by different LAA blood flow patterns: Group 1--25 patients with well-defined biphasic configuration of LAA flow; Group 2--28 patients with multiphasic configuration of LAA flow; Group 3--22 patients with very low LAA blood flow and, sometimes, barely detected Doppler signal. All the 25 patients in Group 1 had a sinus rhythm during TEE study, while the other 50 patients in Groups 2 and 3 were in atrial fibrillation. The patients in Group 3 had the lowest LAA ejection fraction and the lowest peak emptying velocity of these three groups. LAA SEC was present in five of 28 patients in Group 2 and 14 of 22 patients in Group 3, but in none of 25 patients in Group 1 (P < 0.001). LAA thrombus was present in one of 25 patients in Group 1, two of 28 patients in Group 2, and seven of 22 patients in Group 3 (P < 0.05). In conclusion, this study found that patients with poor LAA function, which was represented by lower LAA ejection fraction and lower peak emptying velocity, had higher incidence of LAA SEC or thrombus formation.

Adolescent↗
PubMed1995

[The rate of recovery of left atrial contractile function after the transition to sinus rhythm in patients with paroxysmal atrial fibrillation].

In the examination of 120 patients without valvular heart disease suffering from atrial fibrillation paroxysms mechanical function of the left atrium (LA) was assessed using Doppler echocardiography. The majority of the examinees had dilated LA which is thought to be arrhythmogenic. The recovery of the sinus rhythm is accompanied by electromechanical dissociation the longest duration of which took place in subjects exposed to electrical defibrillation. An inverse relationship was established between the time of the last fibrillation and recovery of LA mechanical function. The duration of the electromechanical dissociation of the atria holds prognostic importance in relation to recurrent fibrillation.

Adult↗
PubMed1993

Atrial natriuretic peptide and left atrial systolic function in normal subjects.

The purpose of this study is to elucidate factors determining the release of atrial natriuretic peptide (ANP) in normal volunteers at rest. Ten normal volunteers were included in this study. Ages ranged between twenty-seven and thirty-three years (mean twenty-seven). The authors measured plasma levels of ANP, and four cardiac chamber volumes, and their functions by cine magnetic resonance imaging using the rephased gradient-echo method. Plasma levels of ANP in 10 normal subjects were 15.0-37.1 pg/mL (mean 23.6 pg/mL). No significant relationship was seen between ANP level and heart rate or blood pressure. The level of ANP was positively correlated with left atrial (LA) emptying fraction and negatively correlated with LA minimal volume (r = 0.85, P < 0.01; r = 0.64, P < 0.05, respectively). No significant relationship was observed between plasma ANP level and left ventricular, right ventricular, or right atrial parameters. These results suggest that LA systolic function is one of the major determinants for ANP release in normal subjects at rest.

Adult↗
PubMed2000

Left atrial appendage function in patients with different pacing modes.

Many studies suggest that patients who receive a ventricular pacemaker have a higher incidence of systemic thromboembolism compared to patients receiving a physiological pacemaker. However, the exact mechanism regarding the etiology of thromboembolism remains unclear. We evaluated the left atrial appendage (LAA) functions, using multiplane transesophageal echocardiography (TEE), in patients with different pacing modes. In order to evaluate the ejection fraction (EF), peak emptying (V(E)) and filling (V(F)) flow velocities of the LAA by TEE, we studied 31 patients (mean age 63+/-18.5 years) who had been paced for 5.0+/-2.9 years. Patients with atrial fibrillation, left ventricular dysfunction and mitral valve disease were excluded. The pacing indications were complete atrioventricular block (AVB) in 19 patients (9 VVI, 10 VDD or DDD) and sick sinus syndrome (SSS) in 12 patients (5 VVI, 7 DDD). Mean EF, V(E) and V(F) of the LAA were significantly lower in all patients with ventricular pacing (25.5+/-15.6%, 30.4+/-15.6 cm/s and 29. 1+/-19.2 cm/s, respectively) compared to those with physiologic pacing (48.5+/-16.9%, 59.6+/-16.3 cm/s, 57.9+/-18.5 cm/s, respectively) (P<0.01 in all). When patients were further classified with respect to underlying heart disease whether they had SSS or AVB, all measurements of the LAA (EF, V(E) and V(F)) in both subgroup of patients with SSS and AVB were found significantly lower in those with ventricular pacing than in those with physiologic pacing (Tables 3 and 4). This decrease, especially in LAA flow, was much greater in those with SSS (Mean V(E) and V(F) <20 cm/s). In a patient paced with VVI for SSS, a thrombus was detected within the LAA cavity. In conclusion, these results suggest that the pacing modality appeared to influence the LAA functions in paced patients. Patients with asynchronous ventricular pacing modes had a significantly higher incidence of depressed LAA functions than did patients with physiological pacing, especially more marked in patients with sick sinus syndrome. This may be a factor responsible for increased risk of thrombus formation and thromboembolic events in this patient population.

Adult↗
PubMed2006

Effect of percutaneous mitral balloon valvuloplasty on left atrial appendage function: a Doppler tissue study.

The aim of this study was to compare left atrial appendage (LAA) functions by Doppler tissue imaging (DTI) before and after percutaneous balloon mitral valvuloplasty (PBMV). Twenty patients with symptomatic rheumatic mitral stenosis who underwent PBMV were included in this study. LAA functions were measured before and after PBMV. To determine LAA functions, LAA late filling (LAALF) velocity, LAA late emptying (LAALE) velocity, and area change of LAA percent were measured. In the DTI records, the first positive wave identical to the LAALE wave after the P wave was accepted as LAA late systolic wave, and the second negative wave identical to the LAALF flow was accepted as late diastolic wave. There was no difference in LAALF velocity and area change of LAA percent after PBMV. LAALE velocity increased after PBMV compared with baseline (P = .005). Late emptying, systolic, and diastolic wave values measured by DTI were found to be increased after PBMV compared with baseline (P = .023, P = .002, and P = .002, respectively). LAALE velocity measured by standard Doppler was increased after PBMV compared with baseline (P = .005), but there was no change in area change of LAA percent or LAALF. Spontaneous echocontrast was present in 7 of the 20 patients before procedure. It completely disappeared (4 patients) or decreased (3 patients) after procedure. In patients with spontaneous echocontrast, LAALE and late emptying, systolic, and diastolic wave values measured by DTI were found to be increased after PBMV compared with baseline. Our results suggest that PBMV improves LAA functions and, thereby, may have a favorable influence on future thromboembolic complications.

Adult↗
PubMed2003

Atrial stunning: basics and clinical considerations.

Conversion of atrial fibrillation and flutter to sinus rhythm results in a transient mechanical dysfunction of atrium and atrial appendage, termed atrial stunning. Atrial stunning has been reported with all modes of conversion of atrial fibrillation and flutter to sinus rhythm including both transthoracic and low energy internal electrical, pharmacological, and spontaneous cardioversion, and conversion by overdrive pacing and by radiofrequency ablation. Atrial stunning is a function of the underlying arrhythmia becoming apparent at the restoration of sinus rhythm, not the function of the mode of conversion, and does not develop after the unsuccessful attempts of cardioversion or the delivery of electric current to the heart during rhythms other than atrial fibrillation or flutter. Tachycardia-induced atrial cardiomyopathy, cytosolic calcium accumulation, and atrial hibernation are the suggested mechanisms of atrial stunning. Atrial stunning is at maximum immediately after cardioversion and improves progressively with a complete resolution within a few minutes to 4-6 weeks depending on the duration of the preceding atrial fibrillation, atrial size, and structural heart disease. Atrial stunning causes postcardioversion thromboembolism despite restoration of sinus rhythm. Duration of anticoagulation therapy after successful cardioversion should depend on the duration of atrial stunning. Lack of improvement in cardiac output and functional recovery of patients immediately after cardioversion is attributed to the atrial stunning. Verapamil, acetylstrophenathidine, isoproterenol, and dofetilide have been reported to protect from atrial stunning in animal and small human studies. Right atrium stunning is less marked and improves earlier than that of left atrium, resulting in a differential atrial stunning explaining the rare occurrence of pulmonary edema after cardioversion.

Animals↗
PubMed2001

Effect of blood pressure reduction on abnormal left atrial appendage function in untreated systemic hypertensive patients with sinus rhythm.

To investigate whether reduction in blood pressure has a beneficial effect on left atrial appendage (LAA) function, the authors evaluated 24 untreated systemic hypertensive patients with normal left ventricular systolic function in sinus rhythm at baseline and at 3 months after initiation of antihypertensive therapy. They performed transthoracic and transesophageal echocardiographic examinations in hypertensive patients before and after treatment of hypertension. Three of the 24 patients had blood pressure that failed to respond to the regimen of antihypertensive therapy and were removed from the analysis. Of the remaining 21 patients, mean systolic and diastolic blood pressures at baseline were 170 +/- 18 and 104 +/- 6 mm Hg, respectively, and fell significantly at 3 months to 141 +/- 10 and 90 +/- 5 mm Hg, respectively, (p<0.001) after initiation of antihypertensive therapy. There was no significant change in heart rate with treatment (baseline 81 +/- 8 and at 3 months 84 +/- 9 beats/min). There was no significant change in left ventricular end-diastolic diameter, left ventricular ejection fraction, left ventricular wall thickness, or left atrial diameter from baseline (49 +/- 4 mm, 58 +/- 5%, 12 +/- 1 mm, and 41 +/- 4 mm, respectively) at 3 months (48 +/- 5 mm, 59 +/- 4%, 12 +/- 1 mm, and 40 +/- 3 mm). The treatment caused a significant reduction in maximal LAA areas (6.3 +/- 1.3 cm2 at baseline, 4.6 +/- 0.7 cm2 at 3 months, p<0.001), with a concomitant increase in LAA emptying velocity (44 +/- 7 cm/sec at baseline, 60 +/- 9 cm/sec at 3 months, p<0.001). In conclusion, these findings suggest that reduction in blood pressure with antihypertensive therapy could improve LAA function in hypertensive patients with normal left ventricular systolic function in sinus rhythm.

Adult↗
PubMed1995

Left atrial size and function: assessment using echocardiographic automatic boundary detection.

OBJECTIVE: To evaluate the waveforms of left atrial area changes obtained by automated boundary detection with newly developed acoustic quantification technology. DESIGN: All subjects had measurements of left atrial areas taken in the apical four chamber, parasternal long axis, and parasternal short axis views using both conventional echocardiographic methods and automatic boundary detection on two occasions separated by at least a week. On the second visit measurements were also repeated in healthy volunteers after acute intravenous volume loading with 1 litre of saline over 2-5 minutes. SETTING: A university medical school echocardiographic laboratory. SUBJECTS: 12 healthy male volunteers and 8 patients with cardiac disease (5 with congestive heart failure, 1 with mitral stenosis, and 2 with hypertensive left ventricular hypertrophy, and dilated left atria). RESULTS: There was close correlation between conventionally derived left atrial areas and those obtained by automatic boundary detection, particularly in the apical four chamber view (r = 0.98). Both inter and intra observer variabilities (coefficient of variation) for left atrial areas measured by automatic boundary detection were good (4.7-14.2% and 8.1-18.6% respectively). The reproducibility (coefficient of variation) for derived indices of left atrial function, however, was much poorer (10.4-104.8% and 12.5-88% respectively). After acute volume loading significant increases in left atrial area were observed at all stages in the cardiac cycle. CONCLUSIONS: These data demonstrate that although the reproducibility of left atrial functional indices is poor, instantaneous left atrial cavity measurements with automatic boundary detection are reproducible. This suggests that automatic boundary detection may assist in serial non-invasive measurement of left atrial size to assess disease states and treatments.

Adult↗
PubMed1999

Atrial and ventricular pressures in atrial flutter.

The hemodynamic effects of atrial flutter (AF) are unknown. The purpose of the present study was to investigate the changes in atrial and ventricular pressures after induction of AF. In 23 patients with paroxysmal AF (age 59 +/- 9 years), a hemodynamic study was performed both during sinus rhythm and after induction of the tachyarrhythmia. During AF, 13 patients showed a fixed 2:1 AV conduction and 10 patients showed variable conduction. Mean right and left atrial pressures increased (P < 0.001) and right and left ventricular end-diastolic pressures decreased (P < 0.001) after induction of AF. Both the increase in mean atrial pressures and the decrease in ventricular end-diastolic pressures were present either in the patients with fixed 2:1 AV (heart rate: 133 +/- 15 beats/min) or in those with variable conduction (heart rate 96 +/- 15 beats/min), but were more marked in the former. AF produces an impairment of atrial function, as evidenced by the increase in mean atrial pressures and reduction in ventricular end-diastolic pressures in the absence of an elevated heart rate. The mechanisms responsible for the increase in mean atrial pressures are unknown; however, atrial contractions against closed AV valves seem to play an important role.

Atrial Flutter↗
PubMed2005

Embolic stroke, sinus rhythm and left atrial mechanical function.

A 64-year-old man manifested a stroke two years after restoration of sinus rhythm through a radiofrequency catheter ablation. Transesophageal echocardiography demonstrated the presence of a thrombus in the left atrial appendage. Left atrial volumes and different parameters of atrial emptying showed that, despite the persistence of the sinus rhythm, atrial mechanical function was severely impaired. After atrial ablation procedures echocardiography can be useful to stratify patients according to their risk of developing embolic events and hence be of help in deciding whether or not discontinuation of anticoagulant therapy is the appropriate choice.

Atrial Appendage↗
PubMed2000

The influence of right atrial septal pacing on the interatrial contraction sequence.

UNLABELLED: Right atrial septal pacing yields shorter interatrial conduction delays than conventional right atrial pacing at the free wall or the right atrial appendage. However, the hemodynamic effects of right atrial septal pacing are less well known. This study measured the delay between right and left atrial contractions during right atrial septal pacing (n = 21), conventional right atrial pacing (n = 32) and atrial multisite pacing (n = 6) by pulse Doppler echocardiography of transtricuspidal and transmitral blood flow. The effects of right atrial septal pacing (n = 14) versus conventional right atrial pacing (n = 22) on the optimal AV delay during dual chamber pacing was examined in patients with high degree atrioventricular (AV) block. Compared to sinus rhythm, conventional right atrial pacing increased P wave duration from 119 +/- 21 ms to 137 +/- 24 ms (P < 0.001), whereas both right atrial septal pacing (119 +/- 10 ms before, 106 +/- 13 ms during pacing, P = 0.002) and atrial multisite pacing (123 +/- 20 ms before, 112 +/- 11 ms during pacing, P = 0.5) shortened P wave duration. Atrial pacing caused a significant (P < 0.002) prolongation of atrial contraction [corrected] delays from 24 +/- 21 ms to 41 +/- 26 ms during conventional right atrial pacing, and reversed the right-to-left into a left-to-right contraction sequence in 20 of 21 patients during right atrial septal pacing (atrial conduction delay during sinus rhythm: 34 +/- 23 ms vs -37 [corrected] +/- 26 ms during atrial pacing, P < 0.0001). Atrial multisite pacing caused a nonsignificant shortening of the usual right-to-left contraction delay from 22 +/- 34 ms to 11 +/- 18 ms. The optimal left heart AV delay during AV sequential pacing was significantly (P = 0.002) shorter during right atrial septal pacing (108 +/- 38 ms) than during conventional right atrial pacing (152 +/- 33 ms). During conventional right atrial pacing the optimal right heart AV delay was significantly (P = 0.029) shorter than the optimal left heart AV delay. The opposite relation was observed for right atrial septal pacing (P = 0.033). CONCLUSIONS: Interatrial septal pacing does not synchronize right and left atrial contractions. It reverses the atrial mechanical timing from a right-to-left to a left-to-right contraction sequence, and requires the setting of shorter AV delays during dual chamber pacing if based on the optimization of left heart timing. Interatrial septal pacing is a technique which allows pacing of the left atrium from a right atrial site, rather than a single site approach to biatrial pacing.

Adolescent↗
PubMed2000

Evidence of heterogeneous remodeling in canine atrial fibrillation.

Although electrophysiologic changes occur during atrial remodeling, little is known how remodeling affects atrial fibrillation (AF) organization. We hypothesized that, in animals with long-term rapid atrial rates and a rapid ventricular response, AF would be more disorganized than in animals with rapid atrial rates only. In 8 dogs, chronic AF was created by 6 weeks of continuous rapid atrial pacing. In this group, the ventricular response to AF was spontaneous and unaltered. Twenty-one epochs of AF were epicardially mapped from the right and left atria. In 6 dogs, chronic AF was also created with rapid atrial pacing, however, the AV node was ablated and the ventricles were VVI paced at 80 BPM. Only 1 epoch of AF per dog was mapped. Atrial cycle length (CL) and spatial organization were compared. In chronic AF with a spontaneous ventricular rate, left atrial CL (96+/-14 ms) averaged 24 ms shorter than right atrial CL (121+/-18 ms) (P < .0001). With VVI pacing, AF CL was longer than in the dogs with the spontaneous ventricular rate. However, the left atrial CL (109+/-30 ms) was still significantly shorter than the right atrial CL (145+/-43 ms) (P < .001). Spatial organization values showed that during chronic AF with a spontaneous ventricular rate, the left atrium is more disorganized (2593+/-497) than the right atrium (2052+/-732) (P < .0001). With VVI pacing, the left atrium (2202+/-597) is still more disorganized than the right (1620+/-936) (P < .05). However, with VVI pacing, both atria appear less disorganized than dogs with VVI pacing. Atrial remodeling caused by heart failure that is superimposed on the remodeling due to rapid atrial rates causes the atria to be more disorganized than remodeling due to rapid atrial rates alone. However, in either case the left atrium is faster and more disorganized than the right atrium. Atrial fibrosis caused by the heart failure may increase the disorganization of AF activation.

Animals↗
PubMed2001

Differential effects of dofetilide, amiodarone, and class lc drugs on left and right atrial refractoriness and left atrial vulnerability in pigs.

OBJECTIVES: Antiarrhythmic drugs have been shown to prolong right atrial refractoriness while data on the left atrium are not available. In pigs we have observed shorter effective refractory periods (ERP) of the left compared with the right atrium associated with a much higher left atrial vulnerability for tachyarrhythmias. Since this could suggest a different distribution of repolarizing ion channels in left and right atrium, we investigated whether antiarrhythmic drugs blocking different ion channels have a differential effect on left and right atrial ERP and left atrial vulnerability. METHODS: In pentobarbital-anesthetized pigs (n=40) we measured and compared ERPs in both atria before and after different drugs with the S1-S2 extrastimulus method at three basic cycle lengths (BCL) and assessed the inducibility of atrial fibrillation/flutter (AF/AFL) by the premature S2 stimulus. RESULTS: At the three BCL tested (240/300/400 ms) baseline ERPs were shorter in left vs. right atrium (112+/-2/124+/-2/129+/-2 ms vs. 147+/-2/163+/-2/167+/-2 ms, P<0.001). Mostly non-sustained AF/AFL induced by the S2 extrastimulus was very frequent in the left (68%) and nearly absent in the right atrium (3%). Only amiodarone, 5 mg/kg i.v., which showed a balanced increase of left and right atrial ERP (29+/-5/33+/-4/35+/-3% vs. 30+/-5/35+/-5/42+/-7%), decreased the inducibility of AF/AFL significantly (-72%, P<0.01). Dofetilide, 10 microg/kg i.v., had a stronger effect on right than left atrial ERP (36+/-4/39+/-5/46+/-10% vs. 23+/-2/22+/-7/22+/-5%, P<0.05), while flecainide, 1 mg/kg i.v., prolonged left more than right atrial ERP (58+/-15/36+/-7/40+/-7% vs. 26+/-5/24+/-5/21+/-4%, P<0.05) similar to 1 mg/ kg of propafenone (46+/-5/45+/-7/32+/-10% vs. 17+/-4/21+/-5/ 25+/-8%, P<0.05). CONCLUSION: The shorter refractoriness of the left compared with the right atrium observed in pigs was associated with a high left atrial vulnerability for tachyarrhythmias, which was reduced only by amiodarone showing a balanced increase of left and right atrial ERP. Dofetilide was stronger on right atrial ERP, flecainide and propafenone on left atrial ERP. These differences suggest a differential distribution of repolarizing ion channels between left and right atrium with possible relevance for the antiarrhythmic efficacy of drugs.

Amiodarone↗
PubMed2006

Differences in the aging-associated trends of the monophasic action potential duration and effective refractory period of the right and left atria of the rat.

BACKGROUND: The incidence of atrial fibrillation (AF) increases with aging, but the aging-associated electrophysiological changes of atrial myocardium are poorly understood. METHODS AND RESULTS: Based on the hypothesis that aging of the atrium enhances AF susceptibility, 30 Wistar rats were divided into 3 age groups: adult, middle-aged, and aged (n=20 per group). Their hearts were isolated and perfused by Langendorff apparatus. Monophasic action potential duration at 90% repolarization (MAPD(90)) and effective refractory period (ERP) at the basic stimulation cycle length (BCL: 400 ms), and MAPD(90) at other different stimulation cycle lengths in each age group were measured. At the BCL, the MAPD (90) of the right atrial myocardium was prolonged from the adult to the aged group, that of the left atrial myocardium was prolonged from the adult to middle-aged group, and the MAPD(90) of the left atrial myocardium in the aged group were shorter than that in the adult and middle-aged groups. The ERP of the atrial myocardium showed the same age-associated trend as MAPD(90). As the stimulation frequency increased, the MAPD(90) of both the left and right atrial myocardium shortened correspondingly in the adult and middle-aged groups, but in the aged group the MAPD(90) of the right atrial myocardium shortened markedly more than that of the left atrial myocardium. CONCLUSIONS: There are different aging-associated electrophysiological changes in the right and left atrium, and the older heart is more vulnerable to developing the substrate for AF.

Action Potentials↗