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At least 109 records · Page 6Linked to original sources
PubMed1996

Evaluation of the effect of transthoracic cardioversion from ventricular tachycardia to sinus rhythm on left atrial mechanical function.

We measured left atrial function during sinus rhythm before and after ventricular tachycardia was induced in an electrophysiology laboratory, using peak transmitral A-wave velocity from pulsed-Doppler transthoracic echocardiography as a marker of left atrial mechanical function. The results of this prospective study do not support the hypothesis that a transthoracic shock of mild to moderate energy diminishes atrial mechanical function.

Adolescent↗
PubMed1975

Complete heart block. Studies of atrial and ventricular pacemaker site and function.

Atrial and ventricular pacemaker function was studied in 20 patients with idiopathic chronic complete heart block using the rate response to an intravenous bolus dose of isoprenaline (5 mug/70 kg bodyweight). Pacemaker responses were compared with those of 16 normal control subjects. None of the patients was having syncopal attacks at the time of admission and they were therefore selected in that none required immediate pacing. Ten of the patients had His bundle electrograms; all were shown to have a pre-His type of atrioventricular block. Two major groups emerge from the responses to isoprenaline. (a) High risk group: 11 of the 14 patients with reduced ventricular pacemaker responses had frequent syncopal attacks; 8 of the patients with Adams-Stokes syncope had a bundle-branch block pattern, while 3 had a narrow QRS. These patients require pacing. (b) Low risk group: a low risk asymptomatic group (5 patients) was identified with atrial and ventricular responses to isoprenaline within normal range. One of these patients had a bundle-branch block pattern, while 4 had a narrow QRS. These patients might be managed without pacing. The atrial response to isoprenaline was reduced in 12 of the 20 cases, 10 of whom also had reduced ventricular responses. All 9 patients with bundle-branch block had reduced ventricular responses, while 7 had reduced atrial responses. This evidence indicates that cardiac conducting tissue pathophysiology is widespread in complete heart bolck. The present work suggests that consideration of the ventricular pacemaker function is important in assessing liability to syncope in complete heart block. While patients with Adams-Stokes attacks require pacing it is suggested that all asymptomatic patients with complete heart block and those with minor symptoms are assessed using studies of both ventricular pacemaker function and site. A low risk group not requiring a pacemaker may emerge after sufficient follow-up assessment.

Adams-Stokes Syndrome↗
PubMed1993

[Outcome of Doppler parameters of left ventricular systolic function during atrial stimulation as a function of coronary disease].

The authors studied the effects of transoesophageal atrial pacing on Doppler parameters derived from flow in the left ventricular out flow tract (maximal velocity (V max), velocity-time integral (VTI), mean acceleration of aortic flow (Acc), acceleration force (AF) of the left ventricle). These parameters were recorded in patients with normal left ventricular wall motion at rest, with and without coronary disease. Eight patients had angiographically normal coronary arteries (Group 1) and 21 had coronary disease (Group 2) including 10 with an isolated stenosis of the left anterior descending artery (Group 2a) and 11 with multivessel disease (Group 2b). The heart rate was increased by increments of 20 beats per minute from 90 to 130 each minute. In coronary patients, atrial pacing resulted in a fall in V max from 0.99 +/- 0.15 to 0.90 +/- 0.12 m/s, p < 0.0005 and in AF from 23.1 +/- 6.3 to 19.6 +/- 4.8 Kdynes, p < 0.0005, whereas the Acc remained stable (13.51 +/- 3.27 and 13.53 +/- 2.47 m/s/s, NS). Conversely, V max (1.04 +/- 0.11 and 1.04 +/- 0.11, NS) and AF (25.2 +/- 5.7 and 26.3 +/- 6.7, NS) were unchanged in normal controls and the Acc improved from 13.87 +/- 3.61 to 17.04 +/- 3.49, (p < 0.05). The VTI fell significantly in both groups. The percentage variations of V max, Acc and AF were significantly different in coronary patients compared with normal controls. There were no differences between the two coronary subgroups.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1997

Recovery of atrial systolic function after pharmacological conversion of chronic atrial fibrillation to sinus rhythm: a Doppler echocardiographic study.

OBJECTIVE: To evaluate the time course of the recovery of atrial mechanical function after pharmacological cardioversion of chronic atrial fibrillation to sinus rhythm. PATIENTS AND METHODS: 21 patients (12 male, 9 female, aged 37-77 years) with chronic atrial fibrillation (< 6 months) were followed up by serial transmitral pulsed Doppler echocardiography. Echocardiographic studies were performed within the first 24 hours and on day 8, 15, and 30 after cardioversion. RESULTS: There was a significant increase (mean (SD)) in the peak A-wave velocity (from 0.35 (0.10) on day 1 to 0.50 (1.73) on day 8, and thereafter a gradual increase to 0.61 (0.14) m/s on day 30). Similarly, integrated late atrial velocities increased from 4.50 (1.46) on day 1 to 5.61 (1.73) on day 8 and 5.97 (1.47) cm/s2 on day 30. The atrial contribution to total transmitral flow increased significantly from 26 (7)% immediately after conversion of atrial fibrillation to sinus rhythm to 34 (7)% on day 30, indicating the haemodynamic benefit of the restoration of sinus rhythm. Left atrial diameter decreased but not significantly, from 4.11 (0.37) to 3.98 (0.34) cm (P < 0.005). CONCLUSIONS: These results suggest that restoration of atrial mechanical function after pharmacological cardioversion in patients with chronic atrial fibrillation is slow and gradual, as it is after electrical DC restoration of sinus rhythm. This time course may have important implications for determining how long treatment with anticoagulants and antiarrhythmic agents needs to continue in individual patients. It will also influence the clinical assessment of the haemodynamic benefit of restoring sinus rhythm in patients with chronic atrial fibrillation.

Adult↗
PubMed1989

Pulsed Doppler evaluation of atrial mechanical function after electrical cardioversion of atrial fibrillation.

Full recovery of atrial mechanical activity may not occur immediately after successful electrical cardioversion of atrial fibrillation to sinus rhythm. To examine the time course of recovery of left atrial mechanical function, serial two-dimensional, M-mode and transmitral pulsed Doppler echocardiographic studies were performed in 21 patients after elective direct current cardioversion of atrial fibrillation of 3 weeks' to 24 months' duration (mean 5 months). Over 3 months of follow-up, there were significant increases in both peak A wave velocity (p less than 0.005) and percent atrial contribution to total left ventricular filling (p less than 0.005). Compared with values in a normal control population, peak A wave velocity and percent atrial contribution to total left ventricular filling did not return to normal until 3 weeks after cardioversion in patients who remained in sinus rhythm. Left atrial dimension also decreased over the follow-up period (p less than 0.05) in patients with persistent sinus rhythm. These results may have important implications in guiding the appropriate duration of anticoagulant therapy after cardioversion, and in clinically assessing the hemodynamic benefit of restoring sinus rhythm in an individual patient.

Aged↗
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↗
PubMed1981

Left atrial transport function.

These studies show that the left atrial booster pump action serves as a supercharger which can increase left ventricular stroke volume in the range of 25 percent; and in patients with aortic stenosis, stroke work in the range of 50 percent (4). These changes can occur in the face of increased resistance to left ventricular filling in clinical conditions such as aortic stenosis where there is diminished left ventricular compliance and in mitral stenosis where there is stenotic resistance to left ventricular filling from the atrium. In spite of this fact, assessment of left atrial function by measurement of cardiac output changes occurring after return from atrial fibrillation to normal sinus rhythm yields erratic and confusing results. The reason for this is that atrial function, per se, is not a primary determinant of steady state cardiac output. Sequential A-V pacing may temporarily increase stroke volume in an acute setting like myocardial infarction. Nevertheless, one cannot infer from such observations that the use of permanent transvenous A-V sequential pacing will augment steady state cardiac output over a period of time. This is an important point to remember when considering the use of sequential A-V pacing, since it requires insertion of more complicated pacing and sensing wires as well as a more complex circuitry. All of these features lead to an increased risk of pacemaker malfunction. This increased risk of malfunction is not justified unless there is good evidence that atrial contribution is important in a given patient.

Aortic Valve Stenosis↗
PubMed1993

Impact of electrical cardioversion for atrial fibrillation on left atrial appendage function and spontaneous echo contrast: characterization by simultaneous transesophageal echocardiography.

OBJECTIVES: This study assessed the function of the left atrial appendage in the pericardioversion period to gain insights into mechanisms involved in thromboembolism after cardioversion of atrial fibrillation. BACKGROUND: Systemic embolization associated with electrical cardioversion of atrial fibrillation is thought to originate from the left atrium or left atrial appendage, or both. However, the mechanism involved is poorly understood. METHODS: We studied left atrial appendage function with transesophageal echocardiography in 20 patients with atrial fibrillation before and after successful electrical cardioversion. We measured left atrial appendage emptying and filling velocities by pulsed wave Doppler echocardiography, characterized Doppler emptying patterns, measured atrial appendage areas and assessed the presence or absence of spontaneous echo contrast or thrombus. RESULTS: Organized left atrial appendage function returned in 16 (80%) of 20 patients immediately after cardioversion. Atrial appendage emptying velocities before cardioversion were greater in patients without (0.39 +/- 0.02 m/s) than in those with (0.25 +/- 0.12 m/s) spontaneous echo contrast (p = 0.045). Furthermore, emptying velocities before cardioversion were significantly greater than late diastolic emptying velocities after cardioversion (0.31 +/- 0.15 vs. 0.14 +/- 0.12 m/s, p = 0.0001), as well as in both the group with (0.25 +/- 0.12 vs. 0.13 +/- 0.13 m/s, p = 0.001) and the group without (0.39 +/- 0.02 vs. 0.15 +/- 0.12 m/s, p = 0.01) spontaneous echo contrast. In addition, left atrial and atrial appendage spontaneous echo contrast developed in 4 of 20 patients and increased in intensity in 3 of 20 patients in the immediate postcardioversion period. CONCLUSIONS: Organized left atrial appendage function returns in most patients immediately after cardioversion of atrial fibrillation. However, its function is impaired compared with that before cardioversion. Furthermore, spontaneous echo contrast increased in 7 (35%) of 20 patients after cardioversion. These observations suggest that stunned left atrial appendage function after cardioversion may predispose the chamber to thrombus formation, which may play a role in the mechanism involved in the occurrence of embolization after cardioversion.

Aged↗
PubMed1994

Assessment of left atrial appendage function by biplane transesophageal echocardiography in patients with nonrheumatic atrial fibrillation: identification of a subgroup of patients at increased embolic risk.

OBJECTIVES: This study was conducted to identify a subgroup of patients with nonrheumatic atrial fibrillation with an increased risk for cardiogenic embolism by assessing left atrial appendage function. BACKGROUND: Patients with nonrheumatic atrial fibrillation have an increased risk for thromboembolic complications. The left atrial appendage is the most likely source for thrombus formation. It is likely that the appendage function (contraction, filling dynamics) is related to the pathogenesis of thrombus formation. METHODS: Twenty-nine patients with nonrheumatic atrial fibrillation (group I) underwent biplane transesophageal echocardiography. The maximal and minimal areas during a cardiac cycle and the peak emptying and filling velocities of the appendage were measured in both scan planes. For comparison, two additional groups were also analyzed. Group II consisted of 12 patients with chronic atrial fibrillation due to significant mitral stenosis, and group III consisted of 30 patients who were in sinus rhythm. RESULTS: Patients with nonrheumatic atrial fibrillation showed two distinct appendage flow patterns: either well defined peak filling and emptying waves (> or = 25 cm/s) with visible fibrillatory contractions of the appendage wall ("high flow profile") or irregular, very low, peak filling and emptying waves (< 25 cm/s) associated with almost no visible appendage contractions ("low flow profile"). The left atrial appendage function in the first subgroup resembles that seen in patients with sinus rhythm, whereas the appendage function in the latter subgroup resembles more the "static pouch" seen in patients with rheumatic atrial fibrillation. Events suggestive of cardiogenic embolism occurred in six patients from group I, five of whom were in the low flow profile subgroup (p < 0.05). The spontaneous echo contrast phenomenon was observed in 80% of the low flow profile subgroup but in only 5% in the high flow profile subgroup (p < 0.05). Three thrombi confined to the left atrial appendage were detected by transesophageal echocardiography in group I; all three of the patients were in the low flow profile subgroup. CONCLUSIONS: The assessment of left atrial appendage function by transesophageal echocardiography may be helpful to identify subgroups of patients with nonrheumatic atrial fibrillation with an increased risk of thrombus formation.

Atrial Fibrillation↗
PubMed1994

A study on left atrial transport function. Effect of age or left ventricular ejection fraction on left atrial storage fraction.

Left atrial (LA) storage fraction is defined as the ratio of storage volume of the left atrium (LA) during ventricular systole to left ventricular (LV) stroke volume. To test their hypothesis that left atrial (LA) storage fraction is increased to compensate for impaired LV filling in the heart of aged subjects or with impaired LV ejection fraction, the authors studied 33 "normal" subjects and 25 patients with coronary artery disease. LA volume was measured by LA cineangiocardiography, and LV stroke volume and LV ejection fraction were measured by LV cineangiocardiography. To further evaluate the determinants of changes in LA storage fraction, they measured the ratio of LA active release volume to LV stroke volume, and the ratio of LA passive release volume to LV stroke volume. In "normal" subjects, LA storage fraction was increased with age (r = 0.584, P < 0.01). In patients with coronary artery disease, LA storage fraction was increased as LV ejection fraction was decreased (r = -0.525, P < 0.01). In both cases, LA active release fraction was significantly associated with changes in LA storage fraction rather than in LA passive release fraction. They conclude that LA storage fraction may be an important determinant of LV filling mainly through the LA active release fraction.

Adolescent↗
PubMed1992

Effect of the pericardium on atrial systolic function.

The effect of pericardial constraint on atrial systolic function was investigated in nine acutely instrumented anesthetized dogs. Left and right atrial pressures were recorded by high-fidelity catheters; auricular diameters and free wall segment lengths were measured by sonomicrometry. Atrial function curves were constructed by relating atrial systolic dimensional shortening to atrial end-diastolic pressure during progressive volume loading. With the pericardium closed, the function curves were shifted markedly downward and rightward, such that atrial systolic shortening was reduced at any given pressure. There was a concomitant leftward and upward shift of the atrial end-diastolic pressure-dimension relationship. The relationship between atrial systolic shortening and atrial end-diastolic dimension was not shifted. These results suggest that the apparent depression of atrial systolic function with the pericardium closed is due to a restrictive effect of the pericardium on atrial filling. In conclusion, in the acutely dilated heart, the pericardium restricts atrial filling and thus causes a reduction in atrial systolic contribution to ventricular filling.

Animals↗
PubMed1986

[Left ventricular function during atrial fibrillation assessed by left ventricular function curve using ECG-gated blood pool scintigraphy].

Cardiac function is difficult to assess in patients with atrial fibrillation due to the widely fluctuating cycle lengths resulting in variable ventricular hemodynamics. With respect to ECG-gated blood pool scintigraphy, distortion of the time activity curve occurs due to a summation of irregular cycle lengths. Therefore, performing such a study has been regarded meaningless. To evaluate left ventricular function during atrial fibrillation using scintigraphic technique, a new processing algorithm was devised to make multiple gated images which are discriminated by the preceding R-R interval, and left ventricular filling and function curves were established. The left ventricular filling curve, obtained by plotting end-diastolic volume against the preceding R-R intervals demonstrated an impairment of blood filling in cases of mitral stenosis and constrictive pericarditis, which resolved after mitral commissurotomy in case of mitral stenosis. The left ventricular function curve, established by plotting stroke volume against end-diastolic volume, was analyzed according to indices such as "slope" and "position". Both of these indices were significantly reduced in relation to the severity of heart failure according to the NYHA's functional classification and cardiomegaly on chest radiography. On individual comparisons of underlying diseases, the indices decreased in the following order; lone atrial fibrillation, hyperthyroidism, aging, hypertension, mitral valve disease, ischemic heart disease, dilated cardiomyopathy and aortic regurgitation. The indices correlated closely with ejection fraction. In cases of mitral regurgitation, however, the function curves were situated to the right and above those of lone atrial fibrillation and decreased in slope despite the fairly well-maintained ejection fraction. After treatment with digitalis and/or diuretics, the function curves shifted to the left and upward. In conclusion, left ventricular filling and function curves based on a newly-devised algorithm of ECG-gated blood pool scintigraphy are of considerable clinical value in evaluating cardiac performance in patients with atrial fibrillation. They are widely applicable to the assessment of therapeutic and interventional effects.

Atrial Fibrillation↗
PubMed1997

Left atrial chamber and appendage function after internal atrial defibrillation: a prospective and serial transesophageal echocardiographic study.

OBJECTIVES: The purpose of this prospective study was to assess left atrial chamber and appendage function after internal atrial defibrillation of atrial fibrillation and to evaluate the time course of recovery. BACKGROUND: External cardioversion of atrial fibrillation may result in left atrial appendage dysfunction ("stunning") and may promote thrombus formation. In contrast to external cardioversion, internal atrial defibrillation utilizes lower energies; however, it is unknown whether the use of lower energies may avoid stunning of the left atrial appendage. METHODS: Transesophageal and transthoracic echocardiography were performed in 20 patients 24 h before and 1 and 7 days after internal atrial defibrillation to assess both left atrial chamber and appendage function. Transthoracic echocardiography was again performed 28 days after internal atrial defibrillation to assess left atrial function. The incidence and degree of spontaneous echo contrast accumulation (range 1+ to 4+) was noted, and peak emptying velocities of the left atrial appendage were measured before and after internal atrial defibrillation. To determine left atrial mechanical function, peak A wave velocities were obtained from transmitral flow velocity profiles. RESULTS: Sinus rhythm was restored in all patients. The mean +/- SD peak A wave velocities increased gradually after cardioversion, from 0.47 +/- 0.16 m/s at 24 h to 0.61 +/- 0.13 m/s after 7 days (p < 0.05) and 0.63 +/- 0.13 m/s after 4 weeks. Peak emptying velocities of the left atrial appendage were 0.37 +/- 0.16 m/s before internal atrial defibrillation, decreased significantly after internal atrial defibrillation to 0.23 +/- 0.1 m/s at 24 h (p < 0.01) and then recovered to 0.49 +/- 0.23 m/s (p < 0.01) after 7 days. The corresponding values for the degree of spontaneous echo contrast were 1.2 +/- 1.2 before internal atrial defibrillation versus 2.0 +/- 1.0 (p < 0.01) and 1.1 +/- 1.3 (p < 0.01) 1 and 7 days after cardioversion, respectively. One patient developed a new thrombus in the left atrial appendage, and another had a thromboembolic event after internal atrial defibrillation. CONCLUSIONS: Internal atrial defibrillation causes depressed left atrial chamber and appendage function and may result in the subacute accumulation of spontaneous echo contrast and development of new thrombi after cardioversion. These findings have important clinical implications for anticoagulation therapy before and after low energy internal atrial defibrillation in patients with atrial fibrillation.

Anticoagulants↗
PubMed1996

[Left atrial contractility function in hypertension].

UNLABELLED: The purpose of this study was the assessment of the left systolic atrial function (LSAF) in 45 hypertensive subjects (HS) with left ventricular hypertrophy (LVH). (LV mass index) (LVMI) (> 134 g/m2 for men, > 110 g/m2 for women) and in 32 normal subjects (NS). The both groups were matched for age, body surface, heart rate and LV fractional shortening. Left atrial volume (LAV) was calculated by the formula: LAV = 8 A1 x A2/3 pi l in which A1 is the area of the four-chamber view, A2 is the area of the two-chamber view and L is common length in the two views. The atrial function contractility was evaluated by the following parameters: 1. LA stroke volume (LASV) = LAV - LAMV where LAV is the volume before atrial systole and LAMV is the LA minimal volume. 2. LA ejection fraction (LAEF) = LASV/LAV. 3. Atrial ejection force (AEF) = peak A/MOA in which peak A wave is the maximal late diastolic velocity and MOA is the mitral orifice area. 4. Atrial transport (AT) = A/M in which M area is under the mitral velocity curve and A-area under the late diastolic velocity curved assessed by Doppler echo. [table: see text] Thus all above parameters are significantly increased in HS. In HS, LASV is correlated to LAV (r = 0.84; p < 0.001) and to LVMI (r = 0.32; p < 0.05). LAEF is correlated to peak A (r = 0.90; p < 0.001) and LVMI (r = 0.34; p < 0.05). CONCLUSIONS: In HS with LVH in comparison with N, the increase of the LA contractility is considered to be urged by the increase of LAV (Frank-Starling's law). These data could be explained by the less distensibility of LV chamber in relation to LVH.

Adolescent↗
PubMedDate not supplied

Left atrial mechanical function in the healthy elderly: new insights from a combined assessment of changes in atrial volume and transmitral flow velocity.

To assess left atrial mechanical function in the elderly, 35 old (age > 70 years) and 18 sex-matched young (age < 50 years) healthy subjects were studied. Transmitral flow velocities were recorded with pulsed Doppler echocardiography. Left atrial volumes were measured echocardiographically at mitral valve opening (maximal) and closure (minimal) and at onset of atrial systole (P wave of the electrocardiogram) according to the biplane area-length method. Left atrial passive emptying was assessed with the passive emptying volume (maximal-volume at onset of atrial systole) and fraction (passive emptying volume/maximal). Left atrial active emptying was assessed with the active emptying volume (volume at onset of atrial systole-minimal) and fraction (active emptying volume/volume at onset of atrial systole) and with left atrial ejection force = 0.5.blood density.volume at onset of atrial systole.active emptying fraction.(A velocity)2/A integral. Left atrial volumes were greater in old compared with young subjects (maximal: 31 +/- 10 cm3/m2 vs 24 +/- 8 cm3/m2, p = 0.02; at onset of atrial systole: 23 +/- 8 cm3/m2 vs 15 +/- 5 cm3/m2, p = 0.0002; minimal: 13 +/- 5 cm3/m2 vs 9 +/- 4 cm3/m2, p = 0.001). Passive emptying volume and fraction were lower (7.8 +/- 1.7 cm3/m2 vs 9.2 +/- 3.2 cm3/m2 [p = 0.04] and 26.4% +/- 9.8% vs 37.9% +/- 11.2% [p = 0.003], respectively), whereas atrial ejection force and active emptying volume were greater in old compared with young subjects (6.8 +/- 3.3 kdynes/m2 vs 4.2 +/- 2.8 kdynes/m2 [p = 0.007] and 9.2 +/- 4.1 cm3/m2 vs 5.7 +/- 2.9 cm3/m2 [p = 0.002], respectively). The active emptying fraction was similar in the two groups (39.7% +/- 11% vs 38.4% +/- 13%; difference not significant). Thus advanced age is associated with depressed left atrial passive emptying function and increased left atrial volume. Left atrial dilation contributes to an increase in atrial ejection force and the amount of blood ejected during left atrial systole and may represent an important compensatory mechanism in this age population.

Adult↗
PubMed1991

Echo-Doppler evaluation of the effects of heart rate increments on left atrial pump function in normal human subjects.

It is commonly believed that the atrial contribution to left ventricular filling increases during heart rate increments. However, the relative contribution of the pump function (atrial systole) and of the passive role (diastasis and reservoir) of the atrium to end-diastolic left ventricular filling is not well known. In order to investigate this problem, we performed a two-dimensional echo-Doppler study during right atrial pacing. Transmitral flow velocity curves were obtained by means of pulsed Doppler. Pacing was performed (1) at the lowest heart rate at which it was possible to obtain a stable capture of the atria, (2) at the heart rate at which the early and late Doppler filling waves almost completely overlapped. In both stages pacing was interrupted for a few seconds to obtain some post-pacing beats. Doppler tracing recorded at rest, during pacing and in the immediate post-pacing beats were analysed to obtain well-known parameters of atrial contribution; atrial peak flow velocity, early to atrial peak flow velocity ratio, and time-velocity integral of the atrial wave. Furthermore, in order to distinguish end-diastolic passive flow from the active contribution of atrial systole to filling, we superimposed the envelope of the last Doppler curve obtained during atrial pacing over the envelope of the first post-pacing curve. In this way the area of the atrial wave of the paced beat was divided by the mid-diastolic part of the post-pacing one into two areas, the integrals of which correspond to the active and passive atrial contribution respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗