Left atrial dimensions in growth and development: normal limits for two-dimensional echocardiography

Normal percentile curves for left atrial size in healthy children and adolescents

BACKGROUND

Despite the clinical utility of echocardiography to measure left atrial (LA) structure and function, there are scarcities of data about the percentiles of LA diameter (LA_D ), LA volume (LA_VOL ), and LA volume indexed by body surface area (LA_{VOL / BSA} ) from prospective population-based studies in healthy children and adolescents from the Southern Cone of Latin America.

METHODS

Echocardiographic studies were obtained in 1095 healthy subjects nonexposed to cardiovascular risk factors (5-24 years). Age- and sex-specific reference values of LA_D , LA_VOL , and LA_{VOL / BSA} were generated using parametric regression based on fractional polynomials.

RESULTS

After covariate analysis (ie, adjusting by age, body surface area), specific sex-specific percentiles were evidenced as necessaries. Age- and sex-specific 1st, 2.5th, 5th, 10th, 25th, 50th, 75th, 90th, 95th, 97.5th, and 99th percentile and curves were reported. Our percentiles showed high concordance and complementarity with what was previously reported for the population of North American, European, and Asiatic Populations.

CONCLUSIONS

In children and adolescents, the interpretation of the LA size requires sex-related percentiles. This study provides the largest Argentinean database concerning percentile curves of LA_D , LA_VOL , and LA_{VOL / BSA} obtained in healthy children and adolescents. These data are valuable in that they provide values with which data of populations of children, adolescents, and young adults can be compared.

Racial Variation in Echocardiographic Reference Ranges for Left Chamber Dimensions in Children and Adolescents: A Systematic Review

Echocardiography plays a critical role in the assessment of cardiac disease. Important differences in echocardiographically derived cardiac chamber dimensions have been previously highlighted in different population groups in adult studies, but this has not been systematically studied in children, whose body size changes throughout childhood. The aim of this study was to review the distribution of available reference ranges for the left cardiac chamber dimensions in older children and adolescents. The following electronic data bases were searched: Medline, Embase and Web of Science were searched to identify studies which have established echocardiographic reference ranges of left heart parameters in children and adolescents from 1975 to December 2017. There was no geographical limitation. All results were imported into Endnote. Retrieved articles were screened and data extracted by two independent reviewers. A total of 4398 studies were retrieved, with 36 studies finally included in this review. 29 (81%) references were from North America and European (Caucasians) populations, with only one study each from Africa and South America. Two-dimensional and M-mode techniques were the most commonly used echocardiography techniques. There were methodological variations in techniques and normalisation of references. Comparison of selected cardiac measures showed significant differences for interventricular septal thickness among Black African, Indian, German and US American children. Available echocardiographic references cannot be generalised to all settings and therefore, there is need for locally relevant reference ranges. Africa and South America are particularly under-represented. Future studies should focus on developing comprehensive echocardiographic reference ranges for children from different racial backgrounds and should use standardised techniques.

Cardiac Remodeling from Middle Age to Senescence

Background: The data on cardiac remodeling outside the scope of myocardial infarction and heart failure are limited. Methods: A cohort of middle-aged hypertensive subjects with age- and gender-matched control subjects without hypertension (n = 1,045, aged 51 ± 6 years) were randomly selected for the OPERA study (Oulu Project Elucidating Risk of Atherosclerosis study). The majority of those who were still alive after more than 20 years of follow-up underwent thorough re-examinations. Results: Left ventricular mass index (LVMI) increased significantly from 106.5 ± 27.1 (mean ± SD) to 114.6 ± 29.1 g/m² (p < 0.001), the thickness of the left ventricular posterior wall (LVPW) from 10.0 ± 1.8 to 10.6 ± 1.7 mm (p < 0.001), fractional shortening (FS) from 35.0 ± 5.7 to 38.4 ± 7.2 % (p < 0.001), and left atrial diameter (LAD) from 38.8 ± 5.2 to 39.4 ± 6.7 mm (p = 0.028) during the 20-year follow-up. After multivariate adjustments, hypertension treated with antihypertensive medication and male gender predicted a smaller increase in the thickness of LVPW (p = 0.017 to <0.001). Baseline higher fasting plasma insulin level, larger intima media thickness of the carotid artery, greater height and antihypertensive medication (p = 0.046-0.002) predicted a smaller (less favorable) change of FS. The increase of LAD was associated with higher baseline diastolic blood pressure (p = 0.034) and greater height (p = 0.006). Conclusion: Aging from middle age to senescence increases the echocardiographic indexes of LVMI, LVPW thickness, FS and LAD. Several baseline factors are associated with these changes.

Left atrial geometry and pump function in ischemic cardiomyopathy

Background

Many of the factors that are known to alter left atrial (LA) contractility are present in patients with ischemic cardiomyopathy (ICM). Nevertheless, preservation of LA contractile function in this group of patients was reported in previous studies. The aim of this study was to assess the changes in LA size, geometry and contractile function in ICM.

Methods and results

60 subjects (age: 49 ± 12 years, 53% males) in sinus rhythm undergoing coronary angiography (CA), were enrolled in this study; 15 subjects as a control group, 30 patients with reduced ejection fraction (EF) and significant coronary artery disease; as the ICM group, and 15 with reduced EF and normal CA; as the dilated cardiomyopathy (DCM) group.

LA dimensions, volume, active emptying fraction (ACTEF) and eccentricity index (LAEi) as well as late diastolic velocities of the mitral annulus (a′) and LA free wall (A₃) were measured.

Compared with the control group, ICM patients had larger LA volume and reduced ACTEF, a′ and A₃, with no significant difference between patients with ICM and DCM in any of these parameters. LA eccentricity was, non-significantly, higher in both cardiomyopathy groups than in the control group.

Conclusions

Patients with ICM have increased LA volume and reduced LA contractile function in comparison with normal controls. LA enlargement, LA contractile dysfunction and LA geometric changes in ICM are similar to that occurring in DCM. LA size, contractile function and eccentricity may not be reliable in differentiating ischemic from idiopathic dilated cardiomyopathy.

Individual reference values for 2D echocardiographic measurements. The Stockholm - Umeå Study

OBJECTIVES

Improved reference values for 2D echocardiographic measurements are required, even when more recent echocardiographic technology is employed. In addition, it may be preferable to individualize reference values from age, gender and body characteristics of any subject.

DESIGN

A material of 180 healthy subjects was collected and investigated, aiming for an even distribution of sex and age (from 20 to 80 years of age; the Stockholm material). For atrial areas, material from another 216 healthy subjects with similar sex and age distribution was added (the Umeå material). The 2D measures determined were the left and right ventricular diameters in diastole, the left ventricular diameter in systole, the thickness of septum and posterior wall, the diameters of the aortic root (sinotubular junction) and the left atrium (all in parasternal view), together with the left and right ventricular diameters in diastole and left and right atrial areas in end-systole (apical four-chamber view). The width of the inferior vena cava (from subcostal view) was also determined.

RESULTS

Confidence intervals for females and males are presented for each of these measures. Multiple linear regression analyses with age, sex and measures of body characteristics as predictors were also performed, and for eight of the 12 measurements, such equations are presented.

CONCLUSIONS

It is possible to obtain more highly individualized reference values for these cardiac dimensions, which may clinically be a better way of distinguishing pathological states from normal states.

Characterization of echocardiographic measures of cardiac structure and function in healthy octogenarians

BACKGROUND

Currently, there is not enough echocardiographic information regarding aging-associated changes in the octogenarian population. We aimed to characterize echocardiographic measures of structure and function among a group of healthy octogenarians.

METHODS

Approximately 350 octogenarians, residing in nursing homes, were screened in Ankara, Turkey. According to inclusion criteria, 40 octogenarians were enrolled. These subjects underwent conventional and tissue Doppler echocardiography according to the guidelines of the American Society of Echocardiography (ASE). The population was also separated into various groups according to gender, body mass index (BMI, <25 vs. 25-29.9), and blood pressure (<80/120 mmHg vs. 80-89/120-139 mmHg). All measurements were indexed by dividing to body surface area (BSA) for standardization.

RESULTS

Left ventricular mass (LVM), posterior wall thickness, right ventricular diameter, tricuspid E/A ratio, and septal e'-wave velocity were significantly higher in men, which lost significance after adjusting for BSA. There was no significant difference between groups formed by BMI and blood pressure. Moreover, mild global left and right ventricular dysfunction including a prominent diastolic counterpart, however, with normal ejection fraction was revealed using conventional and tissue Doppler techniques. Finally, we checked our results with the current reference values of the ASE and observed the following differences: ventricular septum, relative wall thickness, LVM, and mass index values were above ASE reference range, posterior wall measurements were close to upper range. On the contrary, left ventricular diameters and volumes were below ASE reference range.

CONCLUSIONS

We described echocardiographic measures of structure and function in a group of healthy octogenarians.

Left Atrial Volume Index in Healthy Subjects: Clinical and Echocardiographic Correlates

Left atrial (LA) size is related to cardiovascular morbidity and mortality. The relative role of multiple determinants of LA morphology in healthy subjects remains incompletely defined. The aim of this study is to define normal ranges for LA diameters and volume index (LAVi), and to investigate clinical and echocardiographic correlates. A total of 1480 healthy individuals (mean age 36.1 ± 15.5 years, range 20–80; 61% males) underwent a comprehensive transthoracic echocardiography exam including assessment of LAVi calculated using the biplane area‐length method at the apical four‐chamber and two‐chamber views at ventricular end systole (maximum LA size) and indexed for body surface area (BSA). Mean LAVi in the overall population was 29.5 ± 10.8 mL/m2 (range: 26.1–41.8 mL/m2). Distinct higher values were found in subjects ≥50 years as compared with those <50 years of age (33.4 ± 12.5 vs. 29.1 ± 13.5; P < 0.001). On univariate analysis, LA volume was significantly associated with age (r = 0.48, P < 0.0001), male gender (r = 0.28, P < 0.05), BSA (r = 0.51, P < 0.0001), mitral E/E' (r = 0.47, P < 0.0001), LV end‐diastolic volume (r = 0.52, P < 0.0001), and LV mass index (r = 0.31, P < 0.05). Multivariable analysis identified age, BSA, LV end‐diastolic volume, and mitral E/E' ratio as the only independent determinants of LA volume (model R2 = 0.54, P < 0.0001). Gender was an independent predictor of most absolute LA volume, but following normalization to BSA, some associations became nonsignificant. In healthy individuals LAVi vary significantly by age, BSA, diastolic function, and LV dimensions, with lesser effects of gender.

Size matters! Impact of age, sex, height, and weight on the normal heart size

BACKGROUND

Therapeutic decisions in cardiology are determined frequently by cardiac chamber size. To decide whether cardiac dimensions are still in the normal range, reliable reference values are needed. However, published reference values mostly refer to historical cohorts using motion-mode measurements and have not been adjusted for sex or age. The impact of body size was only vaguely addressed. The importance of such adjustments is illustrated by studies, which show that smaller individuals and women are at risk of delayed treatment and impaired outcome when currently used reference values are applied. The aim of the present study was to assess the impact of body size, sex, and age on the normal heart size.

METHODS AND RESULTS

We prospectively studied 622 individuals (52.7% women; 17-91 years; 143-200 cm; 32-240 kg) without cardiac disease by standard transthoracic echocardiography. Multivariable linear regression analyses of the impact of sex, age, height, and weight on cardiac chamber size were performed. By multivariable regression analysis (n=500), all 4 variables independently influenced cardiac chamber size. The validity of cardiac dimensions predicted by the regression model was tested prospectively in a validation cohort (n=122). A calculator is proposed that estimates cardiac dimensions on the basis of the regression analysis.

CONCLUSIONS

Sex, height, weight, and age significantly affect the normal heart size. These parameters need to be considered when cutoff values indicating the need for treatment or even surgery are established.

Effect of age, gender, and left ventricular diastolic function on left atrial volume index in adults without known cardiovascular disease or risk factors

There are limited data on reference values of left atrial volume indexes (LAVIs) in adults without known cardiovascular disease or risk factors, as well as their stratification by age, gender, and diastolic stage. LAVIs were calculated using the biplane area-length method in accordance with guidelines in 966 consecutive patients (mean age 48.0 ± 15.7 years) with no known cardiovascular disease or risk factors, with preserved left ventricular systolic function and normal or grade I diastolic dysfunction (DD). The mean LAVI was 23 ± 8 ml/m(2). Using a conventional cut-off value of 34 ml/m(2) (mean + 2 SDs of the values derived from the guidelines) to define abnormal LAVI would label about 10% of patients as having dilated left atria and structural heart disease, whereas using the American Society of Echocardiography's recommended cutoff of the mean + 1 SD (i.e., 28 ml/m(2)) would do so for up to about 20%. The mean LAVI was similar between the genders (p = 0.10) and among different age groups (p = 0.60 for the trend across decades). Finally, when stratified by diastolic function, the mean LAVIs were 23.2 ± 8.3 and 22.2 ± 8.7 ml/m(2) for patients with normal (n = 653) and grade I DD (n = 313), respectively (p = 0.10). In conclusion, in this cohort of patients without known cardiovascular disease or risk factors, the cut-off values for abnormal LAVI were greater than those adopted in the guidelines. There was no variation, however, by gender, age, or grade I DD, although subjects with long-standing grade I DD and/or high filling pressures were likely underrepresented.

Left atrial volume in children without heart disease and in those with ventricular septal defect or patent ductus arteriosus or hypertrophic cardiomyopathy

In adults, the left atrial (LA) volume has been shown to reflect diastolic function and is a powerful predictor of cardiac morbidity and mortality. Normative LA volume values in children and the effect of loading conditions on the LA volume in those with congenital heart disease are lacking. The purposes of the present study were to (1) establish normal LA volume values for children, (2) assess the effect of left ventricular volume loading conditions on LA volume, and (3) describe the effect of abnormal myocardial relaxation on the LA volume. We retrospectively reviewed the echocardiograms from 3 pediatric cohorts: group N (n = 522), children with normal echocardiographic findings; group VSD/PDA (n = 71), children with ventricular septal defect (VSD; n = 50) or patent ductus arteriosus (PDA; n = 21); and group HC (n = 63), children with hypertrophic cardiomyopathy (HC). In group N, we identified the LA volume indexed to the body surface area (LA volume index) as a consistent measure of the LA volume in children 3 to 23 months old (mean 16 ± 3 ml/m(2)) and 2 to 17 years old (mean 22 ± 4 ml/m(2)). LA dilation was more common in group VSD/PDA than in group N (27% vs 2%, p <0.0001) and in children with moderate or large shunts than in those with smaller shunts (61% vs 5%, p <0.0001). In group HC, the LA volume index correlated with the mitral valve E/e' ratio (p <0.0001). In conclusion, this is the first study to establish normal pediatric LA volume values. The LA volume index is a reproducible measure of LA size in children ≥ 3 months old. The LA volume index reflects a chronically increased left ventricular volume load in children with VSD or PDA and chronically elevated left ventricular filling pressures in children with HC.

Diastolic dysfunction, cardiovascular aging, and the anesthesiologist

As the number of persons aged 65 years and older continues to increase, the anesthesiologist will more frequently encounter this demographic. Cardiovascular changes that occur in this patient population present difficult anesthetic challenges and place these patients at high risk of perioperative morbidity and mortality. The anesthesiologist should be knowledgeable about these age-related cardiovascular changes, the pathophysiology underlying them, and the appropriate perioperative management. Whether presenting for cardiac or general surgery, the anesthesiologist must identify patients with altered physiology as a result of aging or diastolic dysfunction and be prepared to modify the care plan accordingly. With a directed preoperative assessment that focuses on certain aspects of the cardiovascular system, and the assistance of powerful echocardiographic tools such as tissue Doppler, this can be achieved.

Diastolic dysfunction and its histopathological correlation in obstructive hypertrophic cardiomyopathy in children and adolescents

BACKGROUND

Histopathologic hallmarks of hypertrophic cardiomyopathy (HCM) include myocyte hypertrophy and disarray as well as interstitial and endocardial fibrosis. Published correlations between echocardiographic parameters and histopathologic findings are scarce.

METHODS

All patients aged <20 years (n = 45; 15 female patients; median age, 14 years) with obstructive HCM undergoing septal myectomy at the Mayo Clinic from 2003 to 2007 were identified. A retrospective review of echocardiographic data was performed, and these data were compared with the histologic findings from the myectomy specimens.

RESULTS

Histopathologic analysis of myectomy specimens revealed significant myocyte hypertrophy (100%), myocyte disarray (98%), interstitial fibrosis (95%), and subendocardial fibrosis (97%). On multivariate regression analysis, there was a significant relationship between the degree of myocyte disarray and echocardiographic markers of left ventricular diastolic dysfunction.

CONCLUSION

The results of this study suggest that myocyte disarray is a key factor responsible for diastolic dysfunction in pediatric patients with obstructive HCM. These findings provide novel insights into the mechanism of diastolic dysfunction in HCM that warrant further study.

Left atrial volume and geometry in healthy aging: the Cardiovascular Health Study

BACKGROUND

The left atrium is a validated marker of clinical and subclinical cardiovascular disease. Left atrial enlargement is often seen among older individuals; however, there are few population-based data regarding normal left atrial size among older persons, especially from those who are healthy, and from women. Furthermore, because the left atrium is a 3D structure, the commonly used parasternal long-axis diastolic diameter often underdiagnoses left atrial enlargement.

METHODS AND RESULTS

We evaluated left atrial size in 230 healthy participants (mean age, 76+/-5 years) free of prevalent cardiac disease, rhythm abnormality, hypertension, and diabetes selected from the Cardiovascular Health Study, a prospective community-based study of risk factors for cardiovascular disease in 5888 elderly participants. In addition to the standard long-axis measurement, we obtained left atrial superoinferior and lateral diameters and used these dimensions to estimate left atrial volume. These measurements were used to generate reference ranges for determining left atrial enlargement in older men and women, based on the 95% percentiles of the left atrial dimensions in healthy participants, both unadjusted, and after adjustment for age, height, and weight. In healthy elderly subjects, indices of left atrial size do not correlate with age or height but with weight and other measures of body build.

CONCLUSIONS

These data provide normative reference values for left atrial size in healthy older women and men. The results should be useful for refining diagnostic criteria for left atrial dilation in the older population and may be relevant for cardiovascular risk stratification.

Derivation of a size-independent variable for scaling of cardiac dimensions in a normal paediatric population

AIMS

It is general practice to correct cardiac chamber size for body size by the process of scaling or normalization. Normalization is most commonly performed using simple linear or isometric correction; however, there is increasing evidence that this approach may be flawed. Likewise, there is little agreement concerning the appropriate scaling variable (measure of body size) for normalization. Therefore, we aimed to establish the optimal method for correcting the differences in body size in a large population of echocardiographically normal paediatric subjects.

METHODS AND RESULTS

We compared the relative ability of standard size variables including height (HT), body weight (BW), body mass index (BMI), and body surface area (BSA), in both isometric and allometric models, to remove the effect of body size in 4109 consecutive echocardiographically normal subjects<18 years of age, using the left atrial dimension (LAD) as a reference standard. Simple linear normalization resulted in significant residual correlations (r=-0.57 to -0.92) of the indexed value with the body size variable, the correlations with weight (WT) and BSA actually increasing. In contrast, correction by the optimal allometric exponent (AE) removed the effects of the indexed variable (residual correlations -0.01 to 0.01), with BW and BSA best removing the effects of all the measures of body size.

CONCLUSION

Conventional linear correction for body size is inaccurate in children and paradoxically increases the relationship of the indexed parameter with WT and BSA. Conversely, correction using the optimal AE removes the effect of that variable, with WT best correction for all measures of body size.

Echocardiographic evaluation of left atrial size and function: current understanding, pathophysiologic correlates, and prognostic implications

Left atrial (LA) volume has recently been identified as a potential biomarker for cardiac and cerebrovascular disease. However, evidence regarding the prognostic implications of LA volume still remains unclear. Evaluation of LA size and function using traditional and more recent echocardiographic parameters is potentially feasible in the routine clinical setting. This review article discusses the conventional and newer echocardiographic parameters used to evaluate LA size and function. Conventional parameters include the assessment of phasic atrial activity using atrial volume measurements, transmitral Doppler peak A velocity, atrial fraction, and the atrial ejection force. Newer parameters include Doppler tissue imaging (DTI) including segmental atrial function assessment using color DTI, strain, and strain rate. In addition, an overview of the implications and clinical relevance of the findings of an enlarged left atrium, from currently available literature, is presented.

How many patients would be misclassified using M-mode and two-dimensional estimates of left atrial size instead of left atrial volume? A three-dimensional echocardiographic study

OBJECTIVES

Left atrial size has shown prognostic importance in a variety of cardiac conditions. Diameters, area, and volume derived from M-mode and two-dimensional (2D) echocardiography are commonly used to estimate left atrial size. However, M-mode and 2D measures of left atrial size rely on various geometrical assumptions and their accuracy remains to be determined. To address this issue, we compared M-mode and 2D parameters routinely used to estimate left atrial size with three-dimensional (3D) echo measured left atrial volume (LAV) as a reference standard.

METHODS

We studied 104 patients (55% males, 62 +/- 15 years, range 10-87 years), presenting for a routine echocardiographic evaluation.

RESULTS

The mean 3D LAV for the study population was 90 +/- 68 ml (range 24-458 ml). We found highly significant (P < 0.0001) correlations between 3D LAV and left atrial anterior-posterior (r = 0.78, 95% CI = 0.69-0.85), superior-inferior (r = 0.74, 95% CI = 0.63-0.81) and medial-lateral (r = 0.91, 95% CI = 0.86-0.93) diameters. A highly significant correlation was also found between 3D LAV and left atrial area (r = 0.94, 95% CI = 0.91-0.96). However, using M-mode anterior-posterior diameter or left atrial area would have misclassified 57% and 70% of our study patients, respectively, regarding the degree of left atrial dilatation. Closer correlations and narrower confidence intervals were found between 3D LAV and single-plane (r = 0.98; 95% CI = 0.94-0.97) and biplane (r = 0.97; 95% CI = 0.96-0.98) 2D LAVs.

CONCLUSION

Left atrial diameters and area measurements were poor predictors of 3D LAV, especially in the enlarged left atria. Therefore, these parameters can be misleading in assessing the severity of left atrial dilatation. Two-dimensional LAVs are accurate in estimating 3D LAV. The small additional accuracy obtained by using the biplane instead of the single-plane area-length method, and the fact that the biplane method is more technically demanding and time consuming, may allow the use of the area-length for routine clinical use.

Left Atrial Size

Left atrial (LA) enlargement has been proposed as a barometer of diastolic burden and a predictor of common cardiovascular outcomes such as atrial fibrillation, stroke, congestive heart failure, and cardiovascular death. It has been shown that advancing age alone does not independently contribute to LA enlargement, and the impact of gender on LA volume can largely be accounted for by the differences in body surface area between men and women. Therefore, enlargement of the left atrium reflects remodeling associated with pathophysiologic processes. In this review, we discuss the normal size and phasic function of the left atrium. Further, we outline the clinically important aspects and pitfalls of evaluating LA size, and the methods for assessing LA function using echocardiography. Finally, we review the determinants of LA size and remodeling, and we describe the evidence regarding the prognostic value of LA size. The use of LA volume for risk stratification is an evolving science. More data are required with respect to the natural history of LA remodeling in disease, the degree of LA modifiability with therapy, and whether regression of LA size translates into improved cardiovascular outcomes.

Left atrial volume, geometry, and function in systolic and diastolic heart failure of persons > or =65 years of age (the cardiovascular health study)

The left atrium enlarges in association with many factors, including aging, atrial fibrillation, hypertension, diastolic dysfunction, and heart failure (HF) with low ejection fraction. However, left atrial (LA) volume, geometry, and emptying have not been compared between diastolic and systolic HF, nor has the association of LA volume for new HF been determined in older subjects, many of whom have normal ejection fraction. We used echocardiography to measure the LA volume, geometry, and emptying in 851 community-dwelling subjects > or =65 years of age, including 180 with HF at baseline and 255 participants who subsequently developed HF. The LA volume, area, and linear dimensions were higher in the prevalent and incident HF groups than in controls and did not differ between those with systolic versus diastolic HF, independent of co-morbidities and Doppler measures of diastolic function. The fractional area change was associated with prevalent, but not incident, HF. In conclusion, in population-based older subjects, the LA size is increased and LA emptying decreased in patients with either systolic or diastolic HF. LA size is associated with the new development of HF. These findings highlight the important role of the left atrium in HF, with or without a decreased ejection fraction.

Effect of right atrial overdrive pacing in the prevention of symptomatic paroxysmal atrial fibrillation: a multicenter randomized study, the PAF-PACE study

The aim of this study was to assess if right atrial overdrive pacing can suppress symptomatic episodes of paroxysmal atrial fibrillation (PAF) in patients without bradyarrhythmias. Forty-two patients with frequent and symptomatic PAF without other pacing indication had a pacemaker implanted after a 4-week run-in period, during which the frequency of symptomatic PAF episodes and the mean heart rate were objectively documented. Depending on the mean heart rate recorded during run-in, the pacemaker was programmed in random order to right atrial AAI pacing at 10-19 beats/min > mean heart rate (medium overdrive [MO]), at 20-29 beats/min > mean heart rate (high overdrive [HO]) and to no pacing (OAO mode) for 4-12 weeks each using a crossover design. In the 35 patients who completed the protocol, the number of symptomatic episodes of PAF (>30-second duration) per week was significantly lower during MO pacing (median 0.88, P = 0.001, n = 35) and during HO pacing (median 0.75, P = 0.002, n = 20) than during OAO (median 2.02 and 2.04, respectively). There was no difference between MO and HO pacing in the 20 patients paced at both rates (0.97 vs 0.75, P = 0.33). Seven patients did not complete the protocol due to persistent atrial fibrillation (n = 4), angina pectoris requiring surgery (n = 1), and unwillingness to continue the study due to improvement (n = 1) or worsening (n = 1) of symptoms during the study periods. Right atrial overdrive pacing can reduce the number of symptomatic PAF episodes in patients with frequent and drug refractory PAF but without bradyarrhythmias.

Left atrial and left ventricular function in healthy children and young adults assessed by three dimensional echocardiography

OBJECTIVE

To establish normal values of left atrial and left ventricular volumes and function in children and young adults using three dimensional echocardiography (3DE).

METHODS

169 healthy subjects aged 2 to 27 years were studied by digitised 3DE. 3DE was achieved using rotational acquisition of planes at 18 degrees intervals from the parasternal view for the left atrium and from the transthoracic apical view for the left ventricle with ECG gating and without respiratory gating. Left atrial and left ventricular volumes could be calculated throughout the heart cycle, and the respective time-volume curves were reconstructed in each subject.

RESULTS

For the analysis the subjects were divided into five groups according to body surface area: 0.5-0.75 m2, 0.75-1.0 m2, 1.0-1.25 m2, 1.25-1.5 m2, and over 1.5 m2. Mean (SD) left atrial maximum volume/body surface area was 19.6 (3.5), 21.7 (3.7), 22.0 (4.7), 24.5 (4.8), and 27.4 (6.4) ml/m2; left ventricular maximum volume/body surface area was 50.1 (8.8), 54.9 (10.1), 56.4 (9.9), 58.7 (11.0), and 64.4 (10.3) ml/m2. Left atrial active emptying increased from 19% to 35% with age (r = 0.34, p < 0.001) and with decreasing heart rate (r = -0.28, p < 0.001).

CONCLUSIONS

Transthoracic 3DE is well suited for studying the phasic changes in left atrial and left ventricular volumes in young children as well as in adults. The data obtained from 169 healthy subjects will serve as a reference for further studies in patients with various cardiac abnormalities.

Left atrial volume assessed by transthoracic three dimensional echocardiography and magnetic resonance imaging: dynamic changes during the heart cycle in children

OBJECTIVE

To assess the dynamic changes in left atrial volume by transthoracic three dimensional echocardiography and compare the results with those obtained by magnetic resonance imaging (MRI).

DESIGN AND PATIENTS

30 healthy children (15 boys and 15 girls, aged 8 to 13 years) underwent examination by three dimensional echocardiography and MRI.

METHODS

Three dimensional echocardiography of the left atrium was performed using rotational acquisition of planes at 18 degrees intervals from the parasternal window with ECG gating and without respiratory gating. Volume estimation by MRI was performed with a slice thickness of 4-8 mm and ECG triggering during breath holding in deep inspiration. A left atrial time-volume curve was reconstructed in each child.

RESULTS

Left atrial maximum and minimum volumes averaged 24.0 ml/m(2) and 7. 6 ml/m(2) by three dimensional echocardiography, and 22.1 ml/m(2) and 11.9 ml/m(2) by MRI. The greater left atrial minimum volume in the latter was at least in part a result of breath holding. Dynamic changes in left atrial volume during the heart cycle were detectable by both methods. The higher temporal resolution of three dimensional echocardiography allowed a more precise evaluation of different phases.

CONCLUSIONS

Three dimensional echocardiography and MRI were both useful methods for studying the physiological volume changes in the left atrium in children. These methods may be used for further study of the systolic and diastolic function of the heart.

Comparison of automatic boundary detection and manual tracing technique in echocardiographic determination of left atrial volume

Previous reports have indicated that echocardiography with automatic boundary detection (ABD) is useful for the noninvasive estimation of left ventricular volume. However, few data exist regarding the measurement of left atrial (LA) volume, which also provides pivotal information in the clinical setting. Therefore, the feasibility of LA volume measurement by ABD in comparison with the manual tracing using modified Simpson's method (SM) was evaluated. Fifty-nine patients with coronary artery-disease with sinus rhythm were examined. Using ABD, a region of interest was set around the LA border and mitral annulus from an apical four-chamber view. The maximal and minimal LA volume (Vmax and Vmin) were measured from the volume waveform. Using the SM, the maximal and minimal LA volume were measured by the manual tracing on frozen frames at the apical four-chamber view. The ABD displayed a curve of LA volume change that consisted of passive emptying, diastasis, and active emptying phases during the left ventricular diastolic period. Under these conditions, the Vmax and Vmin were 43.7 +/- 11.2 ml and 21.1 +/- 7.6 ml, respectively, yielding the volume change of 22.6 +/- 6.0 ml. By the SM, Vmax and Vmin were 43.1 +/- 9.9 ml (r = 0.94, p < 0.0001, y(ABD) = 0.91x (SM) + 3.6) and 22.0 +/- 9.0 ml (r = 0.91, p < 0.0001, y = 0.94x + 0.7), respectively, and the volume change was 22.8 +/- 6.1 ml (r = 0.82, p < 0.0001, y = 0.84x + 3.8). These results indicate that the ABD from the apical four-chamber approach could provide an accurate estimation of LA volume change, suggesting the potential value of this method in assessing LA function, although some technical difficulties need to be further overcome.

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.

Estimation of left ventricular diastolic pressures from precordial pulsed-Doppler analysis of pulmonary venous and mitral flow

Because analysis of pulmonary venous flow (PVF) will be extensively used in comprehensive Doppler assessment of left ventricular diastolic function, this study was designed to (1) evaluate the feasibility of PVF measurement in 116 consecutive patients with various cardiac abnormalities by using precordial pulsed Doppler echocardiography; (2) Estimate mean pulmonary capillary pressure (MPCP) and left ventricular end-diastolic pressure (LVEDP) from Doppler variables of PVF and mitral inflow; and (3) evaluate the influence of clinical and hemodynamic variables on PVF Doppler patterns. We adequately recorded anterograde PVF in 96 (82.7%) patients and retrograde PVF in 45 (38.7%) patients. The strongest correlation between MPCP and Doppler variables of PVF was found with systolic fraction (the systolic velocity time integral expressed as a fraction of total anterograde PVF) (r = -0.88; p < 0.001). Age influenced this relation, with progressive increase of the systolic fraction in older patients. A good correlation (r = 0.72; p < 0.001) was found between LVEDP and the difference in duration of the reversal PVF and the mitral a wave. In conclusion, (1) PVF can be recorded adequately in most patients with precordial Doppler echocardiography; (2) left ventricular diastolic pressures can be estimated reliably by precordial Doppler echocardiography; and (3) the clinical meaning of Doppler-derived indexes of left ventricular diastolic performance is age-related.

New perspectives in the assessment of cardiac chamber dimensions during development and adulthood

The use of body surface area to assess the normalcy of cardiac dimensions has several limitations. To determine whether cardiac dimensions can be assessed by other indexes of body size and growth, this study evaluated the relations between cardiac dimensions assessed by two-dimensional echocardiography and age, height, weight and body surface area. The study group included 268 normal persons aged 6 days to 76 years of age. The dimensions examined included the aortic anulus, left atrium and left ventricular end-diastolic diameter, each measured in the parasternal long-axis plane, and left ventricular length measured from the apical two-chamber view. The analysis confirmed that the heart and great vessels grow in unison and at a predictable rate after birth, reaching 50% of their adult dimensions at birth, 75% by 5 years and 90% by 12 years. Although each cardiac dimension related linearly with height (aortic anulus, r = 0.96; left atrium, r = 0.91; left ventricular diameter, r = 0.94; left ventricular length, r = 0.93), the relations among age, weight and body surface area were best expressed by quadratic equations. Multiple regression confirmed that after adjustment for height, other indexes including age, gender, weight and body surface area had no independent effect on the prediction of each dimension. Therefore, because height is a nonderived variable that relates linearly with cardiac dimensions independent of age, it offers a simple yet accurate means of assessing the normalcy of cardiac dimensions in children and adults.

Determination of left atrial area and volume by cross-sectional echocardiography in healthy infants and children

Part 1 of the study measured the end-systolic and end-diastolic left atrial (LA) areas and volumes in 30 children through sector echocardiography, and compared these values with those obtained with biplane angiocardiography. A strong correlation exists between the LA area in the frontal plane as determined by apical (r greater than 0.91) and subcostal (r greater than 0.98) echocardiography on the one hand and by angiocardiography on the other. However, there is a slight underestimation of the LA area by the apical 4-chamber view. LA volume as determined by subcostal sector echocardiography in the frontal and sagittal plane also correlated well with LA volume calculated with biplane angiocardiography (r greater than 0.97). Part 2 of the study determined LA areas and volumes in 74 healthy newborns and infants by echocardiography and related them to body weight and body surface area, thus obtaining normal values for this age group. The relation of the LA area and volume measurements in newborns and infants to body weight or surface area was best described by a linear function. The mean of the percentage of systolic-diastolic area diminution was 53 +/- 6% for the apical 4-chamber view and 50 +/- 4% for the subcostal 4-chamber view. LA ejection fraction determined by the subcostal biplane volume measurements was 62 +/- 7% (mean +/- standard deviation). These values were independent of body weight or surface area.