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PubMed2002

Left atrial volume as a morphophysiologic expression of left ventricular diastolic dysfunction and relation to cardiovascular risk burden.

Left ventricular (LV) diastolic dysfunction is prevalent in the community. Current assessment of diastolic function can be complex, involving Doppler evaluation of an array of hemodynamic data. The relation between left atrial (LA) volume and diastolic function, and between LA volume and cardiovascular risk and disease burden are not well known. In the present prospective study of 140 adults, mean age 58 +/- 19 years, referred for a clinically-indicated echocardiogram and in sinus rhythm, with no history of atrial arrhythmias or valvular heart disease, we determined the LA volume, LV diastolic function status, cardiovascular risk score (based on age, gender, history of systemic hypertension, diabetes mellitus, hyperlipidemia, and smoking), and cardiovascular disease burden (based on confirmed vascular disease, congestive heart failure, and transient ischemic attack or stroke). LA volume was found to correlate positively with age, body surface area, cardiovascular risk score, LV end-diastolic and end-systolic dimensions, LV mass, diastolic function grade, tissue Doppler E/E', tricuspid regurgitation velocity, and negatively with LV ejection fraction (all p <0.006). In a multivariate clinical model, LA volume indexed to body surface area (indexed LA volume) was independently associated with cardiovascular risk score (p <0.001), congestive heart failure (p = 0.014), vascular disease (p = 0.012), transient ischemic attack or stroke (p = 0.021), and history of smoking (p = 0.008). In a clinical and echocardiographic model, indexed LA volume was strongly associated with diastolic function grade (p <0.001), independent of LV ejection fraction, age, gender, and cardiovascular risk score. In patients without a history of atrial arrhythmias or valvular heart disease, LA volume expressed the severity of diastolic dysfunction and provided an index of cardiovascular risk and disease burden.

Adolescent↗
PubMed2005

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.

Aged↗
PubMed1999

Noninvasive assessment of left atrial maximum dP/dt by a combination of transmitral and pulmonary venous flow.

OBJECTIVES: The study assessed whether hemodynamic parameters of left atrial (LA) systolic function could be estimated noninvasively using Doppler echocardiography. BACKGROUND: Left atrial systolic function is an important aspect of cardiac function. Doppler echocardiography can measure changes in LA volume, but has not been shown to relate to hemodynamic parameters such as the maximal value of the first derivative of the pressure (LA dP/dt(max)). METHODS: Eighteen patients in sinus rhythm were studied immediately before and after open heart surgery using simultaneous LA pressure measurements and intraoperative transesophageal echocardiography. Left atrial pressure was measured with a micromanometer catheter, and LA dP/dt(max) during atrial contraction was obtained. Transmitral and pulmonary venous flow were recorded by pulsed Doppler echocardiography. Peak velocity, and mean acceleration and deceleration, and the time-velocity integral of each flow during atrial contraction was measured. The initial eight patients served as the study group to derive a multilinear regression equation to estimate LA dP/dt(max) from Doppler parameters, and the latter 10 patients served as the test group to validate the equation. A previously validated numeric model was used to confirm these results. RESULTS: In the study group, LA dP/dt(max) showed a linear relation with LA pressure before atrial contraction (r = 0.80, p < 0.005), confirming the presence of the Frank-Starling mechanism in the LA. Among transmitral flow parameters, mean acceleration showed the strongest correlation with LA dP/dt(max) (r = 0.78, p < 0.001). Among pulmonary venous flow parameters, no single parameter was sufficient to estimate LA dP/dt(max) with an r2 > 0.30. By stepwise and multiple linear regression analysis, LA dP/dt(max) was best described as follows: LA dP/dt(max) = 0.1 M-AC +/- 1.8 P-V - 4.1; r = 0.88, p < 0.0001, where M-AC is the mean acceleration of transmitral flow and P-V is the peak velocity of pulmonary venous flow during atrial contraction. This equation was tested in the latter 10 patients of the test group. Predicted and measured LA dP/dt(max) correlated well (r = 0.90, p < 0.0001). Numerical simulation verified that this relationship held across a wide range of atrial elastance, ventricular relaxation and systolic function, with LA dP/dt(max) predicted by the above equation with r = 0.94. CONCLUSIONS: A combination of transmitral and pulmonary venous flow parameters can provide a hemodynamic assessment of LA systolic function.

Adult↗
PubMed2005

Left atrial volumetric remodeling is predictive of functional capacity in nonobstructive hypertrophic cardiomyopathy.

BACKGROUND: The left atrium is afterload sensitive, responding to immediate changes in left ventricular (LV) diastolic pressure, and left atrial volumetric remodeling has been reported in conditions associated with abnormal diastolic function. We examined the relationship between left atrial volumetric remodeling and objective measures of exercise capacity in patients with nonobstructive hypertrophic cardiomyopathy (HCM). METHODS: We compared LA volume indices, other 2-dimensional and Doppler echocardiographic parameters, invasive hemodynamic measures, and magnetic resonance imaging (MRI)-derived LV mass with exercise duration, maximal oxygen uptake (MV* O2), anaerobic threshold (AT), and ventilatory efficiency (VE/V* CO2 slope) in 43 patients with nonobstructive HCM. Patients underwent cardiac catheterization within 48 hours and metabolic stress testing within 1 week of their echocardiogram and MRI examinations. RESULTS: Left atrial volume at end-ventricular systole (LA max) and end-atrial emptying (LA min) correlated with MV* O2 (r = -0.39, P < .01 for both), AT (r = -0.42, r = -0.39, respectively, P < .01 for both), and VE/V* CO2 slope (r = 0.45, P = .003; r = 0.41, P = .008). Patients with an LA max > or =33 mL/m2 had significantly lower MV* O2 (P = .025) and AT levels (P = .017) and higher VE/V* CO2 slope levels (P = .004) as compared with patients with a smaller LA size. In multivariate analysis, MRI-determined LV mass, which was not a univariate correlate of exercise tolerance, provided additional effect when combined with LA volume index. CONCLUSIONS: Left atrial volumetric remodeling predicts exercise capacity in nonobstructive HCM and may reflect chronic LV diastolic burden. This simple noninvasive measure of LA size may provide a long-term indication of the effects of chronically elevated filling pressures in patients with HCM and further studies testing its prognostic value are necessary.

Adult↗
PubMed1978

Failure of left atrial distension to alter renal function in the nonhuman primate.

Experiments were undertaken to determine the influence of increasing left atrial pressure on renal function in the nonhuman primate. Significant elevations of left atrial pressure, produced by using an intra-atrial balloon, had no effect on salt or water excretion, renal plasma flow, or glomerular filtration rate. There were no significant changes in heart rate or blood pressure. We conclude that, unlike those in the dog, atrial receptors in the nonhuman primate play little or no role in modulating salt and water excretion.

Animals↗
PubMedDate not supplied

Influence of left ventricular diastole on left atrial appendage blood flow in patients with nonrheumatic atrial fibrillation.

The function of the left atrial appendage (LAA) reflected by the Doppler flow velocity at the outlet of the left atrial appendage has been reported to be correlated with spontaneous echo contrast and thrombus formation. To evaluate the influence of left ventricular diastole on LAA flow during atrial fibrillation (AF), 81 patients with chronic nonrheumatic AF were studied by transesophageal echocardiography. The peak outflow velocity of LAA during ventricular diastole was higher than that during ventricular systole (0.23 +/- 0.14 vs. 0.15 +/- 0.13 m/s, p < 0.001). The peak inflow velocity of LAA during ventricular diastole was also higher than that during ventricular systole (0.22 +/- 0.15 vs. 0.18 +/- 0.11 m/s, p < 0.01). Patients with a good left ventricular ejection fraction have a significantly higher peak LAA outflow velocity and a larger diastolic augmentation of LAA outflow (defined by the difference of LAA outflow between systolic and diastolic phases) than patients with an impaired left ventricular function. Thus, left ventricular diastole might have an influence on LAA flow during AF. In addition, the left ventricular function might be considered a predictor of subsequent thromboembolism from the viewpoint of its effect on LAA flow in patients with nonrheumatic AF.

Adult↗
PubMed1994

Left atrial backward ejection in symptomatic hypertrophic cardiomyopathy--assessment by transthoracic and transesophageal Doppler echocardiography.

BACKGROUND: During atrial contraction, the left atrium produces both forward ejection to the left ventricle and backward ejection to pulmonary veins. PURPOSE: To determine quantitatively left atrial ejection performance in symptomatic hypertrophic cardiomyopathy (HCM) patients by using left atrial systolic time intervals. METHOD: Thirty-one patients with symptomatic HCM and sinus rhythm and 31 normal subjects were studied with transthoracic and transesophageal Doppler echocardiography. Left atrial pre-ejection period (APEP), corrected atrial pre-ejection period (APEPc), and the duration (AET) and the time velocity integral (IA) of the atrial contraction wave in transmitral flow were determined. The duration (PV-AET) and the time velocity integral (PV-IA) of reverse pulmonary venous flow during atrial contraction were also determined. RESULTS: For normal subjects, significant correlations were found between APEP and electrocardiographic P wave duration (r = 0.78, p < 0.001), and between APEPc and left atrial forward ejection indices (AET: r = -0.42, p = 0.01, IA: r = -0.54, p < 0.05, respectively), but not between APEP and either of the two latter indices. These findings indicate that, for normal subjects, APEPc is a better index of left atrial systolic function than APEP. In contrast, for HCM patients, significant correlations were found between APEPc and left atrial backward ejection indices (PV-AET: r = -0.49; p < 0.005, PV-IA: r = -0.66; p < 0.001, respectively), but not between APEPc and left atrial forward ejection indices. CONCLUSION: Augmentation of left atrial afterload may result in decreased left atrial forward ejection and increased left atrial backward ejection. Thus, both left atrial forward ejection and left atrial backward ejection must be considered in the assessment of left atrial ejection performance in patients with symptomatic HCM.

Adult↗
PubMed2005

No correlation between atrial natriuretic peptide concentrations and echocardiographic measurements of left atrial size or left ventricular size and function in patients with persistent atrial fibrillation.

Atrial fibrillation (AF) may be associated with activation of atrial natriuretic peptide (ANP). The exact trigger for the release of ANP is still being debated. Atrial volume, pressure, and wall stretch are considered to be the main determinants of ANP activation. The aim of the study was to evaluate plasma ANP concentrations in patients with persistent AF and to analyze the echocardiographic determinants of ANP concentration in this group. The study population included 67 patients, 59 +/- 7 years of age, with a median AF duration of 5.5 months (range 0.1-12). The relationship between plasma ANP concentrations and echocardiographic left atrial (LA) diameter and volume, and left ventricular (LV) diameter and ejection fraction (EF) was analyzed by logistic regression analysis. The median baseline plasma ANP concentration was 63 pg/mL (range 21-126) in the study group versus 34 pg/mL (range 16-73) in a control group. The mean left antero-posterior atrial dimension, LA volume, LV enddiastolic diameter, and LVEF were 48 mm, 104 mL, 52 mm, and 54%, respectively. A significant linear positive correlation was found between plasma ANP concentration and maximal LA volume (r = 0.62, P < 0.01). A negative correlation was found between LVEF and plasma ANP concentration (r =-0.42, P = 0.01). However, by multivariate regression analysis, no echocardiographic parameter was an independent predictor of plasma ANP concentration. Plasma ANP concentrations were independent of echocardiographic measurements of LA size or LV size and function in patients with persistent AF.

Adult↗
PubMed1999

[Changes of left ventricular diastolic function in hypertensive patients with left atrial enlargement].

In order to find out the relationship between the left atrial enlargement and left ventricular diastolic function in hypertension, radionuclide ventriculography was performed in 45 hypertensive patients with normal left ventricular mass index(LVMI), including 23 with normal left atrium(Group I), 22 with left atrial enlargement(Group II), and 28 matched subjects as control(Group III). The results showed that the left ventricular diastolic function in Group I was normal, but abnormal in Group II. It is considered that left atrial enlargement and left ventricular diastolic dysfunction are the early signs of the hypertensive heart disease.

Adult↗
PubMed1994

Altered left ventricular diastolic function post-atrial pacing in coronary artery disease and left ventricular hypertrophy: further insights by pulmonary venous flow analysis.

Left ventricular filling dynamics during acute pacing-induced myocardial ischaemia were assessed using transoesophageal atrial pacing and simultaneous Doppler measurements of pulmonary venous and mitral flow. All patients (10 with CAD and 12 with left ventricular hypertrophy due to hypertrophic cardiomyopathy; HCM) were in sinus rhythm and patients with mitral insufficiency were excluded. Data were compared with those of a control group (n = 10). Measurements were obtained at baseline (heart rate 84 +/- 14 beats.min-1) and immediately after atrial pacing via the same transoesophageal echocardiography (TEE) probe after stepwise increase of the pacing rate to 133 +/- 12 beats.min-1. Heart rate immediately after pacing was 83 +/- 13 beats.min-1. Time velocity integrals (TVI) were calculated at baseline and after pacing for the following flows: early (E) and late (A) mitral flows, as well as antegrade systolic (S), diastolic (D) and retrograde diastolic (R) pulmonary venous flows. In the control group none of the flow parameters changed significantly after pacing compared with baseline data. In contrast, in CAD patients, the TVI of the E wave, the TVI E/A ratio as well as the pulmonary venous flow changed significantly after pacing (7.3 to 5.5 cm, P < 0.05, 1.7 to 1.1, P < 0.01 and 1.0 to 2.1 cm, P < 0.001, respectively). HCM patients also showed significant changes: TVI E/A ratio post-pacing decreased from 1.9 to 1.4 (P < 0.05), and the pulmonary venous reverse flow integral increased from 1.3 to 2.8 cm (P < 0.0001). Analysis of variance showed the TVI E/A ratio to be significantly dependent on pacing (P = 0.012). The pulmonary venous retrograde flow was found to be influenced by the presence of disease (P = 0.033 before and P = 0.0001 after pacing) and in all cases by pacing (before vs after pacing; P = 0.0001). Pacing resulted in significantly different changes in the TVI E/A ratio and the TVI of the retrograde pulmonary venous flow for CAD and HCM patients compared with those of control subjects. In patients with CAD and HCM, rapid atrial pacing results in a decreased early to late ventricular filling ratio because of impaired relaxation, despite presumably increased filling pressure. Retrograde pulmonary venous flow increased because of increased filling pressure and operating left ventricular stiffness.

Adult↗
PubMed1996

Assessment of posterior aortic wall motion using echocardiogram in patients with atrial fibrillation.

BACKGROUND AND HYPOTHESIS: Noninvasive evaluation of left ventricular (LV) diastolic function was performed on 12 patients with atrial fibrillation (AF) using posterior aortic wall echocardiogram and a parameter for determining the optimal heart rate in patients with chronic atrial fibrillation was considered. METHODS: Subjects were divided into two groups; one with no underlying cardiac disease (AF only group; n = 7) and the other with dilated cardiomyopathy (DCM group; n = 5). Left atrial emptying index (LAEI) obtained from the posterior aortic wall echocardiogram was used as the parameter of LV diastolic function, and R-R interval-LAEI relation and minimum R-R interval showing LAEI = 1.0 were investigated and compared between the two groups. RESULTS: There was a good correlation between R-R interval and LAEI until LAEI of 1.0 was obtained in all patients. Slope of the regression line was significantly steeper in the AF only group than in the DCM group, and minimum R-R interval showing LAEI = 1.0 was significantly shorter in the AF only group. CONCLUSION: Assessment of R-R interval-LAEI relation was useful for the noninvasive evaluation of LV diastolic function, and this parameter could be used for clinical application to determine the optimal heart rate in atrial fibrillation.

Aorta↗
PubMed2005

Prediction of circulatory equilibrium in response to changes in stressed blood volume.

Accurate prediction of cardiac output (CO), left atrial pressure (PLA), and right atrial pressure (PRA) is a prerequisite for management of patients with compromised hemodynamics. In our previous study (Uemura et al. Am J Physiol Heart Circ Physiol 286: H2376-H2385, 2004), we demonstrated a circulatory equilibrium framework, which permits the prediction of CO, PLA, and PRA once the venous return surface and integrated CO curve are known. Inasmuch as we also showed that the surface can be estimated from single-point CO, PLA, and PRA measurements, we hypothesized that a similar single-point estimation of the CO curve would enable us to predict hemodynamics. In seven dogs, we measured the PLA-CO and PRA-CO relations and derived a standardized CO curve using the logarithmic function CO = SL[ln(PLA - 2.03) + 0.80] for the left heart and CO = SR[ln(PRA - 2.13) + 1.90] for the right heart, where SL and SR represent the preload sensitivity of CO, i.e., pumping ability, of the left and right heart, respectively. To estimate the integrated CO curve in each animal, we calculated SL and SR from single-point CO, PLA, and PRA measurements. Estimated and measured CO agreed reasonably well. In another eight dogs, we altered stressed blood volume (-8 to +8 ml/kg of reference volume) under normal and heart failure conditions and predicted the hemodynamics by intersecting the surface and the CO curve thus estimated. We could predict CO [y = 0.93x + 6.5, r2 = 0.96, standard error of estimate (SEE) = 7.5 ml.min(-1).kg(-1)], PLA (y = 0.90x + 0.5, r2= 0.93, SEE = 1.4 mmHg), and PRA (y = 0.87x + 0.4, r2= 0.91, SEE = 0.4 mmHg) reasonably well. In conclusion, single-point estimation of the integrated CO curve enables accurate prediction of hemodynamics in response to extensive changes in stressed blood volume.

Animals↗
PubMed1989

[Effects of atrial natriuretic peptide on left ventricular function in man].

The effects of atrial natriuretic peptide (ANP) infusion were determined in 9 subjects undergoing cardiac catheterization which did not disclose heart disease. Data were obtained at rest and during the steady-state phase of alpha-human-(1-28)-atrial natriuretic peptide infusion (0.5 microgram/Kg bolus dose, 0.05 microgram Kg/min iv for 20 min). Mean blood pressure decreased from 105 +/- 3 to 98 +/- 4 mmHg (p less than 0.05); pressure measurements and left ventricular (LV) angiograms suitable for analysis were available in 7 of 9 subjects at matched heart rate. The infusion of ANP reduced LV end-diastolic and end-systolic volume indices from 93 +/- 6 to 80 +/- 6 ml/m2 (p less than 0.01) and from 25 +/- 3 to 17 +/- 1 ml/m2 (p less than 0.05), respectively. Left ventricular ejection fraction insignificantly increased from 72 +/- 5 to 77 +/- 4%. End-systolic pressure/volume ratio showed a slight but not significant rise (from 3 +/- 0.4 to 4 +/- 0.8). Initial plasma levels of ANP (48 +/- 12 pg/ml) rose to 1890 +/- 423 pg/ml (p less than 0.001) during the infusion and individual hemodynamic responses were not related to plasma concentrations of the peptide. These data suggest that the administration of ANP has no negative effects on LV function and the ANP-induced changes on cardiac performance are related to the reduced cardiac load.

Adult↗
PubMed1995

Extended transseptal versus conventional left atriotomy: early postoperative study.

BACKGROUND: Mitral valve operations require excellent exposure. The description of an extended vertical transseptal atriotomy by Guiraudon and associates promises to provide optimal exposure of the mitral valve. A prospective study was carried out to evaluate the merits of the extended vertical transseptal atriotomy in comparison with the conventional left atriotomy for mitral valve operations. METHODS: Conventional atriotomy was performed in 24 patients (group I) whereas 65 patients underwent the extended vertical transseptal offroach (group II). They were similar in age, sex, cause of disease, New York Heart Association functional class, left atrial size, and left ventricular function. The early postoperative rhythm changes in these two groups were compared. Statistical studies to analyze the significance of incidence of junctional arrhythmia in these two groups were carried out. RESULTS: Of the 24 patients in group I, 3 had development of transient junctional rhythm after operation, lasting less than 24 hours. None had this arrhythmia at the time of discharge. Of the 65 patients in group II, junctional rhythm was documented in 25, with a rate of occurrence of 38% (95% confidence interval, 27.6% to 52.2%). At the 6-week follow-up, 3 patients still had this junctional rhythm, with a failure to recover rate of 12% (3 of 25). CONCLUSIONS: The surgical exposure was considered excellent and closure of the atriotomy was thought to be easy in group II. However, this should be balanced against a significant (38%) incidence of transient junctional rhythm in the early postoperative period in group II, probably from injury to sinus node artery or atrial conduction pathways.

Adolescent↗
PubMed1993

Plasma noradrenaline as an indicator of functional state in hearts with mitral stenosis: the influence of acutely reduced left atrial pressure by balloon mitral commissurotomy.

To investigate the mechanism in which plasma noradrenaline concentration (pNA) is elevated in heart failure, the effect of balloon mitral valvuloplasty was used as a model of acute manipulation of the left atrial pressure reduction in ten patients with mitral stenosis. Gorlin mitral valve area and pNA were correlated with New York Heart Association functional class and found to have a significant exponential inverse relationship with each other ([pNA, pg/ml] = 198.9 x [mitral valve area, cm2]-0.696; P = 0.003). Elevated pNA could be partially explained by a reduced cardiac index (CI) ([pNA, pg/ml] = 403.4 x [CI, l/min/m2]-0.889; P = 0.027; r = 0.495), especially in severely failed hearts, but not by pulmonary capillary wedge pressure (PCWP). However, the percent changes (% delta) of variables early after balloon valvuloplasty exhibited a paradoxical contrast; % delta pNA showing a clear negative exponential correlation with % delta PCWP ([% delta pNA] = 436.0 x [% delta PCWP + 80]-0.679 - 80; P = 0.021), but not with % delta CI. These results suggest that pNA should be considered an indicator of cardiac functional class in mitral stenosis. PNA is modulated by both cardiac index and pulmonary capillary pressure, but in different ways.

Adult↗
PubMed1997

Improved Doppler echocardiographic assessment of the left atrial appendage by peripheral vein injection of sonicated albumin microbubbles.

We evaluated the usefulness of peripherally injected sonicated albumin microbubbles in transesophageal echo-Doppler cardiographic assessment of the left atrial appendage in 19 patients (age 61 +/- 19 [range 21 to 86] years; 12 [63%] women). Multiplane transesophageal echocardiography was performed before and after intravenous injection of sonicated albumin, and the left atrial appendage image and Doppler flow signal quality were assessed by a grading system of 0 to 3+ (0 = poor, 1 + = adequate, 2+ = good, and 3+ = excellent). Microbubbles appeared in the left atrium in 15 (79%) of 19 patients and completely opacified the left atrial appendage in 7 (37%) of 19 patients. Left atrial appendage maximal and minimal areas by planimetry were similar before and after contrast injection, although image quality improved in 13 (68%) of 19 patients (echocardiographic grade 1.8 +/- 0.6 vs 2.6 +/- 0.5, p< 0.001). Similarly, left atrial appendage peak emptying and peak filling Doppler flow velocities did not change before and after contrast injection, although Doppler flow signal quality improved in 12 (63%) of 19 patients (Doppler grade 1.6 +/- 0.5 vs 2.1 +/- 0.8, p < 0.05). Overall, contrast injection improved left atrial appendage echocardiographic or Doppler quality in 16 (84%) of 19 patients. Thus peripheral vein injection of sonicated albumin microbubbles can improve the assessment of left atrial appendage structure and function by transesophageal echocardiography.

Albumins↗
PubMed2002

Compensatory changes in atrial volumes with normal aging: is atrial enlargement inevitable?

OBJECTIVES: The aim of this study was to evaluate left atrial volume and its changes with the phases (active and passive) of atrial filling, and to examine the effect of normal aging on these parameters and pulmonary vein (PV) flow patterns. BACKGROUND: Atrial volume change with normal aging has not been adequately described. Pulmonary vein flow patterns have not been volumetrically evaluated in normal aging. Combining atrial volumes and PV flow patterns obtained using transthoracic echocardiography could estimate shifts in left atrial mechanical function with normal aging. METHODS: A total of 92 healthy subjects, divided into two groups: Group Y (young <50 years) and Group O (old > or =50 years), were prospectively studied. Maximal (Vol(max)) and minimal (Vol(min)) left atrial volumes were measured using the biplane method of discs and by three-dimensional echocardiographic reconstruction using the cubic spline interpolation algorithm. The passive filling, conduit, and active emptying volumes were also estimated. Traditional measures of atrial function, mitral peak A-wave velocity, velocity time integral (VTI), atrial emptying fraction, and atrial ejection force were measured. RESULTS: As age increased, Vol(max), Vol(min), and total atrial contribution to left ventricle (LV) stroke volume were not significantly altered. However, the passive emptying volume was significantly higher (14.2 +/- 6.4 ml vs. 11.6 +/- 5.7 ml; p = 0.03) whereas the active emptying volume was lower (8.6 +/- 3.7 ml vs. 10.2 +/- 3.8 ml; p = 0.04) in Group Y versus Group O. Pulmonary vein flow demonstrated an increase in peak diastolic velocity (Group Y vs. Group O) with no corresponding change in diastolic VTI or systolic fraction. CONCLUSIONS: Normal aging does not increase maximum (end-systolic) atrial size. The atrium compensates for changes in LV diastolic properties by augmenting active atrial contraction. Pulmonary vein flow patterns, although diastolic dominant using peak velocity, demonstrated no volumetric change with aging.

Adolescent↗
PubMed1992

Effect of dexmedetomidine, an alpha 2-adrenergic agonist, in the isolated heart.

Dexmedetomidine (DM) was studied in the isolated dog heart in the form of a Starling heart-lung preparation, (HLP). Hearts were subjected to increased loading by (a) increasing cardiac output, and (b) increasing systemic resistance. Results are depicted by cardiac function curves, prepared by plotting left atrial pressure against either systemic cardiac output or mean arterial pressure. DM, given in divided doses up to 44 micrograms, had no effect on heart rate or cardiac function, nor did injection of 0.5 mg of atipamezole, a selective alpha 2-antagonist. Additional injections of very large doses of DM, up to 4,444 micrograms, caused an increase in heart rate and a leftward shift of the function curves, ie, positive chronotropic and inotropic effects. Plasma catecholamine levels increased markedly between the 444 micrograms and the 4,444 micrograms cumulative doses of DM. Administration of 1 mg of prazosin had no effect, but 1 mg of propranolol returned the rate to baseline and markedly shifted function curves to the right and depressed their slopes. Thus, whereas low doses (corresponding to between 1 and 30 micrograms/kg in intact animals) of DM, given acutely IV, have been shown to depress cardiac function in intact and denervated dogs, this effect is not due to a direct effect on the myocardium. High doses, far beyond doses maximally effective in intact animals and man, release catecholamines from cardiac stores. Plasma DM levels after low doses in the HLP were between 1 to 10 times those seen in intact animals and human volunteers after the usual doses given clinically for their central effects. Because DM caused no myocardial depressant effect in the isolated, blood-perfused canine HLP, decreases in cardiac function seen after this drug is given to intact and autonomically denervated dogs must be due to factor(s) other than a direct action on the myocardium.

Adrenergic alpha-Agonists↗