Atrial receptors and renal function in conscious dogs.
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Assessment of Left Atrial Appendage Structure and Function by Transesophageal Echocardiography: A Review.
This article examines the transesophageal echocardiographic assessment of the left atrial appendage anatomy and function in individuals without significant structural heart disease and in those with atrial fibrillation with or without cardioembolism or mitral valve stenosis. We also summarize the available data in the usefulness of transesophageal echocardiographic studies in patients undergoing cardioversion for atrial fibrillation and percutaneous balloon valvuloplasty for mitral stenosis. Also, potential limitations and ongoing developments in the use of transesophageal echocardiography in the assessment of the left atrial appendage are outlined, and recommendations are given for the uniform reporting of quantitative data.
Journal Article↗
On the brain involvement in saline loading natriuresis--an indirect evidence for the cerebral participation in the functional expression of the atrial natriuretic system.
The ablation of the anterior third cerebral ventricle region totally prevented the homeostatically effective natriuresis which should have followed hypertonic saline loading in conscious sheep. The increased cerebrospinal fluid (CSF) sodium concentration potentiated, and the decreased CSF[Na] prevented, natriuresis during isotonic saline loading. It is thus probable that a cerebral natriuretic system is involved in the functional expression of any other peripheral natriuretic system, e.g. the heart atrial natriuretic system which has been found to play a role in both hypertonic and isotonic saline loading natriuresis.
Animals↗
Preserved atrial natriuretic peptide secretory function after cardiac transplantation.
The purpose of this investigation was to determine whether atrial natriuretic peptide (ANP) secretory function is preserved after cardiac transplantation. Thirteen hemodynamically stable outpatients performed supine exercise on a bicycle an average of 7 months after orthotopic cardiac transplantation. Right atrial pressure increased 2.2-fold (6 +/- 1 to 13 +/- 2 mm Hg) and pulmonary artery wedge pressure 2.1-fold (11 +/- 1 to 23 +/- 7 mm Hg) with exercise in the transplant recipients. Resting venous ANP level (114 +/- 19 pg/ml) and peak exercise venous level (373 +/- 61 pg/ml) was elevated in transplant recipients (p less than 0.001) compared with control subjects (21 +/- 1 and 92 +/- 14 pg/ml, respectively. This represents a 3.3-fold (114 +/- 19 to 373 +/- 61 pg/ml) increase in the ANP level from resting to exercise in transplant recipients and a 4.4-fold (21 +/- 1 to 92 +/- 14 pg/ml) increase in control subjects. A correlation between venous ANP levels and hemodynamics (right atrial pressure) was observed r = 0.49 p = 0.01. It is concluded that ANP levels at rest are elevated after cardiac transplant, the levels correlate with the intracardiac hemodynamics, and exercise-induced augmentation of plasma levels occurs.
Adult↗
Atrial stunning as predictor of early relapse into atrial fibrillation after cardioversion.
Although the high rate of success after cardioversion, less than 50% of patients maintain sinus rhythm for the first year. In view for the high percentage of relapse into atrial fibrillation, it is interesting to analyze the relationship between atrial stunning after cardioversion and relapse into atrial fibrillation. Thus, we evaluated 101 patients with atrial fibrillation and successful cardioversion. Atrial mechanical function was assessed by measures of transmitral peak A wave velocity, determined before and weekly after cardioversion during 1 month. Fifty-five percent of patient relapse into atrial fibrillation during follow-up. No significant differences were found in clinical and echocardiographic variables between the group with and without relapse. However, the group of patients who relapsed into atrial fibrillation showed a lower peak A wave velocity immediately after cardioversion than patients who maintain in sinus rhythm at month (0.44+/-0.27 vs. 0.60+/-0.38 m/s p<0.01). Impaired atrial function improves during the first 14 days after cardioversion.
Atrial Fibrillation↗
Assessment of sinus node function in asymptomatic subjects with sinus bradycardia and in symptomatic patients with sino-atrial disease.
Sinus node function was evaluated in 18 patients with sinus bradycardia without complaints (Group I), in 16 patients with sinus bradycardia and/or sinoatrial block with complaints (subgroup IIa) and in 14 patients with the bradycardia-tachycardia syndrome (subgroup IIb). Mean values of corrected sinus node recovery time (CSRT), atrial effective refractory period (AERP) and atrial functional refractory period (AFRP) differentiated significatively asymptomatic subjects of group I from the two subgroups of patients with sinoatrial disease, but failed to differentiate each subgroup from the other one. There was no significative difference in mean sinoatrial conduction time (SACT) between group I and each of the two subgroups. Three patients of subgroup IIa and 1 patient of subgroup IIb had a false negative response after both overdrive and premature programmed atrial pacing. Spontaneous cycle length was directly correlated with the sinus node recovery time and the atrial refractoriness in group I, and with the only sinus node recovery time in subgroup IIb. No direct correlations were observed in subgroup IIa. This suggests a less disturbed sinus node automaticity in bradycardia-tachycardia syndrome.
Arrhythmia, Sinus↗
Loss of atrial contractility is primary cause of atrial dilatation during first days of atrial fibrillation.
Atrial fibrillation (AF) induces a progressive dilatation of the atria which in turn might promote the arrhythmia. The mechanism of atrial dilatation during AF is not known. To test the hypothesis that loss of atrial contractile function is a primary cause of atrial dilatation during the first days of AF, eight goats were chronically instrumented with epicardial electrodes, a pressure transducer in the right atrium, and piezoelectric crystals to measure right atrial diameter. AF was induced with the use of repetitive burst pacing. Atrial contractility was assessed during sinus rhythm, atrial pacing (160-, 300-, and 400-ms cycle length), and electrically induced AF. The compliance of the fibrillating right atrium was measured during unloading the atria with diuretics and loading with 1 liter of saline. All measurements were repeated after 6, 12, and 24 h of AF and then once a day during the first 5 days of AF. Recovery of the observed changes after spontaneous cardioversion was also studied. After 5 days of AF, atrial contractility during sinus rhythm or slow atrial pacing was greatly reduced. During rapid pacing (160 ms) or AF, the amplitude of the atrial pressure waves had declined to 20% of control. The compliance of the fibrillating atria increased twofold, whereas the right atrial pressure was unchanged. As a result, the mean right atrial diameter increased by approximately 12%. All changes were reversible within 3 days of sinus rhythm. We conclude that atrial dilatation during the first days of AF is due to an increase in atrial compliance caused by loss of atrial contractility during AF. Atrial compliance and size are restored when atrial contractility recovers after cardioversion of AF.
Animals↗
Simultaneous measurement of pulmonary venous flow by intravascular catheter Doppler velocimetry and transesophageal Doppler echocardiography: relation to left atrial pressure and left atrial and left ventricular function.
OBJECTIVES: The aim of our study was to compare measurements of pulmonary venous flow velocity obtained either by transesophageal Doppler echocardiography or by intravascular catheter Doppler velocimetry. Furthermore, the relation among pulmonary venous flow velocity, left atrial compliance and left atrial pressure was evaluated. BACKGROUND: Data about the relation between left atrial pressure and pulmonary venous flow velocity are controversial. METHODS: A total of 32 patients undergoing elective open heart surgery for coronary artery bypass grafting were included prospectively in the study. Pulmonary venous flow velocity (Doppler catheter) and left atrial pressure (microtip pressure transducer) were recorded simultaneously with recordings of pulmonary venous flow velocity obtained by transesophageal Doppler echocardiography. RESULTS: Agreement between Doppler catheter and Doppler echocardiographic measurements of pulmonary venous flow velocity (n = 18 patients) was analyzed using the Bland-Altmann technique. The 95% limits of agreement were -0.16 to +0.11 m/s for systolic peak velocity, -0.14 to +0.09 m/s for diastolic peak velocity and -0.12 to +0.10 m/s for atrial peak velocity. The closest agreement between both methods was found for the ratio of systolic to diastolic peak velocity, the ratio of systolic to diastolic flow duration and the time from Q deflection on the electrocardiogram to maximal flow velocity. Mean left atrial pressure was strongly correlated with the ratio of systolic to diastolic peak velocity (r = -0.829), systolic velocity-time integral (r = -0.653), time to maximal flow velocity (r = 0.844) and the ratio of systolic to diastolic flow duration (r = -0.556). The ratio of systolic to diastolic peak velocity and the time to maximal flow velocity were identified as strong independent predictors of mean left atrial pressure. Left atrial compliance was not found to be an independent predictor of mean left atrial pressure. CONCLUSIONS: Flow velocity in the left upper pulmonary vein can be reliably recorded by transesophageal pulsed wave Doppler echocardiography. Our data reveal further evidence that mean left atrial pressure can be estimated by the pattern of pulmonary venous flow velocity.
Aged↗
Online Quantification of Cardiovascular Function in Children.
Echocardiography is the most valuable diagnostic tool in evaluating congenital anatomic pathology. Improvements in transducer resolution and development of color Doppler echocardiography have resulted in the ability to delineate cardiac anatomy in detail. Online quantification of cardiovascular function represents a similar advance in terms of evaluating physiology. Performing an online quantification examination requires attention to technical factors such as avoiding chamber foreshortening, optimizing endocardial tracking, ensuring patient cooperation, and accounting for the effects of respiration. A typical examination consists of performing acoustic quantification on the left ventricle in both short-axis and apical four-chamber views and on the left atrium from the apical four-chamber view. From these views, ventricular systolic and diastolic function, as well as atrial systolic function, can be assessed. As in adult patients, acoustic quantification indices in children correlate well with similar indices measured off line. Acoustic quantification data in children show that, unlike adults, the left ventricular filling is almost exclusively dependent on passive filling, with minimal atrial contribution. Acoustic quantification indices have also been useful in monitoring left ventricular function in intensive care and emergency department settings to evaluate the acute effects of a clinical manipulation. Acoustic quantification can also be used to assess the function of ventricles of unusual geometry such as in hypoplastic left and right heart, double-inlet single ventricle, and unbalanced atrial ventricular septal defect. In these types of ventricles, systolic and diastolic systemic ventricular function has been shown to be markedly altered compared with a normal left ventricle. Acoustic quantification can also be used to assess diastolic function in a variety of pediatric diseases, such as transplant rejection and insulin-dependent diabetes mellitus. In summary, online quantification of cardiovascular function represents a significant advance in the ability to understand cardiovascular physiology in children.
Journal Article↗
[Stratification of the thromboembolic risk in patients with non-rheumatic atrial fibrillation: assessment of left atrial dysfunction].
BACKGROUND: Patients with non rheumatic atrial fibrillation (NRAF) have an increased risk for thromboembolic complications. Recent evidence suggests that left atrial appendage function (contraction, filling dynamics) may provide clues to the thrombogenic potential of this structure. The aim of this study was to identify left atrial spontaneous echocontrast and thrombus between patients with NRAF and their relationship with left atrial appendage function. METHODS: Transthoracic (TTE) and biplane or multiplane transesophageal echocardiography (TEE) were performed in 143 patients with chronic NRAF enrolled in the Trieste Area Study on non rheumatic Atrial Fibrillation (TASAF), an ongoing prospective community study with a follow-up period of 2 years. The maximal and minimal areas of the left atrial appendage were measured during three cardiac cycles and the peak emptying and filling velocities profile were obtained by pulsed wave Doppler at the orifice of the left atrial appendage. The left atrium and appendage were inspected for thrombus and spontaneous echocontrast. RESULTS: Left atrial appendage thrombus was present in 37 patients (26%) and spontaneous echocontrast in 60 patients (42%), 45% of patients with spontaneous echocontrast had thrombus. Univariate analysis identified positive correlation of thrombus with duration of atrial fibrillation (p = 0.05), hypertension (p = 0.01), left atrial area (p = 0.005), mitral annular calcification (p = 0.01), left ventricular dysfunction (p = 0.03) and a non significant correlation with the mitral valve prolapse (p = 0.08) in the TTE. The presence of mitral regurgitation did not demonstrate a protective effect (p = 0.73) against thrombosis. The variables of left atrial appendage function identifying a subgroup of patients with increased risk of thrombus formation were: shortening fraction of the area in the horizontal and vertical sections (p = 0.0001 and p = 0.002 respectively), the peak filling and emptying velocity in horizontal (p = 0.0001 equal for both) and vertical sections (p = 0.0001 equal for both). In summary these patients have a larger left atrial maximal area (p = 0.004) and a lower flow velocity profile (p < 0.00001) and more intense spontaneous echocontrast (p < 0.00001) than the others. Spontaneous echocontrast was correlated with left ventricular dysfunction (p = 0.008), left atrial area (p = 0.02) and there was a non-significant correlation with mitral annular calcification (p = 0.09) and lower left ventricular shortening fraction (p = 0.06). Transesophageal echocardiography variables have identified the subgroup of patients with an increased risk of echocontrast formation. This was positively associated with a low flow velocity profile (p = 0.0001), a left atrial appendage low shortening fraction in horizontal section (p = 0.001) and in vertical section (p = 0.05) and a low peak filling velocity in horizontal section (p = 0.003) and in vertical section (p = 0.004) and a low peak emptying velocity in horizontal section (p = 0.003) and in vertical section (p = 0.001). Prophylactic therapy with anticoagulant or antiplatelet agents has little benefits in our experience. CONCLUSIONS: Spontaneous echocontrast and low flow profile velocity (low peak emptying and filling velocity) and increased area of left atrial appendage were strongly associated with left atrial and/or appendage thrombus in patients with NRAF. The assessment of left atrial appendage function by TEE is an important component of the comprehensive evaluation of potentially increased risk of thrombus formation.
Aged↗
[Relationship between the force of left atrial ejection to left ventricular function in arterial hypertension].
UNLABELLED: The left atrial ejection force (LAEF), defined as that force exerted by the left atrium (LA) to accelerate the blood into the left ventricle during atrial systole, is well accepted for the evaluation of LA systolic function. The aim of this study is to determine whether LAEF is a precursor of the impairement of LV systolic function in patients with arterial hypertension (HTN). For that purpose we studied LAEF in 36 patients with HTN (av. age 58 +/- 8 years) with LV hypertrophy (Lvmi > 134 g/m2 for men and > 110 g/m2 for women). LV systolic function estimated by the fractional shortening (FSh) was 35 +/- 4% (28 to 44); 32 normal subjects (NS) were also analyzed. All subjects were submitted to echo and doppler examinations. METHODS: LAEF was obtained by the formula: 1/3 x MVA x (A-vel)2, where MVA is mitral valve area measured by 2D echo while A-vel. is the late diastolic (atrial) mitral velocity. RESULTS: 1. LAEF increased significantly with age in NS (r = 0.78) p < 0.05). Age corrected LEAF was calculated as % LEAF = (actual LAEF/normal LAEF x 100. 2. Compared to NS. % LAEF was lower in HTN (78 + 25%). 3. There was a significant inverse correlation between LAEF and LV wall thickness (r = -0.46) (p < 0.05). 4. % LAEF was 66 +/- 31% in patients with FSh < 33% and 79 +/- 25% in those with FSh > 33% (p < 0.05). 5. In HTN with the duration > 15 years, % LAEF was lower than in patients with < 15 years (62 +/- 25 vs 76 +/- 24) (p < 0.05). CONCLUSIONS: 1. LAEF is decreased in more advance stages of HTN. 2. This impairment is related to LV hypertrophy and to the duration of the disease. 3. LAEF is a sensitive precursor for LV systolic deterioration in patients with hypertension.
Adult↗
Atrial natriuretic peptide preserves endothelial function during intimal hyperplasia.
BACKGROUND: Atrial and C-type natriuretic peptides (ANP and CNP), acting through different receptors, have antiproliferative effects in vitro. Beneficial effects of CNP in vivo on early atherosclerosis have been described, but it is not known if ANP is antiproliferative in vivo. In the present study, the effects of chronic in vivo ANP were tested and compared with CNP on endothelial dysfunction and intimal thickening caused by peri-arterial collars. METHODS: Non-occlusive collars were placed bilaterally around the common carotid arteries of rabbits. One collar was filled with saline vehicle. The contralateral collar was filled with ANP or CNP (1 or 10 microM, n = 5-7) with slow replacement of peptide via mini-pump (1 or 10 fmol/h). RESULTS: After 7 days, endothelium-dependent vasorelaxation in saline-collared arteries was 33 +/- 3% of maximum [averaged over 0.03-1 muM acetylcholine (ACh)] compared to 64 +/- 2% in normal (uncollared) arteries (p < 0.05, n = 23). In vivo ANP restored the ACh relaxation to normal (e.g., 57 +/- 6%, 1 microM ANP), similar to effects seen with CNP in vivo. Endothelium-independent vasorelaxation of collared-vessels was not altered by either peptide. Intimal hyperplasia induced by the collars was not prevented by peri-arterial natriuretic peptides. In additional rabbits (n = 6), CNP (100 pmol/h) given directly into the lumen of collared carotid arteries for 7 days reduced neointima formation by 16 +/- 5% (p < 0.05), whereas ANP given intraluminally (100 pmol/h; n = 6) did not. CONCLUSIONS: The more potent actions of CNP on vascular smooth muscle cell migration and proliferation (established in vitro) may explain differences between the peptides on intimal hyperplasia in vivo. The major hallmark of atherosclerosis and restenosis, endothelial dysfunction, was prevented by chronic, peri-arterial administration of ANP or CNP.
Acetylcholine↗
Pressure-flow studies in man: effect of atrial systole on left ventricular function.
In order to evaluate the effects of atrial contraction on left ventricular function, the pressure gradient technique was used to measure instantaneous aortic blood flow and pressure in nine patients, six having complete heart block and three having normal sinus rhythm. From these data both left ventricular stroke volume and stroke work were calculated. Ventricular rate was controlled by transvenous right ventricular pacing over a range of 50-158 beats/min. At each heart rate, beats which were not preceded by a P wave served as controls. The other beats were divided into six groups according to the duration of the preceding PR interval. The results indicated that stroke volume and stroke work were always affected similarly. In one patient the presence of a P wave did not alter the subsequent stroke volume significantly. In the other patients, beats preceded by P waves had stroke volumes greater than the controls. In general, there was no difference in stroke volume for beats preceded by a P wave having a PR interval within the range of 0.05-0.20 sec. As the PR interval lengthened beyond 0.20 sec stroke volume tended to decrease, especially at more rapid heart rates. The absolute increase in stroke volume after a beat preceded by a P wave (PR interval 0.05-0.20 sec) was quite variable among the patients. For a given patient the absolute increase in stroke volume was essentially independent of heart rate. The percentage change in stroke volume, however, was always greater as the heart rate increased. These data indicate that in most patients atrial systole is important in augmenting ventricular stroke volume and stroke work especially at high heart rates, but the magnitude of these effects are quite variable among patients.
Adult↗
Left atrial versus left ventricular input function for quantification of the myocardial blood flow with nitrogen-13 ammonia and positron emission tomography.
Flow quantitation with nitrogen-13 ammonia ((13)NH(3)) and positron emission tomography (PET) is dependent on an accurate blood time-activity curve. This is conveniently derived from the PET images by drawing a region of interest in the left ventricular cavity. The blood time-activity curve obtained in this way, however, may contain spillover from the myocardial wall. The purpose of this study was to analyse the effect of wall to blood pool spillover. Additionally, we analysed the application of a left atrial input function. Using computer simulations, we investigated the effect of spillover from the myocardial wall to the left ventricular input function and the effect of time delay on the left ventricular input function. An oxygen-15 carbon monoxide PET study of seven normal volunteers was used to investigate possible recovery issues regarding the left atrial input function. Finally, (13)NH(3) studies of 31 normal volunteers during rest and dipyridamole stimulation were analysed using either a left atrial or a left ventricular input function. The simulation studies showed that myocardial wall to blood pool spillover causes a considerable underestimation of the regional blood flow values in hyperaemic flow studies. Neither time delay nor recovery issues prevent flow quantitation with a left atrial input function. The (13)NH(3) studies revealed no significant difference between the resting blood flow values, whereas the hyperaemic blood flow values were underestimated by 8% (P<0.01) on average (up to 40% individually) when using a left ventricular input function compared with a left atrial input function. Spillover of activity from the left ventricular wall to the blood time-activity curve is of importance in hyperaemic flow studies using (13)NH(3). Application of a left atrial input function is a possible solution to these issues.
Ammonia↗
[Function of the left atrial appendage after electrical cardioversion of atrial fibrillation to sinus rhythm].
INTRODUCTION: It is widely believed that atrial fibrillation appears in a secondly manner to atrial enlargement. Morfological alteration might be the source of disturbance of electrical activation and mechanical function to fibres that facilitate arrhythmia preservation as well as life threatening complications. THE OBJECTIVE: It is crucial to establish whether reversion of atrial fibrillation to sinus rhythm causes size diminishment and function improvement of the left atrial appendage, which creates hope to avoid dangerous complications, particularly systemic embolisation. DATA AND METHODOLOGY: 30 patients were qualified including 18 males and 12 females aged between 52 and 86 (average age was 63.81 +/- 9.22). All the patients suffered from nonrheumatic atrial fibrillation. The echocardiographic examination was conducted before reversion of atrial fibrillation, right after reaching sinus rhythm and after 6 months observation at sustained sinus rhythm. During the transesophageal echocardiographic examination the following parameters were investigated: LAApodł, LAApoprz, LAAobw, LAApole, LAAF, LAAB, LAAF intg, LAAB intg, spontaneous echocardiographic contrast, thrombus. RESULTS: Left atrial appendage size right after reversion of atrial fibrillation did not considerably differ from the values registered at the time of arrhythmia. It significantly diminished in the case of sustained stabilisation of sinus rhythm. The diminishment of the left atrial appendage size was connected with its function improvement expressed by increased maximum filling and emptying velocities as well as their integrals. SEC appearance frequency considerably increased right after reaching sinus rhythm. SEC appeared very rarely in the examination after 6 months. No single case of THR in LAA was noted. At the same time several cases of THR were disclosed both before and directly after restoration of sinus rhythm. CONCLUSIONS: Sinus rhythm restoration and its sustaining for a longer period of time results in size diminishing and function improvement of left atrial appendage. The stability of sinus rhythm is closely tied with thromboembolism risk factors.
Aged↗
Relationship of epicardial adipose tissue with atrial dimensions and diastolic function in morbidly obese subjects.
Obesity is associated with atrial dilation and diastolic dysfunction although the causative mechanisms are not completely understood. In this study we showed for the first time that increase in epicardial fat thickness is significantly correlated with atria enlargement and impairment in diastolic filling in morbidly obese subjects.
Adipose Tissue↗
Chronotropic response to exercise in patients with atrial fibrillation: relation to functional state.
OBJECTIVE: To determine the relation between functional capacity and heart rate response to exercise in patients with atrial fibrillation. SUBJECTS: 73 consecutive patients with chronic atrial fibrillation. MAIN OUTCOME MEASURES: Relation between functional capacity, measured as peak oxygen consumption (peak VO2; ml/min/kg), and heart rate at all stages of exercise in univariate and multivariate analyses. RESULTS: Peak VO2 showed no correlation with resting heart rate, but it showed a negative correlation with heart rate during the first stage of exercise (r = -0.94, p < 0.01). Indeed, heart rate during the early stages of exercise (stages 1-5) was higher in patients with a peak VO2 less than or equal to 20 ml/mm/kg than in those with a peak VO2 greater than 20 ml/min/kg (heart rate 140 v 125 beats/min, p < 0.05). At maximal exercise, however, peak VO2 was positively correlated with heart rate (r = 2.15, p < 0.0001). CONCLUSION: In patients with atrial fibrillation and impaired functional capacity heart rate at low levels of exercise is augmented but maximal heart rate attenuated compared with patients with preserved functional capacity. Excessive heart rate responses to minor exercise may have deleterious effects on left ventricular function and thereby further limit functional capacity.
Adrenergic beta-Antagonists↗
Refinement on single-beat determination of left ventricular systolic function in patients with atrial fibrillation.
Single-beat determination of left ventricular systolic function at a beat with equal subsequent cardiac cycles has been proposed as an accurate method in atrial fibrillation. However, there has still been substantial variability between the values calculated from beats with equal subsequent cycles. Therefore, some refinement on the single-beat method is needed. In 100 patients with atrial fibrillation, Doppler aortic flow time-velocity integral was determined for at least 20 consecutive cardiac cycles. The values at beats with equal subsequent cardiac cycles were chosen and compared with the average values over all cardiac cycles. The values at beats with cycle lengths shorter than 500 milliseconds were usually far below the average values over all cardiac cycles. Bland-Altman agreement analysis revealed improved accuracy by gradually narrowing the range of the limits of agreement when 2 or 3 beats with equal subsequent cycles and cycle lengths longer than 500 milliseconds were used for evaluation.
Atrial Fibrillation↗