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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↗
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↗
PubMed1985

Effects of pulmonary hemodynamics on lung function in adult patients with atrial septal defect.

To clarify the relationship of pulmonary function with differing severity of atrial septal defect (ASD) and to assess the effects of pulmonary hemodynamics on these functions, we classified 101 patients with adult ASD by their pulmonary arterial mean pressure (PAm) and pulmonary blood flow (Qp), and compared details of pulmonary functions between pairs of groups. Classification was by drawing lines at the PAm of 20 mmHg and the Qp of 10 L/min. Group I was the low pressure-low flow group, Group II the low pressure-high flow group, Group III the high pressure-low flow group, and Group IV the high pressure-high flow group. Vital capacity as the percentage of predicted (%VC) was low in Groups III and IV. There were no significant differences in the ratio of forced expiratory volume in one second to forced vital capacity (FEV1%), flow at 25% forced vital capacity and closing volume as the percentage of predicted (%V25, %CV/VC) between each group. Both maximum midexpiratory flow rate and flow rate at 50% forced vital capacity as the percentage of predicted (%MMEF, %V50) in Group III with the most severe ASD, were significantly low. Pulmonary diffusing capacities for carbon monoxide as the percentage of predicted (%DLco) exceeded 100% in all groups, and tended to decrease with increases of PAm without relation to Qp. Pulmonary dysfunctions in adult ASD were mainly due to restrictive changes accompanied by obstructive change in proportion to the decrease of VC. Peripheral airway obstructions are mild in ASD and these might be caused by lower pressure of left atrium and no existence of pulmonary venous congestion in ASD, even in the most severe group.

Adolescent↗
PubMed1983

Limiting factor for the initiation of reentrant tachycardia in concealed Wolff-Parkinson-White syndrome.

We studied the limiting factor for the initiation of reentrant tachycardia in 14 patients with concealed Wolff-Parkinson-White syndrome by comparing atrial refractoriness and echo times. When relatively late atrial premature beats (A2) were not accompanied by an atrial echo (Ae), the echo times were estimated from the antegrade A2-V2 conduction time of A2, since the retrograde conduction time via the accessory pathway remained constant regardless of the degree of prematurity. Thus, A2-Ae curves including the minimal echo time and the longest A2-Ae without Ae could be drawn in all patients. Then the curve was compared with the atrial effective refractory periods and the functional refractory periods of A2 in each patient. Atrial refractoriness which might limit the occurrence of an Ae is not that of basic beats (A1) but that of premature beats (A2). In all patients the atrial effective refractory periods of A2 were much shorter than the minimal echo time and the longest A2-Ae without Ae, suggesting that the atrial effective refractory period is not responsible for limiting the initiation of an Ae. Also in 13 of 14 patients, the atrial functional refractory periods were shorter than the minimal echo time and the longest A2-Ae without Ae. In one patient, the atrial functional refractory period was sandwiched between the minimal echo time and the longest A2-Ae without Ae suggesting the atrial functional refractory period of Ae might be responsible for limiting the occurrence of an Ae in this patient.

Adult↗
PubMed2005

[Functional assessment of the left atrial appendage with transesophageal echocardiography before and after percutaneous valvotomy in the mitral stenosis].

OBJECTIVE: To assess the effects of the relief of the mitral stenosis by percutaneous ballon valvotomy in the function of the left atrial appendage. METHODS: Twelve patients with symptomatic mitral stenosis, in sinus rhythm, were studied. They were submitted to the transesophageal echocardiogram before and after effective percutaneous ballon valvotomy. Concerning the left atrial appendage, the peak flow velocities and the respective integral of the anterograde and retrograde flow, in addition to the ejection fraction calculated through the planimetry of the area of that structure, were analyzed at the pulsatile Doppler. RESULTS: There was a significant increase of the anterograde flow velocity of the left atrial appendage after percutaneous ballon valvotomy (pre: mean of 0.30 m/s; post: mean of 0.47 m/s; p<0.05) and their respective integrals. The same happened with the retrograde flow velocity (pre: mean of 0.35 m/s, post: mean of 0.53 m/s; p<0.05). There was a tendency of increase of the ejection fraction of the left atrial appendage after the procedure (pre: mean of 20%, post: mean of 31%; p=0.08). CONCLUSION: The effective opening of the stenosed mitral orifice resulting from the percutaneous ballon valvotomy determined an improvement of the flow pattern of the left atrial appendage, which can potentially contribute for the reduction of the embolic risk.

Adolescent↗
PubMed2007

Effects of cardioversion of atrial fibrillation on endothelial function in hypertension or diabetes.

BACKGROUND: Cardioversion (CV) to sinus rhythm corrects endothelial dysfunction secondary to atrial fibrillation (AF). As AF often complicates hypertension and diabetes (disorders associated with impaired endothelial function) the study probed whether these comorbidities to AF produced an additive effect and to what extent CV might be advantageous. MATERIALS AND METHODS: Brachial artery flow-mediated dilatation (FMD) was evaluated before and after CV in 17 lone AF patients (group 1), 16 patients with AF + hypertension (group 2) and 17 patients with AF + diabetes type II (group 3), while in supine and head-up tilting (HUT) positions, as this is when endothelial vasodilation is emphasized as a counterbalance to neurogenic vasoconstriction. RESULTS: After 2 weeks, CV in group 1 increased (P < 0.01) supine FMD (from 7.22-->9.50%) and restored its HUT potentiation (from 9.31-->17.22%). In group 2, FMD also improved significantly with CV (supine from 4.92-->7.11% and HUT from 5.29-->11.83%; P < 0.01). In group 3, CV did not promote significant FMD changes (supine from 5.12-->4.92% and HUT from 4.98-->4.73%). After 3 months, FMD improvement persisted in groups 1 and 2 with enduring sinus rhythm, but not in those with AF relapse. In group 3, FMD remained unchanged regardless of cardiac rhythm. CONCLUSIONS: Cardioversion persistently increases supine shear stress endothelial responsiveness and restores the orthostatic modulation in AF alone or in association with hypertension, but not with diabetes. Differences in background endothelial impairment may explain the presence (hypertension) or the absence (diabetes) of an additive AF effect in comorbidities, as well as CV results.

Atrial Fibrillation↗
PubMed1988

Correlation of minimum coronary lumen diameter with left ventricular functional impairment induced by atrial pacing.

To understand whether quantitative measurement of minimal coronary luminal diameter is a better method than percent diameter narrowing for assessing the functional impairment of myocardial contractility produced by coronary artery stenoses, measurements were made from 37 stenotic segments in 27 patients with coronary artery disease and from corresponding segments in 10 subjects without coronary artery narrowing. An assessment of the reliability of the 2 types of measurements was made by correlating them with the physiologic parameters of both segmental wall motion and global ejection fraction response induced by atrial pacing. Digitally acquired coronary angiograms were used to facilitate quantitative analysis. Measurements by edge detection and videodensitometry correlated closely (r = 0.94). Percent diameter narrowing correlated moderately with the change in ejection fraction (r = -0.41) or with the change in segmental wall motion (r = -0.44). The measurement of minimal lumen diameter correlated with the change in global ejection fraction (r = 0.61) and did so even better with the change in segmental wall motion (r = 0.78, p less than 0.05). A minimal lumen diameter of less than or equal to 1.5 mm identified patients likely to have a functional impairment during atrial pacing as assessed by either global ejection fraction or segmental wall motion defects. We conclude that minimal coronary luminal diameter provides a better method than percent diameter narrowing calculations to measure the anatomic severity of coronary artery narrowing.

Angiography↗
PubMed2006

Left atrial appendage-flow velocity predicts cardioversion success in atrial fibrillation.

Restoration of sinus rhythm by electrical cardioversion is a therapeutic option in appropriately selected patients with atrial fibrillation. It is important to determine predictors of electrical cardioversion outcome in patients with atrial fibrillation. Predictive value of clinical and conventional echocardiographic parameters for predicting cardioversion outcome is limited. The role of left atrial appendage (LAA) function, which may reflect left atrial contractile function, for prediction of cardioversion outcome remains unclear. We conducted a single center prospective study to evaluate the role of LAA function for prediction of cardioversion success in patients with atrial fibrillation. One hundred sixty three patients with atrial fibrillation underwent transthoracic and transesophageal echocardiography (TEE) before electrical cardioversion. LAA functions, including LAA peak flow velocity, LAA area and LAA ejection fraction, were examined. Cardioversion was successful in 133 patients and unsuccessful in 30 patients. Mean LAA peak emptying flow velocity was significantly higher in the patients with successful cardioversion than in those with unsuccessful cardioversion (0.34 +/- 0.14 vs 0.27 +/- 0.1 m/sec; p = 0.013). At multivariate logistic regression analysis, only LAA flow velocity (> 0.28 m/sec, odds ratio = 2.8 ; p = 0.03) proved to be an independent predictor of cardioversion success. LAA area (p = 0.18) and LAA ejection fraction (p = 0.52) were not different between successful and unsuccessful cardioversion groups. Therefore, measurement of LAA flow velocity provides valuable information for prediction of cardioversion outcome in patients with atrial fibrillation before TEE guided cardioversion.

Aged↗
PubMed1994

Functional significance of angiotensin receptors in human myocardium. Significant differences between atrial and ventricular myocardium.

We studied the effects of angiotensin (Ang) I and II in a variety of isolated human cardiac tissues contracting under physiological conditions (37 degrees C, 60 beats.min-1). Ang I and II consistently increased the peak developed force of human atrial muscles by 30-40%, an effect that was completely blocked by 10(-6) M saralasine, but not by the combination of prazosin and propranolol. However, neither Ang I or II had significant inotropic effects in right and left ventricular human preparations. We were also able to demonstrate that the positive inotropic effect of Ang II in human right atrial tissue is mediated by the AT1 receptor subtype but not the AT2 receptor subtype.

Angiotensin I↗
PubMed1975

Atrial receptors and renal function.

The hypothesis that receptors in the heart or pulmonary vasculature initiate a reflex that influences urine flow was derived from experiments designed to evaluate the effect of mechanical ventilation on renal function. These experiments indicated that urine flow usually decreases during positive-pressure breathing and usually increases during negative-pressure breathing. It was surmised that impulses from certain cardiopulmonary receptors affect the secretion of ADH, which in turn influences urine flow. A subsequent investigation appeared to localize the pertinent receptors to the left atrium, but the results of this particular investigation were influenced by several complication factors that have not been widely appreciated. The apparent localization of volume-regulating recpetors to the left atrium and the accumulating evidence that atrial receptors do respond to changes in atrial pressure or atrial volume triggered a myriad of further studies on the function of left receptors. Nearly all these studies employed indirect techniques that produced changes in systemic and pulmonary hemodynamics in addition to changes in left atrial pressure. Nevertheless, it often was assumed that if changes in left pressure were produced, any concomitant changes in circulating ADH or in urine flow were attributable to a reflex elicited from atrial receptors. Mush of the data obtained were interpreted as being compatible with the elft atrial volume-receptor hypothesis, but very liggle of the data pertained to left atrial receptors specifically.

Animals↗
PubMed2002

Regulation of ANP secretion by cardiac Na+/Ca2+ exchanger using a new controlled atrial model.

The myocardial interstitium is important in regulating cardiac function. Between the atrial lumen and the pericardial space are transmural pathways, and movement of interstitial fluid (ISF) through these pathways is one of the main driving forces regulating translocation of substances from the interstitium into the blood. To define how ISF translocation from the interstitial space into the luminal space is regulated by each component of atrial hemodynamics, we devised a new rabbit atrial model in which each physical parameter could be controlled independently. Using this system, we also defined the physiological role of the cardiac Na(+)/Ca(2+) exchanger on secretion of atrial natriuretic peptide (ANP) by depletion of extracellular Na(+) ([Na(+)](o)). Increases in stroke volume and atrial end-systolic volume increased ISF translocation and ANP secretion. However, an increase in atrial rate did not influence ISF translocation but, rather, increased ANP secretion. Gradual depletion of [Na(+)](o) caused gradual increases in ANP secretion and intracellular Ca(2+) ([Ca(2+)](i)), which were blocked in the presence of Ca(2+)-free buffer and Ni(2+), but not in the presence of KB-R7943, diltiazem, mibefradil, caffeine, or monensin. Amiloride and its analog blocked an increase in ANP secretion but not an increase in [Ca(2+)](i) by [Na(+)](o) depletion. Therefore, we suggest that ANP secretion and ISF translocation may be differently controlled by each physical factor. These results also suggest that the increase in ANP secretion in response to [Na(+)](o) depletion may involve inhibition of Na(+)/Ca(2+) and Na(+)/H(+) exchangers but not an increase in [Ca(2+)](i).

Animals↗
PubMed1992

Left ventricular function and the relationship between left atrial pressure and peak early diastolic filling velocity in dog.

OBJECTIVE: The aim was to clarify the roles of left atrial pressure and ventricular function in the determination of early diastolic filling. METHODS: Various grades of ventricular dysfunction were made in 12 mongrel dogs by coronary microembolization under pentobarbitone anaesthesia. Left atrial pressure was altered by volume loading. Peak early diastolic filling velocity was measured using pulsed Doppler echocardiography. Ventricular fractional shortening was measured using M mode echocardiography. RESULTS: Peak early filling velocity increased as left atrial pressure increased. There was a direct relationship between mean left atrial pressure and the velocity before and after induction of ventricular dysfunction. The slope of the regression line between mean left atrial pressure and peak early filling velocity decreased as the grade of the dysfunction increased. There was a significant correlation between the slope of the regression line and mean left ventricular fractional shortening (r = 0.65, n = 31, p less than 0.01). CONCLUSIONS: Early diastolic filling was affected by both left atrial pressure and left ventricular function. These facts are useful in interpreting the various transmitral flow patterns observed clinically.

Animals↗
PubMed2000

Time course of recovery of left atrial mechanical dysfunction after cardioversion of spontaneous atrial fibrillation with the implantable atrial defibrillator.

The effect of the timing of cardioversion of atrial fibrillation on left atrial mechanical function was studied in 11 patients treated with the implantable atrial defibrillator. Results of this study suggested that prompt cardioversion of spontaneous episodes of atrial fibrillation within 48 hours after onset was associated with early resolution of left atrial mechanical dysfunction seen after cardioversion.

Aged↗
PubMed2005

Doppler echocardiographic prediction of recurrent atrial fibrillation following cardioversion.

BACKGROUND: Cardioversion for atrial fibrillation (AF) is associated with impairment of left atrial mechanical function and increased risk of thrombus formation with subsequent embolisation. Measuring atrial mechanical function is of interest to determine the individual risk of thromboembolism and the risk of recurrent AF. METHODS: We included 112 consecutive patients with AF and planned cardioversion. Serial echocardiographic measurements of left atrial size and Doppler measurement of mitral valve peak A wave velocities were obtained at days 0, 1, 2, 3, and 28 following cardioversion. These measurements and clinical parameters were related to clinical events and recurrent AF within 4 weeks following cardioversion. Cardioversion was achieved in 100 patients. RESULTS: AF-recurrence within 4 weeks was 23.9% and 45.8% for patients with < or = and > 6 weeks AF-duration, respectively (p=0.04). Peak A wave velocities were significantly lower up to 2 days following cardioversion in patients with AF-recurrence. A peak A wave velocity < 52 cm/s at day 1 resulted in an odds ratio of 5.0 (95% CI: 1.4-18.6) for recurrence of AF. In multiple logistic regression analysis, peak A wave velocity at day 1 remained the only independent predictor of recurrent AF. Left atrial diameter did not correlate with recurrence of AF. CONCLUSIONS: A single measurement of mitral peak A wave velocity 1 day following cardioversion is predictive of AF recurrence. This method is feasible for risk estimation with potential therapeutic implications.

Atrial Fibrillation↗
PubMed1996

Left atrial enlargement in healthy obese: prevalence and relation to left ventricular mass and diastolic function.

BACKGROUND: Left atrial (LA) enlargement has been reported in the obese. However, its prevalence in the healthy obese, clinical correlates and relation to left ventricular (LV) mass and diastolic function have been little investigated. METHODS: Thirty-five consecutive, healthy, normotensive obese (body mass index greater than 28, mean +/- SD 34.2 +/- 2.3 kg/m2) and 35 nonobese subjects (body mass index 24.6 +/- 2.3 kg/m2) comparable in age and sex underwent echocardiographic measurements of LA posteroanterior (parasternal view), mediolateral and superoinferior (apical views) dimensions, aortic root diameter, LV mass and Doppler assessment of LV diastolic function. LA enlargement was defined as a posteroanterior dimension greater than 40 mm. A ratio of LA posteroanterior dimension to aortic root diameter greater than 1.4 was used as an index for disproportionate LA enlargement. RESULTS: LA enlargement was more frequent in the obese than in the nonobese (37% versus 6%, P<0.0001). Similarity, disproportionate LA enlargement was more frequent in the obese (34% versus 6%, P<0.0001). LA posteroanterior dimension correlated well with body mass index (r=0.52, P<0.0001) and LV mass (r=0.56, P<0.0001), and weakly with blood pressure (r=0.28, P<0.02). There was no significant correlation with LV diastolic function, age or sex. In multivariate analysis (multiple r=0.61, P<0.0001), LA posteroanterior dimension correlated significantly only with mass (P<0.005), and the association with body mass index and blood pressure became nonsignificant. Similar results were obtained when LA posteroanterior dimension was replaced with mediolateral or superoinferior dimensions. CONCLUSIONS: LA enlargement is frequent in the normotensive, otherwise healthy obese and correlates well with LV mass. It is not mediated through impairment of LV diastolic function, and likely reflects a physiological adaptation of the heart to the obese state. Further studies are needed to determine whether LA enlargement in the obese is associated with adverse long term outcome.

Adult↗
PubMed2000

Sinus nodal function and risk for atrial fibrillation after coronary artery bypass graft surgery.

BACKGROUND: Nonsurgical patients with sinus node dysfunction are at high risk for atrial tachyarrhythmias, but whether a similar relation exists for atrial fibrillation after coronary artery bypass graft surgery is not clear. The purpose of this study was to evaluate sinus nodal function before and after coronary artery bypass graft surgery and to evaluate its relation with the risk for postoperative atrial arrhythmias. METHODS: Sixty patients without complications having elective coronary artery bypass graft surgery underwent sinus nodal function testing by measurement of sinoatrial conduction time (SACT) and corrected sinus nodal recovery time (CSNRT). Patients were categorized based on whether postoperative atrial fibrillation developed. RESULTS: Twenty patients developed atrial fibrillation between postoperative days 1 through 3. For patients remaining in sinus rhythm (n = 40), sinoatrial conduction times were no different and corrected sinus nodal recovery times were shorter after surgery when compared with measurements obtained after anesthesia induction. Sinus node function test results before surgery were similar between the sinus rhythm and the atrial fibrillation groups. After surgery, patients who later developed atrial fibrillation had longer sinoatrial conduction times compared with the sinus rhythm group (P = 0.006), but corrected sinus nodal recover time was not different between these groups. A sinoatrial conduction time > 96 ms measured at this time point was associated with a 7.3-fold increased risk of postoperative atrial fibrillation (sensitivity, 62%; specificity, 81%; positive and negative predictive values, 56% and 85%, respectively; area under the receiver operator characteristic curve, 0.72). CONCLUSIONS: These data show that sinus nodal function is not adversely affected by uncomplicated coronary artery bypass surgery. Patients who later developed atrial fibrillation, however, had prolonged sinoatrial conduction immediately after surgery compared with patients remaining in sinus rhythm. These results suggest that injury to atrial conduction tissue at the time of surgery predisposes to postoperative atrial fibrillation and that assessment of sinoatrial conduction times could provide a means of identifying patients at high risk for postoperative atrial fibrillation.

Aged↗