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PubMed1990

Interrelationship of atrial natriuretic peptide, atrial volume, and renal function in premature infants.

Infants experience dramatic changes in fluid balance during the first few days of life, which provides an opportunity to observe the interrelationships of changing atrial size, atrial natriuretic peptide (ANP) secretion, and renal function during a relatively short period. To study these relationships, we examined nine infant boys (mean birth weight 1180 gm and gestational age 30 weeks) at 20 to 28 hours of age and then at four 24-hour intervals. Measurements included plasma ANP concentration, two-dimensional echocardiographic estimations of left and right atrial volumes, Doppler determination of ductus arteriosus patency, creatinine clearance, urine flow rate, urinary sodium excretion, and cyclic guanosine monophosphate (cGMP) excretion. Plasma ANP concentration was found to decrease with age and to correlate with decreasing size of the right atrium, closure of the ductus arteriosus, urinary cGMP excretion, and sodium excretion. We speculate that elevated plasma ANP values in a preterm neonate reflect an expanded volume state. As volume contraction, reflected by decreasing atrial volume and body weight occurs, ANP levels decrease, which may diminish diuresis. These findings are compatible with a significant role for ANP in volume homeostasis of newborn infants.

Atrial Natriuretic Factor↗
PubMed1992

[Clinico-functional correlations of left atrial myocardial excursions in patients with mitral valve defects].

The pre- and intraoperative drug maintenance was evaluated in 50 patients with mitral valvular disease and compared with the types of left atrial myocardial excursions. The maintenance with cardiac glycosides and diuretics was greatly different in 3 groups of patients with various types of left atrial myocardial excursions. In patients with Type I excursions the maintenance was minimal, in those with Type III excursions it was maximal, those with Type II excursions, it was intermediate. It is concluded that the functional characteristics of left atrial myocardial excursions may be used as an indicator of cardiac performance.

Adolescent↗
PubMed1996

Concomitant mitral valve or atrial septal defect surgery and the modified Cox-maze procedure.

Atrial fibrillation (AF) is generally associated with rheumatic valve disease and atrial septal defects (ASD) in young adults. Surgical correction of both disorders fails to convert to sinus rhythm or prevent further episodes of paroxysmal or chronic AF in most patients. The role and efficacy of combining mitral valve surgery or ASD correction with AF surgery in this setting has not been widely addressed and remains to be established. The present study prospectively assessed the recovery of sinus rhythm, functional status, and atrial function in 21 patients (mean age 42 +/- 9.2 years) who underwent a modified Cox-maze procedure concomitant with mitral valve or ASD surgery at our institution between March 1993 and February 1995. Seventeen (81%) had chronic AF, and 4 (19%) had paroxysmal AF, with a mean AF duration of 3.5 +/- 3.6 years (range 0.6 to 15.3). Concomitant surgery was performed in 9 patients (42.9%) with mitral stenosis, 5 (23.8%) with mitral regurgitation, 1 (4.8%) with mitral and aortic regurgitation, and 3 (14.3%) with ASD. Eighteen patients (86%) were in New York Heart Association class II to IV before operation. Doppler echocardiography was performed in all patients before surgery, and 1 week, and 3 and 6 months after surgery in patients maintaining sinus rhythm. One patient with severe mitral stenosis and depressed ventricular function died in the immediate postoperative period. Sinus rhythm was restored in the immediate postoperative period in 7 patients (35%), and in another 10 patients (50%) before discharge (mean 5.8 +/- 2 days). Overall, sinus rhythm was restored before discharge in 17 patients (85%); 3 (15%) patients required antiarrhythmic therapy. Doppler echocardiography performed 3 months after surgery documented atrial contractility (A and E waves) in 12 patients (71%). After a mean follow-up period of 8 months (range 3 to 23), 18 (90%) remained in sinus rhythm. Sinus rhythm was successfully restored and maintained in most patients with drug refractory AF undergoing a concomitant Cox-maze procedure with mitral valve or ASD surgery improving atrial function and New York Heart Association class.

Adult↗
PubMed1994

Influence of acutely altered loading conditions on left atrial appendage flow velocities.

OBJECTIVES: The purpose of this study was to identify the effects of altered loading conditions on left atrial appendage flow velocities. BACKGROUND: Although studies have suggested that Doppler analysis of left atrial appendage blood flow may have clinical utility, the hemodynamic and cardiac mechanical determinants of left atrial appendage flow are poorly understood. METHODS: Transesophageal Doppler echocardiography was performed in eight atrially paced anesthetized dogs instrumented with sonomicrometers on the left atrial appendage and the left ventricular minor axis and with left atrial and left ventricular micromanometers. Left atrial appendage emptying and filling velocities corresponding to early and late ventricular diastole, respectively, were measured using volume expansion and phenylephrine infusion. RESULTS: Volume infusion caused a significant decrease in the early to late emptying and filling ratios (mean +/- SD 0.85 +/- 0.24 vs. 0.46 +/- 0.17 and 0.80 +/- 0.50 vs. 0.40 +/- 0.20, both p < 0.05). By contrast, phenylephrine infusion did not significantly alter either filling or emptying ratio. The independent determinants of each flow wave were identified with multiple regression analysis: early emptying velocity--time constant of left ventricular relaxation, left ventricular end-systolic dimension and aortic pressure (r = 0.75, p < 0.001); late emptying velocity--left ventricular peak positive time derivative of left ventricular pressure (dP/dt) and fractional shortening (r = 0.74, p < 0.001); early filling velocity--left atrial appendage shortening fraction (r = 0.45, p = 0.01) and late filling velocity--left atrial appendage lengthening rate and left ventricular fractional shortening (r = 0.56, p < 0.01). CONCLUSIONS: These results indicate that 1) both the magnitude and the pattern of left atrial appendage emptying and filling velocities are dependent on loading conditions, and 2) left atrial appendage velocities are influenced to a greater extent by changes in left ventricular than in left atrial appendage function. These findings may have implications for the pathogenesis of left atrial appendage thrombi.

Animals↗
PubMed2005

Map-guided surgery for atrial fibrillation.

BACKGROUND: Although current surgical procedures result in a high success rate for atrial fibrillation, they are not guided by electrophysiologic findings in individual patients and thus might include unnecessary incisions in some patients or be inappropriate for other patients. We sought to determine whether intraoperative mapping is beneficial for the surgical treatment of atrial fibrillation. METHODS: A 256-channel 3-dimensional dynamic mapping system with custom-made epicardial patch electrodes was used to examine the atrial activation during atrial fibrillation and to determine the optimal procedure in 37 patients with continuous and 9 patients with intermittent atrial fibrillation intraoperatively. RESULTS: Surgical intervention for atrial fibrillation was not indicated in 3 patients in whom the atrial electrograms had a low voltage over a broad area. Concurrent, multiple, and repetitive activations arising from the pulmonary veins or left atrial appendage were observed in all patients. A simple left atrial procedure consisting of pulmonary vein isolation and left atrial incisions without any right atrial incisions was performed in 8 patients in whom the right atrial activation was passive, and all (100%) were cured of atrial fibrillation. The radial procedure was performed in the remaining 35 patients, and 31 (89%) of the patients were cured of atrial fibrillation. In this subset of patients, 10 exhibited reentrant or focal activation in the posterior left atrium between the right and left pulmonary veins and required an additional linear ablation on the posterior left atrium. The total amount of postoperative bleeding after the simple left atrial procedure was significantly less than after the radial procedure (378 +/- 135 vs 711 +/- 364 mL, P = .03). The right and left atrial transport functions were well preserved after both the radial and simple left atrial procedures. CONCLUSION: Intraoperative mapping facilitates determining the optimal procedure for atrial fibrillation in each patient.

Aged↗
PubMed1988

Effect of atrial peptide on collecting duct function.

1. The effects of synthetic rat atrial natriuretic peptides (ANP) on diffusional 22Na+, 36Cl- and tritiated water (THO) permeability of in vitro microperfused rat papillary collecting ducts and the effect in vivo of ANP on stop-flow sodium concentrations in the terminal segment of rabbit nephrons were studied. 2. The addition of 4 x 10(-8) or 4 x 10(-7) mol/l ANP to the medium or perfusion solution did not alter diffusional 22Na+ or 36Cl- permeability of microperfused rat papillary collecting ducts. 3. The basal diffusional THO permeability of papillary collecting ducts was not altered when 4 x 10(-7) mol/l ANP was present in the medium and did not inhibit the increment in diffusional THO permeability induced by vasopressin or reduce the permeability to water in a duct previously stimulated by vasopressin. 4. The administration of ANP (2 micrograms/kg bodyweight) to rabbits in water diuresis did not alter systemic blood pressure but induced a marked natriuresis and increases in urine flow and potassium excretion. This natriuresis was not associated with alterations in stop-flow sodium reabsorptive capacity or sodium permeability of the collecting tubules and ducts. 5. Previously reported in vivo clearance data suggest that ANP causes, at least in part, a natriuresis by altering sodium transport in the medullary collecting ducts. In this study, however, a direct effect could not be demonstrated and it is possible that the medulla needs to be functioning in its normal environment for such effects to be demonstrated.

Animals↗
PubMed1995

Effects of atrial pacing site on rate-dependent AV nodal function in rabbit hearts.

The functional origin of the changes in atrioventricular (AV) nodal function with the atrial pacing site was studied in isolated rabbit heart preparations. The rate-dependent AV nodal properties of recovery, facilitation, and fatigue were characterized with premature stimulation protocols repeated for each of three atrial pacing sites (upper atrium, low crista terminalis, and low interatrial septum). The effects of the atrial pacing site, reference site from which the beginning of nodal activation is measured (low crista and low septum) and stimulation protocol on nodal conduction and refractory parameters, were assessed with multifactorial analyses of variance. The changes in nodal parameters with the stimulation protocol did not differ significantly with the pacing site, indicating that the rate-dependent nodal properties are not affected by the atrial origin of the impulse. Only the baseline value of nodal parameters varied with the atrial pacing and reference site. However, the comparison of data obtained while the low crista was the pacing and reference site to those obtained while the low septum was the pacing and reference site yield no statistically significant differences, thus indicating that changes in perinodal activation were largely responsible for the observed changes in baseline. Upper atrial and low crista pacing yielded very similar data. We conclude that 1) the atrial pacing site affects perinodal activation but not rate-dependent nodal function, 2) the two inputs are equally effective in activating the AV node, and 3) input summation is a minor factor in rate-dependent nodal function.

Animals↗
PubMed2003

Identification of functional block line in atrial flutter using three-dimensional intracardiac echocardiography.

The crista terminalis (CT) is reportedly a critical barrier for maintaining typical atrial flutter (AFL), but recent observations have suggested the presence of posteromedial functional block, as well as crista conduction. Therefore, this study was designed to identify the correlation between the posterior boundary of AFL and anatomical architecture in the human right atrium (RA) using 3-dimensional (D) intracardiac echocardiography (ICE). In 11 patients with AFL (typical 9, reverse typical 2), mapping with a 10-pole (n=5) or 32-pole (n=6) catheter was performed during AFL. ICE was used to determine the catheter's position relative to the intra-atrial structures. In all patients, double potentials were recorded at the posteromedial RA and the catheter positions were recognized as posterior to the CT by 3-D ICE. Double potentials were not recorded on the CT, and the activation sequence revealed a craniocaudal direction in the 9 patients with typical AFL and caudocranial direction in the 2 patients with reverse typical AFL. These findings demonstrate that the posterior boundary of the AFL circuit is in the sinus venosa region posterior to the CT, which may provide an important insight into the mechanism of maintaining AFL.

Adult↗
PubMed1995

Excitation and contraction in atrial and ventricular myocardium of the guinea-pig.

Several parameters of excitation-contraction coupling were compared in two types of muscle, using thin strips from the left atria and papillary muscles from the right ventricles of guinea-pigs. (1) The duration of the action potential and twitch is much longer in ventricular than in atrial muscle. (2) Mechanical restitution can usually be described by a monoexponential function in ventricular and biexponential function in atrial muscle. (3) Post-extrasystolic potentiation, when related to the steady state force, is greater in ventricular muscle. (4) When priming with paired-pulse stimulation, mechanical restitution can be studied after the short interval and after the long interval. In atrial muscle, mechanical restitution is very similar after the short and long intervals but in ventricular muscle they are different in size. (5) Ryanodine (10(-6) M) can decrease the steady state force to about 10% of control in atrial but only to about 35% in ventricular muscle. Ryanodine (10(-8) M) causes the slow phase of restitution in atrial muscle to disappear but in ventricular muscle only increases the rate of mechanical restitution. (6) Ca-antagonists (Cd2+ 0.2 mM) can decrease the steady state force to zero in atrial and ventricular muscle. Ca-antagonists, in low concentrations (Cd2+ 0.01 mM), mainly affected the fast phase of mechanical restitution. (7) The recirculation fraction of calcium was about 0.64 in atrial and 0.27 in ventricular muscle. The findings are discussed in the light of known ultrastructural differences between atrial and ventricular myocardium.

Animals↗
PubMed1991

Effect of manganese (II) bis(glycinate)dichloride on Ca2+ channel function in cultured chick atrial cells.

Manganese (II) bis(glycinate)dichloride (Mn(glycinate)2) is a coordination complex of manganese with application as a contrast enhancement agent for magnetic resonance imaging in the heart. To determine the cardioactivity of the manganese ion in this chelation cage, the effects of Mn(glycinate)2 on Ca channel function in the cultured chick atrial cell was studied. Mn(glycinate)2 decreased amplitude of contraction in chick atrial cells from embryos 14 days in ovo with complete inhibition of beating at 1 mM and half-maximal effect at 0.1 mM. Under control conditions, Bay K 8644, a Ca channel activator increased amplitude of contraction by 86% with a half maximal effect at 3.2 x 10(-7) M. In the presence of 0.025 mM Mn(glycinate)2, a concentration which had no effect on the amplitude of contraction, the maximum response to Bay K 8644 was decreased to 31%. Mn(glycinate)2 had no effect on the EC50 for the response to Bay K 8644, 1.7 +/- 0.1 x 10(-9) M (S.E.M., n = 4) in control cells compared to 2.2 +/- 0.4 x 10(-9) M (S.E.M., n = 4) in cells incubated with Mn(glycinate)2. 45Ca2+ uptake over 5 min in cultured chick atrial cells decreased from 2.0 nmol/mg protein in control cells to 1.5 nmol/mg protein in the presence of 10(-5) M PN200-110, a Ca2+ channel blocker, a decrease of 28%. 45Ca2+ uptake decreased to 0.94 nmol/mg protein (53%) in the presence of 1 nmol Mn(glycinate)2. Effects of Mn(glycinate)2 and PN200 were not additive. These data demonstrate that Mn(glycinate)2 exerts its negative inotropic effect, at least partially, by interfering with the function of the L-type Ca channels at high concentrations.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1970

Effect of Peruvosid (CD412) on excitability and functional refractory period of atrial and ventricular tissues in cardiomyopathy caused by Trypanosoma cruzi.

Attempts were made to produce myocarditis by Trypanosoma cruzi inoculation in healthy dog puppies 6 to 8 weeks old. Significant electrocardiographic abnormalities were produced, coinciding with interstitial inflammatory processes in the cardiac tissue and with degenerative changes in the myocardial fibres. In puppies showing these changes, profound changes in the excitability and the functional refractory period of the atrial and ventricular muscular tissue were observed. The administration of Peruvosid in doses of 0.0240 to 0.0647 mg./kg. tended to diminish the excitability, previously increased by the inflammatory process, at the same time increasing the functional refractory period duration which had previously been shortened. The fact that Peruvosid corrects these fundamental factors in the genesis of cardiac arrhythmias suggests that the drug may be useful in the treatment of cardiac insufficiency produced by Chagas' myocardiopathy, in which arrhythmias are one of the basic characteristics.

Animals↗
PubMed2000

Atrial lead placement during atrial fibrillation. Is restitution of sinus rhythm required for proper lead function? Feasibility and 12-month functional analysis.

Unexpected atrial fibrillation (AF) during implantation of an atrial pacemaker lead is sometimes encountered. Intraoperative cardioversion may lengthen and complicate the implantation process. This study prospectively investigates the performance of atrial leads implanted during AF (group A) and compares atrial sensing and pacing properties to an age- and sex-matched control group in which sinus rhythm had been restored before atrial lead placement (group B). Patient groups consisted of 32 patients each. All patients received DDDR pacemakers and bipolar, steroid-eluting, active fixation atrial leads. In patients with AF at the time of implantation (group A), a minimal intracardiac fibrillatory amplitude of at least 1.0 mV was required for acceptable atrial lead placement. In patients with restored sinus rhythm (group B), a voltage threshold < 1.5 V at 0.5 ms and a minimal atrial potential amplitude > 1.5 mV was required. Patients of group A in whom spontaneous conversion to sinus rhythm did not occur within 4 weeks after implantation underwent electrical cardioversion to sinus rhythm. Pacemaker interrogations were performed 3, 6, and 12 months after implantation. In group A, implantation time was significantly shorter as compared to group B (58.7 +/- 8.6 minutes vs 73.0 +/- 17.3 minutes, P < 0.001). Mean atrial potential amplitude during AF was correlated with the telemetered atrial potential during sinus rhythm (r = 0.49, P < 0.001), but not with the atrial stimulation threshold. Twelve months after implantation, sensing thresholds (1.74 +/- 0.52 mV vs 1.78 +/- 0.69 mV, P = 0.98) and stimulation thresholds (1.09 +/- 0.42 V vs 1.01 +/- 0.31 V, P = 0.66) did not differ between groups A and B. However, in three patients of group A, chronic atrial sensing threshold was < or = 1 mV requiring atrial sensitivities of at least 0.35 mV to achieve reliable atrial sensing. Atrial lead placement during AF is feasible and reduces implantation time. However, bipolar atrial leads and the option to program high atrial sensitivities are required.

Aged↗
PubMed1990

Comparison of atrial contribution to cardiac hemodynamics in patients with normal and severely compromised cardiac function.

The importance of atrial contribution to cardiac function in patients with congestive heart failure is controversial. Ten patients with severe congestive failure (Group A) and 10 patients with normal ventricular function (Group B) were studied during atrial and ventricular pacing. Left ventricular ejection fraction, baseline pulmonary capillary wedge pressure, and baseline cardiac index were different between Group A and Group B patients: 22 +/- 10 vs. 65 +/- 11 (p less than 0.01); 21 +/- 5 vs. 8 +/- 4, (p less than 0.01); and 2.8 +/- 0.5 vs. 3.5 +/- 1.0 (p = 0.05). Compared with atrial pacing, cardiac index decreased from 2.8 +/- 0.6 to 2.2 +/- 0.5 (p less than 0.01) in Group A and from 3.6 +/- 0.7 to 2.9 +/- 0.5 (p less than 0.01) in Group B, during ventricular pacing. Pulmonary capillary wedge pressure increased by similar amounts in both groups during ventricular pacing. The change in cardiac index, % change in cardiac index, and change in pulmonary capillary wedge pressure from atrial to ventricular pacing, were not different between Group A and Group B patients. By logistic regression analysis, no association was found between the % change in cardiac index and the following variables: left ventricular ejection fraction, left ventricular end-diastolic volume, baseline pulmonary capillary wedge pressure, change in pulmonary capillary wedge pressure, and baseline cardiac index. The atrial contribution to resting steady-state cardiac function is similar between patients with severe congestive failure and those with preserved ventricular function.

Atrial Function↗
PubMed2001

Long-term assessment and serial evaluation of cardiorespiratory exercise performance and cardiac function in patients with atrial switch operation for complete transposition.

BACKGROUND: At present, a considerable number of patients survive who underwent an atrial switch operation for correction of complete transposition. Our study aimed to assess their long-term exercise performance and the serial evolution of cardiac function. METHODS: We studied 22 patients 5 to 17 years after an atrial switch operation, and followed them serially for 3.5 +/- 2 years after the first evaluation. Cardiorespiratory exercise function was assessed by analysis of gas exhange and by determination of the ventilatory anaerobic threshold. Echocardiography was performed on all evaluations. RESULTS: All patients were in Class I of the classification of the New York Heart Association at all assessments. Ventilatory anaerobic threshold, however, was significantly lower than normal. It averaged 77.9% +/- 13.7 of the normal mean value at the initial evaluation, and remained stable when re-evaluated later (76.2 +/- 13.7%). At the initial study, the increase in oxygen uptake during graded exercise was below the 95% confidence limit in 6 of the patients, and was below this level in 10 patients at re-assessment. The subnormal values for oxygen uptake during submaximal exercise were associated with moderate to severe haemodynamic dysfunction. At echocardiography, 15 of 17 patients studied twice had mild to moderate right ventricular dilation and tricuspidregurgiation, which remained virtually the same at reasssesment. A stable sinus rhythm was initially present in 17 patients, and persisted in 15 patients during follow-up. CONCLUSION: At medium term follow-up, cardiorespiratory exercise performance remains stable in patients after atrial switch repair. Serial exercise testing appears useful, because in individual patients in the present study, a decreasing exercise tolerance correlated with development of haemodynamic sequels.

Adolescent↗
PubMed2001

Atrial size reduction as a predictor of the success of radiofrequency maze procedure for chronic atrial fibrillation in patients undergoing concomitant valvular surgery.

INTRODUCTION: Previous studies showed that the surgical maze procedure can restore sinus rhythm and atrial transport function in patients with chronic atrial fibrillation (AF). However, no previous studies discussed the association of atrial size reduction and the success of sinus conversion by the radiofrequency (RF) maze procedure for chronic AF. METHODS AND RESULTS: A total of 119 chronic AF patients undergoing valvular operations were included in this study. Sixty-one patients received RF and cryoablation to create lesions in both atria to simulate the surgical maze II or III procedure (RF maze II or RF maze III; 13 patients, group 1) or a modified maze pattern (RF maze "IV"; 48 patients, group 2). The other 58 patients who underwent valvular operations alone without the maze procedure served as control (group 3). At 3-month follow-up after operation, sinus rhythm was restored in 73%, 81%, and 11% of patients in groups 1, 2 and 3, respectively. Preoperative left and right atrial sizes were not statistically significant predictors of sinus conversion by the RF maze procedure. However, as a result of postoperative reduction of atrial sizes, postoperative left atrial diameter was significantly smaller in patients who had sinus conversion by the RF maze procedure than in patients who did not regain sinus rhythm (45.0+/-7.0 mm vs 51.0+/-8.0 mm; P = 0.03). Postoperative right atrial area of patients who had sinus conversion by the RF maze procedure also was significantly smaller than that of patients who did not regain sinus rhythm (18.1+/-4.4 cm2 vs 28.5+/-8.2 cm2; P = 0.008). CONCLUSION: Atrial size reduction appears to predict the success of sinus conversion with the RF maze procedure used in conjunction with valvular surgery.

Adult↗