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Results for “atrial function”

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At least 1,333 records · Page 74Linked to original sources
PubMed1991

Multiplexing studies of effects of rapid atrial pacing on the area of slow conduction during atrial flutter in canine pericarditis model.

BACKGROUND: We report that rapid atrial pacing interrupts atrial flutter when the orthodromic wave front from the pacing impulse is blocked in an area of slow conduction in the reentry circuit. To characterize the area of slow conduction during atrial flutter and rapid pacing, we studied 11 episodes of induced atrial flutter, mean cycle length 157 +/- 20 msec, in eight dogs with sterile pericarditis. METHODS AND RESULTS: Atrial electrograms were recorded simultaneously from 95 pairs of right atrial electrodes during the interruption of atrial flutter by rapid atrial pacing, mean cycle length 139 +/- 21 msec. Areas of slow conduction during atrial flutter were demonstrated at one to three sites in the reentry circuit. After rapid pacing captured the reentry circuit, one area of slow conduction either disappeared (10 episodes) or the degree of slow conduction in an area of slow conduction decreased (one episode). Both changes were in association with activation of the region by a wave front from the pacing impulse that arrived from a direction different than that during the induced atrial flutter. Interruption of atrial flutter during rapid pacing occurred when the orthodromic wave front from the pacing impulse blocked in an area of slow conduction that had either newly evolved during rapid pacing (seven episodes) or that was previously present (four episodes). CONCLUSIONS: Areas of slow conduction present during atrial flutter and rapid pacing of atrial flutter are functional and depend on both the atrial rate and the direction of the circulating wave fronts. Interruption of atrial flutter by rapid pacing results from block of the orthodromic wave front of the pacing impulse in an area of slow conduction in the reentry circuit.

Animals↗
PubMed2004

Preoperative atrial size predicts the success of radiofrequency maze procedure for permanent atrial fibrillation in patients undergoing concomitant valvular surgery.

BACKGROUND: The radiofrequency (RF) maze procedure can effectively restore sinus rhythm and atrial transport function in the majority of patients with permanent atrial fibrillation (AF) and mitral valve disease. No previous study has described a cutoff value of preoperative atrial size determined by the discriminant analysis in predicting the success of sinus conversion by the RF maze procedure for permanent AF in patients with mitral valve disease. METHODS AND RESULTS: This study included 81 patients with permanent AF and mitral valve disease who underwent the RF maze IV procedure while undergoing concomitant valvular operations. There was one surgical death (1.2%). Another patient died of acute necrotizing pancreatitis 13 months later. Two patients (2.5%) developed sick sinus syndrome and received transvenous permanent pacemaker implantation. In the remaining 77 patients, there were 38 men and 39 women, with a mean (+/- SD) age of 51 +/- 11 years. At a mean follow-up time of 38 months, 65 patients (84.4%) had persistent sinus conversion that had been accomplished by the RF maze procedure (group 1), and 12 patients (15.6%) did not regain sinus rhythm (group 2). We evaluated the preoperative variables between the two groups. Univariate analysis demonstrated that the preoperative left atrial area and the left atrial diameter of group 1 patients were significantly smaller than those of group 2 patients. Group 1 had significantly fewer patients associated with tricuspid valve disease than did group 2. By multiple stepwise logistic regression analysis, only the preoperative left atrial area was an independent determinant of sinus conversion by the RF maze procedure (odds ratio, 0.961; 95% confidence interval, 0.935 to 0.988; p < 0.005). Linear discriminant analysis demonstrated that the sensitivity and specificity of the cutoff value of 56.25 cm(2) of the preoperative left atrial area in predicting the sinus conversion by the RF maze procedure were 50.0% and 86.2%, respectively, and the positive and negative predictive values were 40.0% and 90.3%, respectively. CONCLUSION: The preoperative left atrial area is an independent determinant of sinus conversion by the RF maze procedure for patients with permanent AF and mitral valve disease.

Adult↗
PubMed1986

Aging and vasodilation to atrial peptides.

Alterations in the levels or activity of atrial peptides may be associated with cardiovascular pathologies such as hypertension and congestive heart failure that are more common in the elderly. In the present study, we examined the possibility that vascular relaxation to atrial peptides may be affected by animal age. In vitro evaluation of the relaxation produced by atrial peptide-25 (AP-25) in serotonin-contracted rat aorta, carotid artery and mesenteric artery indicated that relaxation was greatest in tissues from rats 1-2 months of age. Nevertheless, roughly 80% of the maximal possible relaxation to AP-25 occurred in arteries from older rats (up to 18-19 months of age). A similar profile of relaxant responsiveness occurred with AP-21 (atriopeptin I). Unlike the arterial preparations examined, portal veins from rats of all ages relaxed similarly to AP-25, consistent with the lack of age-related changes in relaxation to beta-agonists in the rat portal vein. In vivo, AP-25 given intravenously lowered blood pressure to a similar extent in rats of all ages. Thus, the greater in vitro sensitivity of arteries from rats 1-2 months of age did not result in a greater reduction in blood pressure in these young rats. This latter observation is consistent with the possibility that the effect of atrial peptides on blood pressure may not be associated with an arterial event, but rather with an alteration in venous return and/or cardiac output as previously proposed. Since arteries from older rats were able to respond to atrial peptides, our studies add further support to the impetus to develop clinical agents that might either enhance atrial peptide levels or mimic the action of atrial peptides since no major decline in receptor function of atrial peptides occurred with advanced age.

Aging↗
PubMed1992

[Doppler echocardiographic assessment of left atrial and left ventricular function during right bundle branch block].

Electrocardiographic, echocardiographic and Doppler echocardiographic studies were performed in 44 patients with coronary heart disease and complete right bundle branch block. The patients were found to have an impaired phase pattern of left ventricular systole and diastole as more prolonged length of its isometric relaxation and contraction, lower economic feasibility and efficiency of its contraction, moderate dilation and hypertrophy. Hemodynamic abnormalities in the left heart in these patients are closely correlate with the changes in the phase pattern of right ventricular systole and they turn out to be so greater as the degree of its hypertrophy is. In complete right bundle branch block, left ventricular pump dysfunction leads to decreased cardiac output and cardiac index, increased total peripheral vascular resistance, thus predisposing to impaired greater circulation.

Adult↗
PubMed1992

[Clinical and functional correlations of left atrial excursion characteristics in patients with mitral valve diseases. Part II].

Left atrial myocardial excursions were intraoperatively recorded in patients with mitral valvular disease (33 patients with mitral stenosis and 17 with mitral regurgitations). Three types of atrial myocardial excursions were identified. There was a high correlation between the types of myocardial excursions and the incidence of heart failure. The patients with Types I and II myocardial excursions had no virtually heart failure, those with Type III showed the highest (70%) incidence of heart failure. It is concluded that intraoperative assessment of left atrial myocardial excursions is of great significance in patients with mitral valvular disease.

Adolescent↗
PubMed1989

[Histo-functional interrelations of the atrial hemomicrocirculatory bed in ontogenesis].

In 110 hearts of corpses of fetuses beginning from 7 months of age and those of persons up to the age of 86 years, using various histological techniques, as well as in 20 canine hearts, using certain histochemical techniques, interrelations of the hemomicrocirculatory bed, myocardiocytes, elements of the connective tissue have been studied. Application of correlative and analysis of variance makes it possible to reveal direction and significance of the connections between the structural components of the atrial walls, as well as influence of age on the parameters investigated. The interrelations and interconnections between separate components of the atrial structural organization are complex, they change in the process of individual development, reflect development of the atrial wall and the heart as a whole.

Adolescent↗
PubMed1985

Responses to the beta 2-selective agonist procaterol of vascular and atrial preparations with different functional beta-adrenoceptor populations.

Relaxant responses to the beta-adrenoceptor agonist, procaterol, have been examined on preparations of guinea-pig pulmonary artery (beta 2-adrenoceptors only), rat and rabbit pulmonary artery and rat aorta (beta 2 greater than beta 1), and these responses have been compared with responses of dog left circumflex coronary artery (beta 1 only). Low concentrations of procaterol (3 nM to 100 nM) relaxed KC1-contracted preparations of rat aorta and pulmonary artery from rat, rabbit and guinea-pig whereas high concentrations (greater than 1 microM) were required to relax preparations of the dog left circumflex coronary artery. The dissociation constant (KP value) for procaterol on beta 1-adrenoceptors was 4.9 microM (determined on dog coronary artery) and on beta 2-adrenoceptors was 0.008 microM (rabbit pulmonary artery). Procaterol therefore had a beta 2:beta 1 selectivity value of 612. KP values obtained on guinea-pig atria for procaterol, on which the concentration-response curve was biphasic, confirmed that both beta 2- and beta 1-adrenoceptors mediate responses of this tissue. The KP values were 0.009 microM (data from the first phase of the control concentration-response curve) and 3.5 microM (data from the concentration-response curve in the presence of the beta 2-selective antagonist, ICI 118,551, 10 nM). Data obtained on rat atria indicated that chronotropic responses of preparations from some rats, but not others, involved a minor population of beta 2-adrenoceptors, but the beta 2-adrenoceptors, when present, were less important than in guinea-pig atria. 6 Procaterol appears to be a particularly useful drug for detecting a functional population of beta 2-adrenoceptors in tissues, whether they are the minor or the predominant receptor sub-type present.

Adrenergic beta-Agonists↗
PubMed1987

Left ventricular function in adults with atrial septal defect.

Sixteen patients with secundum atrial defect were catheterized giving emphasis to the analysis of the left ventricle at end systole and mid-ejection. The mean ejection fraction of the group was subnormal 57 + 8% when compared with 30 normal patients (71 + 109) P less than .005. Eight patients showed elevated end-diastolic volumes (156 + 10cc) when compared to our normal group (95% + 10cc) P less than .005. A total of 32 hypokinetic and 35 tardokinetic areas were found. Eight patients were restudied after nitroglycerin (0.4 mg sublingually) with an improvement in the ejection fraction from 54% to 70% (P less than .005) and normalization of most of the hypokinetic areas. No correlation was found between total ejection fraction or total systolic wall motion and the shunt size. Probably these left ventricular wall motion abnormalities are primary and not due to the shunt size.

Adolescent↗
PubMed1982

Echocardiographic assessment of mitral valve motion, cardiac structures, and ventricular function in dogs with atrial fibrillation.

Eleven dogs with atrial fibrillation were examined echocardiographically. During atrial fibrillation, there was no evidence of atrial contraction in the left ventricle or aorta, or on the mitral valve leaflets. Measurement of cardiac structures in echocardiograms showed decreased sizes for the aorta (P less than 0.01), interventricular septum (P less than 0.01), and posterior left ventricular wall (P less than 0.02). Evidence of decreased contractility of the left ventricle was noticed with the decreased amplitude of motion of the posterior left ventricular wall (P less than 0.001) and decreased fractional shortening (P less than 0.01). Not every QRS resulted in systolic or diastolic motion in the mitral and aortic valve leaflets, thus helping to account for the pulse deficits normally seen during atrial fibrillation.

Animals↗