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PubMed1987

Effects of atrial natriuretic peptide on renal function and renin release in the isolated perfused rat kidney.

The effects of synthetic atrial natriuretic peptide (ANP) on the renal hemodynamics, glomerular filtration rate (GFR), fluid and electrolyte excretion and renin release were studied in the isolated perfused rat kidney (IPK). When 10(-9) mol of ANP was administered in 75 ml of perfusate, the renal vascular resistance (RVR) was transiently decreased for 3 to 5 min, thereafter increased for 30 min and then tended to return to the control level. ANP increased the GFR (0.55 +/- 0.08 to 0.71 +/- 0.07 ml/min), urine flow (UV) (0.018 +/- 0.002 to 0.194 +/- 0.028 ml/min), absolute Na excretion (UNaV) (1.83 +/- 0.03 to 17.93 +/- 2.71 microEq/min) and absolute K excretion (UKV) (0.67 +/- 0.13 to 2.33 +/- 0.18 microEq/min). The addition of indomethacin or mefenamic acid to the perfusate before the administration of ANP exerted no influence on any of the effects of ANP. Renin release was inhibited by approximately 50% compared to the ANP-free control group. With the administration of ANP, UV and UNaV reached a peak 15-20 min after the GFR reached a peak and remained elevated after the GFR fell below the control level. These findings suggest that 10(-9) mol of ANP causes natriuresis and renin suppression in the IPK, and that the natriuresis is prostaglandin-independent and cannot be explained only by an increase in GFR.

Animals↗
PubMed1976

[Qualitative function test of ventriculo-atrial drainage using Cordis-Hakim valves].

Description of the acoustic detection of the functional performance of Cordis-Hakim valves. This can be monitored or perceived with a surface microphone, or demonstrated by means of an oscilloscope. To document the findings the image of the viewing screen can be photographed or continuously registered through interconnection of a recorder. There is also the possibility of testing with the stethoscope. The construction of the device and experimental arrangements are described.

Acoustics↗
PubMed2006

Electrical remodeling in atrial fibrillation.

Electrical remodeling refers to any change in electrical function that promotes atrial fibrillation (AF). A key advance in understanding the mechanisms of AF has been the identification of ion channels, gap junctions and regulators of intracellular Ca(2+) homeostasis as the molecular determinants of abnormal atrial electrical activity, and how these are modified in AF. This review focuses on the cellular and molecular basis of altered electrical properties of the atria in AF, with the goal of providing new insights into the potential molecular mechanisms and the identification of putative targets for antiarrhythmic therapy.

Action Potentials↗
PubMed1998

Atrial fibrillation is an independent determinant of low cognitive function: a cross-sectional study in elderly men.

BACKGROUND AND PURPOSE: Cerebrovascular disease is increasingly recognized as a cause of dementia and cognitive decline. We have previously reported an association between hypertension and diabetes and low cognitive function in the elderly. Atrial fibrillation is another main risk factor for cerebrovascular disease. The aim of this study was to investigate whether atrial fibrillation is associated with low cognitive function in elderly men with and without previous manifest stroke. METHODS: This was a cross-sectional study based on a cohort of 952 community-living men, aged 69 to 75 years, in Uppsala, Sweden. Cognitive functions were assessed by the Mini-Mental State Examination and the Trail Making Tests, and a composite z score was calculated. The relation between atrial fibrillation and cognitive z score was analyzed, with stroke and other vascular risk factors taken into account. RESULTS: All analyses were adjusted for age, education, and occupational level. Men with atrial fibrillation (n=44) had lower mean adjusted cognitive z scores (-0.26+/-0.11) than men without atrial fibrillation (+0.14+/-0.03; P=0.0003). The exclusion of stroke patients did not alter this relationship; the mean cognitive z score was -0.24+/-0.12 in the 36 men with atrial fibrillation and +0.17+/-0.03 in those without atrial fibrillation (P=0.0004), corresponding to a difference of 0.4 SDs between groups. Adjustments for 24-hour diastolic blood pressure and heart rate, diabetes, and ejection fraction did not change this relationship. Men with atrial fibrillation who were treated with digoxin (n=27) performed markedly better (-0.05+/-0.21) than those without treatment (n=9; -1.14+/-0.34; adjusted P=0.0005). Previous myocardial infarction was not associated with impaired cognitive results. CONCLUSIONS: In these community-living elderly men, we found an association between atrial fibrillation and low cognitive function independent of stroke, high blood pressure, and diabetes. Interventional studies are needed to answer the question of whether optimal treatment of atrial fibrillation may prevent or postpone cognitive decline and dementia.

Aged↗
PubMed1984

The role of the phase relation between the atrial excitatory waves in determining the functional refractory properties of the atrioventricular node.

Through programme stimulation of the two basic inputs of the atrioventricular node (AVN)--crista terminalis and interatrial septum--different spatial and temporal relations between the excitatory waves passing from the atrium into the node were modelled in intact rabbit heart preparation. The essential role of the spatial-temporal organization for the determination of the refractory properties is demonstrated. The functional refractory curves depend not only on the basic rhythm, but also on the direction of the atrial excitation front. It is shown that interaction of the input waves is possible in intact preparation as well. At optimum phase regimes combined stimulation of the two inputs leads to prolongation or shortening of the initial H1H2 interval. The qualitative characteristic of the observed effects is very varied. It is defined predominantly by the stimulation programme, but it does not depend on which of the two inputs the basic rhythm is applied. The view is expressed that in order to obtain a more accurate characterization of the AVN-conduction, it is necessary to consider the interaction of the atrial excitatory waves arriving at the posterior and anterior inputs of AVN and the reflection of this interaction on its refractory properties.

Animals↗
PubMed1988

Effect of exercise on plasma atrial natriuretic factor and cardiac function in men and women.

In order to provide an integrated view of the physiology of atrial natriuretic factor (ANF) during exercise, we studied changes of its plasma concentrations in 13 normal subjects (seven males, six females) during three graded exercise levels and two periods of recovery (5 and 30 min), concomitantly with an assessment of cardiac function and ventricular volumes by multigated radionuclide angiography. Mean ANF levels (+/- SEM) increased in all patients at the second (P less than 0.002) and third (P less than 0.002) exercise levels, and after 5-min recovery (P less than 0.01): in males from 16 +/- 7 to 30 +/- 11 pg ml-1 at the third level, in females from 27 +/- 12 to 61 +/- 33 pg ml-1. Normal values were observed after 30-min recovery. Even if mean ANF levels were all higher in females, this difference did not reach statistical significance (P = 0.06). Significant decreases of ventricular volumes, as well as increases of ejection fraction and rate pressure product, were noted during exercise and were similar in both sexes. The kinetics of plasma ANF concentrations, compared with the increase of rate pressure product, was characterized by a latency and a remanence in recovery. This remanence, also present in the changes of ventricular volumes, supports the hypothesis that other factor(s) like catecholamines might still exert their influence after the exercise stops.

Adult↗
PubMed1985

Optimal power generation by the left ventricle. A study in the anesthetized open thorax cat.

We studied the interaction of the left ventricle and the systemic arterial bed in the open thorax cat. In the steady state, the ventricle can be characterized by the pump function graph (i.e., the relationship between mean left ventricular pressure and mean outflow). From this pump function graph, the apparent source resistance of the heart is found. Apparent source resistance is defined as the ratio of the difference between maximal and actual mean left ventricular pressure, and mean outflow. The arterial system can be characterized by the ratio of mean aortic pressure and mean flow (peripheral resistance). The pressure and flow at which the heart operates is defined as the working point. We have investigated whether the ventricle in the intact cat is working optimally, i.e., that it cannot increase work output further at the end-diastolic volume, contractile state, and prevailing heart rate. This condition is considered as "matching" of ventricle and load. It could be shown that optimal power is transferred when the ratio of peripheral and apparent source resistance equals twice the ratio of mean aortic and mean left ventricular pressure (the matching principle). In four cats, we observed that mean aortic and mean left ventricular pressures are proportionally related. Mean external power (the time integral of the product of pressure and flow divided by cycle length) and steady power (the product of mean pressure and mean flow) were found to be proportional as well. These proportionalities allow for the calculation of peripheral resistance and mean external power from the pump function graph. Pump function graphs were determined in three groups: control (n = 9), atrial pacing (n = 8), and halothane (n = 5). We compared the ratio of peripheral and source resistance at the working point and at the point of optimal work output (expressed in steady ventricular power). It could be shown that, in all investigated groups, the power optimum and the working point coincide. It was concluded that circulatory control in the intact anesthetized cat keeps the ventricle at optimal work output under the conditions studied.

Animals↗
PubMed2006

Epinephrine increases mortality after brief asphyxial cardiac arrest in an in vivo rat model.

Epinephrine may be detrimental in cardiac arrest. In this laboratory study we sought to characterize the effect of epinephrine and concomitant calcium channel blockade on postresuscitation myocardial performance after brief asphyxial cardiac arrest. Anesthesized rats were disconnected from mechanical ventilation, resulting in cardiac arrest. Resuscitation was attempted after 1 min with mechanical ventilation, oxygen, chest compressions, and IV medication. In experimental series 1 and 2, animals were allocated to 10 or 30 microg/kg epinephrine or 0.9% saline. In series 3, animals received 30 microg/kg of epinephrine and were randomized to 0.1 mg/kg of verapamil or to 0.9% saline. In series 1 and 3, left ventricular function was assessed using transthoracic echocardiography. In series 2, left atrial pressure was measured. Epinephrine was associated with increased mortality (0/8 [0%] in controls, 4/12 [33.3%] in 10 microg/kg animals, and 16/22 [72.8%] in 30 microg/kg animals; P < 0.05), hypertension (P < 0.001), tachycardia (P = 0.004), early transient left atrial hypertension, and dose-related reduction in left ventricular end diastolic diameter (P < 0.05). Verapamil prevented mortality associated with large-dose epinephrine (0% versus 100%) and attenuated early diastolic dysfunction and postresuscitation hypertension (P = 0.001) without systolic dysfunction. Epinephrine appears to be harmful in the setting of brief cardiac arrest after asphyxia.

Animals↗
PubMed1981

[Functional state of the cardiovascular system in patients operated on for a secondary atrial septal defect].

The functional state of the cardiovascular system in 64 adults with a secondary atrial septal defect and in 120 patients who were operated on for this disease was studied by means of the physical exercise test on a bicycle ergometer. In the late postoperative period, the physical working capacity of patients who underwent operation before the age of 20 years was 92% with respect to that of healthy individuals. The physical working capacity of patients in whom the atrial septal defect was closed after the age of 20 was only 76% as compared to the capacity of healthy individuals. The study showed surgical management of an atrial septal defect to be highly effective. The best functional results in the late postoperative period were produced in patients who were operated on before the age of 20.

Adult↗
PubMed1996

Total atrioventricular cardiac transplantation preserves atrial systole and ventricular diastolic filling.

BACKGROUND: Total orthotopic heart transplantation was recently introduced into clinical practice as an alternative technique for orthotopic cardiac transplantation. Total cardiac transplantation uses separate bicaval and left and right pulmonary anastomoses, whereas the standard technique of cardiac transplantation uses atrioplasty. Because the anatomic differences between total and standard orthotopic heart transplantation occur at the atrial level, this study compares atrial systolic function and biventricular filling (dV/dt) between the standard and total transplantation techniques. METHODS AND RESULTS: Forty-eight mongrel canines (23 to 31 kg) were used for 12 total and 12 standard orthotopic cardiac transplantations. Right and left ventricular (RV/LV) function and AV synchrony were analyzed with micromanometry, sonomicrometry, ultrasonic flow meters, and intraoperative echocardiography. Results are expressed as mean +/- SEM (ANOVA, paired and unpaired t tests, and chi 2 test). There were no significant differences in baseline function (pretransplantation), bypass times, and cardiac ischemic times between the two groups. Posttransplantation sinus rhythm was preserved in all total (P < 0025) and in only one standard transplantation recipient (all required atrial diastole pacing). Significant decreases in RV/LV dV/dt from 113 +/- 13 and 123 +/- 14 mL/s to 69 +/- 6 and 85 +/- 10 mL/s after transplantation were measured in the standard group. No significant changes occurred in the total group after transplantation with respect to RV/LV diastolic filling. After transplantation, left atrial contractility and relaxation (-dP/dt) decreased significantly in the standard group by 43% and 70%, respectively, whereas in the total transplantation group, there were no observed changes in left atrial contractility and-dP/dt. A significant increase in the septum to RV free wall dimension in the standard group suggests altered geometry. CONCLUSIONS: Total AV transplantation is a feasible alternative to standard cardiac transplantation and conserves both normal sinus rhythm and synchronized beating of the atria and ventricles. Ischemic and bypass times are comparable in patients undergoing either method. These data suggest that RV/LV diastolic function and geometry and atrial systole are better preserved in the total AV transplantation technique.

Animals↗
PubMed2003

Reversal of atrial mechanical dysfunction after cardioversion of atrial fibrillation: implications for the mechanisms of tachycardia-mediated atrial cardiomyopathy.

BACKGROUND: Atrial mechanical "stunning" develops after cardioversion of atrial fibrillation (AF) and is implicated in the genesis of thromboembolic complications. However, the mechanisms responsible for this phenomenon are poorly understood. Whether atrial mechanical dysfunction caused by AF can be reversed by pacing at increased rates or by pharmacological agents is unknown. METHODS AND RESULTS: Twenty-six patients with AF undergoing cardioversion were dichotomized prospectively on the basis of the duration of arrhythmia as short-duration (1 to 6 months) or long-duration (> or =3 years) AF. Left atrial appendage emptying velocities (LAAEVs) and spontaneous echocardiographic contrast (LASEC) were assessed by transesophageal echocardiography during AF, after reversion to sinus rhythm, during atrial pacing at cycle lengths of 750 to 250 ms, after a postpacing pause, and with isoproterenol. In patients with short-duration AF, LAAEV decreased (42.0+/-2.7 to 18.5+/-2.0 cm/s; P<0.0001) and LASEC increased (0.9+/-0.3 to 2.2+/-0.3; P<0.01) with termination of AF; pacing increased LAAEV (48.3+/-4.1 cm/s; P<0.0001) and decreased LASEC (1.5+/-0.3; P<0.01); isoproterenol increased LAAEV (73.3+/-7.8 cm/s; P<0.0001) and decreased LASEC (0.3+/-0.2; P<0.01); and the postpacing pause increased LAAEV (68.3+/-3.8 cm/s; P<0.0001). In contrast, patients with long-duration AF demonstrated a significantly attenuated response of atrial mechanical function at each time point. With termination of AF, LAAEV decreased (19.1+/-2.6 to 8.2+/-1.0 cm/s; P=0.003) and LASEC increased (2.0+/-0.2 to 3.3+/-0.2; P<0.01); pacing increased LAAEV (18.4+/-2.7 cm/s; P<0.0001) and decreased LASEC (2.3+/-0.2; P<0.01); isoproterenol increased LAAEV (26.1+/-3.9 cm/s; P=NS to equivalent atrial rate) and decreased LASEC (1.0+/-0.3; P<0.01); and the postpacing pause increased LAAEV (27.2+/-2.4 cm/s; P=0.007). CONCLUSIONS: Atrial pacing at increased rates and isoproterenol can reverse atrial mechanical stunning associated with short-duration AF. In contrast, long-duration AF is associated with an attenuated response to these maneuvers. These findings suggest a functional contractile apparatus in the mechanically remodeled atrium caused by AF; however, with longer durations of AF, additional factors may determine atrial mechanical function.

Adrenergic beta-Agonists↗
PubMed1994

Effects of atrial natriuretic peptide on renal function after cardiac surgery and in cyclosporine-treated heart transplant recipients.

The study investigated the effects of intravenous infusion of atrial natriuretic peptide (human ANP 99-126) on renal function and central hemodynamics after coronary artery bypass grafting (CABG), and the ability of ANP to reverse the acute nephrotoxic effects of cyclosporine after heart transplantation. Ten patients with an EF > 0.5 and normal renal function were studied 2 to 4 hours after CABG surgery. Furthermore, six heart transplant recipients receiving cyclosporine for immunosuppression who developed renal dysfunction 2 to 4 days after transplantation were studied. Standard urinary clearance of 51Cr-EDTA and PAH was used to study the effects of ANP on glomerular filtration rate (GFR) and renal blood flow (RBF). Baseline measurements were first performed during two 30-minute periods. Incremental infusion rates of ANP were then administered for three consecutive 30-minute periods (25, 50, and 100 ng/kg/min), followed by two 30-minute post-ANP control periods. Marked increases in urinary flow (UF), GFR, filtration fraction (FF), and fractional urinary excretion of Na+ were observed in the CABG patients with increasing doses of ANP, while RBF was unchanged. Mean arterial pressure decreased by around 15% at the highest ANP dose. In the heart transplant recipients, baseline GFR was markedly reduced compared to pretransplantation values (-65%). UF, GFR, and RBF increased 240%, 69%, and 53%, respectively, while renal vascular resistance decreased 45% during the highest dose of ANP infused. At this ANP dose level, circulating ANP concentrations were sixfold to eightfold higher than the preinfusion control level.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1990

Effects of atrial natriuretic peptide on distal tubule function in humans.

To characterize the actions of atrial natriuretic peptide (ANP) in the human distal nephron, we studied interactions between ANP (0.02 micrograms/kg.min i.v.) and acutely administered substances acting in the distal nephron, that is, amiloride and aldosterone, in six healthy humans during maximal water diuresis. ANP increased NaCl excretion, fractional lithium excretion (FELi) and decreased diluting segment reabsorption estimated from free water clearance. Amiloride increased natriuresis, had no effect on FELi, but decreased diluting segment reabsorption. Aldosterone had the opposite effect. When infused in addition to amiloride, ANP still increased NaCl excretion, the changes in sodium handling parameters being comparable to those seen after ANP alone. Amiloride did not increase the further natriuretic response to ANP. These findings suggest that ANP increases distal sodium delivery, and decreases sodium reabsorption in distal segments by a mechanism also sensitive to amiloride. ANP abolished much of the antinatriuretic effect of aldosterone, which may also be explained by assuming a partial overlap of the target segments of ANP and aldosterone in the distal nephron. Remarkably, in neither of these experiments was the natriuresis after ANP accompanied by a kaliuresis, for which the explanation remains obscure.

Adult↗
PubMed2005

Assessment of left ventricular systolic function in patients with chronic atrial fibrillation and dilated cardiomyopathy using the ratio of preceding to prepreceding R-R intervals.

The objective of this study was to determine the relation between left ventricular (LV) systolic function and the ratio of preceding (RR1) to prepreceding (RR2) R-R intervals in patients with chronic atrial fibrillation (AF) and dilated cardiomyopathy. LV systolic function (Emax) was examined using a conductance catheter with a micromanometer in 13 patients with chronic AF and dilated cardiomyopathy. We calculated Emax as a load-independent index of LV contractility and compared it with RR1, RR2, and the ratio of RR1/RR2. We analyzed 50+/-13 cardiac cycles (range 18-61) in each patient. Average heart rate was 80+/-13 beats/min, and ejection fraction over all cardiac cycle in each patient measured by conductance catheter was 31+/-8%. Emax was positively correlated with RR1 and RR1/RR2 in all patients, and negatively correlated with RR2 in all patients. In each patient, correlation coefficients of Emax with RR1/RR2 were greater than those with either RR1 or RR2. Furthermore, Emax at RR1/RR2=1 in the linear regression line reflected average Emax over all cardiac cycles in each patient. In conclusion, we have shown that LV contractility correlated positively with RR1/RR2 in patients with chronic AF and dilated cardiomyopathy, and LV contractility at RR1/RR2=1 represents the average value of contractility over all cardiac cycles.

Adult↗
PubMed1992

[Two-stage Jatene procedure after Mustard or Senning operation].

We have successfully performed a two-stage Jatene procedure in four patients who showed severe anatomical right ventricular dysfunction after atrial switch (Mustard or Senning) operation for transposition of the great arteries. All four patients developed an adequate left ventricular pressure for the arterial switch operation by one or two-stage pulmonary artery banding. Left ventricular posterior wall thickness increased sufficiently enough after the banding although left ventricular ejection fraction showed significant decrease. After Jatene procedure left ventricular ejection fraction recovered, and RV end-diastolic volume which had been prominently enlarged preoperatively was dramatically normalized. Cardiac index increased from 3.6 +/- 1.6 l/min/m2 preoperatively to 5.3 +/- 6.1 l/min/m2 postoperatively with the decrease in left atrial pressure. Postoperative electrophysiological study revealed the recovery of sinus node function and atrial conduction by means of the take-down of atrial switch operation previously performed. We conclude that the Jatene procedure should be an ideal alternative in patients with right ventricular dysfunction after atrial switch operation. The left ventricle could be prepared by an effective pulmonary artery banding in most instances.

Cardiac Surgical Procedures↗