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PubMed2006

Decompression of the left atrium during extracorporeal membrane oxygenation using a transseptal cannula incorporated into the circuit.

OBJECTIVES: When extracorporeal membrane oxygenation (ECMO) is used in the setting of severe myocardial dysfunction, left ventricular end-diastolic and left atrial pressure can rise to extremely high levels. Decompression of the left atrium in this setting is essential for resolution of pulmonary edema and recovery of left ventricular function. We sought to evaluate whether adequate left atrial decompression can be achieved via percutaneous placement of a transseptal left atrial drain incorporated in the ECMO venous circuit. DESIGN: Retrospective case series. SETTING: Tertiary care center pediatric intensive care unit and cardiac catheterization laboratory. PATIENTS: Seven patients (age 8 months to 28 yrs) with cardiac failure on venoarterial ECMO with left atrial hypertension. INTERVENTIONS: All patients underwent left atrial decompression with transseptal puncture and placement of a drain (8- to 15-Fr) incorporated into the ECMO venous circuit. Catheterization and ECMO records and echocardiograms were reviewed, as were the clinical course and outcome for each patient. MEASUREMENTS AND MAIN RESULTS: The median time from ECMO cannulation to left atrial decompression was 11 hrs. Average initial left atrial pressure was 31 mm Hg. Successful drain placement was achieved in seven patients with no major procedural complications. Echocardiographic improvement in left atrial dilation was achieved in five patients (71%). Inability to decompress the left atrium was fatal in two patients. Four patients were decannulated (57%), and three survived to hospital discharge (43%). Larger sheath size and higher flow rate correlated with a greater likelihood of success. CONCLUSIONS: Adequate decompression of the left atrium can be achieved by transseptal placement of a left atrial drain incorporated into the ECMO circuit. This technique represents a reasonable alternative to blade or balloon atrial septostomy for patients requiring left atrial decompression.

Adolescent↗
PubMed1999

Minimally invasive mechanical cardiac support without extracorporeal membrane oxygenation in children awaiting heart transplantation.

BACKGROUND: Mechanical cardiac assist for small children (< 30 kg) requiring bridge strategy to orthotopic heart transplantation often requires sternotomy for cannulation access to ensure perfusion to the aortic arch. Extracorporeal membrane oxygenation (ECMO) through neck cannulation is an option in very small (< 10 kg) patients, but the risk of stroke is increased in larger children. Another disadvantage is poor decompression of the left atrium, which can cause persistent pulmonary edema. METHODS: Two cases are used to illustrate two methods of avoiding sternotomy during mechanical assist in children with dilated cardiomyopathy. One of these approaches avoids the need for extracorporeal oxygenation. RESULTS: Decompression of the left-sided chambers with a left atrial cannula decreased pulmonary edema and improved pulmonary function. CONCLUSIONS: Pediatric patients with dilated cardiomyopathy may benefit from a left ventricular assist technique using a centrifugal pump, which avoids the neck vessels and sternotomy, as well as ECMO.

Cardiomyopathy, Dilated↗
PubMed2006

Role of the simultaneous sequential strategy for failed acute sinus restoration after modified left maze procedure for persistent atrial fibrillation with concomitant mitral surgery.

BACKGROUND: We assessed whether the simultaneous sequential strategy could (1) achieve additional sinus restoration for those patients who were not in sinus rhythm while coming off bypass after modified left maze procedure and (2) attain the same long-term success rates as the bi-atrial maze procedure in patients with persistent atrial fibrillation (AF) and mitral valve disease. MATERIALS AND METHODS: Twenty-seven consecutive patients - ten men and 17 women with a mean age of 52 +/- 13 years, all with persistent AF and mitral valve disease - underwent the modified maze procedure with the simultaneous sequential strategy. In the first phase, the modified left atrial maze operation was carried out with concomitant valvular surgery; the right side maze operation was subsequently carried out as a second phase of the sequential strategy only if AF re-appeared following the spontaneous restoration of heart beats during the operation. RESULTS: Twenty patients (74.1%) underwent the left atrial maze procedure only, and seven patients (25.9%) required the subsequent right atrial maze procedure as part of the sequential strategy. At a mean follow-up of 15.1 +/- 7.7 months, six of the 27 patients (22.2%) who underwent additional right atrial maze procedure had restored sinus rhythm. At a mean follow-up of 17.8 +/- 7.3 months, 24 of the 27 patients (88.9%) had restored sinus rhythm and 22 patients (81.5%) had restored bi-atrial transport function (right atrial filling fraction: 40.8 +/- 11.7%; left atrial filling fraction: 22.9 +/- 8.1%) after application of the sequential strategy. CONCLUSIONS: Compared with modified left atrial maze procedure, the application of the simultaneous sequential strategy successfully restored sinus rhythm in an additional 22.2% of patients with persistent AF. The overall sinus conversion rate of 88.9% was comparable with that of the standard bi-atrial maze procedure.

Adult↗
PubMed2004

An abnormal systemic and regional hypercoagulable state in patients with mitral stenosis.

Mitral stenosis still remains a major problem in Southeast Asia including Thailand. It contributes to the morbidity and mortality related to thromboembolism which was associated with the left atrial thrombus. However, the pathogenesis of left atrial thrombus in these patients is not completely understood. Therefore, the objective of this study was to investigate the coagulation and platelet activity including the function of the endocardium in the left atrium and peripheral circulation in patients with mitral stenosis who were free of left atrial thrombus and to compare those hematologic markers activity in the peripheral venous blood between the patients with mitral stenosis and the control. Thirty-six patients with moderate to severe mitral stenosis were included in the study. Most of the patients were in functional class II and 50 per cent had atrial fibrillation. Blood was obtained from the femoral vein, femoral artery, pulmonary artery and left atrium of these patients before heparin was administered to determine the value of various hematologic markers. In the control group, blood for determining the hematologic markers was collected only from the antecubital vein. The results of this study demonstrated that the levels of prothrombin activation fragment 1+2 (F1+2), thrombin-antithrombin III complex (TAT) and Beta-thromboglobulin (beta-TG) in the left atrium of the patients with mitral stenosis were significantly higher than those in the femoral vein and femoral artery, whereas the level of thrombomodulin was significantly lower in the left atrium compared with the femoral artery and vein. When comparing with the control group, the levels of TAT, plasminogen activator inhibitors-1 (PAI-1) from the peripheral vein were significantly higher and the level of thrombomodulin was also significantly lower in the patients with mitral stenosis. In conclusion, the present study demonstrated an abnormal hypercoagulable state of the left atrium and systemic circulation related to the abnormalities of coagulation, platelets and the endocardium which may cause the formation of left atrial thrombus in patients with mitral stenosis.

Adult↗
PubMed1987

Myocardial and vascular structural adaptation to chronic pressure overload.

Left ventricular (LV) function and end-diastolic dimensions were determined during antegrade and retrograde perfusions, respectively. Isolated hearts from spontaneously hypertensive rats (SHRs) and renal hypertensive rats and SHRs to which either feldopine, nifedipine, alpha-methyldopa, or a combination of felodipine and metoprolol was administered were used. Maximal cardiac function [cardiac output x (aortic pressure - left atrial pressure)] was elevated in SHRs, but depressed in those with renal hypertension. The diastolic pressure-volume relationships revealed eccentric rather than concentric LV hypertrophy in the SHRs. Renal hypertension in SHRs caused concentric LV hypertrophy. Antihypertensive therapy with calcium antagonists (but not with alpha-methyldopa) caused reduction of LV wall thickness, but increased LV end-diastolic volume (EDV). In SHRs, coronary flow was reduced at any given level of aortic pressure. At low aortic pressures (and hence, limited coronary perfusion), cardiac function was attenuated in SHRs. This reduction could be reversed by administration of antihypertensive therapy. These results suggest an improvement in maximal stroke work in SHRs as a result of eccentric hypertrophy which allows increased stroke volume for a given degree of myocardial shortening. Structural coronary vascular changes, which can be reversed by antihypertensive therapy, can limit coronary perfusion--and hence, cardiac performance--at low aortic pressures in SHRs. Maintenance of maximal cardiac function in treated SHRs, despite a reduction in LV wall thickness, may be due to an increase in LV end-diastolic volume.

Animals↗
PubMed1982

Effects of left atrial stretch in cardiac-denervated and intact conscious dogs.

We monitored cardiovascular and renal function in conscious dogs with surgically denervated hearts during two experimental procedures: 1) inflation of a balloon in the left atrium and 2) intravascular volume expansion. The results obtained were compared with results from identical experiments on sham-operated control dogs. Left atrial balloon inflation in the sham-operated dogs produced an increase in left atrial pressure, heart rate, urine flow, and sodium excretion; central venous pressure decreased. These changes were absent in the cardiac-denervated dogs. Infusion of 6% dextran in isotonic saline (16% of estimated blood volume) increased the heart rate significantly in the control dogs but not in the cardiac-denervated dogs; other hemodynamic measurements were comparable in the two groups. Urine flow and sodium excretion increased significantly in both the cardiac-denervated and control dogs; the responses did not differ significantly between the two groups. These experiments demonstrate that inflation of a balloon in the left atrium of a conscious dog elicits diuretic and natriuretic responses that are dependent on intact cardiac neural pathways, presumably specifically dependent on afferent neural impulses from left atrial receptors. On the other hand, an increase in circulating blood volume induced by the intravenous infusion of an isotonic, isoncotic solution elicits diuretic and natriuretic responses in the cardiac-denervated dog that are similar to the renal responses produced in a control dog. Thus, although cardiac receptors are capable of eliciting reflex changes in both hemodynamics and renal function, it is not clear what role they play in mediating the renal responses evoked by increases in blood volume.

Animals↗
PubMed1991

Effect of intra-aortic balloon counterpulsation on right-left shunt following right ventricular infarction.

Intra-aortic balloon counterpulsations decrease the left ventricular end-diastolic pressure and, subsequently, the left atrial pressure in patients with impaired myocardial function following myocardial infarction. This paper reports a case of right ventricular infarction in a patient with patency of the oval foramen where the use of intra-aortic balloon counterpulsation led to the perpetuation of the right-to-left shunt.

Coronary Artery Bypass↗
PubMed2006

Silent cerebral infarction in patients with dilated cardiomyopathy: echocardiographic correlates.

BACKGROUND: Patients with dilated cardiomyopathy (DCM) have an increased risk of thromboembolic events. Incidence of silent cerebral infarction (SCI) has not been investigated in these patients. The aim of this study was to investigate the incidence of SCI in patients with DCM and to determine its associations with echocardiographic parameters. METHODS AND RESULTS: Seventy-two patients (mean age 62+/-12 years) with DCM underwent cranial magnetic resonance imaging in addition to transthoracic and transesophageal echocardiographic examination. A total of 56 age-matched healthy volunteers served as a control group for comparison SCI prevalence. Prevalence of SCI was significantly higher in patients with DCM (35% vs. 3.6%; p<0.001). In DCM group, patients with SCI had significantly impaired left ventricular systolic function, higher frequency of restrictive diastolic filling, moderate to severe left atrial spontaneous echo contrast (SEC), aortic SEC, and complex atherosclerosis or calcified plaques in the aorta. In logistic regression analysis, type of diastolic filling emerged as the only independent risk factor for SCI (p<0.001). When the type of diastolic filling was removed from the analysis, ejection fraction, marked left atrial SEC, complex-calcified aortic atheroma and age appeared as the other independent risk factors (p = 0.003, p = 0.009, p = 0.013 and p = 0.018, respectively). CONCLUSION: SCI is a frequent finding in DCM patients. Impaired systolic function, restrictive filling pattern, presence of moderate to severe left atrial SEC, and complex atherosclerosis in the aorta are the factors contributing to the development of SCI.

Adult↗
PubMed1989

Electrophysiologic characteristics of sudden QRS axis deviation during orthodromic tachycardia. Role of functional fascicular block in localization of accessory pathway.

We analyzed the effect of functional fascicular block (FFB) on ventriculoatrial conduction time (VACT) during orthodromic tachycardia (OT) in 32 patients with single accessory pathway (AP) of the Kent bundle type. The location of AP was left free wall (LFW-AP) in 21 patients, left posteroseptal in 6, right free wall in 2, and right anteroseptal in 3. FFB either alone or in combination with functional left or right bundle branch block (LBBB or RBBB) occurred predominantly at the onset of OT and was initiated with ventricular extrastimulus technique more often than with atrial extrastimulation. In patients with LFW-AP, isolated functional left anterior fascicular block (LAFB) produced significant prolongation in VACT (15-35 ms). A similar magnitude of VACT increase (20-35 ms) was also observed when LAFB was associated with RBBB. Although 25-45-ms prolongation in VACT occurred with functional LBBB and normal axis, an additional 20-55-ms VACT increase was seen when LAFB accompanied LBBB. Functional LAFB, alone or in combination with bundle branch block, however, did not prolong VACT in patients with other AP locations. Furthermore, left posterior fascicular block did not produce prolongation of VACT in any of the cases. It is concluded that in patients with the Wolff-Parkinson-White syndrome, evaluation of VACT during functional LAFB provides important information regarding AP localization and a clear separation of LFW-AP from all other locations.

Adolescent↗
PubMed1999

Exercise capacity in hypertrophic cardiomyopathy depends on left ventricular diastolic function.

Some studies have demonstrated that left ventricular (LV) diastolic function is the principal determinant of impaired exercise capacity in hypertrophic cardiomyopathy (HC). In this study we sought the capability of echocardiographic indexes of diastolic function in predicting exercise capacity in patients with HC. We studied 52 patients with HC while they were not on drugs;12 of them had LV tract obstruction at rest. Diastolic function was assessed by M-mode and Doppler echocardiography by measuring: (1) left atrial fractional shortening, and the slope of posterior aortic wall displacement during early atrial emptying on M-mode left atrial tracing; and (2) Doppler-derived transmitral and pulmonary venous flow velocity indexes. Exercise capacity was assessed by maximum oxygen consumption by cardiopulmonary test during cycloergometer upright exercise. Maximum oxygen consumption correlated with the left atrial fractional shortening (r = 0.63, p <0.001), the slope of posterior aortic wall displacement during early atrial emptying (r = 0.55, p <0.001), age (r = -0.50; p <0.001), pulmonary venous diastolic anterograde velocity (r = 0.41, p <0.01), and the systolic filling fraction (r = -0.43; p <0.01). By stepwise multiple linear regression analysis, left atrial fractional shortening and the pulmonary venous systolic filling fraction were the only determinants of the maximum oxygen consumption (multiple r = 0.70; p <0.001). Exercise capacity did not correlate with Doppler-derived transmitral indexes. Thus, in patients with HC, exercise capacity was determined by passive LV diastolic function, as assessed by the left atrial M-mode and Doppler-derived pulmonary venous flow velocities.

Adolescent↗
PubMed1986

Effects of atriopeptin infusion versus effects of left atrial stretch in awake dogs.

We infused synthetic atriopeptin III intravenously into 10 conscious dogs while monitoring renal function and systemic hemodynamics. The results obtained from these infusion experiments were compared with results from other experiments in which left atrial distension was performed in the same dogs. Both atriopeptin infusion and left atrial distension caused significant increases in urine flow, sodium excretion, potassium excretion, and free water reabsorption and a significant decrease in renal blood flow. On the other hand, the pattern of systemic hemodynamic responses to atriopeptin infusion were quite different from the hemodynamic responses elicited by left atrial distension. However, there was a striking concordance between the renal effects of atriopeptin and those of left atrial distension. We therefore hypothesize that the renal response to left atrial distension in the conscious dog is mediated largely by the release of natriuretic peptides from the atria.

Aldosterone↗
PubMed1997

Determinants of the pulmonary artery pressure rise in left ventricular dysfunction.

Pulmonary artery hypertension in patients with left ventricular dysfunction is related to poor outcome but the role of cardiac functional abnormalities in the genesis of pulmonary hypertension remains unknown. The aim of this prospective study was to identify the determinants of pulmonary hypertension in 102 consecutive patients with primary left ventricular dysfunction (ejection fraction < 50%). Systolic pulmonary artery pressure was measured by continuous wave Doppler. Left ventricular systolic and diastolic function, severity of functional mitral regurgitation, cardiac output, and left atrial volume were assessed using Doppler echocardiography. In patients with left ventricular dysfunction, systolic pulmonary artery pressure was increased (51 +/- 14 mmHg, range 23 to 87 mmHg). Mitral deceleration time (r = -0.61; p = 0.0001) and mitral effective regurgitant orifice (r = 0.50; p = 0.0001) were the strongest parameters related to systolic pulmonary artery pressure. Multivariate analysis identified these two variables as the strongest predictors of systolic pulmonary artery pressure in association with the mitral E/A ratio (p = 0.006) and age (p = 0.005). In conclusion, pulmonary hypertension is common and variable in patients with left ventricular dysfunction. It is closely related to diastolic dysfunction and severity of functional mitral regurgitation but not independently to the degree of left ventricular systolic dysfunction. These findings underline the importance of assessing diastolic function and quantifying mitral regurgitation in patients with left ventricular dysfunction.

Blood Pressure↗
PubMed2004

Antithrombotic therapy in native heart valve disease.

In establishing the indication for anticoagulation of patients with native heart valve disease, those with thromboembolic events and/or atrial fibrillation (AF) must be distinguished from patients with sinus rhythm. Anticoagulation should be started as a matter of principle in patients with thromboembolic events and/or AF who do not undergo valve replacement. However, a more differentiated procedure is mandatory for patients with sinus rhythm. If the left atrium is enlarged, spontaneous echo contrast is detected, and/or there is no atrial contraction and/or reduced left ventricular pump function (e.g., in patients with mitral valve stenosis), then anticoagulation with a target INR of 2.5 is indicated, even in those with sinus rhythm. Whereas rheumatic mitral valve stenosis predominates in developing countries, aortic stenosis (AS) predominates in developing countries. These AS patients mainly suffer microemboli that often determine the prognosis in patients with calcification of the mitral annulus. Anticoagulation is not recommended in calcific microemboli. If there are simultaneous atherothrombotic plaques of the aortic arch > 5 mm in size owing to an often more complex cardiovascular risk profile, then warfarin treatment is indicated. Mitral valve prolapse (MVP), patient foramen ovale and atrial septal aneurysm are potential sources of embolism that may cause stroke. On their own, these congenital lesions do not entail an indication for anticoagulation. This applies in particular to patients with MVP in whom secondary prevention of stroke can be attained with 100 mg aspirin.

Anticoagulants↗
PubMed2005

Effects of systolic atrial function on plasma renin activity and natriuretic peptide secretion after high rate atrial and ventricular pacing in dogs.

Rapid atrial rates cause electrical, structural remodeling, and neuro-humoral changes. This study compares the effects of mechanical remodeling on plasma renin activity (PRA) and atrial natriuretic peptide (ANP) secretion. Eight beagles were subjected to rapid atrial pacing (AP) at 400 beats/min for 16 days. After complete recovery of left ventricular function, they underwent rapid ventricular pacing (VP) at 240 beats/min of equal duration. Left atrial systolic maximal dimension (LAmax) and left atrial appendage (LAA) peak late emptying velocity (LAA-E) were assessed by echocardiography. Blood samples were taken from the right atrium and from the peripheral vein. LAmax after AP and VP enlarged significantly (2.16 +/- 0.21 cm vs 2.41 +/- 0.23 cm, P = 0.002). Compared with baseline, LAA-E velocities were significantly reduced (0.65 +/- 0.12 m/s vs 0.26 +/- 0.16 m/s, P = 0.001) after AP only. AP caused a significant elevation of PRA in right atrial (9.28 +/- 4.23 nmol/L per hour) and peripheral samples compared with baseline values (4.82 +/- 2.53 nmol/L per hour, P = 0.04). ANP levels increased after AP (1117.12 +/- 252.21 fmol/L) with respect to baseline values (824.37 +/- 159.08 fmol/L, P = 0.001). There was no difference in PRA and ANP levels between atrial and peripheral samples. Atrial size and impaired systolic appendage function play an important role in secretion of PRA and ANP. Both neuro-humoral pathways may be therapeutic targets in the treatment of patients with AF.

Animals↗
PubMed1993

[Post operative embolism and left atrial enlargement in the old-aged ASD (atrial septal defect) patients].

As the operation risk of ASD is little today, the unexpected postoperative complication such as embolism is a miserable concern. We experienced two cases of embolism, which were cerebral infarction, in old-aged patients after ASD correction. It has been reported that low cardiac function, atrial fibrillation and foreign body in the left atrium should be risk factors of the embolism after ASD correction. However, blood stasis in the left atrium due to its enlargement may be an essential risk factor of the embolism. Accordingly we evaluated the left atrial volume in 87 ASD patients without complicated cardiac disorder. There was a significant correlation between the age (X) and left atrial volume index (Y). (Y = 16.5 + 1.1X, r = 0.668, p < 0.001). Left atrial volume index in our two cases of cerebral infarction indicated 171.7, 190.8 ml/m2 respectively. The former case had sinus rhythm and its defect was directly closed, and the latter had atrial fibrillation and its defect was closed with teflon patch. In addition pulmonary artery pressure and cardiothoracic ratio correlated with left atrial volume index significantly. Although some investigators reported that pulmonary hypertension and cardiomegaly were the risk factors of embolism, the left atrial enlargement by aging was thought to be the main risk factor. Thus, we concluded that anticoagulant therapy was necessary for the ASD patients with marked left atrial enlargement.

Aged↗
PubMed1996

Relationship between diastolic hypertension and myocardial morphology and function in elderly males with diabetes mellitus.

The existence of a distinct diabetic cardiomyopathy, characterized by a raised left ventricular mass, has previously been suggested. However, as diabetes mellitus is associated with both left ventricular hypertrophy and hypertension a confounding effect of raised blood pressure in diabetic patients has to be considered. In the present cross-sectional study an echocardiographical examination was performed as part of a health screening survey in 582 males, aged 70 years. After the exclusion of subjects with coronary heart disease or those on regular antihypertensive treatment, 30 normotensive subjects with diabetes were compared with 10 subjects with non-insulin-dependent diabetes (NIDDM) and a diastolic blood pressure 90 mm Hg or more and 203 normotensive control subjects with normal glucose tolerance. Both groups with NIDDM showed a significantly increased left atrial diameter (4.4 +/- 0.7 vs 4.0 +/- 0.5 cm, p < 0.05) and an increased atrial component in diastole (A-wave, p < 0.01) compared to the control subjects. Left ventricular mass was, however, only marginally and not significantly elevated in the diabetic subjects when compared to the healthy control subjects (133 +/- 19 and 133 +/- 28 vs 128 +/- 25 g/m2). Only in the subjects with concomitant diabetes and a raised blood pressure was the intraventricular septum significantly enlarged (p < 0.05). Thus, in the present sample no distinct diabetic cardiomyopathy with an increased left ventricular mass, independent of the influence of hypertension could be detected. The myocardial alterations in these diabetic males were restricted to an increased left atrial size and an impaired diastolic function.

Aged↗
PubMed2004

Relation between left ventricular contractile reserve during low dose dobutamine echocardiography and plasma concentrations of natriuretic peptides.

BACKGROUND: In ischaemic cardiomyopathy, raised plasma concentrations of natriuretic peptides are associated with a poor long term prognosis, while the presence of contractile reserve is a favourable sign. OBJECTIVE: To assess the relation between plasma natriuretic peptides and contractile reserve. DESIGN: Prospective observational study. SETTING: Tertiary referral centre. PATIENTS: 66 consecutive patients undergoing low dose dobutamine stress echocardiography to evaluate contractile reserve in regions with contractile dysfunction at rest, divided into two groups: group 1, 31 patients with ischaemic cardiomyopathy (left ventricular ejection fraction < or = 40%) and heart failure symptoms; group 2, 35 patients with normal left ventricular function. MAIN OUTCOME MEASURES: Plasma atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP), measured using immunoradiometric assays. Contractile reserve was defined as an improvement in segmental wall motion score during infusion of low dose dobutamine. RESULTS: Plasma ANP and BNP concentrations were higher in group 1 than in group 2 (mean (SD): ANP, 17.8 (32.8) v 7.2 (9.7), p < 0.005; BNP, 24.4 (69.0) v 5.0 (14.3) pmol/l, respectively; p < 0.001). In group 1, the presence of contractile reserve was inversely related to ANP and BNP levels; however, patients with contractile reserve had lower ANP and BNP concentrations than patients without contractile reserve (ANP, 14.2 (9.1) v 24.2 (44.2), p < 0.05; BNP, 20.2 (25.5) v 37.5 (93.8) pmol/l, respectively; p < 0.05). CONCLUSIONS: Plasma natriuretic peptide concentrations are raised in patients with left ventricular dysfunction, but in the presence of preserved myocardial contractile reserve, relatively low levels of ANP and BNP are present.

Echocardiography, Stress↗
PubMed1978

Effect of acute blood volume expansion on cardiac output, plasma dopamine beta-hydroxylase, and renal function in rats with chronic constriction of the ascending aorta.

To examine the effect of raised left atrial pressure (AP) on the relationship of cardiac output to renal function, we constricted the ascending aorta in rats (AC) and 1-6 months later tested their response to acute volume expansion (VE) with blood (2% body weight, iv). Sham-operated (SH) rats were controls. In AC rats heart weight increased 38%, but cardiac output was 47% lower. Statistically significant differences in the initial clearance periods were (AC vs. SH): venous pressure (VP) 8 +/- 2 vs. 3+/- 1 cm H2O; inulin clearance (CIN) 0.61 +/- 0.06 vs. 0.84 +/- 0.04 ml/min; sodium excretion (UNAV) 1.2 +/- 0.2 vs. 2.1 +/- 0.3 muequiv./min. Filtration fraction, fractional UNaV, mean arterial pressure (MAP), and plasma dopamine beta-hydroxylase (DBH) were the same in both groups. After VE, cardiac output increased proportionately more in AC (69% vs. 27%); however, the absolute increases were not different. UNaV increased proportionately more in AC rats, but the absolute increase was less (5.1 vs. 7.5 muequiv./min). Multiple variable regression analysis showed that UNaV correlated with CIN, MAP, and VP, with no difference between AC and SH animals. Cardiovascular-renal relationships were indistinguishable from previous descriptions of dogs and rats with chronic vena caval constriction. Modulation of renal function by left AP was not apparent. In both groups after the peak response to VE, UNaV decreased in association with decreased cardiac output and increased sympathetic nervous activity as indicated by raised DBH levels. After VE, VP remained high in AC but not in SH animals.

Animals↗