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PubMed1989

[Incidence and concomitant factors of tricuspid valve insufficiency in patients with aortic and mitral valve diseases].

Invasive data about the frequency and associated factors of tricuspid regurgitation in normals and in patients with aortic and mitral valve disease are still rare. Thus, right ventricular biplane angiograms (RAO/LAO projection), the mean pulmonary artery pressure and the presence of atrial fibrillation were analyzed with regard to tricuspid regurgitation in 30 normals and 165 patients with pure mitral regurgitation, mitral stenosis, aortic regurgitation, aortic stenosis, combined mitral valve disease or combined aortic valve disease. Patients with tricuspid stenosis or coronary artery disease were excluded. In 52 of the 195 patients tricuspid regurgitation was present. Tricuspid regurgitation occurred statistically more often in patients with mitral stenosis (33%), mitral regurgitation (48%) or combined mitral valve disease (68%) than in patients with aortic regurgitation (4%) or combined aortic valve disease (3%). In patients with aortic stenosis and in normals tricuspid regurgitation was not present. In patients with combined mitral valve disease, tricuspid regurgitation was more often present than in patients with pure mitral stenosis (p less than 0.002), despite comparable values of the mean pulmonary artery pressure, the right ventricular enddiastolic and endsystolic volume indexes, the right ventricular ejection fraction and the frequency of atrial fibrillation. Only in patients with pure mitral regurgitation tricuspid regurgitation was associated with an elevated mean pulmonary artery pressure (p less than 0.02). Differences in the right ventricular size and function did not occur between normals and patients with mitral or aortic valve disease. Therefore, the mean pulmonary artery pressure, atrial fibrillation and the size and function of the right ventricle are not major determinants for the occurrence of tricuspid regurgitation.(ABSTRACT TRUNCATED AT 250 WORDS)

Aortic Valve↗

PubMed1996

Angiotensin II-receptor subtypes in human atria and evidence for alterations in patients with cardiac dysfunction.

Angiotensin II (AII) has been implicated as an important factor in the pathophysiology of heart diseases. Following the recent identification of two subtypes of the AII receptor in cardiac tissue of animals, we investigated the possible occurrence of these, or similar, subtypes in human atrial tissue. In right-atrial tissue from patients undergoing heart surgery, we determined the AII-receptor profile in receptor binding studies, using [125I]-angiotensin as radioligand and subtypes to identify and quantify AII-receptor subpopulations. In 35 patients (23 requiring coronary bypasses, 10 valvular surgery and two combined coronary and valvular surgery), the left-ventricular ejection fraction was determined in the preoperative phase, and right- and left-atrial pressure during surgery. In membranes of human right atria, AII receptors are present in high density (median: Bmax = 294 fmol.mg-1 protein, range: 111-2073) and two different subtypes can be distinguished. Type-1 receptors (AT1) accounted for 33 +/- 10% of the population whereas type-2 receptors (AT2) made up 67 +/- 10% of the population. There was no correlation between any of the measured cardiac functions and total AII-receptor density or receptor affinity. However, the percentage of AT1 receptors was higher in the atria of patients with normal right-atrial pressure; left-ventricular ejection fraction was positively and right-atrial pressure inversely correlated with the percentage of AT1 receptors (r = 0.740 and -0.901, respectively; P < 0.001, for both). Moreover, the percentage of AT2 receptors was directly correlated with the levels of left-atrial pressure (r = 0.853; P < 0.001). It is concluded that the ratio of AT1 to AT2 receptors correlates well with right-atrial pressure and left-ventricular function. This is a first indication of a possible involvement of AII-receptor subtypes in the pathophysiology of cardiac dysfunctions.

Adult↗

PubMed1991

[Transmitral flow velocity patterns as influenced by preload, afterload and heart rate alterations: pulsed Doppler echocardiographic study].

The influences of preload, afterload and heart rate alterations on the pattern of left ventricular filling were investigated using pulsed Doppler echocardiography (PDE) in humans. Transmitral flow at the level of the valvular tip was recorded during dextran infusion, lower body negative pressure, angiotensin II infusion, and atrial and atrioventricular sequential pacings. Peak velocity of rapid filling (R), peak velocity of atrial contraction (A), the ratio of peak velocities (A/R), flow velocity integrals of the rapid filling phase (IR) and atrial contraction (IA) were obtained. PDE and the measurement of hemodynamics during lower body negative pressure (0, -10 mmHg, -20 mmHg) and dextran infusion (100 ml, 200 ml) were studied in 22 patients with ischemic heart disease. R decreased significantly after lower body negative pressure, and increased significantly during dextran infusion. Before and during angiotensin II infusion, PDE and the measurement of hemodynamics were studied in 14 patients with ischemic heart disease. The patients were categorized into 2 subgroups according to left ventricular function. During afterload stress, the A/R and IA increased in patients with normal left ventricular function; whereas, the A/R decreased in patients with poor left ventricular function. PDE was recorded during right atrial and atrioventricular sequential pacings at the heart rates of 60 to 100 beats/min in 29 patients with ischemic heart disease. When the heart rates increased, R decreased during atrial and atrioventricular sequential pacings. The A increased after the occurrence of the summation between the rapid and atrial filling waves. The A/R gradually increased with incremental heart rate. These results indicate that changes in the preload alter the peak velocity of left ventricular filling pattern of transmitral flow. The effects of the increasing afterload depend on the basal left ventricular function, with an increase in the peak velocity of atrial contraction being observed in the presence of normal left ventricular function. Both the peak velocity of rapid filling and atrial contraction were related to the heart rate and atrioventricular conduction delay. In assessing left ventricular filling dynamics using PDE, the influence of the preload, afterload and heart rate must be considered.

Angiotensin II↗

PubMed1996

Resting hemodynamics after total versus standard orthotopic heart transplantation.

Total orthotopic heart transplantation (TOHT) requires longer surgery than standard orthotopic heart transplantation (SOHT), but offers normal anatomy and synchronous atrial contraction. We endeavored to test whether TOHT improves resting hemodynamics. We analyzed 60 patients with SOHT and 66 with TOHT transplanted between 12/89 and 7/94. Age, preoperative NYHA class, ejection fraction, and donor characteristics were similar. After applying exclusion criteria at 2 weeks postoperatively, 53 SOHT and 58 TOHT patients were accepted for further study. Right-heart hemodynamics were examined at 2 weeks and 6 months posttransplant. Despite a longer ischemic time (161 +/- 36 vs. 142 +/- 37 min, p = 0.004), cardiac output and index were higher in the TOHT group at 2 weeks (6.1 +/- 1.4 vs. 5.4 +/- 1.0 L/min, TOHT vs. SOHT, p = 0.01; and 3.3 +/- 0.7 vs. 2.9 +/- 0.6 L/min/m2, p = 0.005) but similar at 6 months (5.9 +/- 1.2 vs. 5.6 +/- 1.4 L/min; and 3.0 +/- 0.6 vs. 2.9 +/- 0.7 L/min/m2). Right-atrial pressure was lower with TOHT at both time points (7 +/- 4 vs. 9 +/- 4 mmHg, p = 0.02: and 5 +/- 2 vs. 7 +/- 3, p = 0.0006). Wedge pressure was similar at 2 weeks (12 +/- 5 vs. 13 +/- 5, p = 0.045). Heart rate (bpm) was higher at both time points with TOHT (84 +/- 10 vs. 75 +/- 12, p = 0.0003: and 90 +/- 12 vs. 82 +/- 9, p = 0.0006). Pulmonary vascular resistance was similar at both time points. Despite a longer ischemic time, total orthotopic heart transplantation does not impair postoperative cardiac function. There is an early improvement in cardiac output, a sustained higher heart rate reflecting preservation of donor sinus node function, and a lower right-atrial pressure.

Blood Pressure↗

PubMed1992

Effects of volume expansion on renal sympathetic nerve activity and cardiovascular and renal function in lambs.

To assess the cardiopulmonary baroreflex in the immature animal, effects of volume expansion on changes in right atrial pressure, renal sympathetic nerve activity, and renal function were measured in chronically instrumented newborn (4-8 days; n = 13) and older lambs (4-5 wk; n = 14). Studies were carried out for 30 min before and 2 h after volume expansion with 6% Dextran 70 (25 ml/kg). Right atrial pressure increased by 4.0 +/- 0.5 mmHg in newborns and by 8.8 +/- 0.6 mmHg in older lambs within 15 min of volume expansion (P less than 0.001). After volume expansion, heart rate decreased in newborns from 237 +/- 6 beats/min to a nadir of 211 +/- 7 beats/min 2 h later (P less than 0.001) but remained constant at control levels of 148 +/- 9 beats/min in older lambs. Maximal inhibition of renal sympathetic nerve activity was achieved at 15 min in older lambs (-50.1 +/- 7.5%) and at 60 min (-58.3 +/- 10.9%) in newborns in which there was a prolonged sympathoinhibition (P less than 0.001). There was also a significant diuretic response in both groups but a limited natriuretic response to volume expansion in newborns (P greater than 0.05) compared with older lambs (P less than 0.001). These data demonstrate the presence of the cardiopulmonary baroreflex in the first week of life in lambs. The sustained sympathoinhibition and bradycardia seen in response to volume expansion in newborns but not in older lambs support the hypothesis that the reflexes controlling arterial pressure and blood volume change with postnatal maturation.

Animals↗

PubMed2000

Double-chambered right ventricle presenting in adulthood.

BACKGROUND: Double-chambered right ventricle is a form of right ventricular outflow tract obstruction that develops over time, often in patients with an abnormally short distance between the moderator band and pulmonary valve. This lesion typically presents in childhood or adolescence and is often accompanied by a ventricular septal defect. Only a handful of previous cases have been described in which double-chambered right ventricle occurred in adulthood. METHODS: Since 1992, three patients more than 30 years old (38, 43, and 66 years of age) have presented at our institution with unusual symptoms or a previous incorrect diagnosis. We reviewed the clinical data in these patients. RESULTS: Presenting symptoms included syncope, angina, and severe dyspnea resembling pulmonary hypertension. In 1 patient, disease was categorized as New York Heart Association class IV, and in the other 2 as class III. Coexisting anomalies included a patent foramen ovale or secundum atrial septal defect in 2 patients, a small ventricular septal defect in 1 (with a probable history of ventricular septal defect in another), and mild aortic regurgitation in 1. All patients required urgent or emergent operations, with peak pressures in the proximal right ventricular chamber of 135 to 180 mm Hg and severely depressed left ventricular function in 1 patient. Resection of the anomalous right ventricular muscle bundles was achieved through a right atrial approach in all patients. All patients were alive with improved functional status at follow-up, which was between 15 and 40 months. CONCLUSIONS: Right ventricular outflow tract obstruction resulting from a double-chambered right ventricle is rare in adults, but when it does occur it can present with unusual symptoms. When evaluating the patient with signs or symptoms of primary right heart failure, cardiologists should make an effort to image the entire right heart complex. Subcostal echocardiography can facilitate adequate visualization of the right ventricle when it is difficult to distinguish the subpulmonary outflow tract from the parasternal and apical windows.

Adult↗

PubMed1997

[Area reduction effects on atrial fibrillation inducibility].

Atrial fibrillation inducibility and sustenance depend upon the atrial electrophysiologies such as wavelength and upon the anatomical factors such as atrial area. To determine the mechanism of prevention of atrial fibrillation by atrial mass reduction, 20 adult mongrel dogs underwent the right atrial isolation procedure and atrial fibrillation duration, functional refractory period, conduction velocity, wavelength, atrial area and weight were examined pre- and postoperatively. The animals were divided into two groups: right atrial isolation group (RAI-group, n = 10) and control group (C-group, n = 10) in which cardiopulmonary bypass was undergone for the identical duration and the right atrial isolation was not performed. Atrial fibrillation duration significantly prolonged from 9.2 +/- 2.5 sec preoperatively to 43.6 +/- 0.4 sec postoperatively in the control group. However, in the RAI group, the duration significantly shortened from 11.4 +/- 2.7 preoperatively to 1.2 +/- 10 sec postoperatively. The wavelength at the non-isolated atrium did not show significant difference between the control group and the RAI group. The atrial area decreased from 61.9 +/- 4.1 cm2 to 46.3 +/- 3.5 cm2 postoperatively in the RAI group, while the area did not change in the control group. We conclude that the reduction in the effective atrial area affects the inducibility of atrial fibrillation.

Animals↗

PubMed2002

Deterioration of left ventricular function following atrio-ventricular node ablation and right ventricular apical pacing in patients with permanent atrial fibrillation.

AIMS: Transcatheter radiofrequency ablation of the atrio-ventricular (AV) node followed by ventricular pacing has been shown to improve symptoms and quality of life of patients with atrial fibrillation (AF). It is assumed that function improves, but this has been less well demonstrated. The aim of this study was to assess the long-term effect of AV node ablation and ventricular pacing on left ventricular ejection fraction (LVEF) in patients with permanent AF. METHODS AND RESULTS: All 12 patients studied had permanent AF for at least 12 months (mean age 70 years, range 41 to 78). LVEF was determined 6 days and 3 months after AV node ablation by radionuclide ventriculography, at a paced rate of 80 beats . min (-1). Cardiac dimensions were measured by means of transthoracic echocardiography. No major changes in pharmacological therapy were made during 3 months follow-up period. LVEF showed a significant deterioration after 3 months follow-up period for the group (47.5 +/- 14.4%; 6 days after ablation vs 43.2 +/- 13.7%; 3 months after ablation, P < 0.05). There were no significant differences in left ventricular cavity dimensions directly after AV node ablation and 3 months later (LVEDD 51.2 +/- 10.7 mm vs 52.6 +/- 8.6 mm, P = NS: LVESD: 36.1 +/- 14.2 mm vs 36.6 +/- 9.7 mm, P = NS). Left atrial size did not show reduction 3 months after AV node ablation (50.8 +/- 13.6 mm vs 51.0 +/- 14.1 mm, P = NS). CONCLUSION: The restoration of a regular ventricular rhythm following AV node ablation for patients in permanent AF does not result in improvement in left ventricular function.

Adult↗

PubMed1988

Atrial electrophysiologic properties of patients with asymptomatic Wolff-Parkinson-White syndrome.

To evaluate the existence of a peculiar atrial electrophysiologic substrate, we studied 18 patients with asymptomatic Wolff-Parkinson-White (WPW) syndrome. These patients were compared with 10 age-matched normal subjects (N). Effective and functional refractory periods were determined at two right atrial sites (high and low in the lateral wall), during atrial pacing (100 min-1) and at twice diastolic threshold. Disperson (D) of effective (ERP) and functional (FRP) refractoriness was evaluated as the difference between refractory periods at the two atrial sites. WPW patients showed significantly lower mean values of effective and functional refractoriness at both atrial sites and significantly higher mean values of D-ERP and D-FRP. Moreover, in calculating the highest normal values of D-ERP and D-FRP (as mean values of N plus 2SD) it was observed that WPW with abnormal values of D showed a statistically (chi 2 test) higher incidence (100%) of induced atrial fibrillation (AF). These findings indicate the existence of both an abnormal atrial electrophysiologic substrate and of a higher vulnerability in WPW. Finally, AF was induced generally at the site with the lower refractoriness (i.e. low lateral site). This should be taken into account when considering how atrial fibrillation can be induced more easily.

Adolescent↗

PubMed1990

[A case report of Ebstein's anomaly treated with Carpentier's procedure].

A 42-year-old male patient was admitted with congestive heart failure. Echocardiogram and cardiac angiogram revealed Ebstein's anomaly and severe tricuspid valve incompetence. He underwent Carpentier's procedure for the treatment of Ebstein's anomaly. Carpentier's procedure consists of the following two new points; (1) the right atrium and atrialized ventricle is plicated longitudinally; (2) the anterior leaflet and the posterior leaflet of tricuspid valve are transposed with a clockwise rotation to the level of the normal tricuspid anulus. Compared with Hardy's procedure (transverse plication), longitudinal plication preserves the cavity and the function of the right ventricle and excludes atrialized chamber. In our case, there is a trivial residual regurgitation of tricuspid valve postoperatively, but the patient's clinical status has improved remarkably. We conclude that Carpentier's procedure is an effective operation for Ebstein's anomaly.

Adult↗

PubMed1986

Response to isoproterenol infusion in pediatric patients following atrial repair of transposition of the great arteries.

The postoperative function of the right (systemic) ventricle (SV) was evaluated in eight pediatric patients who had undergone intra-atrial switching for simple transposition of the great arteries (TGA). SV function was evaluated at rest and during isoproterenol (ISP) infusion and compared with left ventricular function in the control group. The control group consisted of five patients including two with postoperative pulmonary stenosis, two with mild pulmonary stenosis and one with postoperative partial anomalous pulmonary venous drainage. SV-graphy was performed at rest. During ISP infusion, the TGA group showed a significant increase in cardiac index (3.50 +/- 0.68 (mean +/- SD) L/min/m2 to 4.94 +/- 1.53 L/min/m2, p less than 0.05) and no significant changes in stroke volume index (SVI). Similar changes were observed in the control group. Resting SV ejection fraction was 0.37 +/- 0.05 in the TGA group. In regard to the relationship between SV end-diastolic pressure and SVI, all but one of the TGA patients showed normal response to the stress. These results indicated that the right ventricle in TGA showed an acceptable response to ISP stress and acted as a systemic ventricle for at least two years after surgery.

Child, Preschool↗

PubMed2005

Improvements in cardiac form and function after transcatheter closure of secundum atrial septal defects.

OBJECTIVES: We set out to study the effect of transcatheter closure of atrial septal defect (ASD) on right ventricular (RV) and left ventricular (LV) function assessed by myocardial performance index (MPI), as well as left atrial (LA) volumes. BACKGROUND: The hemodynamic response to the closure of ASD is well-documented in surgically treated patients. However, few studies have documented echocardiographic evaluation of ventricular function in patients undergoing transcatheter closure of ASDs. METHODS: Pre- and post-ASD device closure echocardiograms of 25 consecutive patients were retrospectively reviewed. Measurements of RV and LV MPI and LA volumes were made. RESULTS: Twenty-five patients with an average age of 45.5 +/- 16.3 years underwent transcatheter closure of ASD. There was statistically significant improvement in RV MPI (0.35 to 0.28, p = 0.004), LV MPI (0.37 to 0.31, p = 0.04), and LA volume index (25.7 to 21.8 ml/m(2), p < 0.001) after closure of ASD. CONCLUSIONS: Device closure of ASDs leads to improvement of both RV and LV function as well as reduction in LA volume. These hemodynamic improvements provide insights into the symptomatic benefits gained in closure of ASDs using the transcatheter approach.

Adult↗

PubMed2004

The anatomic variability of the coronary vasculature of the human heart--part I: functional vascular zones--a morphological view.

The myocardium may be divided into distinct zones which act as functional units of the coronary vascular network. The basic principle of this functional systematization of cardiac blood vessels is a constant relationship between the "distributing" and the "delivering" vessels. Six arterial zones of the myocardium are identified under this scheme: anterior right ventricular, lateral left ventricular, posterior left ventricular, interventricular septal, posterior right ventricular, and atrial. The distributing vessels of functional myocardial zones are most frequently both arterial and venous. However, between the lateral and posterior left ventricular zones there is sometimes only the left marginal vein (24%) or left marginal artery (20%). Between the atrial and posterior right ventricular zones there is sometimes only the right coronary artery (52%), or only the small cardiac vein (14%) as a distributing vessel. Between the left and the right posterior ventricular zones there is sometimes an arterial and sometimes a venous distributing vessel (10%). Between the posterior and anterior right ventricular zones there is either the artery (21%) or the right marginal vein (8%) as a distributing vessel. The permanence of the six functional myocardial zones is determined not only by the arterial but also by the venous distributing vessels, and in some cases the venous vessels are the only distributing vessels between certain zones.

Adolescent↗

PubMed1993

Evaluation of left and right ventricular function by transesophageal echocardiography.

Transesophageal echocardiography, especially in the emerging generation of biplane and multiplane probes with the availability of continuous wave Doppler, has increased our capability for evaluating intracardiac hemodynamics and ventricular function. Transesophageal studies have expanded their role both in clinical research and routine monitoring. The available hemodynamic data (assessment of left and right ventricular function, estimation of left atrial and pulmonary artery pressures, evaluation of the hypotensive patient) apply not only to patients monitored in the operating room but also to patients in the critical care and ambulatory setting. These data can be combined with the anatomic pathology to provide bedside diagnoses and often facilitate appropriate therapy. Further improvements in the quality of both images and computer software are likely to allow more detailed studies of subtle changes in cardiac function in humans.

Blood Pressure↗

PubMed2006

Current management of late failure after classic Fontan modifications: Fontan conversion.

BACKGROUND: Re-establishment of Fontan circulation by eliminating the drawbacks of classic Fontan modifications has been proposed recently to improve the functional class and quality of life of patients with failed Fontan circulation. METHODS: Five patients underwent extracardiac and lateral tunnel Fontan conversion due to failure of the Fontan circulation, after classic Fontan modifications. All of the patients were female and mean age was 10.2 +/- 2.2 years (range: 8-14 years). Previous Fontan modifications were atrio-pulmonary anastomosis in 3 and Kawashima operation in 2 patients. Time to re-operation for Fontan conversion was 6 +/- 1.5 years (range: 4-8 years). Indications for re-operation were right heart failure, right atrial dilatation, and intractable atrial arrhythmias in patients with previous atrio-pulmonary anastomosis, progressive hypoxia and exercise intolerance in patients with previous Kawashima operation due to pulmonary arteriovenous fistulas. Previous atrio-pulmonary anastomoses were converted to intra-atrial or lateral tunnel Fontan operation with modified right atrial Maze procedure. Extracardiac Fontan completion was carried out after previous Kawashima operations by redirection of hepatic veins to the lungs. RESULTS: There was no mortality and no major morbidity. All patients were discharged from the hospital in good condition and in sinus rhythm. No prolonged or recurrent effusions were observed. On follow-up, all patients were in sinus rhythm and had NYHA class I functional capacity. In two Kawashima patients, SpO(2) gradually increased from 60 % to 90 % six months after the operation. DISCUSSION: We suggest that Fontan conversion should be considered in patients with previous atrio-pulmonary anastomosis, when right atrial dilatation or intractable atrial arrhythmias with deteriorating functional status develops. Redirection of hepatic venous flow to lungs induces regression of pulmonary arteriovenous fistulas and improves arterial saturation in patients with previous Kawashima operation.

Adolescent↗

PubMed1999

Right atrial appendage thrombosis in atrial fibrillation: its frequency and its clinical predictors.

This study assesses the incidence of right atrial (RA) chamber and appendage thrombosis in patients with atrial fibrillation (AF) in relation to RA appendage morphology and function. Transthoracic and multiplane transesophageal echocardiography were performed in 102 patients with AF to assess the incidence of RA and left atrial (LA) thrombi and spontaneous echo contrast. Both right and left ventricular sizes, atrial chamber and appendage sizes and function were measured. Twenty-two patients in sinus rhythm served as the control group (SR). Complete visualization of the RA appendage was feasible in 90 patients with AF. Patients with AF had lower tricuspid annular excursion (p = 0.008) and larger RA chamber area (p = 0.0001) than patients in SR. In addition, RA appendage areas were larger (p <0.05) and RA ejection fraction and peak emptying velocities (both p <0.0001) were lower in patients with AF patients than in those in SR. Equivalent differences were found for the LA appendage. Six thrombi were found in the RA appendage and 11 thrombi in the LA appendage in AF patients. Spontaneous echo contrast was found in 57% and 66% in the right atrium and in the left atrium, respectively. AF patients with RA appendage thrombi had a larger RA area (p = 0.0001), and lower RA appendage ejection fraction and emptying velocities (both p = 0.0001) than patients without thrombi. Spontaneous echo contrast was detected in all patients with thrombi. Spontaneous echo contrast was the only independent predictor of RA (p = 0.03) and LA appendage thrombosis (p = 0.036). In conclusion, multiplane transesophageal echocardiography allows the assessment of RA appendage morphology and function. RA spontaneous echo contrast is the only independent predictor of RA appendage thrombosis.

Adult↗

PubMed1991

Mild pressure loading alters right ventricular function in fetal sheep.

Right ventricular function before and during 10 days of mild pressure loading (10 mm Hg increase in mean pulmonary arterial pressure) was compared with right ventricular function in unloaded near-term fetal sheep. Pressure loading did not alter fetal arterial blood gases or vascular pressures. The right ventricular function curve (stroke volume versus mean right atrial pressure) was not significantly altered by loading. However, the relation between right ventricular stroke volume and increased arterial pressure was dramatically shifted upward, indicating improved ventricular function after the 10-day loading period. Normalized free wall of the loaded right ventricles became thicker (1.2 +/- 0.2 versus 0.9 +/- 0.2 mm/kg, p less than 0.01) and heavier (2.7 +/- 0.4 g/kg versus 2.2 +/- 0.4 g/kg, p less than 0.05) than control, and the ratio of the equatorial radius of curvature to wall thickness decreased (3.2 +/- 0.5 versus 4.5 +/- 0.9, p less than 0.005). Left ventricular free wall and septal weights and thicknesses were not significantly changed. The in vitro diastolic pressure-volume curves of both ventricular chambers of loaded hearts shifted to the left, indicating smaller ventricles than controls at physiological filling pressures. These data suggest the transduction of right ventricular loading effects to the left ventricle. Improved right ventricular function after loading is predicted by the law of Laplace based on the decreased radius of curvature-to-wall thickness ratio.

Animals↗

PubMed1999

Influence of frusemide on dynamic cardiac variables during exercise.

Exercising horses have extremely high right and left atrial pressures. Limitation in ventricular function (i.e. relaxation) may play a role in these high pressures. We studied relaxation characteristics of the right ventricular myocardium and the impact of frusemide (2.0 mg/kg bwt i.v.) on these characteristics in horses exercising at 8, 10, 12 and 14 m/s. Exercise tests were performed 4 h after administration of frusemide. Right ventricular (RV) pressure was analysed using Fast Fourier Transform techniques to remove non cardiac components of the pressure signal. Mean right atrial (RA) pressure increased with exercise and was significantly attenuated at all speeds by frusemide. RV maximum and minimum rates of pressure change with respect to time (RV + dP/dtmax, RV-dP/dtmax) increased with exercise and RV relaxation time constant (RV tau) and time of RV relaxation from 65-20% of the difference between maximum and minimum ventricular pressure (delta 65-20) decreased with exercise. Frusemide produced no significant differences in +dP/dtmax, -dP/dtmax, RV tau or delta 65-20 except at 12 m/s where RV tau was longer after frusemide (23.4 ms for frusemide vs. 19.7 ms for control). Significant reductions in stroke volume were seen at 8, 10 and 14 m/s after frusemide. These results suggest that the reduction of atrial pressure by frusemide is not due to changes in ventricular relaxation rate.

Animals↗