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PubMed1993

Prevalence and clinical significance of anomalous muscular band in the left atrium.

The significance of left ventricular false tendon and right atrial anomalous muscular band has been previously reported. As well as in the right atrium, anomalous muscular band is sometimes observed in the left atrium. To evaluate the prevalence and clinical significance of the left atrial anomalous band, a clinico-pathologic study was performed among 1,100 autopsies over 60 years. The following results were obtained: (1) Pathologically, the incidence of the left atrial anomalous band was 2% (22 cases among 1,100 autopsies). The anomalous band connected the left atrial side of fossa ovalis with the other areas of left atrial endocardium in most of the cases (19 cases). The cases with the bands had Chiari's network and patent foramen ovale at the same time more frequently than those without the bands (Chiari's network: 27% vs 8%, p < 0.01, patent foramen ovale: 23% vs 8%, p < 0.05). Microscopically, the anomalous band was composed of fibrous and muscular tissues. (2) Clinically, premature atrial complex was more frequently observed among the cases with left atrial anomalous bands than those without the bands (41% vs 11%, p < 0.01). In conclusion, left atrial anomalous band seemed to be one of congenital abnormalities which was associated with Chiari's network and patent foramen ovale in origin, and might be one of the causes of supraventricular arrhythmias.

Aged↗
PubMed2004

The association of chronic atrial fibrillation with right atrial dilatation and left ventricular dysfunction in the elderly.

BACKGROUND: Left atrial dilatation is often considered as one of the important causes for atrial fibrillation. In this study we sought to examine the relationship between right atrial dilatation and left ventricular function in patients with atrial fibrillation, and the association with the documented duration of the dysrrhythmia. MATERIAL/METHODS: 56 consecutive patients with atrial fibrillation were investigated by means of clinical history, electrocardiography and echocardiography. RESULTS: Right atrial dilatation was found in 34, left atrial dilatation in 36 and bi-atrial dilatation in 31 patients. Patients with a dilated right atrium had a larger left atrium, lower left ventricular shortening fraction, and higher transmitral flow velocity than those with a normal right atrium. A history of atrial fibrillation of over 6 months was associated with enlarged atria, reduced left ventricular shortening fraction and increased transmitral flow compared to that of 3 months or less. Functional mitral and tricuspid regurgitation were only found in patients whose atrial fibrillation was over 6 months in duration. CONCLUSIONS: Dilatation of both right and left atria is common in chronic atrial fibrillation, and is associated with impaired left ventricular function. A longer duration of atrial fibrillation predisposes to atrial dilatation, left ventricular dysfunction, and functional atrio-ventricular regurgitation. These findings suggest that atrial fibrillation may have a significant contribution to morphological and functional cardiac changes, and raise the possibilities that early cardioversion or adequate rate control might prevent these changes and may improve prognosis in the elderly.

Aged↗
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↗
PubMed1996

Nitric oxide synthase inhibition during experimental sepsis improves renal excretory function in the presence of chronically increased atrial natriuretic peptide.

OBJECTIVE: To test whether renal excretory function decreases after nitric oxide synthase inhibition during experimental hyperdynamic sepsis. DESIGN: Prospective, randomized, controlled animal trial. SETTING: Research laboratory at a large university medical center. SUBJECTS: Chronically instrumented Merino breed ewes (n = 18). INTERVENTIONS: Continuous infusion of Escherichia coli endotoxin (10 ng/kg/min) for the experimental period of 32 hrs. One group received a bolus of the nitric oxide synthase inhibitor, N omega-nitro-L-arginine methyl ester (25 mg/kg), after 24 hrs, and the remaining sheep were given the carrier, sodium chloride 0.9%. MEASUREMENTS AND MAIN RESULTS: The sheep developed a hyperdynamic cardiovascular response characterized by a decrease in systemic vascular resistance index (p < .05), and an increased cardiac index (p < .05) by 24 hrs. The sheep retained fluid, with creatinine clearance decreasing in the presence of chronically increased atrial natriuretic peptide. After the administration of N omega-nitro-L-arginine methyl ester, systemic vascular resistance index and cardiac index returned to baseline values, fluid balance normalized, and glomerular filtration rate increased (p < .05), while the control animals continued to retain fluid and their creatinine clearance continued to decrease. The concentrations of atrial natriuretic peptide did not differ significantly between groups after N omega-nitro-L-arginine methyl ester administration. CONCLUSIONS: In this ovine model of experimental hyperdynamic sepsis, renal excretory function decreases in the presence of chronically increased concentrations of atrial natriuretic peptide. Administration of the nitric oxide synthase inhibitor, N omega-nitro-L-arginine methyl ester, reverses the vasodilatory state, thereby improving fluid balance and glomerular filtration.

Animals↗
PubMed1992

Theoretical analysis of the relationship between the ratio of ventricular systolic elastance to diastolic stiffness and stroke volume.

The maintenance of adequate blood circulation requires a sufficient ventricular contractility; in addition, to eject blood, the ventricles must first receive a sufficient volume, requiring a low diastolic stiffness. A simplified cardiovascular model was used to derive formulae for stroke volume (SV) as a function of atrial pressure and the ratio of ventricular end-systolic elastance to end-diastolic stiffness. A more complex cardiovascular model was used to assess the ability of the expressions to predict stroke volume under various steady-state conditions. The predicted SV correlated linearly with the model SV over a wide range of diastolic stiffnesses and systolic elastance. The formulae predict that with fixed right atrial pressure the SV is proportional to the ratio of end-systolic elastance to end-diastolic stiffness (GR) for the right ventricle, but relatively insensitive to the ratio (GL) for the left ventricle provided that GL is greater than GR. Model simulations confirmed this. When the right atrial pressure was not fixed increases in GR with fixed GL reduced the right atrial pressure with little change in SV. Similarly, varying GL with fixed GR produced little change in SV. The ratios highlight the importance of diastole to cardiac function.

Diastole↗
PubMed2003

Surgical outcome of the maze procedure for atrial fibrillation in mitral valve disease: rheumatic versus degenerative.

BACKGROUND: The results of the maze procedure are known to be less satisfactory in rheumatic mitral disease than in nonrheumatic mitral valve disease. The aim of this study was to determine whether the etiology of mitral valve disease affected surgical outcome. METHODS: From July 1997 to January 2001, 129 consecutive patients with chronic atrial fibrillation associated with mitral valve disease had mitral valve operations with the maze procedure. The underlying mitral pathology was rheumatic in 86 patients (group R) and degenerative in 43 (group D). Echocardiograms and electrocardiograms were performed immediately and then repeated 3 months and 6 months postoperatively. RESULTS: The mean age, duration of atrial fibrillation, and preoperative left atrial size were similar between the groups. There was no operative mortality and no significant difference in cardiopulmonary bypass and aortic cross-clamp times. The sinus conversion rate at 7 days postoperatively was 86% in both groups, and at 6 months it was 95.3% in group R and 97.7% in group D (p > 0.05). The transmitral A wave detection rates in groups R and D at 7 days and 6 months postoperatively were, respectively, 63.1% versus 67.4% and 90.4% versus 91.9% (p > 0.05). The transmitral A wave velocity (cm/second) at the same times (7 days and 6 months postoperatively) was 41.9 +/- 41.6 versus 45.5 +/- 37.7 and 67.8 +/- 38.2 versus 69.8 +/- 35.8 in groups R and D, respectively (p > 0.05). CONCLUSIONS: The maze procedure is equally effective in treating chronic atrial fibrillation in patients with either rheumatic or nonrheumatic mitral valve disease in terms of sinus conversion rate and left atrial transport function.

Atrial Fibrillation↗
PubMed2002

Normal systolic and diastolic functions of the left ventricle and left atrium by cine magnetic resonance imaging.

Volume and phase characteristics of the left ventricle (LV) and left atrium (LA) were assessed in 31 healthy Asian adults (19 males and 12 females) using cine magnetic resonance imaging (MRI) and an automated boundary detection algorithm. Volume indexes of the LV and LA were smaller than published results obtained mostly from Westerners. Other than LV mass index and percent emptying of the LA, there was no gender difference in all LV/LA indexes. In associating LV/LA functions with the body size and heart rate (HR), we found that LV mass and the minimum LA volume correlated strongly with the body surface area, the maximum LA volume and the reservoir volume correlated strongly with the body weight, and the time to LV peak-filling rate (LVPFRt) and the time to LA peak-emptying rate (LAPERt) correlated strongly with the HR. In associating LV with LA functions, we found that LA conduit volume contributed more than 50% of the LV stroke volume, and correlated with both systolic and diastolic functions of the LV. Moreover, LVPFRt and LAPERt were virtually identical, indicating a mechanical coupling between LV and LA during diastole. In conclusion, using time-resolved, three-dimensional volume data obtained from cine MRI, we have established normative values of LV and LA functions and their functional relationships in healthy Asian adults. The imaging acquisition protocol, data analysis algorithms, and the established normative values provide the basis for the study of left heart function in patients.

Adult↗
PubMed2004

Age-dependent biochemical and contractile properties in atrium of transgenic mice overexpressing junctin.

Junctin is a transmembrane protein of the cardiac junctional sarcoplasmic reticulum (SR) that binds to the ryanodine receptor, calsequestrin, and triadin 1. This quaternary protein complex is thought to facilitate SR Ca2+ release. To improve our understanding of the contribution of junctin to the regulation of SR function, we examined the age-dependent effects of junctin overexpression in the atrium of 3-, 6-, and 18-wk-old transgenic mice. The ratio of atrial weight and body weight was unchanged between junctin-overexpressing (JCN) and wild-type (WT) mice at all ages investigated (n=6-8). The protein expression of triadin 1 was decreased starting in 3-wk-old JCN atria (by 69%), whereas the expression of the ryanodine receptor was diminished in 6- (by 48%) and 18-wk-old (by 57%) JCN atria compared with age-matched WT atria. Force of contraction was decreased by 35% in 18-wk-old JCN compared with age-matched WT left atrial muscle strips, which was accompanied by a prolonged time of relaxation (48.1 +/- 0.9 vs. 44.2 +/- 0.8 ms, respectively, n=6-8, P <0.05). The spontaneous beating rate of isolated right atria was higher in 18-wk-old JCN mice compared with age-matched WT mice (389 +/- 10 vs. 357 +/- 6 beats/min, respectively, n=6-8, P <0.05). Heart rate was lower by 9% in telemetric ECG recordings in 18-wk-old JCN mice during stress tests. Three-week-old JCN atria exhibited a higher potentiation of force of contraction at rest pauses of 30 s (by 13%) and of 300 s (by 35%), suggesting increased SR Ca2+ content. This was consistent with the higher force of contraction in 3-wk-old JCN atria (by 29%) compared with age-matched WT atria (by 10%) under the administration of caffeine. We conclude that in 3-wk-old atria, junctin overexpression was associated with a reduced expression of triadin 1 resulting in a higher SR Ca2+ load without changes in contractility or heart rate. In 6-wk-old JCN atria, the compensatory downregulation of the ryanodine receptor may offset the effects of junctin overexpression. Finally, the progressive decrease in ryanodine receptor density may contribute to the decreased atrial contractility and lower heart rate during stress in 18-wk-old JCN mice.

Aging↗
PubMed2004

Prevalence and significance of increased intraventricular velocities in healthy elderly subjects.

BACKGROUND: Heart murmurs are common in the elderly and increased intracavitary velocities (IIV) within the left ventricle have been reported to be a cause of systolic murmur. OBJECTIVE: To assess the prevalence and functional significance of IIV in healthy elderly subjects METHODS: Ambulatory healthy elderly subjects were recruited from community centres and seniors' apartments. They were screened using a structured questionnaire and then underwent a comprehensive history and physical examination. Electrocardiogram, echocardiogram and 6-min walk test were performed on the same day. RESULTS: Four of the 88 subjects were excluded because of significant valvular dysfunction. Ten of the remaining 84 subjects had IIV and their demographics were similar to those of the 74 subjects without IIV. Echocardiographic parameters including left ventricular size and mass were similar between the two groups. Left ventricular mass index was lower in subjects with IIV (P=0.02). Both groups had similar 6-min walk results. CONCLUSIONS: In the healthy elderly who do not have valvular disease or left ventricular hypertrophy, IIV is uncommon and does not appear to have functional significance.

Aged↗
PubMed1984

Recovery of myocardial function following brief versus prolonged atrial pacing stress in the presence of coronary artery stenosis.

The ability of myocardium distal to a severe coronary artery stenosis to recover from brief (5 min) versus prolonged (30 min) atrial pacing stress was compared in this study. Eight closed chest pigs were prepared with a coronary artery stenosis (82% lumenal diameter reduction) in the left anterior descending artery and ultrasonic length sensors in left anterior descending endocardium. Extent of recovery of systolic function 5 min following a brief (5 min) period of ischaemia induced by rapid (175 to 190 min-1) atrial pacing (AP-1) was compared with that following a prolonged (30 min) period of ischaemia induced by rapid atrial pacing (AP-2). Regional myocardial blood flow (ml X min-1 X g-1) was measured at control, during, and following atrial pacing. Regional shortening (%) distal to the stenosis declined versus control at both 5 min of AP-1 (10.0 +/- 7.3 (mean +/- 1 SD) to 0.6 +/- 0.9, p less than 0.01) and 30 min of AP-2 (6.8 +/- 3.3 to 2.1, +/- 3.5, p less than 0.01). However, within 5 min of discontinuing both brief as well as prolonged pacing, regional segmental shortening (5.7 +/- 3.9 and 7.0 +/- 6.9, respectively) returned to 50 to 70% of initial control levels (10.0 +/- 7.3). Regional shortening was similar 5 min following brief and prolonged stress. Distal left anterior descending zone epicardial regional myocardial blood flow increased (p less than 0.01) versus control at AP-1 (1.05 +/- 0.24 to 1.39 +/- 0.24) and 30 min of AP-2 (0.99 +/- 0.21 to 1.40 +/- 0.23).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2003

Evidence of atrial mechanical dysfunction by acoustic quantification in abnormal relaxation and restrictive filling patterns of diastolic dysfunction in patients with coronary artery disease.

AIM: This study made use of acoustic quantification (AQ) to investigate if left atrial (LA) mechanical function was impaired in patients with diastolic dysfunction, which might not be detected by conventional Doppler echocardiography. METHODS: One hundred and ten patients with coronary artery disease (mean age 65+/-11 years, 80% male) underwent echocardiography prospectively while AQ was performed using harmonic imaging at the apical four-chamber view to evaluate LA function. RESULTS: By Doppler echocardiography, left ventricular (LV) diastolic dysfunction in the form of abnormal relaxation pattern (ARP) was present in 84, pseudonormal (PN) in nine and restrictive filling pattern (RFP) in 10 patients. LA mechanical dysfunction with impaired total fractional area change (FAC) of </=20% was present in 17/19 (89%) patients in the RFP/PN group, but was observed in 27/84 (32%) patients with ARP. Despite identical diastolic Doppler indices between patients with ARP with preserved (n=57) and impaired total FAC, the latter group had significantly lower LV ejection fraction (P<0.001), larger LV volumes (P<0.05 and 0.002, respectively), as well as larger LA area (P<0.001) and lower LA peak emptying and filling rates (both P=0.001). In contrast, there was no difference in nearly all of the parameters of LA function, LV systolic function and LV volume between patients with RFP/PN and ARP with FAC </=20%. Both active and passive LA pump functions were impaired in patients with RFP/PN or ARP with FAC </=20%. CONCLUSION: LA mechanical dysfunction was found to be present in one-third of the patients with ARP of diastolic dysfunction despite a high MV-A. It was also present in almost all the patients with RFP/PN pattern of diastolic dysfunction. Therefore, AQ may provide information on atrial mechanical function complementary to that of Doppler echocardiography.

Aged↗