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Biomedical subjects

R A Nishimura

Publications and source records attributed to R A Nishimura.

At least 73 records · Page 4Linked to original sources
PubMed1996

Value of dynamic respiratory changes in left and right ventricular pressures for the diagnosis of constrictive pericarditis.

BACKGROUND: Conventional cardiac catheterization criteria for the diagnosis of constrictive pericarditis (CP) rely on equalization of intracardiac pressures and have many recognized limitations. Recently, Doppler echocardiographic methods have been used to examine dynamic respiratory changes of increased ventricular interdependence and dissociation of intrathoracic and intracardiac pressures for the diagnosis of CP. These pathophysiological features may be best delineated by cardiac catheterization. Therefore, we studied the accuracy of these dynamic respiratory changes in left ventricular and right ventricular pressure for the diagnosis of CP at cardiac catheterization. METHODS AND RESULTS: High-fidelity manometric catheters and respirometry were used to study 36 patients: 15 patients with surgically proven CP (group 1) and 21 patients with other causes of heart failure (group 2). Conventional cardiac catheterization variables used to establish the diagnosis of CP lacked sensitivity and specificity and failed to distinguish between these groups. However, the finding of discordance between right ventricular and left ventricular pressures during inspiration, a sign of increased ventricular interdependence, accurately distinguished patients in group 1 from those in group 2 (P < .05). CONCLUSIONS: Examination of dynamic respiratory changes indicating increased ventricular interdependence may be helpful in the diagnosis of CP in the cardiac catheterization laboratory.

Adult↗
PubMed1996

Effect of dual-chamber pacing on systolic and diastolic function in patients with hypertrophic cardiomyopathy. Acute Doppler echocardiographic and catheterization hemodynamic study.

OBJECTIVES: This study sought to evaluate prospectively the acute hemodynamic effect of dual-chamber pacing by using a combined hemodynamic approach of high fidelity pressure and Doppler velocity measurements. BACKGROUND: Dual-chamber pacing has been proposed recently as an alternative in the symptomatic treatment of patients with hypertrophic obstructive cardiomyopathy. Although early reports documented a decrease in left ventricular outflow tract gradient and symptomatic improvement, questions remain about the hemodynamic effects of dual-chamber pacing on systolic and diastolic function. METHODS: Twenty-nine patients with hypertrophic cardiomyopathy underwent a combined cardiac catheterization and Doppler echocardiographic study during normal sinus rhythm and P-synchronous pacing at various atrioventricular (AV) intervals. High fidelity pressure measurements of left ventricular inflow and left atrial pressures, ascending aortic pressure, thermodilution cardiac output and Doppler mitral flow velocity curves were obtained to evaluate both systolic and diastolic left ventricular function. RESULTS: During AV pacing at the shortest delay of 60 ms, there was a significant decrease in cardiac output (p < 0.05) and peak positive dP/dt (p < 0.05), an increase in mean left atrial pressure (p < 0.05) and a prolongation of tau, the time constant of relaxation (p < 0.05), compared with that during normal sinus rhythm. During pacing at the optimal AV delay (longest AV interval with pre-excitation), there was a similar trend, with deterioration in both systolic and diastolic function variables but of lesser magnitude than that during pacing at the shortest AV intervals. The deterioration in both systolic and diastolic function was present in 21 patients with and 8 without left ventricular outflow obstruction. There was a modest decrease in left ventricular outflow tract gradient from 73.3 +/- 45.0 (mean +/- SD) to 61.3 +/- 40.5 mm Hg (p = 0.03) during dual-chamber pacing at the optimal AV delay compared with that during normal sinus rhythm. CONCLUSIONS: The acute effect of pacing the right atrium and ventricle may be detrimental to both systolic and diastolic function of the left ventricle, particularly at the short AV intervals. Further studies of the long-term effects of dual-chamber pacing in carefully performed randomized studies are needed.

Blood Flow Velocity↗
PubMed1996

Hypertrophic obstructive cardiomyopathy: preoperative echocardiographic predictors of outcome after septal myectomy.

OBJECTIVES: The purpose of this study was to determine whether two-dimensional and Doppler echocardiography are predictive of clinical outcome in patients with hypertrophic obstructive cardiomyopathy who undergo septal myectomy. BACKGROUND: Surgical myectomy provides excellent relief of symptoms in most patients with hypertrophic obstructive cardiomyopathy who are severely symptomatic despite medical therapy. There is a subset of patients who will remain symptomatic even after operation. Because comprehensive two-dimensional and Doppler echocardiography can define the range of anatomic and associated pathophysiologic abnormalities, it was hypothesized that preoperative echocardiographic variables may be predictive of clinical outcome after septal myectomy. METHODS: The clinical, electrocardiographic (ECG), echocardiographic and surgical data of 47 adult patients with hypertrophic cardiomyopathy who underwent isolated septal myectomy from 1986 to 1992 were analyzed. Specific symptoms were evaluated both preoperatively and at 1 year postoperatively. Electrocardiography and echocardiography were performed preoperatively and postoperatively. The ECG and echocardiographic variables were analyzed to determine whether any were predictive of residual symptoms 1 year postoperatively. RESULTS: The mean [+/-SD] age of the patients was 47 +/- 15 years. All were New York Heart Association functional class III or IV. Dyspnea was present in all 47 patients and was severe in 70%. Most patients experienced symptomatic improvement at 1 year; dyspnea persisted in 26 patients (55%). The preoperative echocardiographic variables of asymmetric hypertrophy, severe systolic anterior motion of the mitral leaflet(s) and prolonged isovolumetric relaxation time were independent predictors of mild or no residual dyspnea postoperatively. CONCLUSIONS: This initial study shows that the preoperative echocardiographic variables of asymmetric hypertrophy, severe systolic anterior motion of the mitral leaflet(s) and prolonged isovolumetric relaxation time can identify patients who are most likely to benefit from septal myectomy.

Adult↗
PubMed1996

Doppler evaluation of patients with constrictive pericarditis: use of tricuspid regurgitation velocity curves to determine enhanced ventricular interaction.

OBJECTIVES: This study sought to examine the value of analyzing Doppler echocardiographically derived tricuspid regurgitation signals during respiration in relation to the diagnosis of constrictive pericarditis. BACKGROUND: A physiologic hallmark of constrictive pericarditis is enhanced ventricular interdependence, which produces reciprocal changes in right and left ventricular filling and ejection dynamics during the respiratory cycle. It was hypothesized that these changes could be detected noninvasively by analyzing Doppler echocardiographically derived tricuspid regurgitation signals and that this information could assist in noninvasively diagnosing constrictive pericarditis. METHODS: Simultaneous Doppler echocardiography and catheterization studies of the right and left sides of the heart with high fidelity pressure manometers were performed in 5 patients with surgically confirmed constrictive pericarditis and 12 patients (control subjects) with heart failure due to other causes. RESULTS: Changes observed in tricuspid regurgitation Doppler echocardiographic variables from onset to peak inspiration in patients with constrictive pericarditis were significantly different from those in control subjects. Mean (+/- SD) percent change in maximal tricuspid regurgitation velocity was 13% +/- 6% and -8% +/- 7% in the constrictive pericarditis and control groups, respectively (p < 0.0001); mean percent change in tricuspid regurgitation signal duration was 18% +/- 2% and -2% +/- 7%, respectively (p < 0.0001); mean percent change in tricuspid regurgitation time velocity integral was 27% +/- 15% and -10% +/- 12%, respectively (p < 0.0001). CONCLUSIONS: Respiratory changes in Doppler echocardiographically derived tricuspid regurgitation peak velocity and velocity duration are increased in patients with constrictive pericarditis and may be helpful in diagnosing this condition noninvasively.

Aged↗
PubMed1996

Analysis of left ventricular diastolic function.

Our understanding of left ventricular diastolic function has evolved with our understanding of Doppler echocardiographic assessment of left ventricular filling dynamics. Left ventricular diastolic function consists of several variables which affect the Doppler echocardiographic recordings in a complex way. While there are still limitations with the non-invasive assessment of left ventricular diastolic function and filling pressures by Doppler echocardiography, great progress has been made and careful interpretation of properly obtained Doppler recordings can give clinically relevant information concerning left ventricular diastolic function, filling pressures, and prognosis in patients with cardiac disease.

Diastole↗
PubMed1996

Superiority of brain natriuretic peptide as a hormonal marker of ventricular systolic and diastolic dysfunction and ventricular hypertrophy.

Atrial and brain natriuretic peptides (ANP and BNP) are produced by the heart, and their plasma concentrations are increased in human chronic congestive heart failure. Although separate studies have suggested that circulating levels of the biologically active C-terminal ANP, the biologically inactive N-terminal ANP, and BNP may have diagnostic utility in the detection of left ventricular systolic dysfunction or left ventricular hypertrophy, no studies have directly assessed the relative value of these peptides prospectively. We therefore designed this study to compare the relative ability of the different natriuretic peptides to detect abnormal left ventricular systolic and diastolic function and left ventricular hypertrophy. Using a prospective study design, we investigated 94 patients referred for cardiac catheterization and 15 age-matched normal subjects. The diagnostic abilities of elevated plasma C-terminal ANP, N-terminal ANP-(1-30), and BNP concentrations to identify systolic dysfunction (ejection fraction < 45%), diastolic dysfunction (time constant of left ventricular relaxation > 55 milliseconds, left ventricular end-diastolic pressure > 18 mm Hg), and left ventricular hypertrophy (left ventricular mass index > 120 g/m2) were objectively compared by receiver operating characteristic analysis. The areas under the receiver operating characteristic curve of BNP for detecting each of these abnormalities ranged from 0.715 to 0.908 and were significantly greater than those of C-terminal ANP or N-terminal ANP-(1-30). The sensitivity and specificity of an elevated plasma BNP, which we defined as greater than the mean + 3 SD of the 15 age-matched normal subjects, were 0.83 and 0.77, respectively, for detecting ejection fraction less than 45%, 0.85 and 0.70 for detecting the time constant of left ventricular relaxation greater than 55 milliseconds, 0.63 and 0.76 for detecting left ventricular end-diastolic pressure greater than 18 mm Hg, and 0.81 and 0.85 for detecting left ventricular mass index greater than 120 g/m2. The use of BNP and one other peptide increased sensitivity (0.90 to 0.96), albeit with lower specificity (0.56 to 0.71). An elevated plasma BNP was a more powerful marker of left ventricular systolic dysfunction, left ventricular diastolic dysfunction, and left ventricular hypertrophy than C-terminal ANP or N-terminal ANP-(1-30) in this population of patients with suspected cardiac disease. Measurement of BNP alone or in combination with C-terminal ANP or N-terminal ANP-(1-30) has potential utility for the detection of altered left ventricular structure and function in a patient population at risk for cardiovascular disease.

Aged↗
PubMed1996

Dual-chamber pacing for cardiomyopathies: a 1996 clinical perspective.

Implantation of a permanent pacemaker is an accepted mode of therapy for symptomatic bradyarrhythmias. Application of pacemaker technology for the treatment of cardiomyopathies has generated considerable interest and enthusiastic support in recent years. In both hypertrophic cardiomyopathy and dilated cardiomyopathy, dual-chamber pacing has been shown to decrease symptoms and improve hemodynamics; however, not all patients will benefit from dual-chamber pacing. Technical considerations must be acknowledged in order to obtain optimal benefit with dual-chamber pacing. In addition, other more accepted therapies are available for patients with symptomatic cardiomyopathies. The purposes of this article are to review critically the current literature on the use of dual-chamber pacemakers in patients with either hypertrophic or dilated cardiomyopathy and to provide a clinical perspective based on current knowledge.

Cardiac Pacing, Artificial↗
PubMed1995

Endothelin in coronary endothelial dysfunction and early atherosclerosis in humans.

BACKGROUND: The endothelium modulates vascular tone through release of vasodilating substances, such as endothelium-derived relaxing factors, and vasoconstricting substances, such as endothelin. Endothelin concentrations are elevated in humans with atherosclerosis and in hypercholesterolemic pigs. Furthermore, the endothelium-dependent vasodilator acetylcholine increases endothelin in hypercholesterolemia in association with coronary vasoconstriction. The present study was designed to test the hypotheses that coronary endothelial dysfunction in humans is characterized by enhanced coronary and circulating endothelin and that the vasoconstriction associated with acetylcholine results in further release of coronary endothelin. METHODS AND RESULTS: Coronary and circulating endothelin concentrations were measured at baseline and during intracoronary acetylcholine administration in 20 patients undergoing diagnostic coronary angiography. Patients were divided into two groups on the basis of their response to intracoronary acetylcholine. Group 1 (n = 7) demonstrated a normal vasodilatory response, but group 2 (n = 13) demonstrated coronary vasoconstriction. Baseline coronary and circulating endothelin concentrations (as determined by coronary sinus and femoral artery measurements, respectively) were higher in patients who responded to acetylcholine with coronary vasoconstriction (group 2) than in group 1 patients (coronary sinus, 15.9 +/- 1.0 pg/mL versus 7.1 +/- 1.0 pg/mL; femoral, 14.1 +/- 0.9 pg/mL versus 6.8 +/- 1.0 pg/mL, respectively; P < .01). In response to intracoronary acetylcholine, a further increase in coronary endothelin was observed only in group 2; this increase correlated with changes in coronary artery diameter. CONCLUSIONS: This study demonstrates that endothelin immunoreactivity is enhanced in the coronary and systemic circulation in humans with coronary endothelial dysfunction. Moreover, acetylcholine further increased coronary endothelin concentration in patients with coronary endothelial dysfunction and was associated with coronary vasoconstriction. These observations strongly support a role for endothelin as an early participant in and marker for coronary endothelial dysfunction in humans.

Acetylcholine↗
PubMed1995

Intravascular ultrasound to assess anastomotic patency after lung transplantation.

Pulmonary arterial anastomotic stenosis is an unusual complication after single-lung transplantation. Intravascular ultrasound, performed at the bedside with an introducer sheath and guidewire, is a new technique that provides high-resolution tomographic images of the anastomotic site. This modality was used early in the postoperative course of a 58-year-old man to exclude significant pulmonary arterial anastomotic narrowing after right single-lung transplantation for primary pulmonary hypertension.

Constriction, Pathologic↗
PubMed1995

Outcome of cardiac surgery for carcinoid heart disease.

OBJECTIVES: The hypothesis was that cardiac surgery for symptomatic carcinoid heart disease in conjunction with adjunctive therapy could improve the long-term outlook of patients with carcinoid heart disease. BACKGROUND: Patients with carcinoid heart disease have a dismal prognosis; most die of progressive right heart failure within 1 year after onset of symptoms. Improved therapies for the systemic manifestations of the carcinoid syndrome have resulted in symptomatic improvement and prolonged survival in patients without heart disease. METHODS: Twenty-six patients with symptomatic carcinoid heart disease underwent valvular surgery. Preoperative clinical, laboratory, Doppler echocardiographic and hemodynamic factors were evaluated. The survival of the surgical group was compared with that of a control group of 40 medically treated patients. RESULTS: There were nine perioperative deaths (35%), primarily from postoperative bleeding and right ventricular failure. Of the 17 surgical survivors, 8 were alive at a mean of 28 months of follow-up. The postoperative functional class of the eight surviving patients was substantially improved. Late deaths were primarily due to hepatic dysfunction caused by metastatic disease. The only predictor of operative mortality (p = 0.03) was low voltage on preoperative electrocardiography (limb lead voltage < or = 5 mm). Predictors of late survival included a lower preoperative somatostatin requirement and a lower preoperative urinary 5-hydroxy-indoleacetic acid level. There was a trend toward increased survival for the surgical group compared with the control group. CONCLUSIONS: Because new therapies have improved survival in patients with the malignant carcinoid syndrome, cardiac involvement has become a major cause of morbidity and mortality. Valve surgery is the only definitive treatment. Although cardiac surgery carries a high perioperative mortality, marked symptomatic improvement occurs in survivors. Surgical intervention should therefore be considered when cardiac symptoms become severe.

Actuarial Analysis↗
PubMed1995

Mechanism of hemodynamic improvement by dual-chamber pacing for severe left ventricular dysfunction: an acute Doppler and catheterization hemodynamic study.

OBJECTIVES: This study was undertaken to determine the mechanism by which improvement in hemodynamic variables may occur with dual-chamber pacing in patients with severe left ventricular dysfunction. BACKGROUND: Dual-chamber pacing has recently been proposed as a therapeutic alternative for the relief of symptoms in patients with dilated cardiomyopathy. METHODS: Fifteen patients with severe left ventricular systolic dysfunction were studied acutely during atrioventricular (AV) sequential pacing at various AV intervals (60, 100, 120, 140, 180 and 240 ms) with use of combined Doppler velocity curves and pressures obtained by high fidelity manometer-tipped catheters and thermodilution cardiac output. RESULTS: Neither cardiac output nor mean left atrial pressure was significantly different when hemodynamic variables in the baseline state were compared with those during AV sequential pacing at the various AV intervals in all patients. The patients were classified into two groups. In group I (eight patients with PR intervals > 200 ms on the rest 12-lead electrocardiogram), cardiac output was significantly increased when AV sequential pacing at the optimal AV interval to output was compared with that at the baseline state (3.0 +/- 1.0 vs. 3.9 +/- 0.43 liters/min, p = 0.005) because timing of mechanical atrial and ventricular synchrony was optimized. In addition, left ventricular end-diastolic pressure and duration of diastolic filling were increased, and diastolic mitral regurgitation was abolished. In group II (seven patients who had normal AV conduction at rest), cardiac output during AV pacing decreased from the baseline value without change in the diastolic filling period. CONCLUSIONS: Dual-chamber pacing may improve acute hemodynamic variables in selected patients with dilated cardiomyopathy, mainly by optimization of the timing of mechanical atrial and ventricular synchrony. Reestablishment of the optimal diastolic filling period and abolition of diastolic mitral regurgitation may also contribute to hemodynamic improvement.

Aged↗
PubMed1995

Epicardial vasomotor responses to acetylcholine are not predicted by coronary atherosclerosis as assessed by intracoronary ultrasound.

OBJECTIVES: The purpose of this study was to use intravascular ultrasound to determine the morphologic appearance of the coronary arteries, relating the absence, presence and extent of atherosclerosis to the response of the coronary arteries to acetylcholine infusion. BACKGROUND: Endothelial function plays a major role in the pathophysiology of myocardial ischemia and angina pectoris. The response of the coronary arteries to selective infusion of acetylcholine has been used to examine endothelial function, with vasoconstriction occurring in the absence of intact endothelial function. Vasoconstriction to acetylcholine infusion in humans without overt coronary artery disease has been attributed to early atherosclerosis not detected by coronary angiography. METHODS: Twenty-nine patients without overt coronary artery disease underwent selective coronary angiography and selective intracoronary infusion of increasing concentrations of acetylcholine (10(-6), 10(-5) and 10(-4) mol/liter), followed by intravascular ultrasound imaging. RESULTS: The response of the coronary arteries to acetylcholine infusion was not dependent on the absence or presence of atherosclerotic plaque, as detected by intravascular ultrasound. The percent change in epicardial coronary artery diameter during acetylcholine infusion versus baseline was -14 +/- 28% (mean +/- SD) in the seven patients with no visible atherosclerosis on intravascular ultrasound versus -9 +/- 20% in the 22 patients with visible atherosclerosis on intravascular ultrasound (p = NS, confidence interval -14% to 25%). There was a greater vasoconstrictive response to acetylcholine infusion in patients with risk factors for coronary artery disease than in those without risk factors (p = 0.003). CONCLUSIONS: The vasoreactive response to acetylcholine is not necessarily dependent on ultrasound detection of the presence or absence of atherosclerosis.

Acetylcholine↗
PubMed1995

Reoperation for aortic valve periprosthetic leakage: identification of patients at risk and results of operation.

Periprosthetic leakage occurs in 1 to 3.5% of patients after aortic valve replacement. Antecedent or active infection increases the risk of perivalvular leakage. Other factors predisposing to perivalvular leakage have not been clearly identified. To determine whether clinical and/or early transthoracic echocardiographic features can identify patients who require reoperation for periprosthetic leakage, we reviewed 1,743 consecutive patients who underwent aortic valve replacement from 1983 through 1991. Thirty patients (1.7%) subsequently required repeat operation for correction of periprosthetic leakage, at a median of 18.0 months (range 0.5-81.0) after aortic valve replacement. Comparison of these 30 patients with periprosthetic leakage to those undergoing primary aortic valve replacement showed no differences in patient age, gender, native valve disease type or etiology, prosthetic valve type, or prosthetic valve size (all p = NS). Of the 30 patients with periprosthetic leaks, 20 had early postoperative transthoracic echocardiography, at a median 5.3 months (range 0.3 - 40.0) after aortic valve replacement. In this early postoperative study, 14 patients (70.0%) had no periprosthetic leak detectable by echocardiography; two patients had trivial leaks, and only four patients had significant periprosthetic leakage by echocardiography. During subsequent operation, aortic valve re-replacement was performed in 26 patients (86.7%), and the periprosthetic leak was repaired in the remaining four patients. Thirty-day and 5-year survival probabilities were 0.90 (70% CI, 0.84-0.96) and 0.73 (70% CI, 0.65-0.82), respectively. It is concluded that in this study, there were no clinical features that distinguished patients undergoing aortic valve replacement who later developed severe perivalvular leakage.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1994

Accurate measurement of the transmitral gradient in patients with mitral stenosis: a simultaneous catheterization and Doppler echocardiographic study.

OBJECTIVES: This study compared the accuracy of Doppler echocardiography with that of conventional cardiac catheterization in the measurement of transmitral gradients in patients with mitral stenosis. BACKGROUND: Simultaneous measurement of left atrial and left ventricular pressures is the most accurate method for determination of the mean mitral valve gradient in patients with mitral stenosis. Because of the inherent risks of transseptal catheterization, pulmonary capillary wedge pressure has been used in many invasive laboratories for determination of the mean mitral valve gradient. Recent studies have observed significant errors when pulmonary capillary wedge pressure was used for these measurements. Doppler echocardiography provides a noninvasive alternative for measurement of the transmitral gradient, but its relative accuracy has remained unclear. METHODS: Seventeen patients with mitral stenosis who underwent transseptal cardiac catheterization had simultaneous measurement of 1) transmitral gradient by direct left atrial and left ventricular pressures, 2) transmitral gradient by pulmonary capillary wedge and left ventricular pressures, and 3) transmitral gradient by Doppler echocardiography. RESULTS: Transmitral gradient measured by pulmonary capillary wedge and left ventricular pressures significantly overestimated the gradient obtained by direct measurement of left atrial pressure, with a mean (+/- SD) difference of 3.3 +/- 3.5 mm Hg (or 53%). Correcting the pulmonary capillary wedge pressure for the phase shift resulted in better correlation, but a consistent overestimation still remained, with a mean difference of 2.5 +/- 2.9 mm Hg (or 43%). The best correlation with the smallest variability was comparison of the Doppler-derived mean gradient with the gradient from direct measurement of left atrial and left ventricular pressures, with a mean difference of 0.2 +/- 1.2 mm Hg. CONCLUSIONS: Compared with the transmitral gradient obtained by direct measurement of left atrial and left ventricular pressures, the Doppler-derived gradient is more accurate than that obtained by conventional cardiac catheterization and should be considered the reference standard.

Adult↗