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Biomedical subjects

R A Nishimura

Publications and source records attributed to R A Nishimura.

At least 109 records · Page 6Linked to original sources
PubMed1991

Follow-up of patients with low output, low gradient hemodynamics after percutaneous balloon aortic valvuloplasty: the Mansfield Scientific Aortic Valvuloplasty Registry.

Symptomatic patients with a low cardiac output and low aortic valve gradient have a poor prognosis but are at high risk for aortic valve surgery. The outcome of percutaneous balloon aortic valvuloplasty in this subgroup of patients is unclear. Therefore, 67 patients (group 1) underwent percutaneous balloon aortic valvuloplasty between December 1, 1986 and November 1, 1987 who had a low cardiac index (less than 2.5 liters/min per m2) and a low aortic valve gradient (less than or equal to 40 mm Hg) before the procedure. The results were compared with 200 patients (group 2) who had a low cardiac index but not a low aortic valve gradient (greater than 40 mm Hg) before the procedure and who had similar baseline presenting symptoms. After balloon aortic valvuloplasty, there was a greater decrease in aortic valve gradient in patients in group 2 than in patients in group 1 (mean +/- SD -33.0 +/- 16.7 mm Hg and -14.6 +/- 6.9 mm Hg, respectively; p less than 0.001) although there was no significant difference in improvement in estimated aortic valve area (0.31 +/- 0.21 and 0.31 +/- 0.22 cm2, respectively; p = NS). In-hospital mortality was 11.9% for patients in group 1 which was not significantly different from the 7.5% mortality for patients in group 2. However, the actuarial probability of survival at 12 months for patients who survived the initial hospitalization was 46% in group 1 and 64% in group 2 (p less than 0.05). Moreover, at follow-up (mean 8.8 months) 64% of surviving group 1 patients displayed clinical improvement, compared with 70% of surviving group 2 patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1991

Degenerative aortic stenosis. One effect of the graying of America.

Degenerative calcific aortic stenosis is evolving as a common geriatric problem. Once symptoms develop, it is a highly lethal disease that does not respond well to medical therapy. Aortic balloon valvuloplasty may offer palliation but is unlikely to alter the overall course of the disease. Aortic valve replacement is the therapy of choice, but high perioperative morbidity and mortality rates can be expected in the very elderly. The presence of other appreciable cardiac disorders may contribute to the occurrence of postoperative complications. Patients with asymptomatic aortic stenosis and normal left ventricular function can be treated medically and followed with serial aortic valve area determinations using Doppler echocardiography.

Aged↗
PubMed1991

Predictors of early mortality in patients with angiographically documented left main coronary artery disease.

To determine predictors of early death after coronary angiography in patients with significant left main coronary artery disease (greater than or equal to 60% diameter narrowing, LMCAD), we reviewed the clinical records of patients with LMCAD who died after angiography. Of 1,288 patients with LMCAD studied between January 1978 and October 1989, 21 died within 2 days after angiography (group 1). As a control group, 85 patients were randomly sampled from 1,196 patients who survived at least 30 days after angiography (group 2). The predictors of early death after angiography in patients with LMCAD were older age (P less than 0.05), New York Heart Association Class III or IV (P less than 0.005), shorter duration of unstable angina (P less than 0.005), higher left ventricular end-diastolic pressure (P less than 0.006), lower ejection fraction (P less than 0.005), and significant left circumflex artery disease (P less than 0.006). The use of heparin infusion after angiography did not appear to be a significant factor. It is suggested that earlier operation or more aggressive management be undertaken in patients who, at cardiac catheterization, have significant LMCAD associated with the above-listed variables.

Aged↗
PubMed1991

Percutaneous balloon mitral valvuloplasty: the learning curve.

PBMV is a catheter-based approach to nonsurgically relieving obstruction to mitral inflow in patients with symptomatic mitral stenosis. Since 1986, 50 patients at the Mayo Clinic have undergone the procedure, utilizing either the Inoue pillow-shaped balloon or a dual-balloon technique with excellent early hemodynamic and symptomatic results. Mean mitral valve area increased from 1.06 +/- 0.32 cm2 to 2.01 +/- 0.70 cm2, and transmitral gradient decreased from 15.7 +/- 7.1 mm Hg to 7.5 +/- 3.9 mm Hg. This improvement has been sustained during short-term and intermediate-term follow-up. A marked improvement in procedural success and complication rates is attributable to refinement of patient selection criteria, technical advances in the procedure, and operator experience. There have been three procedure-related deaths; one of these was in a patient who developed severe mitral regurgitation after PBMV and underwent emergency valve replacement. Unfavorable outcomes appear to be related to three factors: presence of thick, calcified valve leaflets with extensive subvalvular involvement, poor general medical status, and operator inexperience.

Adult↗
PubMed1991

In-hospital mortality after balloon aortic valvuloplasty: frequency and associated factors.

Percutaneous balloon aortic valvuloplasty has been accompanied by significant early periprocedural morbidity and mortality. Identification of factors associated with increased mortality might allow for improved selection of patients. The Mansfield Scientific Balloon Aortic Valvuloplasty Registry was analyzed to identify the frequency of in-hospital death and the factors associated with it. Of 492 patients undergoing the procedure, 37 (7.5%) died during the hospital stay in which valvuloplasty was performed. Twenty-four of these patients died within the first 24 h and the remainder died within 7 days after the procedure. There were significant differences in baseline clinical and hemodynamic characteristics as well as procedural and postprocedural variables between patients dying and those surviving the in-hospital period. Multivariate analysis identified four factors associated with increased mortality: 1) the occurrence of a procedure-related complication, 2) a lower initial left ventricular systolic pressure, 3) a smaller final aortic valve area, and 4) a lower baseline cardiac output. Thus, baseline hemodynamic, procedural and postprocedural variables and complications can be identified that are associated with increased mortality.

Aged↗
PubMed1991

Efficacy of percutaneous mitral balloon valvuloplasty with the inoue balloon.

Percutaneous mitral balloon valvuloplasty has become an accepted technique for use in selected patients with severe, symptomatic mitral stenosis. Recently, a new balloon catheter with an "hourglass" shape and specially designed guidewires and dilators has become available (Inoue balloon). The design of this balloon provides ease of manipulation and self-stabilization across the mitral valve during inflation. These features should decrease the incidence of complications associated with the procedure. Preliminary results in 12 consecutive patients who underwent percutaneous mitral balloon valvuloplasty with the Inoue balloon are presented. The mitral valve area increased from 0.92 +/- 0.21 cm2 before the procedure to 1.75 +/- 0.40 cm2 after the procedure. No complications occurred from the procedure, including no increase in severity of mitral regurgitation or creation of an atrial septal defect. Further follow-up is necessary to determine the long-term efficacy with this new balloon. Nonetheless, the preliminary results are encouraging.

Adult↗
PubMed1991

Lipoprotein analysis in the evaluation of chest pain in the emergency department.

Apolipoproteins were measured in a prospective blinded fashion in blood specimens from patients with chest pain in the emergency department. A definitive diagnosis for the chest pain (non-cardiac-related in 32% and angina or myocardial infarction in 68%) was available in 136 of the 162 patients originally enrolled in the study. Logistic regression and multivariate analysis failed to show any usefulness of apolipoprotein determinations in distinguishing patients with cardiac ischemia from those without it. The clinician's initial impression of the chest pain, the electrocardiogram, a history of previous angina, myocardial infarction, or peripheral atherosclerosis, and male sex were strongly associated with the final diagnosis. We conclude that, although apolipoprotein analysis has proved useful in epidemiologic studies, the most reliable indicators of ischemic pain remain the medical history, the electrocardiogram, and the clinician's overall initial impression.

Aged↗
PubMed1991

Natural history of moderate aortic stenosis.

The natural history of severe, symptomatic aortic stenosis has been well documented. However, the natural history of moderate aortic stenosis remains poorly understood. Therefore, a group of 66 patients was identified who had a diagnosis of moderate aortic stenosis at the time of cardiac catheterization (aortic valve area 0.7 to 1.2 cm2) and who did not have surgical therapy during the 1st 180 days after cardiac catheterization. During a mean follow-up period of 35 months, 14 patients died of causes attributed to aortic stenosis and 21 underwent aortic valve replacement. The estimated probability for remaining free of any complication of aortic stenosis at the end of the first 4 years was 59%. Symptomatic patients with decreased ejection fraction or hemodynamic evidence of left ventricular decompensation were at greater risk for these complications. It is concluded that patients with moderate aortic stenosis are at significant risk for the development of complications.

Aged↗
PubMed1990

The natural history of adults with asymptomatic, hemodynamically significant aortic stenosis.

The natural history of asymptomatic, hemodynamically significant, valvular aortic stenosis in adults was documented. Of 471 patients with aortic stenosis identified by Doppler echocardiography (peak systolic flow velocity greater than or equal to 4 m/s) from January 1984 through August 1987, 143 were asymptomatic and had isolated valvular aortic stenosis. Thirty patients underwent aortic valve intervention within 3 months (group 1); the remaining 113 patients did not have an intervention within 3 months (group 2). Follow-up information was available for all patients; the mean duration of follow-up study was 20 months (range 6 to 48). Three cardiac events occurred in the 30 group 1 patients after operation (two deaths, one reoperation). Among the 113 group 2 patients, three had cardiac death presumed to be a result of the aortic stenosis; all three developed symptoms at least 3 months before death. The actuarial probability of remaining free of symptoms of angina, dyspnea or syncope for group 2 was 86% at 1 year and 62% at 2 years. For this group, the 1 and 2 year probabilities of remaining free of cardiac events, including aortic valve intervention or cardiac death, were 93% and 74%, respectively. Of all clinical and echocardiographic variables (group 2), only Doppler flow velocity (p = 0.004) and ejection fraction (p = 0.01) were independent predictors of subsequent cardiac events. Among the 44 patients (groups 1 and 2) with a flow velocity greater than or equal to 4.5 m/s, the relative risk of sustaining a cardiac event (by Cox regression analysis) was 4.9 (p = 0.004).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Intravascular ultrasound imaging: in vitro validation and pathologic correlation.

Intravascular ultrasound imaging is a new method in which high resolution images of the arterial wall are obtained with use of a catheter placed within an artery. An in vitro Plexiglas well model was used to validate measurements of the luminal area, and an excellent correlation was obtained. One hundred thirty segments of fresh peripheral arteries underwent ultrasound imaging and the findings were compared with the corresponding histopathologic sections. Luminal areas determined with ultrasound imaging correlated well with those calculated from microscopic slides (r = 0.98). Three patterns were identified on the ultrasound images: 1) distinct interface between media and adventitia, 2) indistinct interface between media and adventitia but different echo density layers, and 3) diffuse homogeneous appearance. The types of patterns depended on the relative composition of the media and adventitia. Calcification of intimal plaque obscured underlying structures. Atherosclerotic plaque was readily visualized but could not always be differentiated from the underlying media.

Adult↗
PubMed1990

Percutaneous balloon valvuloplasty.

In the technique of percutaneous balloon valvuloplasty, one or more large balloons are inserted percutaneously and then inflated across a stenotic valve to decrease the degree of obstruction. Currently, the procedure is being performed for patients with pulmonic, mitral, or aortic stenosis. The results vary according to the type of valve and the age of the patient. In patients with pulmonic stenosis, balloon valvuloplasty can be performed safely and the results are excellent. Therefore, at many institutions it is the procedure of choice for the treatment of isolated pulmonic stenosis. In patients with mitral stenosis, the results depend on the morphologic features of the stenotic valve. In patients with highly calcified and fibrotic mitral valve leaflets, the risks of the procedure are increased and the results are suboptimal. In experienced hands, however, balloon valvuloplasty is excellent for patients with a pliable, noncalcified mitral valve or those for whom operation imposes an extremely high risk. The use of balloon valvuloplasty for aortic stenosis has been limited to the frail, elderly patient who either is not a surgical candidate or is at high risk for operation. Although mortality and restenosis rates are high on short-term follow-up, aortic balloon valvuloplasty provides palliation of symptoms in many patients who otherwise would have been unable to undergo any intervention. Long-term follow-up is necessary for determining the ultimate role of balloon valvuloplasty in cardiology.

Aortic Valve Stenosis↗
PubMed1990

Does intracoronary infusion of Fluosol-DA 20% prevent left ventricular diastolic dysfunction during coronary balloon angioplasty?

Distal intracoronary infusion of the perfluorochemical Fluosol-DA 20% has been shown to prevent systolic dysfunction during coronary artery balloon occlusion in coronary angioplasty. To assess its effect on global diastolic dysfunction, a randomized, single-blind, crossover protocol comparing intracoronary infusion of Fluosol or no infusion (control) was performed during 60 s balloon inflations in 10 patients (mean age 67 years) undergoing coronary angioplasty. Assessment of global systolic and diastolic function was obtained with high fidelity micromanometer measurements of left ventricular pressure. Eighteen pairs of balloon inflations (Fluosol versus control) were analyzed. Patients reported significantly less severe chest pain during inflations accompanied by Fluosol compared with control. However, during coronary balloon occlusion, no significant differences in the changes from baseline values were observed between Fluosol and control with regard to ventricular relaxation, including the time constant of early ventricular relaxation (tau) and maximal rate of fall in left ventricular pressure (maximal negative dP/dt). No differences between Fluosol and control were observed in terms of the increase in end-diastolic pressure or minimal diastolic pressure during balloon inflation. Mean systolic pressure decrease from baseline values was greater during control than during Fluosol inflations (-9.0 +/- 3.3 mm Hg, p = 0.013), but no significant difference was observed in the change in maximal rate of rise in left ventricular pressure (maximal positive dP/dt). These results suggest that Fluosol does not preserve global left ventricular diastolic function during coronary balloon occlusion, possibly because of its limited oxygen delivery capability relative to arterial blood.

Aged↗
PubMed1990

Preoperative and intraoperative echocardiography to detect right-to-left shunt in patients undergoing neurosurgical procedures in the sitting position.

In patients undergoing neurosurgical procedures at high risk for venous air embolism (VAE), the presence of a right-to-left shunt adds an additional risk for paradoxical air embolism (PAE). Although this is a rare complication, it can have devastating results. The most common form of right-to-left shunt is a patient foramen ovale (PFO), which can be detected by contrast echocardiography. This study evaluates the efficacy of preoperative precordial and intraoperative transesophageal echocardiography (TEE) to detect right-to-left shunting in patients undergoing neurosurgical procedures while in the sitting position. In 101 patients precordial contrast echocardiography was performed prior to surgery. The Valsalva maneuver was utilized as a provocative maneuver to facilitate demonstration of right-to-left shunting. Fifty-one of these patients also had intraoperative TEE monitoring. Right-to-left shunting was demonstrated in only six of the 101 patients examined. Of these, four were detected by TEE. This is less than the expected incidence based on the known incidence of PFO in the general population. The usefulness of preoperative ECHO as a screening test for PFO in patients undergoing neurosurgical procedures is limited, but when a PFO is found, valuable information is acquired to help manage these patients.

Cervical Vertebrae↗
PubMed1990

Intravascular US of the distal aorta and iliac vessels: initial feasibility studies.

Intravascular ultrasound (US) imaging is a new, evolving technique in which a high-frequency transducer is placed on the tip of a catheter. With this device it is possible to obtain high-resolution images of vessel structure in real time. This may provide valuable information about the degree of stenosis, as well as the type and extent of atherosclerotic plaque, in relation to the underlying tunica media and adventitia. The intravascular US catheter was used in seven patients undergoing transfemoral angiography because of arteriosclerosis obliterans. High-resolution images were obtained in all seven patients, and no complications were noted. Various US findings were demonstrated and correlated with the angiographic findings.

Aged↗
PubMed1990

Relation of pulmonary vein to mitral flow velocities by transesophageal Doppler echocardiography. Effect of different loading conditions.

It has previously been demonstrated that predictable changes occur in mitral flow velocities under different loading conditions. The purpose of this study was to relate changes in pulmonary venous and mitral flow velocities during different loading conditions as assessed by transesophageal echocardiography in the operating room. Nineteen patients had measurements of hemodynamics, that is, mitral and pulmonary vein flow velocities during the control situation, a decrease in preload by administration of nitroglycerin, an increase in preload by administration of fluids, and an increase in afterload by infusion of phenylephrine. There was a direct correlation between the changes in the mitral E velocity and the early peak diastolic velocity in the pulmonary vein curves (r = 0.61) as well as a direct correlation between the deceleration time of the mitral and pulmonary venous flow velocities in early diastole (r = 0.84). This indicates that diastolic flow velocity in the pulmonary vein is determined by the same factors that influence the mitral flow velocity curves. A decrease in preload caused a significant reduction in the initial E velocity and prolongation of deceleration time, and an increase in preload caused an increase in E velocity and shortening of deceleration time. An increase in afterload produced a variable effect on the initial E velocity and deceleration time and was dependent on the left ventricular filling pressure. The change in systolic forward flow velocity in the pulmonary vein was directly proportional to the change in cardiac output (r = 0.60). The pulmonary capillary wedge pressure correlated best with the flow velocity reversal in the pulmonary vein at atrial contraction (r = 0.81). Use of pulmonary vein velocities in conjunction with mitral flow velocities can help in understanding left ventricular filling.

Aged↗
PubMed1989

Significance of Doppler indices of diastolic filling of the left ventricle: comparison with invasive hemodynamics in a canine model.

Doppler measurements of mitral flow velocity curves have been proposed as a method for characterizing diastolic filling of the left ventricle. Different velocity curves have been empirically described in different disease states and under differing loading conditions in humans, but relating these various Doppler parameters to hemodynamic measurements of ventricular diastolic properties has not been fully elucidated. The effect of differing loading conditions (preload reduction, preload increase, afterload increase) on the Doppler mitral flow velocity and high-fidelity left atrial-left ventricular pressures was examined in seven closed-chest, anesthetized dogs. Preload reduction by balloon inflation in the inferior vena cava resulted in significant decreases in E velocity (early diastolic velocity) from 0.39 +/- 0.09 m/sec to 0.29 +/- 0.10 m/sec (p less than 0.01) and prolongation of deceleration time from 131 +/- 18 msec to 165 +/- 60 msec (p less than 0.05). Preload increase by infusion of fluids resulted in a significant increase in E velocity from 0.39 +/- 0.09 m/sec to 0.49 +/- 0.10 m/sec (p less than 0.001) and shortening of the deceleration time from 131 +/- 18 msec to 95 +/- 15 msec (p less than 0.001). The effect of afterload increase was variable and was dependent upon the left atrial pressure. Significant but weak positive correlations were noted between E velocity and maximal left atrial-left ventricular pressure gradient (r = 0.47, p less than 0.001) and total change in left ventricular pressure (r = 0.68, p less than 0.001), with inverse relationships between the deceleration time and these parameters. There was no overall relationship between the time constant tau and the E velocity, but an inverse relationship emerged when the data were examined according to different filling pressures. These results indicate that none of the mitral velocity measurements should be directly equated with other measurements of diastolic function. However, distinct velocity curves emerged under differing loading conditions that help in interpreting the meaning of these curves.

Animals↗