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Biomedical subjects

A Bouchard

Publications and source records attributed to A Bouchard.

At least 37 records · Page 2Linked to original sources
PubMed1989

The value of cine nuclear magnetic resonance imaging for assessing regional ventricular function.

Previous nuclear magnetic resonance (NMR) imaging studies to assess left ventricular function have used multiple axial planes, which are compromised by partial volume effects and are time consuming to acquire and analyze. Accordingly, an imaging approach using cine NMR and planes aligned with the true cardiac axes of the left ventricle was developed in views comparable with left ventricular cineangiography. Cine NMR imaging was used to assess regional wall motion and was validated by comparison with biplane left ventricular cineangiography. Fifty-nine patients underwent cineangiographic and NMR studies within 72 h. A poor quality NMR study precluded analysis in 4. leaving a study group of 55 patients (mean age 58 +/- 12: 17 women). Cine NMR movie loops were acquired in two long-axis planes: 1) right anterior oblique plane, parallel to the septum, and 2) four chamber orthogonal plane, perpendicular to the septum (this view is comparable to the angiographic left anterior oblique view). To assess regional wall motion, the left ventricle in both cine NMR and cineangiographic images was divided into five segments and graded on a five point grading scale from 3 for normal through 0 for akinesia and -1 for dyskinesia. Regional wall thickening was used qualitatively to aid in the analysis of wall motion. For the 275 segments compared in the right anterior oblique view, agreement was within one grade in 263 (95.6%) of 275 segments, whereas absolute agreement was observed in 171 (62%) of 275 segments. In the left anterior oblique view, of 200 segments evaluated, agreement within one grade was achieved in 184 segments (92%) and agreement was complete in 132 (66%).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Noninvasive assessment of cardiomyopathy in normotensive diabetic patients between 20 and 50 years old.

PURPOSE: To further the understanding of diabetic heart disease, we tested the hypothesis that an asymptomatic group of normotensive diabetic patients between 20 and 50 years old had a restrictive cardiomyopathy independent of clinically significant coronary artery disease. PATIENTS AND METHODS: Quantitative two-dimensional echocardiography and stress myocardial perfusion scintigraphy were performed to detect and characterize the cardiac abnormalities in this study group comprising 88 patients with rigorously classified diabetes and 65 volunteer control subjects. RESULTS: Diabetic patients were shown to have a mildly reduced left ventricular end-diastolic volume index: 50.1 +/- 8.2 and 52.1 +/- 14.7 mL/m2 for patients with type I and type II diabetes, respectively, versus 58.9 +/- 11.7 mL/m2 for control subjects. The left ventricular diastolic filling was also impaired in diabetic patients as reflected by a lower atrial emptying index: 0.73 +/- 0.24 and 0.76 +/- 0.3 for type I and type II diabetics, respectively, compared with 1.14 +/- 0.24 for control subjects. Exercise tolerance was normal in subjects with type I diabetes and slightly reduced in subjects with type II diabetes. Only one patient developed regional ischemia on thallium exercise testing. CONCLUSION: Using a comprehensive, noninvasive approach, we have shown that asymptomatic normotensive patients with type I or type II diabetes who were between 20 and 50 years old had a restrictive cardiomyopathy characterized by mildly reduced left ventricular end-diastolic volume and altered left ventricular compliance independent of critical coronary artery disease.

Adult↗
PubMed1988

Hydrodynamics in the heart modulates work.

The hydrostatic pressure (perfusion pressure) of the isovolumic isolated perfused rat heart regulated the hydrodynamics (water movement) of the myocardium. An abrupt (10 s) decrease in hydrostatic pressure caused an immediate decrease in oxygen consumption, left ventricular developed pressure, and wall thickness. Wall thickness was determined by two-dimensional echocardiography. When the perfusion pressure was again returned to the control values (140 cm H2O) oxygen consumption, developed pressure, and wall thickness returned to control values within 10-30 s. An abrupt decrease in perfusion pressure also caused an immediate decrease in both extracellular and intracellular water in the heart as determined by H-1 NMR (nuclear magnetic resonance) with the shift reagent Dy(TTHA)3- (Dysprosium triethylene tetramine-hexaacetate). Similar findings were obtained using K(CoEDTA) (potassium cobalt ethylenediaminetetraacetate) utilized as an extracellular marker. With a decrease in intracellular water in the heart, there was a concurrent decrease in intracellular calcium.

Animals↗
PubMed1988

Cardiac consequences of renal transplantation: changes in left ventricular morphology and function.

To characterize changes in left ventricular morphology and function associated with renal transplantation, noninvasive cardiac evaluations were performed in 41 adults at the time of surgery and at follow-up. At the time of transplantation, 36 patients had undergone hemodialysis through a fistula for 2.3 +/- 2.5 years (mean +/- SD); their hematocrit level was 26 +/- 6% and systolic blood pressure was 151 +/- 19 mm Hg. Perioperatively, left ventricular hypertrophy was present in 93% of patients by echocardiography, but in only 37% by electrocardiography. Abnormal left ventricular diastolic function was present in 67% of patients and indicated a high risk for perioperative pulmonary edema. At follow-up (1.5 +/- 1.4 years), mean hematocrit level increased to 39 +/- 7%, systolic blood pressure decreased to 132 +/- 14 mm Hg and spontaneous closure of the fistula occurred in 13 patients. Left ventricular mass by echocardiography decreased from 237 +/- 66 to 182 +/- 47 g (p less than 0.001), a decrease of 23%. Left ventricular volumes and cardiac index also decreased significantly, reflecting the rapid resolution of a pretransplant high output state. Despite proportionate regression of left ventricular hypertrophy within months of transplantation, diastolic function did not improve. The significant regression of left ventricular hypertrophy that occurs after renal transplantation may help explain the improved cardiovascular survival of patients with a renal transplant over that of patients on long-term dialysis.

Adult↗
PubMed1987

Effects of altered coronary perfusion pressure on function and metabolism of normal and cardiomyopathic hamster hearts.

The effects of a sudden decrease in coronary perfusion pressure from 140 to 0 cmH2O for a 10-second interval were analyzed in normal and cardiomyopathic hamster hearts to determine whether cardiomyopathy would affect the relationship between altered coronary perfusion pressure and left ventricular geometry, wall thickness, myocardial hydrodynamics, and hemodynamics. In normal hamsters, an acute reduction in coronary perfusion pressure resulted in a decrease in left ventricular short axis epicardial cross-sectional area, base to apex length, diastolic wall thickness, myocardial water content and developed pressure. In cardiomyopathic hamsters all results induced by lowering the hydrostatic pressure of the perfusing medium were the same except that diastolic wall thickness failed to decline, indicating a decrease in intramyocardial elasticity in dilated cardiomyopathy. In parallel studies, hearts were freeze clamped at end-diastole and high energy phosphates and energy metabolites analyzed. In both normal and cardiomyopathic hamsters no significant changes were observed in ATP, PCr, or Pi levels at 10 s following the decrease in perfusion pressure. However, during the abrupt decrease in coronary perfusion pressure adenosine increased and cAMP decreased in both groups of animals. The erectile effect of altered coronary perfusion pressure is partially attenuated in the cardiomyopathic hamster in which no change in diastolic wall thickness occurs during an abrupt change in the hydrodynamics of the heart.

Animals↗
PubMed1987

Measurement of left ventricular stroke volume using continuous wave Doppler echocardiography of the ascending aorta and M-mode echocardiography of the aortic valve.

A number of reports have described different Doppler echocardiographic methods to calculate left ventricular stroke volume and cardiac output, but the clinical application of the noninvasive measurements of cardiac function remains in the early stages of development. This slow dissemination may be partly explained by the varying success of these ultrasound methods in determining accurate left ventricular stroke volume. The purpose of this study was to improve the simplicity and accuracy of Doppler stroke volume determination so that it could be more easily applied to patient management. Stroke volume was measured using the product of the integral of aortic velocity obtained by continuous wave Doppler technique and the M-mode tracing of the aortic valve, validating the data against cardiac output obtained by thermodilution technique in 41 patients (r = 0.95, SEE = 7 cc). Intra- and interobserver variability was between 9 and 11%. The results of different sampling sites and the temporal relation between Doppler and thermodilution measurements were also studied. Analysis of 21 patients who had M-mode and two-dimensional echocardiographic studies of the aortic root revealed that the method using M-mode measurement of aortic valve area was most accurate in determining left ventricular stroke volume (r = 0.94, SEE = 10 cc), stroke volume being overestimated when area measurements of the ascending aorta were used. In conclusion, maximal ascending aortic velocity determined by continuous wave Doppler echocardiography with M-mode measurement of aortic valve area can be used to calculate left ventricular stroke volume and cardiac output. The simplicity and practicality of this method should enhance the clinical application of Doppler echocardiography as a noninvasive monitoring technique.

Adult↗
PubMed1986

Left ventricular dimensions and mechanics in distance runners.

We assessed heart size and mechanics at rest in highly trained distance runners. By means of two-dimensional echocardiography, we compared 62 runners (greater than 40 miles/week) and 84 nonrunners. Left ventricular end-diastolic volume index and mass index were larger in runners than in nonrunners (p less than 0.001) and in men than in women (p less than 0.001). However, left ventricular end-diastolic and end-systolic volume/mass ratios were similar for runners and nonrunners. Noninvasive estimates of end-systolic and peak-systolic meridional and circumferential wall stresses were lower in runners than in nonrunners (p less than 0.001). Lower wall stress resulted from lower myocardial area/cavity area ratios, and thus 'average' radius/thickness ratios (measured from the parasternal short-axis view), in runners than in nonrunners (p less than 0.001). We detected a subtle change in ventricular shape among the distance runners. Basilar hypertrophy accounted for increased myocardial thickness with normal cavity size in the parasternal short-axis view, as might be expected in hearts working under sustained pressure elevations during prolonged training periods. However, cavity length and therefore ventricular volume were increased in the apical views, leading to a normal overall volume/mass ratio. These hearts have thus adjusted to periods of volume, as well as to pressure overload. Race performance is determined by a complex interaction between the heart, vascular, and skeletal muscle systems. In this study no parameter of myocardial size or function predicted 10 km or marathon race times, just as no physical characteristic or training record predicted left ventricular mass, end-diastolic or end-systolic volume.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Quantitation of mitral regurgitation by Doppler echocardiography.

The evaluation and care of patients with mitral regurgitation would be facilitated by an easy, reproducible and noninvasive method that could quantitate the hemodynamic burden. In this study, we describe a new Doppler echocardiographic method that measures the regurgitant fraction and we compare it with angiographic and scintigraphic methods. A total of 27 patients with mitral regurgitation were evaluated by echocardiography and either cardiac catheterization or scintigraphy. With two-dimensional echocardiography, diastolic and systolic volumes were measured to derive the left ventricular stroke volume (LVSV). The forward stroke volume (FSV) was obtained from the product of M mode-derived aortic valve area and ascending aortic flow velocity integral assessed by continuous-wave Doppler. Regurgitant fraction was calculated as follows: (LVSV - FSV)/LVSV. Comparisons showed that regurgitant fraction calculated by Doppler echocardiography correlated with regurgitant fraction determined by both cardiac catheterization (r = .82) and by scintigraphy (r = .89). There was, however, an important interobserver variability within each method: 10%, 13%, and 11% for Doppler echocardiography, angiography, and scintigraphy, respectively. In conclusion, Doppler echocardiography can be used to quantitate mitral regurgitation. Serial noninvasive determinations of regurgitant fraction may be useful in the evaluation of therapy and in the follow-up of patients with mitral insufficiency.

Adult↗
PubMed1985

Magnetic resonance imaging in pulmonary arterial hypertension.

Magnetic resonance imaging (MRI) was used to examine the right ventricle and pulmonary arteries in 17 patients with pulmonary artery (PA) hypertension documented by cardiac catheterization. The study population consisted of 7 patients with primary pulmonary hypertension, 7 with Eisenmenger's syndrome and 3 with pulmonary hypertension secondary to lung disease. The MRI studies of patients were compared with those of 10 normal volunteers. Multislice gated transaxial images encompassed the right ventricle and central pulmonary arteries, showing the severity of right ventricular (RV) hypertrophy in proportion to the elevation of PA pressure and reversal of septal curvature when PA pressure approximated systemic pressure. End-diastolic RV wall thickness and mean pulmonary pressure correlated well (r = 0.79). MRI showed enlargement of PAs in all patients with PA hypertension. A magnetic resonance signal was present in the PAs throughout the cardiac cycle in patients with severe PA hypertension (more than 90 mm Hg) and was absent during systole in normal subjects. A signal within the PAs in systole is consistent with decreased flow velocity in patients with severe PA hypertension. MRI was useful in detecting each of the congenital anatomic defects in patients with Eisenmenger's syndrome. This study indicates the potential of MRI for evaluating the severity of PA hypertension by providing direct measurements of RV wall thickness and PA diameter and by detecting abnormal intraluminal signal intensity during the cardiac cycle.

Adolescent↗
PubMed1985

Comparison of clinical variables and variables derived from a limited predischarge exercise test as predictors of early and late mortality after myocardial infarction.

An exercise test limited to 5 METS or 70% of age-predicted maximal heart rate was performed 1 day before hospital discharge by 225 survivors of acute myocardial infarction, all of whom were subsequently followed up for at least 5 years. The mortality rate was 11.1% during the first year, but averaged only 2.9% per year from the second to fifth year. Over the entire follow-up period, the five variables that predicted mortality by multivariate analysis were QRS score, an exercise-induced ST segment shift, previous infarction, failure to achieve target heart rate or work load and ventricular arrhythmia during the exercise test. Because mortality differed markedly before and after 1 year, Cox regression analyses were performed separately for both of these periods. The factors that were predictive of mortality during the first year were an exercise-induced ST shift (p less than 0.0001, relative risk 7.8), failure to increase systolic blood pressure by 10 mm Hg or more during exercise (p = 0.0039, relative risk 4.3) and angina in hospital 48 hours or longer after admission (p = 0.0046, relative risk 3.4). None of these three variables was predictive of mortality after 1 year. Previous infarction (p = 0.0007), QRS score (p = 0.0042) and ventricular arrhythmia during the exercise test (p = 0.016) were predictive of mortality after the first year. Thus, clinical and exercise test variables are complementary predictors of mortality after myocardial infarction. An abnormal ST segment response during an early limited exercise test and angina in the hospital are common strong predictors of mortality to 1 year, but not thereafter. Late mortality correlates with markers of poor left ventricular function.

Adult↗
PubMed1985

Left ventricular mass and volume/mass ratio determined by two-dimensional echocardiography in normal adults.

This study prospectively defined the range of left ventricular mass and volume/mass ratio determined by two-dimensional echocardiography in 84 normal adults. A modified Simpson's rule algorithm was used to calculate ventricular volumes from orthogonal two and four chamber apical views. An algorithm based on a model of the left ventricle as a truncated ellipsoid was used to calculate ventricular mass. Like left ventricular volumes, left ventricular mass values were larger in normal men than in women (mean 148 versus 108 g, p less than 0.001) and remained larger after correction for body surface area. Volume/mass ratios, however, were constant at end-diastole (0.80) and end-systole (0.26). The influence of age and heart rate on all variables in this normal group was minimal, and no correction for these variables was necessary. The definition of normal mass, volume and volume/mass ratios by two-dimensional echocardiography will facilitate the noninvasive, quantitative diagnosis of left ventricular hypertrophy and help clarify the relation between hypertrophy and systolic wall stress.

Adult↗
PubMed1985

Regional myocardial dysfunction: evaluation of patients with prior myocardial infarction with fast CT.

A prototype ultrafast cine computed tomographic (CT) scanner, designed specifically for cardiac imaging, was used to evaluate a preliminary series of patients with prior myocardial infarction (n = 21) and a control group without coronary artery disease (n = 5). Multilevel 50-msec CT scan exposures were obtained during peripheral intravenous bolus injections of contrast medium. A comparison was made between cine-CT scans and standard left ventriculographic images in assessing segmental left ventricular motion. Results indicate that cine CT, performed at sufficiently rapid speeds (20 scans per second) to allow useful analysis of regional ventricular wall motion, can provide adequate image quality. Analysis of 110 segments revealed a good correlation (90.9%) between the two techniques in characterizing normal from abnormal regional wall motion. Cine CT, based on this initial study, demonstrates considerable potential for evaluating not only cardiac chamber dimensions but also segmental wall dynamics.

Adult↗
PubMed1985

Intraoperative detection of myocardial ischemia in high-risk patients: electrocardiography versus two-dimensional transesophageal echocardiography.

Because acute segmental wall motion abnormalities (SWMAs) of the left ventricle are highly sensitive and specific indicators of myocardial ischemia, this study compared the incidence and significance of ischemia, as detected by two-dimensional transesophageal echocardiography and surface electrocardiography, during anesthesia and surgery in patients at high risk of myocardial ischemia. During surgery, 24 of the 50 patients studied had new SWMAs, whereas only six had ST segment changes. All patients with ST segment changes also had new SWMAs: in three instances, SWMAs occurred before the ST segment change, and in three instances, they occurred simultaneously. All three patients who had intraoperative myocardial infarctions also had persistent intraoperative SWMAs, whereas only one patient had ST segment changes. Ten healthy patients requiring noncardiovascular surgery were monitored similarly; none of these had SWMAs, ST segment changes, or myocardial infarction. This study demonstrates the superiority of two-dimensional transesophageal echocardiography over electrocardiography for the intraoperative detection of myocardial ischemia. Furthermore, when new SWMAs persist to the conclusion of surgery, myocardial infarction is likely to have occurred.

Echocardiography↗
PubMed1984

Circadian variation in variant angina.

Thirteen hospitalized patients with variant angina were studied to assess circadian variation in disease activity. Over 48 hours, all angina attacks were noted, a continuous Holter electrocardiogram was recorded and 2 ergonovine tests were performed 12 hours apart, 1 at 4 AM and the other at 4 PM. Only 2 patients gave a clearcut history of more frequent nocturnal or early morning attacks. During the study period, 1.8 +/- 1.6 AM and 0.62 +/- 1.2 PM angina episodes per patient were reported (p less than 0.02), but a circadian pattern was apparent in only 4 patients. However, Holter analysis revealed 5.3 +/- 13.8 AM and 2.6 +/- 8.5 PM episodes of ST elevation per patient (p less than 0.05) and 8.1 +/- 13.9 AM and 3.2 +/- 8.5 PM episodes of ST elevation, ST depression or T-wave pseudonormalization (p less than 0.01). Ten of 11 patients with Holter abnormalities had more frequent AM than PM attacks (p less than 0.01). ST elevation developed during all 13 of the 4-AM and 12 of 13 of the 4-PM ergonovine tests. In 10 cases the ergonovine threshold at which the attack occurred was lower in the morning, in no case was it lower in the afternoon, and in 3 patients the morning and afternoon doses were identical (p less than 0.01). Thus, circadian variation in disease activity both for spontaneous and provoked attacks is present in most patients with variant angina, even though it is often not clinically apparent.

Adult↗
PubMed1984

Exercise testing in the early period after myocardial infarction in the evaluation of prognosis.

Prognosis for the patient recovery from an acute myocardial infarction is related mainly to electrical instability, left ventricular function, residual ischemia, and extent of coronary atherosclerosis. Many procedures now exist that allow investigation of these various aspects of cardiovascular function and stratification of risk. No ideal marker of prognosis exists because prognosis is not related to a single factor, because the various determinants are often interdependent, and also because they are time dependent. Thus, the presence of ischemia may be particularly important in the first year when the risk is greater, whereas left ventricular function may be the most important factor thereafter. For this reason, an active strategy for detecting ischemia, by exercise testing or other means, may add to clinical observation. Exercise testing is a safe and noninvasive method that can provide information not only on residual ischemia but also on other aspects of cardiovascular function. Many parameters can be studied, such as ST segment elevation or depression, chest pain, ventricular arrhythmias, tolerance to exercise, completion or not of the test, and the heart rate and blood pressure responses. Some of these data are not specific and must be complemented by further investigation. Such as approach should allow an overall evaluation of the cardiovascular function of the patient and an assessment of risk, and help institute an optimal treatment.

Angina Pectoris↗
PubMed1983

Spontaneous remission is a frequent outcome of variant angina.

To assess the prevalence of spontaneous remission in variant angina, 100 patients with this diagnosis who had undergone coronary arteriography in the hospital and a follow-up of at least 1 year were studied. Patients with coronary bypass surgery or myocardial infarction were excluded. Remission was diagnosed in 45 of the 100 patients who had been angina-free and had had no treatment for more than 3 months (mean 18.3). The other 55 patients were receiving medical treatment; 37 had been angina-free for at least 6 months (mean 22.5) and angina persisted in 18. The persistent angina group had a lower prevalence of organic coronary stenoses 70% or greater: 4 of 18 versus 22 of 45 and 22 of 37 for the other two groups (p less than 0.05), and a longer history of rest angina before admission. The remission group contained more patients (17 of 45 versus 4 of 55 [p less than 0.001]) whose attacks had been documented only by provocative testing. Rest angina recurred when calcium antagonist drugs were discontinued in 15 of 51 instances, within 1 month in 11 patients and later in 4 patients. Remission was eventually attained in 35 of the 38 patients in whom these drugs were stopped. These results indicate that remission is a frequent outcome of variant angina. This fact should be considered in the evaluation of the long-term results of treatment and in the planning of care for an individual patient.

Adult↗
PubMed1983

Factors influencing the long-term prognosis of treated patients with variant angina.

To determine the prognosis of variant angina and the factors influencing it, 169 consecutive patients hospitalized in our coronary unit were followed for a mean of 15.3 months (range 1 to 68). Survival at 1, 2, and 3 years was 95%, 90%, and 87%, respectively; survival without myocardial infarction was 80%, 78%, and 75%. Twenty of the 22 myocardial infarctions and eight of the 14 deaths occurred within the first 3 months. Mantel-Haenszel log-rank analysis demonstrated that coronary disease, ventricular function, and the degree of disease activity were significant interdependent variables that influenced both survival and survival without infarction. At 1, 2, and 3 years, survival for patients with multivessel disease was 81%, 76%, and 66%; for patients with one-vessel disease, 97%, 92%, and 92%; and for patients without stenoses greater than or equal to 70%, 98% at each year (p = .0003). Survival without infarction at 1 year was 88% in patients with no stenoses greater than or equal to 70% and 82% in patients with single-vessel disease; it did not change thereafter in either group, but was 62%, 58%, and 50% at 1, 2, and 3 years in patients with multivessel disease (p = .001). Treatment did not influence survival in any subgroup (only 14 patients died overall) or survival without infarction in patients with multivessel disease. However, in patients without multivessel disease, treatment with nifedipine, diltiazem, and verapamil improved survival without infarction compared to treatment with perhexiline maleate or long-acting nitrates alone (92% vs 67% at 1, 2, and 3 years; p less than .005). Thus in addition to preventing angina, nifedipine, diltiazem, and verapamil appear to reduce complications in patients with variant angina without multivessel disease.

Adult↗