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Biomedical subjects

N Reichek

Publications and source records attributed to N Reichek.

At least 91 records · Page 5Linked to original sources
PubMed1987

Early postoperative changes in left ventricular chamber size, architecture, and function in aortic stenosis and aortic regurgitation and their relation to intraoperative changes in afterload: a prospective two-dimensional echocardiographic study.

We prospectively studied 16 patients with isolated aortic stenosis and eight with isolated aortic regurgitation undergoing aortic valve replacement, using two-dimensional echocardiography preoperatively, intraoperatively, and 41 +/- 7 days postoperatively to calculate the intraoperative change in afterload, quantify the postoperative changes in left ventricular chamber size, architecture, load and function, determine whether the postoperative left ventricular remodeling correlated with the intraoperative change in afterload in aortic stenosis and aortic regurgitation, and assess whether preoperative afterload excess precluded postoperative improvement in left ventricular function. Preoperative left ventricular mass, end-systolic meridional and circumferential wall stresses, ejection fraction, and stress-shortening relations in patients with aortic stenosis and aortic regurgitation were similar. However, our patients with aortic regurgitation had severe systolic dysfunction, with ejection fraction less than 55% in all but one patient, compared with only 10 of 16 patients with aortic stenosis. Left ventricular end-diastolic volume, mass/volume ratio, and chamber shape were significantly different in patients with aortic stenosis and aortic regurgitation (174 +/- 64 vs 294 +/- 140 ml, p less than .01; 1.81 +/- 0.63 vs 1.14 +/- 0.18, p less than .01; and 0.59 +/- 0.09 vs 0.69 +/- 0.09, p less than .05, respectively). Intraoperative end-systolic meridional and circumferential stresses fell significantly in patients with aortic stenosis but remained unchanged in those with aortic regurgitation. The changes in left ventricular volume and ejection fraction during early postoperative remodeling (6 weeks) correlated with the intraoperative change in afterload in patients with aortic stenosis. In contrast, there was no intraoperative change in afterload in patients with aortic regurgitation and no significant changes in left ventricular volume, architecture, or function at 6 weeks or at 6 months. The differences in left ventricular remodeling and changes in function between patients with aortic stenosis and aortic regurgitation in the early postoperative period most probably relates to the major difference in intraoperative reduction in afterload, although a contributory role may have been played by the preoperative left ventricular dysfunction in those with aortic regurgitation that was underestimated by measurement of ejection fraction.

Adult↗
PubMed1987

Cardiac fatigue after prolonged exercise.

To determine the effects of prolonged exercise on systolic and diastolic left ventricular function, we studied 21 athletes before, at the finish (within 11 +/- 5 min), and during recovery (28 +/- 9 hr) after the Hawaii Ironman Triathlon (2.4 mile swim, 112 mile bike, 26.2 mile run). Two-dimensionally guided M mode echocardiograms were digitized for wall thickness, cavity dimension, fractional shortening, and peak rates of cavity enlargement and wall thinning. Pulsed Doppler left ventricular inflow recordings were analyzed for peak early and late velocities and their ratio. Left ventricular diastolic dimension was reduced at race finish (5.4 +/- 0.6 to 5.1 +/- 0.6 cm) and remained reduced after 1 day of recovery (5.2 +/- 0.6 cm, p less than .05). Fractional shortening fell at race finish (39 +/- 5% to 35 +/- 5%), although systolic blood pressure was unchanged, and rose to 40 +/- 4% after recovery (p less than .05). The return to prerace shortening values after recovery occurred despite continued reduction in diastolic size. Peak circumferential shortening did not change significantly. Individual reductions in fractional shortening were correlated with increases in systolic cavity size (r = -.64, p less than .01), but not with decreases in diastolic size. The stress-shortening relationship was displaced downward at race finish, but returned toward baseline after 1 day of recovery, despite a persistent reduction in cavity size. This suggests that the decrease in shortening was due to impaired contractility as well as altered preload.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Standardization in the measurement of left ventricular wall mass. M-mode echocardiography.

A wide variety of approaches to M-mode echocardiographic methods for estimation of left ventricular mass have been proposed and employed in hypertensive heart disease. The cube function geometry, which assumes an ellipsoid of revolution with a length twice the minor axis, appears to be optimal provided left ventricular shape is relatively normal. The Penn measurement technique for wall thickness and diameter is best validated, but American Society of Echocardiography measurements can be used with appropriate regression correction. Changes in instrumentation may warrant reexamination of measurement techniques as well as the relative value of M-mode and two-dimensional echocardiographic techniques for estimation of left ventricular mass.

Cardiac Volume↗
PubMed1987

Standardization in the measurement of left ventricular wall mass. Two-dimensional echocardiography.

Two-dimensional echocardiography is superior to M-mode echocardiography for estimation of left ventricular mass when left ventricular shape is markedly abnormal. Left ventricular mass measurement by two-dimensional echocardiography depends on careful experimental calibration of the echocardiographic instrument using either a standard phantom or actual heart slices, and appropriate geometric algorithm, and short axis images to determine myocardial cross-sectional area. Several well-validated algorithms are available, of which the short-axis area-length technique is the simplest. In hypertensive heart disease, in which left ventricular shape is usually close to normal, two-dimensional echocardiography may offer a smaller standard error than M-mode, but this issue requires further evaluation. Further, it is uncertain whether the incremental accuracy of two-dimensional echocardiography in hypertensive heart disease would offset its increased cost and complexity relative to M-mode echocardiography.

Echocardiography↗
PubMed1986

Left ventricular structure and function by echocardiography in ultraendurance athletes.

To determine left ventricular (LV) structural and functional changes induced by ultraendurance exercise training, M-mode LV echograms and Doppler recordings of LV inflow velocity in 26 triathletes and 17 normal subjects were studied. All triathletes trained 20 to 40 hours/week in swimming, cycling and running for more than 2 years. Structurally, triathletes had normal LV systolic and diastolic cavity dimensions, but increased wall thickness (1.05 +/- 0.26 vs 0.80 +/- 0.27 cm in normal subjects, p less than 0.001), increased relative wall thickness, or h/R ratio (0.41 +/- 0.10 cm vs 0.33 +/- 0.11 cm in normal subjects, p less than 0.001), and increased LV mass (226 +/- 60 vs 143 +/- 54 g in normal subjects, p less than 0.001). LV mass correlated closely with mean exercise blood pressure during an 8-hour exercise test in 14 triathletes (r = 0.88). Systolic function at rest was similar in both groups, with no differences in fractional shortening or end-systolic stress. Diastolic LV function measured by digitized M-mode echo was similar in normal subjects and triathletes, with no differences in peak rates of cavity enlargement and wall thinning by echocardiogram. In contrast, the Doppler-derived ratio of early-to-late LV inflow velocities was slightly increased in triathletes (p less than 0.05). It is concluded that ultraendurance training produces a physiologic pattern of moderate pressure overload LV hypertrophy, in proportion to the hemodynamic load imposed during prolonged exercise. Unlike the abnormal hypertrophy of systemic hypertension, early diastolic function remains normal in the triathlete heart.

Adult↗
PubMed1986

Effects of six-month afterload reduction therapy with hydralazine in chronic aortic regurgitation.

Seventeen patients with chronic asymptomatic aortic regurgitation (AR) were studied to determine whether 6 months of hydralazine therapy can reduce the severity of AR or reverse left ventricular (LV) enlargement and hypertrophy. Echocardiography, radionuclide angiography at rest and during exercise, and maximal treadmill exercise with respiratory gas analysis were performed at intake and after a 6-month double-blind treatment period. After dose titration with hydralazine, patients were randomized to their maximal tolerated hydralazine dose or to placebo. At intake, hydralazine and placebo groups were similar. Six patients taking hydralazine and 8 taking placebo completed the study protocol. One patient taking placebo died and 2 patients taking hydralazine withdrew with drug-related adverse effects. The mean titrated dose of hydralazine was 96 +/- 9 mg, but the mean treatment dose was 63 +/- 21 mg administered 3 times daily because of drug intolerance. After 6 months, mean systolic blood pressure with hydralazine therapy decreased from 136 to 125 mm Hg (p less than 0.02), and end-systolic posterior wall thickness increased from 1.58 to 1.70 cm (p less than 0.05), resulting in a significant reduction in M-mode meridional end-systolic stress (from 104 to 80 kdynes/cm2) (p less than 0.05). M-mode fractional shortening increased from 0.28 to 0.31 (p less than 0.05) with hydralazine, but mean LV echocardiographic dimensions were unchanged. LV mass increased from 383 to 434 g (p less than 0.05) with hydralazine primarily because of an increase in end-diastolic wall thickness. In the placebo group, there was no change in any of the hemodynamic or echocardiographic parameters at 6 months.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Echocardiographic assessment of left ventricular hypertrophy: comparison to necropsy findings.

To determine the accuracy of echocardiographic left ventricular (LV) dimension and mass measurements for detection and quantification of LV hypertrophy, results of blindly read antemortem echocardiograms were compared with LV mass measurements made at necropsy in 55 patients. LV mass was calculated using M-mode LV measurements by Penn and American Society of Echocardiography (ASE) conventions and cube function and volume correction formulas in 52 patients. Penn-cube LV mass correlated closely with necropsy LV mass (r = 0.92, p less than 0.001) and overestimated it by only 6%; sensitivity in 18 patients with LV hypertrophy (necropsy LV mass more than 215 g) was 100% (18 of 18 patients) and specificity was 86% (29 of 34 patients). ASE-cube LV mass correlated similarly to necropsy LV mass (r = 0.90, p less than 0.001), but systematically overestimated it (by a mean of 25%); the overestimation could be corrected by the equation: LV mass = 0.80 (ASE-cube LV mass) + 0.6 g. Use of ASE measurements in the volume correction formula systematically underestimated necropsy LV mass (by a mean of 30%). In a subset of 9 patients, 3 of whom had technically inadequate M-mode echocardiograms, 2-dimensional echocardiographic (echo) LV mass by 2 methods was also significantly related to necropsy LV mass (r = 0.68, p less than 0.05 and r = 0.82, p less than 0.01). Among other indexes of LV anatomy, only measurement of myocardial cross-sectional area was acceptably accurate for quantitation of LV mass (r = 0.80, p less than 0.001) or diagnosis of LV hypertrophy (sensitivity = 72%, specificity = 94%).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Intraoperative assessment of left ventricular heterogeneity.

To evaluate regional differences in thickness and systolic function of human myocardium perfused by angiographically normal coronary arteries in valvular and ischemic heart disease, we performed intraoperative epicardial M-mode mapping of ventriculographically normal wall regions (perfused by normal coronary arteries) in 22 subjects undergoing either coronary bypass surgery for stenoses in other vessels (n = 15) or mitral (n = 5) and/or aortic valve replacement (n = 4). In patients in whom both anterior and inferior walls were ventriculographically normal and normally perfused (n = 6), comparison of the two walls showed the anterior wall to be thicker at both end diastole and end systole, but there was no difference in the percentage of systolic thickening. Analysis of myocardium along the long axis revealed apical sites to be thinner than basal sites at both end diastole and end systole. Percentage of systolic thickening was also increased at apical sites. In patients in whom only the anterior wall was normal, a similar decrease in anterior wall thickness was noted at the apex. Thus systematic regional heterogeneity along both the left ventricular major and minor axes is found in the chronically diseased human heart as it is in the normal heart. Assessment of myocardial structure and function and of the effects of therapeutic interventions must take this heterogeneity into account.

Coronary Artery Bypass↗
PubMed1986

Effects of nitroglycerin in patients with angina, normal coronary arteries, and left ventricular hypertrophy.

The coronary hemodynamic and left ventricular mechanical responses to nitroglycerin were studied in eight patients with angina, normal coronary arteries, and pressure overload left ventricular hypertrophy (POLVH) and in five control subjects. Elevated mean and end-diastolic pressure and end-diastolic meridional stress characterized the POLVH group, although systolic meridional stresses were not significantly different from the control group. Thermodilution coronary sinus flow and estimated myocardial oxygen consumption declined significantly following nitroglycerin in both patient groups. Systolic and diastolic mechanical loads also decreased in both groups, although diastolic tone remained elevated in the patients with POLVH. The decrease in coronary sinus flow in the POLVH group was in excess of that expected from the decrease in systolic mechanical load, which suggests a combination of perfusion pressure-dependent decreases in coronary flow as well as an increased resistance to coronary inflow in these patients. The beneficial clinical response to nitroglycerin may reflect the lowered myocardial metabolic demand as well as the decrease in diastolic myocardial tensile and compressive forces.

Adult↗
PubMed1986

Dynamic three-dimensional reconstruction of the left ventricle from two-dimensional echocardiograms.

Using an open chest canine model, a method was developed for three-dimensional reconstruction of the contracting left ventricle from two-dimensional echocardiograms, which is applicable to intraoperative studies in humans. A mechanically held 5 MHz transducer was used to record parallel high resolution cross-sectional images with precise spatial registration. Myocardial borders were tracked manually and entered into a computer system. Regional filling and interpolation routines were applied to reconstruct the endocardial and epicardial surfaces of the ventricle. The myocardium can be displayed as a translucent, shaded three-dimensional solid surrounding the ventricular cavity. One or both surfaces can be rotated about any axis, sectioned through any plane and viewed in motion through systole and diastole. Studies before and after left anterior descending coronary artery occlusion showed the three-dimensional extent of abnormal left ventricular cavity and myocardial deformation. Quantitative examination of regions of interest permits the analysis of global and regional volumetric and myocardial thickness changes throughout the cardiac cycle. Thus, open chest three-dimensional echocardiography provides a powerful tool for the quantitative physiologic investigation of the left ventricle.

Animals↗
PubMed1986

An unusual case of postoperative pseudoaneurysm of the left ventricle: Doppler echocardiographic findings.

Two years and 9 months after aneurysmectomy of a true left ventricular aneurysm, a 55 year old man presented with clinical features suggestive of acute pericarditis. The echocardiogram revealed a large echo-free space outside the heart. Doppler study showed phasic flow between the echo-free space and the left ventricular cavity through a distinct interruption of the left ventricular apical wall endocardial echoes. The diagnosis of pseudoaneurysm was made and was subsequently confirmed by angiographic and operative findings. After successful repair, a repeat Doppler echocardiographic examination showed a marked reduction in the echo-free space, absence of communication with the left ventricle and no flow signal in the space.

Coronary Angiography↗
PubMed1986

Estimation of wall stress and left ventricular mass by noninvasive techniques and clinical implications.

Left ventricular mass and wall stress are easily calculated using routinely available imaging modalities. Consideration of these parameters provides important contributions to the evaluation and treatment of many forms of heart disease. The newer techniques of computed tomography and magnetic resonance imaging hold great potential for increasing both the accuracy and the ease of mass and stress determinations.

Algorithms↗
PubMed1985

Relative wall thickness analysis by two-dimensional echocardiography.

M-mode echocardiographic relative wall thickness (RWT) has been used extensively as an index of left ventricular hypertrophy. To determine whether the more extensive tomographic sampling and enhanced spatial orientation provided by two-dimensional echocardiography (2DE) might improve the value of RWT analysis, we compared 2DE and M-mode RWT in 69 subjects (19 normals, 13 with aortic stenosis, 22 with aortic regurgitation, and 15 with congestive cardiomyopathy). M-mode results correlated relatively weakly with 2DE RWT (r = 0.62 at end diastole; r = 0.81 at end systole). End-systolic M-mode values were larger than 2DE results, while end-diastolic M-mode values were generally smaller than 2DE results (both p less than 0.001). Thus, in congestive cardiomyopathy M-mode RWT was larger than 2DE end-diastolic results and therefore failed to distinguish between cardiomyopathy, aortic regurgitation, and normals. We conclude that M-mode and 2DE analysis of RWT yield disparate results. Moreover, 2DE may enhance the value of RWT in the assessment of left ventricular hypertrophy due to volume overload and cardiomyopathy.

Adolescent↗
PubMed1985

Effects of reduced left ventricular mass on chamber architecture, load, and function: a study of anorexia nervosa.

We investigated the effects of reduction in left ventricular mass on cavity geometry, afterload, pump function, and exercise performance in 17 patients with anorexia nervosa and in 10 age-and sex-matched normal subjects. Left ventricular mass index determined by two-dimensional echo-cardiography was significantly lower than that in normal subjects (53 +/- 15 vs 79 +/- 18 g/m2; p less than .005). Left ventricular end-diastolic and end-systolic volume indexes were also reduced in patients with anorexia nervosa compared with normal subjects (49 +/- 11 vs 65 +/- 17 ml/m2, p less than .005; 14 +/- 5 vs 19 +/- 4 ml/m2, p less than .025). In spite of the reductions in left ventricular mass and volume indexes, left ventricular chamber architecture described as h/R ratio, mass to volume ratio, and short/long left ventricular axis ratio were normal. Left ventricular afterload assessed as end-systolic meridional and circumferential wall stress was normal (59 +/- 18 vs 79 +/- 19 dyne/cm2 X 10(3) and 170 +/- 26 vs 167 +/- 23 dyne/cm2 X 10(3)). Ejection fraction, percent fractional shortening, and the relationship between end-systolic wall stress and ejection fraction were all within normal limits. In seven patients restudied after a 15% to 20% weight gain, left ventricular mass and volume indexes increased significantly but end-systolic wall stress and ejection fraction did not change. Ten patients with anorexia nervosa and resting heart rates and systolic blood pressures significantly lower than control values underwent treadmill testing. Exercise duration, peak heart rate, peak systolic blood pressure, and peak oxygen consumption in these patients were all significantly lower than normal. The hypotensive effect of fasting resulted in an initial decrease in afterload, which was the stimulus for reduction in left ventricular mass. The left ventricular remodeling associated with the mass reduction occurred in such a way that (1) orthogonal, meridional, and circumferential wall stresses were normalized, (2) normal chamber shape and architecture were maintained, and (3) chamber function and stress-shortening relationships were preserved. Thus down-regulation of left ventricular mass per se, like up-regulation of left ventricular mass, is not associated with abnormal left ventricular function.

Adolescent↗
PubMed1984

Left ventricular mechanics in dilated cardiomyopathy.

The influence of altered chamber shape on the evaluation of left ventricular (LV) mechanics in idiopathic dilated cardiomyopathy (IDC) is unknown. Nine patients with IDC and 7 subjects with normal LV function were studied with simultaneous LV pressure and M-mode echographic recordings in order to derive LV meridional wall stress. The major axis of the left ventricle, determined from the left ventriculogram at rest, allowed for derivation of circumferential wall stress. The IDC group was characterized by larger end-diastolic and end-systolic LV volumes, increased LV mass, depressed angiographic ejection fraction and more spherical LV chamber shape. Both end-systolic meridional (114 +/- 30 kdyne/cm2) and circumferential (251 +/- 73 kdyne/cm2) wall stresses were elevated in patients with IDC, although the ratio of these stresses was less than normal (2.2 +/- 0.1 vs 2.7 +/- 0.2, respectively). LV load alteration with phenylephrine or nitroglycerin allowed for construction of end-systolic stress-minor-axis dimension and end-systolic stress-minor-axis shortening relations. Similar mean slopes of the meridional end-systolic stress-dimension relation were noted in IDC and normal subjects, although the line was displaced to the right in IDC. The slope of the circumferential end-systolic stress-dimension relation was, however, decreased in patients with IDC. Moreover, the end-systolic stress-fractional minor-axis shortening relation in patients with IDC was displaced downward from the normal relation supporting depressed contractile function in these IDC patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1984

Antianginal effects of nitroglycerin patches.

Nitroglycerin (NTG) patches provide potentially therapeutic NTG blood levels for 24 hours, but their effects on exercise tolerance (ExT) in patients with angina have not been well characterized. Therefore, blinded, randomized trials were performed of the acute effects of both low-dose and maximal-tolerated-dose NTG patches and placebo on ExT in 14 patients with coronary artery disease and typical exertional angina. The bicycle exercise protocol of the National Institutes of Health was used and sublingual NTG administered as a positive control. In 7 subjects, low-dose patches produced no statistically significant effect on ExT at 4, 8 or 24 hours after administration. Comparable doses of sublingual and oral isosorbide dinitrate, NTG ointment and transmucosal NTG in previous studies have produced effects similar to those of conventional doses of sublingual NTG. Maximally tolerated doses of 2 types of NTG patches were then tested. The first (n = 8, mean NTG dose delivered 25 mg) produced increases in ExT of 82 and 72 seconds at 4 and 8 hours, respectively (both p less than 0.01), but was ineffective at 24 hours. The second patch type (n = 5, mean NTG dose delivered 22 mg) was also ineffective at 24 hours. Furthermore, even at maximal doses, peak effects on ExT were about half of those of sublingual NTG. Thus, NTG patches, even at maximal doses, appear to have smaller therapeutic effects than other long-acting nitrates and are ineffective at 24 hours. These results suggest rapid attenuation of NTG effect during prolonged maintenance of constant blood levels.

Administration, Topical↗
PubMed1984

Long-acting nitrates: relative utility of nitroglycerin patches.

Cutaneous nitroglycerin patches offer an attractive, convenient approach to antianginal prophylaxis with nitroglycerin. Blood level data have suggested that nitroglycerin patches could have antianginal effects for 24 hours or more. However, direct documentation of antianginal efficacy is fragmentary at present. Existing studies using provocative exercise testing, with one exception, do not demonstrate antianginal effects of nitroglycerin patches at 24 hours, using either low or maximal tolerated doses in each subject. Furthermore, in contrast to other long-acting nitrates evaluated in similar fashion, the peak effects of nitroglycerin patches may not be as potent as those of sublingual nitroglycerin. Thus, at present, clinicians should not assume that nitroglycerin patches can provide 24-hour prophylaxis. Further, in patients on a patch regimen with continuing symptoms, consideration should be given to a trial of alternative or additional long-acting nitrates of other types.

Administration, Topical↗