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Biomedical subjects

N Reichek

Publications and source records attributed to N Reichek.

At least 145 records · Page 8Linked to original sources
PubMed1979

Nifedipine in the treatment of Prinzmetal's (variant) angina.

The clinical response to therapy with the calcium-blocking agent nifedipine was assessed in 12 patients with variant angina pectoris who were 44 to 67 years old. Five patients had vasospasm of the left anterior descending coronary artery, and seven had spasm of a dominant right coronary artery. Before nifedipine therapy, the frequency of anginal attacks per 24 hour period ranged from 1 to 12, with ventricular tachycardia accompanying ischemic episodes in 7 of 12 patients and high grade atrioventricular block occurring in 2 patients. After therapy with nifedipine, 11 of 12 patients had initial relief of symptoms, and 7 of the 11 had long-term relief. Withdrawal of nifedipine led to recurrence of angina on six occasions in four patients. Provocative testing in the cardiac catheterization laboratory by means of the cold pressor test in one patient and ergonovine maleate in another before and after nifedipine administration showed that this agent can block both alpha adrenergic- and regonovine-induced vasospasm. Nifedipine may have a significant role in the therapy of angina caused by coronary spasm.

Adult↗
PubMed1979

Echocardiographic indices of left ventricular function. A comparison.

Multiple M-mode echocardiographic indices of left ventricular function are currently in use, but their reliability is disputed. Therefore, we correlated echo ejection fraction (EF) using quadratic (Q) and cubic (C) formulae, percentage of minor axis shortening (%S), mean velocity of circumferential fiber shortening (mVCF), and peak VCF with angiographic EF in 37 subjects, including 10 normal subjects. None had echocardiographic segmental wall motion abnormalities. Significant linear correlations were found between angiographic EF and EFc (r = 0.78), %S (r = 0.77), EFQ(r = 0.68), peak VCF (r = 0.68), and mVCF (r = 0.58). However, for all indices, the scatter was too great to permit reliable quantitative estimations of angiographic EF based on echo date. Peak VCF was qualitatively the most reliable predictor of ventricular function, being greater than or equal to 2.00 circumference per second in 23 of 25 patients with angio EF greater than or equal to 55 percent and less than 2.00 circumferences per second in 11 of 12 with EF less than 55 (sensitivity [sens] 92 percent, specificity [spec] 92 percent). Mean VCF (sens 83 percent, spec 80 percent), %S (sens 50 percent, spec 96 percent), EFC (senc 58 percent, spec 96 percent), and EFQ (sens 58 percent, spec 92 percent) were less satisfactory. We conclude that echo indices are reliable only as qualitative parameters of ventricular function. Peak VCF appears to be the most sensitive and specific qualitative index now available.

Cineangiography↗
PubMed1977

Echocardiographic determination of left ventricular mass in man. Anatomic validation of the method.

An accurte echocardiographic (E) method for determination of left ventricular mass (LVM) was derived from systematic analysis of the relationship between the antemortem left ventricular echogram and postmortem anatomic LVM in 34 adults with a wide range of anatomic LVM (101-505 g). No subject had massive myocardial infarction, ventricular aneurysm, severe right ventricular volume overload or hypertrophic cardiography. The best method for LVM-E identified combined cube function geometry with a modified convention for determination of left ventricular internal dimension (LVID), posterior wall thickness (PWT), and interventricular septal thickness (IVST), which excluded the thickness of endocardial echo lines from wall thicknesses and included the thickness of left septal and posterior wall endocardial echo lines in LVID (Penn Convention, P). By this method, anatomic LVM = 1.04 ([LVIDp + PWTp + IVSTp]3--[LVIDp]3) -- 14 g; r = 0.96, SD= 29 g, N= 34. Standard echo measurements gave less accurate results, as did previously reported methods for LVM-E. LVM-Dp is an accurate, widely applicable method for the study of left ventricular hypertrophy.

Adult↗
PubMed1976

Mitral valve prolapse.

For half a century the systolic click and late systolic murmur lay dormant as innocent auscultatory curiosities. The thirteen years since Barlow related these phenomena to mitral leaflet prolapse have witnessed an astonishing information explosion. We have sought to bring together the accumulated data in this review. An Historical Perspective traces the evolution from the now abandoned "pericardial" or "extracardiac" phases, through the leafletchordal phase (redundancy), the myocardial phase (segmental left ventricular contraction abnormalities), to the anular phase (dilatation and faulty systolic contraction). Functional Anatomy is dealt with in terms of pathology, pathophysiology, hemodynamics, angiocardiography, echocardiography, and physical and pharmacological interventions. Clinical Manifestations are concerned with prevalence, natural history, symptoms, physical signs, electrocardiographic abnormalities and roentgen fingings. The four Major Complications- sudden death, infective endocarditis, spontaneous rupture of chordae tendineae, and progressive mitral regurgitation- are examined. Associated Cardiac Diseases, i.e., Marfan's syndrome, ostium secundum atrial septal defect and atherosclerotic coronary artery disease, are discussed, and a section on Treatment deals chiefly with prophylaxis for infective endocarditis and the management of arrhythmias and chest pain. A final section on Evolving Information considers etiologic concepts, the nature of left ventricular contration abnormalities, the cause of chest pain, the relationship to Marfan's syndrome and ostium secundum atrial septal defect, and the effect of aging and sex differences on leaflet chordal redundancy.

Echocardiography↗
PubMed1975

Ultrasound in the diagnosis of congenital heart disease.

In addition to recording the motion of the mitral, tricuspid, aortic, and pulmonic valves, echocardiography can identify right and left ventricular cavities and the interventricular septum. Disorders such as atrial-septal defect, valvular and subvalvular aortic stenosis, pulmonic stenosis, Ebstein's anomaly of the tricuspid valve, and the hypoplastic left-heart syndrome can readily be evaluated by echocardiography. In tetralogy of Fallot and truncus arteriosus, discontinuity between the anterior aortic wall and septum with overriding aorta has been demonstrated. Doubleoutlet right ventricle is associated with posterior aortic wall and mitral valve discontinuity. In disorders such as single ventricle, tricuspid atresia, and endocardial cushion defect with common A-V canal, echocardiographic demonstration of the absence of the interventricular septum has provided the clinician with valuable information. Newer techniques such as compound-B ultrasonography, which produces a two-dimensional cross-sectional image of intracardiac structures, and multiscan echocardiography will enhance the use of conventional echocardiography by providing a more accurate anatomic display of cardiac chambers and outflow vessels.

Adult↗
PubMedDate not supplied

Multicenter trial of automated border detection in cardiac MR imaging.

The purpose of the present study was to evaluate the robustness of a method of automated border detection in cardiac magnetic resonance (MR) imaging. Thirty-seven short-axis spin-echo cardiac images were acquired from three medical centers, each with its own image-acquisition protocol. Endo- and epicardial borders and areas were derived from these images with a graph-searching-based method of edge detection. Computer results were compared with observer-traced borders. The method accurately defined myocardial borders in 36 of 37 images (97%), with excellent agreement between computer- and observer-derived endocardial and epicardial areas (correlation coefficients, .94-.99). The algorithm worked equally well for data from all three centers, despite differences in image-acquisition protocols, MR systems, and field strengths. These data suggest that a method of computer-assisted edge detection based on graph-searching principles yields endocardial and epicardial areas that correlate well with those derived by an independent observer.

Adult↗
PubMedDate not supplied

Clinical validation of an edge detection algorithm for two-dimensional echocardiographic short-axis images.

The purpose of this study was to validate an edge detection algorithm for short-axis two-dimensional echocardiographic studies in a protocol that stimulated its implementation at multiple clinical laboratories. Six short-axis two-dimensional echocardiographic studies were solicited from each of five clinical laboratories. A single cardiac cycle from each of the resulting 30 studies was entered into the computer system. Five expert observers came to the laboratory on separate occasions and traced endocardial borders from the short-axis studies on 2 separate days. The computer algorithm generated borders on each frame of the cardiac cycles on the basis of regions of search defined by the observers. Of the 30 original studies, five were considered excellent, seven were good, nine were poor, and nine were technically inadequate by consensus of the five observers. The correlation coefficient for computer-defined borders with manually defined borders in the excellent quality studies was 0.985. Interobserver variability was expressed as the mean percent area difference for all possible pairings of observers. The mean percent area differences were decreased from +/- 9.8% to +/- 5.3%, +/- 12.5% to +/- 8.4%, and +/- 17.4% to +/- 15.6% when comparing observer with computer-generated borders in the excellent, good, and poor quality studies, respectively. Intraobserver variability was expressed as decrease in mean percent area difference on corresponding frames between days 1 and 2. Intraobserver variability was decreased from +/- 6.5% to +/- 4.5%, +/- 10.8% to +/- 7.0%, and +/- 14.0% to +/- 11.9%, respectively. All reductions in variability were statistically significant at p less than 0.01. Observer acceptance of computer-defined borders was estimated at 94%, 93%, and 97% for excellent, good, and poor quality studies, respectively. Once the observer defined a region of search, computer process time to generate all borders in the cardiac cycle was approximately 4 minutes. The conclusion is that the algorithm produces accurate, reliable, and acceptable borders.

Algorithms↗
PubMedDate not supplied

Recommendations for quantitation of the left ventricle by two-dimensional echocardiography. American Society of Echocardiography Committee on Standards, Subcommittee on Quantitation of Two-Dimensional Echocardiograms.

We have presented recommendations for the optimum acquisition of quantitative two-dimensional data in the current echocardiographic environment. It is likely that advances in imaging may enhance or supplement these approaches. For example, three-dimensional reconstruction methods may greatly augment the accuracy of volume determination if they become more efficient. The development of three-dimensional methods will depend in turn on vastly improved transthoracic resolution similar to that now obtainable by transesophageal echocardiography. Better resolution will also make the use of more direct methods of measuring myocardial mass practical. For example, if the epicardium were well resolved in the long-axis apical views, the myocardial shell volume could be measured directly by the biplane method of discs rather than extrapolating myocardial thickness from a single short-axis view. At present, it is our opinion that current technology justifies the clinical use of the quantitative two-dimensional methods described in this article. When technically feasible, and if resources permit, we recommend the routine reporting of left ventricular ejection fraction, diastolic volume, mass, and wall motion score.

Algorithms↗