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Biomedical subjects

E Botvinick

Publications and source records attributed to E Botvinick.

At least 37 records · Page 2Linked to original sources
PubMed1985

Magnetic resonance imaging of the heart: a review of the experience in 172 subjects.

Gated magnetic resonance (MR) imaging was used to evaluate central cardiovascular anatomy in 172 subjects, 31 of whom were healthy volunteers. Using the spin-echo technique, images of diagnostic quality were obtained in 93% of cases with TE = 28 msec and in 65% of cases with TE = 56 msec. Transverse multisection sequences encompassing most of the left ventricle required approximately 6-8 minutes. Corroborative studies were available in 134 of 141 patients who had cardiovascular disease; two dimensional echocardiograms and angiography in 133 and 100 patients, respectively. Gated MR demonstrated the wall thinning and complications caused by prior myocardial infarctions and high signal intensity of the myocardium at the site of acute myocardial infarctions. MR accurately demonstrated anatomic abnormalities owing to hypertrophic and congestive cardiomyopathies, congenital abnormalities of the heart and great vessels, rheumatic heart disease, pulmonary hypertension, and cardiac and paracardiac masses. Depiction of cardiovascular anatomy and pathoanatomy was attained without the use of any contrast media. Consequently, gated MR is an effective technique for cardiac diagnosis. The short time required for tomographic examination of the entire heart using the multisection technique renders this a practical cardiac imaging modality.

Adolescent↗
PubMed1985

Detection and characterization of acute myocardial infarction in man with use of gated magnetic resonance.

To evaluate the capability of magnetic resonance imaging (MRI) in the detection and characterization of alterations in signal intensity and T2 relaxation time in acutely infarcted relative to normal myocardium 16 adult patients and normal volunteers were studied by electrocardiographically gated proton MRI. The seven volunteers were entirely asymptomatic and had no history of cardiovascular abnormality. The nine patients had each suffered an acute myocardial infarction within 5 to 12 days before the MRI studies. The diagnosis in each patient was confirmed by electrocardiographic (ECG) criteria and elevated levels of fractionated creatine kinase (CK) isoenzymes. Electrocardiographically gated MRI was performed with a superconducting system operating at 0.35 tesla. MRI demonstrated infarcted myocardium as a region of high signal intensity relative to that of adjacent normal myocardium; regions of high intensity corresponded anatomically to the site of infarction as defined by the ECG changes. The mean percent difference between normal and infarcted myocardium was substantially greater on 56 msec images (70.2 +/- 21.3%) compared with 28 msec images (27.1 +/- 13.6%). Region of interest analysis revealed that infarcted myocardium had a significantly (p less than .01) prolonged T2 relaxation time (mean T2 = 80.9 msec) relative to that in normal myocardium (mean T2 = 42.3 msec) and relative to the mean T2 of left ventricular myocardium in the volunteers (mean T2 = 42.4 msec). An additional finding for each patient with myocardial infarction was a high intraluminal flow signal on 56 msec images, but this was also observed in normal subjects and is therefore a nonspecific finding.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1984

Phase image characterization of localized and generalized left ventricular contraction abnormalities.

To evaluate their phase image characteristics, 61 patients with varying left ventricular contraction abnormalities were studied. In 16 normal patients, the left ventricular phase image revealed a homogeneous pattern, a narrow bell-shaped histogram and an orderly spatial progression of phase angle (phi). In 16 patients with segmental abnormalities, the left ventricular phase image showed a region of uniformly delayed phase angle corresponding to the site of segmental abnormality, a discrete secondary histogram peak and a discontinuous, but orderly, spatial progression of phase angle. The mean phase angle (phi) (23.6 +/- 15.7 degrees) and its standard deviation (17.6 +/- 7.2 degrees) differed from the normal group (7.6 +/- 11.1 degrees, p less than 0.002 and 8.9 +/- 2.8 degrees, p less than 0.001). The percent of end-diastolic volume involved in the segmental abnormality, calculated using phase data in 13 of these and in 11 additional patients with a left ventricular aneurysm on ventriculography, correlated well with the percent akinetic segment on scintigraphic (r = 0.78) and angiographic (r = 0.84) study. In 18 patients with generalized abnormalities, the left ventricular phase image revealed multiple regions of inhomogeneous phase angle, a grossly irregular histogram and a disorderly spatial progression of phase angle. The mean phase angle (56.4 +/- 23.9 degrees) and standard deviation (27.3 +/- 7.1 degrees) differed from values in the normal group and from patients with segmental contraction abnormalities (both p less than 0.001). The mean phase angle and its standard deviation in scattered regions with abnormally prolonged phase angle differed significantly from abnormal regions in patients with segmental abnormalities (both p less than 0.001). These patterns of left ventricular phase angle demonstrate characteristics that may help differentiate between ventricles with segmental and generalized contraction abnormalities. Their relation to underlying pathophysiology and potential clinical implications should be considered.

Adult↗
PubMed1984

Catheter-induced His bundle ablation in a patient with reentrant tachycardia associated with a nodoventricular tract.

A patient with refractory tachycardia associated with a nodoventricular tract in whom tachycardia was successfully controlled with catheter-induced ablation of the His bundle is reported. Tachycardia was always initiated by ventricular impulses that blocked retrogradely in the nodoventricular tract and conducted by way of the His-Purkinje system. The His bundle ablation was successfully accomplished by delivering two direct current countershocks of 400 J each in the region of the His bundle. Postablation, the patient manifested stable 1:1 anterograde conduction via the atrioventricular (AV) node-nodoventricular fiber over a wide range of heart rates (50 to 180 beats/min). A permanent pacemaker was not implanted at the patient's request. During 16 months of follow-up, the patient has had stable sinus rhythm with no sustained tachycardia. Brief asymptomatic episodes of ectopic atrial tachycardia have been recorded on ambulatory electrocardiographic monitoring. This case 1) demonstrates the potential role of ablation of the His bundle in patients with refractory tachycardia associated with a nodoventricular tract provided that the His bundle is a critical component in the initiation of the tachycardia or a part of the tachycardia circuit; 2) reveals stable 1:1 AV conduction over a nodoventricular tract; and 3) emphasizes the utility of the phase image technique for diagnosis of a Mahaim tract.

Adult↗
PubMed1984

Phase image evaluation of patients with ventricular pre-excitation syndromes.

To localize bypass pathways, left and right ventricular regions were analyzed at rest by phase image analysis in 18 patients with ventricular pre-excitation syndromes. These were compared with image findings in 18 normal subjects. In each of 17 patients with pre-excitation, the site localized on electrophysiologic study correlated closely with the region of earliest ventricular phase angle. This site could be objectively separated from that in normal subjects in each of eight patients with an active left-sided pathway and in both patients with a right-sided pathway. Those with a septal pathway revealed earliest septal phase angle, but could not be separated from normal subjects. In the eight patients with an active left bypass tract, the onset, upstroke and peak of the left ventricular phase histogram preceded those of the right ventricular histogram. Those with a left-sided pathway demonstrated a mean left ventricular phase angle, a difference between mean left and mean right ventricular phase angle and a difference between earliest left and right ventricular phase angles which was significantly less than that in normal subjects (p less than 0.05). These variables presented characteristic converse changes in those with a right-sided pathway. Sequential phase changes in 10 studies suggested "fusion" of normal septal with lateral bypass fronts. Electrocardiographic and electrophysiologic localization of the bypass pathway agreed in only 8 of 14 patients with a recognized delta wave. The phase image represents a new, noninvasive method of evaluating ventricular pre-excitation. The method may provide useful information complementary to that of electrocardiographic and electrophysiologic analysis.

Adolescent↗
PubMed1984

Magnetic resonance imaging strategies for heart studies.

Given a suitable trigger signal, cardiac synchronized magnetic resonance (MR) imaging is simple to implement; however, single section techniques are not efficacious, especially when the heart rate sets the repetition interval. We demonstrate multi-section, double, and single-echo imaging, any of which rapidly covers the cardiac volume; 3-D modes capable of achieving very thin sections; and cycled multi-section imaging capable of efficaciously providing dynamic data on heart motion. These modes form a complementary, powerful set of options for clinical work.

Heart↗
PubMed1984

Imaging and characterization of acute myocardial infarction in vivo by gated nuclear magnetic resonance.

Imaging by nuclear magnetic resonance (NMR) techniques has been shown to provide high-contrast resolution between soft tissues and characterization of normal and pathologic tissues by differences in magnetic relaxation times. The current study was designed to determine whether electrocardiogram (ECG)-gated NMR imaging of the canine heart in vivo could distinguish normal from infarcted myocardium without the use of intravenous paramagnetic contrast agents. Seven dogs were studied by ECG-gated NMR imaging in vivo (spin-echo technique) with a 0.35 Tesla superconducting magnet at 2 to 7 days after ligation of the left anterior descending coronary artery. In six of the seven dogs, signal intensity was increased in the anterior wall compared with the remainder of the left ventricle; this region of high signal intensity corresponded to the area of myocardial infarction demonstrated at postmortem examination. The signal intensity of the infarcted region was 66 +/- 27% greater than that of normal myocardium (p less than .01). The T2 (spin-spin) relaxation time was 69 +/- 3% longer in the infarcted myocardium as compared with normal myocardium (p less than .01). The NMR images from the seventh dog had uniform signal intensity throughout the myocardium of the left ventricle. An infarct was not evident on postmortem examination in this dog. Thus gated NMR imaging in vivo by the spin-echo technique displays acute myocardial infarctions as regions of high signal intensity without the use of contrast media. The infarct is characterized by a prolonged T2 relaxation time.

Animals↗
PubMed1984

Imaging by nuclear magnetic resonance in patients with chronic ischemic heart disease.

Cardiac anatomy was defined by gated nuclear magnetic resonance (NMR) imaging at a magnetic field strength of 3.5 kGauss in eight normal subjects and 10 patients with chronic myocardial infarctions. Multisectional imaging was performed with the spin-echo technique and encompassed most of the left ventricle in an imaging time of 5 to 12 min. In all subjects internal cardiac structure was well delineated without the use of any type of contrast medium. The myocardial wall-blood interface was sharply defined, resulting in visualization of trabeculations, papillary muscle, and chordal structures in both ventricles. In patients with ischemic heart disease, the extent of postinfarctional wall thinning, aneurysms, and mural thrombi were depicted on NMR images. Images obtained with the second spin-echo (delay time = 56 msec) demonstrated high signal intensity in regions of the left ventricular chamber adjacent to the site of aneurysms or infarctions; this finding suggested stasis of blood in a region of akinesis or dyskinesis. The results of this study show that gated NMR is feasible as a technique for imaging the human heart and is capable of demonstrating a variety of left ventricular abnormalities associated with chronic myocardial infarction. NMR is a completely noninvasive technique for clinical imaging of the cardiovascular system.

Adult↗
PubMed1983

Volume loading improves low cardiac output in experimental right ventricular infarction.

To evaluate the effect of volume loading in the low output state associated with right ventricular infarction, isolated right ventricular infarction was produced in seven dogs with the pericardium intact. Volume loading and pericardiotomy were then sequentially performed. After the production of right ventricular infarction, right ventricular systolic pressure decreased by 25%, aortic pressure by 36% and cardiac output by 32%. Right ventricular ejection fraction decreased by 57%, but left ventricular ejection fraction did not change significantly. Left ventricular transmural pressure and diastolic size decreased, and right ventricular diastolic size increased. Intrapericardial pressure increased and equalization of diastolic pressures was noted. Volume loading resulted in increased right ventricular systolic pressure and stroke work, increased aortic pressure and cardiac output and increased transmural pressure and diastolic size in both ventricles. Pericardiotomy resulted in further increases in right and left ventricular filling, stroke work and cardiac output, as well as resolution of equalized diastolic pressures. These results indicate that cardiac output in experimental right ventricular infarction increases with volume loading, which enhances left ventricular preload by augmenting right ventricular output. Elevated intrapericardial pressure affects filling of both ventricles and may play a role in the pathophysiology of low cardiac output in right ventricular infarction.

Animals↗
PubMed1983

Nuclear magnetic resonance imaging of the cardiovascular system: normal and pathologic findings.

Whole body nuclear magnetic resonance (NMR) imaging of the cardiovascular system was carried out in early clinical trials in 244 volunteers and patients using a 3.5 KGauss (0.35 T) unit. The spin echo technique with multiple imaging parameters was used. Blood vessels were clearly discriminated from solid organs and lesions because little or no intraluminal signal is seen with laminar blood flow at normal velocities, whereas a more intense image is generated by solid organs. Characteristic flow signals were observed in normal patients and were accentuated by varying the imaging parameters. Cardiac chambers were well delineated in some patients on nongated images. In one case, internal topography of the ventricles was exquisitely displayed on a gated image. Intraluminal pathology, such as dissection of the aorta, aneurysms of the aorta and left ventricle, and aortic atheroma, was clearly demonstrated. Patency of coronary arterial bypass grafts was shown. Abnormal flow patterns due to slow or turbulent flow were accentuated on images using the second spin echo. This preliminary experience indicates the considerable potential of NMR imaging in the evaluation of cardiovascular diseases.

Blood Flow Velocity↗
PubMed1983

Evaluation of the post-coronary artery bypass patient by myocardial perfusion scintigraphy and computed tomography.

The clinical utility of 201Tl scintigraphy and of computed tomography for the noninvasive assessment of graft patency and regional myocardial perfusion was evaluated in 24 patients who had undergone aortocoronary bypass surgery. Perfusion defects on 201Tl scintigraphy (reversible or new, fixed) correlated (100% sensitivity, 78% specificity) with occlusion or stenosis of a graft or significant new native vessel disease. Graft occlusion was accurately demonstrated by dynamic computed tomography (100% sensitivity, 96% specificity) but did not uniformly correlate with regional perfusion. Perfusion defects in the distribution of patent grafts resulted from progressive native vessel disease or graft stenosis without complete occlusion. The absence of exercise-induced perfusion defects in regions of occluded grafts was attributed to suboptimal exercise, collateralization, or noncritical native vessel stenosis. The two studies provide complementary anatomic and physiologic information in the evaluation of the postbypass patient.

Adult↗
PubMed1982

Diagnostic accuracy of cardiologists compared with probability calculations using Bayes' rule.

Probability analysis has provided insights into the use of diagnostic tests in coronary artery disease, and recent developments may permit clinical application of individual patients. To validate independently two available methods of probability calculation, their diagnostic accuracy was compared with that of cardiologists. Ninety-one cardiologists participated in the study; each evaluated the clinical summaries of eight randomly selected patients. For each patient, the cardiologist assessed the probability of coronary artery disease after reviewing the clinical history, physical examination and laboratory data, including complete results from a treadmill exercise test. The probability of coronary artery disease was also obtained for each patient, using the identical information, from two methods employing Bayes' rule: (1) from a published table of data based on the patient's age, sex, symptoms and degree of S-T segment change during exercise; and (2) from a computer program using the age, sex, risk factors, resting electrocardiogram and multiple exercise measurements. Diagnostic accuracy was assessed on a scale from 0 to 100 with the coronary angiogram as the diagnostic standard. The average diagnostic accuracy on this scale was: 80.2 for the cardiologists' estimates, 78.0 for the estimates based on tables (difference from cardiologists' estimates p less than 0.05) and 83.1 for the estimates based on computer calculations (p less than 0.01). Thus probability analysis incorporating sufficient detail can achieve a diagnostic accuracy comparable with that of cardiologists. Studies of the efficacy of probability analysis in patient care are warranted.

Bayes Theorem↗
PubMed1982

Are regions of ischaemia detected on stress perfusion scintigraphy predictive of sites of subsequent myocardial infarction?

To determine the relation between scintigraphic regions of stress-induced ischaemia and subsequent myocardial infarction, a select group of 21 patients was investigated. Each patient had undergone stress perfusion scintigraphy before myocardial infarction was recorded. After acute infarction, thallium-201 perfusion scintigraphy was performed in 16 patients (76%) and 99mTc (stannous) pyrophosphate in 14 patients (67%). All patients had at least one post-myocardial infarction scintigram and nine (42%) had both perfusion scintigraphy and infarct imaging. Nineteen patients (90%) had scintigraphic evidence of stress-induced ischaemia pre-infarction. Scintigraphic regions of infarction were compared with regions of previously demonstrated stress-induced ischaemia. In 11 patients (53%) the myocardial infarction was more extensive; in one of these patients, reimaged one week before myocardial infarction, and in four others (19%) there were matching defects; in three patients (14%) the infarction was less extensive, and in two patients (9%) the infarction was less extensive but also involved regions not previously shown to develop ischaemia. In the final patient (5%) there was no match. Stress perfusion scintigraphy was generally abnormal before acute infarction in this group of patients. Acute infarction frequently involved regions previously shown to develop stress-induced ischaemia, though these often underestimated the extent of myocardium at risk.

Aged↗
PubMed1982

The phase image: its relationship to patterns of contraction and conduction.

To determine the relationship of phase changes and abnormalities of ventricular contraction and conduction, we performed phase image analysis of blood pool scintigrams in 29 patients. Eleven patients had no evidence of blood pool contraction or ECG conduction abnormalities, four had contraction abnormalities, seven had abnormal conduction and seven had abnormalities of both variables. The phase delay generally related to the degree of contraction abnormality. The mean phase delay in hypokinetic segments differed from that in normokinetic segments in the same patient (p less than 0.025), the phase delay of akinetic and dyskinetic segments differed from that in normokinetic segments (p less than 0.001) and the phase delay in dyskinetic segments differed from that in akinetic segments (p less than 0.005), but there was a significant overlap in the phase delay in normal and hypokinetic segments. Also, in patients with conduction abnormalities, the minimal associated regional phase delay presented a phase dispersion and a pattern of contraction consistent with the pattern of conduction and different from normal. A single study performed both at rest and with stress demonstrated the effect of heart rate on phase assessment and confirmed the independent effects of contraction and conduction on phase delay. Acquisition and analytic methods should add significantly to the resolution of the phase method.

Arrhythmias, Cardiac↗
PubMed1982

The independent value of exercise thallium scintigraphy to physicians.

To determine the effect of exercise myocardial scintigraphy with thallium-201 on diagnostic accuracy and the need for coronary angiography, consecutive patients with a variety of clinical presentations were identified. Clinical summaries, including a detailed history, physical examination, and complete data from a standard treadmill exercise test, were presented to 91 cardiologists. The cardiologists assessed the probability of coronary disease and the need for coronary angiography. They were then presented the results of thallium scintigraphy and revised their assessments if warranted. Scintigraphy significantly increased the cardiologists' diagnostic accuracy beyond that attained with other clinical information (p less than 0.0001). The change in accuracy varied from + 4% to + 20% in different patient groups, and was greatest in patients with atypical angina and a positive exercise ECG. Ratings of the need for coronary angiography changed from -13% to +21% in different patient groups. We conclude that exercise thallium scintigraphy can provide independent diagnostic information and influence the need for coronary angiography.

Coronary Angiography↗
PubMed1981

Contrast enhancement of thallium-201 myocardial scintigrams: improved sensitivity with diminished specificity in coronary disease detection.

Thallium-201 myocardial scintigraphy (TMS) has become an increasingly popular noninvasive technique with a high diagnostic specificity, but a somewhat lower sensitivity for coronary disease (CAD) detection. Many centers now routinely employ computer techniques to contrast enhance scintigrams, but the resulting changes in sensitivity and specificity have not been carefully evaluated. In the present study, three observers with different levels of experience blindly interpreted both unprocessed and enhanced exercise TMS from 40 patients with CAD and from 15 without significant obstructions. The sensitivity for CAD achieved by each observer was higher with the enhanced scintigrams (increase from an average of 80% to 93%), but there was concomitant loss of specificity (from 93% to 73%). Similarly, significant changes were present in the sensitivity and specificity with which ischemic regions were diagnosed. In addition, contrast enhancement facilitated interpretation of TMS studies, particularly in making comparisons between exercise scintigrams and subsequent rest or redistribution images. Contrast enhancement affected the interpretations of the inexperienced observer most significantly. We conclude that contrast enhancement improves TMS sensitivity but results in some loss of specificity. The variable effect of enhancement on observers with different levels of experience suggests that laboratories should critically evaluate their own results before routinely employing computer processing.

Computers↗