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Biomedical subjects

C B Higgins

Publications and source records attributed to C B Higgins.

At least 379 records · Page 21Linked to original sources
PubMed1984

Effects of atrial pacing on global and regional left ventricular function in coronary heart disease assessed by digital intravenous ventriculography.

Digital i.v. ventriculography in conjunction with rapid atrial pacing was used to assess the effects of ischemic stress on global and regional function in 22 patients referred for cardiac catheterization (5 had normal coronary arteries and 17 had greater than 70% diameter reduction of at least 1 major coronary artery). End-diastolic, end-systolic and stroke volume indexes and the ejection fraction were determined by an area-length technique from the mask mode images before and after pacing. In addition, segmental responses were quantitated using a radial shortening method. Subjects with normal coronary arteries showed no overall change in the postpacing volume or ejection fraction indexes. Coronary patients showed no overall change in postpacing end-diastolic volume (86 +/- 25 ml/m2 at control vs 90 +/- 31 ml/m2 after pacing, difference not significant), but there was a significant increase in end-systolic volume (25 +/- 15 ml/m2 at control vs 32 +/- 18 ml/m2 after pacing, p less than 0.005) and a decrease in ejection fraction (72 +/- 11% at rest vs 64 +/- 18% after pacing, p less than 0.025). Furthermore, quantitative deterioration in wall motion was seen in 14 of 17 coronary patients (82%) and in none of the normal patients. Analysis of segmental wall motion was the most sensitive diagnostic variable. A combination of atrial pacing stress testing and digital i.v. ventriculography is useful in detecting functionally significant coronary disease through quantitation of global and regional dysfunction which does not require arterial cannulation.

Adult↗
PubMed1984

Use of computerized tomography to assess myocardial infarct size and ventricular function in dogs during acute coronary occlusion and reperfusion.

Prospectively ECG-gated and nongated computed tomography (CT) can be used to assess global and regional left ventricular (LV) function and to measure myocardial infarct (MI) size. In the current study, CT was used to assess the effects of coronary occlusion and reperfusion in 16 dogs. Ten dogs were subjected to permanent occlusion of the proximal left anterior descending coronary artery and 6 dogs were reperfused after a 2-hour period of total coronary occlusion. Gated scans were used to quantitate the extent of wall thickening in the ischemic zone and to assess changes in mid-LV cross-sectional chamber area at end-diastole and end-systole. Nongated scans were used to estimate the size of the initial perfusion defect during contrast injection shortly after coronary occlusion and the size of the MI as indicated by delayed enhancement of the infarct 10 to 30 minutes after cessation of contrast administration. Neither group showed significant changes in end-diastolic chamber area during acute occlusion or 3 days later. Both groups showed a significant deterioration in percent change in chamber area both early after coronary occlusion and 3 days later; however, in the permanent occlusion group, percent wall thickening in the ischemic zone decreased from 46.2 +/- 16.5% (mean +/- standard deviation) to 1.6 +/- 9.0% during acute occlusion (p less than 0.01) and thickening remained depressed 3 days later (2.4 +/- 10.1%, p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1984

Comparative effects of ionic and nonionic contrast materials on indexes of isovolumic contraction and relaxation in humans.

The effects of contrast media on left ventricular (LV) relaxation as assessed by the time constant of isovolumic relaxation have not previously been studied. A new nonionic contrast agent (iohexol) has been shown to have fewer deleterious effects than standard ionic agents. Nineteen patients received iohexol and sodium meglumine diatrizoate (Renografin-76) in a double-blind, crossover study during left and right coronary arteriography and with simultaneous high-fidelity micromanometer measurements of LV pressure. Neither agent induced significant changes in LV end-diastolic pressure after right or left coronary arteriography. After right coronary arteriography, neither agent produced significant deterioration of peak positive dP/dt or (dP/dt)/DP40 (dP/dt at a developed pressure of 40 mm Hg). However, after right coronary arteriography both agents caused a transient deterioration in peak negative dP/dt and the time constant of isovolumic relaxation (p less than 0.05 at 20 seconds after arteriography). After left coronary arteriography, sodium meglumine diatrizoate induced deterioration of systemic blood pressure (p less than 0.05), peak positive dP/dt (p less than 0.01), (dP/dt)/DP40 (p less than 0.05), peak negative dP/dt (p less than 0.01) and the relaxation time constant (p less than 0.01). These effects were not induced by iohexol. Thus, nonionic contrast media exert negligible alterations on LV function when used for coronary arteriography. The findings are of potential clinical importance in view of the large number of patients with depressed LV function who undergo coronary arteriography.

Coronary Angiography↗
PubMed1984

Serial echocardiograms in patients with congestive cardiomyopathies: lack of evidence for thrombus formation.

We studied 90 patients with congestive myocardial disease documented at cardiac catheterization (46 idiopathic, 39 ischemic, and 5 hypertensive) who underwent M-mode and two-dimensional echocardiograms every 2-3 months for up to 7 years (mean 3.4 +/- 1.6 years, +/- 1 S.D.). All had angiographic evidence of severe left ventricular dysfunction (left ventricular ejection fraction less than 40%), and were on a variety of inotropic, diuretic, and vasodilating drugs. Only 9 were ingesting anticoagulants (5 warfarin and 4 aspirin), those on warfarin had documented pulmonary emboli or deep venous thrombosis. All but 4 patients were in normal sinus rhythm. Only one subject in this group was found to have a myocardial (left ventricular) thrombus. Postmortem examinations of 27 patients confirmed the ultrasound data. Thus, we conclude that cardiac thrombi are unusual in patients with congestive cardiomyopathies and rarely develop over the course of the illness even in the absence of chronic anticoagulation.

Adult↗
PubMed1984

Nuclear magnetic resonance analysis of acute and chronic myocardial infarction in dogs: alterations in spin-lattice relaxation times.

The purpose of this study was to evaluate the effects of acute and chronic ischemic injury on myocardial spin-lattice relaxation times (T1) in dogs. Ligation of the left anterior descending coronary artery was performed on 23 dogs which were divided into four experimental groups and killed at 3 hours (n = 6), 4 days (n = 6), 21 days (n = 5), and 56 days (n = 6) after coronary occlusion. T1 was measured in vitro with a 2.5 kg nuclear magnetic resonance (NMR) spectrometer using tissue from ischemic and control areas of the myocardium. Both the 3-hour and 4-day groups showed prolongations in T1 (p less than 0.01) for tissue from the ischemic area. In the 21-day group, two infarcts showed an increase in T1, two showed a decrease in T1, and one showed no significant change. The 56-day old infarcts had a lower mean value for T1 than control myocardium (p less than 0.01). The differences in myocardial water content between control and infarcted myocardium were found to parallel changes in T1 values in each experimental group. Pathologic examination of the myocardial scar from 21- and 56-day-old infarcts revealed extensive fibrosis in the infarcts with lower T1 values and tissue water contents than control myocardium. We conclude that myocardial edema in 3-hour and 4-day-old infarcts results in association with prolongations in T1. Twenty-one-day-old infarcts may be edematous (with increased T1) or fibrotic (with T1 values lower than normal myocardium), while 56-day-old infarcts are fibrotic and have shorter T1 values than normal myocardium.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Acute effects of doxorubicin (adriamycin) on left ventricular function in dogs.

Although chronic doxorubicin (adriamycin) cardiotoxicity often is attributed to repeated episodes of acute myocardial injury, the acute effects of doxorubicin on in vivo left ventricular performance have not been studied in a carefully controlled setting. Accordingly, we recorded high-fidelity left ventricular pressures and segmental dimensions before and after either intravenous or intracoronary doxorubicin in twelve open-chest dogs. Propranolol was administered to prevent reflex sympathetic stimulation, and heart rate was held constant by atrial pacing. Intravenous doxorubicin (1.5 mg/kg) (n = 6) caused significant decreases in all measured indices of myocardial contractility, in association with a large decrease in left ventricular systolic pressure (125 +/- 28 and 81 +/- 23 mm Hg before and 5 min after doxorubicin, respectively, P less than 0.01). Intracoronary doxorubicin (0.075 to 0.3 mg/kg) (n = 6) caused similar decreases in percent segment shortening (from 19 +/- 7 to 16 +/- 8, P less than 0.05), mean normalized shortening rate (from 0.87 +/- 0.34 to 0.71 +/- 0.37 segment lengths/sec, P less than 0.05), and peak positive left ventricular dP/dt (by 10 +/- 11%, P less than 0.07), although left ventricular systolic pressure was only modestly decreased (126 +/- 20 and 113 +/- 17 mm Hg before and after doxorubicin, respectively, P less than 0.01). Intracoronary doxorubicin also slowed the rate of left ventricular relaxation, as evidenced by an increase in the time constant for isovolumic pressure fall from 32.0 +/- 9.0 to 36.9 +/- 7.5 msec, and significantly altered the relationship between left ventricular pressure and dimension at end-diastole.

Animals↗
PubMed1984

Cardiovascular applications of magnetic resonance imaging.

Magnetic resonance imaging (MRI) is a completely noninvasive modality that has shown significant promise for the evaluation of the cardiovascular system. Our imaging technique employed electrocardiographic (ECG) gating, which resulted in well-resolved images of the cardiac structures. Patients and animals with a variety of cardiovascular abnormalities were also assessed with this technique; the abnormalities included acute and remote myocardial infarctions and their sequelae, atherosclerotic plaques, hypertrophic cardiomyopathy, pericardial diseases, and aneurysms. The diagnostic utility of MRI includes direct tissue characterization, and such utility may be further extended by the use of paramagnetic contrast media. In addition, metabolic imaging of elements other than hydrogen may further increase the clinical potential of MRI for assessment of the cardiovascular system.

Animals↗
PubMed1984

Myocardial infarct size determined by computed transmission tomography in canine infarcts of various ages and in the presence of coronary reperfusion.

Thirty-one dogs underwent in vivo scanning with computed transmission tomography; 15 dogs were studied within 7 days (mean 4) after coronary occlusion, 10 dogs 21 to 25 days (mean 28) after occlusion and 6 dogs 4 days after coronary reperfusion of a 2 to 3 hour coronary ligation. Ungated scans (1 cm in depth) of the left ventricle were obtained from apex to base to determine infarct size. In all animals with documented (postmortem) infarction (n = 26), contrast medium caused delayed enhancement of the entire infarct or the periphery of the infarct. Infarct size was calculated from scans showing contrast enhancement of the infarct. Infarct size was also determined from the postmortem heart using histochemical morphometry (nitroblue tetrazolium) and then compared with infarct size derived from tomography using the outer margin of the contrast-enhanced periphery of the infarct as the border of the infarct. Infarct size calculated by the tomographic technique (excluding the animals without an infarct) correlated well with infarct size determined at autopsy (r = 0.90, p less than 0.001). The tomographic estimate (18.2 +/- 11.3 g) of infarct size was similar to autopsy values (18.6 +/- 11.8 g, p = NS). Thus, ungated computed transmission tomographic imaging of the heart can reliably estimate infarct size in a variety of potential clinical circumstances, particularly when the area of rim enhancement of the infarct is included within the presumed infarct region.

Animals↗
PubMed1984

Computed tomography in congenital heart disease.

The CT results in defining anatomic and certain physiologic features in patients with congenital heart and great vessel anomalies were reviewed in 32 patients with a variety of congenital cardiac and aortic arch anomalies. Most of these cases (18 patients) were selected on the basis of angiocardiographic or echocardiographic studies performed prior to the CT evaluation. In 14 patients CT was performed as the initial study. All examinations were contrast enhanced and performed on a third generation CT scanner with scan time of 2 or 4 s. The CT demonstration of abnormalities of the great vessels such as positional anomalies, atresias, and hypoplasias was equivalent to angiocardiography and usually superior to two-dimensional echocardiography. The CT results in 14 patients were sufficient to obviate catheterization and angiography; most of these cases were abnormalities of the thoracic aorta. The CT evaluation of intracardiac anatomy was inconsistent. It adequately defined septal defects and configurational (Ebstein anomaly) and bulboventricular loop abnormalities of the ventricles. However, valve anomalies were not adequately demonstrated by CT. The three-dimensional representation of cardiac and mediastinal vascular anatomy provided by this relatively noninvasive technique gives unique information in some cardiovascular anomalies. When faster scanning times are introduced, more definition of the cardiac structures should be possible, further increasing the diagnostic potential of CT.

Adolescent↗
PubMed1984

Perfluoroctylbromide as a blood pool contrast agent for liver, spleen, and vascular imaging in computed tomography.

Perfluoroctylbromide (PFOB) in emulsion form was tested as a blood pool imaging agent for computed tomography (CT) in five animals (three dogs and two pigs). Computed tomography of the kidneys, liver, spleen, and mediastinum was performed in the control state and at various time intervals after the end of PFOB infusion. The attenuation coefficient of the vascular space increased by 117 Hounsfield units (HU) (range 105-128 HU), the liver by 54 HU (range 43-70 HU), and the spleen by 77 HU (range 69-86 HU) 30 to 50 min after the end of PFOB infusion, 5 ml/kg. The vascular space enhanced by 25 HU for every g of PFOB/100 ml of blood and remained at almost a constant level for hours after the end of infusion. In conclusion, PFOB emulsion, in addition to hepatosplenic enhancement, produces prolonged and substantial opacification of the vascular space, allowing CT imaging of the heart and vascular structures minutes to hours after the end of infusion.

Angiography↗
PubMed1984

Primary diagnosis of abdominal arteriovenous fistula by MR imaging.

Two cases of abdominal arteriovenous (AV) fistula were imaged by magnetic resonance (MR). Magnetic resonance imaging showed abnormally increased flow with resultant dilatation of the veins draining the site of the fistula. Findings were correlated with CT, digital subtraction angiography, and arteriography. This report suggests the usefulness of MR imaging as the initial imaging technique of choice in clinically suspected cases of AV fistula. The diagnosis can be made within 30 to 45 min of imaging time and does not require administration of contrast material.

Abdomen↗
PubMed1984

Demonstration of the fetal cardiovascular system by MR imaging.

Magnetic resonance is potentially a second imaging modality that can be used to study the fetal cardiovascular system. Magnetic resonance imaging to date has not been associated with any harmful effects and, since it does not involve ionizing radiation, we are evaluating its role in fetal imaging. We report a case in which this modality showed the unique features of the cardiovascular system.

Adult↗
PubMed1984

Cardiac imaging using gated magnetic resonance.

To overcome the limitations of magnetic resonance (MR) cardiac imaging using nongated data acquisition, three methods for acquiring a gating signal, which could be applied in the presence of a magnetic field, were tested: an air-filled plethysmograph, a laser-Doppler capillary perfusion flowmeter, and an electrocardiographic gating device. The gating signal was used for timing of MR imaging sequences (IS). Application of each gating method yielded significant improvements in structural MR image resolution of the beating heart, although with both plethysmography and laser-Doppler velocimetry it was difficult to obtain cardiac images from the early portion of the cardiac cycle due to an intrinsic delay between the ECG R wave and peripheral detection of the gating signal. Variations in the temporal relationship between the R wave and plethysmographic and laser-Doppler signals produced inconsistencies in the timing of IS. Since the ECG signal is virtually free of these problems, the preferable gating technique is IS synchronization with an electrocardiogram. The gated images acquired with this method provide sharp definition of internal cardiac morphology and can be temporarily referenced to end diastole and end systole or intermediate points.

Animals↗
PubMed1984

Magnetic resonance imaging of the pericardium: normal and pathologic findings.

Twenty normal subjects and ten patients with pericardial abnormalities underwent ECG-gated magnetic resonance (MR) imaging of the thorax using a 0.35-tesla superconducting system. The patients with pericardial abnormalities were also evaluated with serial chest radiographs, ultrasound, computed tomography, and/or angiography. ECG gating was necessary to identify the normal pericardium, which was visualized as a 1- to 2-mm-wide curvilinear structure of low signal intensity. Pericardial thickening in constrictive pericarditis was clearly delineated on gated MR images. Pericardial inflammation caused a marked increase in signal intensity as well as thickening of the pericardium. Pericardial effusions and pericardial adhesions were also demonstrated. A simple pericardial cyst and a complex pericardial mass were identified and differentiated from pericardial fat and diaphragmatic eventration. MR appears to be an important modality for the evaluation of pericardial disease.

Adult↗
PubMed1984

Experimental pericardial inflammation evaluated by computed tomography.

Experimental pericardial inflammation was evaluated with ungated and cardiac gated computed tomography (CT) in 12 dogs, including 2 controls. All were studied during and after contrast infusion; in addition, several were sequentially imaged for up to six weeks after inducing inflammation by instilling toxic materials into the pericardial space. All dogs with inflammation had contrast enhancement of the parietal and visceral pericardium; this could be demonstrated within one week of the pericardial insult and for up to six weeks and was frequently associated with effusion. Increased pericardial density was not seen in controls or animals with pericarditis prior to contrast infusion. This technique may be useful in evaluating acute pericardial inflammation.

Animals↗
PubMed1984

Cardiac imaging with a high-speed Cine-CT Scanner: preliminary results.

CT scans were obtained with a Cine-CT Scanner that uses a rapidly moving focused electron beam. The 50-msec CT scans were obtained at two transverse levels simultaneously through the hearts of a series of four normal dogs and six patients, four with coronary artery disease and two with hypertrophic cardiomyopathy. Two scanning mode options were chosen. Myocardial wall thickening and motion were studied by obtaining ten 50-msec CT exposures during one heart-beat within less than one second (cine-CT mode). Regional myocardial blood flow was assessed by obtaining approximately 20 scans at the same level of the left ventricle; each 50-msec exposure was gated to the same phase of 20 sequential heartbeats after intravenous administration of contrast medium (dynamic mode). These initial studies show the feasibility of defining regional and global myocardial contraction using the cine-CT mode, and the considerable potential for measuring regional myocardial perfusion using the flow (dynamic) mode.

Animals↗