Magnetic resonance spectroscopy of the heart.
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Adenosine Triphosphate↗
Biomedical subjects
C B Higgins
Publications and source records attributed to C B Higgins.
MR imaging of cardiac thrombi.
This retrospective study of 10 magnetic resonance (MR) examinations in patients with cardiac thrombi (eight in left ventricle and two in right atrium) was performed to assess the ability of MR for demonstrating cardiac thrombi and describe the appearance of cardiac thrombi using the spin echo technique. Cardiac thrombi usually had higher signal intensity than the normal myocardium on MR imaging, especially on the second echo (TE of 56 or 60 ms) image. Differentiation between cardiac thrombus and intracardiac signal resulting from slowly flowing blood was possible based on different signal intensity changes using various techniques. In conclusion, MI imaging constitutes another noninvasive modality for the detection of cardiac thrombus. Further work is needed to determine its accuracy compared with that of two-dimensional echocardiography.
Adult↗
MR imaging of aortoiliac atherosclerosis with 3D image reconstruction.
A computer program was written to detect blood flow in a sequence of magnetic resonance images, using reduction in first echo intensity and prolongation of calculated T2 value, and to construct three-dimensional vessel maps from the detected flow regions. Reconstructed vessel images were coded to show cross-sectional area of the lumen and relative flow velocity along the length of the vessel. The program was applied to imaging the aorta and iliac arteries in 11 patients with atherosclerosis and results were compared with angiography. All sites of narrowing were identified by the algorithm, but no flow at all was detected at one site of partial occlusion.
Aortic Diseases↗
Effects of intracoronary administration of contrast materials on left ventricular dimensions and rate of relaxation.
The effects of intracoronary administration of ionic and nonionic contrast materials on (LV)left ventricular contractile state, relaxation rate (peak -dp/dt and [-dp/dt]50), and dimensions were determined in eight morphine-chloralose anesthetized dogs. Meglumine sodium diatrizoate caused decreases in peak dp/dt and -dp/dt and increases in left ventricular end systolic dimension (LVESD'), end diastolic dimension (LVEDD'), and end diastolic pressure(LVEDP). The decreases in peak -dp/dt and(-dp/dt)50 persisted after peak dp/dt returned to and exceeded control levels. Calcium meglumine sodium metrizoate caused increases in peak dp/dt but decreases in peak -dp/dt and(-dp/dt)50 and no significant changes in LVEDP, LVESD', or LVED'D. Metrizamide caused no significant changes. Ionic contrast materials induce important changes in LV dimensions and rate of relaxation in addition to producing a depression in contractile state. The decreases in relaxation rate are not reversed by addition of calcium ions.
Animals↗
Pulmonary density distribution in experimental noncardiac canine pulmonary edema evaluated by computed transmission tomography.
We evaluated the density distribution (anterior-posterior) of the right lung in 19 acutely anesthetized supine dogs using computed transmission tomography (CTT). Eleven dogs served as controls, and eight received 0.12 cc/kg of intravenously administered oleic acid. The latter were sequentially imaged over 1 hour. Nine of these dogs (three control and six oleic acid dogs) had wet weight/dry weight ratios of the corresponding anterior and posterior lung sections evaluated immediately upon completion of the scans. In the control animals, the posterior (dependent) lung was 25 +/- 8% (+/- S.D.) denser than the anterior lung, and did not differ if a second section of the lung was evaluated (1 cm cranial or caudal), or if the animal was imaged on a second day (n = 6). In the oleic acid dogs, the posterior portion of the lung was significantly denser 10 minutes after injection of oleic acid (P less than 0.05), and almost twice as dense 1 hour after initial injection. The density changes determined by CTT in the anterior and posterior lung zones correlated well with the increasing regional wet weight/dry weight relationships determined from the lung on postmortem exam (r = 0.90). We conclude that early subtle density changes in the posterior lung can be found in oleic acid injury pulmonary edema. This can be easily quantitated using CTT, and may prove useful in following physiologic and therapeutic interventions during leaky membrane acute pulmonary injury.
Animals↗
Combined actions of verapamil and contrast media on atrioventricular conduction. Influence of osmolality of the media.
Since verapamil and contrast media both cause depression in the electrophysiologic function of the heart and both may exert these effects by actions on ionic calcium, the possible interaction of verapamil and intracoronary contrast media on atrioventricular conduction was studied in six dogs using surface electrocardiography and HIS bundle electrogram. The effects of intracoronary injection of standard ionic media (Renografin 76) and low osmolal contrast media (Hexabrix and Hexabrix with calcium [8 mEq/L]) were compared. Each contrast media was assessed in the normal state and at four increasing doses of verapamil (0.125, 0.25, 0.5, and 1.0 mg/kg). The PR and AH intervals were substantially prolonged by intracoronary injection of Renografin 76 in the presence of a 1.0 mg/kg dose of verapamil (172 +/- 41 msec to 724 +/- 48 msec, P less than 0.05 for PR interval, and 182 +/- 41 msec to 734 +/- 51 msec, P less than 0.05 for AH interval), with most animals developing second degree heart block (Mobitz, type I). There was no change in the HV interval. Hexabrix and Hexabrix with calcium did not cause significant changes in PR or AH intervals at similar doses of verapamil. Thus, standard ionic contrast causes severe inhibition of atrioventricular conduction in the presence of verapamil, whereas low osmolal contrast media cause no significant negative dromotropic effects either in the presence or absence of verapamil. The osmolality of contrast media is an important mechanism responsible for the depression in atrioventricular conduction attending intracoronary contrast media in the presence of verapamil.
Animals↗
Effects of low osmolality contrast materials on coronary hemodynamics, myocardial function, and coronary sinus osmolality in normal and ischemic states.
The effects of intracoronary administration of contrast materials on regional and global left ventricular (LV) function and coronary sinus osmolality were assessed in six anesthetized dogs with segmental myocardial ischemia produced by critical stenosis of the circumflex coronary artery. Effects caused by Renografin (sodium meglumine diatrizoate), two new low osmolality contrast agents (Hexabrix and Hexabrix with added calcium ions), and metrizamide were evaluated. In a nonischemic state, Renografin produced an early (0-10 seconds) decrease in LV contractility followed by a late (10-20 seconds) rebound augmentation in contractility. In the presence of regional ischemia, there are prolongation of the depression of the myocardial contractile state. The monoacid dimer, Hexabrix, demonstrated a similar biphasic response, although the initial depression of myocardial contractility was significantly less than that observed with Renografin. Hexabrix with added calcium ions and metrizamide produced only augmentation in global and regional parameters of LV contractile function. This lack of depressant effects was also observed in the ischemic state. Renografin caused a significantly greater increase in coronary sinus osmolality (Tp) as compared with Hexabrix, Hexabrix-Ca++, and metrizamide. The increases in osmolality in response to the latter three contrast agents were statistically indistinguishable.
Animals↗
Comparative effects of ionic anc nonionic contrast materials on coronary and peripheral blood flow.
Contrast materials may alter coronary blood flow (CBF) by a direct vasodilating action or indirectly by changing determinants of myocardial oxygen requirements (MVO2). The current study compared the vasodilatory actions of ionic (Renografin 76, R76) and nonionic contrast materials (iohexol and metrizamide) after direct injection into the coronary and femoral circulation of anesthetized dogs. R76 did not cause a significantly greater increase in CBF compared with nonionic materials in spite of causing significantly greater increases in osmolality of blood in the coronary sinus. Concomitant with the peak increase in CBF, the ionic materials caused sharp decrease in peak left ventricular (LV) systolic pressure and dp/dt, while the nonionic materials increased these major determinants of MVO2. In contradistinction to the effects on CBF, ionic contrast material caused substantially and significantly greater increase in femoral blood flow, compared with the nonionic materials. In conclusion, these studies infer that the increase in CBF with contrast materials involves both indirect vascular and metabolic actions, while the increase in FBF is due to a direct vascular action.
Animals↗