Magnetic resonance imaging of restrictive cardiomyopathy.
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Adult↗
Biomedical subjects
M J Lipton
Publications and source records attributed to M J Lipton.
Cine computerized tomography.
Ultrafast (Cine) CT scanning provides cross-sectional millisecond tomography, and therefore combines digital imaging and high resolution without the need for either cardiac catheterization or any form of ECG gating. Fifty millisecond multilevel scanning at rates of 17 scans per second allows quantitation of left ventricular (LV) function at each tomographic level during a cardiac cycle. Calculations of global and regional ejection fraction can be obtained, and in addition ultrafast CT also has the potential for providing unique data concerning regional wall thickening, mass and even regional myocardial perfusion. Interventional studies with exercise and pharmacological agents have commenced and are currently being evaluated.
Cineradiography↗
Quantitation of left ventricular anatomy and function by ultrafast CT.
Ultrafast computed tomographic (CT) scanning provides cross-sectional millisecond tomography, similar in many ways to cineangiography. The technique, which combines digital imaging and high resolution without the need for cardiac catheterization, is rapidly being validated. Fifty millisecond scans at rates of 34/second allow quantitation of left ventricular function using typical calculations including global and regional ejection fraction but ultrafast CT also has the potential for providing unique data concerning regional wall thickening, mass, and even regional myocardial perfusion. Furthermore, interventional studies with exercise and pharmacological agents have commenced and are currently being evaluated.
Coronary Circulation↗
Use of ultrafast computed tomography to quantitate regional myocardial perfusion: a preliminary report.
The purpose of this study was to assess the potential for rapid acquisition computed axial tomography (Imatron C-100) to quantify regional myocardial perfusion. Myocardial and left ventricular cavity contrast clearance curves were constructed after injecting nonionic contrast (1 ml/kg over 2 to 3 seconds) into the inferior vena cava of six anesthetized, closed chest dogs (n = 14). Independent myocardial perfusion measurements were obtained by coincident injection of radiolabeled microspheres into the left atrium during control, intermediate and maximal myocardial vasodilation with adenosine (0.5 to 1.0 mg/kg per min, intravenously, respectively). At each flow state, 40 serial short-axis scans of the left ventricle were taken near end-diastole at the midpapillary muscle level. Contrast clearance curves were generated and analyzed from the left ventricular cavity and posterior papillary muscle regions after excluding contrast recirculation and minimizing partial volume effects. The area under the curve (gamma variate function) was determined for a region of interest placed within the left ventricular cavity. Characteristics of contrast clearance data from the posterior papillary muscle region that were evaluated included the peak myocardial opacification, area under the contrast clearance curve and a contrast clearance time defined by the full width/half maximal extent of the clearance curve. Myocardial perfusion (microspheres) ranged from 35 to 450 ml/100 g per min (mean 167 +/- 125). Two flow algorithms derived from characteristics of the contrast clearance curves showed a good correlation with regional myocardial flow determined by microspheres: the ratio of the peak myocardial opacification from baseline to the area under the left ventricular cavity curve (r = 0.7, p less than 0.001, SEE = 44.4 ml/min), and the ratio of the left ventricular cavity to posterior papillary muscle curve areas divided by the full width/half maximal contrast transit time in the region of the posterior papillary muscle (r = 0.82, p less than 0.001, SEE = 52.2 ml/100 g per min). The form of these two flow algorithms was derived from classical indicator dilution theory. In conclusion, indices derived from these data correlated well with regional myocardial perfusion in the posterior papillary muscle region of the dog as assessed by microspheres. This approach offers promise for the quantitation of regional myocardial perfusion and myocardial flow reserve in patients.
Algorithms↗
Measurement of renal blood flow by cine computed tomography.
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Animals↗
Lactate accumulation in ischemic- and anoxic-isolated rat hearts assessed by H-1 spectroscopy.
Proton magnetic resonance (MR) spectroscopy with homonuclear editing was used to assess lactate accumulation in ischemic and anoxic hearts perfused according to the Langendorff method. An increase in the lactate signal was observed after 5 minutes of ischemia and after 10 to 20 minutes of anoxia. This study demonstrates that proton MR spectroscopy can be used to monitor the time course of MR-visible lactate levels in ischemic and anoxic isolated rat hearts.
Animals↗
Magnetic resonance imaging of myocardial infarction using albumin-(Gd-DTPA), a macromolecular blood-volume contrast agent in a rat model.
Magnetic resonance (MR) contrast enhancement of acute myocardial infarction was studied in rats using albumin-(Gd-DTPA), a paramagnetic macromolecule with prolonged intravascular retention after intravenous injection. Histologic examination and distribution measurements of radiolabeled microspheres confirmed induction of regional myocardial infarction after ligation of the left coronary artery. ECG-gated spin-echo images at 2.0 Tesla, employing short, T1-weighted pulse sequence settings, demonstrated time-persistent and significant (P less than .05) enhancement of normal myocardium (66%) and an even greater enhancement of the infarcted area (100%), for as long as 60 minutes after injection of 160 mg/kg albumin-(Gd-DTPA). The contrast difference between normal and infarcted myocardium was increased significantly (P less than .05) after administration of albumin-(Gd-DTPA). The prolonged enhancing effects of albumin-(Gd-DTPA) on MR images are useful for evaluating regional differences in blood volume and capillary integrity between normal and infarcted myocardium.
Animals↗
Relative carotid blood flow measurements in dogs by high-speed CT. A preliminary study.
A high-speed computed tomography (CT) scanner was used for measuring flow in a phantom and in the common carotid arteries of six dogs. The general ability of the scanner to assess flow using contrast media boluses was tested with the phantom. The validated simple concept was then used in the animals. The carotid blood flow was varied with a distal occluder on one side and measured with electromagnetic flow probes in both vessels. The results are promising and demonstrate a good correlation between the high-speed CT findings and those measured with the flow probes.
Animals↗
Atrial-level shunts: sensitivity and specificity of MR in diagnosis.
Gated transverse cardiac magnetic resonance (MR) images from 31 patients with proved atrial septal defect (ASD) and from 33 control subjects were reviewed retrospectively by a panel of cardiac radiologists. The panel, by consensus, determined the presence and the type of ASD and assigned a confidence level for each diagnosis. A total of 97% of ASDs were correctly identified at high levels of specificity (primum, 100%; secundum, 96%; common atrium, 100%). Sensitivity and specificity are illustrated by receiver operating characteristic curves. Pulmonary veins were demonstrated at rates exceeding those reported for echocardiography. Further, all cases of anomalous pulmonary venous connection proved by angiography were also demonstrated by MR. Thus, MR has high sensitivity and specificity in the diagnosis and location of atrial-level shunts and is at least as accurate as, and possibly more accurate than, traditional techniques for the diagnosis of anomalous pulmonary venous connection.
Adolescent↗
Upper airway obstruction in infants and children: evaluation with ultrafast CT.
The diagnostic accuracy of ultrafast computed tomography (CT) was evaluated prospectively in 25 infants and children with suspected airway obstruction. All examinations were conducted in spontaneously breathing, nonsedated children. Scan acquisition times were 0.05 or 0.1 second. CT examinations, completed in an average of 10 minutes, routinely included localizing, contiguous sections through the trachea followed by serial images obtained at a rate of 17 per second through regions of interest. Imaging results were correct in 24 of 25 examinations as judged from clinical and surgical data. Ultrafast CT data permitted diagnosis of dynamic changes in airway caliber, small intraluminal polyps, focal tracheal atresia, compressive mediastinal masses, and foreign body obstructions of the major bronchi. Dose measurements showed a maximum skin exposure of 245 mR (0.06 mC/kg) per 0.05-second image. Ultrafast CT provides an accurate, minimally invasive method for dynamic imaging of the airway in nonsedated children.
Adolescent↗
Quantification of effect of pericardium on LV diastolic PV relation in dogs.
The aim of the present study was to quantify the effect of the pericardium on the left ventricular (LV) diastolic pressure-volume relation. The experiments were done in 10 anesthetized closed-chest dogs. Pericardial and cardiac volumes were determined by computed tomography. Pericardial effusion (n = 5) and volume loading (6% dextran iv; n = 5) were used to increase pericardial volume. Volumes were normalized as multiples of the LV volume measured when LV transmural pressure was 6 mmHg (VLV6). Using the data from the pericardial effusion experiments, we calculated the best-fit exponential equations for the pericardial pressure-volume relations. From these equations we calculated that the changes in pericardial volume necessary to shift the LV diastolic pressure-volume curve upward by 2, 5, 10, and 20 mmHg were 0.6 +/- 0.1, 1.1 +/- 0.2, 1.6 +/- 0.2, and 2.2 +/- 0.3 times VLV6, respectively. Using the data from the volume loading experiments, we also calculated the degree of upward shift of the LV pressure-volume relation caused by volume loading, which increased LV mean diastolic pressure by 12 mmHg. (The upward shift is that increment in pericardial pressure caused by the total increase in volume of the extra-LV contents of the pericardium, i.e., the atria, the right ventricle, and any pericardial effusion.) This volume loading increased the total volume of the right ventricle and the atria by 1.0 +/- 0.1 VLV6, which, in itself, increased pericardial pressure by 3.6 +/- 0.8 mmHg. We conclude that in situations in which heart or pericardial volume increases acutely, the pericardium shifts the diastolic pressure-volume relation of the LV upward by a significant amount.
Animals↗
Cine MR imaging: potential for the evaluation of cardiovascular function.
MR imaging is valuable in defining cardiac anatomy in a variety of cardiac abnormalities. However, evaluation of cardiac function by this technique has been limited by long imaging times and low temporal resolution. New, recently described pulse sequences shorten imaging time considerably and improve temporal resolution. This paper reports our early experience with cine MR imaging of the heart, a technique of gradient-recalled acquisition in the steady state (GRASS) that uses low flip angles and gradient-recalled echoes. Images were obtained in 36 subjects (14 normal volunteers and 22 patients with coronary artery or valvular heart disease) and displayed in a cinegraphic mode for assessment of cardiac function. The acquisition of 10 to 12 levels, covering the whole heart with up to 24 time frames per level, required a maximum imaging time of only 30 min. Because systole and diastole were readily identified, and the contrast between blood and surrounding structures was excellent, systolic wall thickening, wall motion, and motion of the cardiac valves were visualized easily. Regions of myocardial infarcts were clearly visible and characterized by lack of systolic wall thickening and/or diastolic wall thinning. Turbulence caused signal loss within the flowing blood, which usually had higher signal intensity than myocardium. Therefore, turbulent blood flow in valvular regurgitation and in valvular and subvalvular stenosis could be detected. Cine MR imaging is a promising new technique for the evaluation of myocardial and valvular function.
Adult↗
Computer tomography, positron emission tomography and nuclear magnetic resonance in cardiology.
Ultrafast CT scanning, due to short exposure time, high repetition rate and multiple projections, is well-suited for studies of the heart. A typical ultrafast CT study is composed of three different series of images: volume mode, flow mode and motion mode. With the equipment on this service, using volume mode and EKG triggering, a series of eight contiguous 1 cm-thick slices are generated within 240 ms with and without contrast medium. This imaging technique serves for localization of structures. In flow mode, EKG-triggered slices at multiple levels are generated after a bolus injection of contrast dye. Consequently, the passage of the contrast medium can be followed from the right to the left heart and the circulation time can be estimated, the knowledge of which is advantageous for planning of the subsequent motion study. On use of the motion mode, up to 17 slice images per second can be generated at four, six or eight levels during maximal contrast opacification of both ventricles. Possibilities for clinical application of fast CT scanning can be found in diseases of the aorta and pericardium, cardiac tumors and thrombi as well as for use in assessing cardiac chambers and wall thickness, temporal changes in wall thickness, regional wall motion impairment and quantification of cardiac output and shunt flow. Due to the short imaging time, the technique can also be used for exercise studies and to evaluate pharmacological interventions. According to preliminary results, myocardial blood flow can also be reliably quantitated. Coronary bypass grafts can be directly visualized after injection of contrast dye and, through use of the peak arrival time at various levels, information with regard to blood flow velocity as well as estimations of cross-sectional area in the grafts can be obtained. The sensitivity and specificity of assessment of patency of coronary bypass grafts is currently at approximately 95%.
Cardiac Volume↗
Evaluation of left ventricular thrombi by contrast-enhanced computed tomography and two-dimensional echocardiography.
Contrast-enhanced computed tomography (CT) was compared with 2-dimensional echocardiography (2-D echo) for evaluation of left ventricular (LV) thrombus. Thirteen patients with coronary artery disease who had LV thrombus initially documented by 1 of the 2 techniques were then studied with the other technique. The findings of the studies were concordant in 8 of 13 patients, with a similar description of the presence, location and size of the LV thrombus and associated regional LV wall abnormalities. In 5 of 13 patients, the 2 techniques produced discordant data. Of these, 2 patients had false-negative results on 2-D echo owing to poor visualization of the LV apex; 1 patient had a false-positive result on 2-D echo related to misinterpretation of a prominent papillary muscle; 2 patients had false-negative CT results, 1 related to insufficient contrast infusion. The findings demonstrate that CT is a useful technique for evaluating LV thrombus, and may be particularly helpful when 2-D echo is technically limited or equivocal.
Coronary Disease↗
Noninvasive evaluation of suspected thoracic aortic disease by contrast-enhanced computed tomography.
Traditionally, suspected thoracic aortic disease has been evaluated by aortography, which has associated risks because it is invasive. With the introduction of computed tomography (CT), a noninvasive alternative has become available. In the present retrospective study, the potential clinical value of CT in providing correct diagnoses and pertinent information required for current therapies is evaluated. For this purpose, results of CT in 200 patients examined for suspected thoracic aortic disease were compared with "hard" (surgical and autopsy findings) or "soft" (follow-up clinical information) evidence of the true diagnoses. Aortographic results, available in 51 patients (26%), were also compared with available clinical evidence. Excluding inadequate examinations, the diagnostic accuracy of the independently and blindly interpreted results of CT and aortography were similar (86% and 87%, respectively) in patients with true diagnoses confirmed by hard evidence. When patients evaluated for aortic damage from acute blunt chest trauma were also excluded, the accuracy was 90% for CT and 86% for aortography. Specifically, CT was 83% and 67% accurate in proved (i.e., confirmed by hard evidence) type A and type B dissections, respectively (75% for both type A and B by aortography). In the 183 patients suspected of having thoracic aortic disease not attributable to acute blunt chest trauma and with follow-up information, 91% would have been managed appropriately based on their CT evaluation alone. In the subset of patients who underwent aortographic evaluation as well, 91% would have been managed appropriately based on aortography alone. The accuracy for combined CT and aortography was 94%.(ABSTRACT TRUNCATED AT 250 WORDS)
Aortic Dissection↗
Invasive calcific constrictive pericarditis simulating a left ventricular mass.
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Calcinosis↗
Right-sided cardiac transplantation: importance of functional valves.
An original surgical procedure had been developed entailing the implantation of a right-sided heterotrophic cardiac graft in 14 dogs. The benchwork preparation included creation of both atrial and ventricular septal defects which allowed transplantation with the avoidance of extracorporeal circulation and the utilization of all transplanted myocardium and parts. The structure and function of this graft were sequentially evaluated using rapid cine-computed tomograms which permitted assessment of forward graft flow, ventricular wall contraction, and diastolic thickness for both the native and grafted hearts. These parameters were followed during the early (E) (less than 3 days), intermediate (I) (4-21 days), and late (L) (greater than 21 days) postoperative periods. Forward flow (E: 3.0, I: 1.5, L: 2.6) through the transplant was maintained by the competence of the implanted valves despite a progressive decrease in the contraction (E: 3.0, I: 1.3, L: 1.0) and associated decrease in the wall thickness (E: 3.0, I: 2.6, L: 2.4). These findings were consistent with severe cardiac graft rejection without immunosuppression. In summary, long-term structural and functional forward flow of this configurated right-sided transplantation had been maintained by the competent valves on both sides of the graft despite severe rejection without immunosuppression as documented by rapid cine-computed tomograms.
Animals↗
Quantitation of regional myocardial function by cine computed tomography: pharmacologic changes in wall thickness.
To determine the capability of high speed computed transmission tomography to quantitate regional wall thickening dynamics over a wide range of physiologic states, left ventricular wall thickening was studied in nine anesthetized mongrel dogs in the control state and during separate infusions of dobutamine (10 micrograms/kg per min) and phenylephrine (25 micrograms/kg per min). After an intravenous bolus of contrast medium the heart was imaged from base to apex with serial transverse images in eight short-axis cine computed tomographic planes. In each dog during each experimental condition, 50 ms scans spanning the cardiac cycle were acquired at each anatomic level. Left ventricular epicardial and endocardial boundaries were identified on end-diastolic and end-systolic images at the equatorial left ventricular planes by an objective threshold contour method validated in a series of experiments performed on ex vivo anatomic specimens. End-diastolic and end-systolic frames were automatically realigned by superposition of epicardial centers of gravity and then rotated using a cross correlation function. The left ventricular wall thickness was measured manually at 16 points around the circumference by two independent observers. For the group of dogs the average percent wall thickening was 40.5 +/- 28.2% and varied among segments from 18 to 70% in the control state. After dobutamine was administered, significant increases in heart rate and cardiac output (p less than or equal to 0.01) were accompanied by an increase in the average wall thickening (73.6 +/- 51.2%; p less than or equal to 0.001) in the left ventricle; the average wall thickening among segments ranged from 46 to 97%. After phenylephrine administration, significant increases in mean blood pressure and cardiac output (p less than or equal to 0.01) were noted along with a significant increase in average left ventricular wall thickening (60.3 +/- 52.5%; p less than or equal to 0.001). Despite an overall increase in the percent wall thickening, no statistically significant changes in segmental contraction pattern between control and drug intervention states were observed. The wall thickness measurements were highly reproducible between the two independent readers (reliability coefficient = 0.99). Cine computed tomography-derived measurements can potentially be used for quantitative assessment of left ventricular wall thickening dynamics of a single heartbeat during acute interventions, such as the administration of drugs.
Animals↗