A new, rapid magnetic resonance (MR) imaging method, cine MR imaging, was used to determine the regurgitant fraction (RF) in patients with left-sided regurgitant lesions. Right and left ventricular stroke volumes were determined with cine MR imaging and a modified Simpson formula in ten healthy volunteers and 23 patients known to have either predominant mitral (n = 17) or aortic (n = 6) regurgitation. RFs evaluated at cine MR imaging were compared in healthy persons and patients with mild, moderate, or severe regurgitation demonstrated at angiography (n = 10) and Doppler echocardiography (n = 13). Cine MR imaging depicted regurgitant blood flow in all 29 regurgitant lesions in 23 patients as areas of low signal intensity within the regurgitant chamber. The RF was 4% +/- 7% in healthy subjects and 12% +/- 12% in those with mild, 35% +/- 14% in those with moderate, and 63% +/- 5% in those with severe regurgitation. The RFs determined by two observers were similar.
SUMMARY As echocardiography is being used more often, its value and accuracy are becoming more fully appreciated. Coincident with wider application of this imaging technique is the potential for identifying normal anatomic variants and their possible erroneous interpretation as pathologic states. In this report we describe the M-mode and two-dimensional echocardiographic features of a congenital remnant known as the Chiari network. This structure can present as a highly mobile, highly reflectant echo target that can be seen in several locations in the right atrium. We report here an index case that could be well examined echocardiographically and that was a cause of considerable concern due to the presence of congestive heart failure and a history of staphylococcal endocarditis. The presence of the Chiari network was confirmed pathologically. Subsequently, we found similar echocardiographic findings in 19 of 1248 patients (1.5%) studied in our laboratory. This congenital remnant, which is found pathologically in 2-3% of normal hearts, could be confused with valve disruption, vegetation or other mass lesion, particularly when associated with a suggestive clinical situation.M-MODE and two-dimensional echocardiography have gained wide acceptance for providing safe, repeatable and accurate diagnostic information in a variety of complicated clinical situations. Suspicion of valvular heart disease, particularly infection of the valves, represents an important indication for echocardiographic examination.1 2 Increasing experience with these techniques has allowed a better, and in some cases new, appreciation of normal and abnormal cardiac anatomy, motion and structural relationships.3 These include structures often described at cardiac surgery or at postmortem examination, but not previously demonstrable in ambulatory patients. We describe the echocardiographic appearance of the Chiari network, a not uncommon anatomic finding that might be considered a "normal variant."4 This structure, particularly in the setting of fever, congestive heart failure, pulmonary infiltrates and a history of i.v. drug abuse, could be mistaken for evidence of active infection or disruption of normal right-sided structures, possibly requiring urgent cardiac surgery. Materials
Magnetic resonance imaging (MRI) was conducted with use of the spin-echo technique (0.35 Tesla) in 22 patients with a variety of congenital and cardiovascular anomalies and in 16 normal volunteers. Electrocardiographic (ECG) synchronization of the data acquisition produced transverse, parasagittal, and coronal tomograms that were used to define size and relationship of the great vessels and internal cardiac structures. MRI findings were corroborated by angiography and sector-scan echocardiography. In most patients the diagnosis had been established before the MRI study. MRI detected all of 11 abnormalities at the level of the great vessels, all of six atrial septal abnormalities, and 10 of 11 ventricular septal defects. Images of poor quality resulting from patient motion were obtained in the one instance in which a small ventricular septal defect was not imaged. Magnetic resonance imager and imaging techniques. The magnetic resonance imager for this study uses a superconducting magnet operating at a field strength of 3.5 kG and a resonance frequency for hydrogen of 15 MHz. This imager has been described in detail previously.5 A multiple-plane selective irradiation technique was used for data acquisition and sectional (plane) images were reconstructed by the two-dimensional Fourier transform technique. The reconstruction matrix was 128 horizontal pixels and was displayed in 256 gray levels, with the brightest area representing the tissues with the greatest magnetic resonance signal intensity. Spatial resolution was 1.6 mm.The imaging sequence was spin echo at echo delay times (TE) of 28 and 56 msec. The repetition rate (TR), or interval between sets of radiofrequency pulses, was determined by each subject's heart rate and the decision by the operator of whether to initiate a sequence for every heartbeat or for alternating heartbeats. In all subjects images gated to every heartbeat were obtained.Data for each sectional image were acquired during 512 cycles. Total imaging time varied from 5.1 to 8.5 min; this was determined by the product of the R-R interval of the electrocardiogram, the number of lines along the y (vertical) axis of the reconstruction matrix, and the number of times the signal was averaged (four in the current study). Multisectional
Seventy-two patients (aged 2 months to 75 years; mean 23 years) with a variety of congenital anomalies of the heart and great vessels underwent ECG-gated magnetic resonance (MR) imaging using the multisectional spin-echo technique (0.35 Tesla). The ability to define segmental anatomy and intracardiac anomalies on transverse, sagittal, and coronal images was evaluated. MR images were graded as excellent, diagnostic, or nondiagnostic, and MR findings were corroborated by angiography and/or two-dimensional echocardiography. Studies that were considered to be excellent or diagnostic were obtained in 96% of the cases. Visceroatrial situs, the type of ventricular loop, and the relationship of the great vessels could be identified in all patients with studies encompassing the entire heart. Forty-four of 47 abnormalities at the level of the great vessels were identified with MR, including coarctation of the aorta and vascular rings. MR showed 32 of 35 ventricular abnormalities; 2 small ventricular septal defects and 1 Ebstein anomaly were not demonstrated. All of the abnormalities at the atrial level and those of systemic and pulmonary venous return were seen on MR images. Complex cardiac anomalies, such as single ventricles, and the status of the pulmonary arteries were clearly demonstrated, and a good assessment of total and palliative postoperative anatomy was provided.
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