G. Wesley Vick

Ventricular septal defect

Ventricular septal defects account for up to 40% of all congenital cardiac malformations. The diagnosis encompasses a broad range of anomalies, including isolated defects and those associated with other congenital cardiac malformations. Presentation, symptoms, natural history, and management of ventricular septal defects depend on size and anatomical associations of the anomaly, patients age, and local diagnostic and interventional expertise. In this Seminar, we describe the anatomical range of ventricular septal defects and discuss present management of these malformations. Genetic determinants, diagnostic techniques, physiological considerations, and management challenges are examined in detail. Unfortunately, in many circumstances, evidence on which to guide optimum management is scarce. We present some longer term considerations of ventricular septal defects in adolescents and adults, with particular emphasis on patients with raised pulmonary vascular resistance and Eisenmengers syndrome.

Evaluation of left ventricular wall motion, volumes, and ejection fraction by gated myocardial tomography with technetium 99m-labeled tetrofosmin: A comparison with cine magnetic resonance imaging

BackgroundWhether left ventricular function can be assessed accurately by gated single photon emission computed tomography (SPECT) in patients with myocardial infarction and severe perfusion defects is not well known.Methods and ResultsTwenty-five patients with an acute myocardial infarction underwent 99mTc-labeled tetrofosmin (99mTc-tetrofosmin) gated SPECT and cine magnetic resonance imaging (MRI). Wall motion was assessed in 13 left ventricular segments using a 5-point scoring system ranging from 3 (normal) to-1 (dyskinetic). Exact agreement for wall motion scores between gated SPECT and MRI was excellent (92%, kappa=0.82). Furthermore, correlations between the two techniques were also good for end-diastolic volume (r=0.81, P<.0001), end-systolic volume (r=0.92, P<.0001), and ejection fraction (r=0.93, P<.0001).ConclusionIn patients with a recent myocardial infarction, 99mTc-tetrofosmin gated SPECT provides reliable evaluation of global and regional ventricular function and volumes.

Assessment of tissue iron overload by nuclear magnetic resonance imaging.

PURPOSE The ability of stored intracellular iron to enhance magnetic susceptibility forms the basis by which tissue iron can be detected by nuclear magnetic resonance (NMR) imaging. We used this technique to assess myocardial, spleen, and liver iron content in patients with known or suspected iron overload disorders. PATIENTS AND METHODS Spin echo NMR images were obtained in 30 patients; 20 had chronic anemias treated by multiple blood transfusions, five had idiopathic hemochromatosis, and five had non-hemochromatotic liver disease with elevated serum ferritin levels and no stainable iron on liver biopsy. The acquisition of oblique images through the short axis of the left ventricle permitted assessment of left ventricular function, while demonstrating the liver and spleen on the same image. Iron content was assessed using a signal intensity ratio of organ (spleen, liver, or myocardium) to skeletal muscle. RESULTS In patients with multiple blood transfusions, iron content was highest in liver, followed by the spleen. Significant iron overload was detected in the myocardium of only one patient. Left ventricular systolic wall thickening was normal in patients receiving multiple blood transfusions. Two patients with treated idiopathic hemochromatosis had normal signal intensity ratios, and three untreated patients had evidence of significant deposits of iron in the liver and spleen as indicated by a reduction in signal intensity ratios (0.2 +/- 0.01 and 0.9 +/- 0.01, respectively). Five patients with non-hemochromatotic liver disease and high serum ferritin levels had normal signal intensity ratios by NMR imaging. CONCLUSION NMR imaging is a useful method of detecting tissue iron and distinguishing disease due to iron overload. Myocardial iron deposition is a late event, occurring after accumulation of iron in the spleen and liver.

Balloon dilation of unoperated coarctation of the aorta: short- and intermediate-term results.

Balloon dilation is effective in the immediate relief of obstruction due to unoperated coarctation of the aorta. However, the long-term benefits and complications of this procedure have not been established. Thirty-three patients underwent balloon dilation of unoperated coarctation using a percutaneous technique from November 1983 to December 1985. High quality biplane angiography was performed before and after dilation. Follow-up was obtained in 20 patients from 6 to 31 months following dilation. Angiography was performed at follow-up in 10, nuclear magnetic resonance (NMR) imaging in 10 and both NMR imaging and angiography in 3. Balloon dilation was successful in 31 of the 33 patients with a decrease in average systolic pressure gradient from 46 to 8 mm Hg. There was no significant change in gradient on follow-up physical examination and at recatheterization in 10 patients. In addition, there was no evidence of restenosis on follow-up angiography and NMR imaging. In two patients, a small aneurysm formed at the site of balloon dilation. Balloon dilation of unoperated coarctation is effective, providing lasting relief of coarctation gradient and no evidence of restenosis. However, because of the uncertain natural history of aneurysms after dilation, this procedure should be considered investigational until further follow-up on patients with and without an aneurysm is available.

Double balloon technique for dilation of valvular or vessel stenosis in congenital and acquired heart disease

Despite the generally excellent success with balloon dilation for the stenotic lesions of congenital and acquired heart disease, technical difficulties sometimes prevent satisfactory results. Such technical difficulties include: a large diameter of the anulus of the stenotic lesion relative to available balloon diameter, difficulty in the insertion or removal of the larger balloon catheters, and permanent damage to or obstruction of the femoral vessels by the redundant deflated balloon material of the large balloons. A double balloon technique was initiated to resolve these difficulties. With this method, percutaneous balloon angioplasty catheters were inserted in right and left femoral vessels, placed side by side across the stenotic lesion and inflated simultaneously. Dilation procedures using the two balloon technique were performed in 41 patients: 18 with pulmonary valve stenosis, 14 with aortic valve stenosis, 5 with mitral valve stenosis, 3 with vena caval obstruction following the Mustard or Senning procedure and 1 with tricuspid valve stenosis. Patient ages ranged from 1 to 75 years (mean 17.8) and patient weights ranged from 8.9 to 89 kg (mean 42.3). Balloon catheter sizes ranged from 10 to 20 mm in diameter. Average maximal pressure gradient in mm Hg before dilation was 61 in pulmonary stenosis, 68 in aortic stenosis, 21 in mitral stenosis, 12 in tricuspid stenosis and 25 in vena caval stenosis. Average maximal valvular pressure gradient after dilation was 13 in pulmonary stenosis, 24 in aortic stenosis, 4 in mitral stenosis, 0 in tricuspid stenosis, and 1 in vena caval stenosis. No major complications were encountered with the procedures.(ABSTRACT TRUNCATED AT 250 WORDS)

Electrocardiographic gating and monitoring in NMR imaging

ECG gating and monitoring during NMR imaging may be achieved reliably by applying the principles in this tutorial. In order to use the ECG signal both for triggering and for patient monitoring it must have a prominent R-wave, while at the same time must have little artifact from gradient switches or the Lorentz voltage across the aorta, and not be significantly distorted by gradient switching artifacts. The twin goals of no image artifacts and minimal ECG artifacts may be achieved by the following means: (1) using ECG electrodes with minimal metal, (2) selecting electrodes and cables with no ferrous metals, (3) placing the limb electrodes close together, (4) placing the line between the limb electrodes and the leg electrode parallel to the magnetic flux lines and, if possible, parallel to the transverse component of the gradient flux lines, (5) keeping the area between the limb electrodes and the leg electrode small, (6) placing that area in the center of the imager and (7) twisting or braiding the cables. Following these principles allows artifact-free images and reliable ECG monitoring during ECG-gated NMR imaging examinations.

Nuclear magnetic resonance imaging of the pulmonary arteries, subpulmonary region, and aorticopulmonary shunts: A comparative study with two-dimensional echocardiography and angiography

Twelve patients more than 8 years of age with complex congenital heart disease were evaluated prospectively with nuclear magnetic resonance (NMR) imaging and with echocardiographic and angiographic imaging techniques. The subpulmonary region, main pulmonary artery, right and left pulmonary arteries, and aorticopulmonary shunts were clearly visualized by means of NMR imaging in all patients. Angiography defined the subpulmonary region and main pulmonary artery in all patients, the right and left pulmonary arteries along their length in 11 of 12 patients, and aorticopulmonary shunts in seven of eight patients. Except for the right pulmonary artery, echocardiography defined the remaining structures in less than or equal to 50% of patients. Measurement of the pulmonary artery diameters on NMR images correlated well with the angiographic measurements of both the left (r = 0.96) and right (r = 0.94) pulmonary arteries. These results suggest that NMR imaging may be the preferable noninvasive imaging technique for defining the anatomy of the subpulmonary region, main and left pulmonary arteries, and aorticopulmonary shunts in older patients with congenital cardiovascular disease and that it compares well with the angiographic standard.

Pulmonary venous and systemic ventricular inflow obstruction in patients with congenital heart disease: Detection by combined two-dimensional and Doppler echocardiography

Obstruction to pulmonary venous return may be associated with a number of congenital cardiovascular abnormalities occurring both before and after surgery. Hemodynamic assessment by cardiac catheterization is often difficult. A noninvasive method for detection and quantitation of obstruction to systemic ventricular inflow would be clinically useful. Two-dimensionally directed pulsed and continuous wave Doppler echocardiography was performed before cardiac catheterization in 31 patients thought clinically to have possible obstruction to left ventricular inflow or pulmonary venous return. Primary diagnoses included transposition of the great arteries after the Mustard or Senning procedure in nine patients, total anomalous pulmonary venous connection in nine (in two after surgical repair), cor triatriatum in eight (in four after surgical repair), congenital mitral stenosis in four (in one after surgical repair) and mitral atresia in one. Severe obstruction was defined as a mean pressure gradient at catheterization of greater than or equal to 16 mm Hg at any level of the pulmonary venous return or of the systemic ventricular inflow. Severe obstruction was predicted if Doppler examination measured a flow velocity of greater than or equal to 2 m/s across any area of inflow obstruction. At catheterization, 12 patients (39%) had severe obstruction to left ventricular inflow or pulmonary venous return and all obstructions were correctly detected by Doppler echocardiography. The site of pulmonary venous obstruction was localized by two-dimensionally directed pulsed Doppler study. Patients with a lesser degree of obstruction had a lower Doppler velocity, but none had a maximal Doppler velocity of greater than or equal to 2 ms/s.(ABSTRACT TRUNCATED AT 250 WORDS)

Balloon expandable intravascular stents : aortic implantation and late further dilation in growing minipigs

Intravascular stents have been implanted in children with congenital and acquired vascular stenoses. Little information is known regarding the long-term results in growing patients, the implantation of multiple stents (in series), and the feasibility of further dilation. Nine stents were implanted in the abdominal aortas of 6 mini-pigs; in 3 pigs, 2 stents were implanted in series. Five pigs were recatheterized 196 +/- 17 days after stent implant. All stents were patent, with mild narrowing at the stent relative to the adjacent aorta; further stent dilation was performed. The stent diameter increased from 8.3 +/- 0.6 mm to 11.2 +/- 1.3 mm (p = 0.002), and the narrowing was relieved. These five pigs were catheterized 253 +/- 73 days after stent redilation. Each stent was patent without narrowing or pressure gradient. We conclude that intravascular stents do not interfere with normal growth, can be implanted in series, and can be further dilated.

Usefulness of nuclear magnetic resonance imaging for evaluation of pericardial effusions, and comparison with two-dimensional echocardiography.

Nuclear magnetic resonance (NMR) imaging clearly delineates cardiovascular structures without interference from overlying bone and lung tissue. The techniques of NMR imaging and echocardiography were compared in 26 patients with pericardial effusions, 10 of whom had associated pleural effusions. In those patients with fluid detected by both techniques, estimated size of the effusion tended to be somewhat larger by NMR. NMR imaging detected several small pericardial effusions that were not visualized by echocardiography. Both techniques demonstrated loculation well, although NMR imaging was better for detecting fluid located superiorly at the aortic pericardial reflection site, medially at the border of the right atrium and posteriorly at the left ventricular apex. In the 14 patients with documented exudative effusions (10 pericardial, 4 pleural) NMR signals of varying intensity were present in the effusion. One patient had a documented transudative effusion and no NMR signal was observed in the fluid. NMR imaging clearly distinguished pericardial from pleural effusions. NMR imaging is indicated when a suspected pericardial effusions is not detected by echocardiography or when specific localization or fluid characterization is desired.