CT and MR imaging of benign primary cardiac neoplasms with echocardiographic correlation

Benign primary cardiac neoplasms are rare but may cause significant morbidity and mortality. However, they are usually treatable and can often be diagnosed with echocardiography, computed tomography (CT), or magnetic resonance (MR) imaging. Myxomas typically arise from the interatrial septum from a narrow base of attachment. Fibroelastomas are easily detected at echocardiography as small, mobile masses attached to valves by a short pedicle. Cardiac fibromas manifest as a large, noncontractile, solid mass in a ventricular wall at echocardiography and as a homogeneous mass with soft-tissue attenuation at CT. They are usually homogeneous and hypointense on T2-weighted MR images and isointense relative to muscle on T1-weighted images. Paragangliomas usually appear as large, echogenic left atrial masses at echocardiography and as circumscribed, heterogeneous masses with low attenuation at CT. These tumors are usually markedly hyperintense on T2-weighted MR images and iso- or hypointense relative to myocardium on T1-weighted images. Cardiac lipomas manifest at CT as homogeneous, low-attenuation masses in a cardiac chamber or in the pericardial space and demonstrate homogeneous increased signal intensity that decreases with fat-saturated sequences at T1-weighted MR imaging. Cardiac lymphangiomas manifest as cystic masses at echocardiography and typically demonstrate increased signal intensity at T1- and T2-weighted MR imaging. Familiarity with these imaging features and with the relative effectiveness of these modalities is essential for prompt diagnosis and effective treatment.

Influence of ventricular morphology on outcome after the Fontan procedure

The modified Fontan procedure has gained wide acceptance in the treatment of various congenital heart defects. Determination of risk factors for mortality remains an important issue for optimizing patient selection for the Fontan procedure. Conflicting results have been reported about whether ventricular morphology is a risk factor in these patients. Survival free of Fontan takedown or cardiac transplantation was assessed in the first 500 patients undergoing the Fontan procedure at our institution. This survival was correlated with ventricular morphology as evaluated by angiography. Both multivariate and univariate analyses indicated ventricular morphology was predictive of early survival free of Fontan takedown or cardiac transplantation following the procedure. However, there was no statistical evidence for ventricular morphology being a risk factor for mortality in patients alive 6 months after the procedure. Ventricular morphology is a risk factor for early survival in patients undergoing a Fontan procedure, with left ventricular morphology associated with a better early survival than right ventricular morphology.

Telemedicine consultations in congenital heart disease: assessment of advanced technical capabilities

OBJECTIVE

To assess the value of adding remote pointer and dynamic display capabilities to a telemedicine system designed to provide consultative services for patients with congenital heart disease.

MATERIAL AND METHODS

Independent observations by the referring physician and the consulting physician provided the data for the assessment. Fifty-four teleconsultations involving 38 patients with 21 different congenital heart diseases were analyzed. The teleconsultations were based on previously obtained cineangiograms that were digitized and then transmitted by combined satellite and terrestrial-based technology. The observations, recorded by each physician at his workstation at the time of each teleconsultation, were summarized and analyzed statistically.

RESULTS

In 108 observations, the pointer was believed to be helpful in 72 (67%), and dynamic display was helpful in 96 (89%).

CONCLUSION

This study suggests that use of a pointer and dynamic display enhances teleconsultations for patients with congenital heart disease.

Cardiac transplantation for end-stage congenital heart defects: the Mayo Clinic experience. Mayo Cardiothoracic Transplant Team

OBJECTIVE

To review the outcome of cardiac transplantation undertaken in patients with congenital heart defects.

MATERIAL AND METHODS

Between November 1991 and March 1998 at our institution, cardiac transplantation was performed in 16 patients with congenital heart disease (age range, 3 to 57 years; mean, 26.1). Preoperative diagnoses included univentricular heart (N = 4); complete transposition of the great arteries (N = 3); Ebstein's anomaly (N = 2); tetralogy of Fallot (N = 2); levotransposition (N = 2); dextrocardia, corrected transposition, ventricular and atrial septal defects, and pulmonary stenosis (N = 1); double-outlet right ventricle (N = 1); and hypertrophic obstructive cardiomyopathy (N = 1). All patients had undergone from one to five previous palliative operations.

RESULTS

Four patients required permanent pacemaker implantation during the first month postoperatively because of bradycardia; more than 2 years later, another patient required a permanent pacemaker because of sick sinus syndrome. In addition, one patient had an automatic implantable cardioverter-defibrillator. Three patients required reconstruction of cardiovascular structures with use of prosthetic material (Teflon patches or donor tissue) at the time of cardiac transplantation. Actuarial 1-, 2-, and 5-year survival was 86.2 +/- 9.1%. During the first year after transplantation, two deaths occurred--one at 41 days of putative vascular rejection and the second at 60 days of severe cellular rejection. All other patients are alive and functionally rehabilitated; the mean follow-up period has been 26.1 months (range, 2 to 89.6).

CONCLUSION

Cardiac transplantation for patients with congenital heart disease can be accomplished with a low perioperative mortality and an excellent medium-term survival despite the challenges presented by the technical difficulties during invasive diagnostic procedures and at operation and the need for adherence to long-term multiple-drug therapy in this patient population.

Coarctation of the aorta: collateral flow assessment with phase-contrast MR angiography

OBJECTIVE

The purpose of this report is to describe a new use of MR imaging in coarctation of the aorta. The specific question addressed was how well collateral blood flow in intercostal arteries, as determined by phase-contrast MR angiography, correlated with findings during surgery or catheterization in patients with coarctation of the aorta.

CONCLUSION

Phase-contrast MR angiography is an excellent technique for detecting the presence or absence of collateral blood flow in the intercostal arteries of patients with coarctation of the aorta. Knowing whether collateral blood flow is present in patients with narrowing of the juxtaductal aorta should help assess the clinical hemodynamic significance of the coarctation.

Transesophageal echocardiography: unusual case of anomalous pulmonary venous connection to the azygos vein

Partial anomalous pulmonary venous connection, a rare congenital anomaly, most commonly involves the right lung, with one or more pulmonary veins anomalously connecting most frequently to the superior vena cava and less commonly to the right atrium or inferior vena cava. This article describes an unusual case of anomalous pulmonary venous connection of the right lung to the azygos vein in an adult. This anomaly was clearly delineated with angiography, computed tomography of the chest, and transesophageal echocardiography. The transesophageal echocardiographic features of the anomaly are described as a means to prevent further diagnostic misinterpretation.

The Fontan procedure for pulmonary atresia with intact ventricular septum: operative and late results

OBJECTIVES

The goals of the study were to evaluate the operative and late mortality associated with the Fontan procedure in patients with pulmonary atresia and an intact ventricular septum and to obtain follow-up information on the current clinical status of surviving patients.

BACKGROUND

Between 1979 and October 1, 1995, 40 patients with the anomaly had a nonfenestrated Fontan procedure performed at the Mayo Clinic. Because there are no previously published reports involving a series of this size in which the Fontan approach was used for this condition, a review of patient outcomes was thought to be of value.

METHODS

The medical records of the 40 patients were reviewed retrospectively, and 34 were determined to be alive. The status of the survivors as of late 1995 was then ascertained by direct examination, questionnaire or telephone follow-up.

RESULTS

There were three operative deaths and three late deaths. The current ages of the 34 survivors ranged from 4 to 30 years (median 13). Thirty-three of the 34 survivors were thought to be in New York Heart Association functional class I or II, and all but three of these patients, of school age or older, were either full-time students or working full time. The three adults who were not employed thought they were capable of working but were not doing so because of socioeconomic reasons. More than half of the patients were not receiving cardiovascular medications.

CONCLUSIONS

These overall gratifying early and late results encourage continued application of this operation for appropriately selected patients with this complex congenital cardiovascular anomaly.

Angiographic determination of ventricular morphology: correlation with pathology in 36 hearts with single functional ventricles

Among 36 patients with univentricular atrioventricular connections, 27 had left ventricular and 9 right ventricular morphology. None had a common or indeterminate ventricle on autopsy review. Angiographic analysis correctly determined ventricular morphology in 34 (94%) of 36 patients. All 9 patients with right ventricular morphology of the dominant ventricular chamber were correctly identified angiographically. Altogether 25 of 27 patients (93%) with left ventricular morphology of the dominate ventricular chamber were correctly identified angiographically. Two patients with left ventricular morphology and severely dilated ventricles were incorrectly classified as having right ventricular morphology by angiographic assessment. For patients with a single functional ventricle, we conclude that angiographic assessment is an excellent method for determining ventricular morphology.

Dynamic MR digital subtraction angiography using contrast enhancement, fast data acquisition, and complex subtraction

A dynamic MR angiography technique, MR digital subtraction angiography (MR DSA), is proposed using fast acquisition, contrast enhancement, and complex subtraction. When a bolus of contrast is injected into a patient, data acquisition begins, dynamically acquiring a thick slab using a fast gradient echo sequence for 10-100 s. Similar to x-ray DSA, a mask is selected from the images without contrast enhancement, and later images are subtracted from the mask to generate angiograms. Complex subtraction is used to overcome the partial volume effects related to the phase difference between the flowing and stationary magnetization in a voxel. Vessel signal is the enhancement of flow magnetization resulting from the contrast bolus. MR DSA was performed in 28 patients, including vessels in the lungs, brains, legs, abdomen, and pelvis. All targeted vessels were well depicted with MR DSA. Corresponding dynamic information (contrast arrival time ta and duration of the arterial phase tav) was measured: ta/tav = 3.4/4.7 s for the lung, 10.3/4.9 s for the brain, 12.8/19.3 for the aorta, 15.2/12.6 s for the leg. MR DSA can provide dynamic angiographic images using a very short acquisition time.

Successful resection of thoracic aortic aneurysms in Wiskott-Aldrich syndrome

A 23-year-old man with Wiskott-Aldrich syndrome, chronic aortitis, and severe aneurysmal dilatation of the thoracic aorta successfully underwent two-stage graft replacement of the ascending and descending thoracic aorta. Nine years postoperatively, he is asymptomatic and employed full time.

Error in MR volumetric flow measurements due to ordered phase encoding in the presence of flow varying with respiration

Respiratory ordered phase encoding is often employed in MRI studies to reduce image artifacts due to breathing motion. The purpose of this work was to evaluate error caused by the use of respiratory ordering of phase encoding in MR cine phase-contrast (CPC) volumetric flow measurements when the flow rate is sensitive to respiration. It was hypothesized that this effect is due to the systematic biasing of a respiratory-induced phase modulation function in k-space. A theoretical model for the effects of respiration was developed and then tested in flow phantom studies and in normal volunteer studies. In phantom experiments, the use of respiratory ordering induced an error of as much as 13% in CPC volumetric flow measurements. In preliminary volunteer studies, error was as high as 26% in superior vena cava flow measurements versus less than 1% error in the ascending aorta. It is concluded that a potential for error exists in CPC volumetric flow measurements obtained with the use of respiratory ordering schemes. Volunteer studies with larger numbers are warranted. Clinical applications in which this effect may be important include flow measurements in vessels subject to variations in flow due to respiration, such as the venae cavae, pulmonary vasculature, and portal vein.

Outcome of pulmonary and aortic homografts for right ventricular outflow tract reconstruction

To determine late patient outcome and homograft durability, we reviewed 326 patients who received aortic (n = 230) or pulmonary (n = 118) cryopreserved homografts for right ventricular outflow reconstruction between January 1985 and October 1993. Patient survival, including operative mortality, 5 years after the operation was similar between the two groups (pulmonary homograft 86%, aortic homograft 80%; p = not significant by log-rank test). However, 5-year freedom from homograft failure was significantly better for pulmonary homografts (94% versus 70%, p < 0.01 by log-rank test). Late calcification was evaluated by chest roentgenography and echocardiography. Overall, 20% of aortic homografts became moderately or severely calcified compared with 4% of pulmonary homografts (p < 0.01). Twenty-six percent of aortic homografts in children 4 years old or younger had moderate or severe obstruction associated with calcification, whereas only 11% of aortic homografts in patients over 4 years of age had calcific obstruction (p < 0.01). No late deaths among patients receiving pulmonary homografts were related to graft failure; two late deaths in the aortic homograft group were homograft related. Risk factors for patient mortality and homograft failure (defined as either need for homograft replacement because of homograft failure or as homograft-related death) were identified by the Cox multivariate analysis. Aortic type of homograft was a significant risk factor for homograft failure (p < 0.0001), but type of homograft was not correlated with patient mortality. Age 4 years or younger was a significant risk factor for both mortality (p < 0.01) and homograft failure (p = 0.03) in aortic homograft recipients but not in pulmonary homograft recipients. These results indicate that both aortic and pulmonary homografts provided excellent intermediate-term patient survival after right ventricular outflow tract reconstruction, but pulmonary homografts are more durable than aortic homografts with less calcification and obstruction, especially among children 4 years old or younger.

Therapeutic implications of intraoperative pressure measurements after the Fontan operation

Central venous pressure (CVP) and left atrial pressure (LAP) were monitored continuously for the first 72 hours postoperatively in 32 patients who underwent a Fontan operation in whom preoperative measurements of the pulmonary artery index were available. Integrated mean values were generated for each patient for the following time frames: (1) the first 12 hours after operation, (2) the first 24 hours after operation, (3) postoperative day 2, and (4) postoperative day 3. We found no difference in the CVP, LAP, or transpulmonary gradient, derived as CVP-LAP, measured in the operating room at the completion of the operation versus that measured on the third postoperative day: CVP, 18 +/- 2 mmHg versus 19 +/- 3 mmHg; LAP, 10 +/- 2 mmHg versus 10 +/- 3 mmHg; and transpulmonary gradient, 8 +/- 2 mmHg versus 8 +/- 2 mmHg. The combined incidence of hospital mortality and postoperative takedown associated with the Fontan repair was 12.5%. These findings suggest that a poor hemodynamic result from the Fontan operation can be predicted from intraoperative pressure measurements, because the CVP, LAP, and transpulmonary gradient are unlikely to change significantly in the early postoperative period. Therefore, a decision to take down or fenestrate the repair can reasonably be made in the operating room or the early postoperative period.

Coronary artery anatomy in complete transposition of the great arteries

Knowledge of the variations in coronary artery pattern is important in the arterial switch operation for complete transposition of the great arteries (TGA). As autopsy specimens provide the most definitive means of identifying the coronary anatomy, 255 hearts with complete TGA were reviewed by a single pathologist. The age of the patients ranged from 1 day to 34 years (mean, 2.9 years). The origin of the coronary arteries was defined as seen by an observer looking from the pulmonary artery toward the aorta. The usual pattern with the right coronary artery originating from the right hand sinus and the left coronary artery from the left hand sinus (184 cases) and the circumflex coronary artery arising from the right coronary artery (46 cases) accounted for 90% of the cases. Eleven other patterns were identified. The usual coronary artery pattern was more prevalent in TGA with the aorta in a right anterior or anterior position (74.8%) than in TGA with a side-by-side relationship of the great arteries (38.9%). In only 2 cases (0.8%) was an aortic intramural course of the left coronary artery identified. The latter 2 cases confirm our belief that an aortic intramural course of the left coronary artery or the left anterior descending coronary artery must be assumed when the vessel has an aberrant origin from the right sinus or when it is in intimate relationship with the commissure between the right and left sinuses and courses between the great arteries. In the vast majority of specimens a favorable coronary artery pattern with regard to feasibility of the arterial switch operation was encountered.

Imaging strategies for vascular rings

Thirty-nine patients have undergone operation for relief of tracheoesophageal compression resulting from vascular rings and related entities at the Mayo Clinic. Nineteen patients had a double aortic arch, 11 patients had a right aortic arch with an aberrant left subclavian artery, 5 patients had a left aortic arch with an aberrant right subclavian artery, 2 patients had a pulmonary artery sling, 1 patient had a right aortic arch with mirror-image branching and a left ligamentum arteriosum, and 1 patient had a left aortic arch, a right descending aorta, and a right ductus arteriosus. Diagnostic examinations included chest radiography, barium esophagography, angiography, and, more recently, transthoracic echocardiography, computed tomography, and magnetic resonance imaging. A comparison among the various diagnostic techniques used in 12 patients during the last 12 years showed that angiography (n = 7), magnetic resonance imaging (n = 5), and computed tomography (n = 3) were the most reliable, as they always accurately delineated the anatomy. However, in the 6 patients who underwent transthoracic echocardiography, 1 of whom was an older child and 2 of whom were adults, the vascular abnormality was described correctly only once; in the other 5 patients, the results were false-negative or the technique failed to visualize the relevant vascular structures sufficiently. Currently, magnetic resonance imaging is our imaging technique of choice for the delineation of the vascular and tracheal anatomy in patients suspected of having a vascular ring.

Aortic intramural course of the left coronary artery in dextro-transposition of the great arteries

Three patients with dextro-transposition of the great arteries and an aortic intramural left coronary artery are described. A review of our patients with dextro-transposition of the great arteries and those reported in the literature suggests that an aortic intramural course of the left coronary artery or left anterior descending coronary artery must be assumed when the artery arises from the right (posterior) sinus of Valsalva, distal to the right sinotubular junction, or at the commissure between the right and left (anterior) sinuses and courses between the great arteries.

Preoperative diagnosis of coronary artery anatomy in dextrotransposition of the great arteries

BACKGROUND

Preoperative diagnosis of the coronary artery pattern in dextrotransposition of the great arteries is important because deviation from the usual pattern may influence the surgical strategy.

METHODS

For assessment of the value of angiography and echocardiography in this setting, we analyzed the preoperative echocardiographic and angiographic findings in 74 patients with dextrotransposition of the great arteries in whom an arterial switch operation was performed.

RESULTS

Two-dimensional echocardiography established a diagnosis of the coronary artery pattern in 40 of the 74 patients; that diagnosis was correct in 38-30 of 32 (94%) with the usual coronary artery pattern and 8 (100%) with an atypical pattern. Angiography established a diagnosis of the coronary artery pattern in 52 patients; that diagnosis was correct in 50-41 of 42 (98%) with the usual coronary artery pattern and 9 of 10 (90%) with an atypical pattern. The accuracy of echocardiography in diagnosing the coronary artery pattern in dextrotransposition of the great arteries in this series was 95% and that of angiography was 96%.

CONCLUSION

Both echocardiography and angiography can establish the diagnosis of the coronary artery anatomy in most patients. Echocardiography is routinely performed in infants with dextrotransposition of the great arteries and is proving to be increasingly sensitive for diagnosing the coronary artery anatomy; the role of angiography may evolve to be supplementary, especially in cases in which the coronary artery anatomy is not clearly demonstrated by echocardiography.

Radiation exposure and efficacy of exposure-reduction techniques during cardiac catheterization in children

OBJECTIVE

The purpose of this study was to measure radiation exposure levels in children undergoing cardiac catheterization. This information was used to assess methods of reducing exposure and to characterize total exposures.

SUBJECTS AND METHODS

The radiation exposure area product was determined for a total of 175 patients during three study intervals over 10 years. Examinations included biplane fluoroscopy and cineangiography for the diagnosis and treatment of congenital heart disease.

RESULTS

The use of pulsed progressive fluoroscopy was found to reduce patients' fluoroscopic exposure rates by approximately 40% as compared with interlaced mode fluoroscopy. Combining exposures from the frontal and lateral projections, the median fluoroscopic time for diagnostic procedures was 21 min and the median time for cineangiography was 42 sec. Median total exposure area product was 2063 R-cm2 with cineangiography accounting for 44% of the total exposure. For an estimated X-ray beam entrance area of 50-100 cm2, the median total entrance exposure was in the range of 20-40 R. Fluoroscopy times for interventional procedures were found to be 1.5 to 2.5 times longer than for diagnostic procedures, with total exposures approximately three times higher.

CONCLUSION

This study suggests that pulsed progressive fluoroscopy is an effective method of reducing radiation exposure in children undergoing cardiac catheterization.

Surgical treatment of vascular rings: the Mayo Clinic experience

From 1947 through 1992, 37 Mayo Clinic patients underwent operation for the relief of tracheoesophageal obstruction that resulted from vascular rings and related entities. Of the 37 patients, 18 had a double aortic arch, 11 had a right aortic arch with an aberrant left subclavian artery, 4 had a left aortic arch with an aberrant right subclavian artery, 2 had a pulmonary artery sling, 1 had a right aortic arch with mirror-image branching and a left ligamentum arteriosum, and 1 had a left aortic arch, a right descending aorta, and a right ductus arteriosus. Symptoms consisted of stridor, recurrent respiratory infections, and dysphagia. The anomaly was approached through a left thoracotomy in 31 patients, through a right thoracotomy in 4, and through a median sternotomy in 2. Only one early postoperative death (3%) and no late deaths occurred. At long-term follow-up (maximal duration, 45 years), three patients had residual symptomatic tracheomalacia, one of whom required right middle and lower lobectomy for recurrent pneumonia. Magnetic resonance imaging is the imaging technique of choice for accurate delineation of the vascular and tracheal anatomy. When patients are symptomatic, vascular ring should be repaired. The surgical risk is minimal, and the long-term results are excellent.

Modified Fontan operation in the presence of anomalies of systemic and pulmonary venous connection

BACKGROUND

The purpose of this report is to outline technical maneuvers dictated by anomalies of systemic and/or pulmonary venous connection in the performance of the Fontan procedure.

METHODS AND RESULTS

Between 1975 and 1990, 104 patients (60 male, 44 female) with anomalies of systemic and/or pulmonary venous connection underwent a modified Fontan procedure at the Mayo Clinic. Mean age was 9.7 +/- 5.7 years. Isolated anomalies of the systemic venous connection were identified in 46 patients, isolated anomalous pulmonary venous connections in 4, and a combination of the two in 54. Previous palliative operations had been performed in 93 patients. Surgical repair was accomplished by atrial septation or placement of an intra-atrial conduit combined with cavopulmonary anastomosis if required. Survival by Kaplan-Meier, including operative mortality, was 55.7% at 10.3 years, not significantly different from the overall survival of the Fontan population. By the proportional hazards general linear model procedure, insufficiency of the systemic atrioventricular valve, preoperative mean pulmonary pressure greater than 15 mm Hg, and pulmonary artery resistance index greater than 4 U.m2 were associated with higher mortality. Five patients required reoperation for pulmonary venous obstruction (1 patient), revision of the atrial baffle (1 patient), revision of the intra-atrial conduit (2 patients), and replacement of the systemic atrioventricular valve (1 patient).

CONCLUSIONS

We conclude that the modified Fontan operation can be successfully performed in this subset of patients, with long-term results comparable to those obtained in patients with normal systemic and pulmonary venous connection.

Congenital partial and complete absence of the pericardium

Between 1952 and 1991, 15 Mayo patients were found to have partial or complete absence of the pericardium at the time of a cardiovascular surgical procedure. One patient with complete absence of the left pericardium had symptoms possibly related to the pericardial abnormality. This 42-year-old man had severe insufficiency of the tricuspid valve attributable to chordal rupture of the anterior leaflet, possibly precipitated by complete displacement of the heart into the left pleural space. Excision of the ruptured chordae and plication of the anterior flail leaflet rendered a competent tricuspid valve. In two patients, a small defect in the pericardium was repaired. Three patients who underwent operation for complex congenital heart disease died: two early postoperatively and one late after a reoperation. In the other 12 patients, no early or late postoperative complications were encountered. Although rare and usually asymptomatic, complete and partial deficiency of the pericardium may lead to serious complications such as cardiac valvular insufficiency or incarceration of cardiac tissue.

Pulmonary artery size and clinical outcome after the modified Fontan operation

The maximum cross-sectional area of the central pulmonary arteries indexed to the body surface area (pulmonary artery index [PAI]) was measured preoperatively from angiograms in 173 patients evaluated for a Fontan-type operation between 1981 and June 1989. Of these, 34 patients underwent another palliative procedure, 8 primarily on the basis of small pulmonary arteries (PAI, 106 to 167 mm2/m2). The mean PAI of this group was significantly smaller than the mean PAI of the remaining 139 patients who underwent a Fontan operation (136 +/- 20 versus 310 +/- 113 mm2/m2) (p < 0.001). The patients who underwent a Fontan operation were evaluated according to three overlapping end points: (1) hospital death or takedown of repair (12.2%), (2) early failure (cumulative death or takedown of repair within 6 months of operation) (16.5%), and (3) early failure or persistent effusions (33.8%). With regard to these end points, no significant difference in pulmonary artery size could be found between patients having a favorable or unfavorable outcome. However, among a low-risk subset of 30 patients with tricuspid atresia, those with "early failure or persistent effusions" had significantly smaller pulmonary arteries than those with a good outcome (PAI, 185 +/- 47 versus 276 +/- 83 mm2/m2) (p < 0.01). The postoperative transpulmonary gradient of the 8 patients with the smallest pulmonary arteries who underwent a Fontan operation (all PAIs < 170 mm2/m2) was significantly greater than that of the rest of the study group (9.88 +/- 2.3 versus 8.13 +/- 2.3 mm Hg) (p < 0.04).(ABSTRACT TRUNCATED AT 250 WORDS)