Brachial plexus: MR imaging with a dedicated phased array of surface coils.

A phased array of surface coils was constructed for magnetic resonance imaging in three different regions in the brachial plexus. Four-coil subsets of the six-coil array were activated at any given time during imaging in three volunteers. An in vivo estimate of the signal-to-noise ratio (S/N) at three locations in the brachial plexus indicated that the phased-array coil provided a signal-to-noise ratio that was three to six times higher than that of the body coil.

Surface coil phased arrays for high-resolution imaging of the carotid arteries.

An MR phased-array coil assembly was developed to obtain high-resolution images of atherosclerotic plaques in the carotid artery. Images of volunteers and patients obtained by using alternative coil designs provided a subjective assessment of the coils' performance, field of view, ease of use, and susceptibility to motion artifacts. A quantitative measurement performed on a phantom indicated that a two-coil phased-array design should produce a 37% better signal-to-noise ratio at the carotids than would a conventional single 3-inch surface coil.

Prospective evaluation of echocardiography for primary rejection surveillance after infant heart transplantation: comparison with endomyocardial biopsy.

Rejection surveillance is critical to successful heart transplantation, and infant recipients have necessitated the use of noninvasive measures. The survival, incidence of rejection, and accuracy of echocardiography in predicting treatable rejection, as detected on right ventricular endomyocardial biopsy, were prospectively studied in infants. The survival rate (82%) and rejection rate (1.4 rejection episodes per 100 patient days) of infants who underwent transplantation during the study were comparable to other studies that used heart biopsy only. Echocardiography was 98% accurate at predicting biopsy results. The sensitivity of echocardiography was 92%, and the specificity was 98%. We conclude that echocardiography can be used successfully for primary rejection surveillance in infants and that right ventricular biopsy is infrequently required.

Temporal lobes: surface MR coil phased-array imaging.

The authors describe a four-coil surface phased-array coil for magnetic resonance (MR) imaging of the temporal lobes. On the basis of measurements in a phantom, the signal-to-noise ratio of the array is 1.67 times or more better than that obtained with a standard quadrature head coil in the region of the hippocampi. The higher sensitivity of this phased array permits use of imaging pulse sequences for which the head coil is inadequate.

Indications and contraindications for heart transplantation in infancy.

Heart transplantation uniquely offers infants with irreversible myopathies and complex congenital heart disease (CCHD) the potential for survival. Heart transplantation in the first year of life has an actuarial 1-year survival rate of 85%. Controlling for the variables that lead to perioperative death can improve 1-year survival rates to 95%. Mortality is also accrued before transplantation, with 15% to 20% of infants dying before a donor organ is available. Because of this cumulative mortality, an algorithm was developed to maximize pre- and posttransplantation survival and thus increase the likelihood that the limited donor supply would have the greatest impact. The risk factors considered in the algorithm include: (1) hemodynamic stability, (2) central venous access/prostaglandin requirements, (3) need for ventilator support, (4) pulmonary blood flow dependent on a critically restricted atrial septal defect, (5) risk for pulmonary hypertension, (6) anomalous pulmonary venous return, and (7) history of sepsis. Overall, patient survival would be maximized by only using transplantation for patients with CCHD who have moderate or less risk of pre- or posttransplantation death (< 20%). Donor organ utilization could be maximized by reserving transplantation for patients without options (myopathies) and for patients with CCHD who have a low predicted risk of death (< 10%). Because the risks of death at transplantation or in the first year after transplantation are low and relatively fixed, changes in risks of palliative surgery or donor availability can be easily used to adjust the decision algorithm.

Donor shortage: use of the dysfunctional donor heart.

The cause of brain death and the physiologic sequelae of brain death may impair heart function. Pharmacologic attempts to maintain donor viability may further jeopardize myocardial performance and could only be justified if dysfunctional donor organs subsequently prove to recover normal function after transplantation. Survival data on heart transplantation with organs donated from infants with sudden infant death syndrome indicate that prolonged ischemia (cardiopulmonary resuscitation up to 60 minutes) and metabolic abnormalities a priori do not increase the risk of graft failure. To provide a donor organ to infants in immediate peril, we have used donor hearts with documented dysfunction (left ventricular shortening fraction [LVSF] < 28%, wall motion abnormalities, and mitral regurgitation). The results of heart transplantation with use of dysfunctional donor hearts (n = 22, LVSF = 24.5% +/- 3%) were compared with donors with normal left ventricular function (n = 133, LVSF > 28%). Early death (< 30 days) was similar for the dysfunctional donor group (14%) and normal function donor group (11%). Postoperative inotropic support was equally frequent in both groups. Graft function on echocardiography was normal at 30 days after transplantation for both types of donor organs. We conclude that donor hearts with decreased left ventricular function (LVSF 15% to 28% and/or asymmetric wall motion), despite massive inotropic support, can function normally in the recipient. Significant donor mitral regurgitation was seen in grafts that ultimately failed after transplantation. Research into the reversible mechanisms of myocardial dysfunction associated with brain death could enlarge the donor pool.

Serial echocardiographic evaluation of cardiac graft rejection after infant heart transplantation.

The effects of cardiac graft rejection on infant myocardial function as assessed by echocardiography are largely unknown. To quantitate the myocardial response to rejection, serial echocardiographic studies were prospectively performed on 20 infants (less than 1 year of age at transplantation). Two-dimensional guided-M-mode tracings were digitized and quantified with a computer-assisted format. Rejection was diagnosed by clinical criteria, and 85% were graded as mild, that is without cardiac signs or symptoms. Echocardiographic analysis was blinded to rejection status, with studies available 4.2 +/- 2.9 days before rejection, on the day of rejection diagnosis, and 2.9 +/- 1.5 days after rejection treatment. Left ventricular mass increased acutely from 109% of predicted normal to 129% with rejection and decreased to 110% with therapy (p < 0.01). Left ventricular volume also tended to fall with rejection and increase with therapy. The left ventricular volume/mass ratio fell from 0.29 +/- 0.10 to 0.25 +/- 0.13 and increased to 0.37 +/- 0.15 (p < 0.05) with treatment. Systolic function was depressed by rejection as reflected in the posterior wall thickening fraction and velocity of wall thickening. Diastolic dysfunction was reflected in a decreased velocity of posterior wall thinning (-9.7 +/- 3.9 to -7.7 +/- 2.7 and recovery to -10.8 +/- 3.8 (1/second, p < 0.05) and depressed average velocity of cavity enlargement (41.2 +/- 9.6 to 36.4 +/- 8.9 and recovery to 40.7 +/- 8.6 mm/sec, p < 0.05). The utility of these echocardiographic measurements to predict rejection has not been prospectively compared with the endomyocardial biopsy.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac transplantation in infancy: donors and recipients. Loma Linda University Pediatric Heart Transplant Group.

To evaluate the role of orthotopic cardiac transplantation for infants with lethal cardiac disease, we reviewed the results from our first 25 patients. Data on the donors were also reviewed to define the characteristics of a successful cardiac donor. Patients had transplants between November 1985 and November 1988. Several primary cardiac diagnoses were indications for transplantation, including congestive cardiomyopathy, hypoplastic left-heart syndrome, and other types of native and postoperative complex congenital heart diseases. The ages ranged from birth to 7 months. Of 25 patients, 21 are still alive (84% survival rate) with follow-up from 4 to 40 months. No late deaths have occurred. Long-term immunosuppression was accomplished with cyclosporine and azathioprine. Rejection surveillance was performed noninvasively; only one child required an endomyocardial biopsy. Donors died from a variety of traumatic and metabolic causes, including sudden infant death syndrome. The majority (72%) of donors had a history of cardiac arrest requiring cardiopulmonary resuscitation. One third were receiving inotropic support at the time of cardiac evaluation. We conclude that orthotopic cardiac transplantation is an effective therapy for infants with lethal heart disease. A larger donor pool is required, and many dying infants, despite cardiac arrest and resuscitation, would be suitable donors.