Cynthia A. Miller

Early Results after Laparoscopic Gastric Bypass: EEA vs GIA Stapled Gastrojejunal Anastomosis

Background: Various surgical techniques have been successfully applied to isolated Roux-en-Y gastric bypass (RYGBP). Many surgeons rely on stapling devices for the gastrojejunal (GJ) anastomosis. Early follow-up results were compared for two laparoscopic techniques for GJ anastomosis: circular end-to-end (EEA) and linear cutting (GIA) staplers. Methods: Medical charts were retrospectively reviewed of all patients who had undergone stapled GJ anastomosis for isolated RYGBP over a 2-year period. The jejunal limb used for GJ anastomosis was fashioned at 1 cm / unit body mass index (BMI). Patients were grouped by GJ anastomotic technique, EEA or GIA, and the results compared. Results: 61 patients underwent RYGBP (EEA=32; GIA=29), with no differences in preoperative BMI or co-morbidities. Mean (±SD) operative time was shorter for the GIA group (EEA=180±56.1 minutes; GIA=145.3±27.9 minutes, P=0.003). There were 2 early re-operations in the GIA group for anastomotic leaks. Postoperative complications were not statistically different; however, there was an increased incidence of wound infections in the EEA group vs the GIA group (21.9% vs 6.9%, P=0.08). Follow-up at 6-8 months revealed an average percent excess weight loss of 46.7%±12.2% for EEA and 51.4%±10.7% for GIA (P=0.25). Length of stay, total hospital costs and operating-room costs were similar (P=0.34, 0.53 and 0.96 respectively). Conclusion: Operative time was significantly shorter in the GIA group. Complications, length of stay, weight loss and costs were similar between the groups. Selection of anastomotic technique may be based on surgeon preference, operative time, and potential for serious complications.

Results of mechanical ventricular assistance for the treatment of post cardiotomy cardiogenic shock

The voluntary submission of data on patients who receive mechanical circulatory assistance for post cardiotomy cardiogenic shock and acute myocardial infarction has resulted in an established data base for the ongoing evaluation of these devices. Since its inception in 1985, there have been 1,279 cases reported of implanted ventricular assist devices for post cardiotomy cardiogenic shock. The average duration of support for these devices is approximately 4 days. Those patients who underwent implantation of a centrifugal pump had significantly shorter periods of support when compared with the pneumatically supported group. Patients had similar periods of support when comparing clinical outcome. Approximately 70% of the reported cases underwent centrifugal assistance. The majority of reported cases were supported with isolated left ventricular assistance. There was no significant difference in overall outcome statistics when comparing type or mode of support. Approximately 45% of reported patients were weaned from circulatory assistance, and 25% of all patients survived to discharge. These numbers remain consistent with previously reported statistics. The results with acute myocardial infarction remain limited. Of the 96 reported patients, 26% were weaned from support and only 11.5% survived to discharge. This report continues to support the use and research for advancement of these devices toward the treatment of post cardiotomy cardiogenic shock.

Mechanical ventricular assistance: An economical and effective means of treating end-stage heart disease

BACKGROUND Heightened awareness of medical costs has escalated criticism toward expensive medical therapy. METHODS The use of ventricular assistance devices (VADs) at Pennsylvania State University as a bridge to transplantation was reviewed. Records of 43 patients listed as status 1 from July 1991 to July 1994 were compared. RESULTS This analysis demonstrated that for all patients treated with the intent to transplant, those who were bridged with a VAD exhibited a trend toward an improved transplantation rate (92% versus 68%) and a significantly greater rate of discharge from the hospital (92% versus 55.4%; p = 0.023) than the medically managed patients. Although overall charges and costs were higher in VAD-supported patients, this was related to significantly longer pretransplantation hospitalization. When normalized to daily costs and charges, this discrepancy in expenses was eliminated. CONCLUSIONS The superior rate of discharge at equitable daily costs and charges for the VAD patients draws continued enthusiasm toward use of these devices as a bridge to transplantation. Furthermore, development of outpatient care for VAD-supported patients and continued advances in the use of these devices may further reduce the cost of managing these critically ill patients.

Mortality of coronary artery bypass grafting before and after the advent of angioplasty

In an effort to determine whether the population of patients undergoing isolated coronary artery bypass grafting and the outcome of these operations have changed, we analyzed the records of two patient populations from our institution. Interventional cardiology techniques (angioplasty, thrombolysis) were not used at our institution before 1982. The records of 736 patients (group 1) who underwent isolated coronary artery bypass grafting from January 1975 to July 1981 were reviewed and compared with a group of 603 patients (group 2) who underwent operation from July 1985 to December 1987. The techniques of operation and myocardial preservation were virtually identical during the two periods. During the group 2 analysis period, 343 angioplasty procedures were performed. The patients in group 2 were significantly older, had increased preoperative New York Heart Association classification, had sustained more previous myocardial infarctions, and had more associated morbid medical conditions. There was a threefold increase in patients seen for reoperative revascularization procedures and a fourfold increase in emergency operations. Overall mortality, although not significantly different, did increase slightly from 2.69% in group 1 to 3.83% in group 2. Mortality after elective procedures remained essentially unchanged (2.05% for group 1 and 1.90% for group 2).

Pericardium as a thoracic aortic patch: Glutaraldehyde-fixed and fresh autologous pericardium

The repair of complex coarctation of the aorta often requires an aortic patch. Prosthetic patches lack growth potential and are associated with an increased incidence of aneurysm formation opposite the patch. We compared buffered glutaraldehyde-fixed patches, used in six animals (group 1), and untreated autologous pericardial aortic patches, used in five animals (group 2). Weanling pigs underwent pericardial patch replacement of a 1 X 2-cm diamond-shaped segment of the lateral wall of the descending thoracic aorta at the level of the aortic isthmus. Six months following patch aortoplasty, the animals were killed and the in situ patch dimensions were measured and compared to the measurements obtained at implantation. The increases in length, recorded as mean percentage change +/- SEM, were 34.7 +/- 3.7% for group 1 and 102.8 +/- 20.3% for group 2 animals; the increases in width were 91.4 +/- 31.7% for group 1 and 192.4 +/- 31.4% for group 2. The percentage changes for both length and width were significantly different between groups (P less than 0.05). Pull strength testing of standard-size patch samples demonstrated no significant difference in tensile breaking load between groups: group 1 = 959 +/- 277 g, group 2 = 795 +/- 86 g. Thoracic aortography revealed no evidence of stenosis or aneurysmal dilation in either group. Autologous pericardium is resilient, strong, and readily available and has expansile potential that makes it an ideal aortic patch material. We conclude that glutaraldehyde fixation does not provide additional strength and limits graft expansile potential when compared to untreated pericardium.

The mature and immature heart: Response to normothermic ischemia

Low cardiac output after heart surgery occurs more frequently in infants than in adults. This study was designed to determine whether this finding could be explained by a greater susceptibility of the immature heart to ischemia. An isolated working heart model was used to compare myocardial recovery in sets of hearts from six immature (2 weeks, 500 g) and six mature (20 weeks, 2 kg) rabbits after 10, 20, and 30 min of ischemia at 37 degrees C. Mean aortic pressure (MAP), aortic flow (AF), heart rate (HR), left atrial pressure (LAP), and ATP and glycogen levels were measured before and after ischemia. Hemodynamic results are expressed as the percentage recovery of preischemic values. ATP and glycogen are reported as micrograms per gram dry weight. After each period of ischemia, the immature hearts had superior recovery of AF (95 +/- 7.0, 72 +/- 8.8, 70 +/- 7.5 vs 58 +/- 7.1, 34 +/- 15.5, 13 +/- 9.1, P less than 0.05). After 10 min of ischemia, recovery of MAP was not different (97 +/- 1.5 vs 100 +/- 3.5), but after 20 and 30 min of ischemia, the immature hearts had better recovery of MAP (108 +/- 10.8, 98 +/- 5.4 vs 64 +/- 10.8, 48 +/- 6.0, P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Hemodynamic performance of carotid artery shunts

Although the use of shunts for carotid artery surgery remains controversial, the hemodynamics of the shunts currently available have not been carefully evaluated in vivo. We developed an animal model using contralateral carotid artery ligation, which produced ipsilateral carotid blood flows (640 +/- 44 ml/min) and internal carotid stump pressures (52 +/- 4 mm Hg) over a range commonly seen in carotid artery surgery. Seven shunts were tested and included Javid; 10F and 8F Brener; and 14F, 12F, 10F, and 8F Argyle shunts. The hemodynamic features evaluated for each shunt included maximum shunt flow, the pressure gradients occurring across each shunt, the increase in cerebral perfusion pressure over occlusion pressure associated with shunt placement, and the distal pressure pulse waveform. The larger diameter shunts were consistently better than the smaller diameter shunts. The correlation between shunt flow and the increase in distal pressure produced by shunt placement was high (r = 0.98, p less than 0.05), confirming that high flow rates maintained high perfusion pressure. By relating maximum shunt flow and the pressure gradient to the change in the pressure pulse contour for each shunt, it could be demonstrated that at the larger diameters, straight shunts displayed superior hemodynamic characteristics compared with tapered shunts, whereas at smaller diameters, tapered shunts were superior.

Results of aortic anastomoses made under tension using polydioxanone suture

After early repair of congenital cardiovascular defects, such as coarctation of the aorta, late stenosis may become a problem. Use of absorbable sutures has been shown to be superior to use of nonabsorbable sutures in allowing growth of an anastomotic site along with the individual. Some concern has been raised, however, about the potential for aneurysm formation at the site of anastomosis when absorbable sutures are used. This study was undertaken to observe the effects of longitudinal tension on anastomoses made with absorbable polydioxanone suture in growing animals. Six piglets (aged 3 to 4 weeks) underwent a 1-cm resection of the infrarenal aorta and reanastomosis with polydioxanone suture. One animal died prematurely of respiratory illness. The 5 remaining animals were killed after 6 months. The excised aortas demonstrated no stenosis, no dilatation, and no burst-test failure to 250 mm Hg. Histological examination showed disrupted elastic laminae without thinning of aortic wall in all samples of aorta. We conclude that polydioxanone suture is a suitable suture material for vascular anastomoses made under tension where growth of the anastomotic site is expected.

Myocardial oxygen consumption. Comparison between left atrial pulsatile synchronous and asynchronous bypass.

This controlled study was undertaken to quantitate the effect of R-wave synchronization (counterpulsation) on myocardial oxygen consumption (MVO2) as reflected by the tension time index (TTI) during pulsatile left atrial to aortic bypass. Pulsatile ventricular assist devices were implanted in eight anesthetized, fully hemodynamically instrumented animals. After baseline measurement of TTI, heart rate, cardiac output, mean aortic and left atrial pressures, pulsatile left atrial to aortic bypass was instituted. Measurements were then continuously recorded during both left atrial pulsatile synchronous (LAPS) and asynchronous (LAPAS) bypass periods of pumping. Heart rate and mean aortic pressure were controlled throughout the experiment. TTI = 1819 +/- 95 mmHg-sec (control); 987 +/- 127 mmHg-sec (LAPAS); and 763 +/- 89 mmHg-sec (LAPS). The results indicate TTI, and therefore MVO2, is reduced significantly from control levels by either LAPS or LAPAS bypass. However, R-wave synchronization (counterpulsation) offers no further benefit in reducing TTI over the less complex LAPAS or full-to-empty mode pumping.