The prevalence of venous thromboembolism of the lower extremity among thermally injured patients determined by duplex sonography.

BACKGROUND: Morbidity and mortality from venous thromboembolism (VTE) remains a significant problem for hospitalized patients. Despite the ample prospective literature defining the prevalence of VTE in hospitalized patient populations, the prevalence of VTE in the thermally injured population remains largely unknown. METHODS: We prospectively studied 148 thermally injured patients with hospital stays of greater than 3 days with lower extremity duplex ultrasonograms obtained at admission and discharge. RESULTS: Nine patients experienced VTE (6.08%). Eight of the nine deep venous thromboses were proximal. One of the two pulmonary embolisms was fatal. Treatment risk factors that were associated with VTE were the presence of a central venous line (p = 0.020) and transfusion of more than 4 units of packed red blood cells (p = 0.023). These treatment factors were significantly related to each other (p < 0.0001), to body surface area burned, and to intervention. CONCLUSION: The prevalence of VTE in burn patients is similar to that of moderate- to high-risk general surgical patients for whom VTE prophylaxis is recommended. VTE prophylaxis of burn patients, especially those requiring central venous lines and more than 4 units of packed red blood cells, should be considered.

Mesenteric revascularization in a contaminated abdomen: a case report.

The management of acute mesenteric ischemia in the contaminated abdomen may require the use of an autogenous graft to achieve mesenteric revascularization. The authors present a case of an ischemic small bowel perforation in a 62-year-old-woman whose preoperative angiogram demonstrated occlusion of the celiac, superior mesenteric, and inferior mesenteric arteries. Vein mapping of the right greater saphenous vein demonstrated a dual saphenous system whose individual diameters were more than 4 millimeters. Exploratory laparotomy revealed a diffusely ischemic small bowel and liver, as well as abdominal sepsis from the perforated small bowel. Revascularization was accomplished by using saphenous vein in a nonreversed orientation as a bifurcated conduit from the supraceliac aorta to the hepatic and superior mesenteric arteries. Following revascularization, the liver and small bowel immediately regained a normal perfused appearance and the perforated segment of small bowel was resected and reanastomosed. She returned for a follow-up clinic visit 5 months later and was found to have an asymptomatic 6 cm aneurysm involving the proximal mesenteric vein bypass. The aneurysmal aspect of the vein bypass was replaced with a polytetrafluoroethylene interposition graft originating from the supraceliac aorta. On follow-up 3 months later, her aortomesenteric bypass is patent without aneurysmal recurrence, and she is clinically asymptomatic from any symptoms of mesenteric ischemia.

Long-term follow-up and patient satisfaction after surgery for thoracic outlet syndrome.

The purpose of this study was to review the long-term outcomes, particularly patient satisfaction, of patients surgically treated for thoracic outlet syndrome (TOS). All patients who had undergone surgery for TOS at the University of Iowa Hospitals and Clinics between 1988 and 1999 were reviewed. A retrospective chart review of 29 patients (36 operations) was performed. In addition, 20 (69%) of the patients were able to be contacted for a phone survey. There was no operative mortality. Specific neurologic complications occurred in 4/36 operations (11%) including one brachial plexus traction palsy, two phrenic nerve palsies, and one long thoracic nerve palsy. All nerve palsies were either mild or temporary. Mean follow-up was 4 years. On phone survey, 80% of the patients were actively employed. Twenty-seven percent reported that they had an excellent result, 58% reported they had a good result, 8% reported that they had a fair result, and 8% had a poor result. If they had it to do over again, 85% of the patients would have the same surgery again for relief of TOS.

Contralateral internal jugular vein interposition for salvage of a functioning arteriovenous fistula.

Outflow obstruction in patients with hemodialysis access can cause venous hypertension and jeopardize the patency of the access site. Numerous surgical procedures have been described to decompress an occluded subclavian vein. In this report, we describe the use of the contralateral internal jugular vein as a bypass conduit to decompress an occluded brachiocephalic vein in a patient whose dialysis was dependent on this vein access.

A comparative evaluation of femorofemoral crossover bypass and iliofemoral bypass for unilateral iliac artery occlusive disease.

The purpose of this study was to compare the results of extra-anatomic femorofemoral crossover bypass grafting to the anatomic iliofemoral bypass grafting procedure in the treatment of patients with unilateral iliac artery occlusive disease with respect to patency and limb salvage. The records of all patients with unilateral iliac artery disease who underwent revascularization between January 1988 and December 1995 at the University of Iowa Hospitals and Clinics (UIHC) were retrospectively reviewed; 108 patients were identified and divided into two groups. Group I (n=68; male/female=44/24) was composed of all patients who underwent a femorofemoral crossover extra-anatomic bypass. All patients who underwent an iliofemoral anatomic bypass constituted group II (n=40; male/female=24/16). The mean age for group I was 60 years (range 28-87) and for group II, 54 years (range 14-86). The medical risk factors between both groups were comparable. Except for the higher incidence of gangrene in group II the indications for surgery were comparable between both groups. A polytetrafluoroethylene graft was used in 88% of group I patients and in 90% of group II patients (NS). In the remaining patients, an autogenous vein conduit was used. Two patients from group I (2.9%) died in the perioperative period (NS). Graft patency was assessed by clinical evaluation, Doppler-derived ankle/brachial indices, and color duplex imaging. The cumulative primary and secondary patency rates, limb salvage, and patient survival were calculated by use of life table analysis (SE<0.1). The need for simultaneous outflow and inflow procedures at the time of surgery was comparable between both groups. The proportion of patients who underwent further revascularization during follow-up was also comparable. The 5-year primary and secondary graft patency rates were 81.7% and 90.3%, in group I and 61.3% and 80.5% in group II. Although the difference between both groups was not significant there was a tendency toward higher rates with femorofemoral bypass. The 5-year survival rates of 80.3% for group I and 73.3% for group II were comparable. These data suggest that there is no significant difference in the long-term results between the femorofemoral crossover bypass grafts and iliofemoral grafts. Both procedures result in acceptable patency and limb salvage rates. The femorofemoral bypass is, however, more attractive, for it can be performed under local anesthesia if needed and does not involve the creation of the retroperitoneal incision necessary with the iliofemoral bypass.

Entering the ninth decade is not a contraindication for carotid endarterectomy.

The role of carotid endarterectomy (CEA) in stroke prevention is now better defined. However, its role in patients older than 79 years of age is controversial. This group of patients has been excluded in most clinical trials. In this study the authors reviewed their experience with CEA patients >79 years old. The records of all patients older than 79 years of age who underwent a CEA in a recent time period from January 1988 to December 1996 were retrospectively reviewed. Forty-one patients (31 men, 10 women) were identified by computer search. The indication for operation included transient ischemic attack in 12 (29.3%), amaurosis fugax in nine (22%), stroke in two (4.9%), and nonhemispheric symptoms in three (7.3%). Fifteen patients (36.6%) were asymptomatic. Medical risk factors included coronary artery disease in 26 (63.4%), hypertension in 22 (53.7%), and smoking in 12 (29.3%). The procedure was performed under EEG monitoring in all patients. General anesthesia was administered in 37 (90%) and regional anesthesia in four (10%). Shunts were used in four (10%) patients. The internal carotid artery was patched in 16 patients (39%). One patient (2.4%) developed a perioperative stroke and only one patient developed perioperative myocardial infarction (MI). None of the patients died within 30 days of surgery. In addition to the one MI case, five patients developed minor complications. The average length of time for stay after CEA was 3.4 days. Patients were followed up for an average of 20.7 months. Six patients died during follow-up. Four of those died from an MI and two from a stroke. The authors conclude that with proper selection of patients, CEA is safe in the octogenarian. Age alone should not be a contraindication for CEA.

Internal iliac revascularization during aortic aneurysm replacement: a review and description of a useful technique.

The coexistence of infrarenal aortic aneurysm and internal iliac artery aneurysm may represent a management problem with regard to preservation of the pelvic blood supply. In this article, we review the methods available for maintaining the pelvic blood flow and describe a useful technique that we have successfully utilized in seven patients to preserve the hypogastric artery blood flow.

Is color duplex surveillance of infrainguinal polytetrafluoroethylene grafts worthwhile?

BACKGROUND: Unlike vein bypasses, the role of duplex surveillance of infrainguinal prosthetic bypass grafts is controversial. The purpose of this study was to evaluate the adequacy of color duplex surveillance in identifying failing infrainguinal polytetrafluoroethylene (PTFE) bypass grafts and to assess its value in predicting continued bypass patency. METHOD: The surveillance data of primarily patent PTFE bypass grafts were compared with those of revised/occluded PTFE grafts. Ninety-five patients underwent 102 infrainguinal PTFE bypass grafts from January 1991 to December 1996 and were enrolled in a duplex surveillance program at 1 month postoperatively, every 3 months in the first year, every 6 months in the second year, and yearly thereafter. RESULTS: Seventy grafts remained primarily patent, 5 were revised and 27 occluded. There was no significant difference in the mean age, gender, indication for surgery, type of original procedure, or duration of follow-up between both groups. Four hundred and seven duplex surveillance data were available for analysis. Focal increase in peak systolic velocity (PSV) 3 x the adjacent segment or low flow manifested by PSV <45 cm/sec were considered abnormal. In the primarily patent group, 5 bypasses had abnormal duplex surveillance and were found to have no abnormality on angiogram and remained patent during the study period. In the revised/occluded group, duplex surveillance was abnormal in 8 bypasses. Twenty-four bypasses occluded without any predicting abnormalities on their last duplex examination, which was performed within 3 months from the occlusion in the majority of the patients. In the 27 occluded bypasses, no intervention was necessary following the occlusion in 7 grafts because of mild or no symptoms. Two patients were treated with a primary amputation and 2 had new bypasses. In 16 occluded grafts, salvage of the PTFE bypass was attempted. Ten of these grafts were patent at the end of the follow-up. The sensitivity of duplex surveillance was 25% with a positive predictive value of 61.5%. CONCLUSION: Duplex surveillance of infrainguinal PTFE bypass grafts has a low yield and is inadequate at predicting continued bypass patency.

Renal hilar Doppler analysis is of value in the management of patients with renovascular disease.

BACKGROUND: An increasing interest in the role of Doppler ultrasound and duplex scan in screening for renovascular hypertension has recently been noted. We conducted this study to define the role of renal hilar Doppler ultrasound (RHDU) in evaluating renal artery stenosis and its value in the postoperative follow-up after renal revascularization. METHODS: One hundred and fourteen patients are included in this study with a mean age of 63.7 (11 to 89) years. Seventy-two patients underwent renal revascularization. The most frequent revascularization procedure was renal artery bypass in 82%. The RHDU results were compared with 130 angiograms done within 1 month of the RHDU study. The Doppler velocity signal in a segmental artery in the renal parenchyma was recorded, and the waveform was analyzed. An acceleration index (AI) less than 3.78 KHz/sec/MHz and an acceleration time (AT) greater than 0.1 seconds were used to indicate the presence of a significant renal artery stenosis. RESULTS: The overall technical success rate of all RHDU studies was 93.5%. The AI value was higher in the group of patients with normal renal arteries than those with a stenosis (4.7 +/- 1.4 KHz/sec/MHz versus 1.23 +/- 1.13 kHz/sec/MHz, respectively, P <0.0001), and the AT was lower in the former group compared with the latter (0.052 +/- 0.011 sec versus 0.122 +/- 0.069 sec, P <0.0001). The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy for AI were 89%, 92%, 85%, 94%, and 92%, respectively; and for AT were 62.5%, 97.5%, 91%, 86.5%, and 87% respectively. There was a significantly high agreement between the AI and AT results and those of arteriography (Kappa of 0.82 and 0.66, respectively, P < 0.0001). There were 10.6% kidneys with multiple renal arteries by arteriography. In these kidneys the accuracy was lower for both AI and AT and the agreement with arteriography was nonsignificant. In the postoperative period the accuracy of RHDU was 86% for AI and 95% for AT. CONCLUSIONS: Renal hilar Doppler ultrasound has a high accuracy and agreement with arteriography in the diagnosis of renal artery stenosis. Its value is limited by the presence of multiple renal arteries, renal artery occlusion, and high incidence of postoperative false-positive results. It can be useful as a noninvasive screening test for patients suspected of having renal artery stenosis and for surveillance following renal revascularization.

Cardiac screening tests prior to lower extremity revascularization: routine versus selective application.

Coronary artery disease (CAD) is the most important comorbidity associated with peripheral vascular disease. Consensus on the optimal approach to the cardiac evaluation of patients presenting for peripheral vascular operations has not been achieved. We developed a large experience with routine cardiac screening using dipyridamole thallium scintigraphy (DTS) and radionuclide ventriculography. The incidence of reversible ischemia on DTS and the subsequent documentation of severe CAD on coronary angiography was similar in vascular patients with a history of CAD (angina or myocardial infarction) and those with a negative CAD history. However, the analysis of overall risks and benefits does not support a recommendation for routine screening. We suggest that selection of patients for screening should be based on the estimated benefit of coronary revascularization for the individual patient considering both perioperative and long-term survival. In addition, screening is also considered if identification of unsuspected CAD will alter the decision to perform the proposed peripheral vascular operation. Thus, the older patient who requires an infrainguinal bypass for limb-threatening ischemia is unlikely to benefit from cardiac screening. Documentation of the extent of CAD with screening studies may be beneficial in younger patients or in patients with claudication.

Rabbit rectus femoris muscle for ischemia-reperfusion studies: an improved model.

The rabbit rectus femoris muscle was evaluated as a potential model for skeletal muscle reperfusion injury studies. Six white New Zealand rabbits were used. On one randomly selected hind limb, ischemia was induced by direct clamping of the rectus femoris muscle's vascular pedicle. On the other side, blood flow was interrupted by clamping the femoral artery above and below the origin of the vascular pedicle that supplies the rectus femoris muscle. The duration of normothermic ischemia was 4 hr and was followed by 24 hr of normothermic reperfusion. The interruption and restoration of blood flow was monitored using a laser flow meter. The rectus femoris muscles were weighed on a suspension spring balance prior to ischemia and at the end of reperfusion to estimate edema. The extent of muscle necrosis was determined using planimetry following staining with nitroblue tetrazolium. The muscle necrosis obtained by direct clamping of the vascular pedicle (66.9 +/- 14.3%) was significantly greater than that obtained by indirect clamping (18.6 +/- 11.4%) (P < 0.03 by t test). Unlike the indirect clamping technique, direct clamping achieved a good magnitude of muscle necrosis, thus allowing that specific model to be used in skeletal muscle reperfusion injury studies. The muscle weight gain observed in the direct clamping muscle group was 19.8 +/- 9.0% and was significantly greater than that observed in the opposite group being 6.3 +/- 6.5% (P < 0.05 by t test). The rabbit rectus femoris muscle is a suitable model for evaluating skeletal muscle reperfusion injury provided that direct clamping of the vascular pedicle is utilized.

Revascularization of the ischemic diabetic foot using popliteal artery inflow.

Between March 1988 and June 1994, 35 popliteal to distal artery vein bypasses were done in 32 diabetic patients. There were 16 males and 16 females with an average age of 60 years. Eighteen patients (56%) had insulin dependent diabetes mellitus. Medical risk factors included coronary artery disease (CAD) in 15 (47%), hypertension in 15 (47%), chronic renal failure (CRF) in 9 (28%), and cigarette smoking in 10 (31%). Indications for revascularization were: non-healing ulcerations in 18 (51%), gangrene in 15 (43%), and rest pain in 2 (6%). The distal anastomosis was to the posterior tibial artery in 9, anterior tibial artery in 8, dorsalis pedis artery in 10 and peroneal artery in 8 cases. All the bypasses were done with autogenous saphenous veins (in-situ 11, reversed 17, and free non-reversed 7). The limbs were graded into three groups based on the preoperative angiographic evaluation of their pedal arch: patent arch (Grade "0"), partial occlusion of the arch (grade "1.5") and little or no arch visualized (Grade "3"). Eight limbs had Grade "0", 16 had Grade "1.5" and 11 had Grade "3" pedal circulation. Bypass follow up was done by clinical exam and color duplex surveillance (CDS) for a mean duration of 24 months. CDS identified 4 failing bypasses which were surgically revised and have subsequently remained patent. There were 3 bypass occlusions which resulted in a major amputation in 2 patients. Three additional major amputations were performed for persisting infection despite a patent bypass. By life table analysis the cumulative primary & secondary patency and limb salvage rates for this group of diabetic patients were 75% at 2 years, 89% at 3 years and 82% at 3 years respectively (S.E. < 10%). The 3 bypass occlusions, which occurred at 1 week, 5 weeks, and 20 months, were in patients with both CRF and Grade "3" foot circulation (significantly different outcome compared to the rest of the group, by chi 2 test, p < 0.05). Good results can be achieved in the majority of diabetic patients undergoing short popliteal-distal bypasses. However, the combination of chronic renal failure and very limited foot circulation (Grade "3") has a significant adverse outcome.

Selection of patients for cardiac evaluation before peripheral vascular operations.

PURPOSE: This study evaluated the value of preoperative cardiac screening with dipyridamole thallium scintigraphy and radionuclide ventriculography in vascular surgery patients. METHODS: From July 1, 1989, to Dec. 31, 1991, we routinely (irrespective of the patient's cardiac history or symptomatology) performed dipyridamole thallium scintigraphy (DTS) and radionuclide ventriculography (RVG) in 394 patients being considered for an elective vascular operation. Patients with reversible defects on DTS underwent coronary arteriography. RESULTS: DTS results were normal in 146 patients (37%), showed a fixed defect in 75 (19%), and showed a reversible defect in 173 (44%). Patients with and without a history of angina or myocardial infarction had identical rates of reversible defects. Normal left ventricular function (> 50%) was noted in 76% of the patients; 17% had moderate dysfunction (35% to 50%) and 7% had a low ejection fraction (< 35%). The finding of severe coronary artery disease led to cardiac revascularization in 17 patients who had no prior history of cardiac disease and in 13 patients with a history of angina or myocardial infarction. Two deaths and nine major complications were associated with coronary arteriography and cardiac revascularization. Vascular procedures (144 aortic, 53 carotid, 146 infrainguinal) were ultimately performed in 343 patients, with a mortality rate of 1.7% (3.5% aortic, 0% carotid, and 0.7% infrainguinal bypass). The nonfatal perioperative myocardial infarction rate was 2.0%. We monitored all 394 patients for cardiovascular events, with a mean follow-up of 40 months. Patients who underwent cardiac revascularization had a 4-year survival rate of 75%, which was similar to those with a normal DTS. Late cardiac events were significantly more frequent in patients who had either a reversible DTS or RVG < 35%. CONCLUSIONS: Routine cardiac screening of vascular surgery patients had similar impact on patients irrespective of their prior history or current symptoms suggesting coronary artery disease. Routine screening did not result in substantial benefit. Screening studies such as DTS or RVG may be most useful as part of an overall risk versus benefit assessment in patients without active symptoms of coronary artery disease who have less compelling indications for vascular intervention (claudication, moderate-sized aortic aneurysms, or asymptomatic carotid disease).

Lateral approach to the popliteal and crural vessels for limb salvage.

Twenty-one patients underwent 23 bypasses for limb salvage via a lateral approach with subcutaneous graft tunneling. The reasons for utilizing a lateral approach were medial infection (10 bypasses), scarring from previous surgery (six), limited vein length available (three), prior local radiotherapy (two) and 'high risk' groin (two). The target artery was the anterior tibial in 16 cases, the peroneal in three, the above-knee popliteal in three and the dorsalis pedis in one. The median (range) follow-up was 22(<1-52) months. There were three early (within 30 days) and four late bypass occlusions, three of which occurred in previously revised bypasses and one in a non-compliant patient. The primary patency at 1 year was 61% and the secondary patency 86%. Only one amputation was required in the whole series. The lateral approach represents a simple solution to threatened limbs in otherwise difficult or complicated situations and may be the ideal approach for free vein grafts to the anterior tibial and distal peroneal arteries.

Effects of the lazaroid U74389G (21 aminosteroid) on skeletal muscle reperfusion injury in rabbits.

The purpose of this experiment was to evaluate the effects of the aminosteroid U74389G on skeletal muscle reperfusion injury in rabbits. In 24 white New Zealand rabbits (weighing 7.0-8.0 lb), the rectus femoris muscle on both sides was completely isolated on a single vascular pedicle (artery and vein) and a major accessory vein. All muscles were weighed using a suspension spring balance and then underwent 4 hours of normothermic ischemia followed by 24 hours of reperfusion. Muscle ischemia was induced by the application of atraumatic vascular clamps to the vascular pedicles. Complete muscle ischemia and reperfusion were documented by a laser flow meter. The animals were divided into three groups; Group I (n = 8) served as control, Group II (n = 8) received an i.v. bolus of U74389G (1.5 mg/kg) five minutes prior to ischemia, Group III (n = 8) was given the same dose of lazaroid five minutes prior to reperfusion. Muscle biopsies were obtained before ischemia and after reperfusion for quantification of myeloperoxidase (MPO) activity. At the completion of reperfusion, the muscles were excised, weighed and cut into slices along the longitudinal axis and then incubated for 30 minutes in 0.05% nitroblue tetrazolium. Areas of necrosis were determined by computerized planimetry. The following results indicate that reperfusion muscle necrosis in rabbits is significantly decreased by the administration of the lazaroid U74389G. Leukocyte sequestration was not affected by the lazaroid administration. These beneficial effects were observed whether the lazaroid was administered prior to ischemia or prior to reperfusion and were independent of leukocyte sequestration.

The aortic polytetrafluoroethylene graft: further experience.

OBJECTIVES: We analysed our results with the use of aortic polytetrafluoroethylene PTFE grafts over the last 7.5 years. A historical comparison was also made between the results with non-stretch PTFE (NS-PTFE) (1987-91) and stretch PTFE (S-PTFE) grafts (1991-94). MATERIALS: 244 infrarenal aortic replacements or bypasses with PTFE grafts were performed at the University of Iowa Hospitals and Clinics from January 1987 to June 1994. Infrarenal aortic replacement was indicated for aortic aneurysmal disease in 192 patients (elective 151, symptomatic 20, ruptured 21) and bypass for aorto-iliac occlusive disease in 52 patients (disabling claudication 28, limb salvage 24). Patients ranged in age from 37 to 93 years (mean 68 years). There were 161 males and 83 females. Medical risk factors included hypertension (55%), coronary artery disease (31%), COPD (23%), diabetes mellitus (12%) chronic renal failure (9%), and smoking (61%). Aortic replacement or bypass was done with a NS-PTFE graft in 108 patients (44%) and a S-PTFE graft in 136 patients (56%). Postoperative ultrasound (US) scans and/or CT-studies were available in 40 patients with NS-PTFE and 26 patients with S-PTFE grafts. MAIN RESULTS: The 30 day operative mortality was: elective AAA patients (1.3%), symptomatic AAA patients (10%), ruptured AAA patients (48%), limb salvage patients (4.1%) and disabling claudication patients (0%). Graft related complications included five graft limb thromboses (4 NS-PTFE, 1 S-PTFE). Two thromboses occurred perioperatively and the three others at 24, 28 and 30 months postoperatively. Two other graft related complications included a mixed pseudomonas and streptococcus groin infection with a culture negative perigraft fluid collection occurring 3 weeks following surgery (NS-PTFE), and distal aortic anastomotic suture line bleed on the first postoperative day following replacement of a ruptured AAA with a S-PTFE graft. Based on US and/or CT imaging studies, the mean internal diameters of the bodies of 40 NS-PTFE and 26 S-PTFE grafts were 11% and 10% greater than the manufacturer's specified sizes at a mean follow-up duration of 36 and 10 months respectively. CONCLUSIONS: These data reveal that a PTFE graft performs satisfactorily in the aortic position with minimal adverse clinical sequence over a 7.5 year period. Continued long term follow up data will determine the ultimate suitability of aortic PTFE grafts.

Fecal impaction as a cause of acute lower limb ischemia.

Acute lower extremity ischemia secondary to fecal impaction has not been previously reported. Herein, we report the case of an elderly man who was referred to our medical center with an acutely ischemic right lower extremity and a possible abdominal aortic aneurysm. The suspicious abdominal mass noted by his local physician was found to be a large fecal impaction of the rectosigmoid which, by direct pressure, was compressing and occluding the right common iliac artery. After disimpaction, there was complete resolution of the vascular symptoms and signs in the right lower extremity.

Is there a role for abdominal aortic aneurysm exclusion or induced thrombosis?

Most patients with aortic aneurysmal disease are well served by a routine inline bypass replacement procedure. Excellent results have been reported even in patients with significant medical comorbidities. However, occasionally very high-risk patients may benefit from nonresective aortic aneurysm exclusion treatment in association with an axillobifemoral bypass. In the future, endovascular techniques may supplant most conventional and nonresective techniques, thus allowing operative repair in patients who previously might have been rejected for surgical therapy due to multiple medical comorbidities.