Stefano Zoli

Long-Term Survival After Open Repair of Chronic Distal Aortic Dissection

BACKGROUND The optimal treatment of chronic distal aortic dissection remains controversial, with endovascular stent-graft techniques challenging traditional surgery. METHODS From January 1994 to April 2007, 104 patients (82 male, median age 60.5 years) with chronic distal aortic dissection underwent surgical repair, 0 to 21 years after initial diagnosis of acute type A or B dissection (median 2.1 years). Twenty-three (22%) patients underwent urgent-emergent surgery. Mean aortic diameter was 6.9 +/- 1.4 cm. Indications for surgery, other than aortic expansion, were pain in 6 (6%) patients, malperfusion in 6 (6%), and rupture in 11 (11%). Forty-nine (47%) had previous cardioaortic surgery (29% dissection-related), 21 (20%) had coronary artery disease, 12 (12%) had Marfan syndrome, and 4 (4%) were on chronic dialysis. Twenty-six (25%) had a thrombosed false lumen. Thirty (29%) patients required reimplantation of visceral arteries; 8.3 +/- 2.7 segmental artery pairs were sacrificed. RESULTS Hospital mortality was 9.6% (10 patients). Paraplegia occurred in 5 (4.8%). Twenty-seven patients (26%) experienced adverse outcome (death within one year, paraplegia, stroke, or dialysis). Adverse outcome was associated with atheroma (p = 0.04, odds ratio = 4.3). Survival was 78% at 1, 68% at 5, and 59% at 10 years (average follow-up, 7.7 +/- 4.1 years). Freedom from distal aortic reoperation was 99% at 1, 93% at 5, and 83% at 10 years. After one year, patients enjoyed longevity equivalent to a normal age-sex matched population (standardized mortality ratio = 1.38, p = 0.23). By multivariate analysis, atheroma (p = 0.0005, relative risk = 9.32) and age (p = 0.0003, relative risk = 1.15/year) were risk factors for long-term survival. CONCLUSIONS The efficacy of open repair for distal chronic dissection is highlighted by normal survival after the first year, and a low reoperation-reintervention rate.

Selective cerebral perfusion at 28 °C - is the spinal cord safe?

OBJECTIVE To shorten cooling/rewarming associated with hypothermic neuroprotection strategies during complex aortic arch surgery, selective cerebral perfusion (SCP) at 28 degrees C has recently been advocated, although its safe limits - especially with regard to the ischaemic tolerance of the spinal cord - have not been systematically examined. METHODS Twenty juvenile Yorkshire pigs (30.3+/-2.8kg) were randomly allocated to undergo circulatory arrest and SCP at 28 degrees C for 90 min (group A; N=12) or 120 min (group B; N=8) at 50 mmHg using alpha-stat pH management. Spinal cord blood flow (SCBF) was assessed using fluorescent microspheres at baseline (prior to SCP); at 5 and 80 min during SCP, and at 1, 5 and 48 h after cardiopulmonary bypass (CPB). A modified Tarlov score was used to evaluate neurobehavioural recovery in all survivors blindly from videotapes for 5 days postoperatively. Histological ischaemic spinal cord injury was scored after sacrifice. RESULTS All pigs could be weaned from CPB and ventilation, but seven pigs (58%) in group A and five (63%) in group B developed multi-organ failure and died within 24h. SCBF diminished immediately after initiation of SCP and was absent throughout SCP in all segments below T8/9, recovering to baseline 1h after SCP at all cord levels. All survivors suffered moderate-to-severe histological lumbar spinal cord damage, more severe in group B (p< or =0.049). Three of five group A pigs recovered normal function, but two suffered paraparesis. Group B survivors had a worse neurologic outcome (p<0.0001): all suffered paraplegia (one immediate, and two on day 2, after initial recovery). CONCLUSION SCP provides insufficient SCBF below T8/9 to sustain cord viability. At 28 degrees C, the ischaemic tolerance of the cord may be exceeded enough by 90 min to impair function; by 120 min, SCP at 28 degrees C invariably results in paraplegia.

Predicting the Risk of Paraplegia After Thoracic and Thoracoabdominal Aneurysm Repair

BACKGROUND Endovascular repair of descending thoracic and thoracoabdominal aortic aneurysms is an appealing alternative to the standard surgical approach, but precludes revascularization of segmental arteries (SAs). For safer surgical and endovascular repairs, an accurate prediction of the risk of paraplegia in relation to the extent of SA sacrifice is needed. METHODS From January 1994 to October 2008, 609 patients (mean age, 63 ± 14 years) underwent surgical descending thoracic or thoracoabdominal aortic aneurysm repair without SA reimplantation. Three hundred seventy-six patients (62%) were male; 159 (26%) had urgent or emergent operation; 199 (33%) had previous aortic surgery. Somatosensory- or motor-evoked potential monitoring and cerebrospinal fluid drainage were routinely performed. RESULTS Hospital mortality was 10.7% (65 patients). Spinal cord injury (SCI) occurred in 3.4% (21 patients). The extent of resection-expressed as the number of SAs sacrificed (p = 0.007)-and the need for visceral artery reimplantation (p = 0.03) were independent risk factors for paraplegia. Further analysis identified four risk groups (p < 0.0001): fewer than 8 SAs sacrificed (group A, SCI = 1.2%); sacrifice of 8 to 12 SAs with proximal origin in the upper thorax (group B, SCI = 3.7%); 8 to 12 SAs sacrificed beginning in the lower thorax (group C, SCI = 15.4%); and 13 or more SAs sacrificed (group D, SCI = 12.5%). This four-group model more accurately predicts SCI risk than the Crawford classification (goodness of fit c statistic: 0.748 versus 0.640). CONCLUSIONS The extent of SA sacrifice is the most powerful predictor of paraplegia risk. For aneurysms of moderate extent, a more distal location involving the abdominal aorta increases the risk of spinal cord injury. Sacrifice of fewer than 8 SAs is associated with a very low paraplegia risk regardless of location.

Direct Spinal Cord Perfusion Pressure Monitoring in Extensive Distal Aortic Aneurysm Repair

BACKGROUND Although maintenance of adequate spinal cord perfusion pressure (SCPP) by the paraspinal collateral network is critical to the success of surgical and endovascular repair of descending thoracic and thoracoabdominal aortic aneurysms, direct monitoring of SCPP has not previously been described. METHODS A catheter was inserted into the distal end of a ligated thoracic segmental artery (SA) (T6 to L1) in 13 patients, 7 of whom underwent descending thoracic and thoracoabdominal aortic aneurysm repair using deep hypothermic circulatory arrest. Spinal cord perfusion pressure was recorded from this catheter before, during, and after serial SA sacrifice, in pairs, from T3 through L4, at 32 degrees C. Somatosensory and motor evoked potentials were also monitored during SA sacrifice and until 1 hour after cardiopulmonary bypass. Target mean arterial pressure was 90 mm Hg during SA sacrifice and after nonpulsatile cardiopulmonary bypass, and 60 mm Hg during cardiopulmonary bypass. RESULTS A mean of 9.8 +/- 2.6 SAs were sacrificed without somatosensory and motor evoked potential loss. Spinal cord perfusion pressure fell from 62 +/- 12 mm Hg (76% +/- 11% of mean arterial pressure) before SA sacrifice to 53 +/- 13 mm Hg (58% +/- 15% of mean arterial pressure) after SA clamping. The most significant drop occurred with initiation of nonpulsatile cardiopulmonary bypass, reaching 29 +/- 11 mm Hg (46% +/- 18% of mean arterial pressure) before deep hypothermic circulatory arrest. Spinal cord perfusion pressure recovered during rewarming to 40 +/- 14 mm Hg (51% +/- 20% of mean arterial pressure), and further within the first hour of reestablished pulsatile flow. Somatosensory and motor evoked potentials returned in all patients intraoperatively. Recovery of SCPP began intraoperatively, and in 5 patients with prolonged monitoring, continued during the first 24 hours postoperatively. All but 1 patient, who had remarkably low postoperative SCPPs and experienced paraparesis, regained normal spinal cord function. CONCLUSIONS This study supports experimental data showing that SCPP drops markedly but then recovers gradually during the first several hours after extensive SA sacrifice. Direct monitoring may help prevent a fall of SCPP below levels critical for spinal cord recovery after surgery and endovascular repair of descending thoracic and thoracoabdominal aortic aneurysms.

When to operate on the bicuspid valve patient with a modestly dilated ascending aorta.

BACKGROUND Bicuspid aortic valves (BAV) are frequently associated with root/ascending aorta dilatation, but there is controversy regarding when to operate to prevent dissection of a dilated aorta associated with a well-functioning BAV. METHODS From 1988 through 2008, 158 patients (mean age: 56 ± 13.5 years) with a dilated ascending aorta (AA) and a well-functioning BAV were referred to our institution. All patients underwent computed tomographic (CT) scanning and digitization to calculate mean AA diameter. Forty-two patients underwent operation a median of 52 days after initial CT scan with a mean AA diameter of 5.6 ± 0.5 cm. One hundred sixteen patients (mean diameter 4.6 ± 0.5 cm) were enrolled in annual or semiannual surveillance. Seventy-one patients, 45 with 2 or more CT scans, are still under surveillance. RESULTS Average follow-up was 6.5 ± 4.1 years. Overall survival after the first encounter was 93% at 5 years and 85% at 10 years. A total of 87 of 158 patients had a Bentall or Yacoub procedure, with two hospital deaths (2.3%). Mean duration of surveillance in the 116 patients without immediate operation was 4.2 ± 2.9 years (481 patient-years). Average growth rate of the AA in patients with 2 scans or greater was 0.77 mm/year (p < 0.0001 versus normal population) with no significant impact of hypertension, sex, smoking or age. Forty-five of the 116 surveillance patients underwent operation after a mean of 3.4 ± 2.9 years (mean age 55 ± 14.7 years; mean AA diameter 4.9 ± 0.6 cm). Six patients died without surgery, median age 82 (range, 44 to 87) years, but none within one year of the last CT scan. CONCLUSIONS A consistent approach to patients with a well-functioning BAV and AA dilatation, recommending operation to those with an AA diameter greater than 5 cm and deferring operation in patients under surveillance in the absence of significant enlargement (>0.5 cm/year), resulted in overall survival equivalent to a normal age-matched and sex-matched population. Operation was necessary in approximately 10% of patients under surveillance each year.

Redo Lateral Thoracotomy for Reoperative Descending and Thoracoabdominal Aortic Repair: A Consecutive Series of 60 Patients

BACKGROUND Reoperative descending thoracic aorta (DTA) or thoracoabdominal aortic aneurysm (TAAA) surgery is a challenge because of increased risk of lung injury and diffuse bleeding. METHODS Sixty patients (34 male, mean age 54.4 years) underwent redo thoracotomy for DTA (22 patients) or extended thoracoabdominal incision for reoperative TAAA (38 patients) from March 1988 to June 2007, after 1.7 +/- 0.9 previous cardioaortic procedures. Forty-one patients were hypertensive (68%), 18 were smokers (30%), 9 had Marfan syndrome (15%), 9 had coronary artery disease (15%), 5 had chronic obstructive pulmonary disease (8%), and 3 had diabetes mellitus (5%). In all, 45% (27 patients) had previous dissection, 30% (18) had atherosclerotic aneurysms, 15% had coarctation surgery (9), and 6 patients had other etiologies. Mean follow-up, 100% complete, was 6.5 years. RESULTS Hospital mortality for reoperative DTA/TAAA was 13.3% (8 patients). Although 6.3 +/- 2.9 (0 to 14) segmental artery pairs were sacrificed at reoperation-and 6.2 +/- 2.3 (1 to 12) initially-for a total of 10.6 +/- 3.9 (2 to 15) segmental artery pairs sacrificed, only 1 patient had paraplegia (1.6%). Four patients had a 2-day procedure, with 12 to 24 hours of intensive care unit recovery after lysis of extensive adhesions: all survived. Respiratory complications occurred in 13 patients (21.6%), and permanent dialysis was required in 2 (3.3%), but there were no strokes. Adverse outcome-1-year mortality, stroke, permanent dialysis, or paraplegia-occurred in 13 patients (21.6%). Adverse outcome was marginally associated (p < 0.2) with increased age, atherosclerotic aneurysms (33% versus 17% other), TAA incision (30% versus 9%), and greater aneurysm extent, and was significantly associated with perfusion technique (p = 0.02). Adverse outcome occurred in 3 of 4 patients who had clamp-and-sew technique, 6 of 21 using partial cardiopulmonary bypass (28.6%), and 3 of 17 with partial left heart bypass (17.7%), but only 1 of 18 with hypothermic circulatory arrest (5.6%). CONCLUSIONS Reoperative DTA/TAAA repair was significantly safer with hypothermic circulatory arrest rather than partial cardiopulmonary bypass, partial left heart bypass, or clamp-and-sew strategy. A 2-day procedure may be advisable for patients with extensive adhesions.

Measuring the collateral network pressure to minimize paraplegia risk in thoracoabdominal aneurysm resection

OBJECTIVE To minimize paraplegia during thoracoabdominal aortic aneurysm repair, the concept of the collateral network was developed. That is, spinal cord perfusion is provided by an interconnecting complex of vessels in the intraspinal, paraspinous, and epidural space and in the paravertebral muscles, including intercostal and lumbar segmental as well as subclavian and hypogastric arteries. METHODS Collateral network pressure was measured with a catheter in the distal end of a ligated segmental artery in pigs and human beings. RESULTS In the pig, collateral network pressure was 75% of the simultaneous mean aortic pressure. With complete segmental arterial ligation, it fell to 27% of baseline, recovering to 40% at 24 hours and 90% at 120 hours. Spinal cord injury occurred in approximately 50% of animals. When all segmental arteries were taken in 2 stages a week apart, collateral network pressure fell only to 50% to 70% of baseline, and spinal cord injury was rare. In human beings, baseline collateral network pressure also was 75% of mean aortic pressure, fell in proportion to the number of segmental arteries ligated, and began recovery within 24 hours. Collateral network pressure was lower with nonpulsatile distal bypass than with pulsatile perfusion. CONCLUSIONS After subtraction of a measure of spinal cord outflow pressure (cerebrospinal fluid pressure or central venous pressure), collateral network pressure provides a clinically useful estimate of spinal cord perfusion pressure.

Experimental Two-Stage Simulated Repair of Extensive Thoracoabdominal Aneurysms Reduces Paraplegia Risk

BACKGROUND In a pig model, we compared spinal cord injury after extensive segmental artery (SA) sacrifice in a single stage with recovery after a two-stage procedure: lumbar artery followed by thoracic SA sacrifice. METHODS Twenty juvenile Yorkshire pigs were randomly assigned to undergo extensive SA sacrifice at 32 degrees C in a single operation (group 1, n = 10), or thoracic SA ligation 7 days after lumbar artery sacrifice (group 2, n = 10). Spinal cord perfusion pressure (SCPP) was monitored using a catheter placed in the distal stump of L1. Hind limb function was evaluated intraoperatively using motor-evoked potentials and for 5 days postoperatively using a modified Tarlov score. RESULTS Motor-evoked potentials were intact in all pigs until 1 hour after surgery. All pigs in group 2 fully recovered hind limb function, whereas 40% in group 1 experienced paraplegia (median Tarlov scores 9 versus 7; p = 0.004). Group 1 SCPP fell to 28 +/- 6 mm Hg after SA sacrifice, compared with 44 +/- 8 mm Hg in group 2 (p < 0.0001). After sacrifice of all residual SAs, SCPP in group 2 remained consistently greater than 85% of baseline, significantly higher than group 1 SCPP from end clamping until 72 hours (p = 0.0002). Histopathologic analysis showed more severe ischemic damage to the lower thoracic (p < 0.001) and lumbar spinal cord (p = 0.01) in group 1. CONCLUSIONS In contrast with the single-stage approach, a two-stage procedure, starting with ligation of six or fewer lumbar SAs, leads to only a mild drop in SCPP and stimulates vascular remodeling, minimizing the impact of subsequent SA sacrifice on spinal cord function. The greater safety of extensive SA sacrifice when undertaken in two stages has important implications for endovascular and hybrid aneurysm repair.

Cumulative radiation exposure during thoracic endovascular aneurysm repair and subsequent follow-up

OBJECTIVES Thoracic endovascular aneurysm repair (TEVAR) is an appealing alternative to the standard surgical approach, but requires rigorous radiological follow-up. The cumulative radiation exposure (RE) of patients undergoing TEVAR-including pre-operative workup, the procedure and subsequent follow-up computed tomography (CT) imaging-has not previously been investigated. METHODS From August 2003 to February 2011, 48 patients underwent TEVAR at our institution. Mean age was 66 ± 11 years, with 10 patients (21%) aged <60 years. Forty-one (85%) patients were male; 7 (15%) had urgent/emergent operation; 21 (44%) had undergone previous aortic surgery. Mean aortic diameter was 7.3 ± 2.1 cm. Intra-operative screening time and RE were reviewed, and typical institutional thoracic CT scan RE was calculated (17.8 mSv). Life expectancy of an age- and sex-matched population was estimated to assess the cumulative RE from recurrent CT follow-up. RESULTS The average screening time was 15.7 ± 11.4 min, with an RE of 11.3 ± 9 mSv. Obese patients had significantly higher RE during TEVAR (Pearsons coefficient = 0.388, P = 0.019). The RE dropped from 14.9 ± 9.4 mSv to 8.6 ± 7.9 mSv (P = 0.033) after a hybrid suite was established. Our institutional TEVAR protocol involves one pre-operative thoracoabdominal CT scan and three follow-up thoracic CT scans for the first year, with a yearly evaluation thereafter. The life expectancy of an age- and sex-matched population was 17 years. A patient adhering to our surveillance protocol would be subjected to an overall exposure of 89 mSv at 1 year and 161 mSv at 5 years, with a projected lifetime RE >350 mSv. CONCLUSIONS A 2-year RE exceeding the threshold of 100 mSv with a life expectancy >15 years can be estimated to lead to a lifetime risk increase in radiation-induced leukaemia and solid-tumour cancer >2.7%. The risks of cumulative RE especially in younger and/or obese patients must be balanced with the expected morbidity and mortality reduction in TEVAR versus traditional open repair, and the anticipated benefits of recurrent radiographic imaging.

Staged approach for spinal cord protection in hybrid thoracoabdominal aortic aneurysm repair

At present, there are three available options for surgical thoracoabdominal aortic aneurysm (TAAA) repair: conventional open surgery, total endovascular repair, and a hybrid approach, involving conventional surgical and endovascular techniques. Each modality has a different risk/benefit profile, requiring careful patient selection. Spinal cord injury (SCI) due to compromised blood supply following extensive segmental artery (SA) sacrifice is a daunting complication observed with all three approaches. A thorough understanding of the response of the spinal cord vasculature to SA sacrifice is essential to minimize the incidence of SCI after open or endovascular repair of TAAA. For over a decade, perioperative spinal cord protection during TAAA repair has been investigated in Dr. Griepp’s laboratory at The Mount Sinai Hospital in New York. Clinical and experimental work have provided insight into the anatomy of the extensive vascular network surrounding the spinal cord, and its dynamic response to SA sacrifice. This new understanding of spinal cord perfusion has been termed the Collateral Network Concept (CNC) (1).