Jan D Galla

Surgical treatment of the dilated ascending aorta: when and how?

BACKGROUNDnThe aorta is considered pathologically dilated if the diameters of the ascending aorta and the aortic root exceed the norms for a given age and body size. A 50% increase over the normal diameter is considered aneurysmal dilatation. Such dilatation of the ascending aorta frequently leads to significant aortic valvular insufficiency, even in the presence of an otherwise normal valve. The dilated or aneurysmal ascending aorta is at risk for spontaneous rupture or dissection. The magnitude of this risk is closely related to the size of the aorta and the underlying pathology of the aortic wall. The occurrence of rupture or dissection adversely alters natural history and survival even after successful emergency surgical treatment.nnnMETHODSnIn recommending elective surgery for the dilated ascending aorta, the patients age, the relative size of the aorta, the structure and function of the aortic valve, and the pathology of the aortic wall have to be considered. The indications for replacement of the ascending aorta in patients with Marfans syndrome, acute dissection, intramural hematoma, and endocarditis with annular destruction are supported by solid clinical information. Surgical guidelines for intervening in degenerative dilatation of the ascending aorta, however, especially when its discovery is incidental to other cardiac operations, remain mostly empiric because of lack of natural history studies. The association of a bicuspid aortic valve with ascending aortic dilatation requires special attention.nnnRESULTSnThere are a number of current techniques for surgical restoration of the functional and anatomical integrity of the aortic root. The choice of procedure is influenced by careful consideration of multiple factors, such as the patients age and anticipated survival time; underlying aortic pathology; anatomical considerations related to the aortic valve leaflets, annulus, sinuses, and the sino-tubular ridge; the condition of the distal aorta; the likelihood of future distal operation; the risk of anticoagulation; and, of course, the surgeons experience with the technique. Currently, elective root replacement with an appropriately chosen technique should not carry an operative risk much higher than that of routine aortic valve replacement. Composite replacement of the aortic valve and the ascending aorta, as originally described by Bentall, DeBono and Edwards (classic Bentall), or modified by Kouchoukos (button Bentall), remains the most versatile and widely applied method. Since 1989, the button modification of the Bentall procedure has been used in 250 patients at Mount Sinai Medical Center, with a hospital mortality of 4% and excellent long-term survival. In this group, age was the only predictor of operative risk (age > 60 years, mortality 7.3% [9/124] compared with age < 60, mortality 0.8% [1/126], p = 0.02).nnnCONCLUSIONSnThis modification of the Bentall procedure has set a standard for evaluating the more recently introduced methods of aortic root repair.

Significance of distal false lumen after type A dissection repair

Fifty-eight patients underwent repair of acute type A dissection between 1986 and 1992. Follow-up aortogram, computed tomographic scan with contrast, magnetic resonance imaging scan, or a combination of these tests was available in 38 patients with preoperatively patent distal false lumens. All distal anastomoses were constructed with the open technique during a period of circulatory arrest. There were 25 suture and 13 intraluminal graft anastomoses. Patency of the distal false lumen was found in 47.3%. Use of the intraluminal graft for the distal anastomosis decreased patency, although not significantly (4/13, 30% versus 14/25, 56%; p = 0.14). The direction of flow into the false lumen was antegrade in 11 of 24 (45.8%) of sutured anastomoses and 0 of 9 intraluminal graft anastomoses (p < 0.01). Actuarial survival at 5 years for patients with closed distal false lumen was 95% +/- 4.8% versus 76% +/- 15% for patients with patency of the distal false lumen (p = not significant). Event-free survival at 5 years for both groups was 84% +/- 8.3% (closed false lumen) and 63% +/- 13.5% (patency of distal false lumen; p = not significant). This experience indicates that in the treatment of acute type A dissections, operative strategy and anastomotic technique play a role in reducing the incidence of patency and related complications of the distal false lumen.

Selective management of acute type B aortic dissection: Long-term follow-up

BACKGROUNDnSince 1985, we have selectively treated acute type B aortic dissections. Initial treatment lowered blood pressure and heart rate. Transesophageal echocardiography and computed tomographic scans were used to diagnose and follow up the patients. Patients were operated on for organ ischemia, pain, hypertension, or increasing subpleural fluid on computed tomographic scan.nnnMETHODSnWe retrospectively reviewed consecutive patients admitted over a 10-year period to the Mt. Sinai Hospital.nnnRESULTSnFrom August 1985 to May 1995, 68 patients were seen. Three died soon after admission during initial diagnostic evaluation. Seventeen patients underwent operation without mortality or paraplegia (group 1). Forty-seven of 48 patients treated nonoperatively were discharged; 1 patient died of rupture on day 7 (group 2). Actuarial survival for all 68 patients at 1 and 5 years was 92% +/- 4% and 82% +/- 8%. Group 1 survival was 93% +/- 4% and 68% +/- 5%, and group 2 survival was 90% +/- 6% and 87% +/-14%. There were no differences between groups. Late intervention was required in 2 group 1 patients (12%) and in 12 of 48 group 2 patients (25%), again without mortality or paraplegia.nnnCONCLUSIONSnThis experience suggests that selective management of acute type B aortic dissection results in acceptable short-term and long-term survival. Avoiding early operation did not compromise late results.

Subtypes of acute aortic dissection

BACKGROUNDnThis series consists of a 12-year experience with a policy of identifying and replacing the aortic segment containing the primary intimal tear for repair of acute aortic dissection.nnnMETHODSnPatients with type A dissection underwent urgent surgery. Patients with type B dissection were referred for surgery based on selective criteria, including aortic dilatation greater than 5 cm. A classification system for acute dissection is described that specifies the site of intimal tear while retaining the clinical relevance of the Stanford system.nnnRESULTSnOf 168 acute dissections, 139 were type A and 29 were type B. The site of intimal tear was as follows: ascending aorta, 83 cases; arch, 32 cases; descending aorta, 29 cases; multiple tears, 11 cases (10 included arch tears); no tear (intramural hematoma), 6 cases; not noted, 7 cases. Only 60% of acute type A dissections arose from solitary intimal tears in the ascending aorta, whereas 30% had arch tears. Hospital mortality for type A dissection was 13.7% (18.8% for arch tears, NS) and 0% for type B. False lumen patency was 57.1% for type A dissection and 18.8% for type B dissection (p = 0.002), yet survival was similar for these groups. Ten-year survival for type A dissection with arch tear (0.51 +/- 0.12) was lower than 10-year survival for type A dissection with ascending tear (0.74 +/- 0.05; p = 0.77), and significantly lower than for type A dissection with descending tear (0.88 +/- 0.12; p = 0.029).nnnCONCLUSIONSnSystematic resection of the primary tear yielded similar hospital mortality, 5-year survival, and aorta-related event-free survival rates for subtypes of acute type A dissection. Excellent results were obtained with a selective approach to type B dissection.

Predictors of adverse outcome and transient neurological dysfunction after ascending aorta/hemiarch replacement.

BACKGROUNDnThis study was undertaken to determine predictors of adverse outcome and transient neurological dysfunction after replacement of the ascending aorta with an open distal anastomosis.nnnMETHODSnAll 443 patients (300 male, median age 63) undergoing replacement of the ascending aorta with an open distal anastomosis between 1986 and 1998 were included in the analysis. The ascending aorta alone was replaced in 190 (42.9%); 253 (57.1%) also had proximal arch replacement. Median hypothermic circulatory arrest (HCA) time was 25 minutes (range 12 to 68). Either death or permanent neurological dysfunction were considered adverse outcome (AO).nnnRESULTSnAdverse outcome occurred in 11.5% (51 of 443) of patients overall: in 7.4% of elective (20 of 269) or urgent (4 of 54) operations, but in 17% (19 of 113) of emergencies. Multivariate analysis of the group as a whole revealed that significant (p < 0.05) independent preoperative predictors of AO were age greater than 60 [odds ratio (OR) 2.2], hemodynamic instability (OR 2.7), and dissection (OR 1.9). For the 435 operative survivors, procedural variables predictive of AO were contained rupture (OR 2.8) and HCA time (OR 1.03/min). When only the 271 elective patients were analyzed separately, the need for a concomitant procedure (p = 0.009, OR 3.6) and HCA time (p = 0.002, OR 1.06/min) were the only predictors of AO in multivariate analysis. Transient neurological dysfunction (TND) occurred in 86 of 392 patients (22%). Significant predictors of TND for all patients without AO were age (OR 1.06/y), HCA time (OR 1.04/min), coronary artery disease (OR 2.2), hemodynamic instability (OR 3.4), and acute operation (OR 2.2). Survival of discharged patients was 93% at 1 year and 83% at 5 years.nnnCONCLUSIONSnEarly elective operation and shorter HCA time during ascending aorta/hemiarch surgery will reduce both AO and TND.

Use of somatosensory evoked potentials for thoracic and thoracoabdominal aortic resections

BACKGROUNDnDespite tremendous development in surgical and anesthetic techniques, resection of the thoracic and thoracoabdominal segments of the aorta remain associated with the risk of paralysis. Routine use of somatosensory-evoked potential (SEP) monitoring in patients undergoing surgery of the thoracic aorta has become a standard intra- and postoperative procedure at our institution since its first use in 1993.nnnMETHODSnOne hundred forty nine (149) thoracic aortic operations were performed during January 1993 through January 1998 using SEP-directed serial sacrifice of paired intercostal arteries. Full, partial, or no cardiovascular bypass was variably used, dictated by anatomy; 49 patients required deep hypothermic circulatory arrest (DHCA). Patients were monitored during both the intraoperative procedure as well for the post-anesthesia period until neurologic stability and/or ability to reproducibly demonstrate lower extremity neurologic competency was established. Postoperative neurologic function was compared to ischemic intervals, extent of aortic resection, number of intercostal arteries sacrificed, type of perfusion, and underlying aortic pathology.nnnRESULTSnOverall mortality in the group was 13 patients (8.7%), with no one cause predominating. Nine patients sustained permanent paraplegia, only 1 of whom lost SEPs during the procedure. Abnormal SEPs were seen in 19 patients, 14 of whom had normal neurologic function after awakening. Three of 19 (15.8%) developed late paraplegia that resolved with medical therapy. Eleven patients (7.4%) developed cerebrovascular accidents (CVA), with the majority (8) appearing in the group undergoing DHCA. The risk of CVA was significantly higher in DHCA patients (p < 0.01) than other patients. No patient with CVA had abnormal SEPs; 4 DHCA patients developed abnormal SEPs, 1 with permanent paralysis.nnnCONCLUSIONSnThe routine use of SEP monitoring during thoracic and thoracoabdominal aortic surgery as well as during the postoperative period may be useful in decreasing the observed incidence of paraplegic events associated with these procedures.

Favorable outcome after composite valve-graft replacement in patients older than 65 years

BACKGROUNDnConcomitant surgical replacement of the aortic valve and ascending aorta is an ideal treatment for aortic root aneurysms, but there may be hesitation in its use in older patients, despite their known increased risk of rupture. This study was conducted to examine our results in 84 patients older than 65 years undergoing elective aortic root resection with composite valve-graft replacement.nnnMETHODSnEighty-four patients older than 65 years were operated on between June 1987 and August 1998. Median age was 74 years (range, 66 to 89 years), and 57 patients were men. Seventeen patients were undergoing reoperation. Aortic insufficiency was present in 70 patients. Forty-seven patients received a conduit using a bioprosthesis, whereas in 37 a mechanical valved conduit (St. Jude) was used. The ascending aorta alone was replaced in 23 patients; 50 had hemi-arch replacement, and in 11 the entire aortic arch was replaced.nnnRESULTSnHospital mortality was 8.3% (7 of 84). Sixteen late deaths (19%) were noted during a median follow-up of 3.2 years (range, 0 to 10 years). Only one late death was aorta-related. The incidence of thrombotic or hemorrhagic complications was 2.1/100 patient-years, with equal frequency for both mechanical and bioprosthetic valves.nnnCONCLUSIONSnWe conclude that composite valve-graft replacement in elderly patients results in a low operative mortality, yields excellent long-term survival, and averts fatal aneurysm rupture in this high-risk population.

Desmopressin acetate is a mild vasodilator that does not reduce blood loss in uncomplicated cardiac surgical procedures

Desmopressin acetate (DA) is a synthetic analog of vasopressin that may improve perioperative coagulation in cardiac surgical patients. Twenty-seven adult patients with good left ventricular function and normal preoperative coagulation profiles scheduled to undergo elective cardiac surgery participated in the double-blinded, placebo-controlled study. The 14 patients in the DA group received the drug over 10 minutes (starting 15 minutes after protamine administration). The 13 patients in the placebo group received an equal volume of saline. Preoperative template bleeding time was longer in the placebo group (P = 0.04). Otherwise, there were no statistically significant differences between the groups in demographics, coagulation variables, renal concentrating function, blood loss, or transfusion requirements at any study interval. The only significant hemodynamic differences detected were an increase in cardiac output in the DA group and a corresponding decrease in systemic vascular resistance. Five of 13 patients who received DA required treatment for hypotension, whereas none of 12 patients who received placebo required treatment during the infusion (P = 0.008). The authors conclude that DA causes mild vasodilation, but does not reduce blood loss or transfusion requirements in patients undergoing primary uncomplicated cardiac surgical procedures.

Bioprosthetic valved conduit aortic root reconstruction: the Mount Sinai experience

BACKGROUNDnPatients requiring aortic root reconstruction who are deemed unable to take anticoagulants offer unique challenges to the surgeon. For these patients, we have been manufacturing composite conduits intraoperatively using stented bioprostheses.nnnMETHODSnDuring the 10-year period from April 1992 until May 2002, 141 patients (105 male, 36 female) from 34 to 88 years of age underwent aortic root reconstruction with biological valved conduits. Diagnoses included dissection (n = 28, 9 acute type A), degenerative (64), atherosclerotic (32), anuloaortic ectasia (9), endocarditis (5), and other causes (3). Preoperative risk factors included hypertension (90), smoking (63), coronary artery disease (48), and diabetes (6). Valved conduits were mainly constructed from pericardial valves and impregnated Dacron grafts. Distal anastomosis was performed open in all cases except 6; the ascending aorta only was replaced in 63 patients, a hemiarch reconstruction was used in 71, and more extensive arch reconstruction in 7. Additional cardiac procedures were performed in 59 patients.nnnRESULTSnTwo deaths occurred in the operating room (biventricular failure). Late hospital mortality was 11 of 141 (7.8%) of which 6 (55%) were cardiac, 2 (18.2%) were infectious, 2 (18.2%) were of other complications and 1 (9.1%) was unknown. Three patients (2.1%) sustained permanent and 3 transient strokes. No structural deterioration of the valve and an approximately 86% freedom from thromboembolic events was observed during 5 years.nnnCONCLUSIONSnFor patients for whom anticoagulation is contraindicated or undesirable, reconstruction of the aortic root with a stented bioprosthetic valved conduit offers an acceptable alternative to mechanical prostheses.

Delayed chronic type A dissection following CABG: implications for evolving techniques of revascularization.

Abstract Background: Postoperative dissection in some patients is related to manipulation of the aorta and accounts for 3% to 5% of deaths after cardiac surgery. Methods: Between 1987 and 1999, 109 patients with previous cardiac operations were treated for chronic type A dissection. In 31 of the patients, the etiology was related to aortic manipulation. Twenty‐one patients (17 men, 4 women; 67 ± 13 years of age) had isolated coronary artery bypass grafting (CABG) as their first operation and were reviewed. The interval between operations was 52.9 ± 47.3 months. Results: Reoperation was elective in 11 patients, urgent in 10 patients. Median maximal aortic diameter was 6.8 ± 2.1 cm; 9 patients had major aortic insufficiency. The intimal tear was at the partial occlusion clamp site in 12 patients (57.1%), at the cross‐clamping site in 4 patients (19.1%), and at the proximal anastomosis in 1 patient (4.8%); 4 patients (19.1%) had multiple tears at several sites. Cystic media necrosis was present in 9.5% of the patients, severe atherosclerosis in 47.6% of the patients, and 42.9% of the patients had both. Nine patients (42.9%) underwent a modified Bentall procedure, 12 patients (57.1%) underwent a supracoronary anastomosis, and all had open distal anastomosis. There were two (9.5%) hospital deaths and three (14.3%) postoperative strokes. Freedom from cardiac or aorta‐related mortality was 85.7% at a mean follow‐up of 49.3 months. Conclusions: In patients who develop type A dissection of the aorta after previous CABG, the intimal tear most often is at partial occlusion clamp site. This complication is associated with morbidity and mortality. It remains to be seen whether the use of partial occlusion clamps on the pulsating and often diseased aorta during off‐pump coronary artery bypass (OPCAB) will increase the risk of delayed iatrogenic dissections.