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Ann Thorac Surg 2002;74:S1833-S1835
© 2002 The Society of Thoracic Surgeons
a Department of Cardiothoracic Surgery, The Mount Sinai School of Medicine, New York, New York, USA
* Address reprint requests to Dr Lansman, Department of Cardiothoracic Surgery, Box 1028, The Mount Sinai Medical Center, New York, NY 10029, USA
e-mail: sllhttxmd{at}msn.com
Presented at the Aortic Surgery Symposium VIII, May 2–3, 2002, New York, NY.
Abstract
BACKGROUND: Surgery for acute type B aortic dissection is associated with significant mortality. We report the results for 34 consecutive patients who underwent urgent surgery because they met criteria for operation during the acute phase (< 14 days) of acute type B dissection.
METHODS: The average patient age was 64 (32 to 88) years. Indications for surgery were persistent pain (12), threatened exsanguination (18), malperfusion (renal [3], limb [3]), rapid aortic enlargement (4), and uncontrolled hypertension (1). The mean interval from onset of pain to operation was 7 (1 to 14) days. Resection included the proximal descending aorta in 32, the distal aortic arch in 10, extension to the diaphragm in 10, and involved a thoracoabdominal procedure in 3. Surgical techniques included hypothermic circulatory arrest (16 [47%]), distal bypass, monitoring of somatosensory-evoked potentials, sequential intercostal sacrifice (average, 5.6 pairs), cerebrospinal fluid drainage, and steroid administration.
RESULTS: There was no hospital mortality. Important complications occurred in 16 patients (47%): 10 respiratory requiring tracheostomy, six infectious, four dialysis, two myocardial infarctions, and two neurologic (one transient stroke, one paraplegia). Mean intensive care unit and hospital stays were 10 (3 to 32) and 35 (7 to 107) days. Survival at 5 and 10 years was 80% and 57%, respectively (mean follow-up, 5.8 years).
CONCLUSIONS: Patients meeting criteria for urgent surgery have a low perioperative risk for mortality and paraplegia, and are relatively free from long-term aorta-related complications. These findings warrant consideration of earlier surgery for appropriate patients with acute type B aortic dissection.
Operative mortality for acute type B dissection has been significant (25% to 50%) [1], with few series reporting long-term postoperative events and survival [2]. The present review seeks to characterize the results and long-term follow-up of patients with acute type B dissection who met criteria for urgent surgery.
Patients and methods
Management protocol
Initial therapy is directed at reducing blood pressure and dp/dt. Surgery is performed in the immediate or subacute phase based on serial clinical and computed tomographic (CT) scan (at admission and 2- and 7-day) evaluations.
Indications for immediate surgery include rupture, aneurysmal aortic dilatation, and intractable pain or uncontrollable hypertension despite medical therapy. Refractory hypertension may result from pseudocoarctation or may be exacerbated by renal malperfusion. Other manifestations of malperfusion include pulseless extremities and signs of visceral ischemia, such as acidosis or rising liver enzymes. Surgery is reserved for malperfusion that cannot be resolved by percutaneous fenestration.
Indications for surgery in the subacute phase (< 14 days) are based on aortic size and signs of impending rupture. If the descending aortic diameter exceeds 5 to 6 cm, resection is performed after stabilization. Signs of impending rupture include recurrent pain and falling hematocrit, or CT evidence of rapid aortic expansion or rapidly accumulating pleural effusion.
Patients
From September 1985 to February 2002, 527 operations were performed for aortic dissection (309 chronic, 168 acute) at The Mount Sinai Medical Center. Acute cases included 168 type A and 16 type A with descending tears [3]. This report focuses on 34 patients with acute type B dissection who underwent surgery within 14 (mean, 7; range, 1 to 14) days of pain onset.
Indications for surgery were persistent pain (12), rupture with threatened exsanguination (18), malperfusion (renal [3], limb [3]), rapid aortic enlargement (4), and uncontrolled hypertension (1). Twenty procedures were performed emergently, 11 urgently, and three were considered elective.
The average age was 64.1 (± 13.4 SD; 32 to 88) years, with 7 patients (21%) >equal; 75 years. There were 20 males and 14 females. Preoperative risk factors included hypertension (28 [82%]), smoking (21 [62%]), Marfan’s Syndrome (one), chronic hemodialysis (one), and preoperative neurologic dysfunction (one stroke; one ischemic neuropathy).
Technique
Thirty patients underwent left thoracotomy, 3 had thoracoabdominal incisions, and 1 underwent thromboexclusion through a median sternotomy. Sixteen patients had partial bypass, and 16 had hypothermic circulatory arrest (HCA) averaging 36 (± 9.0, 17 to 48) minutes; minimum temperatures were 13.7°C (± 1.7°C, 10.6°C to 16.8°C) esophageal and 18.9°C (± 2.9°C, 13.6°C to 23.8°C) bladder. HCA was employed in cases where proximal cross-clamping was not considered safe or feasible.
For cases not requiring HCA, our spinal preservation strategy has been reported [4], and includes partial bypass, mild hypothermia (32°C), and steroid administration. A high spinal perfusion gradient is achieved by permitting relative systemic hypertension while maintaining intrathecal pressure at 10 mm Hg by cerebrospinal fluid drainage. Vasodilators are avoided and, during partial bypass, blood pressure is controlled by partial exsanguination and transfusion using a reservoir in the bypass circuit. Achieving absolute hemostasis helps maintain systemic pressure, and to this end, we prefer full-thickness rather than inclusion-type anastomoses.
An important aspect of our technique is the stepwise, sequential evaluation and ligation of intercostal arteries using somatosensory-evoked potentials (SSEPs) monitoring, which promotes hemostasis while avoiding "steal" from the anterior spinal artery [4].
Postoperatively, relative hypertension is maintained and spinal fluid is drained for 1 to 2 days. SSEPs are monitored until the patient awakens, and then hourly neurologic exams are recorded.
Results
Intraoperative findings
Eighteen of 34 patients (53%) had contained rupture or free blood in the chest, and most (20/34 [59%]) had dilated aortas (mean diameter, 5.6 ± 0.77 cm; 4.5 to 6.5 cm).
Resection included the proximal descending aorta in 32, the distal aortic arch in 10, extended to the diaphragm in 10, and involved a thoracoabdominal procedure in 3 patients. Generally, four pairs of intercostal arteries were sacrificed, from T3 to T6 (average, 5.6 ± 2.2; range, 3 to 11 pairs). No intercostals were reimplanted, as no SSEP changes were observed.
Complications
There were no hospital mortalities, and no patient required exploration for postoperative bleeding. However, significant complications occurred in 16 (47%) patients, including 10 respiratory requiring tracheostomy, six infectious, four dialysis, and two myocardial infarctions. Three patients required thoracic duct ligation for persistent postoperative chylothorax.
One patient (2.9%) developed permanent perioperative paraplegia, 1 developed a reversible ischemic neurologic deficit, and 3 (8.8%) sustained recurrent nerve injuries. Transient postoperative confusion or agitation developed in 8 patients (24%), 6 of whom had undergone hypothermic circulatory arrest. Of note, 3 patients developed preoperative confusion, a phenomenon not infrequently complicating the medical treatment of type B dissection.
False lumen
Postoperative aortograms, CT scans, or magnetic resonance imaging scans were available in 21 (62%) patients. The false lumen was closed in 18 and open in 6 patients (25%).
Follow-up
The average intensive care unit and hospital lengths of stay were 10 (3 to 32) and 35 (7 to 107) days, respectively. Mean follow-up was 5.5 (0.2 to 16.1) years, with 4 patients lost to follow-up (1.5 to 8.6 years). There were nine late deaths (five cardiac, two neoplastic, one other), but only one aorta related, after reoperation at 4.4 years for angiosarcoma involving the distal suture line. Kaplan-Meier 5- and 10-year survival was 80% (± 07.5% SEM) and 55% (± 14% SEM; Fig 1).
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There was no operative mortality in this series of 34 consecutive patients undergoing surgery for acute type B aortic dissection, and 1 case of paraplegia (2.9%), which occurred before implementing our policy of spinal preservation [4]. There was only one aorta-related death during follow-up, and although 6 patients (18%) required reoperations, only 2 were related to their dissection or initial surgery.
Postoperative false lumen patency was 25%, as compared with 47% in our experience with repair of acute type A dissection [5]. Although the latter review suggested that a closed false lumen improved survival, in this series, false lumens were patent in only one of nine late deaths, and in no case requiring reoperation.
Our initial experience with selective management of acute type B dissection was favorable [6], and we reported risk factors for rupture during medical management this condition [7]. The present study confirms that patients selected for surgery, using the criteria described, have a low perioperative risk for mortality and paraplegia, and demonstrates that their long-term course is relatively free from aorta-related complications. Ruptures and reoperations are concentrated in the first 4 years of medical therapy for acute type B dissection [7], and the aorta tends to rupture at a smaller [7] or normal [2] size. These facts, coupled with improving surgical results, warrant consideration of surgery earlier in the acute, subacute, and early chronic phases of type B dissection.
References
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