J ENDOVASC THER 2014;21:353–355
^LETTER
353
TO THE EDITORS———————————————————————————
Acute Type B Dissection Complicated by Infrarenal Aortic Stent-Graft Collapse With Spontaneous Reexpansion To the Editors: Endovascular aortic aneurysm repair (EVAR) is a safe and durable treatment for infrarenal abdominal aortic aneurysms (AAA). However, it is associated with an increasing number of secondary interventions for early and late complications. In 2009, van Keulen et al.1 reported a case of abdominal stent-graft collapse due to progression of a Stanford type B dissection. They covered the entry tear with a thoracic stent-graft and deployed a stent to re-expand the stent-graft. We recently encountered an 88-year-old patient who 10 years after successful EVAR presented at our emergency department with acute bilateral limb ischemia secondary to an acute type B dissection resulting in collapse of the infrarenal stent-graft by the thrombosed false lumen. The course of this patient followed an unusual and different path than the patient reported by van Keulen and colleagues. In the original procedure, a modular bifurcated Zenith Trifab stent-graft (Cook Medical Europe Ltd, Limerick, Ireland) had been implanted to treat a 5.5-mm AAA after coil embolization of the right internal iliac artery. Ten year later, while the patient was being investigated for dyspnea and fever, a 6.5-cm descending thoracic aortic aneurysm (TAA) was discovered, and he was referred to another facility. Two months later, the patient was seen in our emergency department with acute onset pain and sensory motor deficit in both legs. He specifically denied any thoracic or abdominal complaints. Emergency computed tomographic angiography (CTA) showed an acute type B dissection originating in the distal part of the thoracic aneurysm and extending into the infrarenal aorta. The false lumen was open at the level of the thoracic Q 2014 by the INTERNATIONAL SOCIETY
OF
ENDOVASCULAR SPECIALISTS
^
aorta and completely thrombosed from the diaphragm downwards. At this level the true lumen was almost completely collapsed, as were the main body of the infrarenal stentgraft and the proximal portion of both stentgraft limbs. The iliac limbs were expanded but completely thrombosed. Both external iliac and femoral arteries were completely thrombosed as well. All visceral vessels originated from the true lumen and exhibited distal filling with contrast (Figure, A–D). Since his legs required expeditious revascularization and the collapsed infrarenal stentgraft precluded an endovascular procedure to treat the TAA and cover the primary entry tear, it was decided to revascularize the legs with an axillobifemoral graft from the right axillary artery to both femoral bifurcations in the acute phase, with the intention to perform an aortic reconstruction later once the patient was stabilized. However, his condition deteriorated rapidly after the leg revascularization procedure, with acute renal insufficiency necessitating continuous venovenous hemodialysis; he also had a complete atrioventricular block for which a transvenous pacemaker was placed. Any plans for further aortic reconstruction were abandoned. Surprisingly, within 48 hours, he was weaned of the ventilator, the atrioventricular conductivity normalized, and his renal function improved markedly. Within another 3 days his renal function had returned to preadmission levels, and the plan of aortic reconstruction resurfaced. A new CTA was done to assess the anatomy and showed the type B dissection with an open false lumen in the chest and a completely thrombosed false lumen in the abdomen as before. The abdominal aortic true lumen had increased in size, and surprisingly the stent-graft had re-expanded, although it remained thrombosed. All visceral vessels were open and branched off the true lumen (Figure, E–H). Plans were made to thrombectomize the stent-graft, enabling further stent-graft treatAvailable at www.jevt.org
354
LETTER TO THE EDITORS
J ENDOVASC THER 2014;21:353–355
Figure ^ CT scans of the patient at admission (A–D) showing the TAA and type B dissection with infrarenal occlusion of the true lumen and collapse of the stent-graft. Corresponding images (E–H) captured 6 days later show the type B dissection with re-expansion of the collapsed stent-graft. Transverse sections at the level of the (A,E) distal descending aorta, (B,F) renal arteries, (C,G) infrarenal aorta, and (D,H) distal infrarenal aorta.
ment of the thoracic lesion through the groin. However, the night before the planned endovascular procedure, his renal function deteriorated again. Although an ultrasound scan confirmed flow in the renal arteries, it was decided to proceed with a laparotomy. Nine days after the onset of symptoms and the initial revascularization of both legs, the stentgraft was removed, and the infrarenal aorta was reconstructed with an aortoiliac graft to the left common iliac artery. Both renal arteries were revascularized with 6-mm Dacron bypass grafts. Two 2 ZTEG stent-grafts (Cook Medical Europe Ltd) were deployed via the bifurcated graft limb to exclude the TAA and intimal tear from distal to the left subclavian artery to ~1 cm proximal to the celiac trunk. The patient made an uneventful recovery and was discharged 20 days after onset of symptoms. Only a handful of reports of acute dissections after EVAR have been published,1–4 while up to 2.4% of thoracic stent-grafts in the descending aorta may be complicated by retrograde dissections.5 The mode of dissection formation after EVAR may involve intimal disruption at the site of a heavily calcified atherosclerotic landing zone leading to retrograde dissection. This may be facilitated by excessive oversizing of the aortic stent-graft relative to the size of the aortic sealing zone
and the use of stent-grafts with proximal bare metal stents and anchoring barbs. However, in cases of delayed presentation, spontaneous antegrade dissection of the thoracic aorta is more likely. In our patient, the CTA 2 months prior to admission demonstrated a TAA in the absence of a dissection. We are certain that our patient developed an acute type B aortic dissection on the background of a descending TAA. There is a paucity of data regarding the hemodynamic conditions in the true and false lumens during acute dissections. Although heart rate and number/size of entry tears have a slight impact on diastolic pressure of the false lumen in chronic dissections, ex vivo models demonstrate that in the chronic phase of the dissection the pressures in the true and false lumens are more or less equal.6 The collapse of the infrarenal stent-graft in 4 of 5 published cases of dissection after EVAR is witness of the dramatic changes in pressure gradient between the false and true lumens during the acute phase. In order to lead to stent-graft collapse, the pressure gradient between the false and true lumens must exceed the radial force of the stent-graft. The pressure in the abdominal aortic true lumen may fall significantly below systemic values due to obstructed flow through the true lumen secondary to compression of the proximal
J ENDOVASC THER 2014;21:353–355
true lumen or a mobile flap obstructing flow through it. Simultaneously, the pressure in the false lumen rises to systemic levels so that the achieved pressure gradient may exceed the radial force of the stent-graft, leading to its collapse. Subsequently in the presence of one or more patent intimal tears, the pressure in both lumens may return to equilibrium via communicating vessels. Thus, in the later phases of the dissection, the pressure gradient between the false and true lumens may approach zero, and the stent-graft may reexpand driven by its radial force, as suggested by the spontaneous re-expansion of the stent-graft in our case. The same may be achieved in a more timely manner by deploying a stent-graft to cover the intimal tear, leading to increased true lumen and decreased false lumen pressures. Similarly, ascending and arch replacement in the case of a type A dissection may achieve the same changes to distal true and false lumen pressures. The stent-graft collapse and spontaneous re-expansion of the infrarenal stentgraft seen in our patient suggest that the pressure equilibrium between false and true lumens that is seen in chronic dissections may be reached fairly quickly after the acute event.
Tryfon Vainas, MD, PhD Ignace F.J. Tielliu, MD, PhD Bas M. Wallis de Vries, MD Maarten van der Laan, MD, PhD Clark J. Zeebregts, MD, PhD Jan J.A.M. van den Dungen, MD, PhD
LETTER TO THE EDITORS
355
Department of Surgery Division of Vascular Surgery University Medical Center Groningen Groningen, The Netherlands [email protected] Clark Zeebregts is a consultant for Vascutec and received educational grants from Cook Medical and W.L. Gore & Associates. The other authors declare no association with any individual, company, or organization having a vested interest in the subject matter/products mentioned in this article.
REFERENCES 1. van Keulen JW, Toorop RJ, de Borst GJ, et al. Abdominal stent-graft collapse due to progression of a Stanford type B dissection. J Endovasc Ther. 2009;16:752–754. 2. Girardi LN, Bush HL. Type B aortic dissection and thoracoabdominal aneurysm formation after endoluminal stent repair of abdominal aortic aneurysm. J Vasc Surg. 1999;29:936–938. 3. Iyer V, Rigby M, Vrabec G. Type B aortic dissection after endovascular abdominal aortic aneurysm repair causing endograft collapse and severe malperfusion. J Vasc Surg. 2009;50:413– 416. 4. Szabolcs Z, Huttl K, Laczko A, et al. Acute type A aortic dissection complicated by aortic stent graft collapse. Ann Thorac Surg. 2009;87:1279– 1281. 5. Kpodonu J, Preventza O, Ramaiah VG, et al. Retrograde type A dissection after endovascular stenting of the descending thoracic aorta. Is the risk real? Eur J Cardiothorac Surg. 2008;33: 1014–1018. 6. Tsai TT, Schlicht MS, Khanafer K, et al. Tear size and location impacts false lumen pressure in an ex vivo model of chronic type B aortic dissection. J Vasc Surg. 2008;47:844–851.
^LETTER
353
TO THE EDITORS———————————————————————————
Acute Type B Dissection Complicated by Infrarenal Aortic Stent-Graft Collapse With Spontaneous Reexpansion To the Editors: Endovascular aortic aneurysm repair (EVAR) is a safe and durable treatment for infrarenal abdominal aortic aneurysms (AAA). However, it is associated with an increasing number of secondary interventions for early and late complications. In 2009, van Keulen et al.1 reported a case of abdominal stent-graft collapse due to progression of a Stanford type B dissection. They covered the entry tear with a thoracic stent-graft and deployed a stent to re-expand the stent-graft. We recently encountered an 88-year-old patient who 10 years after successful EVAR presented at our emergency department with acute bilateral limb ischemia secondary to an acute type B dissection resulting in collapse of the infrarenal stent-graft by the thrombosed false lumen. The course of this patient followed an unusual and different path than the patient reported by van Keulen and colleagues. In the original procedure, a modular bifurcated Zenith Trifab stent-graft (Cook Medical Europe Ltd, Limerick, Ireland) had been implanted to treat a 5.5-mm AAA after coil embolization of the right internal iliac artery. Ten year later, while the patient was being investigated for dyspnea and fever, a 6.5-cm descending thoracic aortic aneurysm (TAA) was discovered, and he was referred to another facility. Two months later, the patient was seen in our emergency department with acute onset pain and sensory motor deficit in both legs. He specifically denied any thoracic or abdominal complaints. Emergency computed tomographic angiography (CTA) showed an acute type B dissection originating in the distal part of the thoracic aneurysm and extending into the infrarenal aorta. The false lumen was open at the level of the thoracic Q 2014 by the INTERNATIONAL SOCIETY
OF
ENDOVASCULAR SPECIALISTS
^
aorta and completely thrombosed from the diaphragm downwards. At this level the true lumen was almost completely collapsed, as were the main body of the infrarenal stentgraft and the proximal portion of both stentgraft limbs. The iliac limbs were expanded but completely thrombosed. Both external iliac and femoral arteries were completely thrombosed as well. All visceral vessels originated from the true lumen and exhibited distal filling with contrast (Figure, A–D). Since his legs required expeditious revascularization and the collapsed infrarenal stentgraft precluded an endovascular procedure to treat the TAA and cover the primary entry tear, it was decided to revascularize the legs with an axillobifemoral graft from the right axillary artery to both femoral bifurcations in the acute phase, with the intention to perform an aortic reconstruction later once the patient was stabilized. However, his condition deteriorated rapidly after the leg revascularization procedure, with acute renal insufficiency necessitating continuous venovenous hemodialysis; he also had a complete atrioventricular block for which a transvenous pacemaker was placed. Any plans for further aortic reconstruction were abandoned. Surprisingly, within 48 hours, he was weaned of the ventilator, the atrioventricular conductivity normalized, and his renal function improved markedly. Within another 3 days his renal function had returned to preadmission levels, and the plan of aortic reconstruction resurfaced. A new CTA was done to assess the anatomy and showed the type B dissection with an open false lumen in the chest and a completely thrombosed false lumen in the abdomen as before. The abdominal aortic true lumen had increased in size, and surprisingly the stent-graft had re-expanded, although it remained thrombosed. All visceral vessels were open and branched off the true lumen (Figure, E–H). Plans were made to thrombectomize the stent-graft, enabling further stent-graft treatAvailable at www.jevt.org
354
LETTER TO THE EDITORS
J ENDOVASC THER 2014;21:353–355
Figure ^ CT scans of the patient at admission (A–D) showing the TAA and type B dissection with infrarenal occlusion of the true lumen and collapse of the stent-graft. Corresponding images (E–H) captured 6 days later show the type B dissection with re-expansion of the collapsed stent-graft. Transverse sections at the level of the (A,E) distal descending aorta, (B,F) renal arteries, (C,G) infrarenal aorta, and (D,H) distal infrarenal aorta.
ment of the thoracic lesion through the groin. However, the night before the planned endovascular procedure, his renal function deteriorated again. Although an ultrasound scan confirmed flow in the renal arteries, it was decided to proceed with a laparotomy. Nine days after the onset of symptoms and the initial revascularization of both legs, the stentgraft was removed, and the infrarenal aorta was reconstructed with an aortoiliac graft to the left common iliac artery. Both renal arteries were revascularized with 6-mm Dacron bypass grafts. Two 2 ZTEG stent-grafts (Cook Medical Europe Ltd) were deployed via the bifurcated graft limb to exclude the TAA and intimal tear from distal to the left subclavian artery to ~1 cm proximal to the celiac trunk. The patient made an uneventful recovery and was discharged 20 days after onset of symptoms. Only a handful of reports of acute dissections after EVAR have been published,1–4 while up to 2.4% of thoracic stent-grafts in the descending aorta may be complicated by retrograde dissections.5 The mode of dissection formation after EVAR may involve intimal disruption at the site of a heavily calcified atherosclerotic landing zone leading to retrograde dissection. This may be facilitated by excessive oversizing of the aortic stent-graft relative to the size of the aortic sealing zone
and the use of stent-grafts with proximal bare metal stents and anchoring barbs. However, in cases of delayed presentation, spontaneous antegrade dissection of the thoracic aorta is more likely. In our patient, the CTA 2 months prior to admission demonstrated a TAA in the absence of a dissection. We are certain that our patient developed an acute type B aortic dissection on the background of a descending TAA. There is a paucity of data regarding the hemodynamic conditions in the true and false lumens during acute dissections. Although heart rate and number/size of entry tears have a slight impact on diastolic pressure of the false lumen in chronic dissections, ex vivo models demonstrate that in the chronic phase of the dissection the pressures in the true and false lumens are more or less equal.6 The collapse of the infrarenal stent-graft in 4 of 5 published cases of dissection after EVAR is witness of the dramatic changes in pressure gradient between the false and true lumens during the acute phase. In order to lead to stent-graft collapse, the pressure gradient between the false and true lumens must exceed the radial force of the stent-graft. The pressure in the abdominal aortic true lumen may fall significantly below systemic values due to obstructed flow through the true lumen secondary to compression of the proximal
J ENDOVASC THER 2014;21:353–355
true lumen or a mobile flap obstructing flow through it. Simultaneously, the pressure in the false lumen rises to systemic levels so that the achieved pressure gradient may exceed the radial force of the stent-graft, leading to its collapse. Subsequently in the presence of one or more patent intimal tears, the pressure in both lumens may return to equilibrium via communicating vessels. Thus, in the later phases of the dissection, the pressure gradient between the false and true lumens may approach zero, and the stent-graft may reexpand driven by its radial force, as suggested by the spontaneous re-expansion of the stent-graft in our case. The same may be achieved in a more timely manner by deploying a stent-graft to cover the intimal tear, leading to increased true lumen and decreased false lumen pressures. Similarly, ascending and arch replacement in the case of a type A dissection may achieve the same changes to distal true and false lumen pressures. The stent-graft collapse and spontaneous re-expansion of the infrarenal stentgraft seen in our patient suggest that the pressure equilibrium between false and true lumens that is seen in chronic dissections may be reached fairly quickly after the acute event.
Tryfon Vainas, MD, PhD Ignace F.J. Tielliu, MD, PhD Bas M. Wallis de Vries, MD Maarten van der Laan, MD, PhD Clark J. Zeebregts, MD, PhD Jan J.A.M. van den Dungen, MD, PhD
LETTER TO THE EDITORS
355
Department of Surgery Division of Vascular Surgery University Medical Center Groningen Groningen, The Netherlands [email protected] Clark Zeebregts is a consultant for Vascutec and received educational grants from Cook Medical and W.L. Gore & Associates. The other authors declare no association with any individual, company, or organization having a vested interest in the subject matter/products mentioned in this article.
REFERENCES 1. van Keulen JW, Toorop RJ, de Borst GJ, et al. Abdominal stent-graft collapse due to progression of a Stanford type B dissection. J Endovasc Ther. 2009;16:752–754. 2. Girardi LN, Bush HL. Type B aortic dissection and thoracoabdominal aneurysm formation after endoluminal stent repair of abdominal aortic aneurysm. J Vasc Surg. 1999;29:936–938. 3. Iyer V, Rigby M, Vrabec G. Type B aortic dissection after endovascular abdominal aortic aneurysm repair causing endograft collapse and severe malperfusion. J Vasc Surg. 2009;50:413– 416. 4. Szabolcs Z, Huttl K, Laczko A, et al. Acute type A aortic dissection complicated by aortic stent graft collapse. Ann Thorac Surg. 2009;87:1279– 1281. 5. Kpodonu J, Preventza O, Ramaiah VG, et al. Retrograde type A dissection after endovascular stenting of the descending thoracic aorta. Is the risk real? Eur J Cardiothorac Surg. 2008;33: 1014–1018. 6. Tsai TT, Schlicht MS, Khanafer K, et al. Tear size and location impacts false lumen pressure in an ex vivo model of chronic type B aortic dissection. J Vasc Surg. 2008;47:844–851.
