Cardlova,,c lntervenl Radio1119921 15 367-374
CardioVascular andInterventional Radidogy g:, Sprmger-Verlag New York Inc. 1992
Metallic Stents for the Treatment of Biliary Obstruction: A Report of 100 Cases Harold C o o n s Department of Radiology, Sharp Memorial Hospital, San Diego, California, USA
Abstract. T h e results o f the first 100 patients to receive Gianturco-R~Ssch "'Z "" stents is presented along with r e c o m m e n d a t i o n s for their use. The patient population was c o m p r i s e d o f 57 men and 43 w o m e n , age range 17-85 years (mean 65 years). Fifty-four of the patients had benign obstruction and 46 had malignant o b s t r u c t i o n . Of the benign lesions, I l had sclerosing cholangitis and the remainder had p o s t o p e r a t i v e strictures. T h i r t y - o n e of the malignant obstructions were s e c o n d a r y to c h o l a n g i o c a r c i n o m a with the majority o f the o t h e r s s e c o n d a r y to metastases from various s o u r c e s . All but one had multiple s y s t e m s involved. Patients with benign postoperative strictures were all initially treated with balloon angioplasty: if this failed, stents were inserted. In patients w h o had stents in place for greater than 1 year, the o c c l u s i o n rate was 13%. The overall occlusion rate in the 43 patients was 7%. Patients with sclerosing cholangitis did less well. In those with sclerosing chotangitis s e c o n d a r y to intraarteria, l c h e m o t h e r a p y , the o c c l u s i o n rate was 77%, and we no longer use the metallic " Z ' " stent in these patients. The stent was not used for malignant c o m m o n duct obstruction. All patients had hilar involvement. In the patients with malignant obstruction, 17% reo b s t r u c t e d prior to their death. The patients with c h o l a n g i o c a r c i n o m a did well with a mean survival time o f 14 m o n t h s and a re-obstruction rate o f 165-~. All late o b s t r u c t i o n s w e r e s e c o n d a r y to t u m o r overg r o w t h either proximal or distal to the stents. We c o n c l u d e that the " Z ' " stent is an effective form of t r e a t m e n t in patients with benign p o s t o p e r a t i v e strictures and those with malignant obstruction involving the hilum. W e do not r e c o m m e n d it as a r e p l a c e m e n t for c o n v e n t i o n a l stents, but rather as Harold Coons, M.D., Department of Radiology, Sharp Memorial Hospital, 7901 Frost Street, San Diego, CA 92123-2788, USA
Address reprint request5 to:
an additional device that allows t r e a t m e n t o f some of the more difficult c a u s e s o f o b s t r u c t i o n . Key words: Bile d u c t s - - I n t e r v e n t i o n a l dure--Prostheses--Stenosis
proce-
Biliary o b s t r u c t i o n c o n t i n u e s to be a difficult problem to treat. There have b e e n a n u m b e r o f recent articles discussing the use o f metallic stents for this problem [1-8]. Various c o n c l u s i o n s have been d r a w n ranging from a b a n d o n m e n t o f the use o f metallic stents in treating malignant o b s t r u c t i o n [8] to a strong r e c o m m e n d a t i o n o f their use in malignant obstruction [7]. Their use f o r treating recurrent biliary strictures has been a d v o c a t e d by several authors [1, 2]. C o n c e r n s o v e r cost and efficacy have raised questions o f their a p p r o p r i a t e use [6]. In an attempt to evaluate the G i a n t u r c o - R o s c h " ' Z " stent, these stents were used in 100 patients with both benign and malignant biliary o b s t r u c t i o n . The '~Z'" stent was not used as a r e p l a c e m e n t for c o n v e n t i o n a l stents, but r a t h e r in c a s e s w h e r e the use o f a c o n v e n tional stent was not a p p r o p r i a t e or has been disappointing.
Material and Methods One hundred patients (57 males, 43 femalesJ recmved a total of 241 stents. Ten patmnts received only a single stent. The greatest number of stents placed in a single patient was I 1. In most bemgn stnctures, two stents were needed fbr successful drainage. The patients ranged in age from 17 to 85 years (mean 65 yearsl. Fiftyfour patients had benign strictures (Table 1) and 46 had malignant obstruction (Table 2). The technique for insertion has been adequately described in a previous arttcle [1], Any modifications to that technique will be discussed on an individual basis.
368
H. Coons: Metallic Stents for Bdiary Obstruction
Table 1. Patients with bemgn strictures Diagnosis
Number
Postoperative
43
Primary sclerosing cholangitis
4
Secondary scterosmg cholangitls
_~7 Total
5,4
Table 2, Patients with malignant obstruction Diagnosis
Number
Cholanglocarcinoma
3t
Metastatic gallbladder
4
Metastatic colon
3
Lymphoma
3
Metastatic breast
2
Metastatic pancreas
2
Ampullary carcinoma
1 Total
46
Results
Benign Strictures The group with benign strictures/n = 54~ was subdivided into benign postoperative strictures and patients with sclerosing cholangitis. Of the 43 patients in the postoperative group, there were 2 with stents in place for over 4 years. 2 who have had stents for over 3 years, 8 patients with stents in place 2-3 years, and 10 patients with stents for more than 1 year. The remaining 21 patients have had stents in place for 1 year or less. The initial patient received a stent over 4 years ago and remains symptom free. Three patients have returned with obstruction. All 3 had initial surgery for malignancy. 2 of whom had cholangiocarcinoma and the third patient had Hodgkins disease with obstruction secondary to enlarged periportal nodes. Repeat biopsies on these patients failed to reveal active tumor, and it is unclear if the underlying malignancy contributed to the reocclusion in any way. Choledochoscopy was performed on 2 of these patients, and the obstruction was secondary to mucosal hypertrophy. The occlusions occurred at 7 months, 9 months, and 43 months, respectively. There is an overall occlusion rate of 7% in the 43 patients. This is most likely lower than the actual number should be as there is a large group of patients with stents in place
for 1 year or less. Of the 4 patients over 3 years, l has had reobstruction, and this would give an occlusion rate of 25%. The sampling numbers are so small, however, that this may be abnormally high. The occlusion rate is 13% in the 22 patients in whom the stents have been in place for more than 1 year: this is most likely a more accurate figure. In the sclerosing cholangitis group there were 11 patients: 7 had sclerosing cbolangitis secondary to intraarterial chemotherapy, and 4 had primary sclerosing cholangitis. The results in the first subgroup were disappointing. Of the 7 patients that developed sclerosing cholangitis secondary to intraarterial chemotherapy infusion, 5 required an additional drainage procedure at an average of 6 months. In 4 of the 5 patients, fungal growth caused the occlusion. Presumably the predilection to fungus infection is secondary to suppression of the immune system from the chemotherapy. The remaining 2 patients died of their underlying disease at 6 months and 8 months, respectively. We no longer use the stainless steel stent in patients with secondary sclerosing cholangitis. Of the 4 patients with primary scterosing cholangitis. I is stable at 31 months. One patient became jaundiced at 21 months and was redrained and restented. This patient died of progressive liver failure 23 months after the original stent placement. In 1 patient, there has been deterioration of the liver according to liver function studies, and a repeat ERCP shows progressive disease within the stents. The fourth patient is stable at 22 months.
Malignant Obstruction With the exception of I patient with an ampullary carcinoma early in the series, all patients had high obstructions involving more than one system. There were 32 patients with cholangiocarcinoma and 14 patients with metastatic disease of various sources. Using the Bismuth staging system, 5 patients were Bismuth II, 8 were Bismuth III, and 32 were Bismuth IV. Of the patients with metastatic disease, 2 required repeat biliary drainage for recurrent jaundice; both had obstruction at approximately 3 months. In both patients there was tumor extension between the struts of the stent, and external biliary catheters were placed for symptomatic relief. Of the remaining 12 patients with metastatic obstruction, 3 are alive and jaundice free at 2, 7, and 14 months poststenting. One patient died at 4 months with jaundice, the cause being unknown. The remaining 8 patients were jaundice free at death, which ranged from 2 to 9.6 months (mean 4.8 months). All patients with cholangiocarcinoma were
H. Coons: Metalhc Stents for Bihary Ob,,tructlon
treated with irradiation prior to stenting. Twentyeight patients had both intraluminal Iridium-192 and external beam irradiation, and 4 had Ir-192 irradiation only. In addition to the 32 stented patients, there were 2 patients who expired during their period of irradiation and, therefore, did not receive stents; they were excluded from the study. The mean survival time was 14 months (4-40 months). Five of the 32 patients reobstructed prior to death (16%) at 4-19 months (mean 10 months). In all cases, the obstruction was due to tumor overgrowth, either proximal (I case) or distal (4 cases) to the stents. One case with distal reobstruction was treated with an endoscopically placed stent (Fig. l). The other 4 patients were reaccessed and left to external drainage until they expired. There are 10 patients still living with stents in place 2-40 months.
Discussion It is important to emphasize that in all patients, whether the obstruction was malignant or benign, the metallic " Z " stent was inserted as a final step when all other modalities appeared to have a less likely chance of success. All patients with benign postoperative strictures were initially treated with dilatation by angioplasty balloon, and a drainage catheter was left in place for up to 3 months. Only if there was recurrence of the stricture was the metallic ~'Z" stent inserted. This approach, stressed by Rossi et al. [2], is clinically prudent as the majority of patients will respond to balloon dilatation alone. There is, however, a significant recurrence rate of 27-33% for anastomotic strictures, and 12-24% for iatrogenic strictures at 3 years [2, 9, 10]. In our study, we have treated this "'failed" group exclusively. An occlusion rate of 13% in patients with stents in place for more than l year seems acceptable. There are 4 patients with stents in place for o v e r 3 years and only l of these patients has reocctuded. This tiny sample has an occlusion rate of 25% at 3 years. This cannot be compared to the occlusion rate at 3 years of 20% after balloon angioplasty alone stated by Mueller et al. [9], as all of the " s u c c e s s e s " were eliminated from our study. Stated in a different way, of the 24% with recurring obstruction after balloon angioplasty, an additional 75% were symptom free at 3 years for an overall occlusion rate, using both methods, of 6%. This is not an accurate figure as the number of patients in the two studies are quite different. As a larger number of patients with metallic stents in place exceeds 3 years, a more accurate percentage will be apparent. Patients that do reobstruct, however, have a drainage catheter reinserted and have
369
had a period of time without an external drainage catheter in place. Although reobstruction can be considered a failure of the metallic stent, these patients have not lost the ability to be drained and may have had a significant period of time without an external drainage catheter. If metallic stents are used only in patients who have failed balloon dilatation, an improved patency rate will be achieved. The two methods are complementary rather than competitive. Rossi et al. [2] pointed out that the alternatives to placing metallic stents in the failed group are limited to repeat surgery, which has a relatively high recurrence rate, and long-term indwelling catheters. In the 3 patients in this study who developed recurrent obstructions, drainage catheters were left in place. Additional metallic stents were placed inside the original stents in the first patient, in the erroneous belief that the recurrent obstruction was due to fibrous overgrowth. When this patient became reobstructed at 4 months, a c h o l e d o c h o s c o p e was inserted, and biopsies were performed. The biopsy revealed mucosal hyperplasia with no evidence of malignancy (Fig. 2). In all cases of obstruction, the confirmed cause was mucosal hyperplasia. This is apparently a foreign body reaction, similar to the endothelial proliferation seen when metallic stents are placed in arteries [11]. Modification of the metallic stent material, such as covering it with a special coating, should reduce this reaction. It may be that laser resection via the choledochoscope of this hypertrophic tissue could allow the removal of the external drainage catheter. To date, this has not been attempted by US.
One point should be reemphasized. In patients who have undergone a high cholodochojejunostomy, near the hilum, stents need to be placed in both the right and left biliary systems to avoid compression of the neighboring ductal system It]. We agree with Rossi et al. [2] that only double " Z " stents should be used for biliary enteric anastomoses. This prevents dislodgement, and there have been no reported causes of ulcerations secondary to the " Z " stent extending into the bowel lumen, Lameris et al. [7] recently reported 2 cases of duodehal ulceration using the Wallstent (Schneider) and a case of c o m m o n bile duct perforation~ The difference in stent design may account for their incidence of perforation. Cure was not expected in the group with sclerosing cholangitis and, in fact, the initial hope was that prolonged patency could be achieved using the metallic " Z " stent. Although there was a longer period of time to obstruction than with simple balloon angioplasty, it became clear early on that there
370
H Coons: Metalhc S~ents for Bihary Ob,,truct~on
:;~,
,.,,
.".
:-ga{g ...,~..g.., . . "f.,,, ,. %, 9
I/...~
,r.'" I1
o~
,,,§
'
%..'~.., ' ~ ' . : , __ t : - 4 ,
D
< '
}~
"-..:?..:;~.,
.
,,,~,e,~p1~_~ " "'i~.'i;:,.;:,"c. :, ,.
, "'...,.~ Fig. 1. A Si'
CardioVascular andInterventional Radidogy g:, Sprmger-Verlag New York Inc. 1992
Metallic Stents for the Treatment of Biliary Obstruction: A Report of 100 Cases Harold C o o n s Department of Radiology, Sharp Memorial Hospital, San Diego, California, USA
Abstract. T h e results o f the first 100 patients to receive Gianturco-R~Ssch "'Z "" stents is presented along with r e c o m m e n d a t i o n s for their use. The patient population was c o m p r i s e d o f 57 men and 43 w o m e n , age range 17-85 years (mean 65 years). Fifty-four of the patients had benign obstruction and 46 had malignant o b s t r u c t i o n . Of the benign lesions, I l had sclerosing cholangitis and the remainder had p o s t o p e r a t i v e strictures. T h i r t y - o n e of the malignant obstructions were s e c o n d a r y to c h o l a n g i o c a r c i n o m a with the majority o f the o t h e r s s e c o n d a r y to metastases from various s o u r c e s . All but one had multiple s y s t e m s involved. Patients with benign postoperative strictures were all initially treated with balloon angioplasty: if this failed, stents were inserted. In patients w h o had stents in place for greater than 1 year, the o c c l u s i o n rate was 13%. The overall occlusion rate in the 43 patients was 7%. Patients with sclerosing cholangitis did less well. In those with sclerosing chotangitis s e c o n d a r y to intraarteria, l c h e m o t h e r a p y , the o c c l u s i o n rate was 77%, and we no longer use the metallic " Z ' " stent in these patients. The stent was not used for malignant c o m m o n duct obstruction. All patients had hilar involvement. In the patients with malignant obstruction, 17% reo b s t r u c t e d prior to their death. The patients with c h o l a n g i o c a r c i n o m a did well with a mean survival time o f 14 m o n t h s and a re-obstruction rate o f 165-~. All late o b s t r u c t i o n s w e r e s e c o n d a r y to t u m o r overg r o w t h either proximal or distal to the stents. We c o n c l u d e that the " Z ' " stent is an effective form of t r e a t m e n t in patients with benign p o s t o p e r a t i v e strictures and those with malignant obstruction involving the hilum. W e do not r e c o m m e n d it as a r e p l a c e m e n t for c o n v e n t i o n a l stents, but rather as Harold Coons, M.D., Department of Radiology, Sharp Memorial Hospital, 7901 Frost Street, San Diego, CA 92123-2788, USA
Address reprint request5 to:
an additional device that allows t r e a t m e n t o f some of the more difficult c a u s e s o f o b s t r u c t i o n . Key words: Bile d u c t s - - I n t e r v e n t i o n a l dure--Prostheses--Stenosis
proce-
Biliary o b s t r u c t i o n c o n t i n u e s to be a difficult problem to treat. There have b e e n a n u m b e r o f recent articles discussing the use o f metallic stents for this problem [1-8]. Various c o n c l u s i o n s have been d r a w n ranging from a b a n d o n m e n t o f the use o f metallic stents in treating malignant o b s t r u c t i o n [8] to a strong r e c o m m e n d a t i o n o f their use in malignant obstruction [7]. Their use f o r treating recurrent biliary strictures has been a d v o c a t e d by several authors [1, 2]. C o n c e r n s o v e r cost and efficacy have raised questions o f their a p p r o p r i a t e use [6]. In an attempt to evaluate the G i a n t u r c o - R o s c h " ' Z " stent, these stents were used in 100 patients with both benign and malignant biliary o b s t r u c t i o n . The '~Z'" stent was not used as a r e p l a c e m e n t for c o n v e n t i o n a l stents, but r a t h e r in c a s e s w h e r e the use o f a c o n v e n tional stent was not a p p r o p r i a t e or has been disappointing.
Material and Methods One hundred patients (57 males, 43 femalesJ recmved a total of 241 stents. Ten patmnts received only a single stent. The greatest number of stents placed in a single patient was I 1. In most bemgn stnctures, two stents were needed fbr successful drainage. The patients ranged in age from 17 to 85 years (mean 65 yearsl. Fiftyfour patients had benign strictures (Table 1) and 46 had malignant obstruction (Table 2). The technique for insertion has been adequately described in a previous arttcle [1], Any modifications to that technique will be discussed on an individual basis.
368
H. Coons: Metallic Stents for Bdiary Obstruction
Table 1. Patients with bemgn strictures Diagnosis
Number
Postoperative
43
Primary sclerosing cholangitis
4
Secondary scterosmg cholangitls
_~7 Total
5,4
Table 2, Patients with malignant obstruction Diagnosis
Number
Cholanglocarcinoma
3t
Metastatic gallbladder
4
Metastatic colon
3
Lymphoma
3
Metastatic breast
2
Metastatic pancreas
2
Ampullary carcinoma
1 Total
46
Results
Benign Strictures The group with benign strictures/n = 54~ was subdivided into benign postoperative strictures and patients with sclerosing cholangitis. Of the 43 patients in the postoperative group, there were 2 with stents in place for over 4 years. 2 who have had stents for over 3 years, 8 patients with stents in place 2-3 years, and 10 patients with stents for more than 1 year. The remaining 21 patients have had stents in place for 1 year or less. The initial patient received a stent over 4 years ago and remains symptom free. Three patients have returned with obstruction. All 3 had initial surgery for malignancy. 2 of whom had cholangiocarcinoma and the third patient had Hodgkins disease with obstruction secondary to enlarged periportal nodes. Repeat biopsies on these patients failed to reveal active tumor, and it is unclear if the underlying malignancy contributed to the reocclusion in any way. Choledochoscopy was performed on 2 of these patients, and the obstruction was secondary to mucosal hypertrophy. The occlusions occurred at 7 months, 9 months, and 43 months, respectively. There is an overall occlusion rate of 7% in the 43 patients. This is most likely lower than the actual number should be as there is a large group of patients with stents in place
for 1 year or less. Of the 4 patients over 3 years, l has had reobstruction, and this would give an occlusion rate of 25%. The sampling numbers are so small, however, that this may be abnormally high. The occlusion rate is 13% in the 22 patients in whom the stents have been in place for more than 1 year: this is most likely a more accurate figure. In the sclerosing cholangitis group there were 11 patients: 7 had sclerosing cbolangitis secondary to intraarterial chemotherapy, and 4 had primary sclerosing cholangitis. The results in the first subgroup were disappointing. Of the 7 patients that developed sclerosing cholangitis secondary to intraarterial chemotherapy infusion, 5 required an additional drainage procedure at an average of 6 months. In 4 of the 5 patients, fungal growth caused the occlusion. Presumably the predilection to fungus infection is secondary to suppression of the immune system from the chemotherapy. The remaining 2 patients died of their underlying disease at 6 months and 8 months, respectively. We no longer use the stainless steel stent in patients with secondary sclerosing cholangitis. Of the 4 patients with primary scterosing cholangitis. I is stable at 31 months. One patient became jaundiced at 21 months and was redrained and restented. This patient died of progressive liver failure 23 months after the original stent placement. In 1 patient, there has been deterioration of the liver according to liver function studies, and a repeat ERCP shows progressive disease within the stents. The fourth patient is stable at 22 months.
Malignant Obstruction With the exception of I patient with an ampullary carcinoma early in the series, all patients had high obstructions involving more than one system. There were 32 patients with cholangiocarcinoma and 14 patients with metastatic disease of various sources. Using the Bismuth staging system, 5 patients were Bismuth II, 8 were Bismuth III, and 32 were Bismuth IV. Of the patients with metastatic disease, 2 required repeat biliary drainage for recurrent jaundice; both had obstruction at approximately 3 months. In both patients there was tumor extension between the struts of the stent, and external biliary catheters were placed for symptomatic relief. Of the remaining 12 patients with metastatic obstruction, 3 are alive and jaundice free at 2, 7, and 14 months poststenting. One patient died at 4 months with jaundice, the cause being unknown. The remaining 8 patients were jaundice free at death, which ranged from 2 to 9.6 months (mean 4.8 months). All patients with cholangiocarcinoma were
H. Coons: Metalhc Stents for Bihary Ob,,tructlon
treated with irradiation prior to stenting. Twentyeight patients had both intraluminal Iridium-192 and external beam irradiation, and 4 had Ir-192 irradiation only. In addition to the 32 stented patients, there were 2 patients who expired during their period of irradiation and, therefore, did not receive stents; they were excluded from the study. The mean survival time was 14 months (4-40 months). Five of the 32 patients reobstructed prior to death (16%) at 4-19 months (mean 10 months). In all cases, the obstruction was due to tumor overgrowth, either proximal (I case) or distal (4 cases) to the stents. One case with distal reobstruction was treated with an endoscopically placed stent (Fig. l). The other 4 patients were reaccessed and left to external drainage until they expired. There are 10 patients still living with stents in place 2-40 months.
Discussion It is important to emphasize that in all patients, whether the obstruction was malignant or benign, the metallic " Z " stent was inserted as a final step when all other modalities appeared to have a less likely chance of success. All patients with benign postoperative strictures were initially treated with dilatation by angioplasty balloon, and a drainage catheter was left in place for up to 3 months. Only if there was recurrence of the stricture was the metallic ~'Z" stent inserted. This approach, stressed by Rossi et al. [2], is clinically prudent as the majority of patients will respond to balloon dilatation alone. There is, however, a significant recurrence rate of 27-33% for anastomotic strictures, and 12-24% for iatrogenic strictures at 3 years [2, 9, 10]. In our study, we have treated this "'failed" group exclusively. An occlusion rate of 13% in patients with stents in place for more than l year seems acceptable. There are 4 patients with stents in place for o v e r 3 years and only l of these patients has reocctuded. This tiny sample has an occlusion rate of 25% at 3 years. This cannot be compared to the occlusion rate at 3 years of 20% after balloon angioplasty alone stated by Mueller et al. [9], as all of the " s u c c e s s e s " were eliminated from our study. Stated in a different way, of the 24% with recurring obstruction after balloon angioplasty, an additional 75% were symptom free at 3 years for an overall occlusion rate, using both methods, of 6%. This is not an accurate figure as the number of patients in the two studies are quite different. As a larger number of patients with metallic stents in place exceeds 3 years, a more accurate percentage will be apparent. Patients that do reobstruct, however, have a drainage catheter reinserted and have
369
had a period of time without an external drainage catheter in place. Although reobstruction can be considered a failure of the metallic stent, these patients have not lost the ability to be drained and may have had a significant period of time without an external drainage catheter. If metallic stents are used only in patients who have failed balloon dilatation, an improved patency rate will be achieved. The two methods are complementary rather than competitive. Rossi et al. [2] pointed out that the alternatives to placing metallic stents in the failed group are limited to repeat surgery, which has a relatively high recurrence rate, and long-term indwelling catheters. In the 3 patients in this study who developed recurrent obstructions, drainage catheters were left in place. Additional metallic stents were placed inside the original stents in the first patient, in the erroneous belief that the recurrent obstruction was due to fibrous overgrowth. When this patient became reobstructed at 4 months, a c h o l e d o c h o s c o p e was inserted, and biopsies were performed. The biopsy revealed mucosal hyperplasia with no evidence of malignancy (Fig. 2). In all cases of obstruction, the confirmed cause was mucosal hyperplasia. This is apparently a foreign body reaction, similar to the endothelial proliferation seen when metallic stents are placed in arteries [11]. Modification of the metallic stent material, such as covering it with a special coating, should reduce this reaction. It may be that laser resection via the choledochoscope of this hypertrophic tissue could allow the removal of the external drainage catheter. To date, this has not been attempted by US.
One point should be reemphasized. In patients who have undergone a high cholodochojejunostomy, near the hilum, stents need to be placed in both the right and left biliary systems to avoid compression of the neighboring ductal system It]. We agree with Rossi et al. [2] that only double " Z " stents should be used for biliary enteric anastomoses. This prevents dislodgement, and there have been no reported causes of ulcerations secondary to the " Z " stent extending into the bowel lumen, Lameris et al. [7] recently reported 2 cases of duodehal ulceration using the Wallstent (Schneider) and a case of c o m m o n bile duct perforation~ The difference in stent design may account for their incidence of perforation. Cure was not expected in the group with sclerosing cholangitis and, in fact, the initial hope was that prolonged patency could be achieved using the metallic " Z " stent. Although there was a longer period of time to obstruction than with simple balloon angioplasty, it became clear early on that there
370
H Coons: Metalhc S~ents for Bihary Ob,,truct~on
:;~,
,.,,
.".
:-ga{g ...,~..g.., . . "f.,,, ,. %, 9
I/...~
,r.'" I1
o~
,,,§
'
%..'~.., ' ~ ' . : , __ t : - 4 ,
D
< '
}~
"-..:?..:;~.,
.
,,,~,e,~p1~_~ " "'i~.'i;:,.;:,"c. :, ,.
, "'...,.~ Fig. 1. A Si'
