The Ostial Lesion
Naeem K. Tahirkheli
The coronary ostial lesions share the unique paradox of increased rigidity and elastic recoil (1,2). This has resulted in increased complexity of and suboptimal results from percutaneous intervention in these sites, including immediate lumen loss from recoil, higher late restenosis rates and reduced event-free survivals (3, 4, 5). Various techniques and devices have been used to achieve better results in treating these lesions. These include aggressive balloon-to-artery ratios, higher pressures, noncompliant balloons, various kinds of debulking devices, stents—bare metal and drug-eluting—and cutting balloons. Unfortunately, most of the randomized, prospective trials of percutaneous coronary interventions (PCI) have historically excluded ostial lesions and we, for the most part, must base our judgment on small series and case reports (6,7).
The term ostial lesion encompasses a variety of lesions that present distinct challenges to the interventionist while sharing some common features. The ostial lesions are best subdivided into more homogenous categories to adequately assess the impact of a therapeutic intervention. These include aorto-ostial (ostial left main coronary artery and ostial right coronary artery), non-aorto-ostial (ostial left anterior descending artery [LAD], ostial intermediate ramus (IR), and ostial left circumflex [LCX] artery stenoses), and branch ostial stenoses (diagonal, obtuse marginal, posterolateral, and posterior descending arterial stenoses). Ostial vein-graft lesions are best categorized separately. This chapter discusses the unique features of each category of lesions; the focus is on isolated ostial stenoses and not on bifurcation lesions, which are discussed in Chapters 29 and 30.
PERCUTANEOUS TRANSLUMINAL CORONARY ANGIOPLASTY
The technical difficulties that are peculiar to aorto-ostial lesions include maintaining adequate guide catheter position and backup and the potential for guide catheter-induced dissection, intimal disruption and spasm, pressure dampening, catheter-induced ischemia, and suboptimal visualization of the lesion. The aorto-ostial lesions share the more ubiquitous characteristics of ostial lesions elsewhere, including both a significantly increased rigidity, which frequently requires noncompliant balloons, and an excessive elastic recoil, which necessitates oversize balloons and contributes to the occurrence of coronary dissection. In 1987, Topol et al. (3) reported on 53 patients who had undergone percutaneous transluminal coronary angioplasty (PTCA) of the right coronary ostium (within 3 mm of the orifice of the right coronary artery); procedural success (less than 50% residual stenosis without Q-wave myocardial infarction [MI], emergency surgery, or death) was reported in 42 patients (79%). Five patients (9.4%) required emergency surgery because of abrupt closure. Fairly high balloon inflation pressures were needed (9.8 ± 4 atm), quite high for the mid-1980s. These high pressures resulted in a significant amount of dissection; 21% (11 patients) had significant angiographic dissection. The follow-up was a mean of 10.5 months. Twenty of the 42 initially successfully treated patients had recurrence of angina. Six patients (11%) had repeat angioplasty and eight patients (15%) had elective coronary artery bypass grafting (CABG) surgery. Six patients were treated medically. Therefore, only 25 patients (47%) of the 53 treated initially had long-term success without the recurrence of angina, bypass surgery, or repeat angioplasty. The authors reported technical difficulties with guide catheter impaction, ostial trauma, inability to inflate the balloon with adequate guide catheter support, and need for increased intracoronary manipulation. They concluded that the angioplasty of right coronary ostial lesions resulted in suboptimal early success, with a high risk of emergency bypass surgery and high long-term restenosis rates.
The non-aorto-ostial lesions (ostial LAD, ostial LCX, and intermediate artery) present a few more substantial challenges. These include a large territory of blood supply
at risk; repeated manipulations needed in the left main coronary artery, which increases the risks of left main dissection; the potential of retrograde extension of dissection to the left main; and finally, the compromise of the contralateral branches, resulting in a left main equivalent lesion. In 1985, Whitworth et al. (8) reported 172 patients who had PTCA of the proximal LAD. Group 1 (30 patients) included patients with stenosis involving the origin of the LAD. Group 2 (26 patients) had patients whose lesions were within 3 mm of the origin of the LAD. Groups 3 (71 patients) and 4 (45 patients) involved LAD lesions proximal to the diagonal or septal perforator or distal to the origin of the diagonal or septal perforator, respectively. The initial PTCA results were similar in all groups, with post-PTCA stenosis of approximately 22% to 25%. However, the angiographic follow-up, which was available in all of these patients, showed a recurrence (loss of 50% of original gain) in 63% (19 of 30 patients) of Group 1 patients. Group 2 had a restenosis rate of 42% (11 of 26 patients). Group 3 had a restenosis rate of 34% (24 of 71 patients), and Group 4 had a rate of 42% (19 of 45 patients). Tan et al. (9) reported on acute and long-term outcomes of 198 patients who had coronary angioplasty of various ostial stenoses. Of these, 48 were non-aorto-ostial stenoses (LAD 31, IR 8, LCX 9). They reported a success rate of 90%. V. at Mayo Clinic also reported a comparison of PTCA and stent placement for non-aorto-ostial lesions (32). In this study, 95 patients had PTCA of the LAD or circumflex arteries. In the angioplasty cohort, 82.2% of the lesions were successfully dilated; however, the overall procedural success, defined as achieving angiographic success without occurrence of death, CABG, or Q-wave MI during the first 24 hours postprocedure, was only 63%. The patient population, however, was high risk, with 24% having acute MI and 65% of the remaining patients having had a prior MI.
at risk; repeated manipulations needed in the left main coronary artery, which increases the risks of left main dissection; the potential of retrograde extension of dissection to the left main; and finally, the compromise of the contralateral branches, resulting in a left main equivalent lesion. In 1985, Whitworth et al. (8) reported 172 patients who had PTCA of the proximal LAD. Group 1 (30 patients) included patients with stenosis involving the origin of the LAD. Group 2 (26 patients) had patients whose lesions were within 3 mm of the origin of the LAD. Groups 3 (71 patients) and 4 (45 patients) involved LAD lesions proximal to the diagonal or septal perforator or distal to the origin of the diagonal or septal perforator, respectively. The initial PTCA results were similar in all groups, with post-PTCA stenosis of approximately 22% to 25%. However, the angiographic follow-up, which was available in all of these patients, showed a recurrence (loss of 50% of original gain) in 63% (19 of 30 patients) of Group 1 patients. Group 2 had a restenosis rate of 42% (11 of 26 patients). Group 3 had a restenosis rate of 34% (24 of 71 patients), and Group 4 had a rate of 42% (19 of 45 patients). Tan et al. (9) reported on acute and long-term outcomes of 198 patients who had coronary angioplasty of various ostial stenoses. Of these, 48 were non-aorto-ostial stenoses (LAD 31, IR 8, LCX 9). They reported a success rate of 90%. V. at Mayo Clinic also reported a comparison of PTCA and stent placement for non-aorto-ostial lesions (32). In this study, 95 patients had PTCA of the LAD or circumflex arteries. In the angioplasty cohort, 82.2% of the lesions were successfully dilated; however, the overall procedural success, defined as achieving angiographic success without occurrence of death, CABG, or Q-wave MI during the first 24 hours postprocedure, was only 63%. The patient population, however, was high risk, with 24% having acute MI and 65% of the remaining patients having had a prior MI.
Mathias et al. (5) reported on 106 patients with 119 ostial branch stenoses. Of these 65 (61%) were isolated ostial stenoses and 41 (39%) had associated bifurcation lesions. The results were not reported separately. There were 58 diagonal, 21 posterior descending, 34 obtuse marginal, and 6 intermediate artery ostial stenoses. Despite aggressive balloon sizing, with the balloon-to-artery ratio of 1.051, the angiographic success was reported to be 74% of the ostial branch stenosis versus 91% of non-ostial stenoses (p <0.01). Additionally, 13% had complications, including 4% CABG and 9% abrupt closure, as opposed to 5% of the non-ostial branch stenoses.
DEBULKING DEVICES
Directional Coronary Atherectomy
Because of the suboptimal results achieved using the angioplasty alone, considerable interest has arisen in various debulking devices for ostial stenoses. The best-studied debulking device to date is directional coronary atherectomy (DCA). More than 600 patient experiences with ostial stenosis have been reported. The Coronary Angioplasty versus Excisional Atherectomy Trial (CAVEAT-1) was a randomized prospective trial comparing the new device DCA versus balloon angioplasty (BA) alone. In all, 1,012 patients were randomized and treated in this trial (10). A total of 41 ostial LAD lesions were treated with DCA, and 33 ostial LAD lesions were treated with PTCA. Initial clinical success was 86% and 87% for DCA- and PTCA-treated ostial lesions, respectively. Dichotomous restenosis, as tabulated by an independent core laboratory, was 48% for DCA and 46% for PTCA (p = NS). Therefore, no obvious advantage of DCA over PTCA was recognized for the treatment of ostial LAD lesions in this trial. The criticism of this trial was that crossover from DCA to PTCA was discouraged; however, the current thinking is that the optimal use of DCA frequently should include adjunctive balloon angioplasty or stents to maximize minimum lumen diameter (MLD), as shown by Kuntz et al. (11). A subsequent trial, Balloon versus Optimal Atherectomy Trial (BOAT), randomized 294 patients with proximal LAD artery stenosis (12). Thirty-seven of these patients had ostial lesions, whereas the remaining 257 patients had proximal but not ostial lesions. Nineteen of the ostial LAD lesions underwent PTCA, whereas 18 were randomized to DCA. The DCA group had a larger postprocedure MLD: 3.04 mm for DCA versus 2.43 mm for PTCA (p = 0.0001). Similarly, acute gain was greater for DCA: 1.92 mm versus 1.25 mm for PTCA (p = 0.0001); the final diameter stenosis was only 8% for DCA versus 25% for PTCA (p = 0.0001). The comparative 30-day adverse events were not statistically significant. The nine-month follow-up revealed two PTCA patients (10.6%) and three DCA patients (16.9%) who had undergone target vessel revascularization (TVR) (p = NS). The restenosis rate was, however, 20% in DCA patients and 54.9% in PTCA patients. This also was statistically not significant (p = 0.10). However, the cohort size was fairly small, and a trend favoring the DCA can be seen.
Ostial right coronary artery DCA was reported in seven consecutive patients by Popma et al. (13). It was reported as successful in six of the seven patients (85.7%), and follow-up angiography in 6.2 ± 2.7 months after successful atherectomy revealed one patient (16.7%) to have developed restenosis. Kerwin et al. (14) reported successful DCA of 14 of 15 right coronary artery ostial lesions. Nine of the fourteen successfully treated patients had repeat cardiac catheterization; three (33%) had restenosis. They also reported on eight ostial saphenous venous graft (SVG) lesions, which had a 100% success rate and a 50% restenosis rate in those patients who had follow-up angiography. Wong et al. reported on 41 ostial SVG stenoses in 31 patients who underwent DCA (15). Procedural success occurred in 94.1% of the lesions. Only 42% of the patients had event-free survival at 12 months. The authors also compared the results of the DCA for ostial SVG lesions to that of
coronary stenting in 90 lesions (85 patients). No significant differences were noted in initial procedural success (96.5%), target lesion revascularization (32.8%), and 12-month event-free survival (52.8%). However, a trend favoring coronary stenting was noted.
coronary stenting in 90 lesions (85 patients). No significant differences were noted in initial procedural success (96.5%), target lesion revascularization (32.8%), and 12-month event-free survival (52.8%). However, a trend favoring coronary stenting was noted.
In summary, some encouraging results have been noted with DCA in ostial lesions; however, no clear-cut superiority over angioplasty or other debulking techniques has been identified, and further prospective studies are needed. Additionally, DCA continues to be a technically demanding procedure requiring a high level of expertise and experience.
Rotational Atherectomy
Rotational atherectomy has theoretical and practical advantages over DCA, excimer laser angioplasty, and transluminal extraction catheter atherectomy (TEC). The rotating burr that is used is able to ablate more of the calcified, fibrous, and unyielding plaque instead of the elastic arterial wall, which deflects the burr away. It is particularly useful in more calcified lesions, where DCA, TEC, or excimer laser angioplasty may not be the best devices to use. Additionally, rotablator seems to be the device of choice for smaller sized arteries and those with more angulation. Popma et al. were the first to report the results of 105 patients who underwent rotational atherectomy of ostial lesions (16). Fifty-two of these were aorto-ostial lesions (7 ostial left main and 45 ostial right coronary artery). The remaining 53 were non-aorto-ostial lesions involving the ostial LAD or ostial LCX artery. Seventy-four percent of the lesions were calcified. Procedural success was reported in 97% of the patients. Adjunctive BA was used in 85% of the patients. Two patients needed emergent or urgent coronary artery bypass. No procedure-related deaths were documented. Eight percent of the patients had non-Q-wave MI, defined for the study as greater than five times the upper normal limit of creatine phosphokinase-MB fraction (CK-MB). Lesser amounts of CK-MB elevations were not reported. Rotational atherectomy decreased the percent diameter stenosis from 73 ± 13% to 41 ± 14% (p <0.001). Adjunctive BA resulted in a 23 ± 14% final diameter stenosis (p <0.001). During the 5.4 ± 3.6 months’ follow-up, 35 of the 102 (34%) successfully treated patients developed recurrent symptoms. Seven patients underwent coronary artery bypass surgery, and eleven underwent repeat coronary angioplasty. Four patients died during the follow-up, three from cardiac causes. The authors concluded that rotational coronary atherectomy is an effective alternative treatment in patients with coronary ostial lesions, and this technique may be particularly useful in ostial lesions located in smaller vessels and in lesions with extensive calcium or angulation. Note that the average reference arterial segment diameter was 2.6 mm, and 29 of the 105 patients in the study had a lesion angulation >45 degrees.
Koller et al. retrospectively studied 101 patients with ostial stenoses that were either treated by Rotablator (n = 29) or TEC atherectomy (n = 72) over a 3-year period (17). The Rotablator was primarily used in native vessel ostial lesions. Procedural success without major complications was in excess of 90% with each device. Major complications were also similar in TEC atherectomy (4.2%) and Rotablator (6.9%). Sixty of the seventy-two TEC atherectomy patients had follow-up angiography. Restenosis occurred in 59% of the native coronary ostial lesions and in 80% of the SVG aorto-ostial lesions. Of the 29 Rotablator patients, 28 had follow-up angiography, and a dichotomous restenosis rate of 39% was noted.
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