Impact of Rotational Atherectomy on Heavily Calcified, Unprotected Left Main Disease

– The New Tokyo Registry –

Abstract

Background: There is little data on percutaneous coronary intervention (PCI) using rotational atherectomy (Rota) for severely calcified unprotected left main (ULM) lesions.

Methods and Results: Between January 2005 and August 2011, 64 consecutive patients who underwent drug-eluting stent implantation using Rota were retrospectively evaluated. Of these, 54.7% and 20.3% patients had diabetes and were undergoing hemodialysis (HD), respectively. The mean EuroSCORE and SYNTAX score was 5.6 and 35.4, respectively. Procedural success, defined as residual stenosis <30%, was achieved in 95.3% of patients without fatal complications. Periprocedural myocardial infarction occurred in 7.8% patients. At the 1-year follow up, cardiac death was observed in 6.3% of patients, and target lesion revascularization (TLR) and TLR in the main branch (TLR-MB) were required in 18.8% and 10.9% patients, respectively. Optimal stent expansion was achieved in the majority of 33 patients with available intravascular ultrasound (IVUS) data. However, 5 of 9 HD patients who underwent IVUS required TLR-MB despite optimal stent expansion. The rate of TLR-MB was significantly lower in the non-HD patients than in the HD patients (2.1% vs. 46.2%; P=0.003).

Conclusions: PCI using Rota for calcified ULM lesions might guarantee high procedural success and a low complication rate. Although acceptable results were obtained at the 1-year follow up for non-HD patients, the rate of TLR-MB was considerably high for HD patients despite optimal stent expansion. (Circ J 2014; 78: 1867–1872)

Severely calcified lesions continue to remain a technically challenging and an important cause of in-stent restenosis (ISR) and stent thrombosis (ST) after the placement of drug-eluting stents (DES). Rotational atherectomy (Rota) has been reported to be effective in decreasing the incidence of ISR in calcified lesions without increasing the rate of fatal complications.^1,2

In contrast, with advanced technology and sophisticated techniques, percutaneous coronary intervention (PCI) for unprotected left main (ULM) lesions has become a common procedure for patients with low-to-intermediate SYNergy between PCI with TAXus and cardiac surgery (SYNTAX) tertile values.^3–9

However, data on the effectiveness of Rota in patients with calcified ULM lesions is scarce.¹⁰ Therefore, we evaluated the safety and feasibility of PCI using Rota for calcified ULM lesions.

Methods

Between January 2005 and August 2011, 64 consecutive patients who underwent PCI using Rota for de novo calcified ULM lesions were retrospectively evaluated (Figure A). The decision to perform PCI, and not CABG, was made if patients were found to have feasible anatomic and lesion characteristics for stenting without any contraindications for at least 6 months of dual antiplatelet therapy, and fulfilled at least one of the following criteria: high surgical risk, defined by a EuroSCORE of ≥6 (European System for Cardiac Operative Risk evaluation), or refusal to undergo CABG according to the IRB-approved patient information brochure. All patients were carefully informed about the alternative treatment options and PCI-related risks before they provided written informed consent to undergo the procedure. Furthermore, when the intravascular ultrasound (IVUS) catheter could not be passed through the severe lesions, when IVUS detected near-circumferential calcification, or when the lesion did not expand following balloon angioplasty (POBA), the decision for Rota use was left to the discretion of the attending physician. Temporary pacing was mandatory during Rota. If the slow-flow phenomenon occurred after Rota, 100 μg of sodium nitroprusside and 10 μg of noradrenalin were iteratively administered to improve coronary flow and maintain hemodynamics.

Figure.

(A) Study population. (B) Three-dimensional (3D) frequency-domain-optical coherence tomography (FD-OCT) assessment of stent constriction. (a-I) 3D FD-OCT reconstruction of the left coronary artery after stent implantation in a patient undergoing hemodialysis (HD). Longitudinal assessment of stent expansion is shown in (b-I), whereas (c-I) reveals the stent relationship with calcium deposition (highlighted in light grey, red arrows). At the midterm follow up, 3D reconstruction demonstrates late luminal loss (a-II, red arrows). 3D stent rendering demonstrates marked constriction (b-II, red arrows) and its relationship with calcium deposition in the vessel (c-II, red arrows). In d-I and d-II, respectively, baseline and follow-up 3D views of the region of interest demonstrate stent structure (white arrows) and its relationship with calcium deposition (highlighted in light grey). Red, white, and green asterisks represent the unprotected left main coronary artery, ostium of the left circumflex artery, and the left anterior descending artery (LAD), respectively.¹⁸ (C) Stent recoil documented by intravascular ultrasound (IVUS) in patients undergoing HD. Rotational atherectomy results in optimal stent expansion after stent implantation, as assessed by angiography (a-1 – d-1) and IVUS (a-2 – d-2) [minimum stent area (MSA): a, 6.58 mm²; b, 8.71 mm²; c, 11.77 mm²; d, 6.39 mm² ]. During the chronic phase, the occurrence of in-stent restenosis (ISR) (TLR-MB) was high in HD patients (a-3 – d-3). Angiography shows narrowing in the distal left main coronary artery up to the LAD. IVUS shows a decreased minimal stent area caused by severe calcified plaque (a-4 – d-4) (MSA: a, 2.88 mm²; b, 3.55 mm²; c, 5.13 mm²; d, 3.32 mm²).

Antiplatelet regimens included low-dose aspirin, which was indefinitely recommended, and thienopyridine (200–250 mg of ticlopidine twice a day or 75 mg of clopidogrel daily) for a minimum of 12 months after PCI. Clinical data were collected when patients had hospital visits or telephone interviews at 6-month intervals. Angiographic follow up was scheduled between 6 and 12 months or earlier if non-invasive evaluation or clinical presentation suggested the presence of ischemia. Quantitative coronary analysis (QCA) assessment was performed by 3 independent investigators.

The ULM lesions and their characteristics were previously described.^11,12 Renal dysfunction was defined by an estimated glomerular filtration rate (e-GFR) of <60 ml·min^–1 ·1.73 m^–2. Clinical risk was defined according to the EuroSCORE (low risk, ≤2; intermediate risk, 3–5; and high risk, ≥6) and the SYNTAX score (low, 0–22; intermediate, 23–32; and high, ≥33).

Study End-Points

The study end-points were major adverse cardiovascular events (MACE), defined as cardiac death, myocardial infarction (MI), or requirement of target lesion revascularization (TLR) at the 1-year follow up. Furthermore, a composite of MACE and TLR in the main branch (TLR-MB), which included left main and the left anterior descending artery (LAD), were evaluated. Death was considered to be of cardiac origin unless obvious non-cardiac causes could be identified. TLR was defined as either PCI (POBA or DES) or CABG performed to treat ISR or ST of the target lesion, including the proximal and distal edges of the stent, and/or the ostium of the side branch. TLR-MB was defined as the target lesion involving any ULM segment from the ULM ostium to the proximal LAD with or without left circumflex artery (LCx) involvement. Spontaneous MI and ST were defined according to the Academic Research Consortium (ARC).¹³ Procedural success was defined as a residual diameter stenosis evaluated by an offline QCA of <30% in the left main-main branch. In this study, LCx stenosis was not evaluated because the patency of the LM-LAD was considered an important end-point; furthermore, it was difficult to evaluate stenosis of the LCx artery because of the presence of a small vessel with severe stenosis in some cases. Optimal stent expansion was defined as a minimum stent area (MSA) of ≥8.2 cm² within the LM, including the polygon of confluence, and a MSA of ≥6.3 cm² in the ostial LAD¹⁴ on IVUS images. Periprocedural MI was defined as the presence of pathological and new Q waves on an electrocardiogram or an increase in the creatine kinase-myocardial band level to >3 times the upper limit of the normal range.

Statistical Analysis

All statistical analyses were conducted using SPSS software (SPSS version 18.0, Tokyo, IBM, Japan). Continuous variables are expressed as mean±standard deviation, while categorical variables are expressed as number and percentage. The time until the event was calculated using Kaplan-Meier analysis. Event-free survival was compared between groups using the log-rank test. All reported P-values are 2-sided, and values of P<0.05 were considered statistically significant.

Results

Baseline clinical lesion and procedural characteristics are shown in Tables 1 and 2. The mean age of patients was 71.4 years, and 67.2% were male. From the total number of patients, 54.7% had diabetes mellitus (DM) and 20.3% were receiving hemodialysis (HD). In terms of risk stratification, the mean standard EuroSCORE was 5.6, and a total of 50% patients had a EuroSCORE of ≥6. The mean SYNTAX score was 35.4; 57.8% of patients had a SYNTAX score of ≥33. Furthermore, 60.9% of patients had ULM lesions with 3-vessel disease. The preprocedural minimal stent diameter as assessed by QCA was 1.13±0.75 mm, while the postprocedural diameter was 3.33±0.53 mm (Table 3). Although IVUS-guided PCI was performed for 47 patients, MSA at the end of the procedure was measured only in 33 patients in whom the mean postprocedural MSA was 12.45 cm² in the LM and 8.28 cm² in the LAD. IVUS findings demonstrated that the majority of patients achieved optimal stent expansion, with an MSA of >8.2 cm² in the LM and >6.3 cm² in the proximal LAD (Table 4). All 9 HD patients who underwent IVUS achieved optimal expansion in both the LM and LAD.

Table 1. Baseline Clinical Characteristics of Patients Treated for ULM With Rotational Atherectomy

	All patients (n=64)
Age (years)	71.37±8.72
Male gender, n (%)	43 (67.2)
Previous MI, n (%)	22 (34.4)
Previous stroke, n (%)	9 (14.1)
Previous PCI, n (%)	38 (59.4)
DM, n (%)	35 (54.7)
Insulin DM, n (%)	8 (12.5)
Hypertension, n (%)	52 (81.3)
Dyslipidemia, n (%)	42 (65.6)
PAD, n (%)	17 (26.6)
Renal dysfunction, n (%) (eGFR <60)	27 (42.2)
Dialysis, n (%)	13 (20.3)
EF (%)	57.36±10.44
EF <35%, n (%)	5 (7.8)
EuroSCORE (standard)	5.57±3.00
EuroSCORE ≥6, n (%)	32 (50.0)

Data are presented as percentages and absolute numbers or mean±standard deviation, unless otherwise specified.

DM, diabetes mellitus; EF, ejection fraction; eGFR, estimated glomerular filtration rate; MI, myocardial infarction; PAD, peripheral artery disease; PCI, percutaneous coronary intervention; ULM, unprotected left main.

Table 2. Baseline Angiographic and Procedural Characteristics of Patients Treated for ULM With Rotational Atherectomy

	All patients (n=64)
Distal bifurcation, n (%)	63 (98.4)
ULM + 3VD, n (%)	39 (60.9)
True-bifurcation (medina 111, 101, 011), n (%)	47 (73.4)
Calcification, n (%)	64 (100)
Syntax score, n (%)	35.37±11.18
High Syntax (>33), n (%)	37 (57.8)
IABP, n (%)	8 (12.5)
IVUS, n (%)	47 (73.4)
Rota, n (%)	64 (100)
2 stent strategy, n (%)	17 (26.6)
Final kissing balloon inflation, n (%)	41 (64.1)
Ostium of LM covered, n (%)	53 (82.8)
Post dilatation, n (%)	40 (62.5)
1st DES, n (%)	46 (71.9)
Rotational atherectomy to LAD, n (%)	59 (92.2)
Rotational atherectomy to LCx, n (%)	9 (14.1)
Stent size, mm	3.35±0.25
Stent length, mm	23.38±6.29

Data are presented as percentages and absolute numbers or mean±standard deviation, unless otherwise specified.

3VD, 3 vessel disease; DES, drug-eluting stent; IABP, intra aorta balloon pumping; IVUS, intravascular ultrasound; LAD, left anterior descending artery; LCx, left circumflex artery; LM, left main. Other abbreviations as in Table 1.

Table 3. Quantitative Coronary Angiography Findings

	All patients (n=64)
Pre procedure
Pre RD, mm	2.95±0.78
Pre MLD, mm	1.13±0.75
Pre % stenosis, %	59.69±23.75
Post procedure
Post RD, mm	3.52±0.62
Post MSD, mm	3.33±0.53
Post % stenosis, %	5.90±9.61

Data are presented as mean±standard deviation.

MLD, minimum lesion diameter; MSD, minimum stent diameter; RD, reference diameter.

Table 4. IVUS Findings

	Available IVUS finding in patients with ULM (n=33)
Pre procedure LM including POC
Pre MLA, mm2	8.58±3.90
Pre EEM, mm2	20.68±4.63
Pre % stenosis, mm2	57.58±16.38
Post procedure LM including POC
Post MSA, mm2	12.45±3.82
Post MSA >8.2 mm2, n (%)	30 (88.2)
Post EEM, mm2	21.99±3.93
Post % stenosis, %	42.68±14.51
Pre procedure LAD just
Pre MLA, mm2	4.46±1.83
Pre EEM, mm2	15.42±4.09
Pre % stenosis, %	69.67±12.68
Post procedure LAD just
Post MSA, mm2	8.28±2.12
Post MSA >6.3 mm2, n (%)	26 (76.4)
Post EEM, mm2	16.37±5.21
Post % stenosis, %	55.61±12.18

Data are presented as percentages and absolute numbers or mean±standard deviation, unless otherwise specified.

EEM, external elastic membrane; MLA, minimum lesion area; MSA, minimum stent area; POC, polygon of confluence. Other abbreviations as in Tables 1,2.

Procedural success, defined as residual stenosis <30%, was achieved in 95.3% of patients. There were no periprocedural deaths or perforations, and periprocedural MI occurred in 5 (7.8%) patients. However, 1 patient developed definite ST at 8 days after PCI because of the discontinuation of dual antiplatelet therapy, while 1 patient developed probable ST at 17 days. At the 1-year follow up, MACE occurred in 15 (23.4%) patients. Cardiac death occurred in 4 (6.3%) patients and TLR occurred in 12 (18.8%). The rate of TLR-MB was significantly lower in the non-HD patients (2.1%) than in the HD patients (46.2%; P=0.003; Tables 5 and 6). Notably, 5 of the 9 HD patients who underwent IVUS required TLR-MB despite optimal stent expansion.

Table 5. Clinical Outcome in Patients Treated for ULM With Rotational Atherectomy (n=64)

Peri procedural outcome
Peri procedural MI, n (%)	5 (7.8)
Perforation/rupture, n (%)	0
Peri procedural death, n (%)	0
Procedural success, n (%)	61 (95.3)
Clinical outcome at 1 year
Follow-up angiography, n (%)	57 (89.1)
Clinical follow up, n (%)	64 (100)
MACE, n (%)	15 (23.4)
All cause death, n (%)	6 (9.4)
Cardiac death, n (%)	4 (6.3)
TLR, n (%)	12 (18.8)
TLR-MB, n (%)	7 (10.9)
TLR-MB in non-HD patients (n=51), n (%)	1 (2.1)
TLR-MB in HD patients (n=13), n (%)	6 (46.2)
MI, n (%)	3 (4.7)
Definite/Probable ST, n (%)	2 (6.1)
Possible ST, n (%)	2 (6.1)

Outcome rates were derived from Kaplan-Meier curves.

HD, hemodialysis; MACE, major adverse cardiovascular events; MB, main branch; ST, stent thrombosis; TLR, target lesion revascularization. Other abbreviations as in Table 1.

Table 6. Events During the Follow-up Period in Patients Treated for ULM With Rota

No.	Type of MACE	Days from PCI	Cardiac death from PCI	DAPT	HD	Syntax score	EuroScore	Age	EF	Stent type	MSA in LM	MSA in LAD
1	Cardiac death/Definite ST TLR-MB in ostial LAD; 99%	8	Y/8	N	N	38.0	10	81	32	SES	10.56	5.1
2	Cardiac death/probable ST	17	Y/17	Y	N	35.5	7	77	47	EES	NA	NA
3	Pneumonia/AMI	135	Y/135	N	N	37.0	3	74	55	SES	NA	NA
4	TLR-MB in LM-LAD; 50–75%	175	Y/283	Y	Y	24.0	10	68	31	SES	17.10	9.3
5	TLR-MB in ostial LAD; 75%	224	N	Y	Y	25.0	9	69	64	SES	NA	NA
6	TLR-MB in LAD stent distal edge	337	N	Y	Y	25.0	6	72	63	SES	24.7	11.0
7	TLR-MB in ostial LAD; 75%	357	N	Y	Y	25.0	5	49	66	PES	13.10	8.8
8	TLR-MB in LM; 75–90%	360	N	Y	Y	21.0	6	69	61	SES	17.58	10.4
9	TLR-MB in ostial LAD; 75%	363	N	Y	Y	24.0	6	50	51	SES	11.81	10.1
10	TLR-SB in LCx; 99%	107	N	Y	N	42.0	3	68	60	SES	NA	NA
11	TLR-SB in LCx; 90%	203	N	Y	N	51.0	5	80	64	SES	NA	NA
12	TLR-SB in LCx; 99%	212	N	Y	N	46.0	9	79	66	SES	NA	NA
13	TLR-SB in LCx; 99%	225	N	Y	N	36.0	9	81	61	SES	9.70	6.1
14	TLR-SB in LCx; 99%	227	N	Y	N	38.0	2	69	64	EES	11.10	6.9
15	TLR-SB in LCx; 75–90%	232	N	Y	N	33.0	7	80	65	SES	NA	NA

AMI, acute myocardial infarction; DAPT, dual antiplatelet therapy; EES, everolimus-eluting stent; N, no; PES, paclitaxel-eluting stent; SB; side branch; SES, sirolimus-eluting stent; Y, yes. Other abbreviations as in Tables 1,2,4,5.

Discussion

The main findings of the present study are as follows:

1. PCI using Rota for calcified ULM lesions demonstrated high procedural success and a low rate of fatal complications.

2. IVUS demonstrated that the majority of patients achieved optimal stent expansion in the LM and proximal LAD.

3. The incidence of TLR-MB was low in the non-HD patients, while almost 50% of HD patients required TLR-MB despite optimal postprocedural stent expansion.

The use of PCI for ULM lesions has increased in recent years because of new stent technologies and adjunctive pharmacotherapies.^4,7,15–17 However, PCI continues to be technically challenging in patients with severely calcified ULM lesions. Practice guidelines recommend the use of Rota for the treatment of heavily calcified or severely fibrotic lesions that cannot be bypassed by a balloon or adequately dilated before planned stenting.¹⁷

PCI using Rota for LM lesions was reported to be feasible despite the high hospital mortality rate (7.5%).¹⁰ In the present study, the in-hospital mortality rate was 0% and the 30-day mortality rate was 3.1%; the latter was because of ST in 2 patients. In general, patients with severely calcified lesions are at a very high risk and have a poor prognosis in the short and medium terms.¹⁸ In this study, the cardiac mortality rate at the 1-year follow up was 6.3%, which is considered acceptable because our study population had severely calcified lesions, high SYNTAX scores, and high EuroSCOREs. During Rota for calcified ULM lesions, no-reflow and consequent hypotension seem to be inevitable. We performed intra aorta balloon pumping (IABP) as a prophylactic measure in 8 patients with a high potential risk of hypotension or cardiac shock due to low ejection fraction or severe 3 vessel disease. No patient required emergency IABP during PCI. Furthermore, we routinely administered sodium nitroprusside to treat the no-reflow phenomenon, followed by noradrenaline to restore hemodynamics. Therefore, adequate preparation, including catecholamine therapy or mechanical support, is necessary to prevent fatal complications in select patients.

In our registry, 73.4% patients underwent IVUS-guided PCI, and IVUS demonstrated optimal stent expansion in almost 80% patients, indicating that Rota is apparently effective for optimal stent expansion over severely calcified lesions.

Notably, our registry demonstrated that 6 HD patients and 1 non-HD patient required TLR-MB (46.2% vs. 2.1%, P=0.003). Although most HD patients who underwent IVUS-guided PCI successfully achieved optimal expansion¹⁴ in the LM-LAD, ISR occurred in 6 of the 13 patients. The most likely explanations for this observation are stent recoil, excessive neointimal tissue, and variability due to the small sample population. Stent recoil in calcified lesions was first reported by Tanabe et al,¹⁹ and 1 representative case was previously reported from our institute.²⁰ Severely calcified lesions might continuously compress the stent, resulting in ISR in the chronic phase of disease (Figures B, C). Episodic serum Ca level increases, as observed during HD or with the use of vitamin D analogs or Ca-based P binders, might potentially influence vascular calcification in HD patients.¹⁹

Furthermore, HD usually presents concomitantly with systematic diseases such as DM and hypertension, which cause the progression of in-stent neointimal hyperplasia as a consequence of inflammatory responses. Our results support those of previous studies concluding that the decrease in survival of HD patients treated with PCI compared with that of patients treated with CABG might be related to an increased risk of restenosis and ST.^21–23 They also support the results of studies indicating that CABG is superior to PCI as a treatment for patients with severe renal dysfunction.^24,25

Therefore, a dedicated follow-up study is necessary, particularly for HD patients, even when IVUS shows sufficient stent expansion in LM-LAD lesions, although PCI using Rota might be a reasonable treatment option for patients with severely calcified ULM stenosis who are not suitable for surgery and have high EuroSCOREs.

Study Limitations

The primary limitations of the present study are the small cohort of patients and the lack of randomization and a CABG arm. Therefore, in order to clarify the feasibility and efficacy of PCI using Rota in patients with calcified ULM lesions, more procedural experience, a longer-term follow-up period, and a larger study sample are required to evaluate the role of CABG. According to current guidelines, CABG is the gold standard treatment for patients with ULM lesions and a high SYNTAX score. Therefore, patients who undergo PCI should be carefully selected after being provided with adequate information about confirmed CABG therapy and PCI-related risks.

In this study, final IVUS data were available only for 51.5% patients; this was not enough to guarantee optimal expansion following LM-PCI using Rota. Furthermore, the influence of the LCx artery was not considered in this study. Further randomized trials dedicated to assessment of the ULM bifurcation, including the LCx artery, using IVUS are required.

Conclusions

The use of Rota might guarantee high procedural success and a low complication rate for severely calcified ULM lesions. The outcomes in non-HD patients were acceptable at the 1-year follow up, while TLR-MB was required in almost 50% of HD patients despite optimal stent expansion. Therefore, patients should be carefully evaluated before they have PCI performed on them for calcified ULM lesions, and maximum efforts should be made to prevent early ST.

Disclosures

None.

References

• 1.    Hoffmann R, Mintz GS, Kent KM, Pichard AD, Satler LF, Popma JJ, et al. Comparative early and nine-month results of rotational atherectomy, stents, and the combination of both for calcified lesions in large coronary arteries. Am J Cardiol 1998; 81: 552–557.
• 2.    Moussa I, Di Mario C, Moses J, Reimers B, Di Francesco L, Martini G, et al. Coronary stenting after rotational atherectomy in calcified and complex lesions: Angiographic and clinical follow-up results. Circulation 1997; 96: 128–136.
• 3.    Patel MR, Dehmer GJ, Hirshfeld JW, Smith PK, Spertus JA. ACCF/SCAI/STS/AATS/AHA/ASNC 2009 Appropriateness Criteria for Coronary Revascularization: A Report by the American College of Cardiology Foundation Appropriateness Criteria Task Force, Society for Cardiovascular Angiography and Interventions, Society of Thoracic Surgeons, American Association for Thoracic Surgery, American Heart Association, and the American Society of Nuclear Cardiology Endorsed by the American Society of Echocardiography, the Heart Failure Society of America, and the Society of Cardiovascular Computed Tomography. J Am Coll Cardiol 2009; 53: 530–553.
• 4.    Kim YH, Park DW, Lee SW, Yun SC, Lee CW, Hong MK, et al. Long-term safety and effectiveness of unprotected left main coronary stenting with drug-eluting stents compared with bare-metal stents. Circulation 2009; 120: 400–407.
• 5.    Chieffo A, Morici N, Maisano F, Bonizzoni E, Cosgrave J, Montorfano M, et al. Percutaneous treatment with drug-eluting stent implantation versus bypass surgery for unprotected left main stenosis. Circulation 2006; 113: 2542–2547.
• 6.    Park SJ, Kim YH, Lee BK, Lee SW, Lee CW, Hong MK, et al. Sirolimus-eluting stent implantation for unprotected left main coronary artery stenosis: Comparison with bare metal stent implantation. J Am Coll Cardiol 2005; 45: 351–356.
• 7.    Morice MC, Serruys PW, Kappetein AP, Feldman TE, Stahle E, Colombo A, et al. Outcomes in patients with de novo left main disease treated with either percutaneous coronary intervention using paclitaxel-eluting stents or coronary artery bypass graft treatment in the synergy between percutaneous coronary intervention with TAXUS and cardiac surgery (SYNTAX) trial. Circulation 2010; 121: 2645–2653.
• 8.    Kubo S, Kadota K, Shimada T, Ozaki M, Ichinohe T, Eguchi H, et al. Seven-year clinical outcomes of unprotected left main coronary artery stenting with drug-eluting stent and bare-metal stent. Circ J 2013; 77: 2497–2504.
• 9.    Alam M, Huang HD, Shahzad SA, Kar B, Virani SS, Rogers PA, et al. Percutaneous coronary intervention vs. coronary artery bypass graft surgery for unprotected left main coronary artery disease in the drug-eluting stents era: An aggregate data meta-analysis of 11,148 patients. Circ J 2013; 77: 372–382.
• 10.    Garcia-Lara J, Pinar E, Valdesuso R, Lacunza J, Gimeno JR, Hurtado JA, et al. Percutaneous coronary intervention with rotational atherectomy for severely calcified unprotected left main: Immediate and two-years follow-up results. Catheter Cardiovasc Interv 2012; 80: 215–220.
• 11.    Takagi K, Ielasi A, Chieffo A, Basavarajaiah S, Latib A, Montorfano M, et al. Impact of residual chronic total occlusion of right coronary artery on the long-term outcome in patients treated for unprotected left main disease: The Milan and New-Tokyo Registry. Circ Cardiovasc Interv 2013; 6: 154–160.
• 12.    Takagi K, Ielasi A, Shannon J, Latib A, Godino C, Davidavicius G, et al. Clinical and procedural predictors of suboptimal outcome after the treatment of drug-eluting stent restenosis in the unprotected distal left main stem. Circ Cardiovasc Interv 2012; 5: 491–498.
• 13.    Laskey WK, Yancy CW, Maisel WH. Thrombosis in coronary drug-eluting stents: Report from the Meeting of the Circulatory System Medical Devices Advisory Panel of the Food and Drug Administration Center for Devices and Radiologic Health, December 7–8, 2006. Circulation 2007; 115: 2352–2357.
• 14.    Kang SJ, Ahn JM, Song H, Kim WJ, Lee JY, Park DW, et al. Comprehensive intravascular ultrasound assessment of stent area and its impact on restenosis and adverse cardiac events in 403 patients with unprotected left main disease. Circ Cardiovasc Interv 2011; 4: 562–569.
• 15.    Tamburino C, Di Salvo ME, Capodanno D, Palmerini T, Sheiban I, Margheri M, et al. Comparison of drug-eluting stents and bare-metal stents for the treatment of unprotected left main coronary artery disease in acute coronary syndromes. Am J Cardiol 2009; 103: 187–193.
• 16.    Toyofuku M, Kimura T, Morimoto T, Hayashi Y, Ueda H, Kawai K, et al. Three-year outcomes after sirolimus-eluting stent implantation for unprotected left main coronary artery disease: Insights from the j-Cypher registry. Circulation 2009; 120: 1866–1874.
• 17.   Task Force on Myocardial Revascularization of the European Society of Cardiology (ESC) and the European Association for Cardio-Thoracic Surgery (EACTS); European Association for Percutaneous Cardiovascular Interventions (EAPCI),  Wijns W, Kolh P, Danchin N, Di Mario C, Falk V, Folliguet T, et al. Guidelines on myocardial revascularization.: Insights from the j-Cypher registry. Eur Heart J 2010; 31: 2501–2555.
• 18.    Williams M, Shaw LJ, Raggi P, Morris D, Vaccarino V, Liu ST, et al. Prognostic value of number and site of calcified coronary lesions compared with the total score. JACC: Cardiovascular Imaging 2008; 1: 61–69.
• 19.    Tanabe K, Kishi S, Aoki J, Tanimoto S, Onuma Y, Yachi S, et al. Impact of coronary calcium on outcome following sirolimus-eluting stent implantation. Am J Cardiol 2011; 108: 514–517.
• 20.    Fujino Y, Attizzani GF, Nakamura S, Costa MA, Bezerra HG. Frequency-domain optical coherence tomography assessment of stent constriction 9 months after sirolimus-eluting stent implantation in a highly calcified plaque. JACC Cardiovasc Interv 2013; 6: 204–205.
• 21.    Azar RR, Prpic R, Ho KKL, Kiernan FJ, Shubrooks SJ, Baim DS, et al. Impact of end-stage renal disease on clinical and angiographic outcomes after coronary stenting. Am J Cardiol 2000; 86: 485–489.
• 22.    Schoebel FC, Gradaus F, Ivens K, Heering P, Jax TW, Grabensee B, et al. Restenosis after elective coronary balloon angioplasty in patients with end stage renal disease: A case-control study using quantitative coronary angiography. Heart 1997; 78: 337–342.
• 23.    Otsuka Y, Ishiwata S, Inada T, Kanno H, Kyo E, Hayashi Y, et al. Comparison of haemodialysis patients and non-haemodialysis patients with respect to clinical characteristics and 3-year clinical outcomes after sirolimus-eluting stent implantation: Insights from the Japan multi-centre post-marketing surveillance registry. Eur Heart J 2011; 32: 829–837.
• 24.    Herzog CA, Ma JZ, Collins AJ. Comparative survival of dialysis patients in the United States after coronary angioplasty, coronary artery stenting, and coronary artery bypass surgery and impact of diabetes. Circulation 2002; 106: 2207–2211.
• 25.    Hemmelgarn BR, Southern D, Culleton BF, Mitchell LB, Knudtson ML, Ghali WA, et al. Survival after coronary revascularization among patients with kidney disease. Circulation 2004; 110: 1890–1895.