1

Introduction

Coronary artery disease is highly prevalent in end-stage kidney disease patients requiring chronic hemodialysis (HD); a high-risk population in whom cardiovascular disease is the principle cause of death , and in whom myocardial infarction (MI) is a much stronger predictor of risk compared to the general population .

An increased incidence of target lesion restenosis (TLR) has been recognized in HD patients after percutaneous coronary intervention (PCI) with bare metal stents . This can be attributed to the presence of extensive calcification and lesion complexity, a high prevalence of diabetes mellitus (DM) and a heightened pro-inflammatory state . The use of drug-eluting stents (DES) as a better alternative, is conceivable in patients receiving chronic HD, but this notion is limited by the fact that randomized clinical trials typically exclude such patients, and as a result, DES performance data in this population are very limited. Some observational studies have reported lower rates of repeat revascularization with paclitaxel-eluting stents (PES) compared to sirolimus-eluting stents in patients receiving chronic HD . However, the mechanism for this presumed PES advantage has not been clarified, and the observation has not been confirmed in a randomized clinical trial.

Here we aimed to evaluate the use of various DES types on a relatively large population of patients treated with chronic HD and to specifically assess whether the use of PES in this population carries a significant advantage when compared to other available DES types.

2

Methods

Clinical, procedural and follow-up data were prospectively collected for consecutive patients on chronic HD undergoing PCI with stenting from January 2000 to December 2010. Chronic HD was defined as regular dialysis treatment for ≥ 30 days. The TAXUS® PES (Boston Scientific Corporation, Natick, MA) was used, and then compared to sirolimus-eluting (CYPHER®, Cordis Corporation, Bridgewater, NJ) and everolimus-eluting stents [XIENCE® (Abbott Vascular, Santa Clara, CA) or PROMUS® (Boston Scientific, Natick, MA)], herein grouped as limus-eluting stents (LES).

The institutional review boards of MedStar Washington Hospital Center and MedStar Health Research Institute (Washington, DC) approved this study. Experienced staff at a dedicated data-coordinating center performed all data collection, entry, and analysis. Data regarding baseline clinical and procedural data, together with post-procedure in-patient events, were obtained from hospital chart review. Clinical follow-up at 30 days, 6 months and 1 year was conducted via telephone contact or office visits. Primary source documents for all events were obtained and adjudicated by physicians not involved in the procedures and who were unaware of the objectives of the study.

PCI was performed according to guidelines current at procedure time. In all cases, interventional strategy and choice of peri-procedural and discharge medications were at the responsible physician’s discretion. Anticoagulation regimens included either bivalirudin 0.75 mg/kg followed by an infusion of 1.75 mg/kg/h for the duration of the procedure or unfractionated heparin to achieve an activated clotting time of 200–300 s in all patients. All patients received an aspirin loading dose of 325 mg and were prescribed 81–325 mg once daily indefinitely. After a clopidogrel loading dose of 300–600 mg, patients were prescribed 75 mg once daily for ≥ 6 months.

The primary end point was defined as major adverse cardiac events (MACE), the composite of all-cause mortality, Q-wave myocardial infarction, and TLR at 2 years’ follow up. The secondary end point was the individual outcome of TLR at 2 years. Academic Research Consortium definitions for stent thrombosis were used . Q-wave myocardial infarction was defined as an elevation of creatine kinase-MB ≥ 3 times the upper normal value in the presence of new pathologic Q waves (> 0.4 s) in ≥ 2 contiguous leads of the electrocardiogram. TLR was defined as clinically driven revascularization of the index lesion. PCI angiographic success was defined as a residual stenosis of < 30% with Thrombolysis in Myocardial Infarction grade 3 flow. Clinical success was defined as angiographic success plus the absence of TLR, Q-wave myocardial infarction, or death prior to hospital discharge. Major bleeding was defined using the Thrombolysis in Myocardial Infarction criteria . Vascular complications were defined as the presence of a large hematoma (≥ 5 cm), fistula, or pseudoaneurysm formation, retroperitoneal bleeding, or the need for surgical repair.

Statistical analysis was performed using SAS version 9.1 (SAS Institute Inc., Cary, NC). Normally distributed continuous variables are presented as mean ± SD. Those not normally distributed are shown as median ± interquartile range. Categorical variables are expressed as frequencies and percentages. Baseline characteristics were compared using Student’s t test for parametric variables or the Mann–Whitney U test when not normally distributed. Categorical variables were compared using the chi-square test or Fisher’s exact test as appropriate. Two-year outcomes were compared with the log-rank test and are presented by Kaplan–Meier percentages.

To test the independent effect of DM and angiographic lesion complexity over TLR at 2 years in patients with end-stage renal disease, a multivariable Cox regression model was constructed with the following variables: History of DM, American College of Cardiology/American Heart Association (ACC/AHA) type C lesion, and use of PES. These variables were chosen based on a value for p < 0.1 on univariable analysis or because they were considered clinically relevant. The proportional hazards assumption was assessed by Kolmogorov-type Supremum test. Only patients with data present for all co-variables were included. A p value < 0.05 was considered statistically significant. To evaluate if death before TLR occurrence confounded the result for this end point, a competing outcome analysis was carried out over the entire cohort. To analyze whether the presence of DM would favor the performance of one type of DES over the other, a subgroup analysis was performed by restricting the population to those with a history of DM.

The authors of this manuscript have certified that they comply with the Principles of Ethical Publishing in the International Journal of Cardiology .

2

Methods

Clinical, procedural and follow-up data were prospectively collected for consecutive patients on chronic HD undergoing PCI with stenting from January 2000 to December 2010. Chronic HD was defined as regular dialysis treatment for ≥ 30 days. The TAXUS® PES (Boston Scientific Corporation, Natick, MA) was used, and then compared to sirolimus-eluting (CYPHER®, Cordis Corporation, Bridgewater, NJ) and everolimus-eluting stents [XIENCE® (Abbott Vascular, Santa Clara, CA) or PROMUS® (Boston Scientific, Natick, MA)], herein grouped as limus-eluting stents (LES).

The institutional review boards of MedStar Washington Hospital Center and MedStar Health Research Institute (Washington, DC) approved this study. Experienced staff at a dedicated data-coordinating center performed all data collection, entry, and analysis. Data regarding baseline clinical and procedural data, together with post-procedure in-patient events, were obtained from hospital chart review. Clinical follow-up at 30 days, 6 months and 1 year was conducted via telephone contact or office visits. Primary source documents for all events were obtained and adjudicated by physicians not involved in the procedures and who were unaware of the objectives of the study.

PCI was performed according to guidelines current at procedure time. In all cases, interventional strategy and choice of peri-procedural and discharge medications were at the responsible physician’s discretion. Anticoagulation regimens included either bivalirudin 0.75 mg/kg followed by an infusion of 1.75 mg/kg/h for the duration of the procedure or unfractionated heparin to achieve an activated clotting time of 200–300 s in all patients. All patients received an aspirin loading dose of 325 mg and were prescribed 81–325 mg once daily indefinitely. After a clopidogrel loading dose of 300–600 mg, patients were prescribed 75 mg once daily for ≥ 6 months.

The primary end point was defined as major adverse cardiac events (MACE), the composite of all-cause mortality, Q-wave myocardial infarction, and TLR at 2 years’ follow up. The secondary end point was the individual outcome of TLR at 2 years. Academic Research Consortium definitions for stent thrombosis were used . Q-wave myocardial infarction was defined as an elevation of creatine kinase-MB ≥ 3 times the upper normal value in the presence of new pathologic Q waves (> 0.4 s) in ≥ 2 contiguous leads of the electrocardiogram. TLR was defined as clinically driven revascularization of the index lesion. PCI angiographic success was defined as a residual stenosis of < 30% with Thrombolysis in Myocardial Infarction grade 3 flow. Clinical success was defined as angiographic success plus the absence of TLR, Q-wave myocardial infarction, or death prior to hospital discharge. Major bleeding was defined using the Thrombolysis in Myocardial Infarction criteria . Vascular complications were defined as the presence of a large hematoma (≥ 5 cm), fistula, or pseudoaneurysm formation, retroperitoneal bleeding, or the need for surgical repair.

Statistical analysis was performed using SAS version 9.1 (SAS Institute Inc., Cary, NC). Normally distributed continuous variables are presented as mean ± SD. Those not normally distributed are shown as median ± interquartile range. Categorical variables are expressed as frequencies and percentages. Baseline characteristics were compared using Student’s t test for parametric variables or the Mann–Whitney U test when not normally distributed. Categorical variables were compared using the chi-square test or Fisher’s exact test as appropriate. Two-year outcomes were compared with the log-rank test and are presented by Kaplan–Meier percentages.

To test the independent effect of DM and angiographic lesion complexity over TLR at 2 years in patients with end-stage renal disease, a multivariable Cox regression model was constructed with the following variables: History of DM, American College of Cardiology/American Heart Association (ACC/AHA) type C lesion, and use of PES. These variables were chosen based on a value for p < 0.1 on univariable analysis or because they were considered clinically relevant. The proportional hazards assumption was assessed by Kolmogorov-type Supremum test. Only patients with data present for all co-variables were included. A p value < 0.05 was considered statistically significant. To evaluate if death before TLR occurrence confounded the result for this end point, a competing outcome analysis was carried out over the entire cohort. To analyze whether the presence of DM would favor the performance of one type of DES over the other, a subgroup analysis was performed by restricting the population to those with a history of DM.

The authors of this manuscript have certified that they comply with the Principles of Ethical Publishing in the International Journal of Cardiology .

3

Results

A total of 218 patients on chronic HD underwent PCI with a DES. Sixty-two patients were treated with a PES, while 156 patients received a LES (SES n = 112, EES n = 44). There were no exclusions. The average age for the entire cohort was 67 years (± 11) and the population was predominantly male (57%). Sixty percent of patients were African American.

Table 1 outlines the baseline characteristics for both the entire cohort and the DM subgroup. There were no significant baseline clinical differences between the patients treated with either type of stent in the overall cohort and in the DM-restricted population. Overall, the prevalence of DM was 71%, of which 39.2% received insulin. More than 50% of the population had a history of coronary revascularization by either PCI or coronary artery bypass grafting. Approximately 40% of patients had an acute coronary syndrome at presentation for which PCI was performed; 4% were in cardiogenic shock at presentation.

Table 1

Baseline characteristics.

	Entire Cohort			Diabetes Mellitus Restricted
	LES (n = 156)	PES (n = 62)	p Value	LES (n = 115)	PES (n = 39)	p Value
Age (years)	66.62 ± 10.67	66.97 ± 11.63	0.83	66.27 ± 10.57	66.44 ± 11.00	0.93
Men	84 (53.8%)	40 (64.5%)	0.15	54 (47.0%)	23 (59.0%)	0.20
African–American	97 (62.2%)	33(53.2%)	0.22	74 (64.3%)	21(53.8%)	0.24
Current smoker	13 (8.3%)	9 (14.5%)	0.17	8 (7.0%)	4 (10.3%)	0.50
Unstable angina at presentation	51 (32.9%)	19 (30.6%)	0.75	36 (31.6%)	15 (38.5%)	0.43
Myocardial infarction at presentation	16 (10.3%)	6 (9.7%)	0.89	12 (10.5%)	4 (10.3%)	1.00
Cardiogenic shock at presentation	7 (4.6%)	2 (3.3%)	1.00	6 (5.2%)	2 (5.3%)	1.00
History of diabetes mellitus	115 (74.2%)	39 (62.9%)	0.10	115 (100.0%)	39 (100.0%)
Insulin-treated diabetes mellitus	65 (41.9%)	20 (32.3%)	0.19	65 (56.5%)	20 (51.3%)	0.57
History of hypertension	154 (98.7%)	61 (98.4%)	1.00	113 (98.3%)	39 (100.0%)	1.00
History of dyslipidemia	143 (92.3%)	52 (83.9%)	0.06	108 (93.9%)	35 (89.7%)	0.47
History of myocardial infarction	47 (32.4%)	22 (40.0%)	0.31	32 (29.9%)	14 (42.4%)	0.18
Previous percutaneous coronary intervention	46 (31.5%)	20 (37.0%)	0.46	34 (31.2%)	12 (38.7%)	0.43
Previous coronary artery bypass surgery	46 (31.5%)	15 (24.2%)	0.43	27 (23.5%)	11 (28.2%)	0.55
History of congestive heart failure	68 (45.9%)	31 (51.7%)	0.45	49 (45.4%)	20 (52.6%)	0.44
Left ventricular ejection fraction	0.42 ± 0.15	0.42 ± 0.15	0.98	0.44 ± 0.15	0.43 ± 0.15	0.90
Angiotensin-converting enzyme inhibitor	66 (44.6%)	34 (54.8%)	0.18	49 (45.0%)	22 (56.4%)	0.22
Beta blocker	125 (83.9%)	51 (83.6%)	0.96	89 (81.7%)	33 (84.6%)	0.81
Statin	118 (81.9%)	45 (73.8%)	0.19	89 (82.4%)	26 (68.4%)	0.07

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