Clinical Outcomes after Percutaneous Coronary Intervention with Drug-Eluting Stents in Dialysis Patients
- Volume 18 - Issue 6 - June, 2006
- Posted on: 8/1/08
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The major cause of mortality in dialysis patients is attributable to cardiovascular diseases.1,2 The higher prevalence of coronary artery disease in this population is thought to be related to a higher risk factor distribution, platelet thrombogenicity and premature coronary calcification, when compared with nondialysis subjects. Treatment of ischemic heart disease with percutaneous revascularization techniques has remained controversial because of consistent exclusion of dialysis patients from major clinical trials. To our knowledge, the literature has been composed of retrospective, single-institution experiences with only small numbers of patients, and has led to the conclusion that percutaneous coronary intervention (PCI) in dialysis patients is less successful and associated with more adverse outcomes when compared to nondialysis patients.3,4 Drug-eluting stents (DES) have recently proven an impressive tool in the reduction of repeat revascularization in the overall population and clinical indications. The aim of the present study was to evaluate the outcomes of dialysis versus nondialysis patients treated with PCI and DES.
Materials and Methods
Patient population. We analyzed the medical records of 3,442 consecutive patients who underwent PCI with DES at our institution since March 2003. All patients treated with DES only during this period were included. Patients were classified into dialysis and nondialysis groups. Dialysis patients were defined as having been treated with dialysis for greater than or equal to 90 days prior to the intervention. We identified a total of 72 dialysis patients, of whom 57 (79%) had hemodialysis and 15 (21%) had peritoneal dialysis. The diagnosis of acute myocardial infarction (MI) included all patients with ST-elevation myocardial infarction (STEMI) and non-ST-elevation myocardial infarction (NSTEMI). STEMI was determined by the presence of > 30 minutes of continuous chest pain, a new or presumed new ST-segment elevation greater than or equal to 2 mm on at least 2 contiguous ECG leads, and creatine kinase > 2 times normal. NSTEMI was diagnosed by the presence of chest pain and a positive cardiac biochemical marker of necrosis (troponin and/or creatine kinase-MB) without new ST-segment elevation. Risk factors and previous cardiovascular disease were reviewed. Diabetes mellitus was defined as hyperglycemia requiring insulin and/or oral hypoglycemic drug treatment. Hyperlipidemia was defined as receiving lipid-lowering therapy and/or the presence of a total serum cholesterol > 5 mmol/l or serum triglycerides > 2 mmol/l. Hypertension was defined as receiving medication to lower blood pressure or measured blood pressure values of greater than or equal to 140 mmHg systolic or greater than or equal to 90 mmHg diastolic on two or more occasions. Cardiogenic shock was defined as maximal systolic pressure < 90 mmHg for at least 30 minutes, unless treated with inotropes, or pump failure as manifested by a cardiac index < 2.2 liter/minute per m2 and pulmonary capillary wedge pressure > 18 mmHg. Persistence of hypotension or pump failure after correction of contributing extramyocardial factors (e.g., hypovolemia, hypoxemia or acidosis) and/or peripheral signs of hypoperfusion (e.g., peripheral vasoconstriction, urine output < 30 ml/hour or altered sensorium) were also required. Left ventricular ejection fraction (LVEF) was measured by echocardiography or angiography during the hospitalization.
Procedures. Contemporary percutaneous coronary angioplasty was performed after obtaining written, informed consent. Patients received single or multiple DES for various lesions with or without predilatation or the use of ablative devices for plaque modification. Intravascular ultrasound guided the procedure in almost 80% of the cases. After stent implantation, angiographic optimization was performed by high-pressure dilatation to achieve an acceptable angiographic result with < 30% residual stenosis. All patients received aspirin 325 mg/day greater than or equal to 24 hours before the procedure and continued indefinitely. Additional antiplatelet therapy with either clopidogrel, 75 mg/day (after a loading dose of 300–600 mg), or ticlopidine 250 mg twice daily, was instituted in all patients and advised to continue for greater than or equal to 6 months. Intraprocedural anticoagulation was ensured using unfractionated heparin or bivalirudin, with or without glycoprotein IIb/IIIa inhibitors, to achieve an activated clotting time of > 250 seconds in all patients.
Endpoint definitions. Endpoints were death and all clinical events in-hospital at 1- and 6-month follow up. Death was defined as all causes of mortality. Q-wave and non-Q-wave MI were defined as a total creatinine kinase elevation greater than or equal to 2 times normal and/or creatinine kinase-MB greater than or equal to 20 ng/ml ± new pathological Q-waves in greater than or equal to 2 contiguous leads. Neurologic events included stroke or transient ischemic attack. Acute renal failure was defined as an increase of greater than or equal to 25% over baseline creatinine levels with or without dialysis. Target lesion revascularization (TLR) and target vessel revascularization (TVR) were characterized by repeated percutaneous or surgical intervention of the treated lesion or vessel, respectively, and were clinically driven. Major adverse cardiac events (MACE) were defined as a composite of death, Q-wave MI, or repeat revascularization. Subacute stent thrombosis was defined as evidence of angiographic thrombus of the target lesion greater than or equal to 30 days from the implantation of the DES.
Clinical follow up. A dedicated data coordinating center (Data Center, MedStar Research Institute, Washington, D.C.) performed the data management and analyses. Prespecified clinical and laboratory data during hospitalization periods were obtained from hospital charts that were reviewed by
independent research personnel blinded to the objectives of the study. The data were entered prospectively into the database. Clinical follow ups at 1 and 6 months were conducted by telephone contact or office visits. The occurrence of major late clinical events was recorded, including death (all-cause), MI, TLR and TVR. All clinical events were adjudicated by source documentation by independent physicians who were not involved in the procedures.
Statistical analysis. Statistical analysis was performed using the Statistical Analysis System, version 8.2 (SAS Institute, Inc., Cary, North Carolina). Data are expressed as mean ± SD for continuous variables and as percentages for categorical variables. The Student’s t-test was used to compare continuous variables and the Chi-square test or Fischer’s exact test was used to compare categorical variables. A p-value < 0.05 was considered to indicate statistical significance. Event-free survival curves were constructed using Kaplan-Meier curves. We conducted multivariate logistic regression analysis to identify independent predictors of mortality in dialysis versus nondialysis patients at 6 months. The following variables were first assessed in a univariate model: age, gender, risk factors, clinical presentation, ejection fraction, angiography findings and in-hospital clinical events. Variables with a p-value < 0.1 were then entered into a multivariate model.
Clinical findings. Patients’ baseline clinical characteristics are summarized in Table 1. There was a higher prevalence of female gender (p = 0.03), African Americans (p < 0.001), hypertension (p < 0.001), and diabetes mellitus (p < 0.001) in the dialysis group, while patients in the nondialysis group were more likely to be obese (p = 0.02) and have a smoking history (p < 0.001). Furthermore, dialysis patients were more likely to have acute MI (p = 0.04) at the time of presentation, cardiogenic shock (p = 0.01), and heart failure (p < 0.001). Low-density lipoprotein cholesterol (p < 0.001), hematocrit levels (p < 0.001), and left ventricular ejection fraction (p < 0.001) were higher in the nondialysis group. Discharge medications were mostly comparable between the two groups except for less statin (p < 0.001) use in the dialysis group. Finally, length of stay (p < 0.001) was shorter for nondialysis patients.
Angiographic characteristics. The angiographic and procedural characteristics are shown in Table 2. Dialysis patients were more likely to have multivessel disease (p = 0.04) and more stents implanted (p = 0.02). Culprit lesion localizations were similar between the two groups. Implantation of Cypher™ (Cordis Corporation, Miami, Florida) and Taxus® (Boston Scientific Corporation, Natick, Massachusetts) stents was similar in both groups. Angiographic success, however, was achieved more often in the nondialysis group (p = 0.05).
In-hospital complications. In-hospital complications are presented in Table 3. There was a trend toward a higher mortality rate (p = 0.08) in the dialysis group. Other in-hospital complications were similar except for less transfusions (p < 0.001) in nondialysis patients.
Clinical follow up at 1 and 6 months. These clinical outcomes are presented in Table 4. Mortality rate (p < 0.001), TLR-MACE (p < 0.001) and TVR-MACE (p < 0.001) were significantly higher for dialysis patients at 1- and 6-month follow up. TVR-MACE is the composite endpoint including death, Q-wave MI and TVR. TLR-MACE is the composite endpoint including death, Q-wave MI and TLR. There was no difference in TLR and TVR between the 2 groups at 6 months, however, the dialysis patients had significantly higher TLR and TVR compared to the nondialysis patients, which was attributed to the higher rate of subacute stent thrombosis. As shown in Table 4, subacute thrombosis occurred more often in the dialysis group, as 2 patients had prematurely stopped clopidogrel treatment (3.1% vs. 0.3%; p < 0.001). We did not observe any late thrombosis in the dialysis patients at 6-month follow up, and there was no difference in late thrombosis rates between the 2 groups. In addition, Q-wave MI was higher in the dialysis group at both 1 and 6 months.
Independent predictors of mortality at six-month follow up in dialysis patients. Independent predictors of mortality at 6 months in univariate analysis included cardiogenic shock (p < 0.001), creatine kinase-MB maximum 3 times normal (p = 0.007), body mass index (p = 0.07), and African American race (p = 0.07). The only variable associated with higher odds of mortality in a subsequent multivariate analysis (Table 5) was cardiogenic shock during hospitalization (p = 0.04).