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Original article

Long-term outcome of patients of over 85 years old with acute coronary syndrome undergoing percutaneous coronary stenting: a comparison of bare metal stent and drug eluting stent

MA, Han-ying; ZHOU, Yu-jie; Dick, Ronald J; SHI, Dong-mei; LIU, Yu-yang; CHENG, Wan-jun; GUO, Yong-he; WANG, Jian-long; GE, Hai-long

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Abstract

The elderly population has been steadily increasing in the previous decade, especially octogenarians. As the prevalence of coronary heart disease (CHD) increases with age, the rapid growth of the elderly population will lead to an increase in the number of the elderly being referred and considered for percutaneous coronary revascularization. Most randomized trials, showing a benefit from coronary revascularization, have always selected patients who are under the age of 75. Evidence-based data guiding coronary revascularization in the elderly especially in the very elderly have been limited to randomized clinical trials.1–4

The very elderly are a heterogenous population with complex co-morbidities conditions, worse left ventricular (LV) function, poor functional status, increased risk and reduced benefit, complicated technical issues needed, lesions such as multi-vessel, diffuse, calcified diseases. Also, the strategy of stent selection remains unclear.5–8 The purpose of this study was to evaluate the long-term outcomes of patients aged over 85 years with acute coronary syndrome (ACS) undergoing percutaneous coronary stenting and to observe whether there are differences between bare metal stent (BMS) and drug eluting stent (DES).

METHODS

Study population

A hospital database search revealed all ACS patients over the age of 85 years, who had undergone percutaneous coronary intervention (PCI) at our center from November 2004 to November 2006. All charts were reviewed for demographic and procedural data. The patients were divided into DES group (n=59) and BMS group (n=21).

Procedures and relevant medications

All patients were pretreated with aspirin 300 mg and clopidogrel 300–600 mg. During the procedure, anticoagulation followed standard protocol-unfractionated heparin 80–100 U/kg, if patients were treated with GPIIbIIIa, unfractionated heparin reduced to 70–80 U/kg. Coronary angiography and stenting were performed according to the standard techniques. Post-intervention medication consisted of aspirin 100 mg/d life-long and clopidogrel 75 mg/d for 1–3 months in the BMS group and aspirin 100 mg/d life-long and clopidogrel 75 mg/d for 6–12 months in the DES group.

Clinical definition

ACS included unstable angina (UA), non-ST elevation myocardial infarction (NSTEMI) and ST elevation myocardial infarction (STEMI). Successful PCI was defined as a final stenosis ≤20% of the vessel diameter with TIMI 3 grade flow. Cardiac death was defined as mortality not due to non-cardiac disease. Target lesion revascularization (TLR) was defined as a repeat revascularization with a stenosis ≥50% in the treated lesions. Target vessel revascularization (TVR) was defined as repeat revascularization within the treated vessels. Major adverse cardiac events (MACEs) were defined as a composite of cardiac death, myocardial infarction, TLR and TVR. Other major bleeding referred to severe bleeding except intracranial bleeding. TIMI score was used to stratify the risk of death in ACS patients. The score was calculated as the sum of predefined numerical values including age older than 65 years, more than three coronary risk factors, prior coronary stenosis more than 50%, aspirin administration within 7 days, ST change, more than two episodes of angina within 24 hours and cardiac biochemical marker elevated. A total score value was 7.9–11

Follow-up

Clinical follow-up was done by telephone, review of medical records or outpatient interview to establish the incidence of MACE, stroke and major bleeding. All surviving patients were also contacted by telephone to confirm. Up to November 2007, all patients were clinically followed up for at least one year, with a maximum to three years (range: 360–1080 days).

Statistical analysis

Continuous variables were presented as mean ± standard deviation (SD) or median with interquartile ranges. They were compared using independent sample t test or the Mann-Whitney U test. Categorical variables were presented as frequencies (%) and compared with the chi-square test or Fisher's exact test. Clinical and procedural variables including age, sex, white blood cell count, platelet and hemoglobin; creatinine level, uric acid, tropnin I, CK-MB and glomerular filtration; the factors of hypercholesterolemia, hypertension, current smoker, diabetes, prior MI, prior PCI, prior coronary artery bypass grafting (CABG) and family history; clopidogrel dosage, clinical presentation, number of vessel treated, lesion length, lesion type, TIMI flow pre- PCI and post- PCI, ST elevation and/or depression during the procedure were evaluated by univariate and stepwise Logistic regression analyses. Only variables with a P value < 0.05 in the univariate analysis (creatinine level, hypertension and clinical presentation) were taken into the multivariate model to test independent effects. The results were presented as adjusted odds ratio (OR) with 95% confidence interval (CI). All tests were 2-tailed and P value <0.05 was considered statistically significant. Statistical analysis was performed with SPSS 11.5.

RESULTS

Baseline clinical characteristics

In the 80 patients, 21(26.3%) used BMS and 59(73.7%) used DES. Among them, 16 patients were over 90 years old. Forty-three patients were males and 37 were females, and their mean age was (87.5±1.5) years (85–94 years). Fifteen patients had STEMI and 65 patients had non-STEMI including unstable angina (43 patients) and NSTEMI (22). Baseline clinical characteristics were similar between the two groups despite more patients in the DES group who underwent previous coronary intervention (35.6% vs 14.3%, P=0.25) and had a positive family history (35.6% vs 19.1%, P=0.31). Also there were more patients in the BMS group who were of Killip III—IV grade during the procedure (19.9% vs 1.7%, P=0.06) (Table 1).

Table 1
Table 1:
Baseline clinical characteristics

Baseline angiographic and procedural characteristics

Of the 80 patients, 36 (47.5%) had 3-vessel diseases, 18 (22.5%) had 2-vessel diseases, and 26 (30.0%) had 1 vessel disease. The success rate of the procedure was 93.8% with TIMI-3 coronary flow post-PCI in 93.8% of the vessels while TIMI-3 coronary flow pre-PCI only in 75.0% of the vessels. Procedure-related complications occurred in 17.5% of the patients, with a dissection rate of 12.5%. In the DES group, the frequency of bifurcation lesion (11.9% vs 0%, P=0.11) and graft PCI (10.2% vs 4.8%, P=0.31) was more than that in the BMS group. Other angiographic and procedural details were similar between the two groups (Table 2).

Table 2
Table 2:
Baseline angiographic and procedural characteristics

Clinical outcomes

In-hospital MACE was 8.8% in the entire cohort. No stroke and only two other major bleeding occurred in the DES group. The 1-year follow-up rate of MACE in the DES group was 7.0% but no MACE was found in the BMS group. Only one stroke and one other major bleeding occurred in the DES group. Clinical follow-up for 12–36 months revealed that the incidence of MACE in the BMS group was 5.3% whereas it was 21.1% in the DES group. Totally, the long-term survival free from MACE was 82.9% (Table 3).

Table 3
Table 3:
In-hospital, 1-year and overall follow-up (12–36 months) results (n (%))

Only creatinine level, hypertension and clinical presentation, which were shown to have a P value < 0.05 in the univariate analysis, entered the multivariate model to test independent effects. COX regression analysis of multiple factors showed that creatinine level (OR: 1.013; 95%CI: 1.006–1.020; P=0.004) and hypertension (OR: 3.201; 95%CI: 1.000–10.663; P=0.04) were 2 major factors affecting MACE.

DISCUSSION

This study involved 80 patients with ACS, a very high-risk population. Their median age was 87.5 years; the number of males was a little more than that of females. The patients had a variety of co-morbid conditions, including history of hypertension, high level of creatinine, hypercholesterolemia, previous MI, previous coronary bypass surgery and PCI, but they were less likely to have diabetes mellitus, renal failure, and congestive heart failure, or to be smokers. Also, the patients with diffuse multivessel coronary disease were more likely to be enrolled in the study. Similar to other studies,12–14 most patients presented with unstable angina at the time of enrollment (53.8%). We measured one of the strong independent predictors of outcomes in patients with ACS-TIMI risk scores in these high risk patients. The median TIMI risk score in this study was 4.5, indicating at least a 20% risk of death, myocardial infarction or urgent coronary revascularization within 2 weeks.9

GRACE study showed that compared with the other three younger groups, the patients of more than 85 years old had a significantly lower rate of angiography and PCI. With the increasing of age in the elderly, the success rate of revascularization was lower. But in our study with a small sample, the success rate of the procedure was high (93.8%) with a good result of TIMI flow post-PCI. At the same time, the procedure-related complications occurred in 17.5% of the patients with a dissection rate of 12.5%. This was possibly due to complex coronary lesion (Type B2+C: 80%) and severe calcification.

Other studies15,16 of GRACE showed that patients of over 85 years old had a significantly higher occurrence rate of in-hospital death, heart failure, shock and major bleeding compared with the other three younger groups.

The incidence of in-hospital MACE was much higher in elderly patients treated conservatively than in the PCI treated.17,18 In our study, the incidence of in-hospital MACE was 8.8% including 4 cardiac deaths and 3 MI deaths. The four deaths were due to STEMI, accompanied with Temp pacing (1 patient), IABP (2), hypertension and Killip III—IV grade (3), and complication and GP IIbIIIa use (4), which indicated that they were very high risk patients.

Long-term outcomes of the procedure in this group of patients may affect the future practice. Compared with PCI, conservative treatment may increase the rates of TVR and re-hospitalization.19

In our study, the one year follow-up rate of MACE was low in the DES group and the BMS group. But the follow-up of 12–36 months showed the incidence of MACE was higher in the DES group than in the BMS group. MACE was resulted from cardiac deaths and MI, with a low incidence of TLR and TVR. In 6 deaths and 4 MI patients, 60 % occurred after one year. It was partly due to the duration of dual anti-platelet therapy. Obviously the duration and monitoring of dual antiplatelet in patients with ACS of over 85 years old undergoing DES need further confirmation.

COX regression analysis of multiple factors showed that creatinine level (OR: 1.013; 95%CI: 1.006–1.020; P=0.004) and hypertension (OR: 3.201; 95%CI: 1.000–10.663; P=0.04) are two major factors affecting MACE. Other studies20–22 showed that the prominent predictor of long-term MACE is renal function. Hence if such procedure is done, renal function and hypertension, which may contribute to long-term MACE, should be considered.

Limitations should be taken into consideration when the results of this study are interpreted. For instance, the number of patients is too small to find the best strategy of stent selection and may affect the results of COX regression analysis of multiple factors. Stent selection is largely based on the operators’ preference and non-randomization.

Moreover, percutaneous coronary stenting in patients over 85 years old is associated with a high success rate of the procedure and a low in-hospital mortality and low MACE as shown by long-term follow up. Since there are differences between DES patients and BMS patients, stent selection for this population needs further studies.

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Keywords:

aged; long-term outcome; acute coronary syndrome; stent

© 2008 Chinese Medical Association