Intravascular ultrasound-guided unprotected left main coronary artery stenting in the elderly

Study population

Between October 2009 and September 2012, in Qinhuangdao First hospital, Hebei Province, China, 123 consecutive elderly patients (age >70) with ULMCA were randomized to the IVUS group (61 patients) or the control group (62 patients). Patients in the IVUS group underwent intervention with IVUS guidance and patients in the control group underwent intervention with routine angiography guidance. Unprotected left main coronary artery was defined5 as at least 50% stenosis by visual assessment in the LM vessel without bypass grafts to the left anterior descending artery or left circumflex artery. Exclusion criteria were severe left ventricular dysfunction (ejection fraction <30%), cardiogenic shock, acute myocardial infarction, carcinoma.

This study was approved by the ethics committee of Qinhuangdao First Hospital, and a written informed consent was obtained from all patients prior to the procedure. This study was performed according to the principles of the Helsinki Declaration.

Procedure

Coronary angiography and PCI were performed in the 2 groups via a transradial or transfemoral approach. Minimal lumen diameter (MLD) and lesion length were measured with the quantitative coronary angiography (QCA) analysis system (Centricity CA1000, GE Healthcare, Waukesha, WI, USA).

In the control group, the intervention strategy was decided based on the location of the lesion. Single stent technology was used in ostium or trunk LM disease without bifurcation lesions. Lesions involving the distal segment of the LM or bifurcation were treated with T-stenting, provisional T-stenting or the kissing-balloon technique. In the IVUS group, the stenting technology was decided based on both angiographic finding and IVUS finding.

Two types of drug eluting stent (DES) were implanted as follows: 1) Sirolimus-eluting stents (Firebird-2, Microport, Shanghai, China). 2) Sirolimus-eluting stents (Excel, Jiwei, Shandong, China). Patients were loaded with 300 mg clopidogrel before procedure and remained on a 75 mg dosage daily for at least one year. Aspirin was administered 300 mg daily during the first month and 100 mg daily after the first month. Procedural success was defined as lumen stenosis <30% by final coronary angiography.

Intravascular ultrasound

Intravascular ultrasound was performed in patients of the IVUS group. After the intracoronary administration of 200 ug nitroglycerin, the IVUS catheter (Eagle Eye; Volcano Corporation, Rancho Cordova, CA, USA) was positioned at more than 10 mm beyond the lesion and was pulled back automatically (0.5 mm/s) to the opening of LM. Intravascular ultrasound images were examined by 2 experienced technicians using computerized planimetry (EchoPlaque, INDEC Systems, Inc., Mountain View, CA, USA). Minimal lumen diameter, minimal lumen area (MLA), reference lumen area, and plaque burden were measured. The cross-sectional luminal area was defined6 as the integrated area central to the intimal leading edge echo. Plaque burden6 was calculated as (EEM CSA-lumen CSA)/EEM CSA.

After the procedure, IVUS was repeated to ensure adequate stent expansion. The expansion ratio6 was calculated as minimum stent CSA / (proximal reference lumen CSA + distal reference lumen CSA) × 1/2. Successful stent expansion7 was defined as lumen area 90% or greater of the average reference lumen area pre-intervention. Patients with stent underexpansion underwent post-dilation to gain adequate stent expansion.

Follow-up

Clinical follow-up was performed at one month, 6 months, 12 months, and 24 months. Mean follow-up time was 23.26±7.24 months. Angiography follow-up was performed 9-12 months after the procedure. The primary endpoint was the 2-year incidence of MACE. It was defined as death, non-fatal myocardial infarction, and target lesion revascularization (TLR). Target lesion revascularization8 was defined as a new intervention (percutaneous or surgical) on a previously implanted stent, or within 5 mm of that stent. Deaths were classified as either cardiac or non-cardiac. Deaths that could not be classified were considered cardiac according to the Academic Research Consortium definitions.8 Myocardial infarction9 was diagnosed by an elevation of serum creatine kinase or troponin 3 times the upper limit of normal, together with chest pain lasting more than 30 minutes.

The safety endpoint was stent thrombosis. It was defined as definite or probable stent thrombosis according to established criteria.9 All data relating to procedures and in-hospital outcomes were collected. Information regarding clinical status were collected at clinic visits and by telephone interview.

Statistics analysis

All statistics analyses were performed using the Statistical Package for Social Sciences version 17 (SPSS Inc., Chicago, IL, USA). Continuous variables were expressed as mean ± standard deviation of the mean, and were compared by use of the unpaired t test; categorical variables were compared with the χ² statistics or Fisher exact test.

The incidence rates of 2 year MACE were estimated by the Kaplan-Meier method. A probability value <0.05 was considered statistically significant. A Cox proportional hazard regression analyses were performed to find the predictors of the event outcomes. Variables with a probability value <0.20 in univariable analyses were candidates for the multivariable Cox proportional hazard regression models. A backward elimination process was used to develop the final multivariable model, and adjusted hazard ratio (HR) with 95% confidence intervals (CI) was calculated. A probability value <0.05 was considered statistically significant.