Methods

From April 2003 to December 2005, we prospectively recruited patients who underwent percutaneous coronary intervention (PCI) for the de novo left anterior descending coronary artery or left circumflex coronary artery lesions. Exclusion criteria were defined as follows: (1) calcifications limiting quantitative assessment of vessel cross-sectional area (CSA); (2) LMCA lesions with severe stenosis, defined as >50% diameter stenosis assessed by quantitative coronary angiography; and (3) having undergone PCI for LMCA. In total, 232 LMCA lesions in 232 consecutive patients were enrolled in this study. Of these patients, 14 were excluded because of an inability to perform IVUS (2 patients) and to evaluate IVUS images (12 patients). Ultimately, 218 LMCA lesions in 218 consecutive patients were evaluated. We analyzed the smallest luminal area within their LMCA lesions using IVUS. All patients provided written informed consent, and the study was approved by the hospital ethics committee.

At baseline, all patients underwent an interview by trained interviewers and laboratory tests. Standardized questionnaires assessed coronary risk factors, symptoms, history, and medications. Self-reports of myocardial infarction, angina pectoris, and congestive heart failure were confirmed and validated by review of medical records and relevant examinations. We defined major adverse cardiac events (MACEs) as all deaths including cardiac death, nonfatal myocardial infarction, any revascularization including PCI and coronary artery bypass grafting for new and/or restenosis lesions, and unplanned hospital admission for congestive heart failure. Hospitalization for congestive heart failure was defined as admission to the hospital or attendance at an acute health care facility for the administration of intravenous diuretic treatment, escalation of diuretic doses, and/or inotropes with or without confirmation of the diagnosis on chest x-ray. Revascularizations for the significant stenosis lesions at baseline were excluded from MACEs. The narrowed coronary artery was defined as the one with ≥50% stenosis in a vessel ≥1.5 mm angiographically. Follow-up data were obtained from hospital charts and telephone interviews with patients.

Coronary angiograms were obtained in multiple views after intracoronary injections of isosorbide dinitrate 2.5 mg. Quantitative coronary angiography analysis was performed with a validated edge detection system (MEDIS Medical Imaging Systems, Leiden, The Netherlands) by an experienced observer who was blinded to the clinical course. The reference vessel diameter, minimal luminal diameter, and percentage diameter stenosis were measured from the single worst view.

Global left ventricular function was determined from end-diastolic and end-systolic left ventricular endocardial contours using the centerline method and the global ejection fraction was determined as (end-diastolic volume − end-systolic volume)/end-diastolic volume × 100. The left ventricular ejection fraction was measured before PCI. The measurements were made by an experienced observer who was not aware of the clinical course.

IVUS studies were performed with commercially available systems: a mechanical sector scanner and a 40-MHz transducer (Boston Scientific Corporation, Natick, Massachusetts). Slow, continuous pullback of the IVUS transducer was started in 1 of the left coronary arteries and was generally achieved using a motorized pullback device (at 0.5 mm/s). IVUS images during the entire pullback were recorded on 0.5-inch high-resolution S-VHS tapes or DVDs. The LMCA target site was the smallest luminal CSA within the LMCA plaque. If there were several slices with equal luminal areas, the slice with the largest external elastic membrane and plaque-plus-media (external elastic membrane minus lumen) CSA was analyzed. Quantitative analysis was performed according to criteria of the American College of Cardiology clinical expert consensus document on IVUS as follows. The luminal CSA was measured by tracing the leading edge of the intima and the external elastic membrane CSA with reference to the leading edge of the adventitia. Plaque burden (as a percentage) was calculated as (plaque-plus-media CSA)/(external elastic membrane CSA) × 100%. LMCA lesions whose sizes were larger than the IVUS region of interest or whose lengths were too short to measure were excluded. Representative cases are illustrated in Figure 1 . All measurements were performed by 2 independent experienced observers who were blinded to the clinical course. The correlation of plaque burden measured by 2 physicians who conducted IVUS was r ² = 0.85 (p <0.001). There were no complications related to IVUS studies.

(A) A representative case in an 85-year-old woman admitted to our hospital in July 2005 because of effort angina pectoris due to 90% stenosis in the proximal left anterior descending coronary artery (a) . Plaque burden was 20.1%. She belonged to tertile 1 (b) . (B) A representative case in a 49-year-old man admitted to our hospital in August 2003 because of effort angina pectoris due to 99% stenosis in the proximal left anterior descending coronary artery (a) . Plaque burden was 50.7%. He belonged to tertile 3 (b) . EEM = external elastic membrane.

We analyzed data by grouping into tertiles according to plaque burden values. Baseline characteristics and IVUS findings are reported as mean ± SD and as percentages, with p values calculated using 1-way analysis of variance or the chi-square test. Kaplan-Meier analysis, the log-rank test, and the Cox proportional-hazards model were used for assessment of the tertiles and plaque burden in the LMCA (per percentage). Concerning multivariate analysis, the following variables were included: those with p values <0.20 on univariate analysis, age, gender, and clinical syndrome of acute myocardial infarction or unstable angina pectoris. Analyses were performed using StatMate3 for Windows (ATMS Corporation, Tokyo, Japan). Statistical significance was set a priori at p <0.05.

Results

The average duration of follow-up was 16.1 ± 10.5 months. In this study population (n = 218), the average age was 67.1 ± 9.7 years. The population comprised 77% men. Rates for histories of hypertension, hyperlipidemia, diabetes mellitus, current smoking, previous myocardial infarction, and previous PCI or coronary artery bypass grafting were 67%, 64%, 31%, 37%, 25%, and 34% respectively. The clinical presentation was stable angina pectoris in 73%, unstable angina pectoris in 16%, and acute myocardial infarction in 11%. In IVUS findings of all patients, the average values for external elastic membrane CSA, luminal CSA, plaque-plus-media CSA, and plaque burden were 25 ± 6 mm ² , 15 ± 5 mm ² , 10 ± 4 mm ² , and 39 ± 13%, respectively. The ranges of plaque burden for each tertile were as follows: tertile 1, <32% area stenosis; tertile 2, 32% to 45% area stenosis; and tertile 3, >45% area stenosis. The baseline characteristics, angiographic findings, and IVUS findings of each tertile are listed in Tables 1 to 3 . There were no differences in age, history of hypertension, hyperlipidemia, current smoking, myocardial infarction, PCI or coronary artery bypass grafting, number of narrowed coronary arteries, clinical syndrome, the left ventricular ejection fraction, and medication use among the tertiles. However, according to plaque burden in the LMCA, there was a significant difference in gender. Moreover, the proportion of patients with diabetes mellitus and histories of smoking tended to increase across the tertiles. With regard to the number of narrowed coronary arteries, there were no differences among the tertiles, but there tended to be more 2-vessel disease patients in tertile 3 than in those in tertile 1 (p = 0.063). Concerning reference vessel diameter, minimal luminal diameter, and percentage diameter stenosis, there were significant differences among the tertiles statistically.

Over the 3-year observation period, 12% of tertile 1, 18% of tertile 2, and 40% of tertile 3 experienced MACEs ( Table 4 ). No patients experienced MACEs because of atherosclerotic plaque progression to the LMCA. On Kaplan-Meier analysis, the proportion of MACE-free survivors was significantly lower in tertile 3 compared to tertiles 1 and 2 (log-rank p <0.001; Figure 2 ), because of revascularization (log-rank p <0.001; Figure 2 ). In particular, it was due to new lesions. However, the proportions of all death were similar across tertiles ( Figure 2 ). Results of univariate Cox hazard analysis for MACEs and revascularization are summarized in Tables 5 and 6 . The hazard ratios of plaque burden for MACE and revascularization were 1.04 (95% confidence interval [CI] 1.02 to 1.06, p <0.001) and 1.05 (95% CI 1.02 to 1.07, p <0.001), respectively. Reference vessel diameter, minimal luminal diameter, and percentage diameter stenosis by angiographic evaluation were not significantly associated with MACEs. After adjustment for gender, age, clinical syndrome of acute myocardial infarction or unstable angina pectoris, number of narrowed coronary arteries, and variables with p values <0.20 on univariate analysis, plaque burden in the LMCA remained an independent significant predictor of MACEs (hazard ratio 1.04, 95% CI 1.02 to 1.07, p <0.001) and future revascularization (hazard ratio 1.05, 95% CI 1.02 to 1.07, p <0.001) on multivariate Cox proportional hazard analysis ( Tables 5 and 6 ). The adjusted hazard ratios of other parameters (male gender, age, clinical syndrome of acute myocardial infarction or unstable angina pectoris, number of narrowed coronary arteries, and variables with p values <0.20 on univariate analysis) are listed in Tables 5 and 6 .

Table 4

Major adverse cardiac events

Variable	Tertile 1	Tertile 2	Tertile 3	p Value
	(n = 73)	(n = 73)	(n = 72)
All MACEs	9 (12%)	13 (18%)	29 (40%)	<0.001
All deaths	1 (1%)	2 (3%)	2 (3%)	0.81
Cardiovascular death	1 (1%)	1 (1%)	1 (1%)	>0.99
Nonfatal myocardial infarction	0 (0%)	0 (0%)	0 (0%)	1
Revascularization	7 (10%)	12 (14%)	26 (36%)	<0.001
New lesions	3 (4%)	6 (8%)	19 (26%)	<0.001
Restenosis lesions	4 (6%)	4 (6%)	7 (10%)	0.62
Unplanned hospitalization for congestive heart failure	1 (1%)	1 (1%)	1 (1%)	0.60

Only gold members can continue reading. Log In or Register to continue

Share this:

• Click to share on Twitter (Opens in new window)
• Click to share on Facebook (Opens in new window)

Related

Related posts:

1. Association of Frontal QRS-T Angle–Age Risk Score on Admission Electrocardiogram With Mortality in Patients Admitted With an Acute Coronary Syndrome
2. Vitamin D Deficiency and Supplementation and Relation to Cardiovascular Health
3. Sudden Death Associated With Danon Disease in Women
4. Comparison of Patients With Pulmonary Arterial Hypertension With Versus Without Right-Sided Mechanical Alternans

Stay updated, free articles. Join our Telegram channel

Join