Directional coronary atherectomy for the treatment of acute myocardial infarction

Differences in intravascular ultrasound and histological findings in culprit coronary plaques between ST-segment elevation myocardial infarction and stable angina

A comprehensive evaluation of culprit coronary lesions may help to understand vulnerable plaques responsible for ST-segment elevation myocardial infarction (STEMI). We compared intravascular ultrasound (IVUS) and histological findings in culprit coronary plaques from 94 patients with STEMI (n = 54) or stable angina (n = 40). Tissue specimens were obtained by directional coronary atherectomy and IVUS was performed before percutaneous coronary intervention. IVUS and histological data were analyzed. Clinical characteristics were largely similar between the two groups. Plaque rupture and thrombi were more frequently found in the STEMI group than in the stable angina group. There were no significant differences between plaque types or proximal and distal reference measurements in the two groups. However, the site of minimal lumen area had a greater vessel area, remodeling index, and plaque burden with lesser lumen area in the STEMI group than in the stable angina group. Plaque areas immunopositive for CD68 and CD31 were significantly larger in the STEMI group, while the area immunopositive for α-smooth muscle actin was larger in the stable angina group. In conclusion, culprit lesions in STEMI patients showed a greater plaque burden, remodeling index, and more frequent thrombi with increased inflammation and neovascularization compared to the stable angina group, supporting the current concept of vulnerable plaques being responsible for STEMI.

Comparison of intravascular ultrasound and histological findings in culprit coronary plaques between ST-segment elevation and non-ST-segment elevation myocardial infarction

It remains uncertain whether the histology of culprit coronary plaques differs between ST-segment elevation myocardial infarction (STEMI) and non-STEMI (NSTEMI). We compared intravascular ultrasound (IVUS) and histologic findings in coronary culprit plaques among patients presenting with STEMI and NSTEMI. Atherectomy specimens were obtained from 96 patients, 70 with STEMI and 26 with NSTEMI, who underwent directional coronary atherectomy for de novo coronary artery lesions. IVUS examinations were performed before directional coronary atherectomy. IVUS and histologic data were analyzed. Clinical characteristics were largely similar between the 2 groups; however, normal antegrade flow before angioplasty was less frequently observed in patients with STEMI than those with NSTEMI. Plaque rupture was more common on the proximal side of the minimal lumen site. There were no differences in vessel area, lumen area, calcification, plaque burden, or remodelling index at the reference and culprit sites. However, the arc of the ruptured cavity was significantly greater in patients with STEMI than those with NSTEMI (69.4 ± 27.9° vs 51.8 ± 20.0°, respectively, p = 0.008). The proportion of atheroma, fibrocellular, and thrombus areas was not different between the 2 groups. Similarly, the relative areas immunopositive for CD31, smooth muscle α-actin, and CD68 were similar in the 2 groups. In conclusion, coronary culprit lesions in patients with STEMI show more severe plaque rupture with similar histologic features than those in patients with NSTEMI, supporting the idea that a large plaque rupture is more likely in STEMI patients.

Macrophage heterogeneity of culprit coronary plaques in patients with acute myocardial infarction or stable angina

We investigated the polarization states of macrophages in coronary atherectomy tissues retrieved from patients with acute myocardial infarction (AMI, n = 52) or stable angina pectoris (SAP, n = 22). The specimens were analyzed immunohistochemically using antibodies specific to CD11c (M1 marker), CD206 (M2 marker), and to markers of endothelial cells, macrophages, and smooth muscle cells. Baseline characteristics were similar in the 2 groups. The proportion of areas immunopositive for α smooth muscle actin was similar, but those positive for CD31 and CD68 were larger in the AMI group compared with the SAP group. In addition, AMI had significantly greater areas immunopositive for CD11c (P = .007) than did SAP, but CD206 (P = .102) positivity was not different in the 2 groups. In conclusion, M1 macrophage infiltration, not M2 macrophage infiltration, was increased in culprit plaques of patients with AMI. Macrophage heterogeneity may therefore be related to plaque instability.

Innate immunity markers in culprit plaques of acute myocardial infarction or stable angina

We analyzed the innate immunity markers, C-reactive protein (CRP), serum amyloid P component (SAP) and pentraxin-3 (PTX-3), and metalloproteinase-9 (MMP-9) in coronary atherectomy tissues obtained from patients with acute ST elevation myocardial infarction (STEMI) (n=27) or stable angina (n=15). The relative areas immunopositive for CRP and SAP were similar in the two groups. In contrast, the proportion of areas immunopositive for PTX-3 and MMP-9 was higher in the STEMI group, compared to the stable angina group. PTX-3 or MMP-9-stained areas largely overlapped with those positive for CD68. We concluded that PTX-3 plays a role in the pathogenesis of STEMI.

Comparison of differential expression of P2Y₁₂ receptor in culprit coronary plaques in patients with acute myocardial infarction versus stable angina pectoris

P2Y₁₂ receptor antagonists may have pleiotropic benefits. Little is known, however, about the expression of P2Y₁₂ receptors in coronary atherosclerotic plaques. We investigated the expression of P2Y₁₂ receptor in coronary atherectomy tissues retrieved from patients with acute myocardial infarction (AMI) or stable angina pectoris (SAP). Tissue specimens were collected from 35 patients with AMI and 19 with SAP who underwent directional coronary atherectomy. Specimens were analyzed immunohistochemically using antibodies specific to P2Y₁₂ receptor and to markers of endothelial cells, macrophages, and smooth muscle cells. The 2 groups had similar baseline clinical characteristics. Plaque types were more likely to be cellular in the AMI group. The proportion of areas immunopositive for α-smooth muscle actin was smaller but those positive for CD31 and CD68 were larger in the AMI than in the SAP group. In addition, the relative area immunopositive for P2Y₁₂ receptor was significantly larger for AMI than SAP (1.1 ± 0.9% vs 0.5 ± 0.4%, respectively, p < 0.001). P2Y₁₂ receptor positivity coincided with areas positive for CD31 and α-smooth muscle actin. In conclusion, P2Y₁₂ receptor is present in coronary atherosclerotic plaques and is increased in culprit plaques of patients with AMI. P2Y₁₂ receptor may play a role in plaque destabilization.

Fifteen-year trend in the treatment and outcome of acute myocardial infarction in Japan

To assess the changes in treatment and outcome of acute myocardial infarction (AMI) over a 15-year period, the medical records of 1,437 patients with AMI who underwent emergency coronary angiography within 24h of the onset of chest pain at Hiroshima City Hospital from 1985 to 1999 were reviewed. The patients were divided into 3 groups in chronological order: group 1 (1985-89, n=439), group 2 (1990-94, n=453) and group 3 (1995-99, n=545). Conventional balloon angioplasty and thrombolysis were frequently performed in group 1 (56% and 29%, respectively) and group 2 (71% and 13%, respectively), whereas coronary stenting and conventional balloon angioplasty were more often performed in group 3 (57% and 23%, respectively). The achievement of TIMI grade 3 flow improved in the chronological order (62%, 80% and 85%, respectively; p<0.001). The incidence of reinfarction was lower in group 3 (4.2%) than groups 1 and 2 (8.0% and 7.5%, respectively; p=0.007), and in-hospital mortality decreased from group 1 to group 3 (11.8%, 8.2% and 5.5%, respectively; p=0.002). Stenting is now the most frequently chosen treatment for AMI and sustained TIMI grade 3 flow is obtained in most of the cases, with the result that mortality has reduced by 50% in the past decade.