Michinori Imazu

Prediction of short- and intermediate-term prognoses of patients with acute myocardial infarction using myocardial contrast echocardiography one day after recanalization

OBJECTIVES This study sought to determine whether microvascular integrity in the risk area (RA) for myocardial infarction (MI) one day after recanalization predicts the outcome in patients with first acute MI. BACKGROUND Immediately after recanalization, microcirculation in the RA is modified by both hyperemic response and microvascular impairment. METHODS Fifty consecutive patients who underwent serial myocardial contrast echocardiography before and one day after recanalization (day 2) were studied. All patients had a completely occluded lesion in the left anterior descending coronary artery alone, and underwent successful reperfusion therapy. The relative size of the initial RA (RA ratio) and peak gray scale ratio (PGSR) within the RA on day 2 were determined. Patients were followed for a median of 22 months to evaluate clinical outcome. RESULTS On day 2, PGSR was a median of 0.46. Study patients were subdivided into two groups, group A of 24 patients with acceptable opacification (PGSR > 0.46 on day 2) and group B of 26 patients without it. Major cardiac events (cardiac death, nonfatal MI and repeat admission for congestive heart failure) were more frequently observed in group B (28% vs. 4%, Cox hazard ratio=8.5, p=0.05, 95% confidence interval [CI] 1.03 to 69.9). The median value of the RA ratio was 0.45. Patients (n=15) with RA ratio > 0.45 on day 1 and PGSR on day 2 < or = 0.46 exhibited a 10.7-fold relative risk for major cardiac events (p=0.005, 95% CI 2.06 to 55.8) and a 3.69-fold relative risk for composite cardiac events (major cardiac events and target lesion revascularizations) after the initial intervention (p=0.004, 95% CI 1.51 to 9.04). CONCLUSIONS The assessment of both the size of the initial RA and microvascular integrity on day 2 enables precise determination of the efficacy of reperfusion therapy and prediction of the short- and intermediate-term prognoses of patients with recanalized MI.

Pulse Wave Velocity Predicts Cardiovascular Mortality

Background Arterial stiffness measurements, generally from pulse wave velocity (PWV), are widely used with little knowledge of their relationship to long-term cardiovascular mortality in general populations. Methods and Results We studied a cohort of 492 Japanese-Americans living in Hawaii (mean age: 63.7 ±8.8 years) to assess the relationship between PWV and cardiovascular disease mortality and all-cause mortality. During the 10-year follow-up, 43 patients died (14 from cardiovascular events). The cohort was divided into 2 groups by the cut-off value of PWV (9.9 m/s) represented in the receiver operating characteristic curve. The risk ratio for PWV values >9.9 m/s to all-cause mortality was 1.28 [95% confidence interval (CI): 1.14-1.42], and adjusted for other risk factors this ratio was 1.42 (95% CI: 0.96-2.11). The corresponding risk ratios for cardiovascular mortality was 4.46 (95% CI: 1.61-12.32) and 4.24 (95% CI: 1.39-12.96), respectively. Conclusions The present study demonstrated that an increased PWV value is associated with future cardiovascular disease death in Japanese-Americans living in Hawaii. (Circ J 2005; 69: 259 - 264)

Evaluation of coronary artery stenoses using electron-beam CT and multiplanar reformation.

PURPOSE We assessed the diagnostic value of electron-beam CT with multiplanar reformation for coronary artery stenoses. METHOD Thirty-seven patients who underwent conventional coronary angiography were evaluated with ECG-triggered thin section electron-beam CT with intravenous contrast enhancement. Multiplanar reformation of a stack of the images was performed to visualize coronary arteries. Two observers blind to the results of conventional coronary angiography independently evaluated the reformatted images. RESULTS The sensitivity and specificity for the detection of significant lesions were 100 and 100% in the left main coronary artery, 83 and 84% in the left anterior descending artery, 67 and 96% in left circumflex artery, 63 and 79% in the right coronary artery, and 74 and 94% for total results, respectively. All false-positive results in the left anterior descending artery were caused by wall calcification, and in the right coronary artery, 83% of the false-positive results were caused by small slice gaps in noncalcified segments. CONCLUSION Electron-beam CT was feasible for the detection of coronary artery stenoses. For interpretation of reformatted images, calcification and slice gaps should be taken into consideration.

Optimal time for predicting myocardial viability after successful primary angioplasty in acute myocardial infarction : A study using myocardial contrast echocardiography

This study sought to elucidate serial changes in microvascular integrity during papaverine-induced hyperemia in the risk area for myocardial infarction. In addition, we attempted to determine the optimal time for predicting myocardial viability. Seventy-two patients who underwent serial myocardial contrast echocardiography (MCE) before and shortly after (day 1), 1 day (day 2), and 3 weeks (day 21) after recanalization were studied. In 18 of 72 patients, MCE was performed at baseline and during hyperemia using selective intracoronary infusion of papaverine. Both the peak grayscale ratio (PGSR) within the risk area, and the no- and low-reflow ratio (LR ratio) were analyzed in each stage. Left ventricular regional wall motion (RWM) was determined 6 months after recanalization. The correlation coefficient between PGSR with papaverine on day 1 and that on day 2 was 0.54 (p = 0.02); it was 0.50 (p = 0.04) between day 1 and day 21, and 0.82 (p = 0.001) between day 2 and day 21. On day 1, the correlation coefficient between the LR ratio with papaverine and RWM was 0.60 (p = 0.02), which changed to 0.72 (p = 0.003) on day 2 and 0.54 (p = 0.04) on day 21, respectively. The best time to predict viable myocardium was established on day 2 by receiver operating characteristics curves. ST-segment re-elevation, elapsed time from onset to recanalization, and antecedent angina pectoris were independent factors for PGSR on day 2 using stepwise and multiple linear regression analysis. This study suggests that the optimal time to estimate microvascular integrity for predicting myocardial viability might be 1 day after recanalization, which is neither shortly after recanalization nor during the convalescent stage.

Risk factors for restenosis after percutaneous transluminal coronary angioplasty: Role of lipoprotein (a)

To evaluate serum levels of lipoprotein (a) (Lp[a]) as a predictor of restenosis after percutaneous transluminal coronary angioplasty (PTCA), we evaluated 71 patients who underwent elective single-vessel angioplasty. Patients were divided into two groups according to the presence (n = 24 [34%]; group R) or absence (n = 47 [66%]; group N) of restenosis. Serum insulin levels were similar before and after the glucose challenge test in both groups. The median level of serum Lp(a) was 34.9 mg/dl in group R compared with 19.4 mg/dl in group N (p < 0.01). The frequency of the apo E4 allele was 4 (17%) in group R and 4 (9%) in group N (p = NS). The incidence of restenosis was significantly higher in patients with Lp(a) levels > or = 30 mg/dl than in those with Lp(a) levels < 30 mg/dl (65% vs 26%; p < 0.01). Our results indicate that a serum Lp(a) level > or = 30 mg/dl is a risk factor for restenosis.

Association of β3-adrenergic receptor gene polymorphism with insulin resistance in Japanese-American men

The Trp64Arg variant of the beta3-adrenergic receptor (beta3-AR) gene is relatively common in Japanese people. We hypothesized that this variant may be associated with obesity and insulin resistance when combined with a westernized lifestyle. To test this hypothesis, we investigated the relationships between the beta3-AR gene variant and obesity and insulin resistance in Japanese-American men, who are known to have a higher prevalence of type 2 diabetes mellitus (DM). The subjects were 152 Japanese-American men living in Hawaii, 83 with normal glucose tolerance (NGT), 40 with impaired glucose tolerance (IGT), and 29 with DM. The frequency of the Trp64Arg allele of the beta3-AR gene was 0.18, almost identical to that of the mainland Japanese. The prevalence of the Trp64Arg allele was 30.1% in NGT, 35.0% in IGT, and 41.4% in DM subjects (nonsignificant). The Trp64Arg variant of the beta3-AR gene showed no significant relationship with obesity or insulin resistance in NGT subjects. However, fasting and 2-hour insulin levels and insulin resistance as determined by homeostasis model assessment (HOMA) were significantly higher in IGT subjects with the Trp64Arg variant. Although indices of obesity were the same in IGT subjects with and without the Trp64Arg variant, differences in the body mass index (BMI) and percent body fat between NGT and IGT subjects were greater for individuals with the Trp64Arg variant. Thus, there is an association between the Trp64Arg variant of the beta3-AR gene and insulin resistance in Japanese-Americans with IGT.

Predictive value of preprocedural fibrinogen concerning coronary stenting

Elevated fibrinogen levels after coronary balloon angioplasty have been reported to be useful in predicting restenosis. Therefore, we sought to evaluate the relationship between preprocedural fibrinogen levels and the 6-12-month outcomes of patients undergoing coronary stenting. Plasma levels of fibrinogen were measured in 390 consecutive patients prior to coronary stenting. The primary end point was binary restenosis (percent diameter stenosis of >/=50%). The secondary combined end point was death due to cardiac causes, myocardial infarction related to the target vessel and target lesion revascularization. Patients were grouped into tertiles according to fibrinogen levels. Both at baseline and immediately after procedure, clinical and angiographic characteristics were almost identical in the fibrinogen tertiles. An increase in restenosis rate was observed across the tertiles (18.6, 23.9, 38.1%, P<0.001, respectively). In addition, the frequency of the secondary end point increased in the highest tertile (14.9, 21.5, 37.2%, P<0.001, respectively). Multivariate analysis revealed that high levels of fibrinogen (per 100 mg/dl, OR 1.82, P<0.001) and stent length (P=0.034) were independent predictors for restenosis. An elevated preprocedural fibrinogen level should be considered as a stronger predictor for restenosis after coronary stenting, which might be associated with coagulation and inflammation.

Influence of type 2 diabetes mellitus on cardiovascular disease mortality: findings from the Hawaii-Los Angeles-Hiroshima study.

The present study addressed whether diabetes mellitus was a strong risk factor for cardiovascular disease (CVD) death. Between 1976 and 1984, 927 (404 men) Japanese-Americans in Hawaii aged 40-79 years participated at baseline examination including a 75 g oral glucose tolerance test. Diabetes was defined as fasting serum glucose >or=140 mg/dl, 2 h postload glucose >or=180 mg/dl, or the use of drugs for diabetes. Causes of death were classified by ICD-9 codes on the reports from the Hawaii State Public Health Bureau. Until 1994, 178 individuals suffered death; 81 were attributed to CVD and 43 to coronary heart disease (CHD). The age-adjusted and coronary risk factors-adjusted relative risks for CHD and CVD mortality were significant for diabetes both in men and women. The impact of diabetes on CHD mortality was greater for women. However, no gender difference in the contribution of diabetes to fatal CVD was observed. Serum fasting glucose levels tended to be associated with CHD death and were associated with CVD death in diabetic subjects. In conclusion, diabetes is a strong independent risk factor for CVD mortality in Japanese-American men and women. Hyperglycemia is associated with CVD mortality in diabetic subjects.

Influence of angiotensinogen M253T gene polymorphism and an angiotensin converting enzyme inhibitor on restenosis after percutaneous coronary intervention.

We studied the relation between renin-angiotensin system (RAS) related gene polymorphisms, such as angiotensin converting enzyme (ACE) insertion/deletion (I/D), angiotensinogen (AGT) M253T and angiotensin II type 1 receptor (AT1R) A1166C, and the effect of quinapril, an ACE inhibitor with high tissue-binding affinity, on preventing restenosis after percutaneous coronary intervention (PCI). A total of 253 patients successfully treated for coronary artery disease were randomly assigned to quinapril or control. Of the 215 patients who completed the follow-up, we determined gene polymorphisms in 204 patients with 241 lesions who provided blood samples for genotype determination. In the control, the ACE D homozygotes showed a smaller minimal lumen diameter (MLD) at follow-up (P=0.063). The other two genotypes of AGT and AT1R did not affect restenosis after PCI. According to quinapril treatment, the AGT T homozygotes significantly showed a beneficial effect of quinapril on MLD (P=0.013) and late lumen loss (P=0.013). The ACE I homozygotes also exhibited beneficial effects of quinapril on larger MLD (P=0.065). The AT1R genotype did not influence the quinapril effect. In conclusion, the AGT T homozygotes might benefit from effects of quinapril on preventing restenosis after PCI.

Predicting Angiographic Narrowing ≥50% in Diameter in Each of the Three Major Arteries by Amounts of Calcium Detected by Electron Beam Computed Tomographic Scanning in Patients With Chest Pain

The evaluation of calcium of the coronary arteries on a vessel-by-vessel basis by use of electron beam computed tomography was useful in obstructed coronary arteries. The absence of coronary calcification in any vessel was highly specific for the absence of an obstructive lesion.