Etsuo Mori

Intra-coronary administration of l-arginine aggravates myocardial stunning through production of peroxynitrite in dogs

OBJECTIVE The aim of this study was to investigate how the enhanced nitric oxide (NO) production by intra-coronary infusion of L-arginine acts in myocardial stunning in dogs by focusing on the involvement of peroxynitrite, a reaction product of NO and superoxide anion. METHODS AND RESULTS Dogs were divided into six groups; a control non-treated group (CON, n = 9), and NG-nitro L-arginine methyl ester (L-NAME, n = 6), 1 mM L-arginine (L-ARG, n = 8), D-arginine (D-ARG, n = 6), L-arginine plus superoxide dismutase (L-ARG + SOD, n = 6), and SOD alone (SOD, n = 6) treated groups. L-NAME, or L- or D-arginine was continuously infused into the left anterior descending coronary artery (LAD) starting just prior to reperfusion, whereas SOD was intravenously injected before occlusion. During 120 min of reperfusion after 15 min occlusion of LAD, myocardial contractile function in the ischemic region gradually recovered and reached approximately 70% of the preischemic level in CON, D-ARG and SOD, but it remained dyskinetic (-46%) in L-ARG. On the other hand, it was improved in L-NAME (90%). Tissue malondialdehyde was elevated (p < 0.005) after reperfusion, and myocardial NO metabolites measured by an intratissue-microdialyzer increased (approximately 150%, p < 0.05) in the ischemic region during reperfusion in L-ARG but not in the CON, L-NAME, D-ARG or SOD groups. In the L-ARG + SOD group, L-arginine-induced contractile dysfunction and elevation of malondialdehyde were prevented, but the increase in NO metabolites remained. These results suggest that L-arginine aggravated myocardial stunning through oxidative stress and the cytotoxicity was caused by NO derivatives but not by NO itself. The formation of nitrotyrosine, a footprint of peroxynitrite, was immunohistochemically confirmed in the ischemic region of L-ARG. CONCLUSIONS Our results demonstrate for the first time in vivo that NO has a detrimental role in myocardial stunning through the production of peroxynitrite.

Clinical impact of coronary artery spasm in patients with no significant coronary stenosis in acute coronary syndromes

BACKGROUND AND OBJECTIVE To clarify the clinical features of coronary artery spasm (CAS) with no significant coronary stenosis in patients with suspected acute coronary syndrome (ACS) in real practice. METHODS This is a retrospective observational study of patients with suspected ACS (n=645) based on symptoms, electrocardiographic changes, and/or positive cardiac biomarkers and vasospastic angina (VSA, n=90). ACS patients were divided into two groups: (1) organic ACS (n=515), culprit lesion ≥75% coronary stenosis with/without thrombosis; (2) spastic ACS (n=70), coronary stenosis <75%, either with positive acetylcholine (ACh) test (n=51) or without ACh test but verified spontaneous spasm (n=19). The study compared clinical characteristics among organic ACS, spastic ACS, and VSA. RESULTS One hundred and thirty suspected ACS patients had a coronary organic stenosis <75% (130/645, 20%). Seventy of those patients (70/130, 54%) were confirmed to have CAS, and these accounted for 11% of all ACS patients (70/645). The rate of cigarette smoking was highest in the spastic ACS. No spastic ACS patients died during their hospital stay or after discharge, whereas acute myocardial infarction occurred in 19%, aborted sudden cardiac death in 6%, multivessel spasm was provoked in 78%, and diffuse spasm was more frequently provoked than in the VSA group (82% vs. 62%). CONCLUSIONS CAS is not a rare cause of ACS. Although the prognosis of spastic ACS is good, there are occasional critical cases. An initial differential diagnosis including an ACh test is thus important to decide the treatment strategy of ACS.

Gender differences in factors influencing electrocardiographic findings of left ventricular hypertrophy in severe aortic stenosis

We investigated gender differences in factors influencing the electrocardiographic (ECG) findings of left ventricular hypertrophy (LVH) in patients with severe aortic stenosis (AS). The functional and geometric responses of the left ventricle to chronic pressure overload, such as hypertension and AS, have been reported to be different between men and women. However, gender differences in the factors influencing the ECG findings of LVH in pressure overload remain unknown. We conducted a retrospective observational study in consecutive patients with severe AS (aortic valve area (AVA) assessed by cardiac catheterization <1.0 cm2) without concomitant significant aortic regurgitation, mitral stenosis and/or regurgitation, conduction disturbance, or myocardial infarction (n = 35 males, 68 females). The ECG criteria were classified into three categories: (1) high voltage by the Sokolow–Lyon index associated with ST-T wave changes (with no digitalis therapy); (2) high voltage alone; and (3) normal. Groups 1 and 2 were defined as LVH on ECG. We compared the ECG findings in relation to the AS severity between genders. Women were older, but there were no significant differences in the prevalence of hypertension, AVA index (AVAI), mean pressure gradient or peak velocity across the AV, LV mass index (LVMI) derived from echocardiography or the distribution of ECG categories between genders. A multiple logistic regression analysis including age, gender, hypertension, AVAI, mean pressure gradient, and LVMI revealed that the LVMI (P = 0.001) and AVAI (P = 0.0434) were significantly related to the distribution of ECG categories. LVMI significantly predicted LVH on ECG in both genders, but AVAI was a predictive factor in only women. ECG LVH in patients with severe AS may be mainly reflected by LVMI in men and by both LVMI and AVAI in women. Factors other than AVA, such as end-stage disease and/or complicating factors such as hypertension, may underlie the observed differences in ECG findings of LVH between men and women.