Influence of atenolol on coronary artery spasm after acute myocardial infarction in a Japanese population.

BACKGROUND: Japanese patients with acute myocardial infarction (MI) have a greater incidence of coronary artery spasm than Caucasians. Some beta-blockers have been reported to aggravate coronary spasm. This study sought to assess the effects of beta-adrenoceptor blockade on coronary vasospasm in Japanese patients with acute MI who had been treated with primary angioplasty. METHODS: In 69 patients we analyzed the effect of atenolol 50 mg/day initiated the day after emergency primary angioplasty on the results of intracoronary ergonovine provocation test performed 4 weeks after onset. RESULTS: Among 35 patients in the atenolol group, the drug was discontinued in 9 (26%) due to hemodynamic compromise. The remaining 26 in the atenolol group and 34 in the control group underwent the spasm provocation test. Atenolol did not significantly increase the incidence of coronary vasospasm (31% vs. 15% in the atenolol and control groups, respectively, p= 0.135). Multivariate analysis revealed that only the pre-provocation diameter of the distal segment of the infarct-related artery predicted coronary spasm whereas atenolol did not. CONCLUSIONS: This study showed that atenolol 50 mg/day did not increase coronary spasm in Japanese acute MI patients. It is suggested that beta-blockers can be safely used soon after coronary intervention for acute MI without the risk of increasing coronary spasm; however, attention should be paid to hemodynamic change in the acute phase.

Myocardial metabolism of 123I-BMIPP under low-dose dobutamine infusion: implications for clinical SPECT imaging of ischemic heart disease.

PURPOSE: 123I-(p-iodophenyl)-3-(R,S)-methylpentadecanoic acid (123I-BMIPP) is a fatty acid analog for single-photon emission computed tomography (SPECT) imaging that is mainly stored in the triglyceride pool. Low-dose dobutamine infusion has been reported to improve BMIPP uptake in the stunned myocardium, but the mechanism underlying this effect remains unclear. The purpose of this study was therefore to investigate the myocardial metabolism of 123I-BMIPP in the stunned myocardium under low-dose dobutamine infusion, and to elucidate the mechanism by which dobutamine improves BMIPP uptake. METHODS: Using open-chest dogs, stunned myocardium was induced by occlusion of the left anterior descending artery (LAD) for 30 min, with subsequent reperfusion (ischemia group, n=6). After direct injection of BMIPP into the LAD, myocardial extraction and retention were examined and metabolites evaluated (using high-performance liquid chromatography) during dobutamine infusion. The results in the ischemia group were compared with findings obtained in a control group under dobutamine infusion (n=6). RESULTS: Dobutamine infusion significantly increased both the rapid extraction (within 30 s) of BMIPP into the myocardium (control vs ischemia group: 48+/-19% vs 66+/-14%, p<0.05) and its subsequent retention (73+/-13% vs 85+/-8%, p<0.05). The metabolites from the myocardium consisted of back diffusion of nonmetabolized BMIPP, the alpha-oxidation metabolite, intermediate metabolites, and the full-oxidation metabolite. Among these metabolites, the full-oxidation metabolite decreased significantly (from 34.0+/-20.0% to 15.8+/-9.3%, p<0.05) in the stunned regions, though back diffusion of nonmetabolized BMIPP increased (from 51.3+/-21.9% to 71.3+/-10.1%, p<0.05). CONCLUSION: These results indicate that increased uptake of BMIPP in stunned myocardium is mainly due to decreased beta-oxidation in tissue and increased shunt retention of BMIPP in the triglyceride pool, and thereby provide further insight into the pathophysiology of stunned myocardium.

Subclinical Becker's muscular dystrophy presenting with severe heart failure.

We describe a rare case of Becker's muscular dystrophy (BMD) in a 28-year-old man complicated by rapidly progressing heart failure without apparent clinical signs of neuromuscular disease. He showed rhabdomyolysis, which repeatedly occurred causing acute renal failure as heart failure worsened. His serum creatine kinase (CK) level was generally below 300 IU/l. However, it exceeded more than 10,000 IU/l at the time of myoglobinuria. This suggests that the worsening of heart failure could induce rhabdomyolysis in a BMD patient. Gene analysis for BMD should be considered when the elevation of serum CK is noted in heart failure.

LOX-1 pathway affects the extent of myocardial ischemia-reperfusion injury.

Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) was originally identified as a receptor for oxidized low-density lipoprotein predominantly expressed in endothelial cells. LOX-1 expression can be induced in cardiomyocytes and that activation of LOX-1 is involved in apoptosis. To investigate possible roles of LOX-1 in myocardial ischemia-reperfusion injury, rats were subjected to coronary artery ligation for 1h followed by reperfusion for 2h. Immunohistochemistry revealed that expression of LOX-1 in cardiac myocytes was induced following ischemia-reperfusion but not ischemia alone. Administration of anti-LOX-1 monoclonal antibody resulted in a nearly 50% reduction in myocardial infarction size compared with that of normal IgG or saline (P<0.05). These findings suggest that activation of the LOX-1 pathway is involved in determining the extent of myocardial ischemia-reperfusion injury and that inhibition of the LOX-1 pathway may provide a novel strategy for treatment of acute myocardial infarction in humans.

[Adaptation in properties of skeletal muscle to coronary artery occlusion/reperfusion in rats].

The present study was designed to determine if changes in function and metabolism of heart muscle induce alterations in characteristics of skeletal muscle. We investigated the histochemical and biochemical properties of soleus (SOL) and extensor digitorum longus (EDL) muscles in Wistar rats at the chronic phase after coronary artery occlusion/reperfusion. The size of myocardial infarct region was evaluated using a high resolution pinhole single photo emission computed tomography (SPECT) system. 4 wk after left coronary artery occlusion/reperfusion, the SOL and EDL of hindlimb were dissected out and immersed in isopentane cooled with liquid nitrogen for subsequent histochemical and biochemical analysis. From SPECT imaging, the blood circulation was recovered, but the recovery of fatty acid metabolism was not observed in infarct region of heart. Citrate synthase (CS) and 3-hydroxyacyl-CoA dehydrogenase (HAD) activities in infarct region of heart were lower in the myocardial infarction (MI, n = 6) group compared with that of age-matched sham-operated (Sham, n = 6) group. In addition, heart muscle hypertrophy caused by the dysfunction in MI group was observed. In skeletal muscle, the atrophy and transition of fiber type distribution in MI group, reported in previous studies of heart failure, were not observed. However, the succinate dehydrogenase (SDH) activity in the slow twitch oxidative (SO) from SOL of MI group decreased by 9.8% and in the fast twitch oxidative glycolytic fibers (FOG), 8.0% as compared with sham group. Capillary density of the SO fibers from SOL of MI group also reduced by 18.5% and in the FOG fibers, 18.2% as compared with Sham group. Decreased capillary density in this study related significantly to decreased SDH activity of single muscle fibers in chronic phase of perfusion after surgical infarction. Our results make it clear that there is a difference in the reaction of skeletal muscle to coronary artery occlusion/reperfusion compared with chronic heart failure. However, our data would support the notion that there is a linkage between the function of heart and physiological properties of skeletal muscle.