Effect of intravenous metoprolol on left ventricular performance in Q-wave acute myocardial infarction

Bacterial Community Coexisting with White-Rot Fungi in Decayed Wood in Nature

Lignin-decomposing ability of several bacteria and the degradation mechanism have been revealed in vitro. However, the abundance of such bacteria in decayed wood in nature remains unknown at genus and species levels. This study was aimed at identifying bacterial communities in the decayed wood coexisting with white-rot fungi, which play a potential role in lignin degradation, and predicting the functional profile of bacterial lignin degradation in wood via bacterial community analyses. The bacterial flora of forest soil and four decayed wood samples showed marked differences; particularly, in addition to Methylobacterium and Acidibrevibacterium, sphingomonads, which degrade the major skeleton of lignin in vitro, were more abundant in the decayed wood than in forest soil, suggesting that multiple bacteria were involved in lignin degradation. The bacterial community in the decayed wood was more influenced by wood type and lignin structure than the fungal species observed in the decayed wood.

Effects of propranolol on the left ventricular volume of normal subjects during CT coronary angiography

OBJECTIVE

The purpose of this study is to determine the effects of propranolol on the left ventricular (LV) volume during CT coronary angiography.

MATERIALS AND METHODS

The LV volume of 252 normal Chinese subjects (126 subjects with propranolol medication and 126 age- and gender-matched Chinese subjects without medication) was estimated using 64 slices multi-detector CT (MDCT). The heart rate difference was analyzed by the logistic linear regression model with variables that included gender, age, body height, body weight, systolic blood pressure (SBP), diastolic blood pressure (DBP) and the dosage of propranolol. The following global LV functional parameters were calculated: the real-end diastolic volume (EDV), the real-end systolic volume (ESV) and the real-ejection fraction (EF).

RESULTS

The female subjects had a greater decrease of heart rate after taking propranolol. The difference of heart rate was negatively correlated with the dosage of propranolol. The real-EDV, the real-ESV and the real-EF ranged from 48.1 to 109 mL/m², 6.1 to 57.1 mL/m² and 41% to 88%, respectively. There was no significant difference in the SBP and DBP between the groups without and with propranolol medication (123 ± 17 and 80 ± 10 mmHg; 120 ± 14 and 80 ± 11 mmHg, respectively). The real-EDV showed no significant difference between these two groups, but the real-ESV and real-EF showed significant differences between these two groups (69.4 ± 9.3 and 70.6 ± 8.9 mL/m²; 23.5 ± 5.7 and 25.6 ± 3.7 mL/m², 66.5 ± 5.1% and 63.5 ± 4.6%, respectively).

CONCLUSION

The difference of heart rate is significantly influenced by gender and the dosage of propranolol. Propranolol will also increase the ESV, which contributes to a decreased EF, while the SBP, DBP and EDV are not statistically changed.

Beta-blockers for cardiac CT: a primer for the radiologist

OBJECTIVE

The objective of this article is to describe a protocol for the administration of beta-blockers for cardiac CT. A low and regular heart rate is necessary for optimal visualization of the coronary arteries on CT and can be achieved by the administration of medications.

CONCLUSION

Beta-blockers can be safely given, orally or IV, to most patients to lower the heart rate for cardiac CT. A protocol can be implemented and patients can be screened for certain contraindications to allow successful administration of these medications by radiologists.

Can thromboembolism be the result, rather than the inciting cause, of acute vascular events such as stroke, pulmonary embolism, mesenteric ischemia, and venous thrombosis?: a maladaptation of the prehistoric trauma response

Thromboembolism is considered the inciting cause of many vascular disorders including acute coronary syndrome (ACS), ischemic stroke, pulmonary embolism (PE), deep vein thrombosis (DVT), and mesenteric ischemia. Adrenergia and inflammation are known to accompany these conditions, particularly among arterial thromboembolic disorders, but the teleologic basis of these associations remains poorly understood. We argue that thromboembolism may sometimes be the result, rather than the cause, of acute vascular events, and may be precipitated by underlying adrenergia. Thromboembolic events are most prone to occur during parts of the circadian, seasonal, lifespan, and reproductive cycles with sympathetic dominance, as well as during behavioral, exertional, physiologic, and iatrogenic activation of sympathetic stress. Molecular evidence suggests that adrenergia and inflammation can promote coagulation and lead to co-activation of the pathways. Acute vascular events that occur without angiographic evidence of occlusion suggest that some infarcts may be attributable to adrenergia alone. "Embolic" disorders may represent asynchronous systemic phenomena rather than clot migration. During acute thromboembolism, downstream tissue hypoxia can activate maladaptive self-propelling cycles of sympathetic bias, inflammation, and coagulation. The counterproductive co-activation of these pathways may reflect a maladaptive interlink forged during the primordial evolution of trauma physiology. Their rapid co-mobilization enables rapid control of hemorrhage, microbial defense, and perfusion maintenance during trauma, but the pathways may behave maladaptively in the setting of modern diseases where endothelial injury may be more often precipitated by smoking, diabetes, dyslipidemia, or hypertension. Sympathetic blockade is already employed in ACS, and beta-blockers are used as antihypertensives to prevent stroke. Our hypothesis suggests that the benefits of beta-blockers in stroke may be independent of antihypertensive effects, and that adrenergia may represent a target for managing all thromboembolic disorders, independent of anti-coagulative and thrombolytic therapies. Perhaps reducing adrenergia, rather than maintaining high cerebral perfusion pressure, may represent a counterintuitive strategy for treating stroke and for reducing reperfusion injury. Plausible mechanisms by which autonomic dysfunction may induce venous thrombosis are discussed, especially in those with baroreceptor dysfunction, immobilization, or dehydration. Unexplained hypercoagulability of cancer may also operate through tumor-induced adrenergia and inflammation.

Effects of beta-adrenergic blocking therapy on left ventricular diastolic relaxation properties in patients with dilated cardiomyopathy

BACKGROUND

The hemodynamic mechanism for the improvement in left ventricle (LV) end-diastolic pressure in cardiomyopathy patients treated with beta-adrenergic blocking agents is controversial. We hypothesized that the salutary effect of this kind of therapy on LV end-diastolic pressure would be indicative of an improvement in late, passive diastolic relaxation properties.

METHODS AND RESULTS

We studied 14 cardiomyopathy patients in normal sinus rhythm with no arteriographic evidence of coronary artery disease and an LV ejection fraction of </=40% by radionuclide angiography both before and after 6 months of metoprolol therapy with simultaneous micromanometry and biplane cineventriculography. Four comparable patients who were not treated with metoprolol were studied in a similar fashion and served as control subjects. In those receiving metoprolol, LV end-diastolic pressure decreased (P=0.001). The isovolumic relaxation index, tau(ln), shortened (P=0.03). In a similar fashion, the LV chamber stiffness constant, kappa, decreased (P=0.02), LV volume elastance improved (P=0.04), and the myocardial stiffness constant, kappa(e), decreased (P=0.02). A multiple regression analysis revealed that the decrease in LV end-diastolic pressure was indicative of significant improvements in tau(ln) and kappa(e) with the relationship: LV end-diastolic pressure=-4.73+0.27 tau(ln)+0.54 kappa(e) (r=0.81, P<0.0001). These LV diastolic relaxation properties did not change or worsened in the control cardiomyopathy patients.

CONCLUSIONS

We conclude that the decrease in LV end-diastolic pressure in cardiomyopathy patients treated with metoprolol is an indicator of improvement in LV diastolic properties resulting from more complete myocardial relaxation.

Pathophysiologic and pharmacologic rationales for clinical management of chronic heart failure with beta-blocking agents

An understanding of the important role of neurohormonal compensatory mechanisms in heart failure has been translated into therapeutic options that can improve cardiac function, alter disease progression, and improve survival. Angiotensin-converting enzyme inhibitors are of proven benefit in this regard, and beta-adrenergic receptor antagonists are potentially another such class of agents. By inhibiting the myocardial effects of chronic adrenergic activation, beta blocking agents may improve left ventricular function or delay its deterioration in patients with heart failure. Aside from blocking beta-adrenergic receptors, other ancillary properties inherent in third-generation beta-blocking agents (such as vasodilation) may exert additional favorable effects. Clinical data generated in subjects with heart failure indicate that beta-antagonist therapy exerts its physiologic and clinical effects through neurohormonal antagonism, generally analogous to angiotensin-converting enzyme inhibitors. Virtually all controlled long-term studies show that beta-blocking agents improve cardiac function and hemodynamics in patients with chronic heart failure, but large-scale trials are needed to ascertain a favorable effect on the natural history of heart failure.

Beta receptor antagonists in the treatment of heart failure

The use of beta-receptor antagonists in the treatment of heart failure is controversial. Available data do not allow general recommendations regarding their use. In dilated cardiomyopathy, several studies suggest that long-term treatment in individual patients reduces symptoms and increases exercise capacity. Short-term treatment is usually not beneficial, except in patients with ischemically induced left ventricular dysfunction. In heart failure, post myocardial infarction and in chronic ischemic heart disease, no proper long-term study has been performed to evaluate its effects. However, patients with acute myocardial infarction tolerate beta blockers, despite the presence of left ventricular dysfunction and long-term prognosis is improved. Newer agents, some with ancillary properties, such as intrinsic activity and vasodilatation, may have advantages. In the future we need a better description of the cardiac status in our patients in order to be able to select those that will respond favorably to beta-receptor antagonists. The mechanisms by which some patients improve are still obscure. Protection against receptor downregulation, restoration of receptor density, protection against cardiotoxicity of catecholamines, and improvement in ischemic systolic and diastolic left ventricular function are all possible. The fear that beta-receptor antagonists are dangerous in heart failure is in most instances not warranted, but an initial deterioration may have to be accepted in order to gain long-term beneficial effects. Ongoing studies in both idiopathic cardiomyopathy and in postinfarction failure will hopefully help us to define the use of beta-adrenoceptor antagonists in the future.