Ventricular Tachyarrhythmias

The mechanisms of ventricular tachyarrhythmias fall into two broad categories of increased automaticity and reentry. It is usually difficult to differentiate clinically between the two mechanisms; however, I plan to discuss certain approaches that may be helpful in this regard

Long QT: Good, bad or indifferent?

A survey of current literature suggests an increasing interest in both the desirable and undesirable implications of a prolonged QT interval, the former perceived to be the beneficial effect of antiarrhythmic drugs that prolong the duration of ventricular action potential, and the latter considered to be a potential marker for sudden cardiac death in patients with ischemic heart disease. In addition, there has been an increasing interest in the congenital long QT syndrome associated with an apparent dysfunction of the autonomic nervous system and serious, potentially lethal ventricular arrhythmias. Circumstantial evidence suggests that these arrhythmias are due to increased dispersion of repolarization which may be aggravated by psychologic and emotional perturbations.In this review, the associations between the long QT interval, autonomic nervous system, dispersion of repolarization, antiarrhythmic drugs and ventricular arrhythmias are examined. Attention is directed to the difficulties of accurate QT measurement, problems related to the correction of the QT interval for heart rate and sex (QTC), the wide range of normal values and the modest QT alterations after various manipulations of the autonomic nervous system. Clinical conditions as- sociated with marked, moderate and occasional QT lengthening are listed and discussed briefly in relation to the disturbances of nervous system, dispersion of ventricular repolarization and ventricular arrhythmias.It is proposed that the absence of relevant animal models of neurogenic or psychogenic QT prolongation hinders the investigation of the neurogenic factors associated with QT lengthening. QT prolongation is most often induced by antiarrhythmic drugs and ischemic heart disease. However, it is not known whether the occurrence of torsade de pointes type of ventricular tachycardia in patients treated with antiarrhythmic drugs is related to a critical drug dose or a critical degree of QTC prolongation. There is no conclusive evidence that QT lengthening has any predictive value either during the acute phase or during convalescence after myocardial infarction. Also, a serious deficiency in current knowledge is the lack of an established relation between the prolonged QT interval and the dispersion of ventricular repolarization. It is concluded that the number of unanswered questions discussed in this review still makes it difficult to judge when a prolonged QT interval is good, bad or indifferent

Hypocapnia Alone Fails to Provoke Important Electrocardiogram Changes in Coronary Artery Diseased Patients

Background: There is still an urgent clinical need to develop non-invasive diagnostic tests for early ischemic heart disease because, once angina occurs, it is too late. Hypocapnia has long been known to cause coronary artery vasoconstriction. Some new cardiology tests are accompanied by the claim that they must have potential diagnostic value if hypocapnia enhances their cardiac effects in healthy subjects. But no previous study has tested whether hypocapnia produces bigger cardiac effects in patients with angina than in healthy subjects. Methods: Severe hypocapnia (a PetCO2 level of 20 mmHg) lasting >15 min was mechanically induced by facemask, while conscious and unmedicated, in 18 healthy subjects and in 10 patients with angina and angiographically confirmed coronary artery disease, awaiting by-pass surgery. Each participant was their own control in normocapnia (where CO2 was added to the inspirate) and the order of normocapnia and hypocapnia was randomized. Twelve lead electrocardiograms (ECG) were recorded and automated measurements were made on all ECG waveforms averaged over >120 beats. 2D echocardiography was also performed on healthy subjects. Results: In the 18 healthy subjects, we confirm that severe hypocapnia (a mean PetCO2 of 20 ± 0 mmHg, P 0.05) on their electro- or echocardiogram. All 10 angina patients tolerated the mechanical hyperventilation well, with minimal discomfort. Hypocpania caused a similar increase in V1 (by 39%, P 0.05 vs. healthy controls) and did not induce angina. Its effects were no greater in patients who did not take β-blockers, or did not take organic nitrates, or had the worst Canadian Cardiovascular Society scores. Conclusion: Non-invasive mechanical hyperventilation while awake and unmedicated is safe and acceptable, even to patients with angina. Using it to produce severe and prolonged hypocapnia alone does produce significant ECG changes in angina patients. But its potential diagnostic value for identifying patients with coronary stenosis requires further evaluation

Dynamics and pattern formation in invasive tumor growth

In this work, we study the in-vitro dynamics of the most malignant form of the primary brain tumor: Glioblastoma Multiforme. Typically, the growing tumor consists of the inner dense proliferating zone and the outer less dense invasive region. Experiments with different types of cells show qualitatively different behavior. Wild-type cells invade a spherically symmetric manner, but mutant cells are organized in tenuous branches. We formulate a model for this sort of growth using two coupled reaction-diffusion equations for the cell and nutrient concentrations. When the ratio of the nutrient and cell diffusion coefficients exceeds some critical value, the plane propagating front becomes unstable with respect to transversal perturbations. The instability threshold and the full phase-plane diagram in the parameter space are determined. The results are in a good agreement with experimental findings for the two types of cells.Comment: 4 pages, 4 figure

Histopathology of Infectious Colitis

Histopathology can play an important role in diagnosing infictious colitis for several reasons. First, colonic mucosal biopsy can often reliably differentiate acute self limited colitis (ASLC). or infectious type colitis, from idiopathic inflammatory bowel disease (IBD). In ASLC, crypt architecture is normal and the inflammatory infiltrate in the lamina propria predominantly acute, ie, polymorphonuclear cells. In IBD, in contrast, crypt architecture is often abnormal nd the inflammatory infiltrate in the lamina propria in both acute and chronic, ie, polymorphonuclear cells, plasma cells ,and lymphocyte are present in increased numbers. Second, biopsy may give a clue to the specific infection. Biopsy may reveal the presence of specific parasites such as Entamoeba histolytica, cryptosporidia or schistosomiasis. Viral inclusions are seen when cytomegalovirus or herpes simplex type II virus infect the colon. Granulomas usually indicate Crohn's disease but can he seen with infections due to Chlamydia trachomatis, Treponema pallidum and Mycobacterium tuberculosis. Both chlamydial and syphilitic proctitis are rare and usually seen in homosexually active men. Finally, pseudomembranes, when present, suggest pseudomembranous colitis due to an overgrowth of toxigenic Clostridium difficile. In summary, mucosal biopsy is helpful in differentiating ASLC from IBD in most cases. Sometimes, it provides a clue to the specific infection

Fulminant Clostridium difficile Infection Cured by Fecal Microbiota Transplantation in a Bone Marrow Transplant Recipient With Critical Neutropenia

Clostridium difficile infection is the most prevalent health care-associated infection. Treatment relies on antimicrobial therapy with mounting evidence supporting fecal microbiota transplant (FMT) in refractory cases. Cohort studies have documented the safety of FMT in immunocompromised patients. However, the safety of FMT in patients with critically low (<500/μL) absolute neutrophil count is unknown. Currently, in severely immunocompromised bone marrow or solid organ transplant recipients, FMT is delayed until normalization of absolute neutrophil count. We present a patient with absolute neutropenia in whom sequential FMTs were safely and successfully administered, resulting in cure of fulminant C. difficile infection

Regulatory Oversight and Safety of Probiotic Use

Saccharomyces boulardii probiotics should be used with caution for management of Clostridium difficile infections in hospitalized patients

Incidence of Ischemic Colitis and Serious Complications of Constipation Among Patients Using Alosetron: Systematic Review of Clinical Trials and Post-Marketing Surveillance Data

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75196/1/j.1572-0241.2006.00459.x.pd

Lauric acid is an inhibitor of Clostridium difficile growth in vitro and reduces inflammation in a mouse infection model

Indexación: Scopus.Clostridium difficile is a Gram-positive, spore-forming anaerobic human gastrointestinal pathogen. C. difficile infection (CDI) is a major health concern worldwide, with symptoms ranging from diarrhea to pseudomembranous colitis, toxic megacolon, sepsis, and death. CDI onset and progression are mostly caused by intestinal dysbiosis and exposure to C. difficile spores. Current treatment strategies include antibiotics; however, antibiotic use is often associated with high recurrence rates and an increased risk of antibiotic resistance. Medium-chain fatty acids (MCFAs) have been revealed to inhibit the growth of multiple human bacterial pathogens. Components of coconut oil, which include lauric acid, have been revealed to inhibit C. difficile growth in vitro. In this study, we demonstrated that lauric acid exhibits potent antimicrobial activities against multiple toxigenic C. difficile isolates in vitro. The inhibitory effect of lauric acid is partly due to reactive oxygen species (ROS) generation and cell membrane damage. The administration of lauric acid considerably reduced biofilm formation and preformed biofilms in a dose-dependent manner. Importantly, in a mouse infection model, lauric acid pretreatment reduced CDI symptoms and proinflammatory cytokine production. Our combined results suggest that the naturally occurring MCFA lauric acid is a novel C. difficile inhibitor and is useful in the development of an alternative or adjunctive treatment for CDI.https://www.frontiersin.org/articles/10.3389/fmicb.2017.02635/ful