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Background: The fragmented QRS complex (FQRS) was found to be associated to malignant ventricular arrhythmias and sudden death in patients with hypertrophic cardiomyopathy and other entities. There is scant data available correlating the presence of FQRS with QT interval prolongation in patients with ischemic heart disease (IHD). Methods: A descriptive, retrospective, cross-sectional study was performed in 123 patients with IHD to analyze and correlate the presence of FQRS with QT interval prolongation in the conventional 12-leads electrocardiogram in patients with documented chronic IHD. Results: There were 62% male patients. The mean age was 63.8±12.6 years. Thirty six (44%) patients had fragmented QRS (64% men and 36% women). The duration of QT and QTc, the mean values were 413±59ms, and 463±67ms, respectively. Of the 36 patients with FQRS, 23 patients have prolongation of the QTc interval, and 13 patients did not present it. Of the 45 patients without FQRS, 21 of them have prolongation of the QTc interval, and 24 patients did not have it. These data resulted in a sensitivity of 52% with a moderate SnNout, a specificity of 65% with moderate SpPin, a positive predictive accuracy of 64%, a negative predictive accuracy of 53%. These data resulted in a prevalence of 54%. Conclusion: the presence of FQRS in the ECG has a moderate sensitivity and specificity, as well as, moderate negative and positive predictive value of the existence of QT interval prolongation in patients with ischemic heart disease. [ABSTRACT FROM AUTHOR]

Little is known about the response of arbuscular mycorrhizal fungal communities to ecosystem development. We use a long-term soil chronosequence that includes ecosystem progression and retrogression to quantify the importance of host plant identity as a factor driving fungal community composition during ecosystem development., We identified arbuscular mycorrhizal fungi and plant species from 50 individual roots from each of 10 sites spanning 5-120 000 yr of ecosystem age using terminal restriction fragment length polymorphism (T- RFLP), Sanger sequencing and pyrosequencing., Arbuscular mycorrhizal fungal communities were highly structured by ecosystem age. There was strong niche differentiation, with different groups of operational taxonomic units ( OTUs) being characteristic of early succession, ecosystem progression and ecosystem retrogression. Fungal alpha diversity decreased with ecosystem age, whereas beta diversity was high at early stages and lower in subsequent stages. A total of 39% of the variance in fungal communities was explained by host plant and site age, 29% of which was attributed to host and the interaction between host and site (24% and 5%, respectively)., The strong response of arbuscular mycorrhizal fungi to ecosystem development appears to be largely driven by plant host identity, supporting the concept that plant and fungal communities are tightly coupled rather than independently responding to habitat. [ABSTRACT FROM AUTHOR]

Most research on the mycorrhizal positive-negative responsiveness continuum (or 'mutualism-parasitism continuum') has focused on individual plant species growing at different levels of P availability. Here, we explore this continuum in an experimental plant community inoculated with three arbuscular mycorrhizal (AM) fungal strains (both single and mixed) growing under four resource availability scenarios. These scenarios are a factorial combination of two levels of water and N availability. Each AM fungal strain had a different origin: an arid ecosystem, a farmland, and a mine. We hypothesized that the response of the plant community to mycorrhizal inoculum would depend on the associated AM fungal strain and would be negatively related with increased nitrogen and water availability. Our results showed that mixed-strain AM fungal inoculation had more positive effects along a wider range of water and N availability scenarios than single-strain inoculation. In contrast, mycorrhizal growth response of plants inoculated with a single AM fungal strain shifted from positive to neutral and negative depending on resource availability. Adaptation of each strain to its local conditions might confer different properties to the mycorrhizal symbiosis. Therefore, we conclude that AM fungal origin and environmental limiting resources are crucial factors to predict plant community mycorrhizal growth response in changing ecosystems. [ABSTRACT FROM AUTHOR]

The development of atrial fibrillation (AF) during the course of the evolution of heart failure (HF) worsens the clinical outcomes and the prognosis accounting for an enormous economic burden on healthcare. AF is considered to be an independent predictor of morbidity and mortality increasing the risk of death and hospitalization in 76% in HF patients. Despite the good clinical results obtained with conventional pharmacological agents and different new drugs, the optimal medical treatment can fail in the intention to improve symptoms and quality of life of HF patients with severe left ventricular dysfunction and AF with uncontrolled ventricular rate. Therefore, the necessity to utilize cardiac devices to perform cardiac resynchronization therapy (CRT), or the need to use catheter ablation, or both, emerges facing the failure of optimal medical treatment in order to achieve hemodynamic improvement. Some of these AF patients will require atrio-ventricular nodal (AVN) catheter ablation in order to restore 100% CRT functionality and improvements in clinical outcomes. It is hard to imagine that the deliberate destruction of a natural and normally functional specialized tissue of the main conduction system of the heart would do any good. However, in the presence of AF with rapid ventricular response due to normal conduction through the AV node in HF patients, the fast ventricular rate can cause deleterious consequences in the clinical outcome. Moreover, there are interesting published data which will be analyzed in this manuscript documenting significant acute and long-term improvement in left ventricular function, symptoms, exercise tolerance, clinical outcomes, and quality of life in selected HF patients with paroxysmal and persistent drug-refractory AF who have undergone AVN ablation and permanent pacemaker implantation. [ABSTRACT FROM AUTHOR]

Atrial fibrillation (AF) is the most common arrhythmia in middle-aged athletes. Physical exercise performed in a regular basis has been shown to be beneficial for cardiovascular health. Moderate physical exercise, aside from producing a nice, peaceful and well-being sensation, has been associated with a reduced risk of AF. However, more strenuous endurance exercise, like the one experiencing marathon runners, seems to increase the risk of AF in healthy athletes without organic heart disease. On the other hand, low physical activity was found to be a risk factor for the appearance of AF. Nevertheless, the relationship of exercise to AF is complex, influenced by the intensity and the duration of the physical activity, and seems to have a U-shaped relationship with the greatest levels of physical activity possibly increasing AF incidence. There is cumulative data associating moderate physical activity to reduced AF incidence, hence physicians should recommend moderate exercise training to patients with AF. This may not only reduce AF risk, but would also contribute to an overall cardiovascular benefit. However, since there is also important data suggesting significant increased incidence of AF in elite athletes with long-term endurance physical activity, it may be a serious concern to go to the extreme. In most things in life it is much better and wiser to be well balanced, always in equilibrium. [ABSTRACT FROM AUTHOR]

Due to the lack of prospective, randomized, controlled clinical studies on inflammation and cardiovascular involvement, the exact mechanism of cardiac injury among patients with Coronavirus Disease 2019 (COVID-19) still remains uncertain. It was demonstrated that there is a high and significantly positive linear correlation between troponin T and plasma high-sensitivity C-reactive protein levels, biomarkers of cardiac injury and systemic inflammation, respectively. Cardiac injury and inflammation is a relatively common association among patients hospitalized with COVID-19, and it is related to higher risk of in-hospital mortality. In our literature search, we identified several potential mechanisms of myocardial tissue damage, namely, coronavirus-associated acute myocarditis, angiotensin-converting enzyme 2 receptor binding affinity to the virus Spike protein, increased cytokine secretion, and hypoxia-induced cardiac myocyte apoptosis. Elucidation of the disease pathogenesis and prospective histopathological studies are crucial for future proper treatment in case of renewed outbreaks. Of interest is that with hundred of thousands of bodies available for autopsy studies, no prospective investigation has been reported so far. Strong efforts and continued research of the cardiovascular complications and identification of risk factors for poor prognosis in COVID-19 are steadily needed. The high morbidity and mortality of COVID-19, its monumental economic burden and social impact, the despair of a new pandemic outbreak, and the thread of potential utilization of novel severe acute respiratory syndrome coronavirus 2 as biologic weapons make it a preponderant necessity to better comprehend the therapeutic management of this lethal disease. Emerging as an acute infectious disease, COVID-19 may become a chronic epidemic because of genetic recombination. Therefore, we should be ready for the reemergence of COVID-19 or other coronaviruses., (Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.)

Atrial fibrillation (AF) is the most common arrhythmia in middle-aged athletes. Physical exercise performed in a regular basis has been shown to be beneficial for cardiovascular health. Moderate physical exercise, aside from producing a nice, peaceful and well-being sensation, has been associated with a reduced risk of AF. However, more strenuous endurance exercise, like the one experiencing marathon runners, seems to increase the risk of AF in healthy athletes without organic heart disease. On the other hand, low physical activity was found to be a risk factor for the appearance of AF. Nevertheless, the relationship of exercise to AF is complex, influenced by the intensity and the duration of the physical activity, and seems to have a U-shaped relationship with the greatest levels of physical activity possibly increasing AF incidence. There is cumulative data associating moderate physical activity to reduced AF incidence, hence physicians should recommend moderate exercise training to patients with AF. This may not only reduce AF risk, but would also contribute to an overall cardiovascular benefit. However, since there is also important data suggesting significant increased incidence of AF in elite athletes with long-term endurance physical activity, it may be a serious concern to go to the extreme. In most things in life it is much better and wiser to be well balanced, always in equilibrium.

The development of atrial fibrillation (AF) during the course of the evolution of heart failure (HF) worsens the clinical outcomes and the prognosis accounting for an enormous economic burden on healthcare. AF is considered to be an independent predictor of morbidity and mortality increasing the risk of death and hospitalization in 76% in HF patients. Despite the good clinical results obtained with conventional pharmacological agents and different new drugs, the optimal medical treatment can fail in the intention to improve symptoms and quality of life of HF patients with severe left ventricular dysfunction and AF with uncontrolled ventricular rate. Therefore, the necessity to utilize cardiac devices to perform cardiac resynchronization therapy (CRT), or the need to use catheter ablation, or both, emerges facing the failure of optimal medical treatment in order to achieve hemodynamic improvement. Some of these AF patients will require atrio-ventricular nodal (AVN) catheter ablation in order to restore 100% CRT functionality and improvements in clinical outcomes. It is hard to imagine that the deliberate destruction of a natural and normally functional specialized tissue of the main conduction system of the heart would do any good. However, in the presence of AF with rapid ventricular response due to normal conduction through the AV node in HF patients, the fast ventricular rate can cause deleterious consequences in the clinical outcome. Moreover, there are interesting published data which will be analyzed in this manuscript documenting significant acute and long-term improvement in left ventricular function, symptoms, exercise tolerance, clinical outcomes, and quality of life in selected HF patients with paroxysmal and persistent drug-refractory AF who have undergone AVN ablation and permanent pacemaker implantation.