Coronary microvascular dysfunction, arrythmias, and sudden cardiac death: A literature review.

The coronary vascular system has a unique structure and function that is adaptive to myocardial demand. It is composed of a continuous network of vessels receding in size from epicardial arteries to the microvascular circulation. Failure to meet myocardial demand results in ischemia, angina, and adverse myocardial outcomes. It is evident that 50 % of patients with angina have a non-obstructive coronary disease and 66 % of these patients have coronary microvascular dysfunction (CMD). The impact of CMD on the atria and ventricles is exhibited through its association with atrial fibrillation and distortion of ventricular repolarization. Ultimately, this influence increases the risk of mortality, morbidity, and sudden cardiac arrest. CMD serves as an independent risk for atrial fibrillation, increases ventricular electrical inhomogeneity, and contributes to the progression of cardiac disease. The underlying pathogenesis may be attributed to oxidative stress evident through reactive oxygen species, impaired vasoactive function, and structural disorders such as fibrotic changes. Myocardial ischemia, brought about by a demand-supply mismatch in CMD, may create a milieu for ventricular arrythmia and sudden cardiac arrest through distortion of ventricular repolarization parameters such as QT dispersion and corrected QT dispersion.

The Arab Countries' Contribution to the Research of Neurodegenerative Disorders.

BACKGROUND: Neurodegenerative diseases are disorders in which nerve cells start to lose function due to different causes. Like many other illnesses, they are considered to be highly prevalent in the 22 Arabic-speaking countries known to constitute the Arab world. The two most prevalent neurodegenerative disorders are Alzheimer's disease and Parkinson's disease. AIM: The aim of this paper is to assess the amount of research dedicated to neurodegenerative diseases by the Arab countries during a 15-year period, between 2005 and 2019. METHODS: The number of publications by each Arab country as well as some non-Arab speaking countries was retrieved from PubMed. Publications in top 10 neuroscience journals were also tracked using the same method with each journal's name included. The numbers were then normalized with respect to the average population and average gross domestic product (GDP) in each country to eliminate bias. RESULTS: Arab countries were shown to contribute only 1,311 (0.774%) of the 169,330 articles published worldwide on neurodegenerative disorders. These 1,311 also constitute only 0.660% of the 198,869 Arab publications during the indicated period. Saudi Arabia had the highest contribution to these numbers with more than one-quarter the number of publications on neurodegenerative disorders. Approximately one-third of all neurodegenerative disease-related articles were associated with Alzheimer's disease, whereas one-fifth were related to Parkinson's disease. For the top 10 neuroscience journals, only a minimal contribution by Arab countries was noted. CONCLUSION: Although an increase in the number of articles by the Arab world was noted from 2013 onward, the contribution of the Arab countries on the subject to the number of publications still seems to be insufficient.