This decreases the ability of hemoglobin to carry oxygen to myocardial tissue.Atherosclerosis is the most common cause of stenosis (narrowing of the blood vessels) of the hearts arteries and, hence, angina pectoris. Some people with chest pain have normal or minimal narrowing of heart arteries; in these patients, vasospasm is a more likely cause for the pain, sometimes in the context of Prinzmetals angina and syndrome X.
Myocardial ischemia also can be the result of factors affecting blood composition, such as the reduced oxygen-carrying capacity of blood, as seen with severe anemia (low number of red blood cells), or long-term smoking. Pathophysiology
Angina results when there is an imbalance between the hearts oxygen demand and supply. This imbalance can result from an increase in demand (e.g., during exercise) without a proportional increase in supply (e.g., due to obstruction or atherosclerosis of the coronary arteries). However, the pathophysiology of angina in females varies significantly as compared to males. Non-obstructive coronary disease is more common in females. Diagnosis
Angina should be suspected in people presenting tight, dull, or heavy chest discomfort that is:
Retrosternal or left-sided, radiating to the left arm, neck, jaw, or back. Associated with exertion or emotional stress and relieved within several minutes by rest. Precipitated by cold weather or a meal.Some people present with atypical symptoms, including breathlessness, nausea, or epigastric discomfort, or burning. These atypical symptoms are particularly likely in older people, women, and those with diabetes.Anginal pain is not usually sharp or stabbing or influenced by respiration.
In this type, the hypoplasia of the cerebellar vermis does not reach past the horizontal midline of the fourth ventricle, and the posterior fossa is also not as large. The authors noted that this form would previously have been classified as simply mega–cisterna magna. In 1999, Calabró et al. first used the phrase Dandy–Walker continuum when referring to proposals that a condition known as Blakes pouch cyst falls under the umbrella of the Dandy–Walker complex proposed by Barkovich. Later authors would put these terms and systems under intense scrutiny and state that they added considerable confusion to the diagnosis of DWM. However, they remain commonly used.In 2011, Spennato et al. came up with a set of criteria based on Klein et al. (2003) that they considered necessary for diagnosis of DWM:
The lower portion of the cerebellar vermis is absent to varying degrees (three quarters, one half or one quarter missing). The posterior fossa (the space behind the cerebellum) is enlarged, and its cerebrospinal fluid flow is continuous with that of the fourth ventricle. The rest of the cerebellar vermis is hypoplastic and is pushed upwards and rotated forwards due to the enlarged posterior fossa. The cerebellar hemispheres are pushed forwards and to the side by the enlarged posterior fossa. The angle at the centre of the cerebellar vermis (representing the location of the fastigial nucleus) is large, giving a flattened appearance to the bottom of the vermis, or the fastigial nucleus is absent entirely.