As the left ventricle becomes unable to compensate for an acute rise in systemic vascular resistance, left ventricular failure and pulmonary edema or myocardial ischemia may occur.In the kidneys, chronic hypertension has a great impact on the kidney vasculature, leading to pathologic changes in the small arteries of the kidney. Affected arteries develop endothelial dysfunction and impairment of normal vasodilation, which alter kidney autoregulation. When the kidneys autoregulatory system is disrupted, the intraglomerular pressure starts to vary directly with the systemic arterial pressure, thus offering no protection to the kidney during blood pressure fluctuations. The renin-aldosterone-angiotensin system can be activated, leading to further vasoconstriction and damage. During a hypertensive crisis, this can lead to acute kidney ischemia, with hypoperfusion, involvement of other organs, and subsequent dysfunction. After an acute event, this endothelial dysfunction has persisted for years. Diagnosis
The term hypertensive emergency is primarily used as a specific term for a hypertensive crisis with a diastolic blood pressure greater than or equal to 120 mmHg or systolic blood pressure greater than or equal to 180 mmHg. Hypertensive emergency differs from hypertensive urgency in that, in the former, there is evidence of acute organ damage. Both of these definitions had collectively been known as malignant hypertension, although this medical term is replaced.In the pregnant patient, the definition of hypertensive emergency (likely secondary to pre-eclampsia or eclampsia) is only a blood pressure exceeding 160 mmHg systolic blood pressure or 110 mmHg diastolic blood pressure.
A hypertensive emergency is very high blood pressure with potentially life-threatening symptoms and signs of acute damage to one or more organ systems (especially brain, eyes, heart, aorta, or kidneys). It is different from a hypertensive urgency by this additional evidence for impending irreversible hypertension-mediated organ damage (HMOD). Blood pressure is often above 200/120 mmHg, however there are no universally accepted cutoff values. Signs of organ damage will be discussed below. Signs and symptoms
Symptoms may include headache, nausea, or vomiting. Chest pain may occur due to increased workload on the heart resulting in inadequate delivery of oxygen to meet the heart muscles metabolic needs. The kidneys may be affected, resulting in blood or protein in the urine, and acute kidney failure. People can have decreased urine production, fluid retention, and confusion.Other signs and symptoms can include:
Chest pain
Abnormal heart rhythms
Headache
Nosebleeds that are difficult to stop
Dyspnea
Fainting or the sensation of the world spinning around them (vertigo)
Severe anxiety
Agitation
Altered mental status
Abnormal sensationsThe most common presentations of hypertensive emergencies are cerebral infarction (24.5%), pulmonary edema (22.5%), hypertensive encephalopathy (16.3%), and congestive heart failure (12%). Less common presentations include intracranial bleeding, aortic dissection, and  pre-eclampsia or eclampsia.Massive, rapid elevations in blood pressure can trigger any of these symptoms, and warrant further work-up by physicians. Physical exam would include measurement of blood pressure in both arms.