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La causa de la enfermedad isquémica del corazón depende del tipo que tenga. La enfermedad isquémica del corazón también puede tener más de una causa, incluida la acumulación de placa o cambios moleculares en los vasos sanguíneos.

Hay tres tipos principales de enfermedad isquémica del corazón: enfermedad arterial coronaria obstructiva; enfermedad arterial coronaria no obstructiva; y enfermedad coronaria microvascular. La enfermedad arterial coronaria afecta las arterias grandes en la superficie del corazón y muchas personas tienen formas obstructivas y no obstructivas de esta enfermedad. La enfermedad coronaria microvascular afecta a las pequeñas arterias en el músculo cardíaco. Puede ocurrir con enfermedad arterial coronaria o sin esta.

A stress test is usually done in a hospital or doctor’s office. Your doctor will give you instructions to prepare for the test and tell you what to expect during and after the test.

To diagnose a circadian rhythm disorder, your doctor may review your medical history; ask about your symptoms, sleep patterns, and environment; do a physical exam; and order diagnostic tests.

Signs and symptoms of circadian rhythm disorders can vary depending on the type of circadian rhythm disorder you have and how severe your condition is. Many of the symptoms of circadian rhythm disorders occur because you are not getting enough good-quality sleep when your body needs it. Undiagnosed and untreated circadian rhythm disorders may increase your risk of certain health conditions or cause workplace or road accidents.

You may have a higher risk for circadian rhythm disorders because of internal factors such as your age, your sex, family history and genetics, and certain medical conditions that affect your brain or vision. External factors such as your lifestyle habits, environment, and occupation can also increase your risk.

Circadian rhythm disorders occur when your sleep-wake cycle is out of sync with your environment. Many factors, both internal and external, can cause you to have problems sleeping and raise your risk for a circadian rhythm disorder.

The types of circadian rhythm disorders are advanced or delayed sleep-wake phase disorder, irregular or non–24-hour sleep-wake rhythm disorder, and shift work or jet lag disorder. The type you may have is based on your pattern of sleep and wakefulness.

Breathing involves two phases: breathing in and breathing out. Your lungs deliver oxygen and remove carbon dioxide from your blood in a process called gas exchange. Gas exchange happens in the capillaries surrounding the alveoli, where the oxygen that is breathed in enters the circulatory system and carbon dioxide in the blood is released to the lungs and then breathed out. If you have problems breathing, gas exchange may be impaired, increasing the risk of serious health problems.

The body’s muscles and nervous system help control your breathing. The lungs are like sponges; they cannot move on their own. Muscles in your chest and abdomen contract, or tighten, to create space in your lungs for air to flow in. The muscles then relax, causing the space in the chest to get smaller and squeeze the air back out. Your breathing usually does not require any thought, because it is controlled by the autonomic nervous system, also called the involuntary nervous system.