Defibrillation: The stopping of a fast heart rate by delivering a high-energy electrical shock to restore the heart’s normal rhythm. Electrical current is used to restore the heart’s natural pacemaker function which resumes a normal heartbeat. The shock is administered through electrodes placed on the chest wall (external defibrillation) or in the heart (internal defibrillation).
Defibrillator: An internal or external device that can deliver an electric shock to stop extremely rapid and irregular heartbeats and return the heart to normal rhythm.
Dilatation: Gradual opening of the narrowed coronary artery by cracking and compressing the narrowing or obstructing plaque.
Dual-Chamber Pacemaker: A pacemaker that monitors and paces a chamber of the upper heart and a chamber of the lower heart at the same time. A dual-chamber pacemaker usually has two leads – one located in the right atrium and the other located in the right ventricle.
Dual-Chamber Pacing: To pace and/or sense heart rhythm in both the atrium and the ventricle.
Death Rate: A death rate that has been standardized for age so different populations can be compared or the same population can be compared over time.
Deep Vein Thrombosis: A blood clot in a deep vein in the calf.
Defibrillator: A machine that helps restore a normal heart rhythm by delivering an electric shock.
Diabetes: A disease in which the body doesn’t produce or properly use insulin. Insulin is needed to convert sugar and starch into the energy used in daily life.
Diastolic Blood Pressure: The lowest blood pressure measured in the arteries. It occurs when the heart muscle is relaxed between beats.
Digitalis: A medicine made from the leaves of the foxglove plant. Digitalis is used to treat congestive heart failure (CHF) and heart rhythm problems (arrhythmias). Digitalis can increase blood flow throughout the body and reduce swelling in the hands and ankles.
Dissecting Aneurysm: A condition in which the layers of an artery separate or are torn, causing blood to flow between the layers. Dissecting aneurysms usually happen in the aorta, the large vessel that carries blood from the heart to other parts of the body.
Diuretic: A drug that lowers blood pressure by causing fluid loss. Diuretics promote urine production.
Doppler Ultrasound: A technology that uses sound waves to assess blood flow within the heart and blood vessels and to identify leaking valves.
Dysarthria: A speech disorder resulting from muscular problems caused by damage to the brain or nervous system.
Dyspnea: Shortness of breath.