| heart conduction system | An impulse-conducting system composed of modified cardiac muscle and having the power of spontaneous rhythmicity and conduction more highly developed than the rest of the heart. (12 Dec 1998) |
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| heart defects, congenital | Imperfections or malformations of the heart, existing at birth. (12 Dec 1998) |
| heart-eating | Preying on the heart. Source: Websters Dictionary (01 Mar 1998) |
| heart hormone | A substance present in extracts of cardiac tissue that augments cardiac contraction; possibly adenosine, a catecholamine, or some non-specific stimulant present generally in tissues. Synonym: cardiac hormone, heart hormone. (05 Mar 2000) |
| heart injuries | General or unspecified injuries to the heart. (12 Dec 1998) |
| heart-lung machine | A combination blood pump and blood oxygenator used for temporary periods of time in cardiopulmonary bypass for cardiac surgery. (12 Dec 1998) |
| heart-lung transplantation | The simultaneous, or near simultaneous, transference of heart and lungs from one human or animal to another. (12 Dec 1998) |
| heart massage | Rhythmic compression of the heart by pressure applied manually over the sternum (closed heart massage) or directly to the heart through an opening in the chest wall (open heart massage). It is done to reinstate and maintain circulation. (12 Dec 1998) |
| heart murmur | A finding on physical examination of the heart that can, in some cases, indicate the presence of cardiac disease. Murmurs result from vibrations set up in the bloodstream and the surrounding heart and great vessels as the result of turbulent flow. (27 Sep 1997) |
| heart murmurs | A sound generated by disturbed blood flow through the heart manifested as "turbulence". Turbulence is an irregular condition of motion caused by local vibrations of the wall of a vessel or heart chamber. Heart murmurs are usually detectable in ventricular outflow obstruction and in various types of heart valve disease and are differentiated from heart sounds, a physiological concept. (12 Dec 1998) |
| heart muscle | <anatomy> Tissue specialised for contraction. See twitch muscle, catch muscle: Cardiac muscle (heart muscle) is a striated but involuntary muscle responsible for the pumping activity of the vertebrate heart. The individual muscle cells are joined through a junctional complex known as the intercalated disc and are not fused together into multinucleate structures as they are in skeletal muscle. Skeletal muscle is a rather non-specific term usually applied to the striated muscle of vertebrates that is under voluntary control. The muscle fibres are syncytial and contain myofibrils, tandem arrays of sarcomeres. Smooth muscle is muscle tissue in vertebrates made up from long tapering cells that may be anything from 20-500m long. Smooth muscle is generally involuntary and differs from striated muscle in the much higher actin/myosin ratio, the absence of conspicuous sarcomeres and the ability to contract to a much smaller fraction of its resting length. Smooth muscle cells are found particularly in blood vessel walls, surrounding the intestine (especially the gizzard in birds) and in the uterus. The contractile system and its control resemble those of motile tissue cells (for example fibroblasts, leucocytes) and antibodies against smooth muscle myosin will cross react with myosin from tissue cells, whereas antibodies against skeletal muscle myosin will not. See: dense bodies. (18 Nov 1997) |
| heart position | A description of the heart's assumed electrical habitus based upon the form of the QRS complexes in leads aVL, aVF, V1, and V6. Sometimes loosely (and inaccurately) used to describe the frontal plane electric axis. Synonym: heart position. (05 Mar 2000) |
| heart rate | The number of beats per minute. Normal resting heart rates are variable with age, sex, size and overall cardiovascular condition. Heart rate can be determined by taking the pulse. Normal heart rate for an average sized adult is in the range of 60-85 beats/minute. (27 Sep 1997) |
| heart rate, foetal | The heart rate of the foetus. The normal range at term is between 120 and 160 beats per minute. (12 Dec 1998) |
| heart-robbing | 1. Depriving of thought; ecstatic. "Heart-robbing gladness." 2. Stealing the heart or affections; winning. Source: Websters Dictionary (01 Mar 1998) |