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Ischemia, electrolyte, pH abnormalities, or bradycardia are potential causes of functionally defined re-entry due to changes in the properties of the cardiac tissue's functional core. [2] (No accessory pathway required). For reentry to occur, the path length of circuit should be greater than the wave length (ERP × conduction velocity) of impulse.
Cardiac stress testing is used to determine to assess cardiac function and to disclose evidence of exertion-related cardiac hypoxia. Radionuclide testing using thallium or technetium can be used to demonstrate areas of perfusion abnormalities. With a maximal stress test the level of exercise is increased until the person's heart rate will not ...
The underlying mechanism typically involves an accessory pathway that results in re-entry. [3] Diagnosis is typically by an electrocardiogram (ECG) which shows narrow QRS complexes and a fast heart rhythm typically between 150 and 240 beats per minute. [3] Vagal maneuvers, such as the Valsalva maneuver, are often used as the initial treatment. [4]
Abnormal impulses can begin by one of three mechanisms: automaticity, re-entry, or triggered activity. A specialized form of re-entry which is both common and problematic is termed fibrillation. [citation needed] Although the term "tachycardia" has been known for over 160 years, bases for the classification of arrhythmias are still being discussed.
They are generally due to one of two mechanisms: re-entry or increased automaticity. [3] Diagnosis is typically by electrocardiogram (ECG), Holter monitor, or event monitor. [4] Blood tests may be done to rule out specific underlying causes such as hyperthyroidism, pheochromocytomas, or electrolyte abnormalities. [4]
The following outline is provided as an overview of and topical guide to cardiology, the branch of medicine dealing with disorders of the human heart. [1] The field includes medical diagnosis and treatment of congenital heart defects, coronary artery disease, heart failure, valvular heart disease and electrophysiology.
Lown–Ganong–Levine syndrome (LGL) is a pre-excitation syndrome of the heart. Those with LGL syndrome have episodes of abnormal heart racing with a short PR interval and normal QRS complexes seen on their electrocardiogram when in a normal sinus rhythm.
Junctional ectopic tachycardia (JET) is a rare syndrome of the heart that manifests in patients recovering from heart surgery. [1] It is characterized by cardiac arrhythmia, or irregular beating of the heart, caused by abnormal conduction from or through the atrioventricular node (AV node).