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TachycardiaIntroduction Supraventricular tachycardia (SVT) is a heart rhythm disorder featuring episodes of abnormally fast heart rate lasting for seconds, minutes, hours or, in rare cases, days. Episodes may occur regularly or very infrequently (sometimes years apart). The rate may be as high as 300 beats per minute, but is usually between 140 and 180. It is caused by abnormal, fast, electrical spontaneous impulses that arise in the atria, the upper chambers of the heart and override the natural pacemaker. Attacks often come on for no obvious reason but may be triggered by exertion, emotional upset, coffee or alcohol. In most cases, the heart is normal, although the symptoms may be uncomfortable. Symptoms The condition most commonly causes palpitations (the sensation of your heart pounding in your chest). There may also be chest pain, dizziness, light-headedness, fatigue and breathlessness. Rarely, fainting occurs due to a drop in blood pressure. Causes The normal heartbeat is synchronised by a collection of muscle fibres in the upper right chamber of the heart called the sinoatrial node. This is the heart's natural pacemaker. In SVT, fast impulses start up elsewhere, above the ventricles and override the natural pacemaker. The term SVT refers to several different kinds of arrhythmias. The most common is Paroxysmal Supraventricular Tachycardia (PSVT). The paroxysms (temporary episode of disturbance of heart rhythm) are most commonly caused by a short circuit in the electrical system of the heart which causes the electrical signal to continuously travel around in a circle, forcing the heart to beat rapidly. Another specific type of SVT includes Wolff-Parkinson-White syndrome where there is an abnormal electrical connection between the atria and ventricles. This extra tissue forms a short circuit between these chambers, again causing a fast heart beat. In SVT, the heart beats so fast that the heart muscle does not relax between contractions, and this reduces the amount of blood being pumped around the body. SVT may be a side effect of medications such as digitalis, asthma medications, herbal supplements and cold remedies. Caffeine and stress can also cause arrhythmias.In some cases, the cause of supraventricular tachycardia is unknown. Diagnosis Diagnosis can usually be confirmed, and other causes of a fast heart rate ruled, out by using an electrocardiogram (ECG) during an episode of SVT. ECGs trace the rhythm and electrical activity of the heart. They record any abnormal findings in the heart's electrical impulses. Electrodes are placed on the chest, leg and arms and the results are printed on graph paper. Sometimes a 24-hour ECG is used to show a change in rhythm over time. Further tests may be advised once episodes of SVT are confirmed. These aim to determine the exact location within the heart that is triggering the episodes of SVT. Treatment In many cases, the symptoms of SVT stop quickly, and no treatment is needed. Attempts to stop SVT by any means should only be carried out after an ECG has been performed in hospital. Non-drug methods may be tried where you will be asked to hold your nose, close your mouth and breath out strongly (Valsalva manoeuvre) or by someone massaging the carotid sinus in your neck. If symptoms last for a long time, or they are severe, medicines can be injected into a vein. These block the electrical impulses in the heart. Intravenous adenosine is the treatment of choice, with intravenous verapamil usually given when this is not recommended, for example, in asthma patients. Electric shock treatment (cardio version) under sedation is also occasionally used to stop an episode of SVT. Medication may be prescribed to prevent further episodes of SVT. These include digoxin, verapamil, and beta blockers which interfere with the electrical impulses in the heart. Radio frequency ablation is a procedure where catheters are placed inside the heart and a map of electrical activity is charted. When the source of the abnormality is found high-energy radio waves are used to remove the tissue. Ablation has a high success rate in curing SVT. To help relieve symptoms at the point of attack try smelling Ylang Ylang either directly from the bottle or on a tissue. On an ongoing basis try using Chamomile, Lavender, Neroli and Rose in massages and aromatic baths. As attacks can be brought on by stressful situations try reading the section on stress. |
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