Other Atrial Tachycardias

Sinus tachycardia is the same rhythm as normal sinus rhythm except the rate is greater than 100 beats per minute at rest. Many processes can result in the heart rate increasing at rest. Sinus tachycardia can develop as a desirable response to exercise, pregnancy, and emotion. At times sinus tachycardia may reflect a compensatory adjustment by the circulatory system via the sympathetic nervous system to conditions such as low blood pressure, low blood volume impaired ability of the blood to transport oxygen, or ineffective ventricular ejection. Clinical examples of situations when sinus tachycardia occurs as a compensatory mechanism include anemia, post-surgical blood loss, heart failure, and fever. Sinus tachycardia may also occur in situations associated with abnormally elevated energy expenditure such as pain, cancer, endocrine disorders, and drug toxicity or drug withdrawal. Sinus tachycardia can also be brought on by drugs, including prescription drugs, "recreational" drugs, and over the counter drugs. Sometimes there is not a demonstrable cause. In this situation, the rhythm is referred to as inappropriate sinus tachycardia. In these cases, the sinus node over responds to influences that effect heart rate causing the heart rate to be too fast at rest and with minimal exercise.

Therapy for patients with "appropriate" sinus tachycardia focuses on defining and correcting the underlying process precipitating the increased heart rate. Patients who experience increased heart rates with the use of tobacco, alcohol, caffeine, or adrenaline like drugs should discontinue these substances. For patients with "inappropriate " sinus tachycardia (without apparent cause) medications may be useful in minimizing the tachycardia and its symptoms. In severe cases of sinus tachycardia, ablation of the sinus node can be performed or the ventricular rate can be controlled by AV nodal ablation.

Atrial Tachycardia is a heart rhythm driven by pacemaker activity in atrial sites other than the SA node. Automatic atrial tachycardia is typically associated with heart rates ranging from 150-200 beats/minute. The heart rate may display a "warm-up" in which the abnormal rhythm gradually accelerates after initiation. Often atrial tachycardia is associated with prior heart surgery or lung diseases. The rhythm is most often associated with structural heart disease such as coronary artery diseases, myocardial infarction, severe lung disease and drug toxicity. The origin or focus of the abnormal impulses distinguishes two types of atrial tachycardia depending upon whether the origin or focus of the abnormal impulse appears to involve a single (unifocal) site or multiple (multifocal) sites.

Unifocal atrial tachycardias are usually associated with structural heart disease, severe lung disease, and drug toxicity, or it may occur after open-heart surgery. Unifocal atrial tachycardias can occur in people that have normal hearts. It accounts for about 5% of cases of supraventricular tachycardia. It can be treated with medications or with radiofrequency ablation. Because it can be harder to cure with ablation, medications are used more often with atrial tachycardias than in other types of supraventricular tachycardia.

Multifocal atrial tachycardia is an irregular chaotic rhythm resulting from random firing of several different atrial foci. It usually occurs after age 50 and is exacerbated by respiratory failure. It is common in elderly patients with cardiac or pulmonary disease and affects more men than women. Multifocal atrial tachycardia is seen mostly in people whose lungs are not working well. The best treatment is to improve the function of the lungs. If this cannot be accomplished, verapamil sometimes helps to reduce the heart rate and suppress the firing of the abnormal cells.

Therapy for atrial tachycardia depends upon the nature of the atrial tachycardia and the clinical setting. Ventricular rate control may be achieved with medications or with AV nodal ablation and pacing. Unifocal atrial tachycardia may be amenable to ablation of the tachycardia circuit or may be treatable using medications. Multifocal atrial tachycardia is managed by treating the underlying cause or by medications.