The clinical presentation may not be apparent, as MAT may alternate with periods of normal sinus rhythm [1], but abnormally high rates of atrial (400 beats/min) and ventricular (150-250 beats/min) firing are the main features of MAT. Many patients can remain asymptomatic for a prolonged period of time, but up to 40% of patients have some form of structural heart disease (SHD) - Tetralogy of Fallot, patent ductus arteriosus (PDA), atrial septal defect (ASD), hypertrophic cardiomyopathy, pulmonary atresia and several other [4]. SHD may be life-threatening in some cases, which is why an early diagnosis is detrimental.

• Anemia

  […] automaticity due to causes listed below Causes COPD CHF Sepsis Methylxanthine toxicity / Theophylline toxicity Electrolyte abnormalities Other associations Valvular heart disease DM Acute renal failure Postoperative state Pulmonary embolism Pneumonia Anemia [wikem.org]

  However, if arrhythmia persists despite the treatment of underlying medical conditions it may be worth checking a complete blood count and serum chemistry for signs of infection, anemia, or electrolyte abnormalities such as hypokalemia and hypomagnesemia [ncbi.nlm.nih.gov]

  An underlying cause for the tachycardia eventually becomes apparent including anemia, volume depletion, hypoxia, pain, anxiety, or a drug effect (i.e., dopamine, albuterol). [thecardiologyadvisor.com]

• Failure to Thrive

  When symptoms occur, they can include: Chest tightness Light-headedness Fainting Sensation of feeling the heart beat ( palpitations ) Shortness of breath Weight loss and failure to thrive in infants Other symptoms that can occur with this disease: Breathing [coordinatedhealth.com]

  When symptoms occur, they can include: Chest tightness Lightheadedness Fainting Sensation of feeling the heart is beating irregularly or too fast ( palpitations ) Shortness of breath Weight loss and failure to thrive in infants Other symptoms that can [mclaren.org]

  When symptoms occur, they can include: Chest tightness Lightheadedness Fainting Sensation of feeling the heart is beating irregularly or too fast (palpitations) Shortness of breath Weight loss and failure to thrive in infants Other symptoms that can occur [pennstatehershey.adam.com]

• Vascular Disease

  The most important contraindications to use of beta blockers are severe bradycardia and hypotension and acute asthma; other risks include exacerbating peripheral vascular disease and masking severe hypoglycaemia in patients with unstable diabetes. [cardiologytoday.com.au]

An irregular heart rate can be detected during the physical examination, but to discern the type and the severity, ECG is necessary. Diagnostic criteria for MAT include [1] [2]:

• A Heart rate of 100 beats/min (although certain authors propose that 90 beats/min should be the threshold limit).
• Multiple (at least three) distinct P-wave morphologies.
• Irregular P-P intervals.
• The presence of an isoelectric baseline between P waves.

Echocardiography should be performed in order to determine or exclude SHD.

• Premature Atrial Contractions

  In several patients there seemed to be a transition from multifocal premature atrial contractions through chaotic atrial tachycardia to atrial fibrillation. [ahajournals.org]

  Six patients had 3 to 6 premature atrial contractions per minute. No adverse effects were noted, and arterial blood gases before and after therapy were comparable. [ncbi.nlm.nih.gov]

  Premature atrial contraction Premature ventricular contraction Non-arrhythmic cardiac causes: Acute coronary syndrome Cardiomyopathy Congenital heart disease Congestive heart failure (CHF) Mitral valve prolapse Pacemaker complication Pericarditis Valvular [wikem.org]

  Arrhythmias included: Normal Sinus (NSR) Sinus Arrhythmia Atrial Fibrillation (AFib) Atrial Flutter (AFlutter) Supraventricular Tachycardia (SVT) Atrioventricular Nodal Reentry Tachycardia (AVNRT) Premature Atrial Contractions (PACs) Premature Ventricular [play.google.com]

Numerous antiarrhythmic agents have been used in the treatment of symptomatic MAT, including digoxin, flecainide, propafenone, propranolol and many other, as standardized therapy does not exist at the moment [4]. Amiodarone, a class III antiarrhythmic agent, has emerged as one of the most efficient drugs in restoring normal sinus rhythm and has shown very good long-term effects [1] [4].

Earlier studies have reported a significant mortality rate from MAT (38%-62%) [6], but with marked advances in general care, the prognosis of patients suffering from MAT are very good [1]. The long-term outcome, however, depends on the presence of comorbidities and their severity, as COPD or some forms of congenital heart disease may substantially affect the quality of life [1].

At this moment, the exact cause of MAT remains unknown. It usually arises due to an underlying medical disease.

The incidence rate of MAT in the general population is estimated at 0.02% according to isolated reports and it is very rarely seen in clinical practice, as only 100 cases have been described in literature up to 2006 [4]. Use of theophylline, hypoxemia, acidosis, electrolyte imbalance and catecholamine excess are considered as risk factors [5], as were COPD and congestive heart failure [2] [5]. The diagnosis is most frequently made in elderly individuals [1].

One of the theories includes increased intracellular calcium overload, seen in hypokalemia, acidosis, and hypoxia, inducing a higher rate of neuronal activation [6]. The exact pathogenesis model, however, remains unknown.

At this moment, prevention strategies do not exist, as the exact cause remains unknown.

Multifocal atrial tachycardia (MAT, also known as chaotic atrial rhythm) is characterized by a heart rate of > 100 beats/min, multiple distinct P-waves, irregular P-P intervals and the presence of an isoelectric baseline between P-waves on electrocardiography (ECG) [1]. This irregular atrial arrhythmia is most frequently encountered in elderly patients with preexisting cardiac or respiratory diseases such as congestive heart failure or chronic obstructive pulmonary disease (COPD), and it is very rarely described in the pediatric population [1] [2] [3]. The pathogenesis of MAT involves rapid activation of atria by impulses from multiple sites, but the exact cause remains unknown [1]. The clinical presentation involves an abnormally high atrial (400 beats/min) and ventricular (150-250 beats/min) activity, although they may alternate with periods of normal sinus rhythm. For this reason, many patients, especially children, may be asymptomatic [1]. A variety of anatomic anomalies of the heart (atrial septal defect, hypertrophic cardiomyopathy, tetralogy of Fallot, etc) can be present, however, in which case life-threatening cardiac disease can be present [4]. The diagnosis is made by ECG and echocardiography, while amiodarone is the drug of choice in transforming the irregular heart rate to sinus rhythm [4].

Multifocal atrial tachycardia is a rare type of arrhythmia in which abnormal beats of the atria are generated from at least three different sources, leading to a profoundly increased heart rate. The cause of MAT remains unknown and numerous risk factors have been proposed, including the presence of diseases such as congestive heart failure and chronic obstructive pulmonary disease and toxicity due to theophylline. MAT is most frequently diagnosed in elderly with preexisting cardiopulmonary disease, but it may also be encountered in children. In fact, up to 40% of children suffering from MAT have some structural heart disease - Patent ductus arteriosus, tetralogy of Fallot, atrial septal defect, etc. Many patients are asymptomatic, however, primarily because irregular heart beats may alternate with normal heart rhythm. Nevertheless, the diagnosis should be made as early as possible and electrocardiography studies are the used to describe typical features. Numerous antiarrhythmic drugs are used in therapy, as guidelines for therapy do not exist, but amiodarone has shown both short-term and long-term benefits and is recommended for use in patients suffering from MAT.

1. Bradley DJ, Fischbach PS, Law IH, Serwer GA, Dick M 2nd. The clinical course of multifocal atrial tachycardia in infants and children. J Am Coll Cardiol. 2001;38(2):401-408.
2. Kothari SA, Apiyasawat S, Asad N, Spodick DH. Evidence supporting a new rate threshold for multifocal atrial tachycardia. Clin Cardiol 2005;28:561.
3. McCord J, Borzak S. Multifocal atrial tachycardia. Chest. 1998;113(1):203-209. Kim LK, Lee CS, Jeun JG. Development of multifocal atrial tachycardia in a patient using aminophylline -A case report-. Korean J Anesthesiol. 2010;59:S77-S81.
4. Hsieh MY, Lee PC, Hwang B, Meng CC. Multifocal atrial tachycardia in 2 children. J Chin Med Assoc. 2006;69(9):439-443.
5. Kim LK, Lee CS, Jeun JG. Development of multifocal atrial tachycardia in a patient using aminophylline -A case report-. Korean J Anesthesiol. 2010;59:S77-S81.
6. Scher DL, Arsura EL. Multifocal atrial tachycardia: mechanisms, clinical correlates, and treatment. Am Heart J. 1989;118(3):574-580.