- Causal therapy:
Treatment of the underlying condition.
If the causal cause is digitalis intoxication, (most common cause of multifocal atrial tachycardia) it should be treated as follows (Herold 2022):
- Immediate discontinuation of digitalis
- Promote elimination of digitalis by:
- Antidote treatment with Fab antibody fragments such as DigiFab (Böhm 2000). Dosage:
- if the amount of digitalis is known: 80 mg antidigoxin- Fab bind 1 mg digoxin, so that the digoxin- level decreases by 1ng / ml and for digitoxin by 10 ng / ml (Flake 2021).
- If the amount of digitalis is unknown: bolus of 160 mg as a short infusion in 5% glucose over 20 min, then 20 mg / h over 12 h (Flake 2021)
- Symptomatic therapy of digitalis intoxication in the form of:
- temporary pacemaker
- Atropine for bradycardia (Herold 2022) Dosage: 1mg atropine i. v. (Böhm 2000).
- For ventricular extrasystoles, tachycardia and ventricular flutter use of:
- Magnesium 20 mval i. v. (2 mval = 1 mmol / l (Hartig 2004).
- Phenytoin 100 mg i. v.
- Lidocaine 100 mg i. v.
- defibrillation
- Cardioversion (Böhm 2000)
- Potassium:
Hyperkalemia increases the risk of AV block (Lemmer 2007). Therefore, in case of hyperkalemia, antidote treatment with Fab antibody fragments (see above) should be given immediately (Mori 2012). If no antidote is available, the shift of potassium into the intracellular space can be treated with glucose, insulin, and bicarbonate (Gertsch 2007).
However, potassium is always contraindicated in pre-existing conduction disorders (Lemmer 2007). In case of hypokalemia, potassium should be substituted, except in case of pre-existing conduction disorders (Mori 2012).
- Calcium:
Ca2+ enhances the effect of digitalis and thus promotes toxicity. From there, calcium supplements are contraindicated in digitalis intoxication. Existing hypercalcemia should be corrected promptly (Karow 2021).
- Symptomatic therapy of FAT:
- Drug therapy with e.g.
- beta blockers (Herold 2022)
- Calcium channel blockers
- Adenosine (Kasper 2015)
- antiarrhythmic drugs
- Ivabradine (Brugada 2019).
Beta blockers and antiarrhythmics
Beta-blockers, such as metoprolol or esmolol, and calcium channel blockers, such as verapamil or diltiazem (IIa C [Brugada 2019]), may slow ventricular rate by enhancing AV block, which in turn may improve tolerance to arrhythmias (Kasper 2015).
They should also be used when adenosine administration fails (IIa B [Brugada 2019]).
Nucleoside
The nucleoside adenosine can be used i. v. as a bolus of 6-18 mg for regular narrow complex tachycardia (I B) and for multifocal atrial tachycardia (IIa C [Brugada 2019]).
Administration of adenosine abates some forms of FAT, but there may also be transient enhancement of AV block (in the case of reentry cause, for example) without termination of tachycardia (Kasper 2015).
Antiarrhythmics
Ibutilide i. v. (llb) or amiodarone / flecainide / propafenone (IIb C) may be considered as acute therapy for FAT. However, ibutilide is not available in Germany (Brugada 2019).
Ivabradine
Ivabradine can be considered together with a beta-blocker (see above) as long-term therapy in FAT (llb [Brugada 2019]).
- Cardioversion:
In hemodynamically unstable patients, the guideline (I B) recommends synchronized direct current cardioversion as the first therapeutic measure. If therapy is not successful, antiarrhythmic drugs such as ibutilide, amiodarone / flecainide / propafenone (ll b C) should be used (Brugada 2019).
In hemodynamically stable patients, it is recommended to use synchronized direct current cardioversion only after failure of the above drugs (l B [Brugada 2019]).
- Ablation:
This should be applied when there is a risk of tachycardia-induced cardiomyopathy or when drug therapy is permanently required (Herold 2022), as well as in recurrent FAT (Brugada 2019).
Primarily, adenosine (IIa B) is recommended therapeutically in patients with FAT. If this therapy is unsuccessful, beta blockers (lla C) or calcium channel blockers (lla C) should be used. If this also fails, antiarrhythmic drugs such as ibutilide, flecainide, or propafenone (llb C) should be used. If therapeutic success fails despite drug measures, synchronized direct current cardioversion (l B) is recommended (Brugada 2019).
Long-term therapy
Long-term therapy options include:
- 1. catheter ablation (l B) if FAT is persistent or has already caused cardiomyopathy (Brugada 2019).
- 2. if ablation is not desired by the patient, drug therapy can be used in structurally heart healthy patients in the form of:
- Beta-blockers (see above) or.
- non-dihydropyridine calcium antagonists such as verapamil or diltiazem or
- Flecainide or propafenone (lla C).
In patients without evidence of heart failure with reduced left ventricular ejection fraction (HFrEF), verapamil or diltiazem are recommended (Brudaga 2019).
- 3. if the above options fail, ivabradine should be used in conjunction with a beta-blocker or amiodarone (llb C) if there is no response (Brugada 2019).