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................................................................................................ 11.1.3 Multifocal atrial tachycardia Multifocal AT is defined as a rapid, irregular rhythm with at least three distinct morphologies of P waves on the surface ECG. Multifocal AT is commonly associated with underlying conditions, including pulmonary disease, pulmonary hypertension, coronary disease, and valvular heart disease, as well as hypomagnesaemia and theophylline therapy.209 It may also be seen in healthy infants under 1 year of age, and carries a good prognosis in the absence of underlying cardiac disease.210

It may be difficult to distinguish multifocal AT from AF on a single ECG trace, so a 12 lead ECG is indicated to confirm the diagnosis. On the ECG, the atrial rate is >100 b.p.m. Unlike AF, there is a distinct isoelectric period between visible P waves. The PP, PR, and RR intervals are variable. Although it is assumed that the variability of P-wave morphology implies a multifocal origin, there have been very few mapping studies of multifocal AT.

11.1.3.1 Therapy The first-line treatment is management of the underlying condition. Magnesium (i.v.) may also be helpful in patients, even in those with normal magnesium levels.211 Antiarrhythmic medications, in general, are not helpful in suppressing multifocal AT.209 Management often involves slowing conduction at the AVN level to control heart rate. Verapamil has some efficacy in patients with multifocal AT who do not have ventricular dysfunction, sinus node dysfunction, or AV block.212,213 Metoprolol has been found to be superior to verapamil,214 and beta-blockers can be used with caution to treat multifocal AT in the absence of respiratory decompensation, sinus node dysfunction, or AV block. There has also been a case report on the successful use of ibutilide.215 In symptomatic and medically refractory cases in which LV deterioration is seen, AV nodal modification may be used for the control of ventricular rate.216

11.1.4 Macro-re-entrant atrial tachycardias Atrial flutter and focal AT are traditionally defined according to the ECG appearance: continuous regular electrical activity, most commonly a saw-tooth pattern, vs. discrete P waves with an isoelectric line in between. ECGs with flutter-like appearances are mostly due to macrore-entrant atrial circuits but micro-re-entry is also possible. However, MRATs with a significant part of the activation of the circuit in protected areas may display a focal AT pattern, with discrete P waves.220

11.1.4.1 Cavotricuspid isthmus-dependent macrore-entrant AT

11.1.4.1.1 Typical atrial flutter: common (counter-clockwise) and reverse (clockwise). Typical common atrial flutter is the most frequent cavotricuspid isthmus (CTI)-dependent flutter, i.e. a macro-reentry circuit around the tricuspid annulus using the CTI as a critical passage at the inferior boundary. Activation goes downward in the RA free wall, through the CTI, and ascends in the right septum. Activation of the LA is passive. The upper part of the circuit may be anterior or posterior to the superior vena cava. This activation is also known as counter-clockwise (or anticlockwise) when seen from the apex. When the circuit is activated in the opposite direction, i.e. clockwise, it results in a different ECG pattern, then called typical reverse flutter.

11.1.4.1.2 Diagnosis. In counter-clockwise flutter, the circuit results in regular atrial activation from 250330 b.p.m., with negative sawtooth waves in inferior leads and positive waves in V1 (Figure 10). In

Recommendations for the therapy of multifocal atrial tachycardia

Recommendation Classa Levelb

Acute therapy Treatment of an underlying condition is recommended as a first step, if feasible.209 I C i.v. beta-blockers, or i.v. non-dihydropyridine calcium channel blockers (verapamil or diltiazem) should be considered.213,214 IIa B Chronic therapy Oral verapamil or diltiazem should be considered for patients with recurrent symptomatic multifocal AT in the absence of HFrEF.217,218 IIa B A selective beta-blocker should be considered for patients with recurrent symptomatic multifocal AT.214,219 IIa B AV nodal ablation followed by pacing (preferable biventricular or His-bundle pacing) should be considered for patients with LV dysfunction due to recurrent multifocal AT refractory to drug therapy.216 IIa C

AT = atrial tachycardia; HF = heart failure; HFrEF = heart failure with reduced ejection fraction; i.v. = intravenous; LV = left ventricular. i.v. verapamil and diltiazem are contraindicated in the presence of hypotension or HFrEF. i.v. beta-blockers are contraindicated in the presence of decompensated heart failure. aClass of recommendation. bLevel of evidence. A B ©ESC 2019

Figure 10 Counter-clockwise (A) and clockwise (B) atrial flutter with 2:1 atrioventricular conduction. Downloaded from academic.oup.com/eurheartj/article/41/5/655/5556821 by guest on 07 October 2026