Domenico Spaziani, Massimo Pagani, FrancescoNaccarella*, S. De Servi, PaolaMontanari**, Salvatore Romano**.
Divisione di Cardiologia, Ospedale di Legnano, **Ospedale Maggiore di Milano IRCCS, *Azienda Ospedaliera Citta di Bologna, Italy
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Atrial fibrillation represents the arrhythmia
most commonly encountered in practical clinical work.
The social costs associated with the management of the disease is exceedingly relevant,
and the therapeutic strategies implemented for the effective treatment of this pathology
have become more and more refined in the last few years.
Atrial fibrillation is considered a low risk pathologic event related to mortality, but it has
been noted for years how these arrhythmias are burdened by the elevated risk of
complications from embolic events particularly among the elderly patients.
Over the last years, we have consequently witnessed the evolution of various
therapeutic protocols for pharmacological cardioversion of this arrhythmia; the use of
sophisticated electrophysiologic mapping studies in order to explain the
electrophysiologic substrate of atrial fibrillation; the introduction in clinical practice of
transcatheter ablation therapies of such substrate; the introduction of radiofrequency
atrioventricular modulation or total junctional ablation with a subsequent pace-maker
implant; the possibility of obtaining a restored sinus rhythm through transthoracic
electrical cardioversion or internal cardioversion.
Everyone has been able to observe the attempt, in these years, on one hand to control
the symptoms associated with arrhythmia, and on the other hand to reduce the possible
complications by the maintenance of sinus rhythm an through the treatment of these
patients with anticoagulation therapies.
If, in fact, the risk of complications for embolic events is constantly present during
arrhythmia, the risk is particularly high at the moment of cardioversion to sinus rhythm
and in the following days. It has been known for some time that the anticoagulation
therapies are able to reduce the incidence of embolic events from 4 to 0.5% in patients
with atrial fibrillation lasting more than 48 hours1.
The recovery of atrial mechanical function does not always coincide with the restored
sinus rhythm, and from this arises the need to treat these patients with anticoagulants
in the weeks following the achieved cardioversion.
The cardioversion of the atrial fibrillation may be performed with drugs or electrically
with DC shock. This latter possibility has recently been complemented with the so-called
internal electrical cardioversion. The current trend on the other hand is that of
performing the cardioversion with drugs in patients recently developing atrial fibrillation,
and to perform trans-thoracic cardioversion in patients with a long history of atrial
fibrillation, or in case of a failed attempt with drugs, and to reserve the internal
cardioversion for patients not responding to trans-thoracic procedure.
The effort to remotely maintain the sinus rhythm has been particularly effective when:
– the left atrial diameter is not high;
– arrhythmia is recent (<3 months);
– there are no heart failure, valvular disease or hypertension;
– patient is not suffering from ischaemic disease.
If the maintenance of sinus rhythm is inversely correlated to the duration of the atrial
fibrillation, the duration of the atrial stunning after cardioversion is directly correlated
to the time that the arrhythmia has persisted. This phenomenon has been known for
some years2.
The phenomenon of atrial stunning resulting in blood slow flow and in successive
possibility of intra-atrial thrombus formation, does not at this time have a clear and
univocal explanation. The first studies that reported the latency between the
disappearance of the P wave from the ECG and the functional mechanical recovery
of the atrium , evaluated on the echocardiogram through the re-appearance of the
A wave or the increase in velocity of the same on the mitral doppler flow, correlated
this phenomenon with the effects of energy delivered. Consequently, it has been
hypothesized that this event was caused exclusively by the energy delivered, and
subsequently by the number and voltage of the discharges3-4.
Omran et al5 have later demonstrated, however, that the atrial stunning was present
also after internal cardioversion, a methodology that requires low energy delivery.
On the other hand, in the Manning’s study6, the atrial stunning appeared both in
patients who had been treated with electrical cardioversion, as well as in patients
where the attempted pharmacological therapies have been successful ; even though
the stunning in the first group lasted longer and was more intense.
On the basis of data reported in literature, it seems that the phenomenon of mechanical
atrial stunning relates to the restoration of the sinus rhythm itself and not to the
methodology used in order to achieve it7: among the variables that could negatively
influence the restoration of contractile function of the atrium, a major role is played
by the duration of atrial fibrillation and the use of anti-arrhythmic drugs with negative
inotropic effects as sotalol.
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