Introduction
Since 2006, the cryoballoon ablation (CBA) technique has revolutionized
the treatment of paroxysmal atrial fibrillation and has become the gold
standard treatment method since 2012. The main reason behind its
efficacy is its simplifying pulmonary vein (PV) isolation, making it a
highly standardized and reproducible procedure [1–3].
Nevertheless, CBA is associated with a significant risk of right
phrenic nerve injury (rPNI) because of the proximity between the right
phrenic nerves and the right-sided PVs during balloon-based ablations
[4]. PNI can be transient or persistent, and that feature depends on
the time to recovery. Transient phrenic nerve paralysis/injury (TPNI)
is defined either as completely resolved before the end of the procedure
[5,6], lasting less than 24 hours [7], or until discharge as
demonstrated by chest fluoroscopy [8]. Any longer period of
diaphragmatic paralysis is defined as persistent or sustained phrenic
nerve injury (PPNI). In a systematic review, the reported incidences of
transient and persistent PNI resulting from ablation with the
first-generation CB were 6.48% and 4.73%, respectively [9]. The
risk of PNI associated with the second-generation CB is even higher with
a reported incidence of transient and persistent PNI being
16.0%–24.7% and 5.4%–7.0%, respectively [10–13]. The
anatomical relationship of the relevant structures makes the risk
unavoidable; however, various techniques have been implemented
throughout the last decade for preventing prolonged rPNI [14]. The
most used technique involves the use of compound motor action potentials
(CMAP). The first record of CMAP was published in 2011 by Franceschi
[15]; later, two studies, including multiple patients, were
published in 2014 with a significant PPNI reduction [16,17].
In this article, we aimed to perform a systematic review of PNI based
on all cryoballoon generations from the last 12 years by conducting a
meta-analysis to assess the efficacy of diaphragmatic stimulation and
CMAP use for PNI protection. Intra-operative physical conditions both
with and without right dome diaphragmatic stimulation and time to
recovery data were collected.