Material and Methods
Study population and laboratory analysis : This study was
approved by the institutional review committee and ethics review board
of our hospitals. From 2014 to 2019, 22 consecutive intolerably
symptomatic patients with drug (including beta-blockers, calcium-channel
blockers, and class I agents of the Vaughan Williams classification)
refractory MA-PVCs visited our hospitals to undergo RFCA. All patients
had their history recorded, and underwent a physical examination,
laboratory analysis, 12-lead electrocardiography (12-ECG), 24-h Holter
monitoring, and echocardiography, on admission or within at least 1
month before admission, and 6-months after the successful RFCA. The LV
end-diastolic (LVDd) and systolic (LVDs) internal dimensions, right
ventricle (RV) internal dimension (RVD), degree of mitral regurgitation
(MR), and LV ejection fraction (LVEF) measured by the Teichholz method,
were measured. All the echocardiography values were recorded during
sinus rhythm, but not during PVC beats, nor post-PVC beats. The serum
brain natriuretic peptide (BNP) concentration and New York Heart
Association (NYHA) functional class using a specific activity scale were
evaluated on admission and 6-months after the successful RFCA.
Definition of MA-PVC: Mitral annulus-PVCs were defined as
having a characteristic electrocardiographic appearance of a right
bundle branch block (RBBB) contour in V1 and positive concordant R waves
in the precordial leads including V1~6 (Figure 1A).
Ventricular tachycardia (VT) was defined with standard
electrocardiographic criteria including at least 3 consecutive PVCs at a
rate of > 120 beats per minute. Patients with ventricular
tachycardia and atrial tachyarrhythmias including atrial fibrillation,
atrial flutter, atrial tachycardia, and paroxysmal supraventricular
tachycardia were excluded from this study because they may cause
tachycardia-induced LV
dilation4. The patients
who received hemodialysis during this study were also excluded from this
study.
Mapping and catheter ablation procedure: All procedures were
performed after written informed consent was obtained. Anti-arrhythmic
drugs were withdrawn in all patients at least five half-lives before the
procedure. The anti-hypertensive and –hypercholesterolemic agents
and/or others were continued in patients with hypertension and
dyslipidemia before and after the RFCA. The anti-diabetic agents in
patients with diabetes mellitus were continued before and after the RFCA
but not on the procedural day. The QRS duration and peak deflection
index (PDI)5 were
measured before the RFCA. RFCA was performed under local anesthesia.
After a 50 unit per kilogram administration of heparin was administered,
4 or 5-mm-tip electrode catheters (St. Jude Medical, St. Paul, MN, USA)
were introduced percutaneously into the right ventricle (RV) and
coronary sinus, respectively. A 100 unit per kilogram administration of
heparin was administered following the trans-interatrial septal
puncture, and heparinized saline was additionally infused to maintain
the activated clotting time at 300–350 seconds. After left atrio- and
ventriculography, electro-anatomical mapping during the PVCs was
performed in the coronary sinus and around the MA, left atrium (LA), and
LV near the MA in detail utilizing a 3D mapping system (EnSite NavX /
VelocityTM Cardiac Mapping System, St. Jude Medical,
St. Paul, MN, USA) by a circular mapping catheter
(InquiryTM AFocusIITM Double Loop
Catheter, St. Jude Medical, St. Paul, MN, USA) or high density mapping
catheter (AdvisorTM HD Grid catheter, Abbott,
Plymouth, Minn, USA) during culprit PVCs. If the culprit PVC was not
found during the procedure, an isoproterenol administration and/or
programmed electrical stimulation with a digital stimulator (Cardiac
Stimulator, Nihon Kohden Co., Tokyo, Japan) was performed to induce the
culprit PVC. Then, an open irrigated 3.5-mm-tip ablation catheter
(FlexAbilityTM, St. Jude Medical, St. Paul, MN, USA)
through a steerable introducer (AgilisTM NxT, Abbott,
Plymouth, Minn, USA) was positioned at the MA. An optimal pace map was
defined as a match of all 12 surface leads by comparing the R/S ratio
and subtle notching in the QRS complex during pacing. An identical match
was necessary in at least 11 of 12 leads. Further, based on the findings
of the electro-anatomical mapping and an optimal pace map,
radiofrequency energy was delivered at the site of the unipolar
potentials from the ablation catheter demonstrating a QS pattern and
bipolar potentials from the tip of the ablation catheter preceding the
QRS in the 12-ECG by at least 20 -30 milliseconds during the PVC with a
preset temperature of 43 to 50°C and power limit of 30-35 W. Further,
when the radiofrequency energy was delivered from the coronary sinus, in
order to avoid any complications, (1) heparinized saline was
additionally infused to maintain the activated clotting time at more
than 300 s, (2) a maximum power setting of 20 W for the radiofrequency
energy was chosen, and (3) careful attention to and observation of the
patient was paid during the radiofrequency energy delivery as we
previously reported6.
The radiofrequency energy application was terminated when an abnormal
impedance rise (> 30 Ω) was observed. A successful ablation
was defined as no recurrence and non-inducibility of the culprit PVC
with and without an isoproterenol administration and/or programmed
electrical stimulation for at least 30 minutes after the ablation.
Procedural success was defined as no recurrence of the culprit PVC
within 24 hours after the procedure under electrocardiogram monitoring.
If the recurrence of the culprit PVC was observed, a repeat RFCA was
performed.
Statistical Analysis: The numerical results are expressed in
the text as the mean ± standard deviation. Paired data was compared by a
Fisher’s exact test and Student t tests. The differences between
the continuous variables before and 6 months after the RFCA in each
group, or between the lower and upper groups in each period, were
compared by using a repeated measures analysis of variance followed by a
Bonferroni’s test for multiple comparisons. The correlation between the
two parameters was determined by a simple linear regression analysis.
All analyses were performed with SAS version 9.2 software (SAS
Institute, Cary, NC). A p of < 0.05 was considered to indicate
statistical significance.