Four hundred forty consecutive patients with >1,000 PVCs of LBBB morphology (minor diagnostic criterion of ARVC/D) and no other pre-existing criteria were prospectively enrolled.
CMR examination was performed using a 1.5-T Signa CVi scanner (GE,
Milwaukee,
Wisconsin) with a cardiac phased-array 8-channel coil.
For the assessment of regional wall motion (WM) and left ventricular (LV) and RV volumes and mass,
cine images were used with a steady-state free precession (Fast Imaging Employing Steady-State Acquisition [FIESTA]) pulse sequence in short-axis views (from atrioventricular valve plane to the apex,
8-mm slice thickness,
no gap) and in para-axial views (from diaphragm to the entire outflow tract,
5-mm slice thickness,
no gap).
RV WM,
signal abnormalities,
dilation,
and reduced ejection fraction evaluated by CMR were considered imaging criteria of ARVC/D.
The following acquisition parameters were applied: 30 phases,
10 to 25 views per segment depending on heart rate,
NEX 1,
FOV 40 cm,
a matrix of 224x224,
a 45° flip angle,
TR/TE equal to 3.5/1.5,
and a bandwidth of 125 kHz.
For the evaluation of fat infiltration,
a fast spin echo image was acquired in the same short-axis view (8-mm slice thickness,
no gap) and para-axial view (5-mm slice thickness,
no gap) with the following parameters: NEX 1,
FOV 40 cm,
matrix of 256x256,
a 90° flip angle,
TR/TE equal to 1,791/41.5,
and a bandwidth of 62.5 kHz.
Fast spin echo images were also reacquired using a fat saturation pulse to selectively null signals from fat.
Post-processing. Using dedicated software (Mass Analysis,
MEDIS,
Leiden,
the Netherlands),
the following functional parameters were obtained from the short-axis images: RV and LV end-diastolic volume index,
RV and LV end-systolic volume indexes,
LV mass index,
and RV and LV ejection fraction.
The RV and follow-up was performed evaluating an index composite endpoint of 3 cardiac events: cardiac death,
resuscitated cardiac arrest,
and appropriate implantable cardiac-defibrillator shock.
RV WM was evaluated by 2 independent expert investigators from the short-axis and para-axial cine views and were classified as normal WM,
minor WM abnormalities (hypokinetic segment),
or major WM abnormalities (akinetic or bulging segment).
(Fig.1)
Similarly,
fast spin echo images with and without fat saturation were evaluated by 2 independent expert investigators,
and the signal from the RV wall was classified as follows: 1) normal signal if there was no evidence of hyperintense myocardium with infiltrative characteristics; or 2) signal alteration (myocardial area hyperintense in fast spin echo images and hypointense in fat saturation fast spin echo images) diffuse (more than 1 segment) if focal,
but infiltrating or associated with wall thinning.
(Fig.2).
According to the Task Force diagnostic criteria for ARVC/D,
CMR findings accepted as major diagnostic criteria are severe WM abnormalities (akinesia,
bulging) and severe RV dilation with dysfunction (defined as mean end-diastolic volume index >4 SD above the mean reference value,
and RV ejection fraction lower than 40%).
Minor CMR diagnostic criteria of ARVC/D are: mild WM abnormalities (hypokinesia),
mild RV dilation defined as mean end-diastolic volume index <2 and >4 SD about the mean of the reference,
or RV ejection fraction between 40% and 50%).
Considering that all patients were positive for only a minor criterion (>1,000 PVCs in 24h with LBBB morphology and inferior axis),
the diagnosis of ARVC/D was based on the evidences of major or minor CMR criteria for ARVC/D.
Therefore,
on the basis of the presence or absence of these criteria,
subjects were clustered in 2 groups: no-RVA group (patients without RV abnormalities found by CMR) and RVA group (patients with the presence of 1 or more RV abnormalities).
RVA group was also subdivided into 2 groups: RVA-1 (patients with only 1 RV abnormality) and RVA-2 (patients with 2 or more RV abnormalities).
Follow-up was performed in all patients for a mean of 1,348±120 days after the CMR examination.
Comparisons between groups were made with the chi-square test with Yates correction and t test or Mann-Whitney U test,
where appropriate.
Logistic regression analysis was carried out for the hazard risk evaluation of VT at 24-h ECG Holter monitoring as the dependent variable and age,
sex,
and the different groups of patients with any RV wall abnormality.
Statistical analyses were performed using SPSS version 13 (SPSS Inc.,
Chicago,
Illinois),
and a p value <0.05 was considered significant.