- Baseline characteristics of the sample
The majority were male (32 patients, 78.05%) with a mean age on diagnosis of 46.8 ± 17.5 years. Thirty-six patients (87.8%) had definite ARVC/D and the remaining 5 (12.2%) were borderline according to the Task Force criteria modified in 2010.3 The diagnostic criterion for each patient is shown in detail in Table 1.
Regarding clinical presentation, 33 patients were diagnosed based on arrhythmic events (secondary prevention): two patients suffered an aborted SCD and thirty-one had sustained VT with left bundle branch block morphology (22 superior axis and 9 inferior axis). Eight patients had a primary prevention ICD due to severe ventricular involvement (2 biventricular and 6 right ventricular): four were diagnosed from a study for ventricular extrasystole, three during a study for dyspnea with heart failure and other during a familial screening.
A pathogenic or probably pathogenic desmosomal mutation was detected in 26 of 35 patients with a genetic test. Of these mutations, plakophilin–2 was the most frequent with nineteen variations, followed by desmoglein–2 with five and desmoplakin with three.
The mean LVEF was 57.9 ± 9.5%, seven patients (17.1%) had LV involvement and two of them (4.9%) presented severe ventricular dysfunction (LVEF≤35%). Late gadolinium enhancement was present in 12 of the 20 patients who underwent cardiac magnetic resonance. The mean RVEF was 39.4 ± 17.4% measured by resonance and 20 patients suffered severe RV dysfunction (fractional area change ≤17% or RVEF≤35%).
Eighteen patients (43.1%) were athletes before the diagnosis. The exercise was not associated to differences with the indication of the ICD (48.5% in secondary prevention and 25% in primary, p = 0.2), but the athletic patients were younger at the time of diagnosis (33.3 ± 11 years vs 55.2 ±14 years, p<0.001).
All patients underwent beta-blockers from the diagnosis and the follow-up. Fourteen patients (34.14%) had taken amiodarone, none before the first arrhythmic event.
During a mean follow-up of 6.37 ± 4.88 years, 26 patients (63.4%) had at least one appropriate arrhythmic event. The mean time to onset of the first event was 11.42 ± 9.1 months.
A total 364 ventricular arrhythmias with a mean cycle length of 278.5 ± 38.68 ms were recorded and treated. The effectiveness of anti-tachycardia pacing (ATP) was high: 324 (89.01%) reverted with ATP, while the rest required shocks: 40 episodes in 15 patients (36.59%). Nine (21.95%) were admitted for arrhythmic storm and seven (17.07%) required substrate ablation for repetitive ventricular arrhythmias.
Table 2 shows the baseline characteristics at the time of diagnosis and the arrhythmic events in the follow-up according to the indication of the ICD.
Arrhythmic prognosis was worse in secondary prevention than in primary prevention with more affected patients (24p (72.7%) vs 2p (25%); p = 0.02), and also with a nonsignificant tendency to a greater arrhythmic storms (8p (24.2%) vs 1p (12.5%); ns) and ablations (6p (18.2%) vs 1p (12.5%); ns). The lower free survival arrhythmic event is shown in figure 1.
All the appropriate events were by VT in primary prevention. In secondary prevention, the majority were by VT, but 2.3% (8/350 events) were by VF. There were no deaths of arrhythmic origin.
The severe involvement of the RV (fractional area change ≤17% or RVEF ≤35%) was not associated with a lower survival free of arrhythmic events as shown in figure 2.
Five patients suffered inappropriate shocks during follow-up: three due to atrial fibrillation, one due to sinus tachycardia and other due to noise after the fracture of the electrode.
During follow-up, 5 patients (12.2%) were admitted due to heart failure, 2 patients had a heart transplant for refractory heart failure, there were no cardiovascular deaths and 2 died because of non-cardiac causes: one due to pneumonia and the other due to cancer.
Severe RV involvement (fractional area change ≤17% or RVEF ≤35%) was associated with an increased risk of non-arrhythmic events such as heart failure admissions (5p (25%) vs 0%, p = 0.02) and heart transplant (2p (10%) vs 0; ns).
Three patients had complications related with the device: two infections and an electrode fracture.
During follow-up, after the implantation of the ICD, 29 patients (70.73%) presented a cardiovascular event such as ventricular arrhythmias, hospitalization due to heart failure, heart transplantation or cardiovascular death.
Comparing the primary and secondary prevention groups with respect to the risk of any cardiovascular event, there were no differences as shown in figure 3: 24 patients (72.7%) in secondary prevention and 5 patients (62.5%) in primary prevention had cardiovascular event.