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52 Suitability for subcutaneous implantable cardioverter-defibrillator therapy – the impact of different selection policies
  1. Amit Kaura,
  2. Nicholas Sunderland,
  3. Ravi Kamdar,
  4. Ed Petzer,
  5. Francis Murgatroyd,
  6. Para Dhillon,
  7. Paul Scott


Background With subcutaneous ICDs (S-ICD) not offering the same range of pacing therapies as transvenous systems (T-ICD), it is unclear how many ICD recipients may be suitable for a S-ICD. In addition, the benefit from ICD therapy is dependent on non-sudden cardiac death (SCD) risk. The study aims were to [1] establish how many ICD recipients may be suitable for S-ICD implantation based on a range of selection policies, and [2] determine the impact of S-ICD use on the risk of non-SCD.

Methods We performed a retrospective study of all ICD implants over 5 years (2009–2013). We evaluated how widely the S-ICD could be utilised using the following indications: (a) Least liberal use – S-ICD used only in patients with inherited channelopathies and idiopathic ventricular fibrillation; (b) Intermediate use – S-ICD also used for SCD primary prevention in hypertrophic cardiomyopathy; (c) Most liberal use – S-ICD also used for SCD primary prevention in coronary artery disease (CAD) and non-ischaemic dilated cardiomyopathy (DCM) who have a narrow QRS complex (120msec). Given the potential impact of age on the benefit from S-ICDs, we stratified our results by implant age (70, 60 and 50 years). Non-SCD risk was quantified using the MADIT-II risk score (score 0–5, 5 (highest risk)). Mann-Whitney U testing was used to compare risk scores.

Results Over the 5 years, there were 402 implants (79% male, age 70±13 years). After exclusion of patients implanted with a CRT-D device or with a pacing indication, 219 remained for consideration of a S-ICD. Using our definition of least liberal use, intermediate use, and most liberal use, the number of patients considered suitable for a S-ICD was 18 (4.5%), 30 (7.5%) and 77 (19.2%), respectively. Age as a discriminator had a significant impact on the proportion of patients considered suitable for a S-ICD. This was predominantly due to a reduction in the number of patients with CAD and DCM being considered for a prophylactic device. Using the most liberal definition, the number of potential S-ICD candidates dropped from 52 (12.9%) in those 70 years old at implant, to 34 (8.5%) for 60 years, to 20 (5%) using 50 years as the cut-off.

The MADIT-II score was 0.22±0.1, 0.47±0.1 and 0.96±0.1, in the least liberal, intermediate and most liberal use S-ICD groups, respectively. The score was 2.07±0.1, 2.11±0.1 and 2.24±0.1 in the respective T-ICD groups. The mean MADIT-II score in the S-ICD group was significantly lower than that in the respective T-ICD group (p<0.0001, for all three selection policies).

Conclusions While up to one-fifth of patients currently receiving ICDs may be suitable for a S-ICD, this result is dependent on both which patient groups the S-ICD is used in and whether an age cut-off is applied. The cohort of patients suitable for a S-ICD also have a lower risk of non-SCD compared to those receiving conventional T-ICDs.

  • Subcutaneous ICD
  • Indications
  • Mortality

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