A retrospective study of HCM patients with implantable defibrillators conducted at eight centers worldwide  has demonstrated that ICDs are not only lifesaving, the shocks they generate are not harmful to those in whom they are implanted.

The study looked at 486 patients with HCM with an ICD implanted for either primary or secondary cardiac arrest prevention.  Of the 486 patients, 94 (19%) experienced at least one appropriate shock from their ICDs.  44 of those who had been shocked had experienced one or more shocks over the period of the study, including 6 patients who had at least 3 shocks over a 24 hour period.  Inappropriate shocks occurred in 96 patients (20%).

Despite the shocks, appropriate or not, at the end of the follow-up period the ICD discharges did not appear to cause the patients to suffer from increased heart failure or sudden cardiac arrest. Furthermore, their general health and well-being were good:  they did not suffer from significant degrees of anxiety and depression.