Tuesday 26 June 2018

Placebo pacemakers

Once inserted, heart pacemakers can be turned off and on remotely. This makes them well suited for a placebo study, and that’s what these researchers did in the late 1990’s, with surprising results. It is a shame that no one else has done it since.

In a study published in 1999 (here), researchers from the European Society of Cardiology placed pacemakers in people with a certain form of heart disease (hypertrophic obstructive cardiomyopathy). In 40 patients (selected randomly) the pacemaker was set to ‘inactive’ mode (basically turned off). In 41 patients, it was ‘active’ (working normally). 
Patients were blinded (they didn’t know what they got) and they could change from their group to the other group if they thought they weren’t getting better. Interestingly, 3 patients from the placebo (inactive) group did just that, whereas none in the active group asked to swap.

The patients who received the active pacemaker did much better than the placebo patients in terms of cardiac function, exercise duration and the pressure gradient measured in the heart (the amount of left ventricular obstruction). No surprises there.

However, there are two important findings from this study. Firstly, the placebo patients also significantly improved their cardiac pressure gradient (but not as much as the active group). This is interesting because this is something that patients can’t feel or fake. It’s also important, because the difference in the improvement between the two groups tells us the true effect of the treatment (the effect of pacing, beyond the effect of just inserting a pacemaker). This kind of powerful information is only available in placebo trials.

Secondly, patients in the placebo group significantly improved in many of the quality of life measures (like chest pain, shortness of breath, palpitations, quality of sleep), sometimes with a greater improvement than the active group (and sometimes vice versa).

The bottom line

This study tells us a lot. It shows us that placebo treatments can be associated with significant improvements, not only in subjective outcomes like chest pain, but in ‘hard’ outcomes like cardiac pressure gradients. It is also important because by subtracting the amount of improvement in the placebo group from the amount of improvement in the active group, the researchers were able to determine the ‘true’ effect (the effect beyond placebo) of their treatment, which shows us the power of placebo studies. It is a shame that no similar pacemaker studies have been done this century.

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