• Comparative Effectiveness at work (and a power dig)

    A faithful reader of the blog thought I might feel better if I focused on some actual clinical trials. He’s right. From JAMA, “Association of Single- vs Dual-Chamber ICDs With Mortality, Readmissions, and Complications Among Patients Receiving an ICD for Primary Prevention“:

    Importance  Randomized trials of implantable cardioverter-defibrillators (ICDs) for primary prevention predominantly used single-chamber devices. In clinical practice, patients often receive dual-chamber ICDs, even without clear indications for pacing. The outcomes of dual- vs single-chamber devices are uncertain.

    Objective  To compare outcomes of single- and dual-chamber ICDs for primary prevention of sudden cardiac death.

    Design, Setting, and Participants  Retrospective cohort study of admissions in the National Cardiovascular Data Registry’s (NCDR) ICD registry from 2006-2009 that could be linked to Centers for Medicare & Medicaid Services fee-for-service Medicare claims data. Patients were included if they received an ICD for primary prevention and did not have a documented indication for pacing.

    Main Outcomes and Measures  Adjusted risks of 1-year mortality, all-cause readmission, heart failure readmission, and device-related complications within 90 days were estimated with propensity-score matching based on patient, clinician, and hospital factors.

    Here’s the deal. Most of the research on implanted defibrillators has been conducted on what are called single-chamber devices. But then came along dual chamber devices, which have some theoretical benefits. However, most of those are for a select population. But this being the US and all, soon two-thirds of all ICDs being put in were dual-chambered, and about 60% of those lacked any documented reason for using the more complicated device. Oh – the dual chambered devices cost more, too.

    This was a comparative effectiveness study of people who received a single or dual chamber ICD from 2006-2009. What did they find? Of the 32,034 patients, 38% got a single-chamber device and 62%  got a dual-chamber device. After controlling for come clinical issues, those who got a single-chamber ICD had fewer complications than those who got a dual-chamber ICD (3.51% vs 4.72%). In contrast, those with the single-chamber device did not see higher 1-year mortality (9.85% vs 9.77%), 1-year all-cause hospitalization (43.86% vs 44.83%), or hospitalization for heart failure ( 14.73% vs 15.38%).

    In other words, the dual-chamber device offers no improvements in mortality, all-cause hospitalization, or heart failure hospitalization. This held true even when looking at sub-groups of age, sex, or the presence of renal dysfunction. BUT, dual-chamber devices did have a significantly higher risk of complications.

    And they cost more. This is how comparative effectiveness can help. But only if we act on it.


    Sidebar: I quote from the methods: “Power calculations were not performed because the study was retrospective with a fixed sample size. The precision of the estimates for the hazard ratios between single- and dual-chamber ICDs is reflected in the confidence intervals for these estimates.” Please recognize, however, that this was a study of over 32,000 patients – all of whom were appropriately analyzed. All got one of the therapies, and all could have had the outcomes. They were able, therefore, to detect a clinical difference in complications of 3.51% and 4.72% as statistically significant. The difference in hospitalization for heart failure (14.73% vs. 15.38%) was not statistically significant.

    Yet in Oregon, we are expected to believe that the application of insurance to 56 or 57 people with documented hypertension should tell us something significant.