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.

Hidden information below


Email Address*