All studies, great and small

Talk about extremes. Two studies published recently illustrate the range of sample sizes and what can be learned from both small clinical trials and large observational studies.

Mark A. Hlatky, MD, of Stanford University School of Medicine in Stanford, Calif., and colleagues used a comparative observational study to expand the scope of knowledge beyond findings in clinical trials that compared multivessel PCI and multivessel CABG. Their motivation centered on the beliefs that trials enroll a selected patient population that may differ from real-world practice and sometimes lack sufficient power to conduct subgroup analyses.

They used Medicare claims data to identify 194,223 eligible patients with multivessel CABG and 57,330 with multivessel PCI and matched 10,080 patient pairs for the analysis. Hlatky et al found that CABG had a slight mortality edge over PCI for the “average” patient.

But in an era of personalized care, physicians should consider their results on patient characteristics and treatment effects. They reported that patients with diabetes, heart failure, peripheral artery disease or those who used tobacco had a survival advantage from CABG while patients without those characteristics were predicted to have better survival after PCI.

The results were published online April 23 in the Annals of Internal Medicine.

On the other side of the spectrum, Birgit Assmus, MD, of the Institute of Cardiovascular Regeneration at Goethe University in Frankfurt, Germany, and colleagues offered the latest in their research on the use of cardiac shock waves and intracoronary administration of autologous bone marrow-derived mononuclear cells (BMCs) to treat patients with chronic postinfarction heart failure. Their study appeared in the April 17 issue of the Journal of the American Medical Association.

In a double-blind randomized controlled clinical trial called CELLWAVE, they enrolled 103 patients who first underwent randomization to receive low-dose, high-dose or a sham dose of shock-wave pretreatment followed by a second randomization in the low-dose and high-dose groups of BMCs or placebo. Everyone in the sham group received BMCs.

They found at four months a significant improvement in left ventricular ejection fraction in patients who received a low-dose or high-dose pretreatment plus BMCs compared with the other groups. But these findings are based on a small number of patients. The results may justify a larger randomized clinical trial but as yet lack enough weight to sway clinical practice.

Both studies deserve credit for advancing knowledge, one peg at a time, toward the ultimate goal: better patient care.

Please feel free to share recent findings that you see as potentially changing practice, either now or in the future.

Candace Stuart

Cardiovascular Business, editor