The Half-Life of Medical Knowledge

Blog by: Neil Sanghvi, M.D., F.A.C.C., F.H.R.S. I recently attended a presentation on minimizing ICD discharges. I was particularly struck by a comment from the presenter — Dr. Michael Gold from the Medical University of South Carolina. To paraphrase: The half-life of medical knowledge is seven years. What an insightful thought. The rate of medical knowledge is increasing exponentially with advances in research techniques, technology, and global connectedness. This newly accumulated knowledge is as capable of confirming current practice as it is to contradict accepted doctrine. Fifty percent of what we believe is correct today may be proven obsolete in coming years. For example, take beta blockers and congestive heart failure: up until the mid 1970s, beta blockers were completely contraindicated due to the belief that their negative inotropic property would result in worsening heart failure and death. To suggest giving a heart failure patient a beta blocker prior to the 1970s would have been considered malpractice. It wasn't until 1975 that Waagstein et al(1) described the successful administration of chronic beta blockers in heart failure patients. Today, all patients with systolic dysfunction should be considered for beta blockers — a core measure of good clinical practice. Moreover, I once thought that beta blocker therapy for remote post-MI patients or patients with known coronary artery disease (CAD) was sacred — a mainstay of therapy that would prevent future myocardial infarctions and extend longevity. Well, it turns out that this too may not be true. Recently, an observational study of 45,000 patients was reported in the October 2012 issue of the Journal of the American Medical Association.(2) Using propensity score matching, the authors discovered that beta blockers conferred no benefit in preventing recurrent myocardial infarctions, strokes, or mortality in patients with stable CAD including remote history of MI, known CAD, or 3+ risk factors for CAD with normal ventricular function and no current angina. Once again, a principle of cardiovascular medicine is being challenged. I personally do not know if this means that these patients do not need beta blockers at all. However, I will likely think twice before insisting compliance in these stable CAD patients at the cost of side effects and intolerance. Walk away with this: medical knowledge is ever changing. Stay informed, know the limitations of current evidence, and finally ... be prepared to potentially unlearn 50% of what you know! (1) Waagstein F, Hjalmmarson A, Varnauskas E, Wallentin I. Effect of chronic beta-adrenergic receptor blockade in congestive cardiomyopathy. Br Heart J. 1975;37:1022. (2) Bangalore S, et al, for the REACH Registry Investigators. β-blocker use and clinical outcomes in stable outpatients with and without coronary artery disease. JAMA. 2012;308:1340. For more information on Dr. Sanghvi, please visit: