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Owens LV, Farber MA, Young ML, Carlin RE, Pallares EC, Passman MA, et al. The value of air plethysmography in predicting clinical outcome after surgical treatment of chronic venous insufficiency. J Vasc Surg 2000; 32: 961–968. 19. Janssen MCH, Wollersheim H, Haenen JH, Van Asten WNJC, Thien TH. Deep venous thrombosis: A prospective 3-month follow-up using duplex scanning and strain-gauge plethysmography. Clin Sci 1998; 94: 651–656. 20. Elford J, Wells I, Cowie J, Hurlock C, Sanders H. Computerized straingauge plethysmography-An alternative method for the detection of lower limb deep venous thrombosis? Clin Radiol 2000; 55: 36–39. 21. Goodacre S, Sampson F, Stevenson M, Wailoo A, Sutton A, Thomas S, et al. Measurement of the clinical and cost-effectiveness of non-invasive diagnostic testing strategies for deep vein thrombosis. Health Technol Assess 2006; 10: 1–5. …continued from page 121 The limitations of this trial mostly address the possibility of a false negative. First, the control group in SODIUM-HF did not consume a lot of salt. That made the difference in salt intake between the groups quite small (< 500 mg). Trial discussant Dr Mary Norine Walsh said that the average American consumes 3 g of sodium daily. The implication is that had the control group been more representative (i.e. more American), the low-sodium diet may have reduced clinical outcomes. This is a reasonable criticism, but it does not reduce the importance of the results. SODIUM-HF did not compare zero advice on sodium with a restricted diet; it tested the standard advice on being careful with sodium against a more restrictive plan. My takeaway is that we don’t have to spend time and energy getting patients to adhere to a super-low-sodium diet. Yes, of course, a patient with heart failure shouldn’t consume 3 g of sodium daily; no one should. Another limitation centres on the statistical power of the trial to detect a difference, if there were one. In deciding how many patients to enrol in a trial, investigators estimate event rates. SODIUM-HF observed fewer events than was originally expected, decreasing the chance of detecting a true difference. Yes, a false negative is possible, but given the p-value of 0.53, it does not seem probable. A third criticism I heard at ACC was that SODIUM-HF enrolled patients who were not sick enough to benefit from a low-sodium diet. For instance, the trial did not require high N-terminal pro-brain natriuretic peptide levels, only a third of enrolled patients had a heart failure admission in the prior year, and most patients were well enough to tolerate good medical therapy. The suggestion is that if the trial had enrolled the ‘right’ patients – those with more severe disease – the low-sodium diet would have worked. SODIUM-HF was a pragmatic trial testing low-sodium diets in six different regions of the world. If you are a proponent of strict sodium restriction, the onus is now on you to show us a group of patients in which it reduces outcomes compared to standard care. Another counter to the ‘wrong’ patient argument turns on the difficulty of making a difference against current medical therapy of heart failure. Years ago, when there were few options for heart failure, a new intervention had a better chance of showing a benefit. But because modern-day therapy drives event rates so low, it’s harder for anything to lower it much more. That is actually good news. Ambitious trial, humble lesson SODIUM-HF is an ambitious trial looking at sodium restriction in different cultures. It showed that under current care, in a typical heart failure cohort, recommending a stricter low-sodium diet versus general advice did not make a difference in outcomes – and might have led to patients having a better perception of their health. The trial advances care because a serious challenge for managing heart failure is getting patients to endure the work of being a patient with heart failure. I see adherence to optimal care as a reservoir of sorts. If you can reduce withdrawals, you have a larger reserve for adherence to things that matter. Yes, of course, we counsel on avoidance of a high-salt diet. But the time spent teaching patients how to cut daily sodium intake to just 1 500 mg can now be used on other things, such as exercise prescriptions or up-titrations of medical therapy. Source: MedicalBrief 2022
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