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In This Week’s Podcast
For the week ending February 7, 2025, John Mandrola, MD, comments on the following topics: Sugar sweetened beverages (SSB), the epidemiology of driving after an implanted cardioverter-defibrillator (ICD), blood pressure (BP) measurements, and the massive evidence-based medicine (EBM) lesson in endovascular thrombectomy (EVT) for acute stroke.
Sugar-Sweetened Beverages
Multiple studies came out recently focusing on the dangers of SSB — a timely topic before the Super Bowl and its ads.
First is Nature Medicine, which has a big epidemiological study designed to assess the global burden of disease attributable to SSB. Then, two other population studies suggest how difficult it is to create healthcare policy regarding SSB.
First let’s do the Nature Medicine global paper.
The methods are complex and involved hundreds of surveys from nearly 3 million people in 118 countries.
They then conducted risk assessment and concluded that more than 2 million new type 2 diabetes (T2D) cases and about 1 million new cardiovascular disease (CVD) cases could be attributed to SSB.
Mexico, Columbia, and South Africa were most affected. By region, Latin America and the Caribbean had the highest absolute and proportional T2D incidence caused by SSB. Southeast Asia and East Asia had the lowest.
I won’t go on about the details. There are probably hundreds of similar papers. I highlight this topic because I feel there is direct clinical relevance, actionable at the bedside. Namely, one of the main causes of obesity and T2D is liquid calories.
I counsel strongly to reduce or eliminate SSBs — call it low-hanging fruit in the counseling of patients with obesity.
Just stop drinking sugar is such an obvious recommendation. The paper excluded fruit juices, but I think these should be included as well.
Again, we don’t have to become nutritionists. SSBs are obvious places of intervention. And in my experience, admittedly low level of evidence, patients often accept taking SSBs out of their diet.
Finally, while this isn’t a policy podcast, I do like to think about policy interventions to reduce consumption, because clearly less SSB also equals better population health.
Policy interventions are much harder. Some have proposed a soda tax. This seems so obvious, right? Economic principles state that higher prices reduce consumption.
Well. It’s not so easy. SSBs taste good and have amazing marketing.
JAMA Network Open published an observational study from authors at Kaiser who compared California cities with SSB taxes to demographically matched cities without taxes. This was a big data study involving more than a million people.
Their outcome measure was mean body mass index (BMI) and proportion of people with overweight or obesity. They used a difference-in-differences method.
The method relies on comparing four key data points:
The treatment group before the intervention;
The treatment group after the intervention;
The control group before the intervention;
The control group after the intervention.
This study involved a time period of about 4 to 6 years before and after the tax.
The main finding was that overall, there was no difference in BMI in the taxed cities compared with controls.
When looking at subgroups there were a few small signals. One was adults age 20 to 39 years and the other was the group in Berkeley, California. Both groups had additive differences in mean BMI of about -0.16. Both subgroups reached statistical significance.
But to me, the overall study was sobering. And even if you think the subgroup findings were significant the absolute change was tiny.
The Lancet Regional Health published the second study, looking at electronic health record data to find before and after changes in weight from a 2017 SSB tax in Philadelphia, Pennsylvania.
The Philly tax was larger than in California. It was 1.5 cents per ounce. This resulted in about a 30% increase in the beverage cost, which led to a 20% to 40% reduction in SSB consumption.
This was another big data study of hundreds of thousands of people. The main outcome measure was BMI.
Again, it was a quasi-experimental design with an active arm, people in Philly, vs a control, cities without SSB taxes.
The groups were different. For instance, 82% of the control arm was white vs only 39% of the active arm in Philly.
So, the first step was to make statistical adjustments to get baseline characteristics closer, which they could do, at least on paper.
They used two samples. One a cross-sectional sample of 2 million people and the other longitudinal sample following people before and after. Yes, I know, it’s complicated.
Let me summarize: There was little effect on BMI. One sample was non-significant pre and post change. One sample was statistically significant, but the mean reduction in BMI was tiny.
The authors call it “limited evidence” of effect. And they call for replication of these results.
Comments. Taken together, the two papers looking at before and after show modest to no effects on important outcomes, such as BMI.
I think we should expect that. I mean, common sense holds that there are many causal factors acting on obesity, not just SSB intake. There is food intake and exercise.
I am not even sure we should hold SSB tax policy to the endpoint of average BMI of the population.
The message though is that turning American cities into Copenhagen is not going to be easy.
Cardiometabolic health of populations won’t come from doctors advocating for healthy behaviors. We should do that, obviously, but making Americans healthier will need to come from big policy changes at a macro level. This won’t be easy.
We shall see if the new public health leadership has any success. There are big corporations and lots of money working against cardiometabolic health, so I am pessimistic.
Driving With an Implanted Cardioverter-Defibrillator
JACC-Electrophysiology has published an attempt to bring some empiricism to our decrees on driving after an ICD. It’s a fun paper. I learned a lot by studying it.
There are guideline recommendations on this, but very little robust data. How could there be, right? Crashes are uncommon events and causal factors are many.
Well, the British Columbia (BC) electrophysiology (EP) group, first author, John Staples, sought to find some evidence to inform driving recommendations. I am going to tell you about the study, then I will give you a simple hard and fast rule that I have decided on. It’s nearly foolproof and I think you might like it.
The study is neat because they used two methods to seek causation. First, they had population level data of all drivers involved in a serious crash in BC from 1997 to 2019. Exposure, obviously, was receiving an ICD implant in the 6 months before the crash.
One method was a case crossover design, and the other was a responsibility design to account for road exposure. I will speak about the design, then give the results. Each of the designs requires adjustments for potential confounding variables.
In the case-crossover design, each person serves as their own control. You compare the exposure, the ICD implant during a “case” period when the crash occurred, with exposure during control periods when no crash occurred.
The case period is the time right before, and control period is earlier time periods. Then they calculate the odds ratio of ICD implant in the case period vs control period.
Here are the results of this design:
In the case-crossover analysis of crash-involved ICD recipients. ICD implantation occurred in 6.4% precrash intervals and in 7.4% of control intervals, adjusted odds ratio [aOR]: 0.86; 95% confidence interval (CI): 0.71 to 1.03; P = 0.11, which suggests no temporal association.
Now to the responsibility analysis which started by sorting responsibility using an integer score. They then were able to do a correlation to evaluate the association between crash responsibility and nonresponsibility and recent ICD implant.
Here is the result of the main responsibility analysis. Note the numbers in the ratios:
14 of 22 drivers with recent ICD implantation and approximately 500,000 of a million drivers without recent ICD implantation were deemed responsible for their crash. The crude proportion responsible: 64% vs 51%; aOR: 2.20; 95% CI: 0.91 to 5.30; P = 0.08.
This suggests no association between ICD implantation and crash responsibility.
The problem, of course, was that only 22 of a million drivers with determinate responsibility had an ICD in the 6 months before the crash, so statistical power is low.
Comments. Before I say anything about these two methods of sorting causality, let me tell you about a paper from the same BC group published in the journal HEART last year, this study also attempted to sort out ICD and driving. Here they did a much simpler analysis using the same BC database.
They looked at people with a first ICD implant over a 20-year period and age- and sex-matched them to three control patients. Then they looked at involvement as a driver in a crash.
They found that having an ICD implant was associated with a lower risk of subsequent crash. Statistically significant, hazard ratio (HR) 0.71. The results held up even for secondary prevention ICD; that is, ICDs implanted for ventricular tachycardia.
The rub in this study was that relative to controls, ICD patients had more traffic violations in the 3 years prior to ICD implantation but fewer violations in the 6 months after implantation, suggesting individuals reduced their road exposure (hours or miles driven per week) or drove more conservatively after ICD implantation.
The more recent study with the case-crossover design and responsibility analysis is more robust as it gets around the driving exposure weakness. But there are still limitations. I have already mentioned power because both car crashes and ICD implants are rare events. But there is also missing data about ICD indication and specific data about crashes, like distracted driving.
That said, taken together, these three methods of assessing causality with this database do not provide even a shred of evidence that ICD implantation affects crash risk in the 6 months after implant.
I love the paper. I learned a lot about causal methods. It confirms what I have seen in my 29 years of practice: namely that patients with ICDs are not a danger.
So, I will tell you the Mandrola rule for driving by any cardiac patient.
Whenever you think about restricting a grown adult with heart disease, the proper comparison is to a 16-year-old who just got his or her license.
For this reason, I almost never suggest a driving restriction after more than a week (so that incisions can heal).
Blood Pressure Measurements and Simple Randomized Controlled Trials
Professor Ahmed Bendary from Egypt changed my mind about covering this study. I wasn’t going to cover this Annals of Internal Medicine paper comparing BP measures in a quiet office vs a noisy public space.
I looked at it and thought, no, that’s not notable. But Ahmed messaged me and said he liked these trials as much as more complicated regulatory trials.
So, I took another look and I agree with him. Why? Because we are told that BPs have to be done in quiet offices — perfectly controlled. This idea limits the use of screening BP.
This very simple but elegant study from Johns Hopkins in Baltimore set out to test the effect of noise and public environment on BP readings.
About 100 patients were recruited from screening campaigns. Each patient is their own comparison. Randomization assigned the order in which they had triplicate BP measures in each of three settings: office quiet; public noisy, and public with ear plugs.
A note on patients — mean age was 56 years; 84% were self-reported Black; nearly half were female.
The average noise level in public was loud, at 76 db.
The results: There were no clinically important differences overall or in subgroups; less than 2 mmHg.
Comments. This study suggests that public spaces are reasonable places to check BP. Sort of. It’s a small sample; patients are motivated; researchers are motivated to measure BP properly. But still, I don’t see the downside of advancing more BP screening — especially in underserved populations.
The other thing to say is that I love efforts like this. No one gets rich because they got a new drug across a regulatory bar by using a dubious noninferiority design or even more dubious, a composite primary endpoint. And these researchers aren’t going to get a Nobel Prize.
But the effort in doing a proper trial is great for them, and great for readers of theliterature. If I have said this once I’ve said it a hundred times: if you believe something is true in Medicine, subject it to randomization.
A Big Shake-up in Interventional Stroke Care
Two trials published in NEJM suggest there is a limit to the benefits of EVT for acute stroke.
There are a lot of details and nuance here, and I am not a stroke neurologist, so I will focus on the EBM-lessons, including one huge one. Dr J Mocco wrote an excellent editorial in NEJM, on which I will lean heavily. Notably, it was candid and stark, and this is remarkable.
Stroke thrombectomy got its start in 2015, with early large-vessel occlusion. Then there were extended window trials in 2018, and then large core trials in 2023.
The question I have seen come up — often in the neuro-radiology reading room, which I visit often — is what to do with medium and distal vessel occlusions, beyond the M1 segment of the middle cerebral artery or in the basilar artery.
Two trials inform that issue. One was ESCAPE -MeVO (for medium vessel occlusion).
The trial included 530 patients with acute ischemic stroke due to MeVO who presented within 12 hours of symptoms.
Primary outcome was modified Rankin score (mRS; 0 to 6; 0 is normal, 6 is dead) reported as the percent within 0 to 1. Randomization was 1:1.
Patients with an mRS of 0 to 1 occurred in 42% of those in the EVT vs 43% in the usual care group. So non-significant.
Mortality, however, was higher in the EVT group (13.3% vs 8.4%; HR 1.82 with CI 1.06 to 3.12).
Intracerebral hemorrhage (ICH) was also 2.5 times more common in the EVT group (5.4% vs 2.2%).
Comments. Obviously, EVT therapy does not work in this population. No benefit in efficacy, higher mortality, and greater risk of ICH.
The authors offer reasons — delay to recanalization because everything about smaller vessels is harder, including successful opening of the artery, and even decision-making, more complications, such as more pneumonias, possibly because of general anesthesia, 41% vs less than 10% in the older trials.
Let me tell you about the second NEJM trial, then I will focus on the main EBM point.
The DISTAL Trial. Similar story: about 540 patients, now with isolated occlusion of medium or distal vessels. Conducted in Europe. EVT vs standard care.
Primary outcome was the level of disability at 90 days by mRS. An added feature was its pragmatic design with broad inclusion criteria and allowance for doctors to choose what they felt was the best approach to intervention.
The predominant occlusion locations were the M2 segment (in 44.0%), M3 segment (in 27%), P2 segment (in 13%), and P1 segment (in 5%).
The main results:
No difference in mRS. OR for improved score was 0.9 but CI went from 0.67 to 1.22 and P = 0.50.
Mortality was numerically higher in the EVT group (15.5% vs 14.0%).
ICH was also higher, 5.9% vs 2.6%.
The conclusion is also obvious. EVT offers no benefit in this group of patients.
A discussion point was that successful reperfusion was only 72%, lower than reported in trials of stroke with large-vessel occlusions.
Comments on Both Studies. Whenever trials fail to show an improvement, there is a discussion among proponents that the best patients were not included. Same here. Both trials enrolled patients older than in previous trials, and that may be because younger patients with medium or distal vessel occlusions who were more apt to benefit were treated not randomly assigned.
I would note here is that this is the same argument used to avoid accepting the COURAGE trial of adding percutaneous coronary intervention to medical therapy.
When COURAGE shocked the cardiology world because it showed no benefit, stent proponents said that docs only put patients in COURAGE if they felt the disease was mild, and they treated the worst angiograms.
Well, that was wrong, because in ISCHEMIA, which yielded similar results, randomization was before the angiogram.
I don’t know about stroke care, but sadly, neither ESCAPE-MeVO nor DISTAL tell us the number screened who were not randomly assigned. This is such an important data point. More and more, I see it excluded, but for external validity or clinical translation, it is an important factor. The classic example here was CASTLE AF which screened 3000 to enroll 300.
The main teaching point is this: EVT for medium and distal vessel disease was being widely performed. It was accepted practice.
J Mocco pointed out in his editorial that the number of publications for EVT for medium vessels had increased from 8 in 2020 to 99 in 2024. And it was the same pattern for EVT for distal vessels. He also notes that nearly all those publications noted benefit from EVT.
What were these publications? Two of the most dangerous kinds of publications — observational studies and subgroup analyses from RCTs, including meta-analyses.
The expansion of medium and distal vessel EVT was supported by an amalgam of optimistic interventional doctors powered by non-RCT-level evidence. I pulled one such study: A meta-analysis of pooled data from the HERMES trials. It had only 100 patients and the benefit had a CI that went from 1 to 5, suggestive of low power.
So, the lesson here is:
Be skeptical about subgroups. We should favor the main finding from trials as this is what the trial is powered for. Never forget the ISIS-2 lesson where post-MI aspirin effect varied by astrological sign.
Remember that we call subgroup analyses “hypothesis-generating” not actionable because that is indeed what they are for. Here, the hypothesis that EVT would work in medium or distal vessels was proven wrong.
Pay no heed to non-random comparisons, as surely in the setting of interventional therapies they are biased beyond belief by selection.
All doctors can learn from the EVT story laid out in this week’s NEJM. Once again, the main results of proper RCTs show the way forward.
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