Coronary artery bypass surgery during mobilization (freeing) of the right coronary artery from its surrounding tissue, adipose tissue (yellow). The tube visible at the bottom is the aortic cannula (returns blood from the HLM). The tube above it (obscured by the surgeon on the right) is the venous cannula (receives blood from the body). The patient’s heart is stopped and the aorta is cross-clamped. The patient’s head (not seen) is at the bottom.
Medscape.com, by Shelley Wood, May 4, 2011 (Chicago, Illinois) — Rates of (PCI)Percutaneous coronary intervention, have stayed stable between 2001 and 2008, while the annual rate of CABG procedures declined by 38%, a new analysis shows . Authors of the study, published in the May 4, 2011 issue of the Journal of the American Medical Association, say that the findings likely speak to “a sizable shift in cardiovascular clinical practice patterns away from surgical treatment toward percutaneous, catheter-based interventions.”
Whether that shift is good or bad and just who is actually being “shifted” and why remain some of the most contentious questions in cardiovascular medicine.
“The ratio of PCI to CABG used to be 2 to 1 and now it’s 3 to 1,” Dr Peter Groeneveld (Philadelphia Veterans Affairs Medical Center, PA), senior author on the study, told heartwire . “That’s a bit of a concern, because we know from the SYNTAX trial that CABG is the better alternative for patients with triple-vessel and left main disease.”
But Dr Jeffrey Moses (Columbia University, New York, NY), an interventional cardiologist, commenting on the study for heartwire , calls this interpretation of SYNTAX “astonishing” and “disingenuous,” saying, “I don’t think these guys have been going to the same meetings that I have!”
He points out that based on SYNTAX and other studies, PCI is now considered by both US and European guidelines as a suitable alternative for lower-risk patients with left main disease and three-vessel disease.
“Contrary to what the authors are saying, the evidence does seem to be moving practice in a direction that I think they’d consider positive. If you look at this logically, the patients who were previously referred for CABG did not go away–they did not get treated medically, they almost undoubtedly got a different form of revascularization–ie, PCI. So with the additional numbers of PCIs from the formerly CABG group, the fact that total PCI didn’t go up indicates that there is another segment who was getting PCI before who is now being treated medically.”
Also commenting on the analysis for heartwire , cardiovascular surgeon Dr Chris Feindel (University of Toronto, ON) said that that the shift cannot fully be explained by patients getting PCI, appropriately, who in the past were suitable only for CABG. He believes some are not hearing the surgeon’s point of view as to what treatment is best. If they were, he says, “I think you’d probably see CABG rates being fairly flat, possibly increasing somewhat in three-vessel disease, and I think you’d see multivessel-disease angioplasty falling to some degree. I don’t know how much, but I think it would be a significant amount.”
A SYNTAX Refresher
As previously reported by heartwire , the three-year results from SYNTAX, which compared PCI and CABG in patients with left main coronary disease and/or three-vessel disease, showed rates of the primary end point (major adverse cardiac and cerebral events) to be lower in CABG patients than in patients treated with a Taxus paclitaxel-eluting stent. That difference was driven largely by repeat procedures in the PCI group. Rates of death/stroke/MI were nearly identical in the two groups overall. When patients were divided into tertiles based on baseline SYTAX score, reflecting disease complexity, those in the lowest-risk tertile did well with both procedures out to three years; those in the middle and highest tertiles, however, had worse outcomes if treated with PCI.
CABG Drops; PCI Stays the Same
Authors of the new analysis, Dr Andrew J Epstein and colleagues, used inpatient data from the Healthcare Cost and Utilization Project, supplemented with Medicare outpatient claims. They noted a 15% overall decrease in rates of coronary revascularization procedures, mostly driven by a striking drop in CABG procedures, from 1742 to 1081 per million adults. By contrast, PCI rates held steady, from 3827 per million adults in 2001–2002 to 3667 in 2007–2008.
Epstein et al acknowledge that they couldn’t, in their data, distinguish patients who were suitable for both revascularization procedures from those best suited to either one procedure over the other. It is possible, they say, that patients whose care “shifted” to CABG “included many patients with less compelling clinical indications for CABG surgery over PCI.”
“Who is appropriate for CABG and who is appropriate for PCI–we have these discussions all the time and the data are analyzed and subanalyzed, and that’s a matter of uncertainty in many anatomic and clinical circumstances,” Moses observed. “But the fact that the overall rates of revascularization are going down in the face of overall outcomes of death and MI improving in the country I would take as an overall positive message.”
Groeneveld, in response, says he “can’t rule out” the possibility that all of the migration from CABG to PCI consists of patients determined to be newly suitable, based on the evidence.
“The problem is that it’s a little hard to believe that that’s the whole story, that we’ve just been treating patients more appropriately, and that explains this huge decline. I would buy that if it were a 5% to 10% decline in CABG or a slightly greater decline in CABG compared with PCI. If we’re talking about a fraction of SYNTAX patients who have triple-vessel disease or left main but are at low risk–that’s still a low percentage of the overall CAD population. We’re probably talking about 5000 or 10 000 patients a year, not hundreds of thousands of patients a year.”
His “hunch” he continued, is that with interventionalists as the gatekeepers, “CABG is a more difficult destination to reach.”
Feindel, likewise, referred to as-yet-unpublished data looking at varying CABG:PCI ratios across hospitals in Ontario, showing that hospital culture is a key driver.
“We’ve seen that ratio of PCI to CABG from center to center can range from 1.4 up to 4.4, which is pretty dramatic,” Feindel said. “One has to wonder what’s going on, and is it financial incentives? Medicine is very much a supply-driven economy in the sense that if you have more operators, sometimes I think more things get done whether we like it or not.”
In fact, in Epstein et al’s analysis, the number of hospitals providing both types of revascularization procedures increased, although more so for PCI (26%) than for CABG (12%). This, at least for CABG procedures, had the effect of driving down case volumes for hospitals by 28% and more than doubling the number of hospitals performing less than 100 CABG procedures per year (11% in 2001 compared with 26% in 2008).
“Usually you would start closing coronary surgery programs if you were faced with declining volumes; instead we are seeing the opposite phenomenon, and that’s worrisome if in fact hospitals need to do a minimum volume of CABGs to be good at it, and there’s reason to think that’s probably true,” Groeneveld said.
Stoking the Flames
Anticipating all of the discussion that the JAMA paper will stoke anew, Moses observed: “These articles tend to get politicized when the message, I think, is pretty interesting and a positive one for the healthcare system.”
Groeneveld, for his part, acknowledged that there is no information on procedure appropriateness in his paper or on any clinical outcomes. In fact, the data set they used can’t be linked to subsequent patient events. What he hopes the analysis will do, he says, is prompt discussion.
“I hope that this paper does kind of compel people practicing in clinical medicine as well as patients in this arena to think hard about how patients eventually wind up getting the treatment they get, and I think SYNTAX does the same thing: it makes us wonder whether we are really getting patients to the right kind of treatment.”
Study Shows Heart Attacks in the Morning Are More Serious Than Those in Overnight Hours
Reviewed by Laura J. Martin, MD
WebMD,com Health News, May 3, 2011, by Salynn Boyles — The most common time of day for heart attacks is the morning, and now new research suggests that morning heart attacks are also the most serious.
Heart attacks occurring between 6 a.m. and noon were associated with the most the damage in the study, reported Wednesday in the journal Heart.
Researchers reviewed data from more than 800 heart attack patients treated at a hospital cardiac center in Madrid, Spain, between 2003 and 2009. Heart attacks that occurred in the morning hours were associated with about 20% more dead heart tissue.
The study is the first to link circadian fluctuations to heart attack severity in humans. If confirmed, the findings could affect treatment and research, study researcher Borja Ibanez, MD, PhD, tells WebMD.
Ibanez is a senior investigator for Spain’s National Center for Cardiovascular Research and an interventional cardiologist at Madrid’s Hospital Clinico San Carlos.
The association was quite robust,” he says. “In our study, events that took place in the morning were associated with more damage.”
Morning Heart Attacks vs. Overnight Heart Attacks
The patients included in the study all had a type of heart attack caused by blockages in the arteries.
Heart muscle damage was calculated by examining peak concentrations of creatine kinase (CK) and troponin-I (TnI), key enzymes released in response to muscle injury.
Heart attack timing was divided into four six-hour time periods over 24 hours.
As expected, the largest number of heart attacks occurred in the morning hours, with 269 patients needing treatment between 6 a.m. and noon. The fewest heart attacks occurred between midnight and 6 a.m., with 141 patients needing treatment.
Patients whose heart attacks occurred between 6 a.m. and noon had 21% higher CK and TnI levels than patients whose heart attacks occurred between midnight and 6 a.m.
Ibanez says the recognition that morning heart attacks may be more severe could have important implications for their treatment.
Early treatment with clot-busting drugs and angioplasty can prevent or limit damage to the heart muscle, but most cardiac catheterization labs are not fully staffed in the early morning hours.
Research suggests that around-the-clock access to a catheterization lab reduces treatment delays, he says.
“It could be that having one or two cath labs open in a city could have a significant impact on outcomes,” Ibanez says.
Searching for Answers
It is not entirely clear why heart attacks are more common in the morning hours, but a recent study from Harvard Medical School suggests that elevated blood pressure does not explain the link.
High blood pressure is a major risk factor for heart attack and stroke, but Harvard researcher Steven A. Shea, PhD, and colleagues found that study participants actually had their lowest blood pressure readings of the day in the late morning hours.
Ibanez’s own research suggests that fluctuations in hormones receptors that bind adrenaline over the course of the day may explain the circadian influence on heart attacks.
“If we are able to identify protective proteins that are elevated later in the day, we might be able to develop drugs to replicate this protection.”
WebMD.com, by Steve Stiles, May 4, 2011 (Boston, Massachusetts) — A rare randomized trial exploring the impact of tai chi in patients with mild to moderate heart failure found that the Chinese martial art, practiced throughout China and the world in part as a form of low-intensity exercise, can significantly improve objective measures of quality of life, exercise self-efficacy, and mood state . However, it saw no apparent effect of tai chi on standard functional assessments such as six-minute-walk distance or peak oxygen uptake.
“Tai chi exercise, a multicomponent mind-body training modality that is safe and has good rates of adherence, may provide value in improving daily exercise, quality of life, self-efficacy, and mood in frail, deconditioned patients with systolic heart failure,” write the authors, led by Dr Gloria Y Yeh (Beth Israel Deaconess Medical Center, Boston, MA), in the April 25, 2011 issue of the Archives of Internal Medicine. “A more restricted focus on traditional measured exercise capacity may underestimate the potential benefits of integrated interventions such as tai chi.”
The group’s findings and conclusions are consistent with Yeh’s presentation of the study at the Heart Failure Society of America 2010 Scientific Meeting, which heartwire reported at the time.
The single-blind study evenly randomized 100 patients with NYHA class 1–3 heart failure and an LVEF <40% (mean 29%) to a group-based, 12-week tai-chi program or a heart-failure education program conducted during the same period.
At 12 weeks, compared with baseline, those who had practiced tai chi showed significant improvements, compared with the education group, in results of the Minnesota Living With Heart Failure Questionnaire (MLHFQ) (p=0.02), the Cardiac Exercise Self-Efficacy Instrument (p<0.001), and the Profile of Mood States (p=0.01).
In an accompanying editorial , Dr John R Teerlink (San Francisco Veterans Affairs Medical Center, CA) agrees that various tests of exercise capacity and other functional measures commonly used in patients with heart failure may be limited in showing any potential benefits from interventions with a strong mind-body component, such as tai chi. He also agrees with Yeh et al that such interventions are tough to evaluate in heart-failure clinical trials as they are now conducted.
“As therapies move from a primary goal of increasing survival beyond physiological or functional surrogates to improving quality of life, a variety of other end points have emerged,” Teerlink writes; among them are the MLHFQ and the Kansas City Cardiomyopathy Questionnaire.
“The criticism that these measures do not correlate with rehospitalization rates or mortality is not relevant. As long as an intervention is safe, improvements in functional capacity or health-related quality of life are independently important, although underappreciated, goals reflecting different facets of the patient’s response to therapy,” according to Teerlink.
“However, for mind-body medicine to realize its potential, rigorously performed trials with sufficient attention to masking, control group, end-point selection, and sample-size determination are necessary.”
The current study is an advance in this regard, he writes, but it has limitations, including its small sample size–especially compared with the >2300 patients in HF ACTION. He and Yeh et al both point out the need for exploring the mechanisms of any benefit from tai chi in heart failure.
“Mind-body medicine holds tremendous potential to improve both functional capacity and health-related quality of life in patients with HF; it is time to give these therapies the studies they deserve.”
Yeh and Teerlink had no conflict-of-interest disclosures.
Survey Shows Many Americans Misunderstand the Effects of Wine and Salt on Heart Health
Reviewed by Laura J. Martin, MD
WebMD.com, May 3, 2011 by Bill Hendrick — Most Americans believe that drinking red wine is good for the heart but may not fully understand that failure to limit the amount they drink could lead to serious health problems, according to a new survey by the American Heart Association (AHA).
What’s more, most people also mistakenly believe that sea salt is a good low-sodium alternative to table salt, the survey shows.
The poll of 1,000 adults was conducted to help the AHA gauge American perceptions about wine and sodium consumption as those substances relate to heart health.
The AHA says drinking of any type of alcohol should be limited to no more than two drinks per day for men and one for women. That’s about 8 ounces of wine for men and 4 ounces for women.
The AHA says in a statement that heavy and regular drinking of alcohol — whether wine, beer, or spirits — can dramatically increase blood pressure, cause heart failure, lead to stroke and other health problems, and contribute to high triglycerides, alcoholism, suicide, accidents, and obesity.
It’s true, the AHA says, that limited wine intake seems to be good for the heart, and 76% of people surveyed knew that.
However, only 30% of those questioned were aware of the AHA’s recommended limits for daily wine drinking.
“This survey shows that we need to do a better job of educating people about the heart-health risks of overconsumption of wine, especially its possible role in increasing blood pressure,” says AHA spokesman Gerald Fletcher, MD, a professor of medicine-cardiovascular diseases at the Mayo Clinic College of Medicine in Jacksonville, Fla.
When it comes to salt, the survey suggests most people may be confused about low-sodium food choices.
For example, 61% of respondents agreed, incorrectly, that sea salt is a low-sodium alternative to table salt. In reality, kosher salt and most sea salt are chemically the same as table salt, containing 40% sodium, and thus count the same toward total sodium consumption.
Also, 46% of those surveyed said table salt is the primary source of sodium in American diets, which is wrong.
As much as 75% of the sodium consumed by Americans comes from processed foods such as soups, condiments, canned foods, prepared mixes, and tomato sauce.
The AHA recommends eating no more than 1,500 milligrams of sodium daily and advises Americans to read nutrition and ingredient labels carefully.
Read the Food Label
Sodium compounds are present whenever food labels include the words “soda” and “sodium” and the chemical symbol “Na,” the AHA says.
“High-sodium diets are linked to an increase in blood pressure and a higher risk for heart disease and stroke,” Fletcher says. “You must remember to read the Nutrition Facts panel and ingredient list on food and beverages.”
Other key findings of the survey:
- People who drink wine are no more likely to know the AHA’s recommended limits than nondrinkers.
- 73% of adults say they drink wine. Knowledge of the AHA’s recommended limits seems to increase with age.
- 87% of wine drinkers say wine is good for the heart, compared to 51% of respondents who don’t drink.
- 59% of respondents said they knew their blood pressure numbers and 25% said they had high blood pressure. Of those who said they had high blood pressure, 80% knew their numbers.
- Only 24% of respondents were knowledgeable about the AHA’s recommended limits for daily sodium consumption.
- 69% understood that people often can’t tell by the way they feel or look whether they have high blood pressure.
- About 95% of respondents indicated they knew they could reduce their risk for high blood pressure.
By Michael Smith, North American Correspondent, MedPage Today
Reviewed by Dori F. Zaleznik, MD; Associate Clinical Professor of Medicine, Harvard Medical School, Boston and Dorothy Caputo, MA, RN, BC-ADM, CDE, Nurse Planner
MedPageToday.com, May 4, 2011 — In a study that seems likely to re-energize the debate over dietary salt, European researchers found that the changes in the amount of sodium excreted in the urine were related to changes in systolic blood pressure.
But they were not linked to diastolic pressure or the risk of developing hypertension, according to Jan Staessen, MD, PhD, of the University of Leuven in Leuven, Belgium, and colleagues.
And levels of urinary sodium excretion were inversely related to the risk of dying of cardiovascular causes, Staessen and colleagues reported in the May 4 issue of the Journal of the American Medical Association.
Taken together, Staessen and colleagues argued, the findings do not support “the current recommendations of a generalized and indiscriminate reduction of salt intake at the population level.”
But the findings should be taken with a grain of salt, according to Ralph Sacco, MD, president of the American Heart Association and chairman of neurology at the University of Miami.
The study raises some questions, he said, but the “bulk of the evidence” still supports the view that cutting sodium will reduce blood pressure and improve cardiovascular outcomes.
The heart association earlier this year said the daily intake of sodium should be no more than 1,500 milligrams and Sacco told MedPage Today the group will stand by that.
“One study is not enough to change policy,” he said.
The findings come from analysis of participants in two European cohorts, with baseline and outcome data on a total of 3,681 people – the so-called “outcome cohort” – over a median follow-up of 7.9 years, the researchers reported.
Of those, 2,856 agreed to take part in follow-up analyses and were considered as two over-lapping groups.
On one hand, the researchers studied the links between changes in 24-hour urinary sodium excretion and changes in blood pressure, over a median of 6.1 years of follow-up, in 1,429 follow-up participants who had complete and accurate urine collection, no cardiovascular disease, and were not on antihypertensive medication.
On the other hand, they studied the incidence of hypertension over a median of 6.5 years in the 2,096
participants who did not have the condition at baseline.
The cohort was divided into thirds, based on 24-hour urinary sodium excretion, with average levels of 107 millimoles in the low tertile, 168 in the medium group, and 260 in the high tertile.
The study population was relatively young at baseline, the researchers noted, with an average age of 40.9 in the low tertile, 38.6 in the medium tertile, and 38.6 in the high group.
Staessen and colleagues found:
- Cardiovascular deaths decreased across increasing tertiles of 24-hour urinary sodium excretion. There were 50 deaths in the low group, 24 in the medium tertile, and 10 in the high group – 4.1%, 1.9%, and 0.8% of the cohort, respectively – and the differences were significant at P<0.001.
- The risk of cardiovascular death was significantly elevated in the low tertile, with a hazard ratio of 1.56 and a 95% confidence interval from 1.02 to 2.36, which was significant at P=0.04.
- 24-hour urinary sodium excretion was not associated with incidence of hypertension. There were 187 new cases of hypertension in the low tertile, 190 in the medium, and 175 in the high group over the follow-up period.
- In multivariate analyses, a 100-millimole increase in sodium excretion was associated with a systolic blood pressure of 1.71 millimeters of mercury (significant at P<0.001) but no change in diastolic pressure.
The researchers cautioned that the number of events was relatively small, owing to the youth of the cohort. And, they added, it may not apply to people other than those of European descent.
They also did not measure sodium sensitivity, they reported.
The heart association’s Sacco told MedPage Today that the study had a young population, with a relatively short follow-up, so that some outcomes – such as cardiovascular death – would be expected to be rare.
As well, he said, findings from an all-white European cohort may not completely apply to the U.S. population, with its large proportion of African Americans and Asians.
Sacco said that the average daily intake of sodium in the U.S. is about 3,500 milligrams, much of it from processed and packaged foods.
“That’s a lot of salt,” he said.
The Heart Association would like to see that down to 1,500 a day by 2020, he said.
WebMD, by Lisa Nainggolan, May 4, 2011 (Leuven, Belgium) — Controversial findings from a new European study question the need to try to curtail salt intake in populations around the world and refute computer-generated estimates of the lives and healthcare costs that would be saved by lowering sodium consumption . Dr Katarzyna Stolarz-Skrzypek (University of Leuven, Belgium) and colleagues report their results in the May 4, 2011 issue of the Journal of the American Medical Association.
“What our study basically shows is that it might not be right to impose a general reduction on sodium intake,” senior author Dr Jan A Staessen (University of Leuven, Belgium) told heartwire . “We are not negating previous studies, and I think sodium restriction is meaningful for patients who already have hypertension and perhaps for patients with heart failure, but there are very few arguments showing that reducing salt intake in the general population would result in substantial benefit.”
Most contentious of all, the new study shows that lower sodium intake– as measured by the “gold standard” of 24-hour sodium excretion–was associated with higher cardiovascular mortality. However, the study did find that there was a rise in systolic blood pressure of 1.71 mm Hg for each 100-mmol increment in sodium intake (p<0.001), an increase Staessen calls “very small,” over 6.2 years of follow-up.
These findings are therefore “paradoxical” and unreliable, says long-term advocate of salt reduction Dr Graham MacGregor (Queen Mary University of London, UK), who has spearheaded a successful UK campaign to reduce the sodium content in foods. “They’ve shown that salt puts up blood pressure, and yet they then claim that salt relates inversely to events; well, that doesn’t make sense,” and there is no attempt to explain this, he says, illustrating “the bias of the authors, in my view. Everything else that has been shown to lower BP is beneficial in terms of heart attacks and strokes.”
This is clever, but it’s harmful in my view. It’s like saying we don’t think cigarettes are harmful so we shouldn’t do anything about smoking.
In addition, this is a “badly written paper,” and there are “severe methodological problems” with it, most notably with urine collection in the group that had the lowest salt intake, MacGregor notes, adding that “JAMA has published a lot of controversial papers about salt. I really don’t think this is worth paying attention to. They are trying to create a stir. This is clever, but it’s harmful in my view. It’s like saying we don’t think cigarettes are harmful so we shouldn’t do anything about smoking,” he adds.
“The overall evidence [in favor of salt reduction] is overwhelming,” MacGregor asserts. “That isn’t to say we wouldn’t change our mind if we had really good evidence, but I don’t think this is it. This will not divert us from reducing salt intake worldwide. At a high-level meeting of the World Health Organization, salt reduction has been recommended as the next thing after tobacco reduction because it’s so cost-effective to implement and so easy to do.”
Mortality 50% Higher in the Lowest Tertile of Sodium Excretion
Staessen says that previous studies on which recommendations to lower sodium intake are based “are all short-term, controlled intervention trials, in which there are reductions in blood pressure in hypertensive patients and a small decrease in BP in normotensive volunteers” with sodium reduction, and “these studies have been extrapolated to the population as a whole.”
“The assumption that lower salt intake would in the long run lower blood pressure, to our knowledge, has not yet been confirmed in longitudinal population-based studies,” he and his colleagues observe.
They recruited participants from the Flemish Study on Environment, Genes and Health Outcomes (FLEMENGHO) and the European Project on Genes in Hypertension (EPOGH), which included patients from the Czech Republic, Italy, Poland, and Russia, as well as Belgians. This new study, says Staessen, represents “a comprehensive evaluation of the problem,” with a cohort representative of five European populations, long follow-up, and many outcomes measured, including 24-hour urinary sodium excretion at baseline and follow-up, BP at baseline and follow-up, and incidence of hypertension and total and cause-specific mortality.
We did not expect that the inverse association between cardiovascular mortality and sodium excretion would be so strong and so consistent.
Among 3681 participants who were free of cardiovascular disease at baseline, followed for a median of 7.9 years, cardiovascular deaths decreased across increasing tertiles of 24-hour sodium excretion, from 50 deaths in the low- (mean 107 mmol) to 24 in the medium- (mean 168 mmol) and 10 in the high-excretion group (mean 260 mmol; p<0.001), resulting in respective death rates of 4.1%, 1.9%, and 0.8%. In multivariable adjusted analyses, this inverse association retained significance (p=0.02); the hazard ratio in the low tertile was 1.56 (p=0.04).
These observations on cardiovascular mortality are “consistent with several other reports,” Staessen and colleagues say, one of which in particular was criticized because it was performed in hypertensive patients who were instructed to avoid high-salt foods for four to five days before sodium-excretion measurements were taken. “This was not at all the case in our study,” Staessen stressed to heartwire , noting that the participants were not given any instructions with regard to salt intake.
“We did not expect that the inverse association between cardiovascular mortality and sodium excretion would be so strong and so consistent,” he commented, pointing out that it persisted even after excluding all deaths that occurred within three years of enrollment, to rule out reverse causality.
Paper Is “Impossible to Decipher”
For heartwire , MacGregor expanded upon the methodological issues he has with this paper. Most important, problems with urine collection in the low-sodium group are evident from examining the creatinine excretion and the volume of urine, he says, noting that “they are all lower in the low-sodium group. If a group of people don’t collect a proper 24-hour urine, they’ll have a lower sodium excretion, and these may be people who are less compliant with treatment and more likely to get events.”
In addition, this paper is “almost impossible to decipher” in other ways, he says. “There are so many different groups and they analyze things in different ways for different sections, and you start going mad if you really try to work out what has been included and what hasn’t. They’ve all got different criteria, and in my view, some of the analyses have not been done correctly for various things.”
Finally, even if this study were “perfectly done” and there were no criticisms of it, including it in a meta-analysis of the multitude of studies on salt reduction “wouldn’t make any difference” to the overall outcome,” says MacGregor. “We’ll always get a few things that come out the wrong way around–it was the same for smoking–but the overall evidence [in favor of sodium reduction] is just overwhelming.”
Explanation for Inverse Association, But No Supporting Evidence
Staessen et al do suggest one underlying mechanism that could explain the inverse association they observed between lower sodium intake and higher CV mortality: that a salt intake low enough to decrease blood pressure also increases sympathetic nerve activity, decreases insulin sensitivity, activates the renin-angiotensin system, and stimulates aldosterone secretion.
This is the sort of thing that irritates me, these throwaway remarks that should never be allowed without references.
MacGregor bristles at this. “We have shown in our meta-analysis that reducing salt by the amounts we are recommending does not increase sympathetic tone, there is a trivial increase in renin, and no evidence of any adverse effects, no physiologic meaning whatsoever. This is the sort of thing that irritates me, these throwaway remarks that should never be allowed without references. Where are their references?”
“There are seven different types of evidence about salt reduction, ranging from epidemiologic to migration studies, from genetic data to population studies and treatment trials,” he notes. “The treatment trials clearly show that lowering salt intake lowers BP, and in this study they show this as well,” he concludes.
The authors report no conflicts of interest. MacGregor has no disclosures.