Wood Street Clinic Blog

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Surgery with ultrasound treats high blood pressure in trial

A minimally invasive surgical procedure that targets nerves leading to the kidneys could one day offer a safe way for some people to reduce their blood pressure medications.
older lady looking at blood pressure results with doctor
Scientists find a new way to optimize blood pressure control.

Investigators have announced the 6-month results of an international clinical trial on the safety and effectiveness of renal denervation by ultrasound as a treatment for mild to moderate high blood pressure.

The findings featured recently at the American College of Cardiology Conference in New Orleans and in a study paper in the journal Circulation.

Surgeons carry out the procedure, which takes about 1 hour, under local anesthetic. It decreases activity in nerves that link the brain to the kidneys and carry signals that regulate blood pressure.

The 2-month results from the randomized, controlled trial had already shown that the procedure resulted in a more significant reduction in blood pressure, compared with a "sham operation."

None of the people in the trial took their blood pressure drugs during the first 2 months. They then resumed blood pressure medication in a managed way, as necessary.

Now, the more recent results reveal that the participants who underwent the ultrasound surgery maintained their reduced blood pressure for 6 months.

Compared with those who had the sham operation, fewer participants who had the surgery needed to resume blood pressure medication, and those who did required fewer drugs at lower doses.

"These results," says lead trial investigator in the United Kingdom Melvin D. Lobo, a professor at Queen Mary University in London and also of Barts Health NHS Trust, both in the U.K., "point towards an exciting future for this new technology."

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Hypertension and kidney nerves

High blood pressure, or hypertension, is a growing global health issue. According to a report in The Lancet, between 1975 and 2015, the number of adults living with high blood pressure rose from 594 million to 1.13 billion.

Having high blood pressure increases the risk of heart disease, heart failure, and other conditions.

Some people can keep their blood pressure under control by watching their weight, doing plenty of exercise, and maintaining a healthful diet. Others may need to supplement these measures with medication.

However, some people struggle to control high blood pressure even with lifestyle changes and medication.

The kidneys have a rich system of nerves for sending and receiving messages.

Scientists have discovered that overactivity in this system can raise blood pressure through its interaction with the body's sympathetic nervous system.

Renal denervation by ultrasound is a treatment that aims to relieve high blood pressure by disrupting the nerves leading to the kidneys.

The procedure involves inserting a device through a catheter in the groin to reach up into the artery of a kidney. The device emits ultrasound waves that then heat up and damage some of the nerve fibers that surround the artery.

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6-month results look promising

The 6-month results report a comparison of the procedure with a sham operation in 140 people at 51 sites in Belgium, France, Germany, the Netherlands, the United Kingdom, and the United States.

After 6 months, 58 percent of those who underwent the procedure had maintained their lower blood pressure compared with 42 percent who had received the sham operation.

Overall, most of the participants needed to resume their medications to maintain blood pressure control. However, 35.8 percent of the renal denervation group were still not taking drugs at the 6-month point compared with only 15.5 percent in the sham operation group.

Those who underwent renal denervation also showed a greater reduction in blood pressure. After 6 months, the average reduction was 18.1 millimeters of mercury (mm Hg) in the treatment group and 15.6 mm Hg in the sham operation group.

There were no safety issues among any of the participants.

It is important to know that the company that manufactures the renal denervation device that the surgeons used in this trial also funded the study.

"If long-term safety and efficacy are proven in larger trials which are currently underway, we hope that renal denervation therapy could soon be offered as an alternative to many lifelong medications for hypertension."

Prof. Melvin D. Lobo

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Why your gut may hold the key to cardiovascular health

New research, which appears in The Journal of Physiology, examines the role that gut bacteria might play in preserving the health of our arteries.
illustration of a heart
Your gut may control the health of your arteries and heart, suggests new research.

An increasing number of studies suggest that the bacteria in our guts hold the key to healthy aging.

For instance, a recent conference that Medical News Today reported on featured research in the worm Caenorhabditis elegans. The results suggested that colonizing the gut with specific strains of bacteria, for example, can delay aging and prevent a host of age-related chronic diseases.

Now, research in mice strengthens the idea that gut bacteria mediate the aging process. Specifically, scientists have examined the link between the composition of the gut microbiota in mice and vascular aging.

Vienna Brunt, a postdoctoral researcher in the Department of Integrative Physiology at the University of Colorado, Boulder, is the study's lead author. Doug Seals, a professor and the director of the university's Integrative Physiology of Aging Laboratory, is the senior author.

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Studying gut bacteria and vascular health

Brunt and colleagues administered a "cocktail of broad‐spectrum, poorly absorbed antibiotics" to a group of young mice and a group of old mice. They added the antibiotics to the drinking water of the rodents for a period of 3–4 weeks to suppress their gut microbiota.

Next, the researchers examined the health of the rodents' vascular systems by measuring their arterial stiffness and the health of the endothelium — that is, the layer of cells that line the inside of the arteries.

Brunt and her team also examined the rodents' blood samples for markers of inflammation and oxidative stress, such as harmful free radicals.

Oxidative stress occurs when the body produces too many free radicals and does not have enough antioxidants to degrade them. Studies indicate that this phenomenon contributes to hypertension, cardiovascular disease, and aging in general.

The researchers also measured levels of nitric oxide, a compound that expands the blood vessels. Finally, they examined the "age-related changes" in each rodent's gut microbiota.

At the end of the study period, the scientists found that the old mice benefited greatly from the antibiotic treatment, while the intervention had no effect on young mice.

Specifically, "When you suppressed the microbiome of the old mice, their vascular health was restored to that of young mice," reports Prof. Seals.

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How old age influences gut health

Next, the scientists set out to identify certain age-related changes in the microbiota of rodents. Their aim was to understand how suppressing the microbiota may preserve vascular health.

To do so, they genetically sequenced the fecal samples of another group of old mice and compared them with those of young mice.

"In general, in the old mice, we saw an increased prevalence of microbes that are pro-inflammatory and have been previously associated with diseases," says lead author Brunt.

These included taxa of microbes that previous studies had linked with gut dysbiosis — an imbalance between the "friendly" bacteria in our guts and other pathogens.

For example, the study found that the old mice had a higher concentration of proteobacteria — a major class that includes well-known pathogens such as Escherichia coli, Salmonella, and Campylobacter bacteria.

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The scientists also analyzed blood plasma levels of a compound called trimethylamine N‐oxide, or TMAO. This is a "gut-derived metabolite," which means that it is a compound produced when microorganisms in the gut break down nutrients from food.

Although the role of TMAO in chronic disease remains uncertain, some previous studies found high levels of TMAO in people with "cardiovascular disease, kidney disease, type 2 diabetes mellitus, and cancer."

Specifically, recent studies have suggested that TMAO interacts with platelets and raises the risk of stroke and heart attack.

In the current study, the old mice had three times as much TMAO in their blood as the young mice, and the researchers found that antibiotic treatment suppressed TMAO levels.

Brunt and her team conclude:

"The results of the present study provide the first evidence for the gut microbiome being an important mediator of age-related arterial dysfunction and oxidative stress."

Fountain of youth may lie in the gut

The findings, continue the authors, also indicate "that therapeutic strategies targeting gut microbiome health may hold promise for preserving arterial function and reducing cardiovascular risk with aging in humans."

The researchers suggest that eating foods rich in probiotics, such as kefir, yogurt, or kimchi, may help preserve cardiovascular health well into old age.

Prof. Seals comments on the results, saying, "We have long known that oxidative stress and inflammation are involved in making arteries unhealthy over time, but we didn't know why arteries begin to get inflamed and stressed. Something is triggering this."

"We now suspect that, with age, the gut microbiota begins producing toxic molecules, including TMAO, which get into the bloodstream, cause inflammation and oxidative stress, and damage tissue," he continues.

In other words, say the authors, "The fountain of youth may actually lie in the gut."

"This is the first study to show that changes in the gut microbiome with aging have an adverse impact on vascular health. [...] It opens up a whole new avenue of potential interventions to prevent cardiovascular disease."

Vienna Brunt, Ph.D.

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10 minutes of leisurely activity per week may lower death risk

New research suggests that adults over the age of 40 who engage in leisurely physical activity — such as dancing, gardening, or going for a walk — for even a short amount of time each week may have a lower risk of death from multiple causes.
two mature women dancing together
Even short amounts of leisurely physical activity, such as dancing, may reduce a person's death risk.

Previous research has shown that engaging even in low-level physical activity — including leisurely tasks, such as gardening — may help protect brain health and cardiovascular health, among other benefits.

Now, a recent observational study, working with tens of thousands of people aged 40 and over has found a link between a lower risk of death from different causes and low levels of physical activity.

This was a collaborative study by researchers from the Shandong University in Jinan, China, the University of Texas Medical Branch in Galveston, and the University of Minnesota in Minneapolis, as well as from other research institutions.

The research — whose results appeared yesterday in the British Journal of Sports Medicine — indicate that people who spend even a short time each week being physically active have a lower risk of death linked to cardiovascular, cancer, and all-cause mortality.

At the same time, the study authors note that participating in more intense types of exercise, including running and cycling, do have the potential to bring more significant health benefits.

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Even low-level activity cuts death risk

The researchers analyzed data collected through the National Health Interview Surveys — a series of yearly surveys that ask people from the United States to offer information about their health and lifestyle habits.

First author Min Zhao and colleagues looked at information gathered in 1997–2008 from 88,140 adults in the U.S., with ages ranging from 40 to 85. They also collated that data, which referred to health and physical activity practices, with information from national death registers, available up to the end of 2011.

For reference, the team estimated that 1 minute of vigorous exercise would equate to 2 minutes of moderate-intensity activity, such as gardening, dancing, or going for a brisk walk. In their analysis, the researchers only included physical activities that lasted for 10 or more minutes at one time.

The researchers found that, unlike people who were very physically inactive, individuals who engaged in 10–59 minutes of moderate, leisurely physical activity per week had an 18 percent lower risk of all-cause death.

People who engaged in moderate physical activity for a little longer — between 150 and 299 minutes per week — saw an even steeper drop in all-cause death risk, of 31 percent.

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And those who spent 1,500 minutes or more being physically active in their leisure time each week experienced a 46 percent decrease in their overall mortality risk.

The researchers observed similar associations between increased levels of physical activity and the risk of death related to cancer.

Finally, individuals who spent 10–59 minutes per week doing leisurely physical activities saw a 12 percent lower risk of death tied to cardiovascular events, and people who were active for 120–299 minutes every week had a 37 percent lower risk of death due to cardiovascular causes.

However, the researchers note that engaging in physical activities for much longer than 1,500 minutes per week did not bring any extra benefits in this respect.

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More is not better, but more vigorous is

Although the authors acknowledge that this was an observational study that cannot determine cause and effect relationships, they also note that the considerable cohort size is representative and that their current findings support existing notions about the benefits of engaging in moderate physical activity.

Nevertheless, the results also showed that people who opted for vigorous rather than lighter physical activity had a much lower mortality risk.

The authors do note that participating in 1,500 or more minutes of moderate physical activity per week "is difficult to achieve for a working adult," so they advise that "[p]articipation in vigorous-intensity activity is more time-efficient than moderate-intensity activity."

"Assuming causality of the associations we observed, both low and high levels of [physical activity] have beneficial effects on all-cause and cause-specific mortality risk," the authors conclude, adding:

"Importantly, vigorous [physical activity] has added benefits for reducing mortality compared with moderate [physical activity]. Promoting [physical activity] of any intensity and amount is an important approach to reducing mortality risk in the general population."

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Higher cholesterol, egg consumption linked to heart disease

A recent study has linked higher consumption of eggs or dietary cholesterol to a higher risk of cardiovascular disease and premature death. The finding is likely to rekindle the debate on eggs and heart health.
close-up of hands preparing eggs in a pan
New research suggests that people should restrict their daily egg intake as part of a healthful diet.

For example, the new study seems to contradict the decision in the United States to omit specific limits on daily intakes of dietary cholesterol and eggs from official advice on healthful eating.

Researchers from Northwestern University Feinberg School of Medicine in Chicago, IL, and other institutions pooled and analyzed data from six U.S. cohort studies covering a total of 29,615 people. Of these, 45 percent were male and 31 percent were black.

They compared eating patterns at baseline, when the average participant age was 52 years, with cardiovascular diseases and deaths that occurred during a follow-up that lasted up to 31 years and whose midpoint was 17 years.

The team describes the findings in a JAMA paper.

Co-corresponding study author Norrina B. Allen Ph.D., an associate professor of preventive medicine at Northwestern, says that the "take-home message" of the study "is really about cholesterol, which happens to be high in eggs and specifically yolks."

"People who consume less cholesterol have a lower risk of heart disease," she adds.

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Guidelines do not limit cholesterol or eggs

According to the Centers for Disease Control and Prevention (CDC), heart disease is the "leading cause of death" in the U.S.

For decades there has been a debate about whether consumption of eggs or dietary cholesterol raises the risk of heart disease and early death.

The official recommendation in the U.S. before 2015 was that people should limit their daily egg consumption to no more than 300 milligrams (mg), which is less than two large eggs.

The more recent Dietary Guidelines for Americans 2015–2020, however, no longer provide limits on dietary cholesterol and egg intake. They include weekly intake of eggs as part of a healthful diet.

"Adequate evidence," they claim, "is not available for a quantitative limit for dietary cholesterol specific to the Dietary Guidelines."

The revised guidelines do, however, retain the message that the choice to drop specific limits does "not suggest that dietary cholesterol is no longer important to consider when building health[ful] eating patterns."

Only foods of animal origin — including dairy products, eggs, shellfish, poultry, and meat — contain dietary cholesterol.

Of the foods most typical of the U.S. diet, eggs contain the most cholesterol. There are around 186 mg of cholesterol in the yolk of a large egg.

The average U.S. adult consumes about 300 mg of dietary cholesterol per day and about three or four eggs per week.

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Higher risk of heart disease and death

Dr. Allen believes that the problem with studies that have found no links between egg consumption and higher risk of cardiovascular disease is that they used less diverse samples and shorter follow-ups, and that they were less able to adjust for other items in the diet.

"Our study," she notes, "showed if two people had [the] exact same diet and the only difference in diet was eggs, then you could directly measure the effect of the egg consumption on heart disease."

The dietary data for the new study came either from completion of questionnaires or interviews that took place during a single visit. These yielded details of what each person had eaten either in the previous year or month.

Around 5,400 cardiovascular events and 6,132 deaths from all causes occurred over the follow-up period. Examples of cardiovascular events include diagnoses of heart disease, stroke, and heart failure.

The scientists found that for "each additional" intake of 300 mg of dietary cholesterol per day, there was a significant 17 percent higher risk of cardiovascular disease and 18 percent higher risk of death from any cause.

The team also calculated the "absolute risk differences" for these results. These were 3.24 percent and 4.43 percent, respectively.

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In other words, for every 1,000 participants in their study, there were 32 additional diagnoses of cardiovascular disease and 4 deaths for every extra 300 mg of cholesterol consumed per day.

The analysis also showed that for each additional half egg eaten per day, there was a 6 percent higher risk of cardiovascular disease and an 8 percent higher risk of all-cause death.

The overall quality of people's diet, the type and amount of fat that they ate, and the amount of exercise that they undertook appeared to have no effect on these links.

"These results," explain the study authors, "should be considered in the development of dietary guidelines and updates."

Single snapshot of diet pattern

Among the study's strengths are the fact that it used a large and diverse sample of people from the U.S., and that there was a long follow-up period.

However, one limitation worth noting is that it only used a single snapshot of egg and cholesterol consumption, and that was at the beginning of the follow-up. People can change their eating habits, and 17–31 years offers plenty of opportunity to do so.

Commenting on the findings, Tom Sanders — who is a professor of nutrition and dietetics at King's College London in the United Kingdom — points out that because the study is prospective, it cannot establish cause and effect; it can only suggest links.

"However," he adds, "the take-home message supported by the accompanying editorial would support the view that a typical [U.S.] diet, which contains lots of meat and plenty of eggs, is associated with poor cardiovascular health and that the [country's] dietary guidelines should reinstate its recommendation that cholesterol intake should not exceed 300 mg per day."

"As part of a healthy diet, people need to consume lower amounts of cholesterol."

Norrina B. Allen Ph.D.

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Common blood pressure drug may increase cardiac arrest risk

A preliminary study concludes that a drug that doctors commonly prescribe to treat angina and blood pressure might increase the risk of sudden cardiac arrest.
Woman with chest pain sitting on a bench
A recent study looked at the risk factors behind cardiac arrest.

Cardiac arrest occurs when the heart stops pumping blood around the body. If a person does not receive treatment, cardiac arrest can be lethal within minutes.

According to the American Heart Association (AHA), in the United States, around 475,000 people die from cardiac arrest each year.

It claims more lives than colorectal cancer, breast cancer, prostate cancer, pneumonia, influenza, vehicle accidents, firearms, HIV, and house fires combined.

The AHA describe cardiac arrest "as one of the most lethal public health problems in the U.S." So, because cardiac arrest is both serious and common, understanding the risk factors involved is essential.

To this end, the European Resuscitation Council set up a project that collects data on cardiac arrest, called the European Sudden Cardiac Arrest network (ESCAPE-NET).

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A new risk factor?

A recent study using ESCAPE-NET data investigated whether a common group of drugs might play a role in cardiac arrest.

Healthcare providers use dihydropyridines to treat high blood pressure and angina, which is chest pain related to reduced blood flow to the heart. The project focused on two dihydropyridines: nifedipine and amlodipine.

The scientists had access to data from the Dutch Amsterdam Resuscitation Studies registry and the Danish Cardiac Arrest Registry, both of which form part of ESCAPE-NET.

The researchers presented their findings at EHRA 2019, the annual congress of the European Heart Rhythm Association, which is taking place in Lisbon, Portugal.

In total, they had access to data from more than 10,000 people who were taking dihydropyridines and 50,000 controls.

Their analysis showed that those who took high-dose nifedipine were significantly more likely to have an out-of-hospital cardiac arrest than those who were not taking dihydropyridines or who were taking amlodipine.

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Why might this be happening?

The scientists moved into the laboratory to examine why the actions of the two drugs differed. Both use the same mechanism, so why does one increase the risk of cardiac arrest while the other appears to make no difference?

Dihydropyridines work by blocking L-type calcium channels. When these channels are blocked, the action potential of cardiac cells becomes shorter.

The phrase "action potential" describes a change in the charge of a membrane associated with the transmission of an impulse. They occur in nerves and muscle cells.

This change could, potentially, drive the arrhythmias that lead to cardiac arrests.

Interestingly, these in vitro experiments matched the findings of the population study. High doses of nifedipine shortened action potentials significantly more than high-dose amlodipine.

"Nifedipine and amlodipine are often used by many cardiologists and other physicians, and the choice often depends on the prescriber's preference and personal experience."

ESCAPE-NET project leader Dr. Hanno Tan

Dr. Tan adds, "Both drugs are generally considered to be equally effective and safe and neither has been associated with sudden cardiac arrest."

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"This study suggests that high-dose nifedipine may increase the risk of sudden cardiac arrest due to fatal cardiac arrhythmia while amlodipine does not."

It is important to note that because this is a new line of investigation, it will be vital to replicate the findings using more participants and other demographics.

As Dr. Tan concludes, "If these findings are confirmed in other studies, they may have to be taken into account when the use of either drug is considered."

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