Valve Replacement: Mechanical or Tissue?

Valve Replacement: Mechanical or Tissue?
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Valve Replacement: Mechanical or Tissue?

Valve Replacement: Mechanical or Tissue?

If you need a new aortic valve, age is the main factor when choosing which type to get.

Q. I'm 66 and will be having my aortic valve replaced soon. My surgeon suggested a tissue valve, but he also mentioned that I could get a mechanical valve instead. What are the key differences between these two choices?

A. In general, both types of replacement valves work very well. But there are pros and cons with each one. Historically, a person's age has been the main consideration when choosing between the two. Currently, the American College of Cardiology and the American Heart Association recommend mechanical valves for people under age 50 and biologic (tissue) valves for those over 70. For people like you who fall between those ages, neither type has an absolutely clear advantage over the other.

Mechanical valves are made from a special type of carbon or titanium and other sturdy materials. Their main advantage is their durability: a mechanical valve will usually last for the rest of the person's life. That is why they have been historically favored in younger people with an expected life span of several more decades. However, blood clots can lodge in the valve flaps or hinges and prevent the valve from working properly. That can be an imminently life-threatening situation. Additionally, those clots may break off and travel through the bloodstream. If a clot blocks an artery to the brain, that causes a stroke.

To avoid this problem, nearly all people who get mechanical heart valves must take anti-clotting medication, usually warfarin (Coumadin), for the rest of their lives. Warfarin increases the risk of bleeding, which can show up as bleeding from the nose, gums, or minor injuries — or, more rarely, as worrisome internal bleeding. However, careful monitoring of the degree of warfarin's effect on the blood can limit this danger.

Tissue valves, which are made from pig heart valves or cow heart-sac tissue, typically last about 15 years. But they usually don't require the lifelong use of anti-clotting drugs. Older people are more vulnerable to the bleeding side effects of warfarin. They're also less likely to outlive their new valves. So for them, a tissue valve is usually considered the better choice. However, for people who are already taking warfarin for another problem, such as atrial fibrillation or deep-vein thrombosis, a mechanical valve might make more sense.

Studies have been somewhat contradictory as to which valve is best for people in their 50s and 60s. In recent years, there's been a trend toward using tissue valves in people at the younger end of that range. The theory is that by the time those people need a second valve, it can be replaced using a minimally invasive procedure — a logical but unproven approach. In the next decade, we should have much more data to make an informed recommendation.

(Harvard Heart Letter)



Japan's New Flagship H3 Rocket Fails to Put Geolocation Satellite Into Orbit

Japan's H3 rocket No.8 carrying carrying the Michibiki No. 5 satellite lifts off from the Tanegashima Space Center on the southwestern island of Tanegashima, Kagoshima Prefecture, southwestern Japan, December 22, 2025, in this photo taken by Kyodo. Kyodo/via REUTERS
Japan's H3 rocket No.8 carrying carrying the Michibiki No. 5 satellite lifts off from the Tanegashima Space Center on the southwestern island of Tanegashima, Kagoshima Prefecture, southwestern Japan, December 22, 2025, in this photo taken by Kyodo. Kyodo/via REUTERS
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Japan's New Flagship H3 Rocket Fails to Put Geolocation Satellite Into Orbit

Japan's H3 rocket No.8 carrying carrying the Michibiki No. 5 satellite lifts off from the Tanegashima Space Center on the southwestern island of Tanegashima, Kagoshima Prefecture, southwestern Japan, December 22, 2025, in this photo taken by Kyodo. Kyodo/via REUTERS
Japan's H3 rocket No.8 carrying carrying the Michibiki No. 5 satellite lifts off from the Tanegashima Space Center on the southwestern island of Tanegashima, Kagoshima Prefecture, southwestern Japan, December 22, 2025, in this photo taken by Kyodo. Kyodo/via REUTERS

Japan's space agency said its H3 rocket carrying a navigation satellite failed to put the payload into a planned orbit, a setback for the country's new flagship rocket and its space launch program.

Monday's failure is the second for Japan's new flagship rocket after its botched 2023 debut flight and six successful flights, The Associated Press reported.

The Japan Aerospace Exploration Agency said the H3 rocket carrying the Michibiki 5 satellite took off from the Tanegashima Space Center on a southwestern Japanese island Monday as part of Japan's plans to have a more precise location positioning system of its own.

The rocket's second-stage engine burn unexpectedly had a premature cutoff and a subsequent separation of the satellite from the rocket could not be confirmed, Masashi Okada, a JAXA executive and launch director, told a news conference.

Whether the satellite was released into space or where it ended up is unknown, and that JAXA is investigating the data to determine the cause and other details, Okada said.

Jun Kondo, an official at the Ministry of Education, Culture, Sports, Science and Technology, told reporters that the failure was “extremely regrettable” and that the government set up a task force to investigate the cause and take necessary measures as soon as possible to “regain credibility.”

Monday's failure is a setback for Japan's new flagship that replaced the earlier mainstay H-2A which had near-perfect success record. It also delays Japan’s satellite launch plans, including one to have a more independent geolocation system for smartphones, maritime navigation and drones without relying on the US GPS system.

The H3 rocket is designed to be more cost-competitive in the global space market. Japan sees a stable, commercially competitive space transport capability as key to its space program and national security.

JAXA's H3 project manager, Makoto Arita, said the new flagship is still in the early stages of operation but can be globally competitive. “We will pull ourselves together so that we won't fall behind rivals. We'll fully investigate the cause and put H3 back on track.”

Monday's launch came five days after JAXA aborted just 17 seconds before liftoff, citing an abnormality of a water spray system at the launch facility, following an earlier problem with the rocket.

In its debut flight in March 2023, H3 failed to ignite the second-stage engine.
Japan currently has the quasi-zenith satellite system, or QZSS, with five satellites for a regional navigation system that first went into operation in 2018. The Michibiki 5 was to be the sixth of its network.

Japan currently relies partially on American GPS and wants to have a seven-satellite network system by March 2026 and an 11-satellite network by the late 2030s.


Scientists and Data Explain Why Kenya’s Lakes Are Rising as Thousands Face an Uncertain Future 

A man stands on a rooftop overlooking submerged homes after rising waters from Lake Naivasha flooded Kihoto Village, displacing hundreds, in Naivasha, Kenya's Rift Valley region, on Tuesday, Nov. 11, 2025. (AP Photo/Andrew Kasuku)
A man stands on a rooftop overlooking submerged homes after rising waters from Lake Naivasha flooded Kihoto Village, displacing hundreds, in Naivasha, Kenya's Rift Valley region, on Tuesday, Nov. 11, 2025. (AP Photo/Andrew Kasuku)
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Scientists and Data Explain Why Kenya’s Lakes Are Rising as Thousands Face an Uncertain Future 

A man stands on a rooftop overlooking submerged homes after rising waters from Lake Naivasha flooded Kihoto Village, displacing hundreds, in Naivasha, Kenya's Rift Valley region, on Tuesday, Nov. 11, 2025. (AP Photo/Andrew Kasuku)
A man stands on a rooftop overlooking submerged homes after rising waters from Lake Naivasha flooded Kihoto Village, displacing hundreds, in Naivasha, Kenya's Rift Valley region, on Tuesday, Nov. 11, 2025. (AP Photo/Andrew Kasuku)

When Dickson Ngome first leased his farm at Lake Naivasha in Kenya’s Rift Valley in 2008, it was over 2 kilometers (1.2 miles) from shore. The farm was on 1.5 acres (0.6 hectares) of fertile land where he grew vegetables to sell at local markets.

At the time, the lake was receding and people were worried that it might dry up altogether. But since 2011, the shore has crept ever closer. The rains started early this year, in September, and didn't let up for months.

One morning in late October, Ngome and his family woke up to find their home and farm inside the lake. The lake levels had risen overnight and about a foot of water covered everything.

“It seemed as if the lake was far from our homes,” Ngome’s wife, Rose Wafula, told The Associated Press. “And then one night we were shocked to find our houses flooded. The water came from nowhere.”

The couple and their four children have had to leave home and are camping out on the first floor of an abandoned school nearby.

Some 5,000 people were displaced by the rise in Lake Naivasha’s levels this year. Some scientists attribute the higher levels to increased rains caused by climate change, although there may be other factors causing the lake’s steady rise over the past decade.

The lake is a tourism hot spot and surrounded by farms, mostly growing flowers, which have gradually been disappearing into the water as the lake levels rise.

Rising levels have not been isolated to Naivasha: Kenya’s Lake Baringo, Lake Nakuru and Lake Turkana — all in the Rift Valley — have been steadily rising for 15 years.

“The lakes have risen almost beyond the highest level they have ever reached,” said Simon Onywere, who teaches environmental planning at Kenyatta University in Kenya’s capital Nairobi.

Rising lake levels displaced tens of thousands

A study in the Journal of Hydrology last year found that lake areas in East Africa increased by 71,822 square kilometers (27,730 square miles) between 2011 and 2023. That affects a lot of people: By 2021, more than 75,000 households had been displaced across the Rift Valley, according to a study commissioned that year by the Kenyan Environment Ministry and the United Nations Development Program.

In Baringo, the submerged buildings that made headlines in 2020 and 2021 are still underwater.

“In Lake Baringo, the water rose almost 14 meters,” Onywere said. “Everything went under, completely under. Buildings will never be seen again, like the Block Hotels of Lake Baringo.”

Flower farms taking a beating Lake Naivasha has risen steadily too, “engulfing three quarters of some flower farms,” Onywere said.

Horticulture is a major economic sector in Kenya, generating just over a billion US dollars in revenue in 2024 and providing 40% of the volume of roses sold in the European Union, according to Kenya’s Ministry of Foreign Affairs.

Significant research has gone into the reasons behind the rising lakes phenomenon: A 2021 study on the rise of Kenya’s Rift Valley lakes was coauthored by Kenyan meteorologist Richard Muita, who is now acting assistant director of the Kenya Meteorological Department.

“There are researchers who come up with drivers that are geological, others with reasons like planetary factors,” Muita said. “The Kenya Meteorological Department found that the water level rises are associated with rainfall patterns and temperature changes. When the rains are plentiful, it aligns with the increase in the levels of the Rift Valley lake waters.”

Sedimentation is also a factor. “From the research I have read, there’s a lot of sediment, especially from agricultural related activities, that flows into these lakes,” says Muita.

‘A mess’ made by the government years ago

Naivasha’s official high water mark was demarcated at 1,892.8 meters (6,210 feet) above sea level by the Riparian Association in 1906, and is still used by surveyors today. That means this year’s flooding was still almost a meter (3 feet) below the high mark.

It also means that the community of Kihoto on Lake Naivasha where the Ngomes lived lies on riparian land — land that falls below the high water mark, and can only be owned by the government.

“It’s a mess established by the government ... towards the late 1960s,” said Silas Wanjala, general manager of the Lake Naivasha Riparian Association, which was founded some 120 years ago and has been keeping meticulous records of the lake’s water levels since.

Back then, a farmer was given a “temporary agricultural lease” on Kihoto, said Wanjala. When it later flooded and the farmer packed up and left, the farmworkers stayed on the land and later applied for subdivisions, which were approved. In the 60-odd years since, a whole settlement has grown on land that is officially not for lease or sale.

This also isn’t the first time it’s been flooded, said Wanjala. It's just very rare that the water comes up this high. That’s little consolation for the people who have been displaced by this year’s floods and now cannot go home without risking confrontations with hippopotamuses.

To support those people, the county is focusing its efforts on where the need is greatest.

“We are tackling this as an emergency," says Joyce Ncece, chief officer for disaster management in Nakuru County, which oversees Lake Naivasha. “The county government has provided trucks to help families relocate. We have been helping to pay rent for those who lack the finances.”

Scientists like Onywere and Muita are hoping for longer-term solutions. “Could we have predicted this so that we could have done better infrastructure in less risk-prone areas?” Onywere said.

Muita wants to see a more concerted global effort to combat climate change, as well as local, nature-based solutions centered on Indigenous knowledge, such as “conservation agriculture, where there is very limited disturbance of the land,” to reduce sedimentation of the lakes.

But all of this is of little help to Ngome and Wafula, who are still living at the school with their children. As the rest of the world looks forward to the holidays and new year, their future is uncertain. Lake Naivasha’s continuous rise over the past 15 years does not bode well: They have no idea when, or if, their farm will ever be back on dry land.


Japan Footballer 'King Kazu' to Play on at the Age of 58

Japanese footballer Kazuyoshi Miura is set to join a new team at the age of 58. STR / AFP
Japanese footballer Kazuyoshi Miura is set to join a new team at the age of 58. STR / AFP
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Japan Footballer 'King Kazu' to Play on at the Age of 58

Japanese footballer Kazuyoshi Miura is set to join a new team at the age of 58. STR / AFP
Japanese footballer Kazuyoshi Miura is set to join a new team at the age of 58. STR / AFP

Evergreen 58-year-old striker Kazuyoshi Miura is set to join a Japanese third-division team to begin his 41th season as a professional footballer, local media reported Sunday.

Miura, known as "King Kazu", will join Fukushima United on a year-long loan after spending last season with fourth-tier Atletico Suzuka, said AFP.

The signing is not yet official but Miura's recent moves have typically been announced at 11:11am on January 11, in a nod to his shirt number.

The former Japan international will turn 59 in February.

He made seven appearances last season for Suzuka, who were relegated to Japan's regional leagues after finishing second-bottom of the table and losing a playoff.

Miura made his professional debut in 1986 for Brazilian team Santos and he has also played for teams in Italy, Croatia, Australia and Portugal.

He helped put football in Japan on the map when the professional J. League was launched in 1993.

He made his Japan debut in 1990 but was famously left out of the squad for their first World Cup finals appearance in 1998, despite scoring 55 goals in 89 games for the national side.