Shortly before a car veered onto a sidewalk and ran over several pedestrians around half past noon last month in downtown Osaka, driver Atsushi Ohashi probably suffered a tear in the wall of a major artery that caused him to lose consciousness.
The accident left Ohashi, 51, and another man dead, and another nine people injured. One remains in critical condition.
The tear, known as an aortic dissection, happens in the aorta, the main artery carrying blood out of the heart. The tear allows blood to flow between layers of the blood vessel wall, which can cause the artery to burst or slow blood flow to other organs.
Along with chest and back pain, the condition can also hamper blood flow to the brain, affecting one’s judgment, said Masahito Hitosugi, professor of social medicine at Shiga University of Medical Science.
“Stress from driving may trigger the disease,” Hitosugi said. “If you feel something is wrong with your health, you better not drive.”
The rare but potentially catastrophic malady can strike anyone. But Hitosugi said smokers and people with hypertension are at greater risk of aortic dissection. High levels of cholesterol or neutral fat can also trigger it.
Aortic dissection has an incidence rate of about five or six per 100,000 people, with older individuals at higher risk.
Between 1990 and 2014, Jichi Medical University’s Saitama Medical Center conducted surgery on 605 patients afflicted by acute aortic dissection, its deputy head Hideo Adachi said.
Eight of the 605 experienced the condition while driving, with two losing consciousness. One case led to an incident of property damage, while the other was reined in by a passenger who managed to stop the vehicle.
According to the National Police Agency, there were 209 traffic accidents caused acute medical attacks in 2014. Heart attacks and strokes were blamed for 52 of them.
In a case similar to the Osaka incident, a tour bus driver in Sapporo died in 2011 after being hit by an acute aortic dissection. A passenger brought the bus to a halt after it hit the guardrails.