Magnetic interference from MP3 headphones can interfere with heart pacemakers （心脏起搏器）and implantable defibrillators, a study has found.
Heart patients with such devices should not put their headphones in their breast pocket or hang them round their neck, researchers have warned.
Small but strong magents inside headphones can deactivate the devices if placed within 1.2 inches of them, posing a real risk to the patient, researchers told an American Heart Association meeting in New Orleans. The MP3 players themselves posed no threat to pacemakers and defibrillators.
Dr. William Maisel of the Medical Device Safety Institute at Beth Israel Medical Center in Boston led a team that tested eight models of MP3 player headphones, including clip-on and ear bud types, in 60 defibrillator and pacemaker patients. They placed the headphones on the patients' chests, directly over the devices. The headphones interfered with the heart devices in about a quarter of the patients and interference was twice as likely in those with a defibrillator than with a pacemaker.
A pacemaker sends electrical impulses to the heart to speed up or slow cardiac rhythm. The magnet, however, could make it deliver a signal no matter what the heart rate is, possibly leading to palpitations or arrhythmia, the researchers said.
An implantable defibrillator signals the heart to normalize its rhythm if it gets too fast or slow. A magnet could de-activate it, making it ignore an abnormal heart rhythm instead of delivering an electrical shock to normalize it. The devices usually go back to working the right way after the headphones are removed, the researchers said.
"The main message here is: it's fine for patients to use their headphones normally, meaning they can listen to music and keep the headphones in their ears. But what they should not do is put the headphones near their device," Dr Maisel said.
72. The underlined word deadactive in the third paragraoh probably means “to make something_______”
A. incorrect B. normal C. ineffective D. useful
73. According to the study, what is actually endangering heart patients with heart devices?
A. The music they hear with MP3 headphones
B. The eight models of MP3 players that have been tested.
C. Magnetic interference from MP3 headphones.
D. The magnets inside pacemakers and defibrillators.
74. What is the fourth paragraph about ?
A. Atest to monitor how heart beats are interfered with.
B. How many patients were tested
C. A brief introduction to defibrillators and pacemakers .
D. Dr. William Maisel was concerned about heart problems.
75. From the passage we can learn that________.
A. MP3 players are gaining popularity among heart patients
B. pacemakers and defibrillators are actually harmful to people’s health
C. heart patients should not listen to music.
D. pacemakers and defibrillators can help normalize heart rhythm