A: This is a growing concern and one being addressed by Dr. Michael Sole of the University Health Network (UHN) in Toronto. He has found that chronic sleep cycle disruption can seriously enlarge and damage the heart. In a 2008 study, Sole showed that when hamsters’ sleep cycles are chronically out of sync with external stimuli such as light and darkness, the animals die at a younger age with cardiomyopathy (an enlarged heart) and severe kidney disease. When sleep cycles are normalized, the harmful effects are reversed.
Sole's research shows that renewal and repair of heart tissues occur mainly during sleep at night. "Cell renewal and remodelling is a rhythmic process that is dependent on synchronicity between the external environment and the body’s internal clock," says Sole, a cardiologist at the UHN’s Peter Munk Cardiac Centre. "Disrupting the daynight sleep cycle interrupts the renewal process, and that interruption leads to tissue disease. Heart muscle cells become impaired and die, and are replaced by scar tissue."
His findings have disturbing implications for the nearly 30 per cent of Canadians who work irregular shifts. Sole advises these people to maintain a consistent schedule for a month or more if possible, so that their body has time to adjust its internal clock. Healthy sleep – seven to eight hours – is as important to heart health as nutrition and exercise, he says.
This research could be particularly worrisome for people who already have heart disease or high blood pressure for whom a regular day-night sleep pattern is especially important. "I'd be very concerned about a patient with heart problems doing shift work," he says.
Q: More and more patients are getting stents to prop open narrowed arteries following a balloon angioplasty. Are these devices safe?
Yes, increasingly so.
Dr. Michael Kutryk of St. Michael's Hospital in Toronto has come up with a way to harness the body's ability to heal the area of the blood vessel damaged during an angioplasty procedure. He has developed a coronary stent coated with antibodies that attract endothelial progenitor cells (EPC) circulating in the bloodstream. EPCs are involved in the repair of damaged blood vessels; they evolve into endothelial cells that line blood vessels and allow blood to flow smoothly.
The new device offers key advantages over the commonly used drug-eluting stents (those coated with a drug to prevent renarrowing of the artery). Results from a 2008 European study suggest that these new antibody-coated stents promote faster blood vessel healing and reduce the risk of blood clots by rapidly forming a protective endothelial layer over the stent. And while patients treated with drug-eluting stents must take bloodthinning medications for the first year after angioplasty to prevent blood clots, the new stent eliminates the need for this medication. "With antibody-coated stents, the risk of blood clotting is as low as can be," says Kutryk. "That’s important because 50 per cent of patients who develop blood clots after angioplasty will die."
Angioplasty procedures using this new invention have been performed on more than 20,000 patients at 250 medical centres worldwide. At St. Michael’s Hospital in Toronto, Kutryk had performed 18 procedures by mid-November on patients who were allergic to blood-thinning medications or who were actively bleeding and therefore could not use them (and so were inelligible for drug-eluting stents). Without the new stent, most would not tolerate open-heart surgery. Kutryk expects the device to be approved for wide use in Canada within two years.
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