People with hard-to-treat heartbeat disturbances could soon be cured using high-intensity radio waves, say US researchers. Hakan Oral and his team at the University of Michigan restored normal heart rhythm in 80 per cent of patients with a condition called intermittent atrial fibrillation. This is a big improvement on existing treatments.
“This is very exciting, but we are still on a learning curve,” said Michael Henein, consultant cardiologist at the Royal Brompton hospital in London. “We don’t know the long-term outcome yet.”
Atrial fibrillation affects millions of people worldwide, mainly those over 70 years old. Normally, the contraction of the muscle in the two upper chambers of the heart – the atria – is tightly coordinated by electrical signals generated by pacemaker cells in an area called the sinus.
But if these signals get jumbled, the muscle cells no longer contract in unison. When this happens, the atria cannot pump blood out into the lower chambers of the heart efficiently. The blood pools and stagnates in the atria. It can then form clots, which can break off and cause strokes.
Atrial fibrillation can be caused by physical damage to the heart, such as coronary heart disease. But in some patients, there is no obvious damage. Instead, groups of heart cells inside the entrances to the pulmonary veins somehow become extra pacemakers, throwing the electrical signals in the heart into disarray.
Oral and his team based their trial on a technique pioneered by Michel Haissaguerre at the Haut Leveque hospital in Bordeaux. They threaded a catheter into the pulmonary veins of 70 patients. The catheter had a ring-shaped tip that could detect electrical signals and help the team track down the errant cells. The team then destroyed the cells around three of the four pulmonary veins with high-intensity radio waves via the catheter.
Existing treatments for atrial fibrillation involve drugs to calm the electrical signals and blood-thinning drugs to combat clots. Doctors can try “re-booting” the heart’s rhythm by applying a pulse of electricity to the patient’s chest – a process called external cardioversion. This works well, but up to half of all patients relapse within a year.
Over 80 per cent of Oral patients had their fibrillation either cured or improved. A year on, they are still doing well, and even improving, says Oral.
But the technique was not so successful in patients whose fibrillation had become chronic. Oral thinks that intermittent atrial fibrillation can lead to permanent changes in the heart if left untreated. “It may be important to intervene early,” he says. More extensive trials of the therapy are planned.
Journal reference: Circulation