Treatment targets spinal cord patients
by Toni Baker
Quadriplegics whose hearts recurrently slow or stop may need aggressive therapy to avoid further cardiovascular problems and even death, MCG researchers say.
A study subset of newly injured quadriplegics showed that less aggressive therapies, such as drugs and a pacemaker placed on top of the chest, simply were not sufficient, said Dr. Andres F. Ruiz-Arango, cardiology fellow and corresponding author of the article in the July/August issue of Cardiology in Review.
The heart’s natural pacemaker relies on the sympathetic nervous system to speed it up and the parasympathetic nervous system to slow it down, said Dr. Gyanendra K. Sharma, noninvasive cardiologist and study co-author.
With a cervical spinal cord injury, the function of the sympathetic nervous system – called the fight-or-flight system because it responds to stress by increasing the heart rate – can be injured or lost while the impact of the parasympathetic system continues, he said.
The result can be a dangerously slow heart rate, said Dr. Vincent J.B. Robinson, nuclear cardiologist and study co-author.
Treatment includes drugs such as atropine and epinephrine to increase heart rate and a transcutaneous pacemaker on the chest.
The researchers’ retrospective survey of 75 spinal cord injury patients at MCG Medical Center from January 2001-July 2003 included six with high cervical injuries, three of whom needed a permanent pacemaker.
It suggests transvenous pacing – inserting a lead into the heart – may be a better first alternative for heart rate imbalances soon after a spinal cord injury.
“Nobody really knows the best therapy,” said Dr. Sharma. “This gives us some direction that if you see a very slow heart rate, if the patient’s heart is stopping for three, four or five seconds, you [consider] putting in a transvenous pacemaker and maybe put a permanent pacemaker in sooner rather than later.”
Although virtually all cervical spinal cord injuries cause heart rate problems temporarily, some patients even with severed cords will not need a permanent pacemaker, Dr. Ruiz-Arango said.
That’s one reason spinal cord patients with heart rate problems sometime receive the least-invasive options.
Other reasons include the infection risk of transvenous pacemakers and the difficulty of lead insertion in a neck secured because of a spinal injury
“What doctors usually do is put a transcutaneous pacer on the chest and just kind of ride it out,” said Dr. Robinson. “But what we found by going over these patients’ data was that external pacemakers do not seem to be reliable in these patients and patients run into a lot of problems.”
Activities such as having secretions suctioned and blood drawn – or even moving the bowels – can trigger the vagus nerve, disrupting the parasympathetic system.
One patient’s heart stopped beating and he had a seizure when blood was drawn, Dr. Robinson noted. “We put a pacemaker in and he has been fine ever since,” he said. “These patients have lost their sympathetic response so the vagal tone is always predominating. In patients showing ongoing symptoms, we found it’s much more important to go ahead and put that transvenous pacemaker in and keep them stable.”
While the researchers suggest rapid action for recurring episodes of bradycardia, the limited number of patients in their study precludes strict treatment guidelines, the researchers say.
They have begun a larger study at the 60-bed spinal cord injury unit at Augusta’s Veterans Affairs Medical Center.