Cardiac sympathetic denervation the heart’s control from the sympathetic nervous system

Mar 29 2004

Surgery to cut part of the nerves to the heart can reduce the risk of fainting or sudden death in young people with a heart rhythm disorder called long QT syndrome (LQTS), researchers reported in today’s rapid access issue of Circulation: Journal of the American Heart Association.

The 40-minute surgical procedure, called left cardiac sympathetic denervation (LCSD), reduces the heart’s control from the sympathetic nervous system, which is the part of the nervous system responsible for involuntary biological activity such as breathing and heart rate.

“Even in a population of LQTS patients at an especially high risk, denervation surgery reduced syncope (fainting) and cardiac arrest by 91 percent,” said Peter J. Schwartz, M.D., professor and chairman of the Department of Cardiology at the University of Pavia in Italy.

Long QT syndrome is a disorder of the heart’s electrical system.   It can be inherited or acquired.  The syndrome gets its name from a characteristic, markedly elongated QT interval on an electrocardiogram.  People with LQTS are prone to develop an extremely rapid heart rhythm, often brought on by exercise, emotion or loud noise.  This improper rhythm interferes with blood flow to the brain and can result in fainting or cardiac arrest. 

Symptoms usually occur in childhood or early adulthood, and affect otherwise-healthy people.  Symptoms also may appear later in life (often in response to certain medications).  The syndrome also may occur in infancy, and may account for a small percentage of sudden infant deaths.

Beta-blockers can slow the heartbeat and prevent arrhythmias in patients with LQTS.  However, about a fourth of patients continue to experience fainting spells and potentially life-threatening arrhythmias while on the medication, researchers said.  If beta-blockers are ineffective or cause unacceptable side effects, or if a person has already experienced near sudden death, doctors can implant a defibrillator that automatically detects a life-threatening heart rhythm and delivers a shock to allow the heart rhythm to return to normal.  This is the best protection, but some patients experience “storms” of cardiac arrest with multiple shocks, which is frightening and can interfere greatly with quality of life, Schwartz said.

The researchers identified 147 patients (69 percent female) who were average age 17.  They had their first fainting spells at 8 on average and underwent LCSD between 1970 and 2002.  The patients were deemed at high risk because their QT intervals were extremely prolonged and they had experienced a cardiac arrest (48 percent) or continued to have symptoms, despite taking beta-blockers (75 percent).

An average of 7.8 years after surgery, the number of cardiac events per patient per year dropped by 91 percent compared with pre-surgery rates.

During the follow-up period, 46 percent of the patients had no symptoms, 31 percent lost consciousness one or more times, 16 percent had a cardiac arrest, and 7 percent had sudden cardiac death.

“For patients who have a fainting episode while on beta-blockers, LCSD is a valid alternative to the immediate implantation of a defibrillator,” Schwartz said.  “A defibrillator could still be implanted in those who, after surgery, continue to have a prolonged QT interval or who have another recurrence.”

“LCSD is one more option available to patients and physicians in their search for the best, individually tailored therapy.  All advantages and limitations should be weighed and discussed, and it is essential to remind people that with LCSD there is some excess risk for fatal events compared to the implantable cardiac defibrillator.”

In five patients who experienced multiple shocks from their implantable defibrillators, LCSD surgery reduced the average number of shocks from 29.3 to 3.3 per year, according to the report.

“Just imagine what that means for young patients and for their parents who have to helplessly watch during the shocks.  We as physicians should always remember that quality of life, and not only duration, is extremely important,” Schwartz said.