New Research Prompts Lifesaving Recommendation For Patients With Genetic Heart Disorder
In often-fatal disease that strikes children and young adults, medications alone may not save lives; use of implantable defibrillators urged for high-risk patients
February 15, 2000
In the recent film The Red Violin, there is a heart-stopping moment that leaves audiences shaken. A small boy, a violin prodigy, is about to audition for a prince in Austria's royal family. As they are being introduced, the prince takes notice of the boy's violin. The tension builds as he studies the boy's prized instrument, and then offers to buy it from the boy's guardian. The boy tightens his grip on the violin as his heart races - and a few moments later he suddenly falls to the floor and dies.
Remarkably, about 500 Americans - most of them teenagers - die each year in similar circumstances. They are victims of a genetic heart disorder known as Long QT Syndrome, in which moments of stress or excitement can trigger fainting spells and, in some cases, cardiac arrest. For a child with Long QT Syndrome, landing a speaking part in a school play or sliding to beat a throw at home plate can be fatal.
When patients are diagnosed with the disorder, doctors usually prescribe medications called beta blockers, which block the effects of adrenaline on the heart. Doctors had thought that shielding the heart from adrenaline surges would reduce patients' risk of fainting spells and cardiac arrest, though beta blockers had never been studied for that purpose.
This week, the findings of two research studies funded by the National Institutes of Health are prompting an urgent recommendation to change the treatment of high-risk patients who are the most likely to die from the disorder. The findings suggest that while beta-blocker drugs can greatly reduce the risk of fainting spells, they are woefully ineffective in preventing deaths, while the use of implantable defibrillators may increase a patient's odds of survival to near 100 percent.
In light of the new findings, the nation's leading expert on the disorder is recommending that 1,500 high-risk patients - nearly all of them children, teenagers, and adults under age 30 - receive implantable defibrillators in addition to receiving beta-blocker medications.
"The results show quite clearly that the only way to ensure the survival of these young, high-risk patients is through the use of implantable defibrillators," said Arthur J. Moss, M.D., a research cardiologist at the University of Rochester Medical Center. "Treatment with beta blockers alone does not significantly reduce a patient's risk of dying from this disease."
The recommendation is based on the findings of two studies led by Moss, the first of which appears in the February 15 issue of the journal Circulation. Moss and his coworkers found that the use of beta blockers reduced the number of fainting spells in patients with Long QT Syndrome by more than 70 percent. But the drugs proved to be ineffective in preventing deaths. Twenty-five patients in the study died from cardiac arrest while on beta blockers. The findings were made by studying a database of information collected from 869 patients over a period of several years.
Preliminary data from a companion study also being led by Moss is showing that implantable defibrillators are much more effective in saving the lives of these patients. Moss's team studied 88 patients who were judged to be at high risk of dying from Long QT Syndrome. In addition to receiving beta blockers, all of the patients in the study were outfitted with implantable defibrillators. The small, surgically-implanted devices were programmed so that if the patient's heart stopped for a period of more than 7.5 seconds - indicating that the patient was suffering a cardiac arrest, and not a fainting spell - the defibrillator would deliver an electrical charge to the heart muscle to re-start it.
During a three-year period, 30 patients in the study suffered cardiac arrest. In every case, the implantable defibrillators re-started the patient's heart, and all of the patients fully recovered. The results of this study will be presented at an international cardiology meeting in May, and published later this year.
"These results are remarkable," said Moss. "In this group of patients, we're finding that the use implantable defibrillators is 100 percent effective in saving their lives."
Based on the findings of these two studies, Moss is recommending that some 1,500 high-risk patients with Long QT Syndrome be treated with both beta blockers and implantable defibrillators. Patients who fall in to the high-risk category are those who have been diagnosed with Long QT Syndrome and have suffered a cardiac arrest or have had more than one fainting spell while on beta blockers.
A genetic test is also available that can identify high-risk patients. The test, available at the University of Rochester and four other academic medical centers, analyzes a patient's blood sample for the presence of a defect in the gene called LQT3. Moss led the research team that in 1998 identified the LQT3 gene and two other genes that, when damaged, cause LQT Syndrome.
Patients with Long QT Syndrome appear healthy in every respect - except that, without warning, they can pass out or suffer cardiac arrest. The problem stems from genetically-caused defects in the thousands of tiny channels in the heart muscle that allow electrically-charged ions to flow in and out of cells. When the flow of ions through the channels is slowed or blocked, patients can experience sudden episodes in which the heart muscle becomes unable to contract and pump blood effectively. If the interruption lasts for only a few seconds, the patient may pass out momentarily and then regain consciousness once the heart beat resumes. But if the heart beat is interrupted for 10 seconds or longer, the episode is almost certain to be fatal unless the heart can be re-started by emergency medical personnel.
"We now understand this disease well enough that, if we act aggressively, we can save thousands of lives," said Moss. "We have the ability to identify the patients who are most likely to die from the disease, and we can offer them a treatment that appears to be 100 percent effective in saving their lives."