Study finds deadly heart mutation

WASHINGTON (Reuters) -- Italian researchers said Monday they had discovered a genetic mutation that causes an abnormally fast heart rate that can suddenly kill children at play or under stress.

Several mutations in a single gene can cause the rare and hard-to-diagnose syndrome, known as catacholamineric polymorphic ventricular tachycardia (CPVT). CPVT strikes children during physical exertion or when they feel strong emotions, the team at the University of Pavia said.

"Finding the gene may help identify individuals at risk," Dr. Silvia Priori, who led the study, said in a statement.

Her team looked at the genes of 12 people with CPVT. Knowing that calcium levels are very important to how well cells work, they targeted a gene called human cardiac ryanodine receptor gene (hRyR2). It controls the levels of calcium inside heart cells.

"Patients with CPVT, as a consequence of the mutation in the ryanodine gene, have an increased sensitivity to calcium. Therefore, intense stimulation due to emotional stress or increased physical activity may lead to calcium overload and precipitate severe arrhythmias," Priori said.

They found four different mutations -- each a single nucleotide polymorphism, or a one-letter change in the genetic code. In three cases, the mutations were not inherited from the parents, who had normal cardiac genes.

"None of the mutations was present in DNA obtained from 400 normal subjects," they wrote in the report published in the American Heart Association journal Circulation.

Knowing about the gene could help doctors better diagnose the condition, Priori's team said, because CPVT is hard to diagnose.

The first symptom is often fainting, but the researchers detailed the tragic cases of several children who had died suddenly of CPVT.

Five of the 12 people studied had a family history of fainting or sudden death. In one family studied, two children died -- a 3-year-old with a history of fainting spells and a 7-year-old who died while running.

One 8-year-old boy had repeated fainting episodes and his identical twin died suddenly at age 7.

Another patient was 30 but had two relatives, sisters, who died suddenly. "One of the two girls died while being interrogated at school and the second while climbing stairs," the researchers wrote.

When CPVT is diagnosed, it can be treated with devices such as implantable defibrillators that correct the heartbeat or drugs such as beta-blockers.

But unlike patients with other heart rhythm abnormalities, such as Long QT Syndrome or Brugada Syndrome, CPVT patients have normal results on an electrocardiogram, a test that measures the heart's electrical activity.

Researchers are finding that genetic mutations can be the cause of many heart conditions. Four mutations have been found to be responsible for Long QT Syndrome, which can also cause sudden death during stress.

Copyright 2000 Reuters. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.

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Medical Informatics Laboratory, University of Pavia
eMedicine Online - Ventricular Tachycardia
American Heart Association

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