Thomas V. McDonald, M.D.
Professor of Medicine (Cardiology)
Professor of Molecular Pharmacology
Albert Einstein College of Medicine
Attending Cardiologist, Department of Medicine
Montefiore Medical Center
Co-director, Montefiore Einstein Cardiogenetics Clinic
Potassium is a key heart-rhythm regulator: it creates the
right environment for the electrical “spark” that triggers the heartbeat. In a
cocaine user who died suddenly, Dr. McDonald and his colleagues discovered a
genetic mutation (called KCNQ1-S277L) that disrupted the heart’s potassium
balance and thus its ability to carry electrical current. In another
sudden-death victim, an obese patient who had undergone stomach banding and was
having trouble keeping liquids and solids down, they found a different genetic
mutation (called G816V HERG). Both mutations caused a dangerous condition
called Long QT Syndrome (LQTS), in which the heartbeat’s QT interval is
delayed.
For people with LQTS, the first sign of trouble may be a
fatal heart arrhythmia. But detecting the genetic defect early can alter that
script. In both cases, Dr. McDonald’s team found the same mutations in some
family members. The team prescribed medication and counseled these people on
living with their disorder. The case studies were described in 2011 and 2012
issues of Pacing and Clinical Electrophysiology.