Introduction:
Short QT syndrome (SQTS) is a very rare genetic disease of the electrical system of the heart which is associated with an increase risk of abnormal cardiac rhythms and sudden cardiac death. First described in 2000 with the first genetic mutation associated with SQTS described in 2004. We present a case of Short QT syndrome in a 53 year old male.
Case:
A 53 year old male with a PMH of HTN, alcohol abuse, and tobacco dependence presented to the ED with palpitations. Patient endorsed that he was in his usual state of health the day prior to arrival. He went to bed after drinking alcohol and woke up suddenly pale and diaphoretic with dyspnea and a persistent feeling of impending doom. On arrival to the ED, he was tachypneic (26 breaths/min) with a heart rate of 163 bpm and a blood pressure of 100/80 mmHg. EKG showed atrial fibrillation with RVR. The patient converted to normal sinus rhythm after one dose of IV Cardizem 10 mg was administered for rate control. The next day he had multiple episodes of Torsades de Pointe and monomorphic ventricular tachycardia treated with synchronized cardioversion, 2g of magnesium, IV amiodarone and lidocaine drip. He was transferred to the ICU for further evaluation and monitoring. Repeat EKG showed normal sinus rhythm at 75 bpm and short QT (QT= 328). TTE showed normal biventricular size and function (LVEF 60-65%) with no valvular abnormalities. Dual chamber Implantable Cardioverter Defibrillator (ICD) was placed and outpatient genetic testing was scheduled.
Discussion:
SQTS is very rare with roughly 70 cases identified worldwide since the condition was discovered in 2000. It is a congenital channelopathy related to potassium channels and represented by a normal heart rate with accelerated cardiac repolarization. Normal QT range is 350-440 msec while SQTS range is 210-340 msec. Mutations in the
KCNH2, KCNJ2,
or
KCNQ1
genes lead to enhanced flow of potassium ions across the membrane of cardiac muscle cells. Patients can present at any age with palpitations, syncope, atrial fibrillation, and sudden cardiac death. The cornerstone to diagnosing SQTS is an electrocardiogram. Patients with SQTS can be managed with ICD implantation, quinidine (especially with KCNH2 mutation), and sotalol (with other mutations other than KCNH2).
Heart rate dynamics distinguish among atrial fibrillation, normal sinus rhythm and sinus rhythm with frequent ectopy
