Genetic predisposition and cellular basis for ischemia-induced ST-segment changes and arrhythmias.
Recent reports have highlighted the importance of a family history of sudden death as a risk for ventricular fibrillation (VF) in patients experiencing acute myocardial infarction (AMI), pointing to the possibility of a genetic predisposition. This report briefly reviews 2 recent studies designed to examine the hypothesis that there is a genetic predisposition to the development of arrhythmias associated with AMI. Ventricular tachycardia and VF (VT/VF) complicating AMI as well as arrhythmias associated with Brugada syndrome, a genetic disorder linked to SCN5A mutations, have both been linked to phase 2 reentry. Because of these mechanistic similarities in arrhythmogenesis, we examined the contribution of SCN5A mutations to VT/VF complicating AMI in patients developing VF during AMI. A missense mutation in SCN5A was found in a patient who developed an arrhythmic electrical storm during an evolving myocardial infarction. All VT/VF episodes were associated with ST-segment changes and were initiated by short-coupled extrasystoles. G400A mutation and H558R polymorphism were on the same allele, and functional expression in TSA201 demonstrated loss of function of sodium channel activity. These results suggest that a subclinical mutation in SCN5A resulting in a loss of function may predispose to life-threatening arrhythmias during acute ischemia. In another cohort of patients who developed long-QT intervals and torsade de pointes arrhythmias in days 2 to 11 after an AMI, a genetic screening of all long-QT genes was performed. Of 8 patients in this group, 6 (75%) displayed the same polymorphism in KCNH2, which encodes the alpha-subunit of the rapidly activating delayed rectifier potassium current, I(Kr). The K897T polymorphism was detected in only 3 of 14 patients with uncomplicated myocardial infarction and has been detected in 33% of the white population. Expression of this polymorphism has previously been shown to cause a loss of function in HERG current consistent with the long-QT phenotype. These observations suggest a genetic predisposition to the development of long-QT intervals and torsade de pointes in the days after an AMI. These preliminary studies provide support for the hypothesis that there is a genetic predisposition to the type and severity of arrhythmias that develop during and after an AMI, and that additional studies are warranted.
Hu
Dan
D
Masonic Medical Research Laboratory, Utica, NY, USA.
Viskin
Sami
S
Oliva
Antonio
A
Cordeiro
Jonathan M
JM
Guerchicoff
Alejandra
A
Pollevick
Guido D
GD
Antzelevitch
Charles
C
D001145:Arrhythmias, Cardiac / Q000175:diagnosis* / Q000235:genetics*; D004252:DNA Mutational Analysis; D005260:Female; D005819:Genetic Markers / Q000235:genetics; D020022:Genetic Predisposition to Disease / Q000235:genetics; D006801:Humans; D008133:Long QT Syndrome / Q000175:diagnosis / Q000235:genetics; D008297:Male; D008875:Middle Aged; D009124:Muscle Proteins / Q000235:genetics*; D009154:Mutation; D017202:Myocardial Ischemia / Q000175:diagnosis* / Q000235:genetics*; D062554:NAV1.5 Voltage-Gated Sodium Channel; D020641:Polymorphism, Single Nucleotide / Q000235:genetics*; D015222:Sodium Channels / Q000235:genetics*
D005819:Genetic Markers; D009124:Muscle Proteins; D062554:NAV1.5 Voltage-Gated Sodium Channel; C568320:SCN5A protein, human; D015222:Sodium Channels