Chaix MA, Chergui M, Leduc C, Khairy P.
Int J Cardiol. 2019 Feb 14. pii: S0167-5273(18)36331-9. doi: 10.1016/j.ijcard.2019.02.026. [Epub ahead of print]
Select item 30765829
Take Home Points:
- Sudden cardiac death remains a leading cause for mortality in patients with transposition of the great arteries and an atrial switch.
- This study provides evidence for a proposed mechanism: myocardial oxygen mismatch of the systemic RV when atrial rates are high, resulting in ischemia-driven ventricular arrhythmias and sudden cardiac death.
Commentary by Dr. Blanche Cupido (Cape Town), section editor of ACHD Journal Watch: In patients with transposition of the great arteries and an atrial switch repair, sudden cardiac death is the main cause of mortality. The decision making for a primary prevention ICD remains difficult with little evidence to substantiate it. A proposed mechanism for sudden cardiac death in this group is thought to be myocardial oxygen supply mismatch of the systemic RV during high heart rates resulting in ischemia- related ventricular arrhythmias and death. This study provides histopathologic evidence in support of this theory.
This is a retrospective cohort study in Montreal, Canada of adults with transposition of the great arteries with an atrial switch procedure. Patients attending their clinic from 1989 onward were enrolled. Those patients with arterial switches or double outlet RV were excluded.
A total of 140 patients were analyzed. The average age was 37.6 years and 37.1% were female. A total of 8 patients (6% – 3 female, 5 male) had a cardiac arrest (of assumed arrhythmic cause) – three of these were successfully resuscitated. None had a prior history of coronary artery disease, ventricular arrhythmia or syncope.
Four patients had atrial arrhythmias, one had non-sustained VT on a Holter (asymptomatic) and two had pacemakers. Two thirds had at least moderate systemic RV dysfunction. Most patients (7 of 8) had NYHA I or II. For 5 patients, the circumstances around the time of arrest were documented: 3 events occurred on exertion, 1 at rest and 1 after methamphetamine use.
Of the 5 patients who died, 2 autopsies were performed. One patient died suddenly 7 days post -op (tricuspid valve replacement) and the other while walking to work (VT documented). Both had extensive acute necrosis of the hypertrophied systemic RV with normal coronary arteries and chronic subendocardial lesions.
These histopathological findings support the following theory: At rapid heart rates, stroke volume is impaired due to poor atrial contraction. This reduction in stroke volume together with the increased oxygen demand, decreased perfusion pressure and inefficient coronary circulation (systemic RV usually only has single coronary supply), induces ischemic ventricular arrhythmias.