Discussion
In the current study, VTA occurred in roughly 3% of ACS patients admitted to the hospital with the majority (77%) of those arrhythmias occurred during the first 48 hours of ACS. Moreover, the incidence of both early and late VTA did not change significantly during the years 2000-2016, suggesting it was not related to medical treatment.
Previous data on prognostic significance of VTA is controversial. In the HORIZONS-AMI Trial (7) there was no significant difference in MACE and 3-year mortality rate in patients with or without VTA that occurred after primary percutaneous coronary intervention (PCI). Another recent study, found that in patients with STEMI that survived out of hospital cardiac arrest due to VTA and underwent primary PCI, the 1-year mortality was equal to those without out of hospital cardiac arrest (8). On the other hand, in the MILIS study (9) the in hospital mortality rate was significantly increased by VTA, especially late VTA, causing cardiac arrest during ACS hospitalization, although there was no difference in mortality rate in the 32-month follow up as compared with patients with no VTA. In APEX AMI trial (10), pre and post primary PCI VTA were also shown to be associated with significantly increased 90 days mortality. Piccini et al. (11) studied a large population of 9000 patients with STEMI and NSTEMI undergoing PCI. In their study, the rate of early VTA was 5.2% and it was also related to increase mortality risk by 4.4 folds as compared with no VTA. Our data is in accord to the aforementioned trials suggesting that VTA occurrence during the course of ACS is not benign. Short and long-term mortality rate was increased dramatically by the presence of early and especially late VTA as compared with no VTA. This was consistent even after adjustment for multiple confounders. In the logistic regression analysis model the presence of late VTA was associated with 27 folds’ increase of in hospital mortality, 10 folds increased one-year mortality and 8 folds increased 5 years mortality rate. The proposed reason why late VTA carries an increased risk of death might be its association with pump failure and hemodynamic deterioration rather than arrhythmic death (12, 13).
Interestingly, although the overall prognosis of ACS patients improved in the last decade (14) as well as in our study, the most prominent improvement in our study was seen in those who had late VTA, as shown in Figures 3 and 4. Wider use of ACE inhibitors and beta blockers at discharge in the late VTA group, early reperfusion strategy, (15, 16), as well as wider use of implantable and wearable cardioverter defibrillators could explain our findings.