Читать книгу Practical Cardiovascular Medicine - Elias B. Hanna - Страница 134

In the reperfusion era, sustained VF occurs in 4% of patients hospitalized with acute STEMI. There are three types of VF, mostly character- ized in fibrinolytic trials:

 Primary VF is defined as VF occurring in the first 48 hours after MI without an associated shock or severe HF. It occurs because of rapid potassium fluxes with increased automaticity and dispersion of repolarization, or increased sympathetic or vagal tone. It mostly occurs in the first 4 hours. Primary VF, whether in the first 4 hours or at 4–48 hours, is associated with a 2–4 times increased in-hospital mortality, from the VF episode itself, VF recurrence, or the larger ischemic burden. However, VF does not affect long-term mortality in survivors, even on unadjusted analyses.135–137 In fact, primary VF correlates with the extent of initial ischemia and is much more commonly seen in STEMI than NSTEMI, but does not correlate with the eventual infarct size and is at least as frequently seen in inferior as in anterior MI (GISSI-2, Apex-AMI analyses). Sinus bradycardia or pauses may precipitate VF in patients with inferior MI.Even after primary PCI, a small but significant proportion of patients have VT/VF at 24–48 hours (~1.5% of patients).138,139 This post-PCI VT/VF carries an increase in short-term,¹³⁹ but not long-term, mortality.

Post-PCI VF may reflect stent thrombosis and warrants thorough clinical and ECG investigation.

 Secondary VF is defined as VF occurring in association with HF or shock (<48 h or >48 h) and portends a poor early and long-term survival, mainly from a downhill HF course.136,137

 Late VF is defined as VF occurring after 48 hours without an associated HF or shock. It is secondary to the myocardial scar and correlates with pump failure, extensive myocardial damage, and increased long-term mortality.¹³⁵