Acute MI and ventricular tachycardia are closely related entities.In fact , the earliest response to ischemia could be a VT .But what is peculiar about this VT is, it almost always degenerates into VF within a minute or so.(Unlike idiopathic VTs /RVOT/LVOT VTs)
This arrhythmia in every sense can be called as “primary VT“ which is the cause for “primary VF”
It is strongly believed VF cannot occur without a brief episode of VT preceding it .Logic would also suggest the ischemic myocardium can not suddenly become chaotic “with the first beat “. There is little documentation available to unprove this presumption.
In spite of this intimate relationship between VT and STEMI , it is very rare for a STEMI patient to enter ER with a sustained stable ventricular tachycardia . While many VTs are known for it is hemodyanmic stability and immunity against degeneration into VF , it is extremely rare for VT to remain as VT in acute STEMI.
*Note : NSVT can be common in hospitalised patient in the coronary care unit . In our experience a sustained VT in STEMI will enter the VF mode within 60 seconds .If not , it is a highly unusual phenomenon .
“But surprise is the other name of medicine ”
Here is case report, a patient walked into coronary care unit with sustained( relatively stable) VT with LBBB morphology .We thought it was a non- ischemic VT (cardiomyopathy , RVOT etc) .As we were examining him, he became unstable and was shocked 50 J biphasic .To our surprise a classical STEMI was unmasked and he was immediately thrombolysed.
* It is possible , the patient had suffered a old MI which got infarcted again and the VT was scar mediated .
But it is still uncommon for it not to degenerate into VF with fresh STEMI
Final message
Nearly all episodes of ventricular tachycardia , that occur in the early minutes/ hours of STEMI would degenerate into VF.This includes VTs that occur within the CCU . Most of the times , the CCU physicians and staffs revert this VT promptly and deny the ventricles from performing the dance of death !
It is extremely rare for an acute ischemic VT associated with STEMI to walk in to the hospital, which our patient did !
Further reading and unanswered questions
- What determines a VT to degenerate into VF ?
- Why macro-reentrant , scar dependent VTs often are well tolerated ? ( In spite of LV dysfunction !)
Dr.S.Venkatesan MD 