Friday, October 23, 2015

Measurement of ventricular repolarization dispersion in chest pain

Although the authors of this paper, for purposes of discussion, use the generally accepted term “NSTEMI” in reference to acute coronary syndrome with subtle or non diagnostic ECG patterns, their findings suggest that the term is simplistic and of limited clinical usefulness.  Utilizing a specialized electrocardiographic technique to measure ventricular repolarization dispersion in  patients presenting with chest  pain they found:

Methods and Results We continuously recorded 12‐lead Holter ECGs from chest pain patients upon their arrival to the ED. VRD was quantified using principal component analysis of the 12‐lead ECG to compute a T‐wave complexity ratio (ie, ratio of second to first eigenvectors of repolarization). Clinical outcomes were obtained from hospital records. The sample was composed mainly of older males (n=369; ages 63±12 years; 63% males), and 92 (25%) had NSTEMI and 26 (7%) had MACEs. Baseline T‐wave complexity ratio modestly correlated with peak troponin levels (r=0.41; P less than 0.001) and was a good classifier of NSTEMI events (area under the curve=0.70). An increased T‐wave complexity ratio on the presenting ECG was strongly associated with NSTEMI (odds ratio [OR]=3.8 [2.1 to 5.8]) and in‐hospital MACE (OR=8.2 [3.1 to 21.5]).

Conclusions A simple measure of global VRD on the presenting 12‐lead ECG correlates with ischemic myocardial injury and can discriminate NSTEMI cases very early during evaluation. Prospective studies should validate these findings and test whether VRD can guide therapy.

More from the discussion section of the paper:

As such, our data suggest that a simple measure of T‐wave complexity is more sensitive for (1) detecting ischemic myocardial necrosis associated with NSTEMI and (2) quantifying the severity of ischemic burden to identify high‐risk NSTEMI patients who would benefit from early revascularization.

This paper convinces me more than ever that the STEMI/NSTEMI terminology needs to be abandoned.  If there is a meaningful binary distinction in ACS it would be between coronary occlusion and plaque instability without occlusion.   But the current STEMI/NSTEM designation is, according to increasing evidence and for multiple reasons, a poor surrogate tor presence of absence of occlusion.  Moreover, according to the data presented here, the decision for early cardiac catheterization ought to be based on assessment along a continuum of risk rather than a binary distinction.

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