Influence of left ventricular hypertrophy on scar identification during bipolar voltage mapping

Bipolar endocardial signal amplitude (BESA) <1.5 mV defines scar in the left ventricle (LV). It is not known if LV hypertrophy (LVH) increases overall bipolar signal amplitude and if scar identification with LVH requires a higher voltage cutoff.

We compared the LV BESA of four patients with moderate LVH on echo (≥1.6 cm) to that of ten consecutive patients with no LVH with both groups having normal systolic function and no scar. Additionally, in 12 patients with ischemic scar (ICM) and moderate LVH (≥1.6 cm), we assessed scar area and percent abnormal electrograms (width >80 ms and/or split/fractionated) using 1.5 and 2.5 mV defined border zone cutoff values and compared results to those from 12 ICM patients with no LVH matched for age, sex, scar distribution, and LV ejection fraction.

Average BESA in the setting of normal systolic function/no scar was comparable in patients with (4.7 ± 3.0 mV, 95% signals >1.58 mV) and those without LVH (4.9 ± 1.6 mV, 95% signals >1.62 mV). In patients with ICM and LVH versus without LVH, there was a smaller area of dense scar <0.5 mV/total scar (15% versus 23%, p = 0.03) but no significant difference in the size of the border zone, or percentage of abnormal electrograms identified within border zones defined by either the 0.5-1.5 mV or 0.5-2.5 mV cutoff values.

Patients with and without LVH with normal systolic function show similar LV endocardial bipolar signal characteristics. Modifying the bipolar amplitude cutoff at the infarct border zone did not increase overall scar size in patients with versus those without LVH. A 1.5 mV-bipolar voltage cutoff used for scar definition seems appropriate even in patients with marked LVH.