Brain natriuretic peptide and biomarkers of myocardial ischemia increase after defibrillation threshold testing

During implantable cardioverter defibrillator insertion, induced ventricular fibrillation followed by test shocks (defibrillation threshold testing [DFT]) is utilized to confirm effective device function. The effect of DFT on ventricular function is uncertain. Brain natriuretic peptide (BNP) is a marker of ventricular dysfunction and hemodynamic stress. We hypothesized that DFT causes increased BNP levels.

BNP, creatine kinase, creatine kinase-MB (CK-MB), and troponin I (cTnI) were measured in 31 patients (mean age 71.4 years; 12 women) at preinsertion (T1), at 2-4 hours (T2), and at 8-12 hours (T3) after DFT. Biomarker levels were compared in patients receiving one shock (Group A) or two shocks (Group B).

After DFT all biomarkers increased above baseline levels but did not reach levels diagnostic for myocardial infarction. From T1 to T2, elevations in CK-MB and cTnI occurred in the highest proportion of patients (CK-MB 90% and cTnI 84%). From T1 to T3, elevation in BNP and cTnI were most prevalent (BNP 83% and cTnI 90%). Significant increases were measured in BNP levels from T1 to T3 (P = 0.0003), CK-MB levels from T1 to T2 (P < 0.0001), and cTnI levels from T1 to T2 (P < 0.0001) and from T1 to T3 (P < 0.0001). CK-MB levels did not increase significantly from T1 to T3 (P = 0.51).

BNP levels rise progressively after DFT accompanied by early CK-MB increases and sustained increases in cTnI. These data suggest that DFT is associated with hemodynamic stress and left ventricular dysfunction, as evidenced by increases in BNP.