Intermittent versus continuous thoracic spinal cord stimulation for treatment of ischemic heart failure

Abstract

Background: Prior experimental studies showed that spinal cord stimulation (SCS) improved left ventricular (LV) function in animal model of ischemic heart failure (HF). Nevertheless, the optimal approach and duration of thoracic SCS is unknown.

Methods: We performed chronic thoracic SCS at T1-T2 level (50Hz frequency, pulse width 0.2ms) in 30 adult pigs with ischemic HF induced by myocardial infarction (MI) via coronary embolization of left circumflex artery followed by rapid ventricular pacing for 4 weeks (MI+HF). All animals were treated with daily oral metoprolol ZOK (50 mg) plus ramipril (2.5 mg), and randomized into control group (n=10), intermittent SCS (4hrs x3, n=10) or continuous SCS (24hrs, n=10) for 10 weeks. Echocardiogram and invasive hemodynamic assessment to determine LV ejection fraction (LVEF) and +dP/dt, respectively, and blood sampling to measure serum norepinephrine (NE) and B-type natriuretic peptide (BNP) levels as baseline, immediately after MI (post-MI), at MI+HF and at 10wks follow-up.

Results: Echocardiogram showed significant increase in LVEF and +dP/dt at 10 wks in both intermittent SCS group and continuous SCS group as compared with control group (P<0.05, Figure 1). However, there were no significant differences in LVEF and +dP/dt between intermittent vs. continuous SCS group (P>0.05,Figure 1). Nevertheless, only continuous SCS group had significant decreased in serum NE and BNP at 10wks as compared with control group (P<0.05, Figure 2).

Conclusions: In porcine model of ischemic HF, addition of either intermittent or continuous SCS to medical therapy improves LV contractile function compared with medical therapy alone. However, continuous SCS, but not intermittent SCS is associated with significant reduction of serum NE and BNP compared with medical therapy alone.