Simultaneous noninvasive recording of electrocardiogram and skin sympathetic nerve activity (neuECG).

neuECG, the simultaneous noninvasive recording of ECG and skin sympathetic nerve activity (SKNA), directly records sympathetic nerve activity over a long period of time. It can be used to measure sympathetic tone in healthy subjects and in subjects with non-cardiovascular diseases. The electrical activity that can be measured on the surface of the skin originates from the heart, the muscle or nerve structures. Because the frequency content of nerve activity falls in a higher frequency range than that of the ECG and myopotential, it is possible to use high-pass or band-pass filtering to specifically isolate the SKNA. neuECG is voltage calibrated and does not require invasive procedures to impale electrodes in nerves and thus has advantages over microneurography. Here, we present a protocol that takes <10 min to set up. The neuECG can be continuously recorded over a 24-h period or longer. We also describe methods to efficiently analyze neuECG from humans using commercially available hardware and software to facilitate adoption of this technology in clinical research.

Cardiac resynchronization therapy modulates peripheral sympathetic activity.

BACKGROUND: Heightened sympathetic nerve activity has been associated with poorer prognosis in patients with reduced left ventricular systolic function (ie, heart failure with reduced ejection fraction [HFrEF]). OBJECTIVE: The purpose of this study was to investigate the effects of cardiac resynchronization therapy (CRT) on sympathetic nerve activity, measured by average skin sympathetic nerve activity (aSKNA). METHODS: This prospective study enrolled 36 patients with HFrEF who received CRT. Ten patients who received an implantable cardioverter-defibrillator for primary prevention served as controls. Patient clinical data, echocardiographic variables, and aSKNA at baseline and 3-month follow-up were collected. RESULTS: CRT patients who exhibited wider QRS duration had higher aSKNA (1.52 ± 0.65 µV vs 0.97 ± 0.49 µV; P = .027) compared to the control group at baseline. In the CRT group, patients with QRS duration ≥150 ms had higher aSKNA than those with QRS duration <150 ms (1.67 ± 0.63 µV vs 1.19 ± 0.51 µV; P =.039). After CRT, left ventricular ejection fraction (LVEF) improved from 29.6% to 35.4% (P = .001). aSKNA decreased significantly (1.52 ± 0.65 µV vs 1.31 ± 0.63 µV; P = .018). Seventeen of the 36 CRT patients were CRT responders, with LVEF improvement ≥5% at 3-month follow-up. aSKNA significantly decreased from 1.47 to 1.15 µV (P = .003) in CRT responders but was unchanged in nonresponders (1.44 ± 0.69 to 1.37 ± 0.70; P = .61). After CRT, a significant reduction in aSKNA was associated with improvement in LVEF (r = 0.638; P = .001). CONCLUSION: CRT reduces elevated sympathetic activity in HFrEF patients, accompanied by improvement in systolic function at short-term follow-up. The reduction of sympathetic activity is mainly seen in CRT responders.