Transcutaneous Electrical Nerve Stimulation Improves Vascular Conductance After Coronary Artery Bypass Graft Surgery

Not Applicable

Completed

• Conditions: Acute Myocardial Infarction
• Interventions: Device: Transcutaneous electrical nerve stimulation

• Registration Number: NCT01777659
• Lead Sponsor: Hospital de Clinicas de Porto Alegre

Brief Summary

The investigators will test the hypothesis that transcutaneous electrical nerve stimulation (TENS) may attenuate peripheral vasoconstriction and to improve blood flow redistribution during handgrip exercise in acute myocardial infarction (AMI) patients after Coronary Arterial Bypass Graft Surgery (CABG).

Detailed Description

Thirty-eight patients will be randomized to a (4 times/day; 30 min/session) for 5-day program of TENS (n = 20) or to placebo-TENS (P-TENS, n = 18) applied on cervical region (C7-T4). Acute sympathetic stimulation by cold pressor test (CPT), Maximal voluntary contraction (MVC), Femoral blood flow (FBF) and femoral vascular conductance (FVC) will be measured as primary outcome pre and post-CABG, even as the 6-minute walk test (6-MWT), Inspiratory and expiratory muscle strength (PImax and PEmax) and β-endorphin as a secondary clinical parameters. In addition, amount of opioid analgesic and pain intensity also will be measured throughout at first 24 hours after CABG (immediately, 6, 12 and 24 hours).

Study Timeline

• Study First Submitted: 2013-01-23
• Study First Submitted QC: 2013-01-28
• Study First Posted: 2013-01-29
• Study Start: 2013-03
• Primary Completion: 2013-10
• Study Completion: 2013-10
• Status Verified: 2013-11
• Last Update Submitted: 2013-11-07
• Last Update Posted: 2013-11-08

Recruitment & Eligibility

• Status: COMPLETED
• Sex: All
• Target Recruitment: 38

Inclusion Criteria

• a previous history of more than 1 vessel coronary artery disease,
• lifelong abstinence from tobacco, and
• formal indication for CABG, according to established guideline.

Exclusion Criteria

• Patients older than 70 years of age, with chronic renal failure, or with unstable angina in the 48 h prior to CABG, moderate or severe valve disease, complex cardiac arrhythmias, stroke, and/or inability to exercise the lower limbs.

Study & Design

• Study Type: INTERVENTIONAL
• Study Design: PARALLEL

Arm && Interventions

Group	Intervention	Description
TENS CABG	Transcutaneous electrical nerve stimulation	Eligible patients will be randomized to a transcutaneous electrical nerve stimulation program (TENS; n = 20) or to placebo-TENS (P-TENS; n = 18). All patients were followed by their own physicians, received routine nursing assistance, and were visited daily by one of the investigators, but P-TENS group will be not exposed to any specific electrical stimulation or motor physical intervention.
P-TENS CABG	Transcutaneous electrical nerve stimulation	Patients will be treated with placebo-TENS (P-TENS) condition for 5 days (4 times/day; 30 min/session) applied on cervical region (C7-T4). P-TENS device underwent modifications in its internal programming: the control capacitor of the time constant was changed and the active time between pulses was modified from 330 milliseconds to 33 seconds, in order to prevent an analgesic effect (33).

Primary Outcome Measures

Name	Time	Method
Blood flow redistribution - baseline and 5 days later	1 day	The ultrasound Doppler system will be equipped with two linear array transducers operating at an imaging frequency of 7- 8 megahertz (MHz). The common femoral artery of the left leg will be insonated distal to the inguinal ligament, 2-3 cm proximal to the bifurcation. Using femoral artery diameter and mean blood velocity (MBF), femoral blood flow (FBF) was calculated as MBF π x (vessel diameter/2)2 x 60. Femoral vascular resistance (FVR) and femoral vascular conductance (FVC) were calculated as (MBP/FBF) and (FBF/MBP \* 100 mm Hg), the conductance multiplied by 100 mmHg so that the conductance units will be similar to the units of femoral blood flow (10, 45). The magnitude of reduction FVC (expressed in %) was calculated as vascular conductance during exercise (% change) - conductance at rest (% change) expressed by % of baseline.

Secondary Outcome Measures

Name	Time	Method
Inspiratory and Expiratory Muscle Function	5 day	Inspiratory and expiratory muscle strength testing were performed using a pressure transducer (MVD-500 V.1.1 Micro Hard System, Global Med, Porto Alegre, Brazil). Maximal inspiratory (PImax), and maximal static expiratory pressure (PEmax) were measured as previously described.

Trial Locations

Locations (1)

Hospital de Clinicas de Porto Alegre; 🇧🇷 Porto Alegre, Rio Grande do Sul, Brazil