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

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).

Study Overview

• Status: Completed
• Conditions: Acute Myocardial Infarction
• Intervention / Treatment: Device: Transcutaneous electrical nerve stimulation

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 Type: Interventional
• Enrollment (Actual): 38
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Brazil
  • Rio Grande do Sul
    • Porto Alegre, Rio Grande do Sul, Brazil, 90035-007
      • Hospital de Clínicas de Porto Alegre

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 48 years to 70 years (Adult, Older Adult)
• Accepts Healthy Volunteers: No
• Genders Eligible for Study: All

Description

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 Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Triple

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: TENS CABG; 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.	Device: Transcutaneous electrical nerve stimulation; Patients will be treated with conventional TENS (ENDOMED 684 Device, ENRAF-Nonius B.V., Rotterdam, Netherlands) for 5 days (4 times/day; 30 min/session) applied on cervical region (C7-T4). TENS intervention was applied as described elsewhere.; Other Names: TENS; electrical stimulation
Placebo Comparator: P-TENS CABG; 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).	Device: Transcutaneous electrical nerve stimulation; Patients will be treated with conventional TENS (ENDOMED 684 Device, ENRAF-Nonius B.V., Rotterdam, Netherlands) for 5 days (4 times/day; 30 min/session) applied on cervical region (C7-T4). TENS intervention was applied as described elsewhere.; Other Names: TENS; electrical stimulation

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Blood flow redistribution - baseline and 5 days later	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.	1 day

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Inspiratory and Expiratory Muscle Function	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.	5 day

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Pain Intensity	A visual analog scale (VAS) for assessing current pain intensity will be used to evaluate pain from 0 to 10, where 0 means no pain and 10 indicates severe pain, being applied on the first and on the 5th day after CABG .	5 day
Opioid Analgesic Amount	During the first 24 h (immediately, 6, 12 and 24 h) after CABG, the amount of additional analgesic dose (pethidine hydrochloride (HCl) 20 mg, maximum 1 mg/kg/day) was measured for patients in both groups.	5 day
β-Endorphin Analysis	Ten milliliters of venous blood will be taken by the phlebotomist. 3 ml of which will be stored in ethylenediaminetetraacetic acid (EDTA) for analysis of a differential white cell count. Seven ml of blood will be divided between an EDTA tube and a lithium heparin (LH) gel tube. These blood samples will be centrifuged and frozen until assayed. β-endorphin was measured by sandwich enzyme immunoassay (ELISA) kit (Phoenix Pharmaceuticals, Inc., USA).	5 day

Collaborators and Investigators

• Sponsor: Hospital de Clinicas de Porto Alegre
• Collaborators: University of Brasilia; Hospital Sao Joao
• Investigators: Principal Investigator: Gaspar R Chiappa, Dr, ScD, Federal University of Rio Grande do Sul

Study record dates

Study Major Dates

• Study Start: March 1, 2013
• Primary Completion (Actual): October 1, 2013
• Study Completion (Actual): October 1, 2013

Study Registration Dates

• First Submitted: January 23, 2013
• First Submitted That Met QC Criteria: January 28, 2013
• First Posted (Estimate): January 29, 2013

Study Record Updates

• Last Update Posted (Estimate): November 8, 2013
• Last Update Submitted That Met QC Criteria: November 7, 2013
• Last Verified: November 1, 2013

More Information

Terms related to this study

• Keywords: exercise; exercise capacity; neuromodulation; blood flow
• Additional Relevant MeSH Terms: Ischemia; Pathologic Processes; Necrosis; Myocardial Ischemia; Heart Diseases; Cardiovascular Diseases; Vascular Diseases; Myocardial Infarction; Infarction
• Other Study ID Numbers: 12-0317