Anteroposterior Versus Anterolateral Electrode Position for Electrical Cardioversion of Atrial Fibrillation (SHOCK-VECTOR)

May 8, 2025 updated by: Omar Ibrahim, McMaster University

A Randomized Controlled Trial of Anterior-posterior Versus Anterior-lateral Shock Vectors for Electrical Cardioversion of Atrial Fibrillation

Atrial fibrillation is the most common heart rhythm disorder (arrhythmia) worldwide. Nearly 40 million people are affected by atrial fibrillation worldwide, and this number is expected to increase by over 50% by 2050. Atrial fibrillation can cause strokes, heart attacks, heart failure, poor quality of life and even death. Almost half a million deaths worldwide are expected to be related to atrial fibrillation by 2050, and many billions of dollars are spent on atrial fibrillation related healthcare in North America every year.

We believe health outcomes for patients with atrial fibrillation, and healthcare costs associated with treating atrial fibrillation could be improved by optimizing existing treatments for atrial fibrillation and maximizing the likelihood of restoring normal heart rhythm. This allows them to benefit from lower stroke risk, better heart function, fewer symptoms and increased quality of life. Restoring normal sinus rhythm earlier prevents atrial fibrillation from causing permanent structural damage to the heart that in turn, makes atrial fibrillation intractable. Furthermore, patients in whom initial attempts to control atrial fibrillation are unsuccessful frequently require more medications or invasive catheter ablation procedures which are costly and carry substantial risk.

Electrical cardioversion is the main way physicians restore normal heart rhythm. In this procedure, the heart is "shocked" back into normal rhythm using two electrodes on the chest. Done correctly, this procedure is safe and effective. Many things are known about electrical cardioversion, for example, the best type and amount of electricity to use. What we don't know is the best position of the electrodes on the chest and whether applying direct, physical pressure to the electrodes makes cardioversion more successful. Our prior research suggests that improving positioning and applying pressure may improve cardioversion, but this finding needs to be verified with a rigorous, dedicated trial.

This study will demonstrate whether front-to-back, or front-to-side placement of the electrodes is more effective for electrical cardioversion of atrial fibrillation. We will also demonstrate whether manually applying pressure to the electrodes makes cardioversion more effective. Should our trial demonstrate a benefit for these techniques, we expect them to be universally applied around the world. Because hundreds of thousands of cardioversions are done each year, even small increases in cardioversion success means thousands fewer patients progress to needing more medications or invasive procedures to manage their atrial fibrillation.

We will study consenting adults presenting for non-urgent cardioversion of their atrial fibrillation. After explaining the study to participants and gaining their consent, we will randomly assign them to front-to-side or front-to-back electrode placement. Patients who remain in atrial fibrillation after the first shock will randomly receive either manual pressure or not. We will compare the success of cardioversion for front-side versus front-back electrode placement, and for manual pressure versus none. We will evaluate success by using electrocardiograms to assess for restoration of the heart rhythm back to normal.

We hypothesize that anterolateral electrode positioning is superior to anteroposterior electrode positioning. We also hypothesize that manual pressure is effective relative to none, when applied in patients who have had one unsuccessful shock already.

Study Overview

Status

Status

Indicates the current recruitment status or the expanded access status.
Recruiting

Conditions

Conditions

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Intervention / Treatment

Intervention / Treatment

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Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Interventional

Enrollment (Estimated)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
1500

Phase

Phase

The stage of a clinical trial studying a drug or biological product, based on definitions developed by the U.S. Food and Drug Administration (FDA). The phase is based on the study's objective, the number of participants, and other characteristics. There are five phases: Early Phase 1 (formerly listed as Phase 0), Phase 1, Phase 2, Phase 3, and Phase 4. Not Applicable is used to describe trials without FDA-defined phases, including trials of devices or behavioral interventions.
  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact

The name and contact information for the person who can answer enrollment questions for a clinical study. Each location where the study is being conducted may also have a specific contact, who may be better able to answer those questions.

Study Locations

  • Canada
    • Ontario
      • Hamilton, Ontario, Canada, L8L2X2
      • Hamilton, Ontario, Canada, L8N4A6

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

Ages Eligible for Study

18 years and older (Adult, Older Adult)

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

Consenting adult patients scheduled for non-emergent electrical cardioversion of Atrial Fibrillation or Flutter

Exclusion Criteria:

  1. Insufficiently anticoagulation for cardioversion as per Canadian Cardiovascular Society guidelines or have not undergone trans-esophageal echocardiography to rule out left atrial thrombus
  2. Anatomic contraindication to anterolateral or anteroposterior placement (e.g. skin conditions or wounds)

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm

Participant Group / Arm

A group or subgroup of participants in a clinical trial that receives a specific intervention/treatment, or no intervention, according to the trial's protocol.
Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.
Active Comparator: Anterolateral shock vector

Patients with electrodes placed on the chest to obtain an anterolateral (front-to-side placement; also known as anteroapical) shock vector.

If first shock is unsuccessful, participants who proceed to a second shock will be randomized to manual pressure versus none but electrode placement will remain the same.
Other: Anterolateral electrode position
As described previously
Other: Manual pressure
Manual pressure applied to the anterior electrode
Active Comparator: Anteroposterior shock vector

Patients with electrodes placed on the chest to obtain an anteroposterior (front-to-back placement) shock vector.

If first shock is unsuccessful, participants who proceed to a second shock will be randomized to manual pressure versus none but electrode placement will remain the same.
Other: Manual pressure
Manual pressure applied to the anterior electrode
Other: Anteroposterior electrode position
As described previously

What is the study measuring?

Primary Outcome Measures

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
Outcome Measure
Measure Description
Time Frame
First-shock cardioversion success
Time Frame: At time of intervention
Reversion to sinus rhythm (5 consecutive P waves within 5 seconds of shock)
At time of intervention

Secondary Outcome Measures

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
Outcome Measure
Measure Description
Time Frame
Cumulative cardioversion success for anterolateral versus anteroposterior placement afte
Time Frame: At time of intervention
Reversion to sinus rhythm (5 consecutive P waves within 5 seconds of shock)
At time of intervention
Second shock success for manual pressure versus none
Time Frame: At time of intervention
Reversion to sinus rhythm (5 consecutive P waves within 5 seconds of shock)
At time of intervention

Other Outcome Measures

Other Outcome Measures

For clinical trials, a planned measurement described in the protocol that is used to determine the effect of an intervention/treatment on participants. For observational studies, a measurement or observation that is used to describe patterns of diseases or traits, or associations with exposures, risk factors, or treatment. Types of outcome measures include primary outcome measure and secondary outcome measure.
Outcome Measure
Measure Description
Time Frame
Descriptive analysis of techniques and results for third, unrandomized, clinician directed shock
Time Frame: At time of intervention
Reversion to sinus rhythm (5 consecutive P waves within 5 seconds of shock)
At time of intervention
First shock cardioversion success (subgroup analysis) by electrode position
Time Frame: At time of intervention
As above; exploratory subgroup analysis of: Males vs females, BMI > 30 vs BMI < 30, First episode atrial fibrillation versus recurrent, Duration of current episode >30 days vs <30 days, Left ventricular ejection fraction > 40% vs <40%, Left atrial volume index >34ml/m2 vs not, Premedication with amiodarone , sotalol or class 1 antiarrhythmic drugs versus not, History of cardiac surgery versus not
At time of intervention
Second shock cardioversion success by manual pressure versus none
Time Frame: At time of intervention
As above; exploratory subgroup analysis of: Males vs females, BMI > 30 vs BMI < 30, First episode atrial fibrillation versus recurrent, Duration of current episode >30 days vs <30 days, Left ventricular ejection fraction > 40% vs <40%, Left atrial volume index >34ml/m2 vs not, Premedication with amiodarone , sotalol or class 1 antiarrhythmic drugs versus not, History of cardiac surgery versus not
At time of intervention
Total number of shocks by electrode positioning
Time Frame: At time of intervention
Reversion to sinus rhythm (5 consecutive P waves within 5 seconds of shock)
At time of intervention

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
McMaster University

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
February 22, 2023

Primary Completion (Estimated)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
June 1, 2027

Study Completion (Estimated)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
July 1, 2027

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
August 19, 2022

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
August 19, 2022

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
August 23, 2022

Study Record Updates

Last Update Posted (Actual)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
May 14, 2025

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
May 8, 2025

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
May 1, 2025

More Information

Terms related to this study

Additional Relevant MeSH Terms

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant numbers.
  • 14093

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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