External pacing, also known as transcutaneous pacing, is a temporary medical procedure that regulates a patient’s heart rate. It involves delivering controlled electrical impulses through the chest wall to stimulate the heart. This non-invasive method serves as a bridge to more definitive treatments, helping stabilize individuals when their heart’s natural electrical system is compromised. It aims to maintain adequate heart function and blood circulation until the underlying cause of the heart rhythm disturbance can be addressed.
How External Pacing Works
External pacing uses an external pulse generator and two large adhesive pacing pads, or electrodes, placed on the patient’s chest. These pads are connected to a monitor/defibrillator device, which generates and delivers electrical current through the skin. The electrical impulses travel through the chest wall to the heart muscle, stimulating it to contract.
The anterior/posterior pad placement, where one pad is on the front of the chest and the other on the back, is often preferred as it helps minimize electrical resistance across the chest. The device settings allow medical professionals to select a desired heart rate, between 60 to 80 beats per minute, and adjust the current measured in milliamps (mA). The current is gradually increased until the heart consistently responds to each electrical impulse, a phenomenon known as “electrical capture,” observed on an electrocardiogram (ECG) as a QRS complex following each pacing spike.
When External Pacing Is Used
External pacing is employed in emergency scenarios where a patient experiences symptomatic bradycardia. It is used when the heart rate falls below 60 beats per minute and causes symptoms of shock, such as low blood pressure or fainting. It is also indicated for certain types of heart block, like third-degree AV block or Mobitz type II second-degree heart block, particularly when these conditions lead to hemodynamic instability.
The procedure serves as a temporary measure to stabilize the patient, allowing time for medical staff to identify and treat the underlying cause. While external pacing can be a life-saving intervention, it is not a long-term solution. It provides support until a more permanent treatment, such as a transvenous pacemaker, can be implemented.
What to Expect During External Pacing
During external pacing, patients may experience muscle twitching or discomfort in the chest area. This discomfort arises from the electrical impulses stimulating not only the heart but also the surrounding chest wall muscles. The sensation can range from a mild tingling to painful muscle contractions.
To manage this discomfort, pain medication or sedation may be administered, especially if prolonged pacing is anticipated. Medical staff continuously monitor the patient’s heart rate and rhythm using an ECG, along with other vital signs like blood pressure, to ensure the pacing is effective and the patient is stable. Observing a palpable pulse with each paced beat confirms that the heart is mechanically responding to the electrical impulses.
Risks and Post-Procedure Considerations
While external pacing is an emergency intervention, it carries potential risks and complications. Skin irritation or burns can occur at the sites where the pacing pads are applied, especially with prolonged use. Muscle soreness in the chest area is also a common complaint due to the continuous electrical stimulation.
There is also a possibility of “failure to capture,” meaning the heart does not respond adequately to the electrical impulses, which might require adjusting the current or repositioning the pads. Once external pacing is no longer required, the patient may transition to an internal pacemaker. Regular skin inspection beneath the pads is advised if pacing extends beyond 30 minutes to minimize the risk of skin damage.