Transcutaneous pacing is a temporary, life-saving intervention used to manage severe disturbances in heart rhythm, particularly those causing a dangerously slow heart rate. This procedure uses external electrical impulses delivered through the skin to stimulate the heart muscle to contract. The goal is to quickly restore a minimum heart rate that can sustain blood flow to the body’s organs. This temporary, non-invasive method serves as a bridge until a more permanent treatment, such as a surgically implanted pacemaker, can be arranged.
What Transcutaneous Pacing Is
Transcutaneous pacing (TCP) is a non-invasive technique that utilizes a monitor/defibrillator device to deliver electrical energy through two large electrode pads placed on the patient’s skin. These electrical pulses travel through the chest wall to the myocardium, or heart muscle, forcing it to depolarize and contract.
The electrical impulse is measured in milliamperes (mA) and must be strong enough to pass through the skin, fat, and muscle to reach the heart. The core purpose of TCP is to restore a minimum effective heart rate, typically between 60 and 80 beats per minute, to maintain adequate blood circulation. TCP differs from a permanent pacemaker, which uses small wires threaded directly into the heart chambers to deliver precise, low-energy impulses.
When Emergency Pacing Is Necessary
Emergency pacing is indicated when a patient experiences symptomatic bradycardia—an abnormally slow heart rate, generally below 60 beats per minute, that causes signs of poor organ perfusion. These symptoms can include significantly low blood pressure (hypotension), fainting (syncope), altered mental status, or signs of shock. The decision to pace is based on the presence of these symptoms, not just the heart rate alone.
TCP is often initiated when first-line drug treatments, such as atropine, have failed to adequately increase the heart rate and improve the patient’s condition. It is also recommended for high-grade electrical blocks in the heart’s conduction system, such as Type II second-degree or third-degree atrioventricular (AV) blocks, which are less likely to respond to medication.
The Steps of Transcutaneous Pacing
The procedure begins with patient preparation and equipment setup. The skin must be clean and dry, and any transdermal patches or excessive hair should be removed from the electrode sites to ensure good electrical conductivity. The large pacing electrodes are then placed on the patient’s torso, typically in an anterior-posterior configuration, with one pad on the anterior chest and the other on the back, often under the left scapula.
The anterior-posterior placement is generally preferred because it “sandwiches” the heart, minimizing the electrical impedance encountered by the current as it travels through the chest. Alternatively, an anterior-lateral placement may be used if access to the patient’s back is restricted. Once the pads are connected to the monitor/defibrillator device, the machine is set to “Pace” mode.
The provider must set the desired heart rate. Next, the electrical output must be adjusted. The current is slowly increased, starting from a low level, until the monitor displays an electrical capture, which is a wide QRS complex following each pacing spike.
The minimum current required to achieve consistent electrical capture is called the capture threshold. Once the threshold is found, the current is increased by an additional 2 to 10 mA above that level to provide a safety margin and ensure reliable pacing. The current required for capture can vary widely, often falling between 40 and 80 mA, but it may be higher in patients with conditions like emphysema or pericardial effusion.
Evaluating Pacing Success and Patient Comfort
After achieving electrical capture, the next step is to confirm mechanical capture—that the electrical stimulus is causing the heart to contract and pump blood effectively. This is assessed by checking for a palpable pulse, such as the femoral or carotid pulse, that matches the set pacing rate. Checking a central pulse is more reliable than a peripheral pulse, as muscle twitching caused by the electrical current can sometimes be mistaken for a pulse.
If a pulse is felt and the patient’s blood pressure and level of consciousness improve, the pacing is considered successful. However, the electrical current delivered through the skin causes involuntary contractions of the chest wall and skeletal muscles, making the procedure painful for a conscious patient. Therefore, adequate sedation and analgesia, often using medications like midazolam or fentanyl, are necessary to manage the patient’s discomfort and prevent agitation.
Continuous monitoring of the patient’s cardiac rhythm and vital signs is required. Signs that pacing may be failing include the set rate not being consistently followed by a QRS complex (failure to capture) or a decline in the patient’s blood pressure and perfusion status. The pacing site should also be inspected periodically for skin irritation or burns, especially if pacing is required for an extended period.