Cardiac pacing is a medical intervention regulating the heart’s rhythm. It involves implanting a device that sends electrical impulses, ensuring the heart beats at an appropriate rate when its natural system malfunctions.
The Heart’s Electrical System
The heart’s electrical system coordinates its pumping action. The sinoatrial (SA) node, a cluster of specialized cells in the upper right chamber, functions as the heart’s natural pacemaker. This SA node generates electrical impulses that spread across the upper chambers, causing them to contract and push blood into the lower chambers.
Signals then travel to the atrioventricular (AV) node, located between the upper and lower chambers. The AV node briefly delays the impulse, ensuring the upper chambers have fully emptied before the lower chambers begin to contract. From the AV node, signals proceed through specialized pathways, like the bundle of His and Purkinje fibers, distributing the impulse throughout the lower chambers for coordinated contraction. When this system malfunctions, the heart’s rhythm can become too slow or irregular, potentially requiring intervention.
Cardiac Conditions Requiring Pacing
Cardiac pacing becomes necessary when the heart’s natural electrical system fails to maintain an adequate rhythm, leading to symptoms or health risks. One common condition is Sick Sinus Syndrome, where the SA node malfunctions, causing heartbeats that are too slow, pauses in rhythm, or alternating rates. This can lead to symptoms such as extreme fatigue, dizziness, or fainting spells.
Another indication for pacing is heart block, particularly second-degree Mobitz type II and third-degree (complete) heart block. In these conditions, electrical signals are either delayed or completely blocked as they travel from the upper to the lower chambers, resulting in a very slow heartbeat. Such blocks prevent the coordinated pumping action needed to supply sufficient blood to the body, often causing lightheadedness, shortness of breath, or fainting. Pacing may also be considered for certain arrhythmias that cause symptomatic bradycardia, or in cases of atrial fibrillation accompanied by a slow heart rate. After a heart attack, if electrical system damage causes persistent slow heart rates, pacing may be needed.
Temporary vs. Permanent Pacing
Pacing devices address either short-term, acute issues or long-term, chronic heart rhythm problems. Temporary pacing is employed in situations where a slow heart rate is expected to resolve, such as during recovery from heart surgery, after a medication overdose, or following an acute heart attack that temporarily disrupts the electrical system. This temporary measure stabilizes the heart’s rhythm until the underlying cause resolves or a permanent solution is implemented. Temporary pacing can be achieved externally, using pads placed on the chest to deliver electrical pulses, or transvenously, by threading a wire through a vein into the heart and connecting it to an external generator.
Permanent pacing is for individuals with chronic, irreversible heart rhythm disorders. This involves surgically implanting a small, battery-powered device, often called a pacemaker, beneath the skin, typically near the collarbone. Leads are guided through a vein into the heart chambers, delivering electrical signals from the pacemaker to regulate the heart’s rhythm. Permanent pacing is decided when long-term support is required for conditions like persistent symptomatic bradycardia or advanced heart blocks.
The Pacing Procedure and Recovery
Implanting a permanent pacemaker typically involves minor surgical intervention. The process usually occurs under local anesthesia, with the patient awake but numbed, and some sedation for relaxation. A small incision (five to six centimeters) is made below the collarbone, usually on the left side.
Leads are guided through a vein into the heart chamber(s) using X-ray imaging for precise placement. The leads connect to the pulse generator (containing the battery and circuitry), placed in a pocket under the skin. After implantation, patients are monitored overnight and typically discharged the next day. Recovery involves keeping the incision site clean and dry, limiting arm movement, and attending follow-up appointments to ensure correct pacemaker function.