The devices used to deliver an electric shock to the heart are called defibrillator paddles, or more formally, defibrillation electrodes. In modern emergency medicine, the traditional handheld paddles have largely been replaced by self-adhesive defibrillation pads (also called multifunction defibrillation electrodes), which stick directly to the chest. Both are part of a machine called a defibrillator.
Paddles, Pads, and Internal Paddles
There are three main forms these electrodes take, depending on the situation:
- Handheld paddles: The classic metal-faced paddles you see in movies, pressed firmly against the chest by a medical professional. These require conductive gel to be applied first and about 10 to 12 kilograms of pressure pushed down onto the chest to ensure good contact.
- Self-adhesive pads: Flat, sticky electrode pads that are peeled and pressed onto the skin. These are the standard in modern resuscitation guidelines and are what you’ll find inside an AED (automated external defibrillator), the public-access devices mounted in airports, gyms, and offices.
- Internal paddles: Small, spoon-shaped electrodes used during open-heart surgery. Surgeons place these directly on the exposed heart, typically delivering 10 to 20 joules of energy, far less than what’s needed through the chest wall.
Why Adhesive Pads Replaced Paddles
Resuscitation guidelines updated in 2010 formally recommended switching from handheld paddles to adhesive pads, and that shift has stuck. The reasons are practical. Adhesive pads eliminate the need to apply conductive gel, reposition the paddles between shocks, and maintain heavy downward pressure. Once you stick them on, they stay in place, freeing up the rescuer’s hands to continue chest compressions while the defibrillator charges.
Safety is the bigger factor. In a study comparing the two approaches, participants strongly preferred pads for safety. Handheld paddles expose the operator to risk because they’re physically gripping a device that delivers up to 5,000 volts. Adhesive pads reduce the chance of electric arc formation, skin burns, and accidental shock to bystanders. That said, paddles do have one advantage: in timed comparisons, first shocks were delivered slightly faster with paddles (about 21 seconds versus 30 seconds on a dry surface), likely because there’s no peel-and-stick step. On wet surfaces, that speed gap widened further.
Where the Pads Go on the Chest
The standard placement is called the anterior-lateral position. One pad goes just below the right collarbone, next to the breastbone. The second goes on the left side of the chest, centered below the armpit. This positions the heart directly between the two electrodes so the electrical current passes through the heart muscle effectively.
An alternative is the anterior-posterior position: one pad on the front of the chest over the heart, the other on the back below the left shoulder blade. Both placements work. AEDs typically include diagrams printed directly on the pads showing exactly where to place them.
What the Shock Actually Does
Defibrillation doesn’t “jump-start” a stopped heart, despite what TV dramas suggest. What it actually does is the opposite: it briefly stops all electrical activity in the heart at once. When the heart is in a dangerous rhythm like ventricular fibrillation, its muscle cells are firing chaotically and out of sync, so the heart quivers instead of pumping. The shock forces nearly all of those cells to reset at the same moment. If things go well, the heart’s natural pacemaker cells then fire on their own and restart a normal, organized rhythm, restoring a pulse.
This is why defibrillation only works on certain abnormal rhythms. A heart that has completely flatlined (true asystole) has no electrical activity to reset, which is why shocking a flatline, another common TV trope, isn’t how real resuscitation works.
The “All Clear” Safety Check
Before a shock is delivered, someone calls out a version of “I’m clear, you’re clear, everybody’s clear” while visually confirming no one is touching the patient. This ritual exists because the voltages involved (up to 5,000 volts) can injure or kill a bystander who becomes part of the electrical pathway. The severity depends on where the current travels through the body. Current passing through the heart can trigger fatal arrhythmias, while current through nerves can cause nerve damage. Even factors like sweaty hands or a torn glove change how much current a rescuer might absorb.
AEDs handle this automatically by issuing voice prompts telling everyone to stand back before delivering the shock. The machine analyzes the heart rhythm on its own and will only allow a shock if it detects a rhythm that defibrillation can correct.
Why Conductive Gel Matters for Paddles
If you’ve seen medical teams squeeze gel onto handheld paddles before use, that’s conductive gel, and it serves two purposes. First, it reduces the electrical resistance between the metal paddle and the skin, allowing more of the energy to reach the heart instead of being lost at the surface. Second, it prevents burns. Without gel, the high-voltage current can arc across dry skin, causing electrical burns or, in extreme cases, fire. Self-adhesive pads have a conductive gel layer built into the adhesive, which is one more reason they’ve become the default.