RCES key terms

The longest coupling interval of a premature stimulus that still fails to produce a propagated response. It shows how long tissue stays unexcitable after depolarization and sets the fastest rate that tissue can follow.

The speed at which an electrical impulse spreads through cardiac tissue, usually reported in meters per second. It depends on the action potential upstroke, cell-to-cell coupling, fiber orientation, and tissue health.

A small structure where atrial and ventricular muscle meet electrically. Its slow, decremental conduction delays each impulse before it reaches the His bundle, limiting how fast the ventricles can be driven.

A property of AV nodal tissue in which faster pacing rates produce progressively slower conduction and longer conduction times. It helps separate AV nodal conduction from conduction over an accessory pathway.

A triangular region in the right atrium bordered by the tricuspid annulus, the tendon of Todaro, and the coronary sinus ostium. It contains the AV node and guides slow pathway ablation.

The strip of tissue between the tricuspid valve annulus and the inferior vena cava. It forms the critical narrow passage of typical atrial flutter and is the usual target for flutter ablation.

The opening where a pulmonary vein joins the left atrium. Most triggers of atrial fibrillation arise in the muscle sleeves near these openings, so they are the main targets for isolation.

The ability of a differential amplifier to cancel signals that appear identically on both inputs, such as power-line interference, while still amplifying the small difference between the two electrodes.

A filter that removes a narrow band of frequencies, usually 50 or 60 Hz, from a recorded signal. It reduces power-line interference without broadly changing the rest of the electrogram.

The distance between the two electrodes of a bipolar catheter, commonly 1, 2, or 5 mm. Closer spacing sharpens localization of local activation but produces smaller signals.

A technique that combines catheter position with electrical recordings to build a three-dimensional model of a chamber. Activation timing or voltage is displayed as colour on that geometry.

A recording between two closely spaced catheter electrodes that emphasizes sharp local activity and rejects distant signals. Its timing and shape are used for mapping and for identifying scar.

The moment assigned to the steepest negative deflection of a bipolar electrogram at a mapped site. Mapping systems compare these times to build an activation map of a rhythm.

A low-amplitude signal with several deflections that lasts longer than a normal electrogram. It is typically recorded in scarred tissue and can mark slow conduction channels that sustain reentry.

A recording from the His region that shows atrial, His, and ventricular deflections. It allows measurement of conduction through the AV node and the His-Purkinje system.

The time from the earliest His deflection to the onset of ventricular activation. Normal is roughly 35 to 55 ms, and a longer value suggests conduction disease below the AV node.

Delivery of timed pacing pulses, usually a drive train followed by one or more premature extrastimuli, to test refractoriness and provoke arrhythmias. It is the basic tool for studying reentry.

Pacing slightly faster than a reentrant tachycardia so that pacing impulses enter and reset the circuit. Responses after pacing stops show whether the pacing site lies inside or outside the circuit.

The interval from the last pacing stimulus during entrainment to the first local electrogram recorded after pacing stops. A value close to the tachycardia cycle length suggests the site is within the circuit.

Delivery of alternating current through a catheter tip to heat tissue and create a small thermal lesion. Lesion size depends on power, temperature, electrode contact, and cooling by blood flow.

The measured force between an ablation electrode and the heart wall. Enough force improves lesion quality, while excessive force raises the risk of steam pops and perforation.

A calculated value that combines power, contact force, and time to estimate lesion size and depth. Operators aim for set target values to create consistent, transmural lesions.

An explosive release of gas when tissue beneath the ablation electrode overheats and boils. It can tear the myocardium and lead to perforation or cardiac tamponade.

A nonthermal method that delivers very short high-voltage pulses to open pores in cell membranes. It mainly destroys heart muscle cells and may spare nearby structures such as the esophagus and phrenic nerve.

Ablation intended to electrically disconnect the pulmonary vein muscle sleeves from the left atrium, usually with contiguous circular lesions around each vein. It is the cornerstone treatment for atrial fibrillation.

The smallest pacing output, at a given pulse width, that consistently depolarizes the heart. It is measured at implant and at follow-up to confirm that the lead still works well.

The opposition to current flow between pacing lead electrodes, measured in ohms. A sudden rise or fall may signal conductor fracture, insulation failure, or tissue changes at the tip.

When a device counts signals that are not true cardiac depolarizations, such as T waves, muscle noise, or lead artifact, as sensed events. It can cause inappropriate pacing inhibition or unnecessary shocks.

Programmed rate ranges that tell an ICD when a rhythm should be treated as ventricular tachycardia or ventricular fibrillation. Rate, duration, and morphology criteria decide whether therapy is delivered.

Pacing both ventricles, usually through a right ventricular lead plus a lead placed in a coronary sinus branch. It resynchronizes contraction in heart failure patients with a wide QRS complex.

A very short-acting drug that briefly blocks conduction through the AV node. It terminates AV nodal reentrant tachycardia and can reveal flutter or accessory pathway conduction by slowing the ventricular rate.

A beta-adrenergic agonist that raises heart rate and speeds conduction. It is infused during EP studies to help induce tachycardias and to test whether a rhythm depends on sympathetic tone.

A bedside blood test of clotting speed used to monitor unfractionated heparin during procedures. Values are kept high enough to prevent catheter thrombus but low enough to limit bleeding.

A drug that binds and neutralizes heparin. It is used to reverse anticoagulation after procedures when bleeding risk is high, with monitoring for hypotension and allergic reactions.

A drug-induced state in which the patient responds purposefully to voice or light touch while breathing without assistance. It is widely used for EP procedures and requires continuous cardiorespiratory monitoring.

The radiation safety principle of keeping dose as low as reasonably achievable. It is applied by reducing fluoroscopy time, collimating the beam, and using the lowest adequate frame rate.

A brief pause before the procedure begins when the team verbally confirms patient identity, procedure, site, allergies, and equipment. It is a required step to prevent wrong-patient and wrong-site errors.

A probe placed in the esophagus to measure temperature during left atrial ablation. A temperature rise warns of thermal injury risk to the esophagus and prompts the operator to stop or move energy delivery.

Damage to the nerve that controls the diaphragm, usually from ablation or cryotherapy near the right superior pulmonary vein or superior vena cava. It causes diaphragm paralysis and shortness of breath.