RCES cheat sheet

Normal conduction sequence: SA node → atria → AV node (delay ~0.1 s) → His bundle → bundle branches → Purkinje fibers; ventricular activation proceeds endocardium to epicardium.

Ventricular myocyte resting potential is about -85 to -90 mV; threshold is about -70 to -65 mV; phase 0 is fast Na+ current, phase 2 is L-type Ca2+ current, and phase 3 is K+ repolarization.

AV nodal and His-Purkinje upstrokes are slow-response and Ca2+-dependent; AV nodal conduction is slow and decremental, unlike fast-response atrial and ventricular myocardium.

Effective refractory period is the longest premature coupling interval that fails to conduct; atrial ERP is shorter than AV nodal ERP, and ventricular ERP is roughly 200-250 ms.

Conduction velocity is highest in Purkinje fibers (~2-4 m/s), intermediate in ventricular myocardium (~0.3-1 m/s), and lowest in the AV node (~0.02-0.05 m/s).

Sympathetic beta-1 stimulation increases heart rate, AV conduction, and contractility; vagal muscarinic stimulation slows SA node firing and AV conduction, with vagal effects predominating at both nodes.

Coronary sinus drains most of the left ventricle, runs in the left AV groove, and enters the right atrium near the tricuspid annulus; its ostium is a landmark for left ventricular mapping.

Right atrial landmarks include the crista terminalis, SVC/IVC junctions, fossa ovalis, coronary sinus ostium, and tricuspid annulus; left atrial landmarks include pulmonary vein ostia, appendage, and mitral annulus.

Intracardiac bipolar electrograms are typically bandpass filtered at 30-500 Hz; surface ECG is usually filtered at 0.05-150 Hz; narrower filters reduce noise but can distort local activation timing.

Smaller catheter electrode spacing (1-2 mm) improves local signal resolution but lowers electrogram amplitude; wider spacing (2-5 mm) records larger but more far-field signals.

Ablation impedance is typically about 80-150 ohms; an abrupt rise suggests coagulum or tissue desiccation, and an abrupt fall suggests steam pop, catheter dislodgment, or circuit change.

RF lesion size depends on power, duration, electrode-tip size, contact force, irrigation, and tissue contact; a standard 4-mm-tip lesion is roughly 3-6 mm deep.

Standard RF ablation targets tissue-electrode temperatures around 50-65°C; irrigated catheters often display lower tip temperatures (~40-45°C) while producing deeper lesions.

Pacing capture thresholds are commonly tested at 0.5-2 ms pulse width and 1-10 mA output; the threshold is the minimum current or voltage producing consistent capture.

A 50/60 Hz notch filter removes powerline interference; high-pass filtering reduces baseline wander, and low-pass filtering reduces high-frequency muscle and electrical noise.

Unipolar recordings show larger, broader signals with more far-field content; bipolar recordings show sharper, more local activation and are preferred for timing and mapping.

Baseline intracardiac intervals: PA 20-50 ms, AH 50-120 ms, and HV 35-55 ms; AH reflects AV nodal conduction and HV reflects His-Purkinje conduction.

Sinus node recovery time is normally less than 1500 ms; corrected SNRT equals SNRT minus baseline sinus cycle length and is normally less than 550 ms.

AV Wenckebach cycle length is typically greater than 500 ms at baseline; a shorter Wenckebach cycle length suggests impaired AV nodal conduction.

Tissue ERP is the longest premature coupling interval that fails to conduct; programmed extrastimuli (S1S2, S1S2S3) and burst pacing are used to measure refractoriness and induce tachycardia.

Concentric retrograde atrial activation (His → CS ostium → proximal → distal CS) suggests AV nodal conduction; eccentric activation suggests an accessory pathway or atypical circuit.

Entrainment uses overdrive pacing within a tachycardia; a postpacing interval minus tachycardia cycle length under about 20-30 ms suggests the pacing site is near or within the reentry circuit.

A His-bundle recording shows a sharp His deflection between atrial and ventricular signals; the HV interval is measured from the earliest His deflection to the earliest ventricular activation.

Para-Hisian pacing helps differentiate retrograde AV nodal conduction from an accessory pathway by comparing atrial activation timing with and without His capture.

Radiofrequency ablation creates resistive heating at the tissue-electrode interface; contact force (commonly 10-20 g), power, duration, irrigation, and stability determine lesion quality.

Irrigated RF reduces electrode-tip temperature and allows higher power delivery, producing deeper lesions; open irrigation flows are commonly 8-30 mL/min depending on catheter and power.

Cryoablation uses reversible cryomapping near -30°C to test safety; therapeutic freezing typically targets -50 to -70°C, causing cellular injury through ice formation and thawing.

Pulmonary vein isolation requires entry block, exit block, and elimination of PV potentials; circumferential antral lesions are preferred to reduce PV stenosis risk.

Cavotricuspid isthmus ablation for typical atrial flutter creates a line between the tricuspid annulus and IVC; the acute endpoint is bidirectional CTI conduction block.

AVNRT slow pathway modification targets the inferior triangle of Koch near the coronary sinus ostium; success is lack of inducible AVNRT, with heart block risk around 1%.

Accessory pathway ablation is guided by earliest ventricular activation during preexcitation or earliest retrograde atrial activation during orthodromic AVRT; proximity to coronary arteries matters.

Major ablation risks include cardiac tamponade, PV stenosis, phrenic nerve palsy, atrioesophageal fistula, stroke, vascular injury, and radiation exposure; anticoagulation and monitoring reduce thromboembolic risk.

The NBG code describes paced chamber, sensed chamber, response to sensing, rate modulation, and multisite pacing; examples include VVI, DDD, DDDR, and CRT-D.

DDD pacing tracks sensed P waves and paces the ventricle; during atrial tachyarrhythmia, mode switch to DDIR or VVIR prevents rapid ventricular tracking.

ICD detection uses programmed rate and duration criteria; ventricular fibrillation typically receives shocks, while organized VT may first receive antitachycardia pacing (ATP).

CRT is indicated for selected heart failure patients with reduced ejection fraction and wide QRS, especially LBBB with QRS duration of 150 ms or greater.

Acceptable acute pacing parameters are generally capture threshold below 1 V at 0.4 ms, R-wave amplitude above 5 mV, and impedance roughly 300-1000 ohms.

A magnet over a pacemaker often causes asynchronous pacing if programmed; a magnet over an ICD usually suspends tachyarrhythmia detection and therapy while preserving bradycardia pacing.

MRI-conditional CIEDs require specific device, lead, programming, and monitoring conditions; nonconditional devices may pose risks from lead heating and programming changes.

Electromagnetic interference from electrosurgery can inhibit pacing or trigger ICD shocks; bipolar cautery, ICD tachytherapy suspension, and continuous ECG monitoring reduce risk.

Moderate sedation preserves airway reflexes and response to verbal commands; deep sedation may impair airway protection and require advanced airway support.

Midazolam is a benzodiazepine with onset in 1-2 minutes and duration of 20-60 minutes; flumazenil reverses its sedative effect but can precipitate seizures in chronic benzodiazepine users.

Fentanyl is a rapid-onset opioid with peak effect in 5-15 minutes; naloxone reverses respiratory depression, and rapid high-dose fentanyl can cause chest wall rigidity.

Propofol produces rapid sedation and hypnosis with onset in 30-60 seconds and brief duration; it can cause hypotension and apnea, and it has no specific reversal agent.

Dexmedetomidine is an alpha-2 agonist that provides sedation with less respiratory depression; bradycardia and hypotension are common adverse effects.

Isoproterenol is a beta agonist used to increase heart rate and induce or facilitate tachycardia; it can provoke ischemia, arrhythmia, and hypotension.

Adenosine causes transient AV block with a half-life under 10 seconds; it can cause flushing, chest tightness, and bronchospasm and should be used cautiously in asthma.

Atropine is a muscarinic antagonist used for vagal bradycardia at 0.5-1 mg IV, maximum 3 mg; caution is needed in glaucoma and urinary retention.

Informed consent requires discussion of diagnosis, procedure, material risks, benefits, alternatives, and the patient's questions; consent must be voluntary and documented.

A preprocedure time-out verifies patient identity, procedure, site, consent, allergies, implants, anticoagulation status, and equipment availability with the entire team.

Radiation safety follows ALARA: minimize fluoroscopy time, use pulsed fluoroscopy and collimation, maximize distance, and wear 0.5-mm lead-equivalent aprons with thyroid shielding.

For left atrial ablation, unfractionated heparin is titrated to an activated clotting time of about 300-350 seconds to reduce catheter-related thromboembolism.

Femoral venous access is preferred for most EP procedures; ultrasound guidance and manual pressure after sheath removal reduce vascular complications.

Sterile technique includes hand hygiene, cap, mask, sterile gown and gloves, and sterile drapes; antibiotic prophylaxis is given according to institutional protocol.

SBAR handoff communicates Situation, Background, Assessment, and Recommendation; structured handoff improves transfer of periprocedural information and reduces omissions.

Postprocedure monitoring includes vital signs, access-site assessment, distal pulses, ECG rhythm, and surveillance for bleeding, hematoma, or retroperitoneal hemorrhage.