IBHRE CEPS flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

HV interval

Conduction time from the His bundle electrogram to the earliest ventricular activation, normally 35-55 ms. Prolongation indicates infranodal disease with risk of progression to complete heart block.

AH interval

Conduction time from the low right atrial electrogram to the His bundle electrogram, normally 50-120 ms. It reflects AV nodal conduction and lengthens with rapid pacing or premature atrial extrastimuli.

Wenckebach periodicity

Progressive PR prolongation before a dropped QRS beat, caused by decremental conduction in the AV node. The greatest PR increment occurs in the first conducted beat after the pause.

Phase 4 depolarization

Spontaneous depolarization of pacemaker cells during diastole, driven mainly by the funny current I_f and T-type calcium current. Slope determines automaticity and sinus node firing rate.

Effective refractory period

The longest coupling interval of a premature extrastimulus that fails to produce a propagated response. It is measured during programmed stimulation and varies with cycle length and drug effect.

Ashman phenomenon

A wide QRS complex with right bundle branch block morphology occurring after a long-short cycle sequence. It reflects aberrant conduction from refractoriness, not a ventricular beat.

Orthodromic AVRT

A reentrant tachycardia using the AV node antegrade and an accessory pathway retrograde. It produces a narrow QRS unless rate-related bundle branch block occurs.

Bazett correction

Method to rate-correct the QT interval: QTc = QT divided by the square root of the RR interval in seconds. It overcorrects at fast rates and undercorrects at slow rates.

Cavotricuspid isthmus block

Confirmation of successful flutter ablation using pacing from the coronary sinus and lateral right atrium. A trans-isthmus delay above 130 ms with a descending activation pattern indicates bidirectional block.

Force-time integral

Cumulative contact force multiplied by ablation time, expressed in gram-seconds. Values near 400 g·s per lesion correlate with durable radiofrequency pulmonary vein isolation.

Steam pop

Abrupt tissue rupture caused by intramural boiling during radiofrequency delivery. Warning signs include an abrupt impedance rise and audible thump; risk rises with high power and excessive contact force.

Phrenic nerve pacing

Technique of pacing the right phrenic nerve during ablation near the right pulmonary veins or superior vena cava. Loss of diaphragmatic capture signals impending nerve injury and prompts immediate cessation.

Cryomapping

Delivery of cryoenergy to approximately -30 degrees Celsius to test lesion effect before creating a permanent lesion. If the desired effect appears, freezing continues to -70 to -80 degrees.

Pulmonary vein isolation

Creation of circumferential lesions around pulmonary vein ostia to block electrical connection with the left atrium. Entry and exit block confirm isolation and is the main endpoint in atrial fibrillation ablation.

Entrainment mapping

Pacing at a rate faster than a reentrant tachycardia to identify a critical isthmus. A post-pacing interval equal to the tachycardia cycle length indicates a site within the circuit.

Atrial-esophageal fistula

A rare, often fatal complication of posterior left atrial ablation presenting days to weeks later with fever, dysphagia, and neurologic events. Urgent imaging and surgical consultation are required.

Substrate modification

Ablation strategy for ventricular tachycardia that targets scar and abnormal electrograms rather than the clinical circuit. It is used when the tachycardia is not hemodynamically tolerated for mapping.

NBG pacemaker code

Five-position code describing paced chamber, sensed chamber, response to sensing, rate modulation, and multisite pacing. For example, DDDD means dual-chamber pacing and sensing with dual response.

Mode switch

Automatic conversion from a tracking mode such as DDD to a nontracking mode such as DDI during atrial tachyarrhythmia. It prevents rapid ventricular pacing in response to fast atrial rates.

PVARP

Post-ventricular atrial refractory period, during which sensed atrial events are ignored after a ventricular event. Together with the AV delay it sets the upper rate limit in DDD pacing.

Defibrillation threshold

The lowest shock energy that reliably terminates ventricular fibrillation. A safety margin of about 10 J below the device maximum output is commonly considered acceptable.

SVT discriminators

Device algorithms that distinguish supraventricular from ventricular tachyarrhythmia, including sudden onset, rate stability, and morphology comparison. They reduce inappropriate ICD shocks for atrial arrhythmias.

Lead impedance trend

Serial measurement of lead impedance used to detect hardware failure. An abrupt rise suggests fracture or dislodgement, while a gradual fall suggests insulation breach or fluid ingress.

Magnet response

Application of a magnet switches pacemakers to asynchronous pacing at the magnet rate and suspends ICD tachyarrhythmia detection. It is used to test battery status and stop inappropriate shocks.

Biventricular pacing

Simultaneous pacing of the right and left ventricles via a coronary sinus lead to resynchronize contraction. It improves symptoms and outcomes in selected heart failure with left bundle branch block.

Dofetilide initiation

Requires hospital monitoring with QTc checks after each dose. It is contraindicated when baseline QTc exceeds 440 ms, or 500 ms when the QRS is widened.

Amiodarone monitoring

Baseline and periodic thyroid, hepatic, pulmonary, and ophthalmologic assessment. Annual testing is typical, with chest imaging prompted by new pulmonary symptoms or dyspnea.

Flecainide restriction

Class IC sodium channel blocker contraindicated in structural heart disease because of proarrhythmia risk. It is used for atrial fibrillation in patients without coronary disease or ventricular dysfunction.

CHA2DS2-VASc score

Stroke risk score for atrial fibrillation incorporating heart failure, hypertension, age, diabetes, stroke, vascular disease, and sex. Scores of 2 or more in men warrant anticoagulation.

Adenosine half-life

Under 10 seconds, producing transient AV nodal block after bolus administration. It terminates AV nodal reentrant tachycardia and can reveal flutter waves in a wide-complex tachycardia.

Sotalol precautions

Class III agent that prolongs QT and is cleared renally, requiring dose adjustment and monitoring during initiation. It is stopped if the corrected QT interval exceeds 500 ms.

Ivabradine mechanism

Inhibits the funny current I_f in the sinus node to lower heart rate without affecting contractility. It is used in heart failure with reduced ejection fraction and sinus rhythm above 70 bpm.