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H-H predicts V-V in BBRVT — if H-H shortens before V-V shortens, it confirms bundle branch reentry as the mechanism.

PJRT is a form of AVRT using a slowly conducting, decremental posteroseptal accessory pathway — mimics atrial tachycardia with a long RP interval.

Para-Hisian pacing: RB capture → short HA = nodal pathway; HB capture → long HA = accessory pathway.

Adenosine terminates AVNRT/AVRT but only transiently slows atrial tachycardia — use this to differentiate on the EP study.

VA linking during VT: if VA interval is fixed regardless of RB/LB aberrancy, it supports a septal AP or AVNRT with bystander AP.

Entrainment with concealed fusion + PPI–TCL < 30 ms + SA–VA ≈ VA = tachycardia circuit is at the pacing site.

Atypical AVNRT (fast-slow): long RP tachycardia, VA > AV, earliest atrial activation at His — not coronary sinus.

Fascicular VT (Belhassen): RBBB + left-axis, responds to verapamil, ablation target is the posterior fascicle Purkinje potential.

HV interval > 100 ms = high risk for infra-Hisian block; prophylactic pacing is indicated even without symptoms.

Atrial flutter: typical (CTI-dependent) has negative sawtooth in II/III/aVF and positive in V1; reverse typical is the opposite.

CPVT: bidirectional VT triggered by exercise/catecholamines; treat with beta-blockers + flecainide; ICD if refractory.

Brugada: Type 1 (coved) is diagnostic; fever, sodium channel blockers, and vagotonia can unmask the pattern.

LQTS: QTc > 500 ms = high risk. LQT1 events with exercise (swimming), LQT2 with auditory stimuli, LQT3 at rest/sleep.

Watchman implant: LAAO is non-inferior to warfarin for stroke prevention in AF; requires TEE follow-up at 45 days.

CRT response predictors: LBBB morphology + QRS ≥ 150 ms = strongest predictors of CRT benefit.

Sinus node dysfunction: SNRT > 1500 ms or corrected SNRT > 550 ms is abnormal on EP study.

Manifest pre-excitation with shortest pre-excited RR ≤ 250 ms during AF = high-risk AP; ablation recommended.

Junctional tachycardia post-cardiac surgery: accelerated junctional rhythm, AV dissociation, responds to cooling and amiodarone.

Outflow tract VT (RVOT): LBBB + inferior axis; responds to adenosine/verapamil; ablation at earliest activation or pace-map.

Pacemaker-mediated tachycardia (PMT): retrograde VA conduction triggers endless-loop tachycardia; extend PVARP to terminate.