The earliest study on electroporation I’ve come across: 1979 . Researchers found small voltages (150 - 400 mV) applied to lipid bilayers -> irreversible mechanical breakdown. But, larger voltages applied for shorter durations-> reversible breakdown of membranes

Eugene Braunwald’s foreword in Douglas Zipes’ autobiography 😅

8/8.References:. - Cardiac Pacing, Defibrillation and Resynchronization: A Clinical Approach. Asirvatham, Friedman, Hayes.ISBN:9781119264002. - Clinical Cardiac Pacing, Defibrillation and Resynchronization Therapy. Ellenbogen & Bruce L. Wilkoff et al. ISBN: 9780323378048.

7/8.This is also why modern pacemakers use biphasic pulses. A second, opposite pulse helps discharge the capacitor - preventing charge buildup that could lead to electrolysis & electrode damage over time.

6/8.How do we minimize this?. Lead Materials: Using materials like platinum, iridium, and titanium. Lead Design: Creating leads with a small radius (maintaining impedance) but a porous, fractal surface which maximizes the electrochemical surface area (reducing polarization)

5/8.What about "afterpotentials"?. When the pacing pulse ends, the Double Layer capacitor discharges and releases this charge. The ventricular refractory period (VRP) of the pacemaker avoids sensing these afterpotentials

4/8.Coming back to pacemakers. When the pacemaker sends an electric current down the lead, this Helmholtz Double Layer capacitor forms and creates a polarization voltage which impedes the flow of electrons (contributing to impedance). The result? The capacitive droop

3/8.What is a capacitor? . Think of it as a mini-battery storing charge. When you separate 2 conducting plates by a layer of insulation (dielectric) and connect this to a battery -> you create a voltage over the capacitor.

2/8.Helmholtz described that when a charged electrode was placed in a solution (like blood), it attracted a layer of oppositely charged ions. Creating an electrical "Double Layer" which acts like a tiny capacitor.

🧵1/8.What causes the "droop" in a pacemaker pulse? Why do afterpotentials occur? & why do pacemaker leads have fractal surfaces?. It all comes back to a simple concept described by Hermann V. Helmholtz in 1879: The Helmholtz Double Layer. #CardioTwitter #EPeeps #PacemakerPhysics

RT @DrDeese99: MYL4 Identifies Intramural Anatomy of Purkinje Fibers in Human Hearts | JACC: Clinical Electrophysiology .

RT @ugurkucuk: Very important study. This is a paradigm shift. #openaccess . MYL4 Identifies Intramural Anatomy of Purkinje Fibers in Human….

RT @ugurkucuk: Septal Intramyocardial Purkinje Network: A Potential New Mechanism Explaining Left Bundle Branch Area Pacing Physiology | JA….

Link to paper: .

3 gross classifications:.1️⃣ Thin & discrete: 2-3 cell layers, 0.4–0.6mm LBB thickness.2️⃣ Thin & complex: 3-9 cell layers, increased connective tissue.3️⃣ Thick & complex: thicker LBB (11-25 cell layers) with significant connective tissue.

🫀Why is there such variability in 👀 LBB potentials during CSP?. 1 possibility @jacabreracardio et al. describe is LBB anatomical heterogeneity where differences in muscle thickness & insulating connective tissue potentially influence signal detection ⬇️. #Epeeps @JACCJournals.

The great @ugurkucuk giving a brilliant overview of ICE - highlighting its historical development & contribution by @AJamilTajik. #CVimagingGrandRounds @MDMankad @MayoClinicCV @MayoEPFellows

3 generations of @MayoMN_IMRES residents re-uniting @HRSonline #HRS2025 🫀⚡️. @iShadrinMDPhD @MCastrichiniMD #OmarLatif @CaThompsonMD . @MayoClinicCV @DukeCardFellows @OhioState

RT @mandeep_mayo: Cardiac conduction system involvement in STEMI.Now we know why AV blocks in inferior STEMI are more common than SA blocks….

RT @MayoClinicCV: Free case-based webinar on CIED lead extraction on March 12 at 6 p.m. CST. Join @MayoClinic faculty Yong-Mei Cha, M.D. &….