CARDIOLOGY
INTRACARDIAC DEVICES
Cardiac resynch therapy (CRT)/Biventricular (BiV) pacing (Circ 2012;126:1784)
• 3-lead pacemaker (RA, RV, coronary sinus to LV); R>S in V1 suggests approp LV capture
• Synchronize & enhance LV fxn (↑ CO, ↓ adverse remodeling)
• Indic: LVEF ≤35% + NYHA II–IV despite med Rx + SR + LBBB ≥150 ms (also reasonable if either LBBB ≥120 ms or no LBBB but QRS ≥150 ms + NYHA III–IV); consider in AF, but rate cntl → ~100% vent capture; ? NYHA I w/ LVEF ≤30% + LBBB ≥150 ms; ? EF ≤50% w/ AVB + indic for PPM (NEJM 2013;368:1585)
• Benefits: ↓ HF sx, ↓ HF hosp., ↑ survival (NEJM 2005;352:1539; 2010;363:2385)
Implantable cardiac defibrillator (ICD) (NEJM 2003;349:1836; JACC 2009;54:747)
• RV lead: defib & pacing (± antitachycardia pacing [ATP] = burst pacing > VT rate to stop VT); ± RA lead for dual chamber PPM. Wearable vest & SC ICD exist (Circ 2013;127:854).
• Pt selection (NEJM 2004;350:2151 & 351:2481; 2005;352:225; 2009;361:1427; Circ 2012;126:1784)
2° prevention: survivors of VF arrest, unstable VT w/o reversible cause (NEJM 1997;337:1576); structural heart disease & spontaneous sustained VT (even if asx)
1° prevention: LVEF ≤30% & post-MI or LVEF ≤35% & NYHA II-III (wait: ≥40 d if post-MI, ? until stabilized on meds for NICMP, or if presumed reversible) or LVEF ≤40% & inducible VT/VF; life expectancy must be >1 y; consider for HCM, ARVC, Brugada, sarcoid, LQTS, Chagas or congenital heart disease if risk factors for SCD
• Benefits: ↓ mortality from SCD c/w antiarrhythmics or placebo
• Risks: inapprop shock in ~15–20% at 3 y (most commonly d/t misclassified SVT); infxn
• ICD discharge: ✓ device to see if approp; r/o ischemia; 6-mo driving ban (✓ state law); if recurrent VT, ? drug Rx (eg, amio + bB, JAMA 2006;295:165) or VT ablation (NEJM 2007;357:2657); ablation at time of ICD ↓ risk of VT by 40% (Lancet 2010;375:31)
Device infection (Circ 2010;121:458; JAMA 2012;307:1727; NEJM 2012;367:842)
• Presents as pocket infection (warmth, erythema, tenderness) and/or sepsis w/ bacteremia
• Incidence ~2% over 5 y; if S. aureus bacteremia, infxn in ≥35%
• TTE/TEE used to help visualize complic. (eg, vegetation), but even 
TEE does not r/o
• Treatment: abx and removal of system; Ppx: no rec for routine abx prior to invasive proc.