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  • Title: Cardiac contractility modulation in non-responders to cardiac resynchronization therapy.
    Author: Nägele H, Behrens S, Eisermann C.
    Journal: Europace; 2008 Dec; 10(12):1375-80. PubMed ID: 18776196.
    Abstract:
    AIMS: Cardiac resynchronization therapy (CRT) has become a standard therapy in cases of heart failure and asynchrony. Unfortunately, 20-30% of patients were non-responsive (NR) to CRT. In this report we used cardiac contractility modulation (CCM) as an adjunctive measure in NR patients. METHODS AND RESULTS: Sixteen NR patients, mean age 65 +/- 9 years, mean ejection fraction 27.3 +/- 7.4%, and New York Heart Association (NYHA) class III (n = 9) or IV (n = 7) despite CRT plus optimized medical therapy, received an additional CCM-implantation contra-lateral to the existing CRT system (OPTIMIZER III, Impulse Dynamics, Orangeburg, NY, USA). Cardiac contractility modulation delivers non-excitatory high-energy stimulatory impulses during the absolute refractory period, thus improving contractility [left ventricular (LV) dp/dt)] by stimulating the septum with two screw-in leads and one additional atrial lead for triggering the impulses. Acute LV dp/dt changes induced by CCM stimulation were measured by 5F Millar catheters placed in the LV during the implantation procedure in 14 of 16 cases. Patients were followed prospectively. Left ventricular dp/dt increased from a mean of 568 +/- 153 to 646 +/- 147 mmHg/s (+14%, P < 0.001) in the acute intraoperative testing. We noted the following complications and events during a follow-up of an average of 147 +/- 80 days (range 68-326) after CCM: intraoperative ventricular flutter needing cardioversion (n = 1), atrial lead dislocation (n = 1), coronary sinus (CS) lead dislocation (n = 1), painful stimulation requiring repositioning of septal leads (n = 1), true defibrillator shocks (n = 3), cardiac decompensations (n = 3), atrial fibrillation (n = 4), renal failure (n = 1), and pneumonia (n = 2). NYHA class improved from 3.4 to 2.8 (P < 0.01), and the ejection fraction increased from 27.3 +/- 5 to 31.1 +/- 6 (P < 0.01). Three patients (19%) died suddenly presumably due to electromechanical dissociation after 318, 104, and 81 days. No electrical interference was observed between the CCM and CRT systems, and in particular, at no time was the CRT-implantable cardioverter-defibrillator found to be delivering inadequate shocks. CONCLUSION: The CCM method is feasible and could be applied with calculated risks as a possible useful adjunct in CRT-NR when no other options are available; however, mortality and event rates are high in this very sick population.
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