Impact of Cardiac Contractility Modulation on Left Ventricular Global and Regional Function and Remodeling

Cardiac contractility modulation for heart failure: a meta-analysis of randomized controlled trials

BACKGROUND

Cardiac contractility modulation (CCM) emerges as a promising device treatment for heart failure (HF). This meta-analysis aimed to systematically review the latest available randomized evidence on the effectiveness and safety of CCM in HF.

METHODS

The Cochrane Central Register of Controlled Trials, MEDLINE, and EMBASE were searched in November 2011 to identify eligible randomized controlled trials comparing CCM with sham treatment or usual care. Primary outcomes of interest were all-cause mortality, all-cause hospitalizations, and adverse effects. Risk ratios (RRs) and 95% confidence intervals (CIs) were calculated for dichotomous data using a random-effects model.

RESULTS

Three studies enrolling 641 participants were included. Pooled analysis showed that, compared to control, CCM did not significantly improve all-cause mortality (n = 629, RR 1.19, 95% CI 0.50-2.86, P = 0.69), nor was there a favorable effect in all-cause hospitalizations. No increase in adverse effects with CCM was observed.

CONCLUSIONS

Meta-analysis of data from small randomized trials suggests that CCM, although with no clear benefits in improving clinical outcomes, is not associated with worsening prognosis. Large, well-designed trials are needed to confirm its role in HF patients for whom cardiac resynchronization therapy is contraindicated or unsuccessful.

Clinical effects of cardiac contractility modulation (CCM) as a treatment for chronic heart failure

Cardiac contractility modulation (CCM) signals are non-excitatory signals applied during the absolute refractory period that have been shown to enhance the strength of left ventricular contraction without increasing myocardial oxygen consumption in studies carried out in animals and humans with heart failure and reduced ejection fraction. Studies from myocardial tissue of animals and humans with heart failure suggest that the mechanisms of these effects is that CCM drives expression of many genes that are abnormally expressed in heart failure towards normal, including proteins involved with calcium cycling and the myocardial contractile machinery. Clinical studies have primarily focused on patients with normal QRS durations in view of the fact that cardiac resynchronization (CRT) is a viable option for patients with prolonged QRS duration. These studies show that CCM improves exercise tolerance as indexed by peak oxygen consumption (VO(2)) and quality of life indexed by the Minnesota Living with Heart Failure Questionnaire. The device is currently available for clinical use in countries recognizing the CE mark and is undergoing additional testing in the USA under a protocol approved by the Federal Drug Administration.

[Treating congestive heart failure with cardiac contractility modulation (CCM) : possibilities and study overview]

Cardiac contractility modulation (CCM) is a device therapy for patients with systolic heart failure. CCM therapy applies non-excitatory signals during the absolute refractory period of the heart cycle. It influences myocardial contractility by modulating the regulation of calcium cycling. CCM therapy has been proven to enhance peak VO(2), quality of life and exercise tolerance in patients with congestive heart failure. It can be used as an additional therapy to an implantable cardioverter defibrillator (ICD), if present. CCM therapy should be considered in symptomatic patients with congestive heart failure, a left ventricular ejection fraction ≤35% and NYHA class II-III. Atrial fibrillation, high grade arrhythmias and an AV block of more than 300 ms represent contraindications. Patients with a left bundle branch block of >120 ms should be considered for the implantation of a biventricular ICD prior to implantation of a CCM device.

Electrical modalities beyond pacing for the treatment of heart failure

In this review, we report on electrical modalities, which do not fit the definition of pacemaker, but increase cardiac performance either by direct application to the heart (e.g., post-extrasystolic potentiation or non-excitatory stimulation) or indirectly through activation of the nervous system (e.g., vagal or sympathetic activation). The physiological background of the possible mechanisms of these electrical modalities and their potential application to treat heart failure are discussed.

Long-term outcome of cardiac contractility modulation in patients with severe congestive heart failure

AIMS

Cardiac contractility modulation (CCM) is a new form of electrical therapy in patients with congestive heart failure. Recently published clinical studies provide evidence of safety and improvements of exercise tolerance and quality of life. In this study, we investigated the impact of CCM on cardiac and all-cause mortality.

METHODS AND RESULTS

Fifty-four consecutive patients (age 63 ± 10 years, 91% male, left ventricular ejection fraction 23 ± 6%, baseline peak oxygen consumption 10.0 ± 4.8 mL/min/kg, N-terminal pro-B-type natriuretic peptide 5194 pg/mL, New York Heart Association III/IV) who underwent implantation of an Optimizer system (IMPULSE Dynamics, Orangeburg, NY, USA) at our centre between June 2003 and June 2010 were analysed retrospectively. Patients were followed every 3 months at our outpatient clinic. This study determined long-term outcomes of patients receiving CCM therapy. Twenty-four (44%) patients died during the follow-up period, which included 19 cardiac deaths (3 sudden cardiac deaths and 16 terminal cardiac pump failure deaths). The Kaplan-Meier analysis calculated a median survival time of 992 days (33.1 months) and a mean death rate of 18.4% per year. All-cause mortality for these patients was precisely predicted by the Seattle Heart Failure Model.

CONCLUSION

Cardiac contractility modulation appears to be a safe therapeutic option for advanced heart failure patients who have no other therapeutic options. Symptomatic improvement by CCM has been shown in earlier studies but our observational study suggests, for the first time, that there is no adverse effect of CCM on long-term survival.

The acute inotropic effects of cardiac contractility modulation (CCM) are associated with action potential duration shortening and mediated by β1-adrenoceptor signalling

Despite promising results in clinical trials conducted to date, little is known about how cardiac contractile modulation (CCM) mediated inotropic enhancement occurs and how CCM affects the electrophysiological characteristics of the heart. The aims of the present study were to 1) investigate how the stimulation parameters of the CCM signal and the location of stimulus delivery influence the contractile response, 2) characterise the effect of CCM on ventricular electrophysiology, and 3) investigate the potential physiological mechanisms underlying these acute inotropic and electrophysiological effects. Experiments were conducted in isolated rabbit hearts with simultaneous measurement of ventricular contractility and monophasic action potential duration (MAPD). Biphasic square wave pulses were applied to the left ventricle, timed to coincide with the absolute refractory period. CCM mediated responses were assessed over a range of signal amplitudes (2–30 mA), durations (2–15 ms) and delays from the activation of the locally recorded monophasic action potential (0–30 ms). Responses were assessed during perfusion with the β1-adrenoceptor antagonist metoprolol (1.8 μM) and HMR 1556 (500 nM), an inhibitor of the slow delayed rectifying potassium current. Norepinephrine content was collected and assessed by ELISA from samples of coronary effluent collected during CCM. CCM induced a significant increase in left ventricular pressure (LVP) in a manner dependent upon the amplitude and duration of the CCM signal but independent of the delay of the stimulus within the action potential plateau and was associated with an increase in norepinephrine in coronary effluent (Mean: 46 ± 9 pg/ml). CCM promoted a shortening of MAPD-90% close to the site of stimulation (− 19 ± 3%) but had no effect on those recorded at distant sites (0 ± 1%). The increase in LVP (4.7 ± 1.8 vs. 0.7 ± 0.9%, P < 0.01) and shortening of local MAPD-90% (− 15 ± 3 vs. 1 ± 1%, P < 0.01) was abolished with metoprolol. Perfusion with HMR 1556 caused a significant inhibition of local MAPD shortening (− 27 ± 2 vs. − 21 ± 3 ms, P < 0.05). CCM is associated with a shortening of ventricular MAPD in a manner dependent upon β-adrenoceptor stimulation resulting from catecholamine release, a finding which may be of clinical significance in regard to the development of malignant ventricular arrhythmias. This article is part of a Special Issue entitled Possible Editorial.