Cardiac contractility modulation for patient with refractory heart failure: an updated evidence-based review

Heart failure is the cardiovascular epidemic of the twenty-first century, with poor prognosis and quality of life despite optimized medical treatment. Despite over the last decade significant improvements, with a major impact on morbidity and mortality, have been made in therapy for heart failure with reduced ejection fraction, little progress was made in the development of devices, with the implantable defibrillator indicated for patients with left ventricle ejection fraction ≤ 35% and cardiac resynchronization therapy for those with QRS ≥ 130 ms and evidence of left bundle branch block. Nevertheless, only a third of patients meet these criteria and a high percentage of patients are non-responders in terms of improving symptoms. Nowadays, in patients with symptomatic heart failure with ejection fraction between 25% and 45% and QRS < 130 ms, not eligible for cardiac resynchronization, the cardiac contractility modulation (CCM) represents a concrete therapeutic option, having proved to be safe and effective in reducing hospitalizations for heart failure and improving symptoms, functional capacity, and quality of life. The aim of this review is therefore to summarize the pathophysiological mechanisms, the current indications, and the recent developments regarding the new applications of the CCM for patients with chronic heart failure.

Cardiac contractility modulation for the treatment of heart failure with reduced ejection fraction

There has been a progressive evolution in the management of patients with chronic heart failure and reduced ejection fraction (HFrEF), including cardiac resynchronisation therapy (CRT) in those that fulfil pre-defined criteria. However, there exists a significant proportion with refractory symptoms in whom CRT devices are not clinically indicated or ineffective. Cardiac contractility modulation (CCM) is a novel therapy that incorporates administration of non-excitatory electrical impulses to the interventricular septum during the absolute refractory period. Implantation is analogous to a traditional transvenous pacemaker system, but with the use of two right ventricular leads. Mechanistic studies have shown augmentation of left ventricular contractility and beneficial global effects on reverse remodeling, primarily through alterations in calcium handling. This appears to occur without increasing myocardial oxygen consumption. Data from clinical trials have shown translational improvements in functional capacity and quality of life, though long-term outcome data are lacking. This review explores the rationale, evidence base and limitations of this nascent technology.

Does glucagon have a positive inotropic effect in the human heart?

Glucagon is considered to exert cardiostimulant effects, most notably the enhancement of heart rate and contractility, due to the stimulation of glucagon receptors associated with Gs protein stimulation which causes adenylyl cyclase activation and the consequent increase in 3′,5′-cyclic adenosine monophosphate production in the myocardium. These effects have been extensively demonstrated in experimental studies in different animal species. However, efforts to extrapolate the experimental data to patients with low cardiac output states, such as acute heart failure or cardiogenic shock, have been disappointing. The experimental and clinical data on the cardiac effects of glucagon are described here.

Cardiac contractility modulation improves left ventricular systolic function partially via miR-25 mediated SERCA2A expression in rabbit trans aortic constriction heart failure model

The purpose of this study was to investigate the underlying mechanism of cardiac contractility modulation (CCM) in improving trans aortic constriction (TAC)-induced heart failure (HF) left ventricular (LV) systolic function. A total of 25 New Zealand white rabbits were randomly divided into 5 groups: sham operation group (SHM), TAC-induced HF group (HF), TAC-induced HF followed by CCM stimulation group (HF + CCM), TAC-induced HF followed by injection of anti-miR-25 group (HF + anti-miR-25), TAC-induced HF followed by CCM stimulation and AAV9-miR-25 injection group (HF + CCM + miR-25). CCM current was performed 6 hours a day for 4 weeks. The left ventricle ejection fraction (LVEF) was measured by ultrasound. Reverse transcription-polymerase chain reaction (RT-PCR) and Western blot were used for measuring RNA and protein levels. The sarcoplasmic reticulum calcium ATPase (SERCA2A) and LVEF were reduced, while the miR-25 expression was improved in HF group compared to SHM group. Conversely, the SERCA2A and LVEF were improved, and the miR-25 reduced in the HF + CCM and the HF + anti-miR-25 groups compared to the HF group. Moreover, the SERCA2A and LVEF were reduced, while the miR-25 was improved in the HF + CCM + miR-25 group compared to the HF + CCM group. CCM is a potentially effective procedure for improving LV systolic function, which might partially by inhibiting miR-25 expression, further improved SERCA2A expression in TAC HF models.

Post-extrasystolic Potentiation: Link between Ca(2+) Homeostasis and Heart Failure?

Post-extrasystolic potentiation (PESP) describes the phenomenon of increased contractility of the beat following an extrasystole and has been attributed to changes in Ca(2+) homeostasis. While this effect has long been regarded to be a normal physiological phenomenon, a number of reports describe an enhanced potentiation of the post-extrasystolic beat in heart failure patients. The exact mechanism of this increased PESP is unknown, but disruption of normal Ca(2+) handling in heart failure may be the underlying cause. The use of PESP as a prognostic marker or therapeutic intervention have recently regained new attention, however, the value of the application of PESP in the clinic is still under debate. In this review, the mechanism of PESP with regard to Ca(2+) in the normal and failing heart will be discussed and the possible diagnostic and therapeutic role of this phenomenon will be explored.

Heart Failure With Reduced Ejection Fraction And A Narrow QRS Complex: Combination Of A Subcutaneous Defibrillator With Cardiac Contractility Modulation

Cardiac contractility modulation (CCM) is a relatively new electrical therapy for heart failure patients with reduced ejection fraction. The majority of patients eligible for CCM will also need an implantable cardioverter-defibrillator (ICD). To-date, three pacing electrodes are mandatory for CCM therapy because the current CCM signal delivery algorithm requires sequential intracardiac sensing of a p-wave, followed by appropriately timed ventricular activation by the two ventricular septal leads. As there is no device combining CCM with ICD functions, most CCM patients will need multiple intracardiac electrodes, which increase the cumulative risk for complications such as systemic infections, thrombosis of central venous lines, insulation failures or lead fractures. The long-term complications associated with trans-venous ICD leads have led to the development of a totally subcutaneous implantable cardioverter-defibrillator (S-ICD). In this essay the two technologies CCM and S-ICD are reviewed. Additionally, we present their successful combination on the basis of a case report on the first patient receiving both devices.

Increased longitudinal contractility and diastolic function at rest in well-trained amateur Marathon runners: a speckle tracking echocardiography study

Background

Regular physical activity reduces cardiovascular risk. There is concern that Marathon running might acutely damage the heart. It is unknown to what extent intensive physical endurance activity influences the cardiac mechanics at resting condition.

Methods

Eighty-four amateur marathon runners (43 women and 41 men) from Berlin-Brandenburg area who had completed at least one marathon previously underwent clinical examination and echocardiography at least 10 days before the Berlin Marathon at rest. Standard transthoracic echocardiography and 2D strain and strain rate analysis were performed. The 2D Strain and strain rate values were compared to previous published data of healthy untrained individuals.

Results

The average global longitudinal peak systolic strain of the left ventricle was -23 +/- 2% with peak systolic strain rate -1.39 +/- 0.21/s, early diastolic strain rate 2.0 +/- 0.40/s and late diastolic strain rate 1.21 +/- 0.31/s. These values are significantly higher compared to the previous published values of normal age-adjusted individuals. In addition, no age-related decline of longitudinal contractility in well-trained athletes was observed.

Conclusions

There is increased overall longitudinal myocardial contractility at rest in experienced endurance athletes compared to the published normal values in the literature indicating a preserved and even supra-normal contractility in the athletes. There is no age dependent decline of the longitudinal 2D Strain values. This underlines the beneficial effects of regular physical exercise even in advanced age.

Cardiac contractility modulation increases action potential duration dispersion and decreases ventricular fibrillation threshold via β1-adrenoceptor activation in the crystalloid perfused normal rabbit heart

BACKGROUND/OBJECTIVES

Cardiac contractility modulation (CCM) is a new treatment being developed for heart failure (HF) involving application of electrical current during the absolute refractory period. We have previously shown that CCM increases ventricular force through β1-adrenoceptor activation in the whole heart, a potential pro-arrhythmic mechanism. This study aimed to investigate the effect of CCM on ventricular fibrillation susceptibility.

METHODS

Experiments were conducted in isolated New Zealand white rabbit hearts (2.0-2.5 kg, n=25). The effects of CCM (± 20 mA, 10 ms phase duration) on the left ventricular basal and apical monophasic action potential duration (MAPD) were assessed during constant pacing (200 bpm). Ventricular fibrillation threshold (VFT) was defined as the minimum current required to induce sustained VF with rapid pacing (30 × 30 ms). Protocols were repeated during perfusion of the β1-adrenoceptor antagonist metoprolol (1.8 μM). In separate hearts, the dynamic and spatial electrophysiological effects of CCM were assessed using optical mapping with di-4-ANEPPS.

RESULTS

CCM significantly shortened MAPD close to the stimulation site (Basal: 102 ± 5 [CCM] vs. 131 ± 6 [Control] ms, P<0.001). VFT was reduced during CCM (2.6 ± 0.6 [CCM] vs. 6.1 ± 0.8 [Control] mA, P<0.01) and was correlated (r(2)=0.40, P<0.01) with increased MAPD dispersion (26 ± 4 [CCM] vs. 5 ± 1 [Control] ms, P<0.01) (n=8). Optical mapping revealed greater spread of CCM induced MAPD shortening during basal vs. apical stimulation. CCM effects were abolished by metoprolol and exogenous acetylcholine. No evidence for direct electrotonic modulation of APD was found, with APD adaptation occurring secondary to adrenergic stimulation.

CONCLUSIONS

CCM decreases VFT in a manner associated with increased MAPD dispersion in the crystalloid perfused normal rabbit heart.

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.