Conventional biventricular pacing is still preferred to conduction system pacing for atrioventricular block in patients with reduced ejection fraction and narrow QRS

It is well established that right ventricular pacing is detrimental in patients with reduced cardiac function who require ventricular pacing (VP), and alternatives nowadays are comprised of biventricular pacing (BiVP) and conduction system pacing (CSP). The latter modality is of particular interest in patients with a narrow baseline QRS as it completely avoids, or minimizes, ventricular desynchronization associated with VP. In this article, experts debate whether BiVP or CSP should be used to treat these patients.

[Cardiac contractility modulation for treatment of chronic heart failure]

The worldwide prevalence of heart failure is 1-2% with a portion of >10% in patients older than 70 years. In addition to treatment of causal determined factors and lifestyle modification, basic treatment consists of guideline-directed medical therapy with angiotensin-converting enzyme inhibitors (ACE), β‑blockers (BB), mineralocorticoid receptor antagonists (MRA), diuretics, digitalis (class IIb recommendation), angiotensin receptor blockers (ARB), Iƒ-channel blockers plus recently recommended in the guidelines angiotensin receptor neprilysin inhibitor (ARNI) to substitute the ACE inhibitor (class I b). Cardiac contractility modulation (CCM) is a device-based electrical therapy for the treatment of refractory heart failure symptoms. CCM signals are relatively high intensity, nonexcitatory signals applied during the absolute refractory period that have been shown to enhance the strength of left ventricular (LV) contraction and improve exercise tolerance and quality of life. The mechanisms of action appear to involve effects on myocardial gene expression and normalization of myocardial key-proteins. So far, more than 3500 CCM devices have been implanted worldwide. For patients with symptomatic heart failure and narrow QRS complex, CCM is together with baroreceptor activation the only additive electrical therapy which had been approved in Germany. Actually, for the first time, CCM has been referenced in the current Heart Failure Guidelines. Prognostic data with regard to mortality are currently being evaluated in case series; some of which have since been published. Approval by the US Food and Drug Administration (FDA) is expected within the next months.

[Cardiac contractility modulation]

Cardiac contractility modulation (CCM) is a device-based electrical therapy for the additive treatment of chronic drug-refractory heart insufficiency. High-amplitude signals are applied during the absolute refractory period and have been shown to enhance the strength of left ventricular (LV) contraction and improve exercise tolerance and quality of life. The mechanisms of action appear to involve effects on myocardial gene expression and on normalization of key myocardial proteins. So far, more than 3500 CCM devices have been implanted worldwide. For patients with therapy refractory heart insufficiency and narrow QRS complex, CCM is together with baroreceptor activation the only additive electrical therapy which had been approved in Germany. For the first time CCM has been referenced in the current guidelines on cardiac insufficiency. Prognostic data with respect to mortality have been evaluated in case series. Ongoing randomized trials and registries will address these specific endpoints and have to a significant extent already been recently published. A Food and Drug Administration (FDA) approval is expected within the next few months.

The interaction of QRS duration with cardiac magnetic resonance derived scar and mechanical dyssynchrony in systolic heart failure: Implications for cardiac resynchronization therapy

Background

Trials using echocardiographic mechanical dyssynchrony (MD) parameters in narrow QRS patients have shown a negative response to CRT. We hypothesized MD in these patients may relate to myocardial scar rather than electrical dyssynchrony.

Methods

We determined the prevalence of cardiac magnetic resonance (CMR) derived measures of MD in 130 systolic heart failure patients with both broad (≥ 130 ms - BQRS) and narrow QRS duration (< 130 ms - NQRS). We assessed whether late gadolinium enhancement derived scar might explain the presence of MD amongst narrow QRS patients. Dyssynchrony was calculated on the basis of a systolic dyssynchrony index (SDI).

Results

Fifty-nine patients (45%) had a NQRS and the remaining had QRS ≥ 130 ms (BQRS group). 25% of NQRS patients had MD based on SDI. In all narrow and broad QRS patients with MD there was a significantly lower scar volume than those without MD (7.4 ± 10.5% vs 13.7 ± 13.3% vs. p < 0.01). This was the case in the BQRS group with a significantly lower scar burden in patients with MD (5.0 ± 7.7% vs 15.4 ± 15.6%, p < 0.01). Notably in the NQRS group this difference was absent with an equal scar burden in patients with MD 13.3 ± 13.9% and without MD 12.5 ± 11%, p = 0.92.

Conclusions

25% of patients with systolic heart failure and a NQRS (< 130 ms) have CMR derived mechanical dyssynchrony. Our findings suggest MD in this group may be secondary to myocardial scar rather than electrical dyssynchrony and therefore not amenable to correction by CRT. This may give insight into non-response and potential harm from CRT in this group.

Multipoint Pacing versus conventional ICD in Patients with a Narrow QRS complex (MPP Narrow QRS trial): study protocol for a pilot randomized controlled trial

Background

Despite an intensive search for predictors of the response to cardiac resynchronization therapy (CRT), the QRS duration remains the simplest and most robust predictor of a positive response. QRS duration of ≥ 130 ms is considered to be a prerequisite for CRT; however, some studies have shown that CRT may also be effective in heart failure (HF) patients with a narrow QRS (<130 ms). Since CRT can now be performed by pacing the left ventricle from multiple vectors via a single quadripolar lead, it is possible that multipoint pacing (MPP) might be effective in HF patients with a narrow QRS. This article reports the design of the MPP Narrow QRS trial, a prospective, randomized, multicenter, controlled feasibility study to investigate the efficacy of MPP using two LV pacing vectors in patients with a narrow QRS complex (100–130 ms).

Methods

Fifty patients with a standard ICD indication will be enrolled and randomized (1:1) to either an MPP group or a Standard ICD group. All patients will undergo a low-dose dobutamine stress echo test and only those with contractile reserve will be included in the study and randomized. The primary endpoint will be the percentage of patients in each group that have reverse remodeling at 12 months, defined as a reduction in left ventricular end-systolic volume (LVESV) of >15% from the baseline.

Discussion

This feasibility study will determine whether MPP improves reverse remodeling, as compared with standard ICD, in HF patients who have a narrow QRS complex (100–130 ms).

Trial registration

ClinicalTrials.gov, NCT02402816. Registered on 25 March 2015.

Electronic supplementary material

The online version of this article (doi:10.1186/s13063-016-1698-1) contains supplementary material, which is available to authorized users.