Cardiac Contractility Modulation (CCM)

Details

Cardiac contractility modulation (CCM; Impulse Dynamics OPTIMIZER Smart) delivers high-voltage nonexcitatory electrical pulses to the right ventricular septum during the absolute refractory period — a window when the cardiomyocyte cannot be depolarised. Because pulses do not trigger an action potential, there is no pacing output or arrhythmia risk. The pulses enhance intracellular calcium handling and phospholamban phosphorylation, improving contractile force without increasing myocardial oxygen demand.

Target population: Symptomatic HFrEF (LVEF 25–45%, NYHA II–III) with narrow QRS (<130ms) who are NOT candidates for CRT. CCM fills a specific gap for the ~50% of HF patients with QRS <130ms who cannot benefit from CRT.

Regulatory status: FDA-approved (2019) as an adjunct to GDMT in eligible HFrEF patients.

Key trial: FIX-HF-5C RCT (n=160, LVEF 25–45%, QRS <130ms, NYHA III): significant improvement in pVO₂ (+1.1 mL/kg/min, P=0.02) and KCCQ (+9.7 points, P<0.001) vs control at 24 weeks. No mortality benefit demonstrated.

Key Facts

CCM Appropriateness — AUC 2025 Ratings

All CCM scenarios rated May Be Appropriate (M 4–5) — no scenario reaches Appropriate (A ≥7):

• NYHA II + LVEF 25–45% + QRS <120ms + ≥3 months GDMT: M(5) (sources/icd-crt-auc-2025, rating: high)
• NYHA III + LVEF 25–45% + QRS <120ms + ≥3 months GDMT: M(5) (sources/icd-crt-auc-2025, rating: high)
• NYHA III + LVEF 25–45% + QRS 120–129ms + ≥3 months GDMT: M(4) — slightly lower given proximity to CRT threshold (sources/icd-crt-auc-2025, rating: high)
• Concurrent ICD implantation with CCM is feasible (separate device); ICD indication assessed independently (sources/icd-crt-auc-2025, rating: high)

Mechanism

• Nonexcitatory pulses during absolute refractory period → enhanced SERCA2a activity → improved SR Ca²⁺ reuptake → increased contractility
• Delivered via two right ventricular septal leads (bipolar sensing + delivery) + pulse generator implanted subcutaneously
• Does not alter QRS morphology or create dyssynchrony (no ventricular activation triggered)
• Programmed to deliver 7 hours per day of therapy (intermittent application)

Clinical Evidence

• FIX-HF-5C (pivotal RCT, n=160): LVEF 25–45%, NYHA III, QRS <130ms; pVO₂ +1.1 mL/kg/min (P=0.02); KCCQ +9.7 points (P<0.001); 6MWD: no significant difference (sources/icd-crt-auc-2025, rating: high)
• FIX-HF-5 (earlier RCT, n=428): Prespecified subgroup QRS <130ms showed pVO₂ improvement; full cohort primary endpoint missed
• CCM-REG registry (real-world, n=140): KCCQ improvement sustained to 24 months in responders; approximately 60–70% symptomatic response rate
• No RCT has demonstrated mortality benefit; benefit is QoL and exercise capacity driven

Eligibility Criteria

1. LVEF 25–45% (too low for CRT candidacy at 36–45%, or too narrow QRS)
2. QRS <130ms (excluding patients meeting CRT criteria)
3. NYHA class II or III on optimal GDMT ≥3 months
4. Sinus rhythm (AF does not exclude CCM but reduces signal reliability)
5. Absence of ventricular capture during CCM delivery (must verify refractory period timing)

Contradictions / Open Questions

• May Be Appropriate — not Appropriate: No CCM scenario reaches A in AUC 2025. This reflects the single pivotal RCT (FIX-HF-5C, n=160), no mortality benefit, and absence of long-term data. The M(4–5) rating acknowledges FDA approval and symptom benefit but requires shared decision-making.
• ICD concurrent implantation: CCM is a separate device from ICD. Many patients eligible for CCM also meet ICD criteria (LVEF ≤35%). The optimal sequencing (CCM alone vs CCM + ICD) is not addressed in the AUC; shared decision-making is required.
• AF and CCM: CCM delivers pulses timed to the cardiac refractory period using detected R-waves; AF with irregular rhythm challenges timing accuracy. Real-world performance in AF is not well-characterised.
• Responder prediction: No validated biomarker or imaging predictor of CCM response. Echo-based assessment of mechanical dyssynchrony or beta-adrenergic receptor density may identify future responders.
• Narrow QRS HF — is CCM equivalent to GDMT optimisation? No trial has compared CCM to SGLT2i + sacubitril–valsartan titration in the QRS <130ms population. It is plausible that modern GDMT is superior for symptom improvement.

Connections

• Related to entities/ICD — CCM and ICD are often implanted concurrently in LVEF ≤35% patients; different devices and mechanisms
• Related to entities/CRT — CCM is the device option for patients NOT eligible for CRT (narrow QRS); explicitly complementary populations
• Related to entities/Heart-Failure — CCM fills a gap for symptomatic HFrEF with narrow QRS not amenable to CRT
• Related to entities/HFpEF — LVEF 25–45% overlaps lower HFmrEF range; CCM studies excluded preserved EF
• Related to concepts/Pharmacogenomics-in-HF — beta-adrenergic receptor signalling as CCM mechanism

Sources

• sources/icd-crt-auc-2025 — ACC/AHA/HRS 2025 AUC (primary source; FIX-HF-5C data)