Cardiac resynchronisation in mild heart failure: long-term survival

Heart failure with reduced ejection fraction continues to claim lives and diminish quality of life across Australia, where roughly half a million adults live with the condition and more than 60,000 new cases are diagnosed each year. Within that population, those whose symptoms are classified as New York Heart Association class I or II, often described in Australian clinics as the "walking wounded" because they remain functional but carry a reduced ejection fraction, have historically received less attention than their severely symptomatic counterparts. Yet the long-term survival benefit of cardiac resynchronisation therapy in mild heart failure is now firmly supported by extended follow-up of pivotal trials, prompting a rethink of who should receive a device.

The clinical question matters locally because the Australian healthcare system, anchored by Medicare and the Pharmaceutical Benefits Scheme alongside private insurers, supports high rates of device implantation through accredited centres in capital cities and regional hubs. Whether earlier intervention improves longevity in mildly symptomatic patients influences individual prognosis, resource allocation, waitlists for electrophysiology laboratories, and the design of shared-care follow-up clinics that bridge metropolitan teaching hospitals with rural general practices.

Recent long-term analyses, with follow-up extending beyond a decade in some cohorts, have begun to clarify the magnitude and durability of survival gains. These data carry implications for guidelines, reimbursement decisions by the Medical Services Advisory Committee, and the conversations clinicians have with patients who may not yet feel unwell enough to accept an implanted device.

Defining mild heart failure and patient eligibility

The term "mild heart failure" requires careful definition before its interaction with cardiac resynchronisation can be appreciated. In contemporary trials, mild heart failure typically refers to patients with a left ventricular ejection fraction of 30% or less who are categorised as NYHA class I or II, often in sinus rhythm with a QRS duration of 130 milliseconds or more and a left bundle branch block morphology. Many Australian patients fitting this profile are identified opportunistically, sometimes after an incidental finding on a transthoracic echocardiogram ordered for unrelated symptoms, or following referral from a rural GP who has picked up a slow recovery after an apparently minor cardiac event.

Eligibility for cardiac resynchronisation therapy in this group differs from that for severely symptomatic patients. The original landmark trials, MADIT-CRT and RAFT, enrolled predominantly class II patients and demonstrated that early device therapy reduced the combined endpoint of death or heart failure hospitalisation. Severely symptomatic class IV patients were excluded from those studies and continue to be considered separately, often for advanced therapies such as left ventricular assist devices or transplant assessment at quaternary centres such as The Alfred in Melbourne or St Vincent's in Sydney.

Risk stratification in mild heart failure also benefits from ancillary electrocardiographic data. Analyses of repolarisation abnormalities and QRS fragmentation in at-risk populations, including those with comorbid renal impairment, are increasingly informing clinical decisions, as discussed in a recent feature on electrocardiographic markers of arrhythmic risk. Embedding these markers into pre-implant assessment pathways may help Australian electrophysiologists refine who truly benefits from early resynchronisation.

Mechanisms of benefit in less symptomatic patients

The biological rationale for cardiac resynchronisation therapy in mild heart failure rests on reversing the adverse remodelling that begins long before symptoms become overt. Dyssynchronous contraction promotes progressive ventricular dilation, mitral annular dilatation, and secondary functional mitral regurgitation, each of which accelerates the trajectory toward overt pump failure. By restoring coordinated mechanical activation, the device reduces wall stress, improves myocardial efficiency, and stabilises or reverses chamber enlargement over months to years.

In patients with mild symptoms, the substrate is less damaged and the opportunity to halt progression is greater. Australian imaging studies conducted through collaborative networks such as the Baker Heart and Diabetes Institute have shown that even modest reverse remodelling, defined as a five-point increase in left ventricular ejection fraction, translates into meaningful gains in functional capacity and event-free survival. Local researchers have also contributed to understanding the role of myocardial scar burden, assessed by cardiac MRI, in predicting response.

The pacing configuration matters as well. Modern devices offer multipoint pacing and adaptive algorithms that adjust atrioventricular and interventricular delays automatically. Trials such as MORE-CRT MPP have suggested incremental benefit in selected patients, although the magnitude is modest and the cost-effectiveness in an Australian context, where device prices and procedural reimbursement are negotiated federally, continues to be debated.

Long-term survival evidence from extended follow-up

The strongest evidence for survival benefit in mild heart failure comes from extended follow-up of the MADIT-CRT and RAFT trials. In RAFT, the original five-year analysis demonstrated a 16% relative reduction in all-cause mortality among class II patients receiving cardiac resynchronisation therapy with defibrillator compared with ICD alone. Long-term extension to roughly eight years confirmed durability, with persistent survival gains in the resynchronisation arm and a hazard ratio for death that remained below one even after adjusting for crossover and subsequent device upgrades.

More recent pooled analyses and individual patient-data meta-analyses have reported that the absolute survival benefit of cardiac resynchronisation therapy in mild heart failure is in the order of four to seven additional life-years per 100 patients treated over a decade of follow-up. These figures are particularly relevant for Australian cardiologists counselling relatively young patients with non-ischaemic cardiomyopathy, in whom the cumulative lifetime gain can be substantial.

Real-world registry data from the European Society of Cardiology's CRT Survey and parallel work within the ANZACS-QI framework have shown that outcomes in everyday practice approximate, though slightly trail, those achieved in randomised trials. In Australia, where implant volumes per centre are smaller than in many European countries, attention to procedural volume, operator experience, and standardised post-implant follow-up is essential to translate trial efficacy into real-world effectiveness.

Australian real-world practice and health system considerations

Australian practice patterns for cardiac resynchronisation therapy in mild heart failure have evolved in step with international evidence, though local factors shape access. Device implantation is concentrated in metropolitan tertiary centres, with outreach services reaching regional Queensland, Western Australia, and Tasmania through visiting specialist networks and telehealth-supported follow-up. Patients in the Northern Territory, where distances between communities are vast, may wait longer for elective procedures, and there is ongoing investment in Indigenous cardiac care programs that aim to close the gap in heart failure outcomes between Aboriginal and Torres Strait Islander peoples and the broader population.

Reimbursement pathways through Medicare require adherence to specific indication criteria, including QRS morphology, ejection fraction thresholds, and documented optimal medical therapy for at least three months. These criteria broadly align with European Society of Cardiology guidelines but incorporate local nuances around which patients qualify for defibrillator backup. The Therapeutic Goods Administration's approval of specific device models and firmware updates also influences when newer technologies such as quadripolar leads or conduction system pacing become routinely available outside major teaching hospitals.

Multidisciplinary heart failure clinics, often nurse-led and integrated with cardiology, pharmacy, and primary care, play a critical role in identifying mildly symptomatic patients who may benefit from referral to electrophysiology. Programs at Westmead, Monash Heart, and the Royal Adelaide Hospital have published data showing that structured screening identifies a meaningful proportion of class II patients with dyssynchrony who would otherwise not be referred for device therapy. Embedding resynchronisation assessment into routine heart failure reviews represents an achievable path to earlier intervention.

Choosing therapy wisely and communicating with patients

Shared decision-making is the cornerstone of offering cardiac resynchronisation therapy to patients with mild symptoms, many of whom feel relatively well and may be reluctant to undergo an invasive procedure with potential complications. Australian clinicians increasingly draw on decision aids that present absolute benefit, procedural risk, and lifestyle implications in plain language, often with input from cardiac nurses, Aboriginal health workers where relevant, and culturally appropriate resources for patients from non-English-speaking backgrounds.

The conversation typically begins with clarification of what the device can and cannot achieve. While survival benefit is supported by robust long-term data, the magnitude varies with QRS duration, morphology, sex, and underlying aetiology. Women, who have been underrepresented in many historical trials, appear to derive proportionally greater benefit in some analyses, and Australian cardiologists are paying closer attention to this disparity. Practical considerations such as driving restrictions, which in Australia are governed by state-based transport authority guidelines, and the small but real risk of device infection or lead failure, must also be addressed.

Younger patients with non-ischaemic cardiomyopathy and minimal comorbidity stand to gain the most lifetime benefit, while older patients with extensive comorbidity may be appropriately directed toward optimal medical therapy alone. The art of practice lies in integrating trial evidence, registry data, and the patient's own priorities. For those seeking the latest peer-reviewed syntheses on related arrhythmic risk stratification and device-based therapies, the journal's homepage curates themed collections and ahead-of-print articles relevant to everyday decision-making.

Researchers and trainees with original data on Australian resynchronisation cohorts, novel imaging predictors of response, or health economic analyses are encouraged to submit their work and contribute to the evolving evidence base that guides care for mildly symptomatic patients across the region.