Heart failure involving the systemic right ventricle (sRV) remains one of the major challenges in the management of adults with complex congenital heart disease. Although cardiac resynchronisation therapy (CRT) has transformed the treatment of many patients with heart failure (HF) and left ventricular dysfunction, its role in this particular population remains controversial. In this study, Fusco et al. analyse the largest international cohort reported to date in an attempt to determine whether this strategy can modify the clinical course of patients with an sRV.
Those of us involved in the follow-up of patients with congenitally corrected transposition of the great arteries (ccTGA) or TGA repaired with an atrial switch procedure are very familiar with a recurring clinical reality: the sRV eventually pays the price for performing, over several decades, a function for which it was never designed.
The search for treatments capable of slowing this progression has become a major priority in recent years. Accumulating experience with newer HF therapies has generated some optimism, but electrical therapies remain surrounded by uncertainty. The pathophysiological rationale supporting CRT is appealing, particularly in patients with ventricular dysfunction and conduction abnormalities. However, clinical experience has been considerably less convincing than in conventional HF.
The authors present an international, multicentric, retrospective study including 1721 adults with an sRV from 33 specialised centres. Of these, 105 underwent successful CRT implantation.
The primary endpoints were overall survival and survival free from HF hospitalisation. The secondary endpoint was a composite of death, HF hospitalisation, heart transplantation, mechanical circulatory support and ventricular arrhythmic events. To reduce baseline differences between groups, propensity score matching was performed using the main clinical variables associated with prognosis.
After a median follow-up of 4.6 years, the electrical response to CRT was limited. QRS narrowing occurred predominantly in patients with previous ventricular pacing and was not accompanied by significant improvements in functional, biochemical or echocardiographic parameters. Device-related complications were also reported in approximately 10% of patients.
After propensity score adjustment, patients treated with CRT showed worse survival and lower event-free survival than matched controls. The authors therefore conclude that, in this cohort, CRT implantation was not associated with demonstrable clinical benefit in terms of either survival or HF outcomes.
COMMENTARY:
I must admit that this is one of those studies whose findings deserve careful consideration before drawing any rapid conclusions. At first glance, the results might suggest that CRT simply does not work in the sRV. However, the actual message is probably considerably more nuanced.
In clinical practice, we rarely consider CRT at an early stage in these patients. They usually reach this therapeutic option only after years of disease progression, multiple previous procedures, established ventricular dysfunction, significant tricuspid regurgitation, arrhythmias and, in many cases, recurrent HF admissions. It is therefore difficult to determine to what extent the poorer outcomes observed reflect a lack of treatment efficacy or simply the severity of the patients selected to receive CRT.
That said, there is one finding that I consider particularly relevant: most patients did not achieve true electrical resynchronisation. Significant QRS narrowing was uncommon, and functional improvement was virtually absent. Perhaps for years we have assumed that the criteria used to select candidates with a systemic left ventricle could also be applied to this population. This study reminds us once again that this is probably not the case. The sRV has completely different anatomy, geometry and activation patterns, and we may be trying to solve a different physiological problem using tools developed for another disease.
From a cardiac surgical perspective, the study also highlights an important reality that can sometimes be obscured by statistical analyses: CRT implantation in these patients is far from straightforward. Anatomical obstacles are common, access through the venous system may be challenging, and hybrid approaches or epicardial systems are not unusual. In this setting, even a moderate complication rate becomes clinically relevant, particularly when the expected benefit has not been clearly established.
Perhaps the most interesting question raised by this study is not whether we should implant fewer CRT devices, but whether some patients should receive them earlier. The authors note that many patients accumulated prolonged periods of conventional ventricular pacing before being upgraded to CRT. We cannot know whether earlier intervention would have altered the outcome, but it is a hypothesis that is difficult to ignore.
Finally, this publication comes at a time of growing interest in physiological pacing. Conduction system pacing (CSP) appears particularly attractive in a population in whom conventional CRT has produced modest results. In a few years, we may look back at these findings not as evidence of the failure of a therapeutic strategy, but rather as the end of one era and the beginning of another.
The central illustration of the article conveys the main message very clearly: patients treated with CRT did not experience an evident clinical advantage during follow-up.
REFERENCE:
Fusco F, Scognamiglio G, Dellborg M, Dehghani P, Jameson SM, Kay WA, et al. Cardiac resynchronisation therapy among adults with a systemic right ventricle: a multicentre experience. Heart. 2026;112:549-556. doi:10.1136/heartjnl-2025-326384.
