Small Perimembranous VSD—Small in Size, but How Significant in Clinical Course?

Abstract

Small perimembranous ventricular septal defects (PM-VSDs) are commonly regarded as relatively benign congenital cardiac lesions. Because they are usually restrictive, impose little hemodynamic burden, and may decrease in size or close spontaneously, conservative management is often appropriate. Yet, “small” should not be equated with “clinically insignificant.” The anatomical proximity of a PM-VSD to the aortic valve, right ventricular outflow tract, and cardiac conduction system creates the potential for complications that may emerge despite an initially restrictive physiology. The prospective study by Ahmed et al., involving 550 children managed at a tertiary cardiac center in Pakistan, therefore addresses an important and clinically relevant question in a population for which longitudinal data remains limited [1]. The findings are noteworthy, but they also require careful interpretation. Ahmed et al. reported spontaneous closure in 12.54% of children, persistence of the defect in 57.2%, and intervention in 22.54% [1]. These proportions differ from some longer-term observational experiences. In a recent 30-year study of 448 children with isolated PM-VSDs, restrictive defects constituted 82.1% of the cohort, spontaneous closure occurred in 23.3%, and approximately 22% underwent surgical or transcatheter intervention. Most restrictive defects nevertheless followed a favorable clinical course, with intervention principally required in patients developing significant hemodynamic or valvular consequences [2]. The comparison is instructive: estimates of spontaneous closure, persistence, and intervention cannot be interpreted independently of age at enrollment, referral patterns, case definition, and—most importantly—duration of observation. A fundamental issue is therefore what is meant by a “small” PM-VSD. Ahmed et al. defined a small defect as measuring less than 50% of the aortic annulus diameter, with a peak Doppler gradient ≥50 mmHg and no pulmonary hypertension or significant left-sided chamber enlargement [1]. This definition appropriately incorporates restrictive physiology, but a high Doppler gradient primarily reflects the pressure relationship across the defect rather than anatomical size alone. For meaningful comparison across studies, absolute defect diameter should ideally be reported alongside its relationship to the aortic annulus and, where feasible, body-size-adjusted measurements. Serial assessment of ventricular dimensions, shunt magnitude, Doppler characteristics, and aortic valve morphology would further help distinguish a truly small, hemodynamically insignificant defect from one that is anatomically small but clinically evolving. Perhaps the most important issue is the short duration of follow-up. The mean follow-up in the present cohort was only 3.33 months, with an interquartile range of 1.8–5.2 months [1]. Such a period provides valuable information about early clinical outcomes, but it cannot adequately characterize the natural history of a congenital lesion whose evolution may extend over many years. In a cohort of 1,823 children followed for as long as 26 years, with a median follow-up of four years, spontaneous closure of perimembranous defects occurred in 12.5%, and the investigators emphasized the generally favorable tendency of many isolated VSDs to decrease in size or close over time [3]. Accordingly, the 12.54% closure observed by Ahmed et al. should be understood as an early observed closure rate within the available follow-up window, rather than as a definitive estimate of spontaneous closure throughout childhood [1,3]. The same caution applies to the reported persistence rate: at approximately three months, “persistent” largely means “still present at early reassessment,” not necessarily persistent over the longer natural history of the lesion. An even more striking observation is the reported 48.72% prevalence of aortic valve prolapse with aortic regurgitation [1]. Aortic valve involvement is a recognized and clinically important complication of PM-VSD, and its development can transform an otherwise restrictive defect into one requiring intervention. However, the magnitude reported in this cohort is unusually high. In a previous study of 1,096 patients with VSD, aortic valve prolapse occurred in 10.6% of patients with perimembranous defects and aortic regurgitation in 6.8% [4]. Importantly, valvular abnormalities in longitudinal cohorts may be present at the initial assessment or develop subsequently [4]. This distinction is critical when interpreting the present study. The key question, therefore, is not simply how many children had aortic valve prolapse or regurgitation, but when these abnormalities appeared. Were they absent at enrollment and newly detected during prospective surveillance, or were they already present when the children entered the cohort? The same question applies to right ventricular outflow tract obstruction, infective endocarditis, and rhythm or conduction abnormalities. Ahmed et al. describe these as complications observed during follow-up, but without clearly separating prevalent abnormalities at baseline from incident complications arising after enrollment, it is difficult to infer short-term disease progression [1]. Given a mean observation period of only 3.33 months, such differentiation becomes particularly important. If a substantial proportion of these abnormalities were already present at baseline, the reported percentages would more accurately represent the burden of associated abnormalities in a tertiary referral cohort rather than the incidence of complications caused by progression during short-term follow-up. This issue also influences interpretation of the relatively high intervention rate. Ahmed et al. report that 124 children (22.54%) underwent intervention, including 78 transcatheter closures and 46 surgical patch closures [1]. An intervention rate of this magnitude during such a short follow-up interval raises the possibility that at least some children entered the study with established or evolving indications for closure rather than developing them de novo during observation. Clearly reporting the clinical and echocardiographic status at enrollment, the timing of each complication, and the interval from enrollment to intervention would substantially strengthen interpretation of these findings. The tertiary referral setting provides another important explanation. A high-volume specialist cardiac center is unlikely to receive a population representative of all children with small restrictive PM-VSDs. Children with uncomplicated lesions that remain clinically silent may be less likely to reach tertiary care, whereas those with persistent murmurs, suspected valve abnormalities, evolving obstruction, or other complications may be preferentially referred. The authors appropriately acknowledge referral bias [1]. Consequently, the high complication and intervention rates should not be extrapolated directly to community populations or interpreted as indicating that nearly half of all children with small PM-VSDs will develop aortic valve disease. These methodological concerns, however, should not obscure the study's important clinical message. A restrictive PM-VSD should not automatically be dismissed simply because the defect is anatomically small or associated with a high Doppler gradient. Follow-up should consider not only defect size but also aortic cusp morphology and regurgitation, ventricular dimensions, subaortic and right ventricular outflow anatomy, shunt characteristics, and rhythm or conduction abnormalities. In this context, conservative management should mean active surveillance rather than therapeutic neglect. At the same time, surveillance should be proportionate to risk. The available evidence does not support treating every small restrictive PM-VSD as a lesion destined for complication. Rather, the clinical objective should be to distinguish the majority of children likely to experience a stable or favorable course from the smaller subgroup demonstrating anatomical or physiological features associated with progression. This risk-stratified perspective avoids two opposite errors: unnecessary intervention in an otherwise benign restrictive defect and delayed recognition of a small defect that is beginning to affect the aortic valve or surrounding structures. Future studies from Pakistan and similar settings could make an important contribution by establishing multicenter prospective cohorts beginning in infancy and continuing through childhood and adolescence. Standardized reporting should distinguish baseline abnormalities from incident complications, document absolute and indexed VSD dimensions, characterize aortic cusp anatomy and regurgitation severity longitudinally, and record the precise timing and indication for intervention. Longer follow-up would permit more reliable estimation of spontaneous closure and complication rates, while multivariable analyses could identify clinical and echocardiographic predictors of spontaneous closure, progressive valve disease, RVOT obstruction, and eventual intervention. Ahmed et al. [1] have provided valuable prospective regional data and have drawn attention to an important clinical reality: a small PM-VSD is not necessarily a trivial PM-VSD. Nevertheless, the short follow-up period, tertiary referral setting, and particularly the absence of a clear distinction between baseline and newly developed complications limit interpretation of the reported outcomes as the natural history of these lesions. Their findings should therefore be viewed as an important clinical signal rather than a definitive description of long-term disease trajectory. The broader evidence suggests that many restrictive PM-VSDs follow a favorable course, while a clinically meaningful minority develop complications requiring intervention [2-4]. The challenge for pediatric cardiology is consequently not whether every small PM-VSD should be closed, but which small defects can be safely observed, which require closer surveillance, and which are beginning to declare themselves as clinically significant lesions requiring timely intervention. References Ahmed MA, Korejo HB, Shaikh A, Kumari V, Sathio SN, Khan MA, Shaikh AS. Natural course and clinical outcomes of small perimembranous ventricular septal defects in children at a tertiary cardiac center: a prospective cohort study. Pak Heart J. 2026;59(04):1252-1259. DOI: 10.47144/phj.v59i4.3757 Karagözlü S, Ramoğlu MG, Alimoğlu B, Uçar T, Atalay S, Tutar E. Natural history and management of restrictive perimembranous ventricular septal defects in children: insights from a 30-year experience. 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