Subaortic stenosis and recurrence: what we can influence and what nature decides Free

In their retrospective review of 120 children undergoing primary repair for ‘simple’ subaortic stenosis over a 26-year time span without operative mortality, Bandara et al. [1] found recurrent outflow tract obstruction in 18% (n = 20) of their patients at a median follow-up time of 13 years, of whom 15 underwent reoperations. Preoperatively, either trivial or mild preoperative aortic insufficiency was present in the majority (n = 86), remained in only 63 children in the immediate postoperative period and persisted again in 86 at the last follow-up. Of these, only 8 had moderate aortic insufficiency, none of whom required surgery for aortic valve insufficiency. A higher pre-operative peak left ventricular outflow tract (LVOT) gradient and the presence of a bicuspid aortic valve were predictors of reintervention for recurrent outflow stenosis. Using systematic subaortic membrane excision/peeling and septal myectomy in 93% of cases, the authors are to be commended for their excellent results, including a low incidence of major complications (only 1 heart block, 0.8%) and freedom from reoperation of 99%, 94%, 93% and 90% at 1, 3, 5 and 10 years, respectively [1].

Since anatomical (versus functional) subaortic stenosis rarely occurs in newborns and is progressive in nature, it is commonly regarded as an acquired lesion, and the result of sheer stress forces exerted on individual or serial components in the left outflow tract [2–6]. Presumed aetiologies include fixed morphological variants (acute aorto-septal angle, small aortic annulus, multilevel obstruction) [1–6], and newly suggested although by no means proven by the authors [1], the presence of a bicuspid aortic valve (only 10% of patients in their series had bicuspid aortic valves, and patients with severe valvar aortic stenosis were excluded from the analysis).

Described risk factors for recurrent left outflow tract obstruction after primary repair of ‘simple’ subaortic stenosis and need for reoperation have included younger age at primary operation, high preoperative outflow gradients, significant residual postoperative gradients and significant aortic insufficiency [1–5]. However, truly identifying the patients who are destined to develop recurrent obstruction has remained elusive [4, 6], and this knowledge gap continues to preclude a standardized approach as to how extensive relief techniques should be employed at primary repair. With the goal of reducing the need for reoperation, some have advocated more aggressive myectomy, but at the cost of a higher rate of heart block with pacemaker implantation, or postoperative aortic insufficiency [3]. Conversely, more extensive strategies, such as the modified Konno procedure, are judged too radical and not yet recommended as a primary approach in the setting of ‘simple’ LVOT obstruction [6], but rather reserved for redo settings in the hope of a more durable solution. So where do we stand? How aggressive should we be at primary repair, and at what cost to the patient (a pacemaker, a new aortic valve, a new pulmonary valve, multiple hospitalizations)? How much is predetermined by forces (angles) of nature, and to what lengths should we go to alter ‘corrected’ natural history?

While more aggressive standard surgical membrane resection + myectomy could delay recurrence to very low levels [1], durable relief, no matter how aggressive the myectomy, may not be attainable in some children. What nature dictates in certain forms and shapes, may probably only be palliated, short of more radical procedures such as the modified Konno or even Ross/Konno procedures, as was performed in 4 patients in this series in a redo setting [1]. Despite improving results and satisfactory long-term outcomes, it seems high time for a better understanding of the initial hurdles imposed by nature that induce stenosis in the first place. Should we continue just putting on a band-aid (membrane resection) for what seems a small anatomical target, or can we justify going all out with a major undertaking (Ross/Konno)? Only through more accurate definition of the mechanisms leading to the genesis and then recurrence of LVOT obstruction, can we better standardize the extent of our surgical approach at primary repair for ‘simple’ subaortic stenosis.

Presented at the EJCTS-2023-100210R2.

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