The Nuss procedure, the gold standard for chest wall remodeling, involves the insertion and rotation of a curved steel or titanium bar beneath the sternum through a small incision (1,2). To our knowledge, it has been rare to report pediatric patients with Nuss bars experiencing cardiac complications unprovoked by the procedure. This article presents a case of an adolescent with Marfan syndrome and pectus excavatum (PE) with 2 Nuss bars who underwent successful cardioversion for atrial fibrillation (AF). Informed consent was obtained from the patient’s guardian for publication.

A 14-year-old boy presented to the pediatric emergency department (ED) for evaluation of arrhythmia and pneumonia. The patient reported new palpitations beginning that morning, along with several days of afebrile upper respiratory symptoms. He was seen in a pediatrician’s office, diagnosed radiographically with right-sided pneumonia (Figure 1), and administered intramuscular ceftriaxone as an empirical antibiotic. An electrocardiogram (ECG) was performed at the office due to a heart rate of 189 beats/minute, which showed a rhythm resembling supraventricular tachycardia (SVT), prompting the pediatrician to refer him to the ED.

On presentation to our service in the ED, the office test results were not immediately available. The patient’s initial vital signs were as follows: blood pressure, 93/58 mmHg; heart rate, 200 beats/minute; respiratory rate, 40 breaths/minute; temperature, 37.2 °C; and oxygen saturation, 96% on room air. On physical examination, he appeared nontoxic, appropriately oriented with palpable pulses, and not in distress or reporting pain, but was noted to have a severe PE appearance on the chest wall. A guardian accompanying him clarified his medical history notable for Marfan syndrome, mitral regurgitation, and left ventricular dysfunction, for which he received cardiologist’s care at another institution. Additionally, he was reported status post Nuss bar placement 3 years prior for the PE, with the bar still retained in place and not yet scheduled for removal. Review of the chest radiograph from the office (Figure 1) revealed in fact 2 Nuss bars as well as posterior spinal rods. There was no prior history of arrhythmia or anticoagulation.

Initial point-of-care troponin concentration was 0.02 ng/mL (reference value, < 0.08 ng/mL). The patient’s rapid heart rate was noted to be irregular on a monitor. While arranging for a 12-lead ECG, this irregular rhythm was further visualized on a routine point-of-care ultrasonogram, indicating an intact cardiac function despite a limited visualization due to underlying PE. Given an ECG finding resembling SVT, but with subtle signs of irregularity more indicative of AF, a pediatric cardiologist was consulted, who subsequently confirmed that the ECG indicated AF with rapid ventricular response (Figure 2).

Synchronized cardioversion was recommended due to the unclear duration of the arrhythmia and an initial blood pressure that was low for his age (3). Defibrillator pads were placed in an anterior-posterior fashion, avoiding the locations of the bars as much as possible, which was additionally challenged by the underlying PE. He received 2 deliveries of standard weight-based cardioversion under 11 mg of etomidate, initially unsuccessful at 30 J and subsequently successful at 50 J (Figure 3). He recovered after the procedure well with improved vital signs. A formal echocardiogram was performed, which clarified a moderately depressed systolic function with mitral regurgitation. Initial laboratory findings drawn from the ED were as follows: white blood cells, 18.9 × 103 cells/μL; negative polymerase chain reaction for respiratory syncytial virus, influenza, and severe acute respiratory syndrome coronavirus 2; and peripheral blood culture that later yielded no growth.

The patient was hospitalized under the pediatric cardiology service for further monitoring. He had no recurrence of palpitations, arrhythmia on telemetry, or new-onset fever. He was started empirically on a 5-day azithromycin course with a repeat chest radiograph showing improved pulmonary findings. An echocardiogram was repeated on day 3, showing improved systolic function with the same degree of mitral regurgitation. After a further discussion with the primary cardiologist who followed up the patient at another institution, including consideration of mitral valve repair which had predated the ED visit, he was discharged in stable condition on the same day. He ultimately had both Nuss bars removed several months later.

AF is a frequent condition in adults who visit EDs, managed via medications or synchronized cardioversion, but is less frequently performed in pediatric patients without underlying cardiac conditions (4). PE is the most common congenital chest wall abnormality, occurring in approximately 1 in 1,000, typically an isolated finding, but also in neuromuscular or connective tissue diseases, such as Marfan syndrome (1,2). Although many pediatric patients with PE are asymptomatic, it can incur impaired cardiopulmonary function and body image (2).

In total, the Nuss procedure has been performed over 50,000 times to date and has undergone many modifications (5-7). Multiple bars can be used for patients with more severe deformities, such as those with Marfan syndrome (5-7). The most lethal complications remain injury to the heart or great vessels during the bar placement (5-7). Several case reports detail the experiences of cardiac arrests during the Nuss procedure (6-8). Cujiño-Álvarez et al. (6) presented a 16-year-old boy with Eagle-Barrett syndrome who developed ventricular fibrillation (VF) following the bar placement and shortly before fixation requiring chest compressions and 3 defibrillations. Although defibrillator pads were placed anterior-laterally during the episode, the authors discussed anterior-posterior placement for future consideration (6). Zou et al. (7) presented an 18-year-old boy with PE who developed recurrent VF during bar rotation, which also required defibrillation. Despite unclear pad placement during this episode, they likewise discussed anterior-posterior placement for future consideration (7). Finally, Kim and Jeong (8) presented a 17-year-old boy with PE who developed VF upon sternal elevation without cardiac injury and ultimately required cardioversion, without discussion on the pad placement.

Collectively, the cases highlight that there are unique considerations and challenges for performing cardiopulmonary resuscitation-related procedures for these patients, as well as an absence of specific guidelines (6). Reflected by our own clinical experience, cardioversion for pediatric patients with the Nuss bar is not familiar to pediatricians or emergency physicians, given its rare occurrence. Generally, the pad placement has been recommended anterior-posterior, in order to facilitate the electrical current passing through the myocardium. These recommendations, however, appear predicated upon theoretical considerations rather than standalone studies (6,7). In addition, there is a hypothetical risk of conversion from electrical to thermal energy when the current passes through the metal bar. We are not aware of any specific studies on this hypothesis. However, the pad placement may not be clearly associated with tissue injury, given the literature regarding patients successfully undergoing electroconvulsive therapy with retained intracranial metal objects or cardioversion with implantable electronic devices (9,10).

There is a scarcity of evidence strongly linking the Nuss bar per se to arrhythmias in patients fully recovered from the Nuss procedure. Guidelines from relevant associations emphasize foremost the role of underlying cardiac risk factors and perioperative stress during a noncardiac surgery (11). There is some speculation that the bar might compromise the internal mammary arterial perfusion over time, in turn leading to arrhythmogenic effects, but this is unclear (12). Another case report theorized that a 23-year-old woman’s late manifestation of cardiac tamponade was caused by repetitive local irritation of the pericardium from the bar (13). Our patient could have had these subclinical risks, but already had several known risk factors for AF, such as Marfan syndrome, pneumonia, and even PE per se (14-16). These risk factors seem more likely related to the development of the arrhythmia for our patient who, irrespective of the underlying cause, still required a cardioversion during an uncommon presentation.

Myocarditis should be considered as a differential diagnosis in pediatric cases of viral-like symptoms and new tachycardia. In a pediatric study, low-voltage ECG findings, new gallop murmur, cardiomegaly, and pulmonary edema were much more common findings than new-onset arrhythmias (17). In another pediatric study, all patients with myocarditis exhibited high troponin concentrations, typically by the time of hospitalization, and ECG changes such as premature ventricular contraction, which were more common than sustained atrial tachycardia (18). Despite the variable presentations of myocarditis, our patient was unlikely to have it given these literature findings.

Our case also highlights the inherent challenges of differentiating the regularity of rapid heart rhythms. Formal evidence-based recommendations are variable on the rate versus rhythm control of such rhythms in the acute care setting (19). An additional challenge is that abnormal ECGs, such as abnormal P wave morphology, can occur in PE, even after procedural repair (20). Accurate identification of arrhythmias can be difficult but critical. In particular, tachyarrhythmia caused by Wolff-Parkinson-White syndrome or another irregular wide-complex tachycardia may mimic SVT, but administering adenosine could result in life-threatening hemodynamic instability.

In conclusion, our case report shows a rare case of a patient with Nuss bars requiring cardioversion unprovoked by the procedural window, representing a unique consideration for cardioversion in such patients. Our experience may strengthen the recommendation for anterior-posterior placement of pads to avoid the bar location to the extent possible (3,7,10).