Case analysis of tachycardia-induced cardiomyopathy secondary to persistent tachycardia in children

Background

Tachycardia-induced cardiomyopathy (TIC) resulting from incessant tachycardia in children is a specific subtype of cardiomyopathy caused by persistent or frequent episodes of tachyarrhythmia. ¹ Its clinical manifestations mainly include cardiac enlargement, heart failure, and impaired cardiac function. In the pediatric population, the tachyarrhythmias most commonly associated with the development of TIC are persistent or incessant supraventricular tachycardias, with major etiologies including incessant or chronic atrial tachycardia, persistent atrioventricular reentrant tachycardia, and chronic atrial flutter. ² Although less common, incessant ventricular tachycardia can also lead to TIC. Rapid pacing induces morphological and ultrastructural changes in cardiomyocytes, which play a key role in the pathogenesis of TIC. In addition, accelerated heart rates contribute to biochemical, metabolic, and neuroendocrine abnormalities that further exacerbate the condition. Notably, TIC in children is a reversible cardiomyopathy when identified and treated early, making timely diagnosis and standardized management particularly important in clinical practice. ³

Case presentation

A young male child was admitted to the Department of Pediatrics, Gansu Provincial People's Hospital, with intermittent dyspnea and palpitations for 1 year, which had worsened over the past 4 days. Prior to admission, the patient had experienced intermittent dyspnea and discomfort without obvious triggers for more than 1 year; each episode lasted several minutes and resolved spontaneously. The patient had a normal body temperature and no precordial discomfort. During the 4 days before admission, the aforementioned symptoms occurred more frequently, with worsening dyspnea but no pallor, edema, cyanosis, or other accompanying symptoms. To undergo further evaluation and treatment, the patient was admitted to Gansu Provincial People's Hospital (Lanzhou, Gansu Province) in January 2023. Written informed consent for treatment was obtained from the patient's guardian before the initiation of all therapeutic interventions. Written informed consent for publication of this case report was also obtained from the patient's legal guardian, and all patient-specific details were de-identified to protect anonymity.

Electrocardiography (ECG) revealed an abnormal rhythm with a heart rate of 230 beats/min; a regular rhythm; a QRS complex duration of 84 ms; upright P waves in lead V1; possibly upright P waves in lead aVL; inverted P waves in leads II, III, and aVF; and an RP interval longer than the PR interval (Figure 1). The patient had no history of cardiovascular disease. On admission, his blood pressure was 92/60 mmHg, height was 132 cm, and weight was 36 kg. Cardiac percussion revealed an enlarged cardiac boundary, and no significant pathological murmurs were auscultated over the valve areas. The preliminary diagnoses were as follows: (a) paroxysmal atrial tachycardia and (b) TIC. Laboratory examinations, including NT-proBNP, routine blood tests, C-reactive protein, rheumatoid factor, liver and renal function tests, myocardial enzyme profile, troponin T, blood glucose, electrolytes, and thyroid function tests, were all within normal ranges. Echocardiography showed a left ventricular end-diastolic diameter of 64 mm, indicating marked left ventricular dilation with a z-score greater than +6.0 compared with normative data adjusted for age, height, and body surface area, severely reduced left ventricular systolic function, and an ejection fraction (EF) of 16%. Cardiac magnetic resonance imaging demonstrated markedly impaired left ventricular systolic motion, with a left ventricular EF of approximately 14.8%, an end-diastolic volume of 147.7 mL, an end-systolic volume of 125.9 mL, and no evidence of myocardial fibrosis. After admission, the patient received medications to improve cardiac function, including furosemide, spironolactone, captopril, and metoprolol, as well as antiarrhythmic therapy (metoprolol and propafenone) for approximately 10 days. However, the therapeutic response was unsatisfactory. During treatment, close monitoring of the patient's heart rhythm, cardiac function, and clinical symptoms was performed, but no obvious improvement was observed. With the family's consent, the patient subsequently underwent an electrophysiological study and radiofrequency ablation.

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Figure 1.

Preoperative surface electrocardiogram (ECG) of a patient with preoperative tachycardia with an upright P-wave in lead V1, a suspected upright P-wave in lead aVL, inverted P waves in leads II, III, and aVF, and an RP interval longer than the PR interval, suggesting right atrial tachycardia.

The procedure was performed under the guidance of a three-dimensional electroanatomical mapping system (CARTO). Catheters were inserted through the right femoral vein and positioned in the high right atrium, His bundle region, and right ventricle, while an additional catheter was introduced through the left subclavian vein and positioned in the coronary sinus. Preprocedural surface ECG showed upright P waves in lead V1, possibly upright P waves in lead aVL, inverted P waves in leads II, III, and aVF, and an RP  interval longer than the PR interval (Figure 1), initially suggesting right atrial tachycardia. Using a Pentaray catheter, a right atrial model was constructed during atrial tachycardia, and high-density activation mapping identified an early activation site 36 ms ahead of the reference signal (coronary sinus electrodes CS7–8) in the high interatrial septum (Figure 2). However, radiofrequency ablation at this site failed to terminate the atrial tachycardia.

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Figure 2.

Right atrial model constructed using a Pentaray catheter during tachycardia with high-precision mapping, indicating a high-septal early activation point with a 36 ms advance relative to the CS7–8 coronary sinus electrodes.

Following successful transseptal puncture, a left atrial model was constructed using the Pentaray catheter, and high-density activation mapping revealed focal atrial tachycardia with the earliest activation point occurring 61 ms before the reference signal (coronary sinus electrodes CS7–8) at the posterior margin of the right upper pulmonary vein (Figure 3). Radiofrequency ablation was performed using a D-type saline-irrigated ablation catheter (NAV-STAR Thermo-Cool, Biosense-Webster, USA) in power-control mode (35 W), with a saline flow rate of 17 mL/min at the target site. The tachycardia terminated and converted to sinus rhythm during ablation. Ablation was then continued at the target site and surrounding area for approximately 200 s (Figure 4). Repeat atrial stimulation and intravenous isoproterenol infusion failed to induce tachycardia. The patient's condition improved after the procedure, and he was discharged.

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Figure 3.

Left atrial model constructed using a Pentaray catheter with high-density activation mapping, demonstrating focal atrial tachycardia with the earliest activation point occurring 61 ms before the reference signal at the posterior margin of the right upper pulmonary vein (referenced to the CS7–8 coronary sinus electrodes).

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Figure 4.

Catheter power-control mode (35 W) with a saline flow rate of 17 mL/min during ablation, ablation performed at the target site. Tachycardia terminated and converted to sinus rhythm during ablation. Ablation was continued at the target site and surrounding area for approximately 200 s.

During the 8-month postoperative follow-up period, the patient continued treatment with spironolactone and sacubitril/valsartan to improve cardiac function. Follow-up electrocardiography (Figure 5) showed no recurrence of tachycardia, while echocardiography demonstrated marked improvement in left ventricular enlargement compared with the preoperative state and normalization of left ventricular systolic function (EF = 59%). The reporting of this study conforms to the Case Report (CARE) guidelines. ⁴

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Figure 5.

Sinus rhythm, a normal electrical axis, normal electrocardiogram (ECG).

Discussion

Various types of tachyarrhythmias can cause TIC, and atrial tachycardia is the most common arrhythmia associated with pediatric TIC, followed by sustained junctional tachycardia, ventricular tachycardia, and atrioventricular reentrant tachycardia. ¹ In this case, the patient had atrial tachycardia, which has a higher incidence in pediatric patients than in adults. Early radiofrequency ablation is recommended for children with symptomatic atrial tachycardia who respond poorly to medical therapy. ² The reported immediate success rate of radiofrequency ablation in pediatric patients with atrial tachycardia ranges from 89% to 100%.

Sustained tachycardia causes systolic dysfunction through multiple cellular and biochemical pathways, including abnormal calcium handling, mitochondrial dysfunction, oxidative stress, and neurohormonal activation. These changes lead to myocyte remodeling, impaired excitation–contraction coupling, and reduced myocardial contractility. Specifically, NAD-Sirtuins-mediated acetylation of SERCA2a has been identified as a key molecular mechanism underlying tachycardia-induced contractile dysfunction, whereas normalization of NAD + balance facilitates functional recovery. ³ Following elimination of the arrhythmia, progressive reversal of cellular injury, restoration of calcium homeostasis, and attenuation of neurohormonal stimulation allow gradual normalization of ventricular size and systolic function. ³

In this case, the patient had atrial tachycardia with a tachycardia burden exceeding 70% based on continuous electrocardiographic monitoring during hospitalization. The diagnostic criteria for pediatric TIC caused by incessant tachycardia are similar to those used in adults and include the following: (a) clinical manifestations of heart failure; (b) a history and evidence of incessant tachycardia over a prolonged period; (c) electrocardiographic and Holter monitoring findings demonstrating incessant tachycardia, cardiac enlargement, and impaired cardiac function; (d) exclusion of heart failure and tachyarrhythmias caused by congenital heart disease or other structural heart diseases; and (e) significant improvement in heart failure, cardiac enlargement, and cardiac dysfunction after control of the tachyarrhythmia. The patient had recurrent symptomatic atrial tachycardia, a body weight ≥15 kg, and ineffective medical therapy, thereby meeting the indications for radiofrequency ablation in pediatric patients with tachyarrhythmias according to the “Pediatric Arrhythmia Catheter Ablation Expert Consensus.”^5,6 After admission, the patient received medications to improve cardiac function and antiarrhythmic therapy; however, the response was unsatisfactory. With the family's consent, the patient underwent an electrophysiological study and radiofrequency ablation under CARTO guidance.

Right atrial tachycardia is more common than left atrial tachycardia. Common ablation sites for right atrial tachycardia include the high interatrial septum, crista terminalis, tricuspid annulus, coronary sinus ostium, superior vena cava, and right atrial appendage.^6,7 Common ablation sites for left atrial tachycardia include the pulmonary veins, interatrial septum, and left atrial appendage. ⁸ Based on the surface ECG findings, the preliminary diagnosis in this patient was right atrial tachycardia, and the initial ablation target was the high interatrial septum. However, radiofrequency ablation at this site was unsuccessful. Subsequently, transseptal puncture and repeat high-density activation mapping identified the target site at the posterior margin of the right upper pulmonary vein, where radiofrequency ablation successfully terminated the tachycardia. Because of the small P-wave amplitude and the influence of factors such as muscle tremor, respiration-induced baseline instability, variability in left atrial anatomy, and electrical connections between the left and right atria, the surface ECG alone is insufficient for accurately determining the origin of atrial tachycardia. P-wave morphology in atrial tachycardia originating near the right upper pulmonary vein often overlaps with that arising from the superior vena cava, crista terminalis, and other sites, making differentiation difficult.^9,10

Previous pediatric studies have shown that TIC is reversible following successful elimination of incessant atrial tachycardia. In children with drug-refractory atrial tachycardia, early radiofrequency ablation guided by three-dimensional mapping is associated with high success rates and significant improvement in cardiac function. ¹¹ Notably, surface ECG P-wave morphology may be misleading when localizing focal atrial tachycardia, and precise electroanatomical mapping is essential for identifying origins such as the pulmonary veins. ⁹ Similar to the present case, pediatric patients with pulmonary vein-originated atrial tachycardia often present with severe left ventricular dilation and dysfunction, both of which may completely reverse after successful ablation. ⁸

Previous studies have described the clinical features and management of TIC. Compared with existing reports, this case highlights a poor response to conventional medical therapy, thereby broadening the recognized clinical spectrum of this condition and providing additional insights for clinical practice. However, this case report has several limitations. As a single-case report, its findings have limited generalizability. In addition, the relatively short follow-up period restricts assessment of the long-term prognosis.

Conclusions

The successful management of this patient was attributed to identification of the appropriate ablation target under CARTO system guidance and timely radiofrequency ablation. During the 8-month follow-up period, there was no recurrence of atrial tachycardia, and both cardiac size and function normalized. Although this is a single-case report, the findings support the concept that early diagnosis and effective intervention may contribute to favorable outcomes in pediatric patients with TIC. In children presenting with tachyarrhythmia, cardiac enlargement, and heart failure, the possibility of TIC should be considered. Early intervention, such as radiofrequency ablation, may be warranted when medical therapy fails to achieve adequate control.