Abstract
Background
Cardiac masses are rare in pediatric patients, and multimodality imaging is crucial for diagnosis. These masses can present with different arrhythmias, adding challenges to their management.
Case Summary
We report an unusual presentation of cardiac masses in an infant with aborted sudden cardiac arrest, ST-segment elevation electrocardiography, and recurrent supraventricular tachycardia. The masses were distant from the sinoatrial node, yet we detected severe sinus node dysfunction requiring epicardial pacemaker implantation. Although the imaging suggested malignant features, tissue biopsy confirmed the diagnosis of benign rhabdomyoma. No other manifestations of tuberous sclerosis were detected.
Discussion
Several cases of this tumor were reported to present with arrhythmias. The management of these cases requires a multidisciplinary approach individualized for each patient.
Take-Home Messages
Infants with cardiac rhabdomyoma can experience severe sinus node dysfunction, irrespective of mass location, requiring pacing. Despite current advances in cardiac imaging, tissue biopsy is still the gold standard for accurate diagnosis.
Key words: bradycardia, cardiac pacemaker, imaging, pediatric surgery
Graphical Abstract
History of Presentation
A 3-month-old male infant was referred to the outpatient clinic with a history of sudden cardiac arrest and multiple cardiac masses for further investigation. One month earlier, the patient was resuscitated from undocumented cardiac arrest after an episode of cyanosis. During the admission, he developed episodes of supraventricular tachycardia (SVT) for which he was prescribed propranolol.
With a weight of 5.2 kg, he had unremarkable clinical examination results. Electrocardiography (ECG) showed marked ST-segment elevation in inferior leads with reciprocal changes. Short PR intervals and delta waves were noted in some leads as well (Figure 1).
Figure 1.
ECG at Presentation
12-lead ECG showing marked ST-segment elevation in inferior leads with reciprocal changes. Initial differential diagnosis included ischemia by vascular compression, pericarditis, myocardial compression, or mass superimposed electrical activity. A pre-excitation pattern is noted in some leads as well (A), which could be the substrate for supraventricular tachycardia. This pattern was intermittent as noted in serial ECG (B). ECG = electrocardiography.
Echocardiography revealed 2 large left ventricular masses; one was located at the cardiac apex protruding into the left ventricular cavity, and the other one was located posteriorly with extension into pericardial space and reaching the atrioventricular (AV) groove (Figure 2). Mild pericardial effusion was noted as well. Otherwise, the study showed normal biventricular size and function with normal valvular structure and flow.
Figure 2.
Initial Echocardiography
Echocardiography images in apical 4-chamber (A), subcostal (B), and parasternal long-axis (C) views with some tilting. Two large left ventricular masses can be seen. One is intracavitary located apically and the other extends into the pericardial space posteriorly. Extension toward the left atrioventricular groove is seen in A and B.
Past Medical History
The infant was a full term born from nonconsanguineous marriage with an uneventful normal delivery. He had 2 siblings with no relevant family history.
Differential Diagnosis
Possible initial explanation of the unusual presentation included coronary artery compromise by the mass, active pericarditis, or ventricular muscle invasion, causing tissue damage and ventricular arrhythmia.
The presented cardiac masses could be primary (benign or malignant), such as rhabdomyoma, fibroma, teratoma, angiosarcoma, or lymphoma, or secondary (metastatic) from a distant source.
The event of aborted arrest could have cardiac causes such as arrhythmias, ischemia, or low cardiac output. It could also have noncardiac causes such as cerebral embolism by the mass or any associated metabolic disorders.
Investigations
Serial ECG did not show significant dynamicity of the ST-segment changes, yet the pre-excitation pattern was intermittent (Figure 1).
There was an elevated high-sensitivity cardiac troponin level: initial test was 5-fold above the upper reference limit, falling to 3.6-fold after 5 days.
Holter monitoring for 24 hours showed multiple pauses, with the longest being 6.5 seconds (Figure 3). These were evident when repeating the Holter while withholding propranolol. No episodes of tachyarrhythmias were recorded.
Figure 3.
Holter Monitoring
Sequential images from 24-hour Holter monitoring of the infant showing one of the recorded bradycardia events. Initially, there was gradual slowing of the heart rate, followed by long sinus arrest. Sporadic escape junctional beats can be noted until gradually regaining sinus activity and normal heart rate. Marked ST-segment elevation and pre-excitation pattern can be seen as well.
Cardiac computed tomography with contrast was performed for better visualization of the masses (Figure 4) and their vascularity. A large isodense soft tissue mass was seen abutting the inferior and inferolateral walls of the left ventricle with no clear line of cleavage. It measured 1.3 × 3 × 3.7 cm. No calcification or degeneration was seen. Another smaller intracavitary soft tissue mass lesion was noted at the apex measuring 1 × 1 × 1.3 cm with similar findings. All coronary arteries had normal origin and courses with no kink or stenosis. The epicardial mass received vascularity from the right coronary and left circumflex arteries. Multiple rib fractures were seen with unremarkable lung examination results.
Figure 4.
Cardiac Computed Tomography With Contrast
Cardiac computed tomography with contrast was performed under sedation. The 2 isodense masses can be seen in the short-axis (A) and 2-chamber (B) views. The test also allowed characterization of mass vascularity (C) and exclusion of coronary compromise by the masses especially in the presence of the inferior ST-segment elevation in electrocardiography. The green arrows point to the left circumflex artery and its branches supplying the epicardial mass.
Cardiac magnetic resonance (CMR) was performed to characterize the mass in different sequences (Figure 5). The mass features in CMR (Table 1) along with the vascularity pattern outweighed the possibility of malignancy. Head and abdomen cuts were taken during examination rendering normal brain and kidney structure with no masses.
Figure 5.
Cardiac Magnetic Resonance
Cardiac magnetic resonance was performed under sedation to characterize the masses. The epicardial mass (red arrows) can be seen in the short-axis view in different sequences: T1 (A), T2 (B), perfusion (C), and late gadolinium enhancement (D). Note the heterogeneous enhancement of the mass in D. Mass characteristics suggested malignant features, which were disproven by the biopsy result later on.
Table 1.
Features of Tissue Characterization in Different Sequences of Cardiac Magnetic Resonance
| Sequence | Signal |
|---|---|
| Cine | Isointense to low intense |
| T1 | Isointense |
| T2 | Iso- to low-intense core with hyperintense line of cleavage between the epicardial mass and the myocardium |
| STIR | Iso- to low-intense core with still noted hyperintense line of cleavage between the epicardial mass and the myocardium |
| T1 FS | Isointense |
| Perfusion | Diffuse enhancement |
| T1 C+ | Heterogeneous mostly peripheral enhancement |
| LGE | Heterogeneous mostly peripheral enhancement |
C+ = postcontrast; FS = fat suppression; LGE = late gadolinium enhancement; STIR = short τ inversion recovery.
Management
A joint cardiac committee was held to discuss the available data among pediatric, cardiothoracic surgery, and electrophysiology specialties. The committee decided to implant a single-chamber epicardial pacemaker as backup pacing and perform a biopsy during the surgery. The procedure was performed through median sternotomy incision, and a tissue biopsy was taken from the epicardial extension of the mass. The pacemaker was then programmed to the VVI mode at a rate of 80 beats/min, and propranolol was reintroduced.
Outcome and Follow-Up
The biopsy result described tumor tissue formed of large vacuolated spider cells with fibrous stroma containing blood vessels and no evidence of malignancy. These findings confirmed the diagnosis of benign rhabdomyoma.
Two months after the surgery, the infant was doing well with no new episodes of syncope or cyanosis. The ECG was static, and the echocardiographic measurements of the masses were the same with no pericardial effusion.
Holter monitoring showed episodes of a sudden drop in the heart rate, followed by ventricular pacing with no visible P waves (Figure 6), suggesting sinus pauses with backup pacing.
Figure 6.
Postoperative Holter
Holter monitoring was performed after 2 months of pacemaker implantation, which was programmed to the VVI mode at 80 beats/min. The strip shows one of the recorded bradycardia events. A drop in the heart rate is noted with disappearance of atrial activity, followed by ventricular pacing marked by the initial pacing spikes. This showed how protective was the pacemaker for the infant.
The infant continued on propranolol for prevention of further SVT episodes.
Discussion
Cardiac tumors are rare in the pediatric age group with an incidence of 0.01% to 0.32%. Clinical presentation is variable depending on the degree of valvular obstruction, the presence of pericardial effusion, and the occurrence of embolic events. Presentation with sudden cardiac arrest or arrhythmia is not uncommon, and decision-making in these cases is quite challenging.1
Cardiac rhabdomyoma is the most common cardiac tumor in pediatric population. There is a well-established association between cardiac rhabdomyoma and tuberous sclerosis especially in patients with multiple masses. It is estimated that 70% to 90% of children with this tumor have tuberous sclerosis.2 Definite diagnosis of tuberous sclerosis requires a combination of major and minor criteria from different body organs such as the heart, brain, lungs, eyes, and skin. Continuous surveillance of these systems is critical in suspected subjects for early diagnosis and treatment.3 In our case, no other manifestations of tuberous sclerosis were evident by imaging, yet further follow-up was planned as a latent presentation usually occurs.
Multimodality imaging is essential in establishing the diagnosis of cardiac rhabdomyoma in addition to detecting complications such as valvular obstruction or coronary occlusion. In our case, accurate diagnosis was challenging owing to the atypical imaging characteristics of the mass. In a multicenter study of pediatric patients with cardiac masses, rhabdomyoma exhibited relatively low diagnostic accuracy with CMR; 69% had correct single diagnosis.4 Prenatal early diagnosis is feasible with fetal echocardiography, which could have been helpful in our case for early follow-up and management.3
The presenting ECG in our case was very unusual with the marked ST-segment elevation in inferior leads with reciprocal changes. Coronary artery compromise by the mass was excluded by cardiac computed tomography. Pericarditis was also unlikely due to the fixed pattern of these changes. ST-segment elevation was previously reported in cases with cardiac rhabdomyoma. Proposed explanations apart from coronary obstruction and pericarditis included myocyte compression, myocardial infiltration, and superimposed electrical activity of the mass itself.5
There is a reported association between cardiac rhabdomyoma and arrhythmias, which vary according to tumor size and location. Reported arrhythmias included SVT, ventricular tachycardia, premature ventricular complexes, complete heart block, and sinus node dysfunction.6
Ventricular pre-excitation was reported in many cases with rhabdomyoma predisposing to AV reentrant tachycardia and life-threatening atrial fibrillation. Regression or resection of these tumors was associated with disappearance of pre-excitation pattern and cessation of tachyarrhythmia, which support that the tumor itself acted as an accessory pathway.7 In our case, which exhibited intermittent pre-excitation and recurrent SVT, this hypothesis is supported by the location of the mass reaching the AV groove (Figure 2). Ablation of the accessory pathway can be considered when the infant reaches appropriate weight, yet the pre-excitation could disappear if regression of the tumor occurred.
Regression of the tumor is the characteristic feature of the natural history of cardiac rhabdomyoma. Surgical resection is reserved for complicated cases with hemodynamic compromise in whom resection could be done without harming nearby structures.2 Immunosuppressant drugs, such as everolimus and sirolimus, were used in limited reports to accelerate tumor regression. These drugs are currently used in complicated cases with high procedural risk owing to the expected adverse effects.8 In our case, resection of the masses during the procedure was considered high risk owing to their size, location, and the suspected malignant nature at the time of decision-making. Further follow-up of the infant was planned to monitor tumor regression and detect complications.
Epicardial pacing was reported previously in a neonate with a small ventricular rhabdomyoma and tuberous sclerosis in whom Holter monitoring recorded a 6.4-second pause. The patient experienced a prolonged episode of unresponsiveness associated with cyanosis. Degenerative and infiltrative changes were suggested as a cause of sinus node disease.9 In our case, pacing was justified by the recurrent long pauses with the history of aborted sudden cardiac arrest. Pacing also enabled reintroduction of propranolol to prevent SVT episodes. Follow-up with Holter recorded recurrent sinus pauses and ventricular pacing, proving the benefit of pacing (Figure 6). In addition, the surgery was a good opportunity to get tissue biopsy to reach the right diagnosis.
Interestingly, a case with a quite similar presentation was reported earlier for a newborn with a giant cardiac rhabdomyoma over the posterior wall of the left ventricle reaching the AV groove. The initial presentation was cyanosis and bradycardia with subsequent aborted cardiac arrest on ventricular fibrillation. Recurrent SVT episodes occurred afterward requiring electrical cardioversion and antiarrhythmic drugs. A different approach was adopted by performing partial resection of the mass. The procedure was considered successful with no recurrence of arrhythmias afterward.10
The occurrence of sinus node dysfunction in such cases where the cardiac rhabdomyoma was distant from the sinoatrial node could possibly be linked to affection of autonomic ganglia by the mass. In our case, one mass had an epicardial extension toward the cardiac crux, which is a known site for left dorsal autonomic plexus.
Conclusions
We report an unusual presentation of cardiac masses in an infant with aborted sudden cardiac arrest, ST-segment elevation on ECG, and recurrent SVT. The masses were distant from the sinoatrial node, yet we detected severe sinus node dysfunction requiring epicardial pacemaker implantation. Although imaging suggested malignant features, tissue biopsy confirmed the diagnosis of benign rhabdomyoma. No other manifestations of tuberous sclerosis were detected.
Take-Home Messages
-
•
Infants with cardiac rhabdomyoma can experience severe sinus node dysfunction, irrespective of the mass location, requiring pacing.
-
•
Despite current advances in cardiac imaging, tissue biopsy is still the gold standard for accurate diagnosis.
Visual Summary.
Timeline of Events
| Age (mo) | Events |
|---|---|
| 2 | Aborted cardiac arrest and recurrent supraventricular tachycardia episodes Discovery of the giant cardiac masses Electrocardiography showing inferior ST-segment elevation and pre-excitation pattern Started propranolol |
| 3 | Multimodality imaging suggesting malignancy Holter monitoring showing severe sinus node dysfunction |
| 3.5 | Single-chamber pacemaker implantation and tissue biopsy from the mass |
| 5.5 | Biopsy confirmed the diagnosis of benign rhabdomyoma Holter showed recurrent sudden bradycardia and backup pacing |
Funding Support and Author Disclosures
The authors have reported that they have no relationships relevant to the contents of this paper to disclose.
Acknowledgments
The authors would like to honor all staff of the Aswan Heart Center in all departments who work with dedication for their patients.
Footnotes
The authors attest they are in compliance with human studies committees and animal welfare regulations of the authors’ institutions and Food and Drug Administration guidelines, including patient consent where appropriate. For more information, visit the Author Center.
References
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