Case September 2026 - Multiple cardiac rhabdomyomas and neonatal hypotension

Case description

Prenatal and early postnatal findings

A term infant was admitted for cardiac monitoring and evaluation for suspected tuberous sclerosis complex (TSC) following antenatal detection of multiple cardiac masses. Third-trimester fetal echocardiography showed cardiomegaly and non-obstructive masses in the right atrium and both ventricles, consistent with rhabdomyomas. Ventricular systolic function and cardiac rhythm were normal. After brief respiratory support at birth, the infant initially stabilised in room air. Early postnatal cardiology imaging confirmed extensive rhabdomyomas, including a large left ventricular (LV) apical mass and masses involving both mitral papillary muscles. Some mitral leaflet restriction and extension towards the LV outflow tract were described, but Doppler showed no ventricular inflow or outflow obstruction. There was mild mitral and tricuspid regurgitation, a small fenestrated secundum atrial septal defect with left-to-right flow, and a tiny restrictive left to right patent ductus arteriosus (closing pattern). Right ventricular (RV) systolic function was grossly normal; LV systolic function was mildly reduced with regional dyssynergy.

Hypotension during seizure treatment

During the first postnatal week, refractory seizures required several antiseizure medications, including a continuous midazolam infusion. Brain MRI showed features consistent with TSC. Hypotension developed in the setting of this treatment, prompting dopamine support (for vasopressor effect) and a targeted neonatal echocardiography (TNE) consultation for functional assessment and evaluation of cardiac filling. At the time of TNE, dopamine was running at 7.5 micrograms/kg/min and midazolam at 7 micrograms/kg/min. Blood pressure was 63/33 mmHg on support, lactate was 1.1 mmol/L, and urine output was approximately 3 mL/kg/h. The infant was receiving CPAP with a low supplemental oxygen requirement.

TNE findings and clinical course

Despite the extensive tumour burden, the TNE study showed preserved biventricular systolic function, with an LV ejection fraction of 56%, fractional shortening of 32%, and tricuspid annular plane systolic excursion of 9.8 mm. LV output was 283 mL/kg/min. No LV or RV inflow or outflow obstruction was identified, and LV filling appeared similar to the preceding cardiology study. The atrial shunt remained left-to-right, and the ductus was closed. The clinical impression favoured medication-associated peripheral vasodilation rather than current systolic pump failure or mechanical obstruction. The TNE team advised avoiding further dopamine escalation that might compromise filling through tachycardia, and considering norepinephrine if hypotension persisted. Vasoactive support was subsequently transitioned to norepinephrine, dopamine was stopped, and blood pressure and perfusion improved. Line position was adjusted during TNE because was intra-cardiac (see views below for final position at the IVC-RA junction).

Discussion

Cardiac rhabdomyomas are benign tumours strongly associated with TSC, particularly when multiple. Many regress spontaneously, but their location can produce valve dysfunction, inflow or outflow obstruction, ventricular dysfunction, or arrhythmia. The severity of the images therefore does not, by itself, define the mechanism of hypotension. [1]

In this infant, papillary muscle and apical involvement raised concern for limited ventricular filling reserve even without a measurable obstruction. Preserved ejection fraction does not establish normal ventricular compliance. The combination of cardiac masses, seizures and characteristic cerebral imaging also warrants coordinated cardiac, neurological, renal and genetic evaluation for TSC. [2]

Blood pressure reflects both cardiac output and vascular resistance. TNE helps distinguish impaired contraction, altered filling, shunt effects and obstruction, but its findings must be integrated with perfusion, urine output and lactate. Systolic indices are load dependent, and this examination was performed during dopamine treatment; it does not describe unsupported function or directly measure systemic vascular resistance. [3] Here, unobstructed flow pathways, preserved systolic function and reassuring perfusion markers on support made vasodilation a plausible working explanation. Midazolam can be associated with hypotension in critically ill neonates. [4] However, the temporal relationship does not establish midazolam as the sole cause, particularly with concurrent antiseizure medications. Volume status, infection, rhythm and evolving cardiac disease remain relevant if instability persists.

The case-specific rationale was to support vascular tone while limiting unnecessary chronotropic stimulation. In ventricles substantially occupied by masses, a faster heart rate may shorten diastolic filling time and reduce filling reserve. This was a physiological concern, not a demonstration of new obstruction or measured diastolic dysfunction. Norepinephrine provides alpha-adrenergic vasoconstriction and also has beta-adrenergic cardiac effects; it is not a purely vascular drug. Increased afterload can reduce output, so a higher blood pressure must be accompanied by adequate tissue perfusion. [5] A small observational study in term neonates with refractory septic shock reported improved pressure and perfusion markers after norepinephrine, but this does not establish superiority for medication-associated hypotension or for infants with rhabdomyomas. [6] Treatment therefore requires individual reassessment, including reassessments when the clinical course changes.

Teaching points

• Define the functional consequences of each mass, not only its size.

• Separate earlier LV dysfunction from the findings during the hypotensive episode.

• Normal systolic function does not exclude limited filling reserve.

• Match vasoactive support to the suspected physiology and reassess pressure together with perfusion.

Targeted Neonatal Echocardiography

Fetal Echocardiography

Bibliography

1. Hinton RB, Prakash A, Romp RL, Krueger DA, Knilans TK. Cardiovascular manifestations of tuberous sclerosis complex. J Am Heart Assoc. 2014;3:e001493. doi:10.1161/JAHA.114.001493

2. Northrup H, Aronow ME, Bebin EM, et al. Updated International Tuberous Sclerosis Complex Diagnostic Criteria and Surveillance and Management Recommendations. Pediatr Neurol. 2021;123:50–66. doi:10.1016/j.pediatrneurol.2021.07.011

3. McNamara PJ, Jain A, El-Khuffash A, et al. Guidelines and Recommendations for Targeted Neonatal Echocardiography and Cardiac Point-of-Care Ultrasound in the Neonatal Intensive Care Unit. J Am Soc Echocardiogr. 2024;37:171–215. doi:10.1016/j.echo.2023.11.016

4. DailyMed. Midazolam Injection, USP. Prescribing information. Neonatal precautions and continuous infusion section. Midazolam prescribing information

5. DailyMed. Norepinephrine Bitartrate Injection. Prescribing information. Clinical pharmacology, sections 12.1 and 12.2. Norepinephrine prescribing information

6. Tourneux P, Rakza T, Abazine A, Krim G, Storme L. Noradrenaline for management of septic shock refractory to fluid loading and dopamine or dobutamine in full-term newborn infants. Acta Paediatr. 2008;97:177–180. doi:10.1111/j.1651-2227.2007.00601.x