In the delicate and rapidly evolving field of neonatal care, understanding the cardiovascular landscape of periviable neonates—those born at the very edge of viability between 22 and 24 weeks gestation—remains one of the most daunting clinical challenges. The complexities inherent in assessing and managing the heart function and circulatory stability of these tiniest patients demand a multifaceted and highly nuanced approach. Cardiovascular assessment in this fragile group is riddled with difficulties: measurements are often imprecise, interpretations ambiguous, and the normative values for many diagnostic tools are sorely lacking. Such challenges place clinicians in a constant race against time, where early detection and vigilant monitoring are essential to navigate the precarious transition to extrauterine life.
Hypotension, or low blood pressure, is a frequent and significant concern in these extremely preterm neonates, reflecting the immense physiological stress of adapting to life outside the womb. However, hypotension in this context should perhaps not be treated as an isolated diagnosis but rather as a complex sign of underlying pathophysiology. This perspective is critical because numerous complicating factors—such as compromised respiratory status requiring mechanical ventilation, the occurrence of pneumothorax, septic episodes, acute kidney failure, temperature regulation disturbances, and metabolic imbalances—can all influence blood pressure readings and the neonate’s overall circulatory state. Therefore, treating hypotension demands an integrated understanding of the whole clinical picture rather than a sole reliance on numbers.
These cardiovascular phenotypes in periviable neonates are highly dynamic, capable of changing swiftly in response to therapeutic interventions. This reality underscores the necessity of early follow-up and frequent monitoring of therapeutic responses, or lack thereof. Unfortunately, our current medical technology lacks the capacity for continuous, real-time monitoring that truly captures the fluid nature of neonatal cardiovascular physiology. This shortfall poses a significant obstacle to precision medicine in this vulnerable population, emphasizing the urgent need for advancements in both technology and clinical protocols.
Clinical evaluation remains the cornerstone of bedside assessment, despite its limitations. For these neonates, physical signs such as skin color, muscle tone, and capillary refill time provide valuable, albeit imperfect, insights into cardiovascular stability. A pink hue in an infant’s complexion offers some reassurance, whereas pallor, mottling, or grayness can signal distress. Similarly, urine output is an essential measure of end-organ perfusion but must be interpreted cautiously during the early transitional phase, when renal function is immature and highly variable. These clinical parameters, while indispensable, are far from definitive, particularly in neonates born at the cusp of viability.
Blood pressure measurement, a tradition long entrenched in neonatal care, is increasingly recognized as an insufficient stand-alone marker for hemodynamic assessment in preterm infants. The long-held convention of using mean arterial pressure (MAP) relative to gestational age as a benchmark is now being debated. Not only are these gestational age-based MAP thresholds unvalidated for use at the earliest gestations, but studies have also shown a poor correlation between these measures and actual systemic blood flow. Moreover, a notable physiological dip in blood pressure occurs in these neonates during the first several hours of life, with nadirs typically seen around four to five hours postpartum. This phenomenon implies that critical windows of vulnerability coincide with naturally transient hypotension, complicating decisions about intervention.
A recent pivotal study by Pershad and colleagues shed light on this issue by demonstrating that gestational age-based criteria notably underestimated actual blood pressure levels in neonates born before 25 weeks gestation. These findings challenge clinicians to reassess existing protocols that may prompt premature or unnecessary use of interventions. Importantly, the first three to six hours after birth are when these neonates are most hemodynamically unstable—a period coinciding with the typical onset of antihypotensive therapy. These insights call for a refined approach that better aligns clinical thresholds with physiological realities.
Beyond the mean arterial pressure, both systolic (SBP) and diastolic blood pressures (DBP) independently provide valuable clues to the underlying cardiovascular dynamics. Recognizing the unique insights each measure offers is vital, as SBP and DBP reflect different aspects of cardiac output and vascular resistance. However, interpreting these values is not straightforward and must consider the measurement method (whether invasive or non-invasive) and anatomical site (pre-ductal versus post-ductal). These factors can significantly influence readings and thus must be integrated into clinical decision-making. Additional hemodynamic parameters such as pulsatility index and perfusion index have also been explored, although normative data and clinical validation are still evolving in this population.
Although blood pressure provides quantitative data, the ultimate goal of cardiovascular management in these neonates extends beyond mere numbers to focus on end-organ perfusion. Recent evidence supports this perspective: neonates who were hypotensive based on gestational age criteria but demonstrated robust clinical signs of adequate perfusion had outcomes comparable to normotensive infants. This finding underscores the danger inherent in binary reliance on blood pressure readings without contextualizing them within the broader clinical picture. It advocates for a personalized, physiology-driven approach to care.
Laboratory surrogates of organ perfusion, such as blood gas analysis revealing metabolic and lactic acidosis, offer additional but imperfect windows into the neonate’s cardiovascular status. Elevated lactate levels in the first three hours of life have been correlated with worse outcomes, including increased mortality and neurodevelopmental impairment. Yet, both types of acidosis are frequently encountered in these tiniest patients, complicating their interpretation. Monitoring trends in these markers over time is therefore more informative than isolated readings, providing a dynamic gauge of the neonate’s metabolic trajectory and response to treatment.
Technological advances have introduced promising tools like near-infrared spectroscopy (NIRS) and non-invasive cardiac output monitoring, which hold promise for continuous, minimally invasive hemodynamic evaluation. NIRS, in particular, enables real-time assessment of regional tissue oxygenation and perfusion, which can guide tailored interventions. However, widespread adoption is hampered by the lack of robust normative datasets and validation studies specifically focused on neonates born at or below 24 weeks gestation. Without this foundational information, interpreting these advanced metrics remains challenging and can potentially lead to misinformed clinical judgments.
Echocardiography, especially targeted neonatal echocardiography (TnEcho), has emerged as an invaluable tool in the nuanced assessment of cardiovascular status in periviable neonates. Performed by skilled neonatologists, TnEcho enables comprehensive evaluation of cardiac function, pulmonary vascular resistance, and the presence and impact of shunts, such as those through the patent ductus arteriosus or foramen ovale. This approach moves beyond static measures to reveal mechanistic underpinnings of hemodynamic abnormalities, informing individualized therapeutic strategies.
TnEcho-guided management has been associated with improved outcomes in centers across North America and Japan, reflecting its growing clinical utility. Its ability to identify transitional circulatory physiology early enables clinicians to tailor interventions to specific cardiovascular phenotypes, enhancing precision care. The method allows intermittent yet timely assessments of cardiac output, right ventricular pressures, and systemic flow patterns, bridging the gap between bedside physical examination and invasive monitoring.
Despite its promise, widespread implementation of neonatal targeted echocardiography faces hurdles. It demands significant expertise and training to perform, interpret, and apply findings effectively at the bedside. Furthermore, concerns about potential instability during examination, particularly in the most fragile neonates, have limited its use. However, recent studies, including those involving neonates with congenital diaphragmatic hernia (CDH), have demonstrated that TnEcho can be safely and rapidly performed early in life, bolstering confidence in its feasibility and utility even in critically ill patients.
Looking ahead, the integration of TnEcho into routine cardiovascular assessments of periviable neonates offers a pathway to standardize care, improve early diagnosis, and optimize management strategies. Establishing normative echocardiographic parameters for this population would further enhance its application, providing essential benchmarks for distinguishing pathological states from expected transitional physiology. When combined with continuous monitoring technologies and bedside clinical assessment, TnEcho has the potential to revolutionize cardiovascular care for these smallest patients.
As global neonatal intensive care units incorporate more focused hemodynamic evaluations, the clinical landscape is shifting toward precision medicine tailored to the unique challenges of periviable neonates. This evolution carries profound implications, not only for survival but also for long-term neurodevelopmental outcomes and quality of life. Bridging existing knowledge gaps and refining cardiovascular assessment tools thus represent not mere academic exercises but critical imperatives in the pursuit of more humane, effective neonatal care.
In summary, managing cardiovascular instability in periviable neonates demands a departure from oversimplified, number-driven protocols toward an integrated, physiology-informed approach. Recognizing hypotension as a symptom rather than a diagnosis, appreciating the dynamic nature of neonatal circulation, incorporating multiple assessment modalities, and embracing advanced imaging techniques collectively form the blueprint for the next era of neonatal cardiovascular care. This paradigm shift holds the promise of transforming outcomes for the tiniest hearts entering the world.
Subject of Research: Cardiovascular phenotypes and assessment in periviable neonates (22–24 weeks gestation)
Article Title: Caring for the smallest hearts: cardiovascular phenotypes and assessment in tiny babies
Article References:
Hari Gopal, S., Parmekar, S., Dempsey, E. et al. Caring for the smallest hearts: cardiovascular phenotypes and assessment in tiny babies. Pediatr Res (2026). https://doi.org/10.1038/s41390-026-05164-4
Image Credits: AI Generated
DOI: 03 June 2026
