Closing the Loop on Right Ventricular Mechanics

Corresponding Author

In 1970, Swan and Ganz introduced the pulmonary artery catheter (PAC), transforming critical care by enabling real-time, bedside hemodynamic monitoring of patients. However, in the decades since, the PAC has undergone little technical development. Despite its widespread adoption in the 1980s and 1990s, the conventional thermodilution-based PAC—and its later evolution into the continuous cardiac output PAC—has gradually fallen out of favor in many intensive care settings. Several studies and reviews have highlighted its limited clinical impact and even potential for harm, particularly when misused or overinterpreted in complex intensive care unit scenarios.¹

Yet, the PAC may be poised for a renaissance. Recent multicenter data from the Cardiogenic Shock Working Group, as reported by Khalife et al,² have reasserted the value of the PAC in cardiogenic shock, where invasive hemodynamics can guide timely escalation of therapies, including novel mechanical circulatory support systems. In this issue of JACC: Basic to Translational Science, Aslam et al³ present the next technical frontier: a modified PAC capable of generating real-time right ventricular (RV) pressure-volume (PV) loops for advance hemodynamic assessment. Their work represents a fusion of classical invasive tools with modern engineering and computational insight, offering a novel pathway to project this old tool into the realm of precision cardiovascular care (Figure 1).

Figure 1.

Closing the Loop on Right Ventricular Mechanics: Past, Present and Future of the Pulmonary Artery Catheter

The authors elegantly navigate the central challenge of RV volume measurement—its nongeometric, crescentic morphology—by leveraging complex admittance signals in a tetrapolar measurement configuration focused on the right ventricular outflow tract (RVOT). Using a swine model, their novel PAC was validated against 2 independent standards: cardiac magnetic resonance imaging and ex vivo foam casts. End-diastolic and -systolic volumes showed good agreement, with minimal bias, although wide CIs highlighted the expected variability inherent to both biologic and electrical measurement systems. Crucially, the device captured physiologic responses to positive inotropic interventions, such as dobutamine and phenylephrine, as well as cardiac injury developing from right coronary artery microsphere-induced ischemia combined with beta-blocker administration. Notably, the novel PAC detected progressive RV dilation during acute ischemic injury—a clinically meaningful signal traditionally inaccessible to standard PACs. Furthermore, the ability to derive elastance, arterial load, and RV-PA coupling from a single PAC in real time represents a major technical and conceptual advancement, transforming a long-static tool into a dynamic monitor of RV function.

Among the strengths of this study, the combination of robust biophysical modeling with careful in vivo validation stands out as particularly noteworthy. The use of finite element analysis to inform electrode configuration and validate field localization strengthens confidence in the specificity of the admittance signal. The dual calibration approach—based on Baan’s classical method of combining saline-based estimation of Ginf (the conductance at infinite volume) with thermodilution-derived stroke volume—reflects a rigorous application of established principles to the anatomically complex RV. Unlike earlier conductance-based implementations by Baan and Wei,^8,9 this study employs admittance technology, which integrates both magnitude and phase data to more accurately estimate dynamic RV volumes.

The thoughtful experimental protocol employed by the authors is another major strength. By including both inotropic stimulation and acute ischemic injury, the authors demonstrate that their device captures not only static volumetric accuracy but dynamic responses across a range of RV loading and inotropic states. This is essential for future clinical translation, where the real-world utility of RV-PV loop analysis will rely on its ability to reflect changes in preload, afterload, and contractility over time.

As with any prototype, certain limitations must be acknowledged. While the catheter’s focus on the RVOT enables a technically elegant and innovative solution to a complex anatomical problem, it also necessitates assumptions to extrapolate total RV volume. The authors address this by partitioning stroke volume and referencing prior RV deformation data—a thoughtful approach grounded in anatomical insight—but this methodology inherently introduces potential sources of variability. Indeed, Bland-Altman analysis reveals wide limits of agreement, reflecting both interanimal differences and geometric complexity.

Another technical constraint is the trade-off between incorporating admittance wires and retaining full PAC functionality. In this study, the thermal filament was sacrificed to accommodate admittance components, although future designs utilizing 7.5-F PACs may overcome this. Catheter stiffness, signal stability with motion, and electrode positioning in human RVs all present hurdles on the path to clinical application.

Finally, while inferior vena cava occlusion (IVCO) enables gold-standard multi-beat elastance calculation and was essential for validating the catheter's ability to assess dynamic RV function, its applicability in routine human use is limited. Although alternatives such as external compression or single-beat estimation are explored, clinical translation will require simplified, reproducible workflows that align with standard hospital protocols.

The potential clinical impact of an admittance-enabled PAC is substantial. Intraoperative and postoperative RV dysfunction is a well-documented and potentially lethal complication in patients with pre-existing right or biventricular heart failure and pulmonary hypertension.⁴ Predicting and assessing RV dysfunction during surgery is particularly challenging because of the ventricle's complex response to surgical manipulation, anesthesia, and shifting loading conditions. Standard tools such as transesophageal echocardiography are limited by poor visualization of the RV, while conductance catheters—although considered the gold standard—are rarely used intraoperatively because of their complexity. An admittance-enabled PAC capable of real-time RV-PV analysis could address this gap by offering continuous, load-sensitive, and geometry-independent measurements of RV function. Lo Muzio et al⁵ recently demonstrated this potential by characterizing RV mechanics in a porcine model of progressive RV pressure overload, showing that conductance-derived PV loops and video kinematic analysis could detect a broad spectrum of intraoperative RV dysfunction with high fidelity. Similarly, in advanced heart failure populations, especially those considered for left ventricular assist device implantation, accurate prediction of RV failure remains an unmet need,⁶ despite numerous proposed scores and hemodynamic indices. A PAC capable of providing an accurate characterization of RV-PA coupling and reserve could guide both timing and patient selection for mechanical circulatory support.

In valvular heart disease, particularly functional tricuspid regurgitation (TR), the complexity of RV physiology and the heterogeneity of disease mechanisms continue to challenge patient selection for transcatheter interventions.⁷ Real-time RV volumetrics may help stratify patients who are likely to benefit from transcatheter therapies by distinguishing those with primary RV dysfunction from those with predominantly afterload-driven TR. The inclusion of the RVOT—a segment with high contractile contribution—further enhances the physiologic relevance of this new catheter design.

Future developments in catheter design hold substantial promise. Enhancing the system to enable simultaneous measurement of both RV inflow and outflow volumes—as demonstrated in an encouraging early prototype—may improve the accuracy and spatial resolution of volumetric assessments. Additionally, miniaturization of the electrode array could reduce catheter stiffness, potentially facilitating safer and more efficient use in patients.

Clinical feasibility studies, ideally in patients undergoing routine right heart catheterization (eg, PAH, advanced heart failure, TR), will be crucial to validate safety, reproducibility, and added value beyond current standards. Ongoing studies such as the PACCS (Pulmonary Artery Catheter in Cardiogenic Shock Study; NCT05485376), which investigates the utility of conventional PAC in acute heart failure and cardiogenic shock, are expected to further clarify its clinical role. Although this trial does not incorporate admittance-based technology, it lays the groundwork for a potential next generation of randomized studies evaluating advanced PACs like the one described by Aslam et al,³ which offer real-time RV-PV loop data. Establishing normative ranges, defining thresholds for clinical intervention, and integrating PV-loop–derived metrics into clinical algorithms represent logical extensions of the work presented here.

The study by Aslam et al³ represents a major step toward revitalizing the pulmonary artery catheter—long a passive observer in hemodynamic assessment—into an active, quantitative tool for real-time RV function monitoring. By integrating admittance-based volume sensing into a familiar platform, the authors bridge the gap between legacy instrumentation and the demands of modern precision cardiology. Although further validation is needed, the path ahead is promising. In the realm of right ventricular assessment, the loop may finally be closing.

Funding Support and Author Disclosures

Dr Alogna is supported by the Deutsche Forschungsgemeinschaft (CRC 1470, Z01, and B02) and by the European Union’s Horizon Europe research and innovation programme under g.n. 101091765; and is founder of “NanoPhoria,” a preclinical stage biotech company developing a versatile, nonviral drug delivery platform based on inorganic nanoparticles.