PA Catheters in Cardiogenic Shock: Patchy Usage, Potential Gains

Pulmonary artery catheter (PAC) use in cardiac intensive care units (CICUs) across North America appears to depend more on the habits and preferences of treating physicians and institutions than it does on patient-level factors, write Bernard Kadosh, MD (New York University Langone Health, NY), and colleagues in JACC: Heart Failure this week.

But in the Critical Care Cardiology Trials Network (CCCTN), PAC use was associated with a reduced risk of mortality, at least in patients admitted with cardiogenic shock. The authors say this finding suggests—at a minimum—that usage is not harmful and may, in the right patient, improve outcomes.

The study could only look at association, not causation, Kadosh stressed to TCTMD, with the chief aim being to get an up-to-date picture of how PACs are being used. What they found is that “there is wide, wide variability in the use of pulmonary catheters in [cardiac] intensive care units now,” Kadosh said. “Looking at the various factors that influence their use, clinical factors were really only a small proportion of the decision making. A lot of the variability was just accounted for by institutional preference.”

That raises the question of what is really driving usage, he continued. “We have to know more about when to use these devices, when to use this strategy, when to use invasive hemodynamics and how to use it. There’s really more unanswered questions than there are answers in the paper, and I don't think that in a disease state that is associated with such a high level of mortality that we should be making decisions based on institutional preference.”

Multiple Guidelines, Little Consensus

International recommendations on the use of invasive PACs to monitor hemodynamics are decidedly mixed. While current American College of Cardiology/American Heart Association heart failure (HF) guidelines recommend against use of invasive hemodynamic monitoring in acute HF (class 3), they give its use class 1, level of evidence C, for use in HF patients in respiratory distress or signs of impaired perfusion when ventricular filling pressures are unclear by clinical parameters.

In shock specifically, the recently updated Society for Cardiovascular Angiography and Interventions (SCAI) expert consensus document condones the use of invasive hemodynamics to guide therapy, particularly for narrowing down shock phenotype to those needing biventricular or isolated right ventricular support.

Outside of North America, the 2021 European Society of Cardiology HF guidelines specify that invasive hemodynamic monitoring for diagnosis and management may help reduce mortality in shock, so long as it’s part of a standardized, team-based approach.

This is a call to action to say we need randomized clinical trials in this space. Bernard Kadosh

“This has been an ongoing discussion among critical care cardiologists and heart failure doctors for many, many years,” said Kadosh. “The use of pulmonary artery catheters has waxed and waned over time in response to various observational studies and clinical trials that were studying different populations, not necessarily the cardiogenic shock cohort, and those studies have been applied to our patients and sometimes not for the best,” said Kadosh. “Practice patterns have changed over time, our treatment of cardiogenic shock has changed over time; there are now new devices that can be applied to help patients to give us time to think about what to do next. So, the idea for this study was: in contemporary CICUs, should we be using invasive hemodynamics to inform our strategies?”

More than that, the researchers wanted to see what was happening, nationally, in terms of practice patterns and usage, he added. “What are the various hospitals doing and why are they making those decisions?”

A Shock Snapshot

For their study, Kadosh and colleagues analyzed data from the CCCTN for 13,618 CICU admissions at 34 sites across the US and Canada. Of these, 3,827 patients were admitted with shock (2,583 with cardiogenic shock). PAC monitoring was used in 2,719 patients overall: in 45.8% of all shock patients and in 55.6% of cardiogenic shock patients.

The proportion of shock admissions given PAC, however, “varied significantly by study center,” as low as 8% at some and up to 83% at others. Patient-centric factors most associated with PAC use were the use of mechanical circulatory support (OR 5.99; 95% CI 5.15-6.98) and a heart failure diagnosis (OR 3.33; 95% CI 2.91-3.81). Ventricular arrhythmias, pulmonary hypertension, and use of vasoactive agents also were more common, the authors note.

Notably, among all shock patients admitted to a CICU, use of a PAC versus no PAC was associated with lower mortality (OR 0.79; 95% CI 0.66-0.96).

Despite the mixed messages from professional groups and expert opinion papers, it’s clear that almost one in five patients admitted to a CICU is treated with a PAC, a figure that reaches nearly 50% in shock patients, the authors conclude. And in detailed analyses, PAC usage was associated with lives saved.

“This is a call to action to say we need randomized clinical trials in this space,” said Kadosh. “We need to understand more about how to use invasive hemodynamics and how to make decisions on treatment strategies for cardiogenic shock. And for really all forms of shock.”

That said, he clarified, this large group of investigators didn’t embark on this analysis with the assumption that PAC would have benefits in all shock. “What we’re saying here is, in cardiac patients who present with various forms of shock, maybe it's important to think about using invasive hemodynamics to figure out what the perturbation is in that patient, because if you have overlapping forms of shock the outcome may be worse if you don't know what's going on,” Kadosh explained. “There’s no way to prove that, based on our paper, but that should be considered for future study.”

At least one randomized trial is attempting to answer that question, he noted. The three-way PACCS trial, launched in August 2022, is testing whether early invasive hemodynamic assessment and ongoing management with a PAC in patients with cardiogenic shock due to acutely decompensated HF is associated with lower in-hospital mortality, compared with both no PAC and delayed PAC.

Evolving Understanding

Commenting on the paper for TCTMD, Srihari S. Naidu, MD (Westchester Medical Center, Valhalla, NY), who led the SCAI efforts to classify shock categories to better tailor treatment, highlighted three takeaways.

The first, he said, is that “despite the guidelines,” PAC use is increasing: a “refreshing” observation, albeit focused on major tertiary care centers. “I think what's evolved over time has been our understanding that the PA catheter can give us a lot more information than just whether the patient is dry, euvolemic, or hypovolemic,” said Naidu. “Now we're talking more about what the cardiac output is—is it high, low, appropriate—and also more importantly we're moving into the realm of phenotyping where now we understand the PA catheter can help us understand if the patient is having left ventricular failure, right ventricular failure, or biventricular failure and trying to tease both things out.”

The initial trials suggested that there was a hazard to using PA catheters that outweighed any meager benefit. Now you have a strong benefit and no noticeable risk. Srihari S. Naidu

The variability among centers also jumped out at him, although what’s notable, he said, is that while some institutions had high-usage patterns and others low, the proportion of patients by shock classification in which PACs were employed was “exactly the same,” he said. “That leads me to believe that there are clinicians at all the hospitals that do it the same way, but at the institutions that don't use it enough, they don't have as many of those clinicians.”

Perhaps most striking, he said, is the mortality finding. With PACs, he pointed out, you might expect mortality to be higher, because they are typically being used in the sickest patients—a finding that has long complicated the understanding of shock outcomes with percutaneous mechanical circulatory support devices, especially in the setting of acute MI.

“This together with other observational databases now do point to the fact that the PA catheter, especially in patients with cardiogenic shock, seems to be associated, increasingly, with reduced mortality and the mortality benefit is strong, about 21% in this study,” Naidu said.

What can’t be teased out in an observational study, of course, is whether PACs themselves reduce mortality, or whether it is the clinical acumen of the physicians who use them or other unmeasured factors.

“I do think that over time as new generations of fellows come out of training, especially in this area of mechanical support and advanced heart failure, there will be more utilization,” Naidu predicted. “I also think that not seeing a hazard in any of these [studies] is also very important to note, because the initial trials suggested that there was a hazard to using PA catheters that outweighed any meager benefit. Now you have a strong benefit and no noticeable risk.”