Advancing the Science

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December 14, 2021

Transforming care for patients in the cardiac intensive care unit

By Elizabeth Zimmermann
Jacob Jentzer, M.D., is a cardiovascular medicine physician specializing in ischemic heart disease and critical care. Additionally, Dr. Jentzer conducts research to better understand disease and to improve care for his patients, and people everywhere.

Jacob Jentzer, M.D., is a cardiac intensivist — meaning he has received specialized training to allow him to provide the best possible care for patients in intensive care who have severe heart conditions. He also is a Kern Health Care Delivery Scholar (@MayoKernScholar) with a portion of his time dedicated to further training in the concepts and methodologies of high-quality practice-based health services research. In addition, as a scholar, he is able to expand his outcomes-based research in cardiac care, applying findings to improve patient care for this high-risk group.

Dr. Jentzer had been able to contribute to the body of knowledge prior to becoming a Kern Scholar in 2020, but his dedicated research time has allowed him to hone in on his goal of developing a clinical decision-support tool for early detection and treatment of hemodynamic instability and shock in hospitalized patients.

"Dr. Kianoush Kashani has been an outstanding mentor, and with the additional resources from the Kern Center, my collaborators and I have been working toward development of predictive models using machine learning methods to predict the development of new-onset or worsening shock," says Dr. Jentzer. "We are using routinely collected clinical data in a large mixed cohort of Mayo Clinic intensive care unit patients. After the best predictive model is developed and validated, this will allow it to be connected with Mayo Clinic's electronic health record to gauge its real-world performance prior to clinical implementation."

In Dr. Jentzer's recent publications are indicators of the decision-support tool that he hopes will soon come into being. Summarized here are three examples of different routes he is investigating:

screen shot of system sample electrocardiogram (ECG) reading

When a patient experiences cardiogenic shock, their condition often deteriorates quickly. Rapid diagnosis and intervention are imperative and serve as the basis for Dr. Jentzer’s Kern Scholar project. Identifying the patient's shock severity stage — A to E as defined by the Society for Cardiovascular Angiography and Intervention — can help clinicians determine what treatments are most likely to help the patient stabilize.

Any sort of ventricular dysfunction in the heart can contribute to shock, but Dr. Jentzer and his colleagues thought there might be more information in the dysfunction than simply as a contributor to the shock stage.

The investigators analyzed the records of 3,158 adult patients admitted to Mayo Clinic's Cardiac Intensive Care Unit in Rochester, Minn., from Jan. 1, 2007, through Dec. 31, 2015. These patients had a transthoracic echocardiogram performed within one day before or after ICU admission, and data was available for both left and right ventricular systolic function, or dysfunction.

They found that biventricular dysfunction in a patient with mild shock stages — A or B — could put them at a higher risk of dying in the hospital than a patient with the next higher shock stage without the dysfunction.

"Although we typically talk about outcomes related to left ventricular dysfunction," says Dr. Jentzer, "in our study, we found that right ventricular systolic dysfunction was considerably more important for predicting mortality."

He and his colleagues report, "The addition of echocardiography assessment to the Society for Cardiovascular Angiography and Intervention shock criteria may facilitate improved clinical risk stratification."

In a related paper, Echocardiographic Correlates of Mortality Among Cardiac Intensive Care Unit Patients with Cardiogenic Shock, Dr. Jentzer and his Mayo Clinic colleagues provide further evidence of the value in incorporating more of the data generated from transthoracic echocardiogram into risk stratification and prognostics.

lab employee with mask on, gloves and lab coat, working with patient laboratory samples

Acidosis is a condition in which a person's blood chemistry balance is disrupted and their blood becomes more acidic than normal, which can compromise tissue and organ function. Lactic acidosis is one of the most common sources acidosis, caused by over production of lactic acid most commonly due to poor blood flow to the tissues and organs, which is called "shock." In some cases, the liver does not function normally or does not receive enough blood flow to clear the lactic acid from the bloodstream as well. High lactic acid levels have been linked to poor outcomes in many forms of critical illness..

"We knew that acidosis and excess lactate predict worse outcomes in patients with cardiogenic shock," says Dr. Jentzer, "However, we wanted to refine that knowledge to see if more severe acidosis at admission was incrementally more predictive of in-hospital mortality."

The team also hoped to better define the characteristics of a treatment-resistant shock state referred to as "hemometabolic shock."  Dr. Jentzer says the idea is that more severe metabolic abnormalities such as lactic acidosis would be associated with more severe shock and worse outcomes.

They analyzed the records of 1,078 adult patients admitted to the cardiac ICU with a diagnosis of cardiogenic shock from Jan. 1, 2007, through Dec. 31, 2015. The investigators used several existing tools to score the severity of each patient's illness. They also noted shock stages as defined by the Society for Cardiovascular Angiography and Intervention.

For this study, Dr. Jentzer and his team developed a composite acidosis score ranging from 0 to 5, with 2 or higher considered severe. The score was derived from select variables — arterial pH, arterial base excess and anion gap — obtained from laboratory analysis of patient blood samples at admission. This is described fully in their paper.

The researchers report that more severe levels of metabolic acidosis at admission were "strongly associated with in-hospital mortality, even when adjusting for the severity of shock and organ failure." However, they found that admission lactate levels were a better predictor of in-hospital mortality than their composite acidosis score.

"Our findings definitely need to be validated with a large prospective study, but it appears that hemometabolic shock can be defined in a 3-dimensional manner combining shock severity, organ failure and acidosis as independent yet interrelated constructs," says Dr. Jentzer. "If so, it could be added to our diagnostic toolkit and lead to more targeted treatment strategies."

intra-aortic balloon pump medical illustration of pump work station, male torso with critical systems highlighted, bulleted text describing use.

In this earlier publication, Dr. Jentzer and several colleagues examined what role use of an intra-aortic balloon pump has in predicting in-hospital mortality among patients experiencing varying stages of shock. An intra-aortic balloon pump is a balloon-like device inserted via catheter into the aorta. It expands and contracts in concert with a patient's beating heart to help improve the amount of blood pumped out of the heart for patients with shock.

Using the same database of patients admitted to the Mayo Clinic Cardiac Intensive Care Unit between Jan. 1, 2007, and Dec. 31, 2015, the investigators identified all patients with an admission diagnosis of cardiogenic shock. After excluding those without hemodynamic instability or hypoperfusion — shock stage A — the study cohort was 934 adult patients. Of these, 363 receive an intra-aortic balloon pump.

Overall, 343 patients died in the hospital. Patients who received an intra-aortic balloon pump had lower in-hospital mortality across all examined shock stages: B, C, D and E.

"As we expected, as the shock stage increased, so too did rates of in-hospital mortality," says Dr. Jentzer. "What we found surprising was that use of the balloon pump was associated with lower risk of mortality across the spectrum of shock severity."

"No one has done studies with the intra-aortic balloon pump in shock except among patients with acute coronary syndromes and these studies have not examined shock severity," he says. "Our findings suggest this device may be useful for some patients with cardiogenic shock but not acute coronary syndromes."

“Shock can be hard to recognize during its early stages, yet it is precisely these patients who have the most reversible disease," says Dr. Jentzer. "Once obvious shock has developed, outcomes are much worse for patients."

"Early recognition and ideally prediction of impending shock is a necessary step to improving the outcomes of patients with or at risk for shock," he continues.  "I believe that by developing and implementing novel predictive approaches in collaboration with the Kern Center, we can hope to stop this lethal disease before it starts in order to help our patients."

The team behind the science

In these highlighted studies, Dr. Jentzer's research collaborators from Mayo Clinic include:

In addition, several of the publications included one or more external co-authors:

  • David Baran, M.D., Sentara Heart Hospital, Advanced Heart Failure Center and Eastern Virginia Medical School, Norfolk, Virginia.
  • Barry Burstein, M.D., a prior Mayo Clinic Critical Care fellow, now Division of Cardiology, Trillium Health Partners, University of Toronto, Ontario, Canada.
  • Timothy Henry, M.D., The Carl and Edyth Lindner Center for Research and Education, Christ Hospital Health Network, Cincinnati, Ohio.
  • Sean Van Diepen, M.D., Department of Critical Care Medicine and Division of Cardiology, Department of Medicine, University of Alberta Hospital, Edmonton, Canada.

The Kern Health Care Delivery Scholar program is administered by the Mayo Clinic Robert D. and Patricia E. Kern Center for the Science of Health Care Delivery. The center is embedded in Mayo's medical practice and works hand-in-hand with the Practice to identify ways to improve outcomes, enhance experience, and increase value for patients, in short, to transform the practice of medicine.

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Tags: About, Brandon Wiley, cardiac intensive care unit, cardiology, Center for the Science of Health Care Delivery, David Holmes Jr., Findings, Gregory Barsness, health sciences research, ICU, intensive care unit, Jacob Jentzer, Kern Health Care Delivery Scholars, Kianoush Kashani, Meir Tabi, Nandan Anavekar, News, Parag Patel, People, pulmonary and critical care medicine, Sarma Singam, shock

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