Medical Technology

Predicting Cardiac Shock Mortality in the ICU

Addition of echocardiogram measurement of biventricular dysfunction improved the accuracy of prognosis among patients with cardiac shock (CS) in the cardiac intensive care unit (CICU).

In patients in the CICU with cardiac shock, biventricular dysfunction (BVD) as assessed using transthoracic echocardiography improves clinical risk stratification when combined with the Society for Cardiovascular Angiography and Interventions (SCAI) shock stage.

No improvements in risk stratification was seen with patients with left or right ventricular systolic dysfunction (LVSD or RVSD) alone, according to an article published in the journal Chest.

Ventricular systolic dysfunction is commonly seen in patients who have suffered cardiac shock, most often on the left side. Although echocardiography is often performed on these patients during diagnosis, previous studies looking at ventricular dysfunction used invasive hemodynamic parameters, which made it challenging to incorporate their findings into general CICU practice.

Pinning Down Cardiac Shock

Although treatment of acute myocardial infarction and heart failure has improved greatly, particularly with the implementation of percutaneous coronary intervention (primary PCI) for ST-segment elevation MI (STEMI). This has reduced the rate of future heart failure, but cardiac shock can occur before or after the procedure, with a 30-day mortality of 30%-40%. This outcome hasn’t improved in the last 20 years.

Efforts to improve cardiac shock outcomes through percutaneous mechanical circulatory support devices have been hindered by the fact that CS patients are heterogeneous, and prognosis may depend on a range of factors.

SCAI was developed as a five-stage classification system for CS to improve communication of patient status, as well as to improve differentiation among patients participation in clinical trials. It does not include measures of ventricular dysfunction.

Simple Measure Boosts Prognosis Accuracy

The new work adds an additional layer to the SCAI shock stage. “Adding echocardiography allows discrimination between levels of risk for each SCAI stage,” said David Baran, MD, who was asked for comment. Baran was the lead author on the original SCAI study and is system director of advanced heart failure at Sentara Heart Hospital, as well as a professor of medicine at Eastern Virginia Medical School, Norfolk, Virginia.

The work also underscores the value of repeated measures of prognosis during a patient’s stay in the ICU. “If a patient is not improving, it may prompt a consideration of whether transfer or consultation with a tertiary center may be of value. Conversely, if a patient doesn’t have high-risk features and is responding to therapy, it is reassuring to have data supporting low mortality with that care plan,” said Baran.

The study may be biased, since not every patient undergoes an echocardiogram. Still, “the authors make a convincing case that biventricular dysfunction is a powerful negative marker across the spectrum of SCAI stages,” said Baran.

Echocardiography is simple and generally available, and some are even portable and used with a smartphone. But patient body size interferes with echocardiography, as can the presence of a ventilator or multiple surgical dressings. “The key advantage of echo is that it is completely noninvasive and can be brought to the patient in the ICU, unlike other testing which involves moving the patient to the testing environment,” said Baran.

The researchers analyzed data from 3158 patients admitted to the CICU at the Mayo Clinic Hospital St. Mary’s Campus, 51.8% of whom had acute coronary syndromes. They defined LVSD as a left ventricular ejection fraction less than 40%, and RVSD as at least moderate systolic dysfunction determined by semi-quantitative measurement. BVD constituted the presence of both LVSD and RVSD. They examined the association of in-hospital mortality with these parameters combined with SCAI stage.

BVD a Risk Factor

Overall in-hospital mortality was 10%. A total of 22.3% of patients had LVSD and 11.8% had RVSD; 16.4% had moderate or greater BVD. There was no association between LVSD or RVSD and in-hospital mortality after adjustment for SCAI stage, but there was a significant association for BVD (adjusted hazard ratio [HR], 1.815; P = .0023). When combined with SCAI, BVC led to an improved ability to predict hospital mortality (area under the curve [AUC], 0.784 vs 0.766; P < .001). Adding semi-quantitative RVSD and LVSD led to more improvement (AUC, 0.794; P < .01 vs both).

RVSD was associated with higher in-hospital mortality (adjusted odds ratio [aOR], 1.421; P = .02), and there was a trend toward greater mortality with LVSD (aOR, 1.336; P = .06). There was little change when SCAI shock stage A patients were excluded (aOR, 1.840; P < .001).

Patients with BVD had greater in-hospital mortality than those without ventricular dysfunction (aOR, 1.815; P = .0023), but other between-group comparisons were not significant.

The researchers performed a classification and regression tree (CART) analysis using left ventricular ejection fraction (LVEF) and semi-quantitative RVSD. It found that RVSD was a better predictor of in-hospital mortality than LVSD, and the best cutoff for LVSD was different among patients with RVSD and patients without RVSD.

Patients with mild or greater RVD and LVEF >24% were considered high risk; those with borderline or low RVSD and LVEF <33%, or mild or greater RVSD with LVEF ≥ 24%, were considered intermediate risk. Patients with borderline or no RVSD and LVEF ≥ 33% were considered low risk. Hospital mortality was 22% in the high-risk group, 12.2% in the intermediate group, and 3.3% in the low-risk group (aOR vs intermediate, 0.493; P = .0006; aOR vs high-risk, 0.357; P < .0001).

The study authors have disclosed no relevant financial relationships.

Chest. Published online October 1, 2021. Abstract

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