Right Heart Function in Critically Ill Patients at Risk for Acute Right Heart Failure: A Description of Right Ventricular-Pulmonary Arterial Coupling, Ejection Fraction and Pulmonary Artery Pulsatility Index

Assessment and diagnosis of right ventricular failure-retrospection and future directions

The right ventricle (RV) has a critical role in hemodynamics and right ventricular failure (RVF) often leads to poor clinical outcome. Despite the clinical importance of RVF, its definition and recognition currently rely on patients' symptoms and signs, rather than on objective parameters from quantifying RV dimensions and function. A key challenge is the geometrical complexity of the RV, which often makes it difficult to assess RV function accurately. There are several assessment modalities currently utilized in the clinical settings. Each diagnostic investigation has both advantages and limitations according to its characteristics. The purpose of this review is to reflect on the current diagnostic tools, consider the potential technological advancements and propose how to improve the assessment of right ventricular failure. Advanced technique such as automatic evaluation with artificial intelligence and 3-dimensional assessment for the complex RV structure has a potential to improve RV assessment by increasing accuracy and reproducibility of the measurements. Further, noninvasive assessments for RV-pulmonary artery coupling and right and left ventricular interaction are also warranted to overcome the load-related limitations for the accurate evaluation of RV contractile function. Future studies to cross-validate the advanced technologies in various populations are required.

Longitudinal Validation of Right Ventricular Pressure Monitoring for the Assessment of Right Ventricular Systolic Dysfunction in a Large Animal Ischemic Model

Right ventricular (RV) dysfunction is a major cause of morbidity and mortality in intensive care and cardiac surgery. Early detection of RV dysfunction may be facilitated by continuous monitoring of RV waveform obtained from a pulmonary artery catheter. The objective is to evaluate the extent to which RV pressure monitoring can detect changes in RV systolic performance assess by RV end-systolic elastance (E_es) following the development of an acute RV ischemic in a porcine model.

HYPOTHESIS

RV pressure monitoring can detect changes in RV systolic performance assess by RV E_es following the development of an acute RV ischemic model.

METHODS AND MODELS

Acute ischemic RV dysfunction was induced by progressive embolization of microsphere in the right coronary artery to mimic RV dysfunction clinically experienced during cardiopulmonary bypass separation caused by air microemboli. RV hemodynamic performance was assessed using RV pressure waveform-derived parameters and RV E_es obtained using a conductance catheter during inferior vena cava occlusions.

RESULTS

Acute ischemia resulted in a significant reduction in RV E_es from 0.26 mm Hg/mL (interquartile range, 0.16-0.32 mm Hg/mL) to 0.14 mm Hg/mL (0.11-0.19 mm Hg/mL; p < 0.010), cardiac output from 6.3 L/min (5.7-7 L/min) to 4.5 (3.9-5.2 L/min; p = 0.007), mean systemic arterial pressure from 72 mm Hg (66-74 mm Hg) to 51 mm Hg (46-56 mm Hg; p < 0.001), and mixed venous oxygen saturation from 65% (57-72%) to 41% (35-45%; p < 0.001). Linear mixed-effect model analysis was used to assess the relationship between E_es and RV pressure-derived parameters. The reduction in RV E_es best correlated with a reduction in RV maximum first derivative of pressure during isovolumetric contraction (dP/dt_max) and single-beat RV E_es. Adjusting RV dP/dt_max for heart rate resulted in an improved surrogate of RV E_es.

INTERPRETATION AND CONCLUSIONS

Stepwise decreases in RV E_es during acute ischemic RV dysfunction were accurately tracked by RV dP/dt_max derived from the RV pressure waveform.

Right Ventricular Pulmonary Artery Coupling and Mortality in Cardiac Intensive Care Unit Patients

Background

Impaired right ventricular (RV) pulmonary artery coupling has been associated with higher mortality in patients with chronic heart disease, but few studies have examined this metric in critically ill patients. We sought to evaluate the association between RV pulmonary artery coupling, defined by the ratio of tricuspid annular peak systolic tissue Doppler velocity (TASV)/estimated RV systolic pressure (RVSP), and mortality in cardiac intensive care unit patients.

Methods and Results

Using a database of unique cardiac intensive care unit admissions from 2007 to 2018, we included patients with TASV/RVSP ratio measured within 1 day of hospitalization. Hospital mortality was analyzed using multivariable logistic regression, and 1‐year mortality was analyzed using multivariable Cox proportional‐hazards analysis. We included 4259 patients with a mean age of 69±15 years (40.1% women). Admission diagnoses included acute coronary syndrome in 56%, heart failure in 52%, respiratory failure in 24%, and cardiogenic shock in 12%. The mean TASV/RVSP ratio was 0.31±0.14, and in‐hospital mortality occurred in 7% of patients. Higher TASV/RVSP ratio was associated with lower in‐hospital mortality (adjusted unit odds ratio, 0.68 per each 0.1‐unit higher ratio; 95% CI, 0.58–0.79; P<0.001) and lower 1‐year mortality among hospital survivors (adjusted unit hazard ratio, 0.83 per each 0.1‐unit higher ratio; 95% CI, 0.77–0.90; P<0.001). Stepwise decreases in hospital and 1‐year mortality were observed in each higher TASV/RVSP quintile. The TASV/RVSP ratio remained associated with mortality after adjusting for left ventricular systolic and diastolic function.

Conclusions

A low TASV/RVSP ratio is associated with increased short‐term and long‐term mortality among cardiac intensive care unit patients, emphasizing importance of impaired RV pulmonary artery coupling as a determinant of poor prognosis. Further study is required to determine whether interventions to optimize RV pulmonary artery coupling can improve outcomes.

The contemporary pulmonary artery catheter. Part 2: measurements, limitations, and clinical applications

Nowadays, the classical pulmonary artery catheter (PAC) has an almost 50-year-old history of its clinical use for hemodynamic monitoring. In recent years, the PAC evolved from a device that enabled intermittent cardiac output measurements in combination with static pressures to a monitoring tool that provides continuous data on cardiac output, oxygen supply and-demand balance, as well as right ventricular performance. In this review, which consists of two parts, we will introduce the difference between intermittent pulmonary artery thermodilution using bolus injections, and the contemporary PAC enabling continuous measurements by using a thermal filament which heats up the blood. In this second part, we will discuss in detail the measurements of the contemporary PAC, including continuous cardiac output measurement, right ventricular ejection fraction, end-diastolic volume index, and mixed venous oxygen saturation. Limitations of all of these measurements are highlighted as well. We conclude that thorough understanding of measurements obtained from the PAC is the first step in successful application of the PAC in daily clinical practice.

Integrated use of cardiac MRI and the CardioMEMS™ HF system in PAH: the utility of coincident pressure and volume in RV failure-the NHLBI-VITA trial

Background

This study aims to study the feasibility and safety of measuring volumetric and pressure parameters noninvasively using simultaneous cardiovascular magnetic resonance (cMR) volumetric data and time-resolved pressure waveforms from previously implanted CardioMEMS devices in pulmonary arterial hypertension (PAH) patients. Opportunities to intervene during clinically occult phases in PAH promise to herald a key transformation in our current practice for treating this complex population. Currently, it is possible and convenient to monitor daily pulmonary arterial (PA) pressures in PAH patients using the CardioMEMS device to determine clinically silent progression. Supplementation of these pressures with other prognostic measurements of right ventricular (RV) contractility, PA resistance and RV/PA coupling could add further predictive capabilities.

Methods

PAH patients (n=17) with New York Hospital Association (NYHA) class III or IV heart failure (HF) and recent HF related hospitalizations were implanted with the CardioMEMS device as part of a NHLBI sponsored Trial. Implanted patients were then assessed using cMR imaging of the right ventricle (RV) along with measurement of pulmonary artery flow. Patients were imaged at one-month post implant (baseline) and at 4-month follow-up time (n=12). At baseline, patients were studied at rest and then under three different physiologic conditions: inhaled nitric oxide (INO), dobutamine (Dob) stress and volumetric stress (Vol), using a multiple slice short-axis imaging and a rapid imaging protocol.

Results

All patients were safely imaged, with no artifacts obscuring the cMR images. RV volumes were measured successfully at rest and under each stress condition using a reduced scan approach that required calibration for each patient which achieved a correlation r² of 0.98. Variables measured included the maximal pulmonary artery elastance (Ea), maximal RV myocardial elastance (Emax) and ventricular-vascular coupling ratio (VVC). The response to stressors was determined on a patient basis. No complications occurred during the cMRI examination.

Conclusions

It is safe and feasible to perform cMR imaging with simultaneous pulmonary artery pressure readings from the CardioMEMS device. A reduced scan approach was developed to allowed measurement of RV volumes during stress conditions. Volumetric and pressure measurements can be combined to assess fundamental myocardial properties (e.g., Emax, Ea and VVC) in PAH patients serially over time. In the future, these parameters can be tested as serial predictors of outcome and response to therapies in PAH.