Non-Invasive Measurement of Cardiac Output and Stroke Volume in PE

Pulmonary embolism impacts over 1 in 1000 adults annually and is the third leading cause of cardiovascular death after heart attack and stroke. The consequence of each PE is widely variable. Physiologically, the morbidity and mortality of PE is ultimately caused by failure of the right ventricle. The acute rise in pulmonary vascular resistance caused by a PE can overwhelm the right ventricle, resulting in a drop in cardiac output and death from failure of the heart to provide vital perfusion. Despite the importance of stroke volume and cardiac output in the current understanding of PE mortality, they are notably absent from risk stratification scores because they historically could only be measured invasively.

Novel non-invasive methods of estimating stroke volume and associated cardiac output have the potential to revolutionize PE risk stratification and care. Non-invasive blood pressure (NIBP) monitors can even measure stroke volume beat to beat, allowing for continuous evaluation of cardiac function. NIBP systems are typically composed of a finger cuff with an inflatable bladder, pressure sensors, and light sensors. An arterial pulse contour is formed using the volume clamp method of blood pressure measurement combined with calibration and brachial pressure reconstruction algorithms. The stroke volume with each heart beat can be estimated as the area under the systolic portion of the blood pressure curve divided by the afterload. NIBP monitors may improve clinical care of PE because they allow for assessment of dynamic cardiac changes in real time. Detection of worsening stroke volume in acute PE could inform providers of impending cardiac collapse, and improvement of stroke volume may function as a positive prognostic factor or marker of therapeutic success. Use of NIBP monitors during acute PE to identify clinically significant changes in cardiac function may advance both PE prognostication and management.

Our clinical study proposes to monitor hemodynamic parameters including stroke volume in patients with acute pulmonary embolism using non-invasive blood pressure monitors. The relationship between hemodynamic parameters and PE outcomes will be assessed, as well as the changes in hemodynamic parameters with PE intervention. To our knowledge, interval monitoring of stroke volume during acute PE with NIBP monitors has never been reported before.

This is a single center study to evaluate the use of non-invasive measurement of stroke volume and cardiac output to assess risk and response to treatment in patients with acute pulmonary embolism (PE). A total of 40 subjects at Ronald Reagan UCLA Medical Center are anticipated to be enrolled.

After informed consent is obtained, the following procedure will be performed:

Patients requiring ICU level care with confirmed diagnosis of PE by CT angiogram or EBUS will be connected to a device that measures hemodynamics non-invasively called the Edwards ClearSight system and Edwards EV1000 clinical platform for 12 to 24 hours. The device is a finger probe worn with a supportive forearm strap. Hemodynamic measurements from the finger cuff will be recorded at intervals. After 12 hours, measurements will be taken if patient comfort and compliance allows.

Patients will be followed through their hospitalization. Standard of care data will be collected from the medical record including vital signs, cardiac monitor recordings, baseline electrocardiogram, central venous pressure (CVP) if available, ventilator settings and measurements, labs (troponin, d-dimer, lactate, pH, complete blood count, basic metabolic panel, B-type natriuretic peptide (BNP) or N-terminal-pro hormone BNP (NT-proBNP), prothrombin time and international normalized ratio (PT/INR), anti-Xa assay, and partial thromboplastin time (PTT)), imaging, interventions performed, therapies administered, discharge outcome and functional status.

As this is a study looking at the feasibility of non-invasive measurement of cardiac output and stroke volume for treating acute pulmonary embolism, study personnel performing the study procedures will not be blinded to the clinical diagnosis and the management of the subject.