Photo Credit: Hatice Gocmen

Readings from an implanted PAP monitoring device while a patient with heart failure stands are different from those taken while supine.

Pulmonary artery pressure (PAP) readings taken from an implanted PAP monitoring device while a patient with heart failure (HF) stands are different from readings taken while that patient is supine, results of a new study suggest.

“PAP in each patient should always be measured in the same position,” Kamal Gupta, MBBS, MD, and colleagues wrote in BMC Cardiovascular Disorders. “Since initial readings at the time of implant are taken in supine position, it may be best to use supine position or to obtain a baseline standing PAP reading if standing PAP is planned on being used.”

HF prevalence has increased in the US; between 2013 and 2016, an estimated 6.2 million American adults aged 20 year and older had HF. Previously viewed as a symptom of HF, recent research indicates that elevated PAP may instead contribute to left HF, the authors note, and monitoring PAP enables early HF detection and treatment.

“Implantable devices that can measure PAP in patients 24/7 are increasingly being used to manage patients with heart failure,” Dr. Gupta explains. “Newer devices are in advanced human clinical trials, and clinical trials are being conducted on the use of these devices in other disease states where accurate PAP assessments will be extremely helpful.”

Standing PAP Significantly Lower Than Supine PAP

To investigate how changing from a supine to a sitting position affects PAP in ambulatory HF patients, Dr. Gupta and colleagues conducted a prospective study of patients who visited the HF clinic of a large academic tertiary care hospital.

Beginning in December 2020 and continuing for two years, the study team enrolled adult ambulatory patients who had stable heart failure, no diuretic medication change in the preceding 2 weeks, and a CardioMEMS (Abbott) sensor previously implanted in a pulmonary artery.

A total of 17 participants aged 76.2 (mean) with a mean BMI of 34.9 kg/m² completed the study. Overall, 35.2% were female, and 94.1% were White. Comorbidities included coronary artery disease, hypertension, diabetes mellitus, obstructive sleep apnea, chronic obstructive pulmonary disease, and chronic kidney disease. Overall, 47.1% had HF with reduced ejection fraction (left ventricular ejection fraction <40%), and 11.7% had HF with recovered left ventricular ejection fraction. The study team did not record medications.

For each participant, the researchers recorded 10 seconds of PAP data using a hand-held interrogator while the patient was supine. After the patient then stood for at least 5 minutes, the researchers recorded the standing PAP data. In both conditions, Gupta and colleagues also recorded systemic blood pressure and heart rate. They used the paired T-test to compare supine and standing PAP values.

They found the following significant mean declines in PAP readings from supine to standing positions (Table), respectively: Systolic PAP difference of 9.9 mmHg (P<0.001); diastolic PAP 6.3 mmHg (P<0.001); and mean PAP 7.4 mmHg (P<0.001). Systemic blood pressure and heart rate measurements did not vary significantly.

PAP Increasingly Important to Manage HF

Although PAP has been shown to play a significant role in ambulatory HF patient management, the literature on pathophysiological PAP variations in ambulatory settings is lacking, the authors write.

Understanding how PAP changes with body position is important; and if further related studies corroborate their findings, “readings obtained from patients need to be standardized,” Dr. Gupta advises. “Our study is a first step in this direction, and more work with larger patient samples is needed.”

The authors acknowledge limitations to the study, including its small sample size, lack of participant diversity, inclusion of only patients with compensated HF on stable doses of diuretics, and its lack of evaluating the effects of comorbidities, gender, and specific medi­cations or dosages.

“Thus, we are unable to say if these findings would also be seen in those not on diuretics or in a decompensated state,” they add. “A larger study should be considered in the future for findings which could be applicable to larger population.”