Usefulness of a Noninvasive Device to Identify Elevated Left Ventricular Filling Pressure Using Finger Photoplethysmography During a Valsalva Maneuver

Photoplethysmography and intracardiac pressures: early insights from a pilot study

Aims

Invasive haemodynamic monitoring of heart failure (HF) is used to detect deterioration in an early phase thereby preventing hospitalizations. However, this invasive approach is costly and presently lacks widespread accessibility. Hence, there is a pressing need to identify an alternative non-invasive method that is reliable and more readily available. In this pilot study, we investigated the relation between wrist-derived photoplethysmography (PPG) signals and the invasively measured pulmonary capillary wedge pressure (PCWP).

Methods and results

Fourteen patients with aortic valve stenosis who underwent transcatheter aortic valve replacement with concomitant right heart catheterization and PPG measurements were included. Six unique features of the PPG signals [heart rate, heart rate variability, systolic amplitude (SA), diastolic amplitude, crest time (CT), and large artery stiffness index (LASI)] were extracted. These features were used to estimate the continuous PCWP values and the categorized PCWP (low < 12 mmHg vs. high ≥ 12 mmHg). All PPG features resulted in regression models that showed low correlations with the invasively measured PCWP. Classification models resulted in higher performances: the model based on the SA and the model based on the LASI both resulted in an area under the curve (AUC) of 0.86 and the model based on the CT resulted in an AUC of 0.72.

Conclusion

These results demonstrate the capability to non-invasively classify patients into clinically meaningful categories of PCWP using PPG signals from a wrist-worn wearable device. To enhance and fully explore its potential, the relationship between PPG and PCWP should be further investigated in a larger cohort of HF patients.

Noninvasive Point of Care Device for Assessing Cardiac Response to Acute Volume Changes

Purpose

The change in the amplitude of a peripheral pulse in response to a Valsalva maneuver has diagnostic utility for assessing volume status at the bedside. We have developed a device to automatically quantify the Valsalva pulse response (VPR) to a standardized Valsalva maneuver that the device guides a user to perform. In this study, we sought to determine whether VPR by the device, Indicor, is sensitive enough to detect the acute increase in central pressure and volume load that occurs with a passive leg raise (PLR) in healthy volunteers.

Methods

Healthy volunteers were tested semirecumbently at 45 degrees, then again after being leaned back on a pivoted wedge with legs raised at 45 degrees and torso and head flat, and then again in the semirecumbent position. The device recorded a finger photoplethysmography (PPG) signal during a 10-second expiratory effort of 20 mmHg as guided by the device. VPR was automatically calculated as the ratio of the end-Valsalva pulse amplitude to the baseline pulse amplitude.

Results

In the 30 participants who completed testing, VPR increased from baseline to PLR in every participant, from 0.34 ± 0.13 to 0.60 ± 0.14 (p < 0.0001). Back upright, VPR decreased back to 0.33 ± 0.10 (p < 0.0001 versus PLR; NS versus baseline position).

Conclusion

In this proof-of-concept study of healthy participants, the Indicor device, a noninvasive, convenient device that automatically calculates VPR from a finger photoplethysmography signal during a standardized Valsalva maneuver, was sensitive enough to detect the increase in VPR that occurred with an acute central volume load from a PLR. Future studies should examine whether VPR responds differently to a PLR in heart failure patients with abnormal cardiac performance and/or congestion.

Quantifying changes in size of arrhythmic photoplethysmography waveforms during a Valsalva maneuver for assessing cardiac filling pressure

OBJECTIVE

We previously showed that the change in amplitude of a finger photoplethysmography waveform during the Valsalva maneuver reflects cardiac filling pressure. However, the automated determination of peaks and valleys to calculate amplitude is limited in significant arrhythmias such as atrial fibrillation and premature ventricular complexes, which are common in heart failure. The purpose of this study was to assess the change in size of the waveform by calculating the change in root mean square (RMS) of the signal, thereby utilizing the entire cardiac cycle, and to compare it to change in size of peak-to-valley amplitude.

APPROACH

We compared the two approaches in signals obtained from participants of a prior study who were tested prior to a clinically indicated cardiac catheterization. Correlation between the two methods was assessed in cases without, and then with, significant arrhythmias including atrial fibrillation or premature ventricular complexes.

MAIN RESULTS

Calculations from the two methods of peak-valley amplitude and RMS were highly correlated with each other in signals without (0.99, p < 0.0001, n = 252) and with significant arrhythmias (0.90, p < 0.0001, n = 34).

SIGNIFICANCE

RMS analysis of photoplethysmography signal size during the Valsalva maneuver is highly correlated with the method of analyzing changes in peak-valley amplitude, but does not rely on identifying peaks and valleys. The RMS method may be a more robust automated method of assessing cardiac filling pressure in patients with significant arrhythmias.

Usefulness of Noninvasively Measured Pulse Amplitude Changes During the Valsalva Maneuver to Identify Hospitalized Heart Failure Patients at Risk of 30-Day Heart Failure Events (from the PRESSURE-HF Study)

The pulse amplitude ratio (PAR), the ratio of pulse pressure at the end of the Valsalva maneuver to before the onset, correlates with cardiac filling pressure. We have developed a handheld device that uses finger photoplethysmography to measure PAR and estimate left ventricular end diastolic pressure (LVEDP). Patients hospitalized with heart failure (HF) performed three 10-second trials of a standardized Valsalva maneuver (at 20 mm Hg measured via pressure transducer), while photoplethysmography waveforms were recorded, at admission and discharge. Combined primary outcome was 30-day HF hospitalization, intravenous diuresis, or death. Fifty-two subjects had discharge PAR testing; 12 met the primary outcome. Median PAR on admission was 0.55 (interquartile range: 0.40 to 0.70, n = 48) and on discharge was 0.50 (interquartile range: 0.36 to 0.69). Mean PAR-estimated LVEDP was significantly higher in subjects that had an event (20.2 vs 16.9 mm Hg, p = 0.043). Subjects with PAR-estimated LVEDP >19.5 mm Hg had an event rate hazard ratio of 4.57 (95% confidence interval 1.37, 15.19, p = 0.013) compared with patients with LVEDP 19.5 mm Hg or below, with significantly lower 30-day event-free survival (log-rank p = 0.006). In conclusion, noninvasively estimated LVEDP using the pulse amplitude response to a Valsalva maneuver in patients hospitalized for HF changes with diuresis and identifies patients at high risk for 30-day HF events. Detection of elevated filling pressures before hospital discharge may be useful in guiding HF management to reduce HF events.

Cardiac Triangle Mapping: A New Systems Approach for Noninvasive Evaluation of Left Ventricular End Diastolic Pressure

Noninvasive and practical assessment of hemodynamics is a critical unmet need in the treatment of both chronic and acute cardiovascular diseases. Particularly, the ability to monitor left ventricular end-diastolic pressure (LVEDP) noninvasively offers enormous benefit for managing patients with chronic congestive heart failure. Recently, we provided proof of concept that a new cardiac metric, intrinsic frequency (IF), derived from mathematical analysis of non-invasively captured arterial waveforms, can be used to accurately compute cardiovascular hemodynamic measures, such as left ventricle ejection fraction (LVEF), by using a smartphone. In this manuscript, we propose a new systems-based method called cardiac triangle mapping (CTM) for hemodynamics evaluation of the left ventricle. This method is based on intrinsic frequency (IF) and systolic time interval (STI) methods that allows computation of LVEDP from noninvasive measurements. Since the CTM method only requires arterial waveform and electrocardiogram (ECG), it can eventually be adopted as a simple smartphone-based device, an inexpensive hand-held device, or perhaps (with future design modifications) a wearable sensor. Such devices, combined with this method, would allow for remote monitoring of heart failure patients.

Usefulness of Pulse Amplitude Changes During the Valsalva Maneuver Measured Using Finger Photoplethysmography to Identify Elevated Pulmonary Capillary Wedge Pressure in Patients With Heart Failure

The pulse amplitude ratio, the ratio of pulse pressure at the end of a Valsalva maneuver to before the onset of Valsalva, correlates with filling pressure. This study aimed to noninvasively estimate cardiac filling pressure in patients with heart failure. We developed a noninvasive handheld device to measure pulse amplitude ratio using finger photoplethysmography. In 69 patients who underwent right heart catheterization, photoplethysmography waveforms were recorded during a standardized Valsalva maneuver, and in 60 of these patients, pulse amplitude ratio was able to be calculated. Pulse amplitude ratio correlated with pulmonary capillary wedge pressure (PCWP) (r = 0.58, p <0.0001), particularly among those subjects with reduced ejection fraction (r = 0.60, p = 0.002, n = 25). A multivariable linear regression model for PCWP including pulse amplitude ratio, age, body mass index, systolic blood pressure, diastolic blood pressure, and heart rate yielded an R² of 0.54. Difference in mean pulse amplitude ratio for subjects with a PCWP ≤15 mm Hg versus >15 mm Hg was statistically significant (p <0.0001, area under receiver operating characteristics curve 0.79 [0.66, 0.92]). Pulse amplitude ratio ≥0.55 predicted PCWP >15 mm Hg with 73% sensitivity and 77% specificity. Pulse amplitude ratio also increased by an average of 0.03 with a leg raise maneuver (p = 0.05, n = 36). In conclusion, we demonstrate that noninvasively measured response to the Valsalva maneuver in patients with HF can estimate PCWP and also detect changes within a single patient.

Autonomic dysfunction as a mechanism of intradialytic blood pressure instability

The autonomic nervous system (ANS) is the principal endogenous defense mechanism that maintains blood pressure in the setting of hypotension. Disruption of the ANS impairs this ability and can contribute to blood pressure instability, including hypotension and hypertension. In this narrative review, we provide an overview of the ANS and the consequences of its dysfunction in patients with end-stage kidney disease treated with dialysis. We also discuss possible mechanisms of this autonomic dysfunction that may need future investigation.