Pulse Transit Time Index Research Articles

Abstract 13817: Very Short-Term Blood Pressure Variability by Pulse Transit Time-Based Measurements During Sleep Predicts Future Cardiovascular Events in Patients With Ischemic Heart Disease

Background: Blood pressure (BP) variability (BPV) is recognized as an independent factor associated with cardiovascular (CV) events. However, monitoring very short-term BPV, which occurs within seconds or minutes remains challenging, and its prognostic impact has yet to be established. In a previous study, we reported that pulse transit time (PTT) enabled monitoring beat-to-beat BP, which is useful for evaluating very short-term BPV during sleep. Aims: This study aimed to clarify the prognostic relevance of PTT-based very short-term BPV during sleep. Methods and Results: We conducted a prospective study involving 206 consecutive hospitalized patients (mean 67.6 years old, 78.1% male) with ischemic heart disease. PTT-driven BP was continuously recorded during the night. To assess very short-term BPV, we defined the PTT index as the average number of acute transient rises in systolic BP (≥12 mmHg) within 30 s/h, and the standard deviation (SD) of PTT-BP was calculated. We followed up with patients for a median of 759 days and observed 49 CV events, including cardiac death, worsening heart failure, acute coronary syndrome, and ischemic stroke. Kaplan-Meier analysis revealed that patients with higher PTT index, as well as higher SD of mean and diastolic PTT-BP were associated with increased CV events ( Figure ). In a multivariate Cox proportional hazards analysis, after adjusting for confounding variables, PTT index, as well as SD of mean and diastolic PTT-BP were independently associated with increased risks of adverse events (hazard ratio, 1.019, 1.245, and 1.244; P = 0.02, 0.04, and 0.09, respectively). Conclusions: PTT-index and SD of mean and diastolic BP during the night, which represent measures of very short-term BPV, predicted the future risk of CV events in patients with ischemic heart disease through the PTT-driven approach and may serve as a target to reduce the residual risk in such patients.

Effects of continuous positive airway pressure on very short-term blood pressure variability associated with sleep-disordered breathing by pulse transit time-based blood pressure measurements.

Blood pressure (BP) variability (BPV) is a predictor of cardiovascular outcomes independently of BP absolute values. We previously reported that pulse transit time (PTT) enables monitoring beat-to-beat BP, identifying a strong relationship between the extent of very short-term BPV and the severity of sleep-disordered breathing (SDB). Here, we investigated the effects of continuous positive airway pressure (CPAP) on very short-term BPV. We studied 66 patients (mean age 62 years old, 73% male) with newly diagnosed SDB who underwent full polysomnography on two consecutive days for diagnosis (baseline) and CPAP, together with PTT-driven BP continuous recording. PTT index was defined as the average number of acute transient rises in BP (≥12 mmHg) within 30 s/h. CPAP treatment effectively improved SDB parameters, and attenuated PTT-based BP absolute values during the night-time. Very short-term BPV that includes PTT index and standard deviation (SD) of systolic PTT-BP was significantly reduced by CPAP therapy. The changes in PTT index from baseline to CPAP were positively correlated with the changes in apnea-hypopnea index, obstructive apnea index (OAI), oxygen desaturation index, minimal SpO 2 , and mean SpO 2 . Multivariate regression analysis revealed that changes in OAI and minimal SpO 2 , as well as heart failure, were the independent factors in determining the reduction of PTT index following CPAP. PTT-driven BP monitoring discovered the favorable effects of CPAP on very short-term BPV associated with SDB events. Targeting very short-term BPV may be a novel approach to identifying individuals who experience greater benefits from CPAP.

Abstract 9881: Effects of CPAP on Very Short-Term Blood Pressure Variability Associated With Sleep-Disordered Breathing Determined by Pulse-Transit-Time-Based Blood Pressure Measurements

Background: Sleep-disordered breathing (SDB) and blood pressure (BP) variability are closely associated with cardiovascular diseases. We have recently reported that pulse-transit-time (PTT) has enabled to monitor the beat-to-beat BP, identifying a strong relationship between the severity of SDB and the extent to very short-term BP variability. Here, we investigated the effects of continuous positive airway pressure (CPAP) on very short-term BP variability. Methods: We studied 57 patients (mean age 61 years old, male 42) with SDB who underwent the full polysomnography on two consecutive days for diagnosis (baseline) and CPAP. PTT was continuously monitored together, and PTT-based BP values were measured on a beat-to-beat basis. PTT index was defined as the average number of acute transient rises in BP (≥12 mmHg) within 30 seconds per hour. Results: Apnea-hypopnea index (AHI) was decreased from 46.5±22.4 to 13.7±15.0 (P<0.01) by CPAP. CPAP significantly lowered the average value of systolic PTT-based BP from 121±21 to 118±20 mmHg (P=0.04). Importantly, CPAP significantly reduced the PTT index from 31.4±20.1 to 20.8±15.6 (P<0.01) as well as the standard deviation (SD) of systolic PTT-BP from 5.3±1.9 to 4.9±1.4 mmHg (P=0.01), suggesting that very short-term BP variability was improved by CPAP ( Figure ). The changes in PTT index after CPAP were significantly correlated with the improvement in AHI (R=0.55), oxygen desaturation index (R=0.36), minimal SpO 2 (R=0.48), mean SpO 2 (R=0.46), and arousal index (R=0.58). In multivariate linear regression analysis, the change in AHI was the independent factor to determine the reduction of the PTT index after CPAP. Conclusion: PTT-based BP discovered the improvement in very short-term BP variability associated with SDB events by CPAP therapy.

Clinical impact of sleep-disordered breathing on very short-term blood pressure variability determined by pulse transit time.

Sleep-disordered breathing (SDB) and blood pressure variability (BPV) are strongly associated with cardiovascular diseases. Recently, pulse transit time (PTT) has enabled the monitoring of beat-to-beat BP; however, little is known about its clinical utility. The present study aimed to clarify the impact of SDB on very short-term BPV determined by PTT-based BP monitoring (PTT-BP). We analyzed 242 patients with suspected SDB. PTT-BP was continuously recorded overnight together with a portable sleep monitor. PTT index was defined as the average number of transient rises in PTT-BP (≥12 mmHg) within 30 s/h. We compared PTT-BP values with each SDB parameter, and examined the association between BPV and subclinical organ damage. Standard deviation (SD) of systolic, mean or diastolic PTT-BP, which indicates very short-term BPV, was significantly correlated with apnea--hypopnea index (AHI) and oxygen desaturation index (ODI). PTT index was positively associated with AHI, ODI, and minimal SpO2. Regression analyses showed that AHI and ODI were significant variables to determine systolic, mean, or diastolic PTT-BP SD and PTT index. Logistic regression analyses demonstrated that diastolic PTT-BP SD significantly influenced the presence of chronic kidney disease and left ventricular hypertrophy. SDB severity was closely associated with very short-term BP variability, and diastolic PTT-BP SD might be an important factor linked to subclinical organ damage. PTT-BP measurement may be useful to evaluate very short-term BPV during the night.

Pulse transit time in pregnancy: a new way to diagnose and classify sleep disordered breathing?

There are significant discrepancies between the prevalence of snoring and that of objectively defined sleep disordered breathing among pregnant women, suggesting subtle airflow limitations that may not be captured by conventional scoring. This study examined the performance of pulse transit time, an indirect measure of arterial stiffness and sympathetic activation, in pregnancy. Pregnant women with obesity and snoring and a group of controls without symptoms of sleep disordered breathing were recruited in the first trimester. Women underwent a level III in-laboratory sleep monitoring study including an electrocardiogram and pulse oximetry, and pulse transit time was measured. Sleep disordered breathing was defined as an apnea-hypopnea index at least five events per hour of sleep. Statistical analysis was performed using Spearman correlation, Fisher's exact t-test, and univariate analysis. Of the 222 women, 38 met criteria for sleep disordered breathing. Pulse transit time drops were very prevalent (95% of participants with snoring had > 5 drops per hour). Median apnea-hypopnea index was 0.7 (interquartile range [IQR]: 2.6) events per hour whereas median pulse transit time drop index was 20.70 (IQR: 35.90) events per hour. Pulse transit time index was significantly higher in snorers with apnea-hypopnea index less than five events per hours and participants with apnea-hypopnea index greater than five events per hour compared to controls. Examination of random epochs with pulse transit time drops showed that 95% of pulse transit time drops were associated with airflow limitation. Pulse transit time ascertains frequent events of sympathetic activation in at-risk women with and without sleep disordered breathing beyond conventional apneas and hypopneas. Pulse transit time may be an important addition to the identification of clinically significant sleep disordered breathing in pregnant women, and may identify more sleep disordered breathing than apnea-hypopnea index.

Nonlinear Cuffless Blood Pressure Estimation of Healthy Subjects Using Pulse Transit Time and Arrival Time

This paper presents a novel blood pressure (BP) estimation method based on pulse transit time (PTT) and pulse arrival time (PAT) to estimate the systolic BP (SBP) and the diastolic BP (DBP). A data acquisition hardware is designed for high-resolution sampling of phonocardiogram (PCG), photoplethysmogram, and electrocardiogram (ECG). PCG and ECG perform as the proximal timing reference to obtain PTT and PAT indices, respectively. In order to derive a BP estimator model, a calibration procedure, including a supervised physical exercise, is conducted for each individual, which causes changes in their BP, and then, a number of reference BPs are measured alongside the acquisition of the signals per subject. It is suggested to use a force-sensing resistor that is placed under the cuff of the BP reference device to mark the exact moments of reference BP measurements, which are corresponding to the inflation of the cuff. Additionally, a novel BP estimator nonlinear model, based on the theory of elastic tubes, is introduced to estimate the BP using PTT/PAT values precisely. The proposed method is evaluated on 32 subjects. Using the PTT index, the correlation coefficients for SBP and DBP estimation are 0.89 and 0.84, respectively. Using the PAT index, the correlation coefficients for SBP and DBP estimation are 0.95 and 0.84, respectively. The results show that the proposed method, exploiting the introduced nonlinear model with the use of PAT index or PTT index, provides a reliable estimation of SBP and DBP.

Evaluation of main arteries rigidity indices according to the data of bifunctional 24-hour BP and ECG monitoring with the BPLab® device

Presented are the results of research of one of the main arteries rigidity index - pulse transit time (PTT) acquired at the processing of 24-hour monitoring data obtained by the portable recorder BPLab®. The work shows correlation of PTT index and BP in 24-hour dynamics. It demonstrates stable correlation of PTT value with other arteries rigidity indices taken by stationary equipment(VS-1000, Fukuda).