Arterial Waveform Analysis Research Articles

A Comparison of Third-Generation Semi-Invasive Arterial Waveform Analysis with Thermodilution in Patients Undergoing Coronary Surgery

Uncalibrated semi-invasive continous monitoring of cardiac index (CI) has recently gained increasing interest. The aim of the present study was to compare the accuracy of CI determination based on arterial waveform analysis with transpulmonary thermodilution. Fifty patients scheduled for elective coronary surgery were studied after induction of anaesthesia and before and after cardiopulmonary bypass (CPB), respectively. Each patient was monitored with a central venous line, the PiCCO system, and the FloTrac/Vigileo-system. Measurements included CI derived by transpulmonary thermodilution and uncalibrated semi-invasive pulse contour analysis. Percentage changes of CI were calculated. There was a moderate, but significant correlation between pulse contour CI and thermodilution CI both before (r 2 = 0.72, P < 0.0001) and after (r 2 = 0.62, P < 0.0001) CPB, with a percentage error of 31% and 25%, respectively. Changes in pulse contour CI showed a significant correlation with changes in thermodilution CI both before (r 2 = 0.52, P < 0.0001) and after (r 2 = 0.67, P < 0.0001) CPB. Our findings demonstrated that uncalibrated semi-invasive monitoring system was able to reliably measure CI compared with transpulmonary thermodilution in patients undergoing elective coronary surgery. Furthermore, the semi-invasive monitoring device was able to track haemodynamic changes and trends.

Automatic detection of pulse morphology patterns &amp;amp; cardiac risks

Analysis of arterial pulse waveforms is important for non-invasive diagnosis of cardiovascular functions. Large samples of IPG signal records of radial arterial pulse show presence of eight different types of shapes (morphological patterns) in the pulse waveforms. In this paper we present an efficient computational method for automatic identification of these morphological patterns. Our algorithm uses likelihood ratio of cumulative periodogram of pulse signals and some geometrical criteria. The algorithm is presented with necessary details on signal processing aspects. Results for a large sample of pulse records of adult Indian subjects show high accuracy of our algorithm in detecting pulse-morphology patterns. Variation of pulse-morphology with respect to time is also analyzed using this algorithm. We have identified some characteristic features of pulse-morphology variation in patients of certain cardiac problems, hypertension, and diabetes. These are found relevant and significant in terms of physiological interpretation of the associated shapes of pulse waveforms. Importance of these findings is highlighted along with discussion on overall scope of our study in automatic analysis of heart rate variability and in other applications for non-invasive prognosis/diagnosis.

Karotid-Femoral (Aortik) Nabız Dalga Hızı ve Paraoksonaz 1 Aktivitesi

Measurement of arterial pulse wave velocity is a good technique in which large artery elasticity is assessed from analysis of the peripheral arterial waveform. Pulse wave velocity is an index of arterial stiffness and a surrogate marker for atherosclerosis. It is inversely correlated with arterial elasticity and relative arterial compliance. The carotid-femoral (aortic) pulse wave velocity predicts cardiovascular morbidity and mortality in high risk patients with hypertension and hemodialysis. Aortic distensibility is reduced in the presence of coronary artery disease and left ventricular hypertrophy. A 1 m/s of increase in aortic pulse wave velocity increases risk of cardiovascular events approximately 39%. Serum lipids and lipoproteins such as oxidized low-density lipoprotein and paraoxonase 1 are important in atherosclerotic disease. Paraoxonase 1 is synthesized primarily in the liver and is secreted into the plasma, where it is closely associated with high density lipoproteins. Paraoxonase 1 prevents the formation of oxidized low density lipoprotein and it protects phospholipids in high density lipoprotein that has a potential cardio-protective function from oxidation. The association of paraoxonase 1 with pulse wave velocity is controversial. According to current data, there are a few studies in connection with activity of paraoxonase 1 and pulse wave velocity in the literature. Therefore, this connection was assessed in this review manuscript.

Cardiac function at term in human pregnancy

ObjectivesWe have previously demonstrated deterioration in cardiac function at term in human pregnancy. To explore further, we investigated central arterial hemodynamics and association with maternal weight during gestation. Study designPrimiparous women (n=32) were recruited in a tertiary referral obstetric hospital and a longitudinal cohort study with analyses at median 16 and 37weeks gestation undertaken. Subgroups of normal body mass index, <25kg/m2, and overweight, ⩾25kg/m2, at 16weeks were created. Main outcome measuresWe performed 2D speckle tracking echocardiography strain analysis and tonometric measures of central arterial pressures, waveforms and pulse wave velocity. ResultsA reduction in cardiac strain (2P=0.002) from 16 to 37weeks gestation was associated with increased systemic vascular resistance (2P=0.008), reduced arterial compliance (2P=0.004) and increased central arterial pressures (2P<0.001) and augmentation index (2P=0.001). ConclusionsBy 37weeks, compared with values in earlier pregnancy, overweight women had higher systemic vascular resistance (2P<0.05). Additionally, their central diastolic pressure was higher (2P<0.05) and their ventricular strain was lower (2P<0.05) than in normal weight pregnant women. An increase in systemic vascular resistance and central arterial pressures by term may contribute to the observed deterioration in cardiac function. This appears more prominent in overweight women.

Thinking Beyond Traditional Cardiovascular Risk Factors

In this issue of Angiology, Ticulescu et al assess the role of arterial stiffness in relation to established risk factors in predicting cardiovascular (CV) remodeling. They assessed left ventricular mass index (LVMi) and carotid intima media thickness (IMT) in patients with moderate renal impairment. Outpatients with stage III chronic kidney disease ([CKD] n 1⁄4 89) and with stage II CKD (n 1⁄4 52) underwent echocardiographic and supra-aortic trunk scanning; carotid IMT was measured 1 cm beneath the carotid bifurcation, whereas arterial stiffness was assessed at the right carotid as the b index. As Ticulescu et al point out, this echotracking estimation of arterial stiffness represents a useful and feasible technique that allows the evaluation of both heart and vessels during one examination. The 2 groups were similar for established CV risk factors (ie, age, gender, hypertension, hypercholesterolemia, diabetes mellitus [DM], and smoking) and relevant drug treatment. No significant differences were found in terms of blood pressure, biochemical parameters (except for creatinine clearance), IMT, LVMi, and presence of carotid plaques. After multivariate analysis, the b index of arterial stiffness was an independent predictor of IMT (along with age, DM, and hypercholesterolemia) in patients with stage III CKD; the most powerful predictor was DM, followed by age, b index, and hypercholesterolemia. In the stage II CKD group, DM was the only independent predictor of IMT. As discussed by Ticulescu et al, this finding could reflect the functional effect of arterial wall remodeling at different stages of CKD; the intimal layer plays a main role in atherogenesis during earlier stages of CKD, whereas in more advanced CKD, the atherosclerotic process mainly involves the medial layer. Chronic kidney disease is recognized as a CV risk factor, and these patients should be treated accordingly. On the other hand, arterial stiffness, regulated by numerous factors, such as mean arterial pressure, structural alterations of the arterial wall, endothelial dysfunction, and inflammation, may accelerate the atherosclerotic process. There are several different noninvasive methods for the assessment of arterial stiffness including pulse wave velocity (PWV), relating change in vessel diameter (or area) to distending pressure, arterial pulse waveform analysis, ambulatory arterial stiffness index, augmentation index, and b index; PWV is the most recognized and established index of arterial stiffness. Arterial stiffness and CKD are closely linked by shared risk factors and associated increased CV mortality. In a cohort of hemodialysis patients, both carotid IMT and b index of arterial stiffness were independently predictive of CV mortality even after adjustment for other relevant covariates, implicating the distinct roles of stiffness and thickness of arterial wall in the pathogenesis of CV disease. Furthermore, arterial stiffness assessed by aortofemoral PWV was the only arterial index (among carotid IMT, systemic arterial compliance, and carotid-derived augmentation index) independently associated with CV outcome in patients with stages IV and V CKD. It should be noted that arterial stiffness is a predictor for CV events not only in renal patients but also in the general population, in patients with hypertension, impaired glucose intolerance, and coronary artery disease. Furthermore, a recent meta-analysis showed that aortic PWV was a strong predictor of CV events and all-cause mortality in 15 877 individuals; the higher the baseline CV risk, the higher the predictive ability of arterial stiffness. Interestingly, aortic PWV was a stronger independent predictor (r 1⁄4 .48; P 1⁄4 .002) of a 25% decline in renal function or initiation of renal replacement therapy compared with systolic blood pressure (r 1⁄4 .17; P 1⁄4 .039) and urine-proteinto-creatinine ratio (r 1⁄4 .20; P 1⁄4 .021) in patients with stages III and IV CKD.

Arterial waveform analysis in anesthesia and critical care

In this review, we describe the basic principles of arterial waveform analysis (AWA) to assess cardiac output (CO) and cardiac preload. The validity of commercially based hemodynamic monitoring systems is discussed, together with their clinical applications and limitations. Currently, three devices (the FloTrac system, PiCCO monitor, and LiDCO system) are available for measurement of AWA-based CO. In addition, dynamic preload parameters such as stroke volume variation (SVV) and pulse pressure variation (PPV) are determined, which may be useful to predict fluid responsiveness in mechanically ventilated patients. AWA provides a less invasive and easy-to-use alternative for CO measurement. The validity of AWA devices has been verified in a variety of patients and circumstances, but their performance is compromised in the presence of hemodynamic instability, cardiac arrhythmias, or other factors disturbing the arterial pressure waveform. The definitive role of dynamic preload parameters like SVV and PPV is a matter of research. Large trials in which the value of early goal-directed therapy using this technology is studied in relation to outcome are urgently needed.

Got PAD? Hidden dangers revealed with ABI

Peripheral artery disease (PAD), a result of atherosclerotic vascular changes to the endothelial lining of blood vessels, affects 8-12 million Americans and increases the risk of mortality as much as 50% from heart attacks and strokes. Early diagnosis and treatment of PAD along with early risk-reduction strategies have the potential to decrease societal health costs, as well as morbidity and mortality. PAD through screening with ankle brachial index (ABI), versus relying on existing physical exam and screening questionnaires, can increase the number of participants correctly diagnosed with PAD and lead to earlier treatment options. ABI screening was implemented in a primary care practice setting; outcomes were compared with historical rates and outcomes for participants at risk who declined ABI. Authors concluded that the participants who had ABI screenings that included arterial waveform analysis had a 78% rate of PAD diagnosis, whereas only 13% of the participants who did not elect ABI screening were diagnosed with PAD based on their symptoms and physical exam. Use of ABI screening led to increased frequency and awareness of PAD diagnosis and the opportunity for early intervention.

Arterial Waveform Analysis for the Anesthesiologist

Qualitative arterial waveform analysis has been in existence for millennia; quantitative arterial waveform analysis techniques, which can be traced back to Euler's work in the 18th century, have not been widely used by anesthesiologists and other clinicians. This is likely attributable, in part, to the widespread use of the sphygmomanometer, which allows the practitioner to assess arterial blood pressure without having to develop a sense for the higher-order characteristics of the arterial waveform. The 20-year delay in the development of devices that measure these traits is a testament to the primitiveness of our appreciation for this information. The shape of the peripheral arterial pressure waveform may indeed contain information useful to the anesthesiologist and intensivist. The maximal slope of the peripheral arterial pressure tracing seems to be related to left ventricular contractility, although the relationship may be confounded by other hemodynamic variables. The area under the peripheral arterial pressure tracing is related to stroke volume when loading conditions are stable; this finding has been used in the development of several continuous cardiac output monitors. Pulse wave velocity may be related to vascular impedance and could potentially improve the accuracy of waveform-based stroke volume estimates. Estimates of central arterial pressures (e.g., aortic) can be produced from peripheral (e.g., brachial, radial) tracings using a Generalized Transfer Function, and are incorporated into the algorithms of several continuous cardiac output monitors.

Improved pulse transit time estimation by system identification analysis of proximal and distal arterial waveforms

We investigated the system identification approach for potentially improved estimation of pulse transit time (PTT), a popular arterial stiffness marker. In this approach, proximal and distal arterial waveforms are measured and respectively regarded as the input and output of a system. Next, the system impulse response is identified from all samples of the measured input and output. Finally, the time delay of the impulse response is detected as the PTT estimate. Unlike conventional foot-to-foot detection techniques, this approach is designed to provide an artifact robust estimate of the true PTT in the absence of wave reflection. The approach is also applicable to arbitrary types of arterial waveforms. We specifically applied a parametric system identification technique to noninvasive impedance cardiography (ICG) and peripheral arterial blood pressure waveforms from 15 humans subjected to lower-body negative pressure. We assessed the technique through the correlation coefficient (r) between its 1/PTT estimates and measured diastolic pressure (DP) per subject and the root mean squared error (RMSE) of the DP predicted from these estimates and measured DP. The technique achieved average r and RMSE values of 0.81 ± 0.16 and 4.3 ± 1.3 mmHg. For comparison, the corresponding values were 0.59 ± 0.37 (P < 0.05) and 5.9 ± 2.5 (P < 0.01) mmHg for the conventional technique applied to the same waveforms and 0.28 ± 0.40 (P < 0.001) and 7.2 ± 1.8 (P < 0.001) mmHg for the conventional technique with the ECG waveform substituted for the ICG waveform. These results demonstrate, perhaps for the first time, that the system identification approach can indeed improve PTT estimation.

Comparison of cardiac output measurements by thermodilution and arterial pulse waveform analysis (Flo Trac/Vigileo ®) in morbid obese patients

s and Programme: EUROANAESTHESIA 2011: The European Anaesthesiology Congress: Monitoring: Equipment and Computers

Noninvasive measurement of cardiac output by uncalibrated finger arterial waveform analysis

s and Programme: EUROANAESTHESIA 2011: The European Anaesthesiology Congress: Monitoring: Equipment and Computers

Arterial Stiffness, Submaximal Heart Rate and Predicted Cardiovascular Fitness in College-Aged Mexican-American Males

Increased arterial stiffness is a known predictor for cardiovascular disease. One population that is at a known greater risk for increased arterial stiffness is the Hispanic population. Additionally, little is reported on the association of heart rate response during and after submaximal exercise on individuals classified with borderline large artery elasticity (LAE). PURPOSE: The purpose of this study was to examine the differences in heart rate during a submaximal exercise test between individuals who have normal arterial stiffness and individuals who have borderline arterial stiffness within a Mexican-American (MA) college-aged population. METHODS: Arterial waveform was measured on 45 college-aged (24.07, +6.7) MA males. Standardized protocols for arterial waveform analysis were followed. Participants were also measured for height, weight, BMI, body fat, and blood pressure. Immediately following the arterial stiffness measurement each participant was asked to perform a three-minute submaximal cardiovascular step test (Queen's College Step Test [QCST]). Heart rate (HR) was recorded at the beginning of the test and at each ten second interval during the test and for two minutes post exercise to examine heart rate recovery (HRr). RESULTS: The results indicate 22 participants had normal LAE (17.52 ml/mmHg × 10 +2.58) and 23 with borderline LAE arterial elasticity (12.82 ml/mmHg × 10 +1.91). ANOVA results show no significant differences between the groups in height, weight, BMI, body fat, or initial QCST HR. Analysis of variance revealed significant HR differences (p<0.05) between LAE normal and borderline groups during the QCST at each ten second interval. The ANOVA also revealed HR differences during HRr at 10s, 20s, and 30s post exercise. Predicted VO2 for the normal LAE group (47.19 ml/kg/min +6.48) and borderline LAE group (42.44 ml/kg/min +6.08) was significantly different (p<0.05). CONCLUSIONS: The majority of the MA males in this sample are diagnosed with borderline LAE. The results indicate that although the two groups show a predicted healthy VO2, there are underlying arterial mechanisms attributed to arterial stiffness exhibited during submaximal exercise that may already be indicative of cardiovascular disease that a submaximal field test may not reveal.

Blood pressure regulation during the aging process: the end of the ‘hypertension era’?

The elderly blood pressure paradigm reflects all of the demographic, technological and therapeutic changes over the past 20-30 years that make it now possible to propose a more integrative approach of 'hypertension'. The aim of the present review was to address what does measured blood pressure really mean and what are its determinants during the aging process. We show that standard blood pressure measurements are not adequate or even misleading for the evaluation of cardiovascular risk especially in the elderly patients and that there is a necessity of a transition to a new approach in determining the arterial risk. Direct arterial measurements including analysis of central and peripheral arterial waveforms and assessment of pulse wave velocity can be reliable and easily performed measurements as an alternative to blood pressure-Korotkoff approach. For these measurements, there are currently sufficient clinical data showing their association with cardiovascular risk. There is also the emergence of reference values and beneficial elements of regression by treatment. This new approach as well as recent knowledge on vascular hemodynamics and biology, represent the swan song for the hypertension concept as defined by blood pressure values.

Arterial and Plethysmographic Waveform Analysis in Anesthetized Patients With Hypovolemia

Survey of Anesthesiology: April 2011 - Volume 55 - Issue 2 - p 102-104 doi: 10.1097/01.SA.0000394317.81799.38

Pre- and Postprocedure Duplex Evaluation of Distal Revascularization-Interval Ligation Procedure: A Case Study

Introduction Duplex ultrasound is a valuable modality for the assessment of hemodialysis access function. A potential complication of hemodialysis access is arterial steal, which occurs when venous outflow exceeds the capacity of the inflow artery, and flow in this distal artery becomes retrograde, stealing blood flow from the hand to the fistula site. A potential condition resulting from arterial steal is hand or digit ischemia. Distal revascularization-interval ligation (DRIL) procedures can be used to “bypass” the fistula or graft site and deliver blood to the hypoperfused hand. Presented is a case of an arterial steal with severe hand ischemia that was alleviated by a DRIL procedure. Case Study A 69-year-old woman presented to the vascular laboratory with an ischemic right hand and digital ulcer distal to a brachial-axillary arteriovenous graft (AVG). Duplex ultrasound was performed of the right upper-extremity inflow arteries, AVG, and outflow veins. Ipsilateral brachial, radial, and ulnar artery waveform analysis for direction of flow was performed with and without AVG compression. The evaluation revealed significant arterial ischemia that returned to normal after manual compression of the AVG. The patient underwent a DRIL procedure after the pre-op duplex evaluation. Postprocedural duplex evaluation revealed patent inflow and outflow vessels, patent graft, and bypass (DRIL) with antegrade flow in the brachial and radial arteries and no change of flow with manual graft compression; clinically, the patient had a healing ulceration of the digit. Conclusion Duplex ultrasound for hemodialysis access should not only be used to evaluate for patency of the fistula or graft but should include assessment for ischemia and/or steal. This case demonstrates the importance of the assessment of the distal arterial segments including digital waveforms, and the use of manual compression to complete the hemodialysis access evaluation. DRIL procedures can potentially correct arterial steal while preserving access function.

Clinical utility of quantitative magnetic resonance angiography in the assessment of the underlying pathophysiology in a variety of cerebrovascular disorders

Quantitative MRA (qMRA) is a relatively new technique that uses traditional time-of-flight and phase-contrast MRI to visualize extracranial and intracranial vascular anatomy and measure volumetric blood flow. We aimed to assess the clinical utility of qMRA in assessing the hypothesized pathophysiology (HP) in a range of cerebrovascular diseases. Moreover, we postulated that evaluation of the arterial waveforms, can improve the evaluation of the hypothesized pathophysiology by qMRA. We reviewed studies from 10 patients who underwent qMRA examinations before and after their treatments. Two reviewers assessed the anatomy, volumetric flow rates and arterial waveforms for each vessel sampled and reached a consensus as to whether the above parameters supported the clinical diagnosis/hypothesized pathophysiology and the subsequent management. All 20 qMRA studies were technically adequate. qMRA supported the HP in all 10 patients as determined by abnormal volumetric flow values in the affected vessels before treatment and by the correction of these abnormal values in the patients whose treatment was successful. Each of our five patients with occlusive disease/vasoconstriction demonstrated evidence of dampening of the arterial waveforms distally to the narrowed artery (parvus-tardus phenomenon). The parvus-tardus effect disappeared after treatment. qMRA is unique in combining time-of-flight MRA in a complementary manner with phase-contrast MRA to obtain volumetric flow values and potentially important physiologic information from arterial waveform analysis in patients with a range of cerebrovascular diseases during the course of a single MR examination.

Examination of the fetal cardiovascular system

Doppler evaluation of the placenta and fetal cardiovascular system is one of the primary surveillance tools in prenatal medicine. By assessing uterine and umbilical arteries, placental development can be documented. This is useful for the prediction of hypertensive maternal disorders and placental dysfunction and fetal growth failure. The umbilical artery flow velocity waveform provides an estimate of villous vascular occlusion in the fetal compartment of the placenta. Middle cerebral artery Doppler is important in studying fetal responses to abnormal oxygenation and fetal anemia. Precordial venous Doppler gives insight into the cardiac effects of many conditions such as fetal growth restriction, twin-twin transfusion syndrome and fetal arrhythmia. Further quantification of these effects requires cardiac Doppler to quantify diastolic and systolic function as well as global myocardial performance. This article reviews important characteristics of arterial and venous Doppler waveform analysis, individual vascular beds and their clinical application in fetal evaluation.

Cardiac Output Determination by Thermodilution, Arterial Pulse Waveform Analysis and Korotkoff Sounds Analysis in Cardiac Catheterization Patients

Cardiac Output Determination by Thermodilution, Arterial Pulse Waveform Analysis and Korotkoff Sounds Analysis in Cardiac Catheterization Patients

Comparison of Cardiac Output Measurement by Arterial Waveform Analysis and Pulmonary Artery Catheter in Mitral Stenosis

Comparison of Cardiac Output Measurement by Arterial Waveform Analysis and Pulmonary Artery Catheter in Mitral Stenosis

Arterial and Plethysmographic Waveform Analysis in Anesthetized Patients with Hypovolemia

Respiratory-induced arterial and plethysmographic (pulse oximetry) waveform changes were shown to be good predictors of cardiac output response to increased preload. The aim of this study was to evaluate the reliability of arterial and plethysmographic waveform variables in patients with mild hypovolemia. Patients undergoing autologous hemodilution were studied. After anesthesia induction, hemodilution was performed by withdrawing blood in steps of 2% of estimated circulating blood volume (ECBV), up to 20%. The patients who did not develop hypotension (systolic blood pressure < 80 mmHg) were studied. Arterial and plethysmographic waveforms were recorded and analyzed off-line at baseline and after each withdrawal of blood. Variations in arterial systolic and pulse pressure were analyzed using standard methods. Plethysmographic waveform variation and delta pulse oximetry plethysmography were determined by using pulse oximetry recordings. There were 33 study participants. Systolic blood pressure decreased by 11%, and heart rate increased from 73 to 76 beats/min after a 20% reduction of ECBV. Systolic pressure and pulse pressure variations increased (P < 0.005) after a 4% reduction of ECBV. The values of arterial pressure and pulse oximetry waveform variables almost doubled in value after a 20% reduction of ECBV. Systolic pressure variation was the most reliable variable during hypovolemia. Plethysmographic waveform variation increased significantly after a 6% reduction of ECBV and delta pulse oximetry plethysmography after an 8% reduction of ECBV. Arterial and pulse oximetry respiratory-induced changes in waveform variables are reliable indicators of mild hypovolemia in anesthetized patients. The pulse oximetry plethysmographic waveforms accurately reflect arterial waveforms during more progressive hypovolemia.