Central Waveform Research Articles

Association of Haemodynamic Indices of Central and Peripheral Pressure with Subclinical Target Organ Damage

Background: Central aortic pressure has often been shown to be more closely associated with markers of vascular function and incidence of cardiovascular events compared to peripheral pressure. However, the potential clinical use of central aortic or peripheral haemodynamic indices as markers of target organ damage (TOD) has not been fully established. Methods: We evaluated associations of TOD with central aortic and peripheral haemodynamic indices (central aortic [cPP] and peripheral pulse pressure [pPP], central aortic augmentation index, and central and peripheral waveform factor) in 770 hospital inpatients (age 60 ± 10 years, 473 males) with primary hypertension. TOD was quantified in terms of arterial stiffness as measured by carotid-femoral pulse wave velocity (cfPWV), carotid intima-media thickness (IMT), and urine albumin-to-creatinine ratio (ACR). Subclinical TOD was defined as carotid IMT >0.9 mm, urine ACR >3.5 mg/mmol in females and >2.5 mg/mmol in males and/or cfPWV >12 m/s. Results: Both cPP and pPP showed significant correlation with cfPWV (r = 0.41 vs. 0.40; p < 0.01), ACR (r = 0.24 vs. 0.27; p < 0.01) and carotid IMT (r = 0.14 vs. 0.15; p < 0.01). Each SD increase in pPP and cPP was associated with increased risk of cfPWV >12 m/s (odds ratio [OR] = 2.7 and 2.9 for pPP and cPP, respectively), ACR >2.5 mg/mmol (OR = 1.2 and 1.4, respectively), and carotid IMT >0.9 mm (OR = 1.46 and 1.53, respectively). Compared to pPP, cPP had higher predictive power for TOD for age ≥60 years (OR = 3.07, p < 0.001). Conclusions: Although both pPP and cPP show an association with TOD in a hypertensive population, cPP provides additional information beyond pPP associated with TOD in a hypertensive cohort. Central aortic haemodynamic indices as potential biomarkers of subclinical TOD need to be validated by further prospective studies.

Usefulness of the maximum rate of pressure rise in the central and peripheral arteries after weaning from cardiopulmonary bypass in pediatric congenital heart surgery: A retrospective analysis.

The maximum rate of pressure rise (dP/dtmax) in radial artery has been proposed as a noninvasive surrogate of aortic dp/dtmax, reflecting left ventricular (LV) contractility in children. The aim of this study was to investigate relationship between aortic and radial dp/dtmax at weaning from cardiopulmonary bypass (CPB) and usefulness of these indices for estimating postoperative outcomes in pediatric congenital heart surgery.Aortic and radial arterial pressure waveforms were analyzed simultaneously during weaning from CPB in 29 congenital heart surgery. The maximum first derivatives of aortic and radial arterial waveforms were calculated and averaged from 3 consecutive respiratory cycles. We obtained the maximum vasoactive inotropic score during the first 36 postoperative hours, LV ejection fraction, and fractional shortening on transthoracic echocardiography performed within postoperative day 7.A significant difference between aortic and radial dP/dtmax was observed (mean difference 356 mm Hg/s, 44% of averages), and radial dP/dtmax was weakly correlated with aortic dP/dtmax (r =0.373, P = 0.047). Aortic dP/dtmax was significantly associated with the maximum vasoactive inotropic score (P < 0.001), postoperative LV ejection fraction (P = 0.018), and fractional shortening (P = 0.015); however, radial dP/dtmax was not. On Receiver operating characteristic analysis, aortic dP/dtmax had a greater area under the curve than radial dP/dtmax in predicting higher vasoactive inotropic score (0.827 vs 0.673).Immediately after CPB in pediatric congenital heart surgery, radial dP/dtmax may not replace aortic dP/dtmax because of a discrepancy between central and peripheral arterial waveforms. In this critical period, aortic dP/dtmax can be useful to estimate postoperative ventricular function rather than peripherally derived dP/dtmax.

Central Hemodynamics and Arterial Stiffness in Systemic Sclerosis.

Although microvascular disease is a hallmark of systemic sclerosis (SSc), a higher prevalence of macrovascular disease and a poorer related prognosis have been reported in SSc than in the general population. The simultaneous assessment of prognostically relevant functional properties of larger and smaller arteries, and their effects on central hemodynamics, has never been performed in SSc using the state-of-the-art techniques. Thirty-four women with SSc (aged 61±15 years, disease duration 17±12 years, and blood pressure 123/70±18/11 mm Hg) and 34 healthy women individually matched by age and mean arterial pressure underwent the determination of carotid-femoral (aortic) and carotid-radial (upper limb) pulse wave velocity (a direct measure of arterial stiffness), aortic augmentation (a measure of the contribution of reflected wave to central pulse pressure), and aortobrachial pulse pressure amplification (brachial/aortic pulse pressure) through applanation tonometry (SphygmoCor). Patients and controls did not differ by carotid-femoral or carotid-radial pulse wave velocity. Aortic augmentation index corrected for a heart rate of 75 bpm (AIx@75) was higher in women with SSc (30.9±16% versus 22.2±12%; P=0.012). Patients also had a lower aortobrachial amplification of pulse pressure (1.22±0.18 versus 1.33±0.25; P=0.041). SSc was an independent predictor of AIx@75 (direct) and pulse pressure amplification (inverse). Among patients, age, mean arterial pressure, and C-reactive protein independently predicted carotid-femoral pulse wave velocity. Age and mean arterial pressure were the only predictors of AIx@75. Women with SSc have increased aortic augmentation and decreased pulse pressure amplification (both measures of the contribution of reflected wave to central waveform) but no changes in aortic or upper limb arterial stiffness. Microvascular involvement occurs earlier than large artery stiffening in SSc.

A Simple Adaptive Transfer Function for Deriving the Central Blood Pressure Waveform from a Radial Blood Pressure Waveform.

Generalized transfer functions (GTFs) are available to compute the more relevant central blood pressure (BP) waveform from a more easily measured radial BP waveform. However, GTFs are population averages and therefore may not adapt to variations in pulse pressure (PP) amplification (ratio of radial to central PP). A simple adaptive transfer function (ATF) was developed. First, the transfer function is defined in terms of the wave travel time and reflection coefficient parameters of an arterial model. Then, the parameters are estimated from the radial BP waveform by exploiting the observation that central BP waveforms exhibit exponential diastolic decays. The ATF was assessed using the original data that helped popularize the GTF. These data included radial BP waveforms and invasive reference central BP waveforms from cardiac catheterization patients. The data were divided into low, middle, and high PP amplification groups. The ATF estimated central BP with greater accuracy than GTFs in the low PP amplification group (e.g., central systolic BP and PP root-mean-square-errors of 3.3 and 4.2 mm Hg versus 6.2 and 7.1 mm Hg; p ≤ 0.05) while showing similar accuracy in the higher PP amplification groups. The ATF may permit more accurate, non-invasive central BP monitoring in elderly and hypertensive patients.

Blood Pressure And Wave Separation Analysis

BACKGROUND: Individuals with Down syndrome (DS) have altered autonomic function, which is related to low blood pressure (BP). Properties of the pressure waveform are important contributors to overall blood pressure responses and regulation. Using lower body negative pressure (LBNP) to stimulate the autonomic nervous system can provide important information on how BP is regulated in persons with DS. PURPOSE: To determine if central BP and waveform separation analyses are different between individuals with and without DS, at rest and during LBNP stimulation. METHODS: Individuals with (n=10; 34 yrs; 32.3 kg/m2) and without DS (n=11; 24 yrs; 22.9 kg/m2) were evaluated at baseline and during LBNP after 5 minutes at -20mmHg. Radial applanation tonometry measured the pressure waveforms, and specialized software determined the forward (FP) and reflected pulse height (RP), as well as aortic systolic and diastolic BP (aorSBP, aorDBP), and augmentation index (AIx and AIx75). RESULTS: There were no group differences at baseline for the hemodynamic variables. AIx during LBNP decreased in the DS group, with no change in the control group (p<0.05). There were no interactions or group differences for FP, RP, aorSBP and aorDBP. CONCLUSION: The results suggest differences in BP control between DS and control subjects. The difference in AIx between groups may be due to the decreased RP in the DS group during LBNP. Activation of the sympathetic nervous system may have increased the RP, which is not depicted in the results in the DS individuals. This data corresponds with previous literature, indicating dysfunction of autonomic control of BP in DS. A limitation of this study may be the small number of subjects.

Inter-arm difference and orthostatic changes of brachial blood pressure in the very elderly patients under antihypertensive treatment

Background. Inter-arm difference in blood pressure (BP) and orthostatic BP response are significant prognostic factors in hypertensive patients, especially in the elderly ones. However, data on their prevalence, predictors and clinical associations remain contradictory. The aim of our study was to investigate inter-arm difference and orthostatic response and to establish their clinical associations in the very elderly hypertensive patients. Design and methods. We enrolled 67 hypertensive subjects older than 80 years (mean age 84,1 ± 3,1 years, 25,5 % male, mean clinic brachial systolic BP (SBP) 134,8 ± 23,2 mm Hg) in a cross-sectional study. Simultaneous bilateral brachial BP measurements were performed using oscillometric validated cuffbased device in sitting position and then 2 minutes after standing up. Central pulse waveform characteristics and arterial stiffness parameters were estimated by BPLab Vasotens system (Petr Telegin, Russia). Results. The median of inter-arm difference in SBP (IADSBP) was 4,00 (2,50, 9,00) mm Hg. IADSBP was ≥ 10 mm Hg in 25,4 % participants. Compared to others, those with IADSBP ≥ 10 mmHg had significantly higher body mass index (31,39 ± 5,73 vs 28,48 ± 4,1 kg/m2 , p < 0,05), waist circumference (116,3 ± 13,6 vs 107,7 ± 11,2 cm, p < 0,05) and pulse wave velocity in aorta (11,65 ± 1,46 vs 10,75 ± 1,71 m/s, p < 0,05). A positive correlation between IADSBP and augmentation index was revealed (r = 0,277, p < 0,05). Patients with asymptomatic orthostatic hypotension (22,4 % participants) had higher levels of brachial SBP and pulse pressure while central BP and markers of arterial stiffness did not differ from those without orthostatic hypotension. Conclusions. Significant IADSBP is associated with increased arterial stiffness and abdominal obesity in the very elderly hypertensive patients, whereas there is no evidence of interrelation between orthostatic response and arterial stiffness in these patients.

Central arterial pulse waveform acquisition with a portable pen-like optical fiber sensor.

Pulse waveform features related to cardiovascular pathologies and arterial stiffness have been extensively studied, and optical fiber sensors have been studied with an aim to simplify the pulse waveform acquisition in the carotid artery. In this paper, a novel optical fiber sensor to record pulse waveform in the carotid artery has been proposed. The pulse waveform optical fiber sensor design, based on fiber Bragg gratings, is presented. The probe was characterized, and its response to controlled waveforms was studied. Finally, tests were performed on human subjects. The developed sensor has a displacement sensitivity of 21.2 pm/μm, with ability to detect the carotid pulse wave in the neck surface, with a resolution of 1.3 mmHg. This study revealed a new technological approach for acquisition of the central pulse waveform.

Wavelet Analysis of Doppler Flow Velocity Waveforms from the Ocular Circulation Detects Abnormalities in Micro-vascular Function in Heart Failure

Aims: Many pathological processes may result in Heart Failure (HF), however, the final clinical phenotype appears to be common to all aetiologies. Microvascular abnormalities in HF have been demonstrated in a variety of vascular beds however the effect of HF on the retrobulbar circulation is not known. We employed a novel method of analysing blood flow velocity waveforms in order to quantify changes in the Doppler signal obtained from the retrobulbar arteries between HF patients and controls. FMD was also assessed. Methods and Results: 32 patients with systolic HF on maximal medical therapy and 10 age and sex-matched controls were studied. Doppler waveforms were obtained from the ophthalmic, central retinal and brachial artery in all subjects. Waveforms were analysed using a wavelet technique which expressed each waveform in constituent frequency bands, allowing direct comparisons to be made. Significant differences were found in ophthalmic and central retinal waveforms but not brachial waveforms between patients and controls. Flow mediated dilatation was also found to be abnormal in patients. Conclusion: This study suggests that abnormalities in microvascular function in the retrobulbar circulation are present in HF and that these changes can be detected by a novel wavelet analysis technique.

Association of serum-free fatty acid level with reduced reflection pressure wave magnitude and central blood pressure: the Nagahama study.

Central blood pressure (BP) has been suggested to be a better predictor of cardiovascular disease risk than brachial BP. Given that central BP and arterial waveform are both influenced by insulin resistance, major initiators of insulin resistance, such as serum-free fatty acid (FFA), are suspected of potentially being involved in central hemodynamics. To confirm that insulin signaling is an important modulator of central hemodynamics, we investigated this hypothesis in a large-scale general population. Brachial BP and radial arterial waveform were measured simultaneously in 9393 middle-aged to elderly individuals. The augmentation index was calculated from the radial waveform as the ratio of the height of the late systolic peak to that of the first peak. Central systolic BP was defined as the absolute pressure of the late systolic peak of the waveform. Differences in central and brachial pulse pressure (PP) were considered to represent PP amplification. PP amplification differed significantly among serum FFA level quartiles (Q1, 7.8±5.3; Q2, 8.6±5.0; Q3, 9.3±5.7; Q4, 10.3±6.1 mm Hg; P<0.001), and the maximum difference in combination with diabetes mellitus status was 4.9 mm Hg. Multivariate analysis adjusted for major covariates indicated that higher serum FFA was an independent determinant for higher PP amplification (β=0.145, P<0.001) and lower augmentation index (β=-0.122, P<0.001) and central systolic BP (β=-0.044, P<0.001), whereas the association between FFA and PP amplification significantly decreased (β=0.022, P<0.001) after further adjustment for augmentation index. Serum FFA is an overlooked factor favorably influencing central hemodynamics. A low-magnitude reflection pressure wave might be involved in this paradoxical relationship.

Aortic reservoir pressure corresponds to cyclic changes in aortic volume: physiological validation in humans.

Aortic reservoir pressure indices independently predict cardiovascular events and mortality. Despite this, there has never been a study in humans to determine whether the theoretical principles of the mathematically derived aortic reservoir pressure (RP(derived)) and excess pressure (XP(derived)) model have a real physiological basis. This study aimed to directly measure the aortic reservoir (AR(direct); by cyclic change in aortic volume) and determine its relationship with RP(derived), XP(derived), and aortic blood pressure (BP). Ascending aortic BP and Doppler flow velocity were recorded via intra-arterial wire in 10 men (aged 62 ± 12 years) during coronary artery bypass surgery. Simultaneous ascending aortic transesophageal echocardiography was used to measure AR(direct). Published mathematical formulae were used to determine RP(derived) and XP(derived). AR(direct) was strongly and linearly related to RP(derived) during systole (r=0.988; P<0.001) and diastole (r=0.985; P<0.001). Peak cross-correlation (r=0.98) occurred at a phase lag of 0.004 s into the cardiac cycle, suggesting close temporal agreement between waveforms. The relationship between aortic BP and AR(direct) was qualitatively similar to the cyclic relationship between aortic BP and RP(derived), with peak cross-correlations occurring at identical phase lags (AR(direct) versus aortic BP, r=0.96 at 0.06 s; RP(derived) versus aortic BP, r=0.98 at 0.06 s). RP(derived) is highly correlated with changes in proximal aortic volume, consistent with its physiological interpretation as corresponding to the instantaneous volume of blood stored in the aorta. Thus, aortic reservoir pressure should be considered in the interpretation of the central BP waveform.

Validation of Peripheral Pulse Wave Analysis Technique to Detect Aortic Valve State in Continuous-Flow LVADs1

Validation of Peripheral Pulse Wave Analysis Technique to Detect Aortic Valve State in Continuous-Flow LVADs1

Central pulse pressure amplification is associated with more extensive and severe coronary artery disease

Objectives. We investigate the association between noninvasively determined central pulse waveform characteristics and the extent and severity of coronary artery disease (CAD) in patients undergoing coronary angiography with the clinical diagnosis of CAD. Design. We included 145 consecutive patients with stable angina pectoris (SAP), unstable angina pectoris (USAP), or acute myocardial infarction (AMI) who were decided to undergo coronary angiography. Gensini and SYNTAX scores were calculated. Noninvasive PWA was performed with the SphygmoCor system. Results. Dividing the patients into tertiles according to augmentation index (AIx), more patients had significant CAD with higher Gensini and SYNTAX scores and lower myocardial blush grade (MBG) (p < 0.001 for all) in the third tertile. The AIx value to predict the presence of moderate to severe CAD as determined by SYNTAX score ≥ 23 was 24.45% (ROC analysis AUC: 0.96; sensitivity 88%, specificity: 93%, 95% CI: 0.93–0.99, p < 0.001). AIx was significantly correlated with Gensini and SYNTAX scores in SAP, USAP, and AMI patients after adjusting for age, gender, height, heart rate, hypertension, and diabetes. Conclusions. Increased AIx is associated with the presence and severity of CAD, and it may be used in selected patients during cardiovascular evaluation in outpatient settings for risk stratification prior to coronary angiography.

Improved pulse wave velocity estimation using an arterial tube-load model.

Pulse wave velocity (PWV) is the most important index of arterial stiffness. It is conventionally estimated by noninvasively measuring central and peripheral blood pressure (BP) and/or velocity (BV) waveforms and then detecting the foot-to-foot time delay between the waveforms wherein wave reflection is presumed absent. We developed techniques for improved estimation of PWV from the same waveforms. The techniques effectively estimate PWV from the entire waveforms, rather than just their feet, by mathematically eliminating the reflected wave via an arterial tube-load model. In this way, the techniques may be more robust to artifact while revealing the true PWV in absence of wave reflection. We applied the techniques to estimate aortic PWV from simultaneously and sequentially measured central and peripheral BP waveforms and simultaneously measured central BV and peripheral BP waveforms from 17 anesthetized animals during diverse interventions that perturbed BP widely. Since BP is the major acute determinant of aortic PWV, especially under anesthesia wherein vasomotor tone changes are minimal, we evaluated the techniques in terms of the ability of their PWV estimates to track the acute BP changes in each subject. Overall, the PWV estimates of the techniques tracked the BP changes better than those of the conventional technique (e.g., diastolic BP root-mean-squared errors of 3.4 versus 5.2 mmHg for the simultaneous BP waveforms and 7.0 versus 12.2 mmHg for the BV and BP waveforms (p <; 0.02)). With further testing, the arterial tube-load model-based PWV estimation techniques may afford more accurate arterial stiffness monitoring in hypertensive and other patients.

Reproducibility of pulse wave analysis and pulse wave velocity in patients with type 2 diabetes

Aims. Patients with type 2 diabetes have increased arterial stiffness and a high incidence of cardiovascular disease compared with non-diabetics. Arterial stiffness and central waveforms can be assessed by carotid-femoral pulse wave velocity (PWV) and pulse wave analysis (PWA) using the SphygmoCor device. These methods can potentially improve cardiovascular risk stratification in the future. However, a prerequisite is acceptable reproducibility. The objective of this study was to assess the intra- and inter-observer reproducibility of PWV and PWA indices in patients with type 2 diabetes using the SphygmoCor device. Methods. Two trained observers (A and B) each undertook two PWA and two carotid-femoral PWV recordings in random order in 20 patients with type 2 diabetes under standardized conditions on the right side of the patients. Observer A also made double recordings on the left side. The mean of the two recordings was used for inter-observer comparison. Data were analyzed by Bland-Altman plots. Results. The mean intra-observer differences (± 2SD) on the right side for observer A and B, respectively, were 0.0 ± 2.8 mmHg and 0.3 ± 3.2 mmHg (aortic systolic blood pressue (BP)), 0.0 ± 1.2 mmHg and 0.1 ± 1.0 mmHg (aortic diastolic BP), − 1.1 ± 3.2% and 1.1 ± 9.6% (central augmentation index (Aix)), − 1.6 ± 6.6% and 0.1 ± 9.0% (Aix normalized to heart rate 75 beats/min (Aix@HR75)) and 0.1 ± 1.8 m/s and 0.0 ± 1.6 m/s (PWV). The mean inter-observer differences (± 2SD) were − 2.6 ± 13.0 mmHg (aortic systolic BP), − 2.1 ± 7.4 mmHg (aortic diastolic BP), − 0.8 ± 8.4% (Aix), − 1.5 ± 7.4% (Aix@HR75) and − 0.3 ± 1.6 m/s (PWV). Left-vs-right comparison showed comparable results (observer A). Conclusions. PWA and PWV assessed with the SphygmoCor device are characterized by good reproducibility in patients with type 2 diabetes.

Exercise Central (Aortic) Blood Pressure Is Predominantly Driven by Forward Traveling Waves, Not Wave Reflection

Exercise hypertension independently predicts cardiovascular mortality, although little is known about exercise central hemodynamics. This study aimed to determine the contribution of arterial wave travel and aortic reservoir characteristics to central blood pressure (BP) during exercise. We hypothesized that exercise central BP would be principally related to forward wave travel and aortic reservoir function. After routine diagnostic coronary angiography, invasive pressure and flow velocity were recorded in the ascending aorta via sensor-tipped intra-arterial wires in 10 participants (age, 55±10 years; 70% men) free of coronary artery disease with normal left ventricular function. Measures were recorded at baseline and during supine cycle ergometry. Using wave intensity analysis, dominant wave types throughout the cardiac cycle were identified (forward and backward, compression, and decompression), and aortic reservoir and excess pressure were calculated. Central systolic BP increased significantly with exercise (Δ=19±12 mm Hg; P<0.001). This was associated with increases in systolic forward compression waves (Δ=12×10(6)±17×10(6) W·m(-2)·s(-1); P=0.045) and forward decompression waves in late systole (Δ=9×10(6)±6×10(6) W·m(-2)·s(-1); P<0.001). Despite significant augmentation in BP (Δ=9±6 mm Hg; P=0.002), reflected waves did not increase in magnitude (Δ=-1×10(6)±3×10(6) W·m(-2)·s(-1); P=0.2). Excess pressure rose significantly with exercise (Δ=16±9 mm Hg; P<0.001), and reservoir pressure integral fell (Δ=-5×10(5)±5×10(5) Pa·s; P=0.010). Change in reflection coefficient negatively correlated with change in central systolic BP (r=-0.68; P=0.03). We conclude that elevation of exercise central BP is principally because of increases in aortic forward traveling waves generated by left ventricular ejection. These findings have relevance to understanding central BP waveform morphology and pathophysiology of exercise hypertension.

Comparative Study on Tube-Load Modeling of Arterial Hemodynamics in Humans

In this paper, we assess the validity of two alternative tube-load models for describing the relationship between central aortic and peripheral arterial blood pressure (BP) waveforms in humans. In particular, a single-tube (1-TL) model and a serially connected two-tube (2-TL) model, both terminated with a Windkessel load, are considered as candidate representations of central aortic-peripheral arterial path. Using the central aortic, radial and femoral BP waveform data collected from eight human subjects undergoing coronary artery bypass graft with cardiopulmonary bypass procedure, the fidelity of the tube-load models was quantified and compared with each other. Both models could fit the central aortic-radial and central aortic-femoral BP waveform pairs effectively. Specifically, the models could estimate pulse travel time (PTT) accurately, and the model-derived frequency response was also close to the empirical transfer function estimate obtained directly from the central aortic and peripheral BP waveform data. However, 2-TL model was consistently superior to 1-TL model with statistical significance as far as the accuracy of the central aortic BP waveform was concerned. Indeed, the average waveform RMSE was 2.52 mmHg versus 3.24 mmHg for 2-TL and 1-TL models, respectively (p < 0.05); the r² value between measured and estimated central aortic BP waveforms was 0.96 and 0.93 for 2-TL and 1-TL models, respectively (p < 0.05). We concluded that the tube-load models considered in this paper are valid representations that can accurately reproduce central aortic-radial/femoral BP waveform relationships in humans, although the 2-TL model is preferred if an accurate central aortic BP waveform is highly desired.

Feasibility studies of Bragg probe for noninvasive carotid pulse waveform assessment

The arterial stiffness evaluation is largely reported as an independent predictor of cardiovascular diseases. The central pulse waveform can provide important data about arterial health and has been studied in patients with several pathologies, such as diabetes mellitus, coronary artery disease and hypertension. The implementation and feasibility studies of a fiber Bragg grating probe for noninvasive monitoring of the carotid pulse are described based on fiber Bragg grating technology. Assessment tests were carried out in carotids of different volunteers and it was possible to detect the carotid pulse waveform in all subjects. In one of the subjects, the sensor was also tested in terms of repeatability. Although further tests will be required for clinical investigation, the first studies suggest that the developed sensor can be a valid alternative to electromechanical tonometers.

Doppler US for Suspicion of Hepatic Arterial Ischemia in Orthotopically Transplanted Livers: Role of Central versus Intrahepatic Waveform Analysis

To compare the diagnostic performance of combinations of parameters derived from main hepatic artery (MHA) and intrahepatic artery (IHA) waveforms at Doppler ultrasonography (US), with the aim of developing a systematic approach to the evaluation of the hepatic arteries in orthotopic liver transplants in patients suspected of having hepatic arterial ischemia. This HIPAA-compliant retrospective study was approved by an institutional review board, with waiver of informed consent. From January 1, 2002, to November 1, 2011, 195 transplanted livers in 189 adults (129 men, 60 women; mean age, 53 years; age range, 18-73 years) who underwent Doppler US and follow-up (computed tomographic, magnetic resonance, or conventional) angiographic study within a 2-week interval were included. Diagnostic performance of the standard IHA and MHA criteria (resistive index [RI] < 0.5 and classic parvus tardus waveforms) with and without peak systolic velocity (PSV) thresholds (determined with receiver operating characteristic curve analysis) was assessed. The results of no-flow analysis and the most optimal MHA and IHA criteria were combined to create an algorithm, which was then applied to all liver transplants. The standard criteria (RI < 0.5 and classic parvus tardus) demonstrated greater sensitivity (80% vs 55%, P = .008) when applied to IHA waveforms compared with MHA waveforms. Optimal PSV cutoff values were less than 67 cm/sec and 39 cm/sec for MHA and IHA, respectively. The addition of a PSV threshold resulted in significant decrease in overall accuracy when applied to IHA (87% vs 73%, P < .001) and MHA (82% vs 66%, P = .002) criteria. Application of an algorithm reflecting a combination of the most optimal MHA and IHA criteria and the results of no-flow analysis resulted in 96% sensitivity and 83% specificity. An algorithmic approach involving a tailored evaluation of the geographic distribution of absent flow and the quantitative parameters and waveform morphology of the MHA and IHAs allows for improved diagnostic performance in the detection of hepatic arterial complications in at-risk patients with orthotopic liver transplants. http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.12120557/-/DC1.

Blood pressure as a drug target: what should we be measuring?

Clinicians and researchers have traditionally relied on esti-mates of systolic and diastolic pressure in the brachialartery to predict cardiovascular risk and guide individualtherapy. There is overwhelming evidence that usual BPmeasured in this way is a powerful predictor of future car-diovascular events [1],but the mechanistic link(s) betweenpressure and pathology (atheromatous disease and arte-rial thrombosis) is (are) incompletely understood.The dis-tinguished statistician Ronald Fisher (of‘Fisher’s exact test’)pointed out the excellent correlation between the inci-dence of lung cancer in the twentieth century and sales ofwashing machines in a tobacco-industry funded pamphletmocking the then available evidence that smoking causescancer. His point was that association does not prove cau-sality, but nor does it disprove it, and the subsequent evi-dence assembled by Richard Doll resolved the smoking/cancer issue definitively.Evidence from placebo-controlled randomized trialsshows that experimental interventions that lower brachialartery blood pressure also reduce cardiovascular events[2]. This not only underpins clinical decision making butalso supports the notion that high BP actually causes car-diovascular disease,rather than being a consequence of it.However, this is not the end of the story. Systolic and dias-tolic BP (SBP,DBP) are correlated with one another,both arelowered by drug treatment, but DBP behaves strikinglydifferently from SBP in predicting future risk.Subjects aged50–79 years in the Framingham cohort were groupedaccording to SBP ( 160 mmHg) tocontrol for the strong association between SBP on DBP andreduce the effect of SBP on risk within each group [3].DBPin each group was found to be

Dialysis Access Flow Phenomenon Demonstrated via an Internal Jugular Central Venous Catheter Uniquely Positioned within a Superior Vena Cava Stenosis

Dialysis Access Flow Phenomenon Demonstrated <i>via</i> an Internal Jugular Central Venous Catheter Uniquely Positioned within a Superior Vena Cava Stenosis