Bramwell-Hill modeling for local aortic pulse wave velocity estimation: a validation study with velocity-encoded cardiovascular magnetic resonance and invasive pressure assessment

<p>Abstract</p> <p>Background</p> <p>The Bramwell-Hill model describes the relation between vascular wall stiffness expressed in aortic distensibility and the pulse wave velocity (PWV), which is the propagation speed of the systolic pressure wave through the aorta. The main objective of this study was to test the validity of this model locally in the aorta by using PWV-assessments based on in-plane velocity-encoded cardiovascular magnetic resonance (CMR), with invasive pressure measurements serving as the gold standard.</p> <p>Methods</p> <p>Seventeen patients (14 male, 3 female, mean age ± standard deviation = 57 ± 9 years) awaiting cardiac catheterization were prospectively included. During catheterization, intra-arterial pressure measurements were obtained in the aorta at multiple locations 5.8 cm apart. PWV was determined regionally over the aortic arch and locally in the proximal descending aorta. Subsequently, patients underwent a CMR examination to measure aortic PWV and aortic distention. Distensibility was determined locally from the aortic distension at the proximal descending aorta and the pulse pressure measured invasively during catheterization and non-invasively from brachial cuff-assessment. PWV was determined regionally in the aortic arch using through-plane and in-plane velocity-encoded CMR, and locally at the proximal descending aorta using in-plane velocity-encoded CMR. Validity of the Bramwell-Hill model was tested by evaluating associations between distensibility and PWV. Also, theoretical PWV was calculated from distensibility measurements and compared with pressure-assessed PWV.</p> <p>Results</p> <p>In-plane velocity-encoded CMR provides stronger correlation (p = 0.02) between CMR and pressure-assessed PWV than through-plane velocity-encoded CMR (r = 0.69 versus r = 0.26), with a non-significant mean error of 0.2 ± 1.6 m/s for in-plane versus a significant (p = 0.006) error of 1.3 ± 1.7 m/s for through-plane velocity-encoded CMR. The Bramwell-Hill model shows a significantly (p = 0.01) stronger association between distensibility and PWV for local assessment (r = 0.8) than for regional assessment (r = 0.7), both for CMR and for pressure-assessed PWV. Theoretical PWV is strongly correlated (r = 0.8) with pressure-assessed PWV, with a statistically significant (p = 0.04) mean underestimation of 0.6 ± 1.1 m/s. This theoretical PWV-estimation is more accurate when invasively-assessed pulse pressure is used instead of brachial cuff-assessment (p = 0.03).</p> <p>Conclusions</p> <p>CMR with in-plane velocity-encoding is the optimal approach for studying Bramwell-Hill associations between local PWV and aortic distensibility. This approach enables non-invasive estimation of local pulse pressure and distensibility.</p

Aortic stiffness as a marker of cardiac function and myocardial strain in patients undergoing aortic valve replacement

Background: Cardiac function and myocardial strain are affected by cardiac afterload, which is in part due to the stiffness of the aortic wall. In this study, we hypothesize that aortic pulse wave velocity (PWV) as a marker of aortic stiffness correlates with conventional clinical and biochemical markers of cardiac function and perioperative myocardial strain in aortic valve replacement (AVR). Methods: Patients undergoing AVR for aortic stenosis between June 2010 and August 2012 were recruited for inclusion in this study. PWV, NYHA class and left ventricular (LV) function were assessed pre-operatively. PWV was analysed both as a continuous and dichotomous variable according to age-standardized reference values. B-type natriuretic peptide (BNP) was measured pre-operatively, and at 3 h and 18-24 h after cardiopulmonary bypass (CPB). NYHA class, leg edema, and LV function were recorded at follow-up (409 ± 159 days). Results: Fifty-six patients (16 females) with a mean age of 71 ± 8.4 years were included, with 50 (89%) patients completing follow-up. The NYHA class of PWV-norm patients was significantly lower than PWV-high patients both pre- and post-operatively. Multiple logistic regression also highlighted PWV-cut off as an independent predictor of NYHA class pre- and post-operatively (OR 8.3, 95%CI [2.27,33.33] and OR 14.44, 95%CI [1.49,139.31] respectively). No significant relationship was observed between PWV and either LV function or plasma BNP. Conclusion: In patients undergoing AVR for aortic stenosis, PWV is independently related to pre- and post-operative NYHA class but not to LV function or BNP. These findings provisionally support the use of perioperative PWV as a non-invasive marker of clinical functional status, which when used in conjunction with biomarkers of myocardial strain such as BNP, may provide a holistic functional assessment of patients undergoing aortic valve surgery. However, in order for PWV assessment to be translated into clinical practice and utilised as more than simply a research tool, further validation is required in the form of larger prospective studies specifically designed to assess the relationship between PWV and these functional clinical outcomes

Aortic stiffness is related to left ventricular diastolic function in patients with diabetes mellitus type 1: assessment with MRI and speckle tracking strain analysis

Diabetes mellitus type 1 (DM1) is associated with aortic stiffening and left ventricular (LV) diastolic dysfunction, however the relationship between aortic stiffness and LV diastolic dysfunction in DM1 patients is still largely unknown. The purpose of this study was to evaluate whether an increased aortic stiffness, expressed by increased aortic pulse wave velocity (PWV), is associated with subclinical LV diastolic dysfunction and decreased left atrial (LA) compliance as assessed with speckle tracking strain analysis in patients with DM1. Aortic PWV was assessed with cardiovascular magnetic resonance in 41 DM1 patients. Patients underwent echocardiography for assessment of conventional LV diastolic function indices and LV and LA longitudinal strain and strain rate (SR) assessed with speckle tracking strain analysis. LV SR during the isovolumic relaxation period (SRIVR) and LA strain were recorded and the E-wave velocity to SRIVR velocity ratio (E/SRIVR) was calculated. Independent samples t test and multivariate linear regression analyses were used for statistical analyses. Aortic PWV significantly correlated with SRIVR (beta = -0.71, p 0.10). In DM1 patients, aortic stiffness is inversely associated with sensitive markers of LV diastolic function and decrease in LA compliance as measured with echocardiographic speckle tracking strain analysis

The effect of hypertension on aortic pulse wave velocity in type-1 diabetes mellitus patients: assessment with MRI.

Item does not contain fulltextTo investigate in type-1 diabetes mellitus (DM1) patients the role of hypertension and of DM1 itself on aortic stiffness by using magnetic resonance imaging (MRI). Consecutive patients from the diabetes and hypertension outpatient clinic and healthy volunteers were included in our study. Subjects were divided into four groups: 32 healthy volunteers (mean age: 54.5 +/- 6.8 years), 20 DM1 patients (mean age: 48.3 +/- 5.9 years), 31 hypertensive patients (mean age: 59.9 +/- 7.2 years) and 28 patients with both DM1 and hypertension (mean age: 50.1 +/- 6.2 years). Aortic stiffness was measured by means of pulse wave velocity (PWV) using velocity-encoded MRI. Analysis of variance (ANOVA), uni- and multivariable regression models and the Bonferroni-test for multiple testing, were used for statistical analyses. Mean aortic PWV was 5.7 +/- 1.2 m/s in healthy volunteers, 5.9 +/- 1.2 m/s in DM1 patients without hypertension, 7.3 +/- 1.2 m/s in hypertensive patients and 7.3 +/- 1.3 m/s in patients with both DM1 and hypertension. Compared to healthy control subjects, aortic PWV was significantly higher in patients with hypertension (P < 0.001) and in patients with both DM1 and hypertension (P < 0.001), whereas aortic PWV was not increased in patients having DM1 alone. Furthermore, aortic PWV was significantly higher in DM1 patients with hypertension than in patients with DM1 alone (P = 0.002). These findings remained after adjustment for confounding factors. Hypertension has a predominant contributive effect on aortic stiffness in DM1 patients whereas the direct diabetic effect on aortic stiffness is small.1 maart 201

Dilatation of the ascending aorta is associated with presence of aortic regurgitation in patients after repair of tetralogy of Fallot

To evaluate the association between aortic morphology and elasticity with aortic regurgitation in surgically corrected of tetralogy of Fallot (TOF) patients. We retrospectively identified 72 consecutive patients with surgically corrected TOF and 27 healthy controls who underwent cardiac MRI evaluation. Velocity-encoded cine MRI was used to quantify degree of aortic regurgitation (AR) in TOF patients. Ascending aorta diameters were measured at standard levels on MRA images. Aortic pulse-wave velocity (PWV) was quantified with MRI. Morphological and functional MRI variables were compared between groups of TOF patients with and without clinically relevant AR and controls. The association between aortic morphology and elasticity with the presence of AR was evaluated using univariate and multivariate logistic regression. The majority of TOF patients had only trace AR. Nine TOF patients (12 %) had an AR fraction higher than 15 %. Indexed aorta diameter at the sinotubular junction (p = 0.007), at the RPA level (p = 0.006), and low left ventricular ejection fraction (LVEF) (p = 0.015) showed the strongest associations with the presence of at least mild AR, which persisted after controlling for age and gender. Increased ascending aorta dimension is associated with AR in patients after repair of TOF. LVEF was also low in the group of patients with relevant AR compared to those without, suggesting even mild to moderate AR may contribute to LV dysfunction in these patients. Enlarged ascending aorta may be an indication for precise quantification of regurgitant fraction with MRI, since symptomatic patients may need aortic valve repair when moderate regurgitation is present