Carotid artery velocity time integral and corrected flow time measured by a wearable Doppler ultrasound detect stroke volume rise from simulated hemorrhage to transfusion

Objective Doppler ultrasonography of the common carotid artery is used to infer stroke volume change and a wearable Doppler ultrasound has been designed to improve this workflow. Previously, in a human model of hemorrhage and resuscitation comprising approximately 50,000 cardiac cycles, we found a strong, linear correlation between changing stroke volume, and measures from the carotid Doppler signal, however, optimal Doppler thresholds for detecting a 10% stroke volume change were not reported. In this Research Note, we present these thresholds, their sensitivities, specificities and areas under their receiver operator curves (AUROC). Results Augmentation of carotid artery maximum velocity time integral and corrected flowtime by 18% and 4%, respectively, accurately captured 10% stroke volume rise. The sensitivity and specificity for these thresholds were identical at 89% and 100%. These data are similar to previous investigations in healthy volunteers monitored by the wearable ultrasound.

Pulmonary Vascular Resistance Estimated by Echocardiography in Dogs With Myxomatous Mitral Valve Disease and Pulmonary Hypertension Probability

Post-capillary pulmonary hypertension (PH) is a life-threatening complication in dogs with myxomatous mitral valve disease (MMVD). An increase in pulmonary vascular resistance (PVR) is associated with post-capillary PH progression. In humans, PVR estimated by echocardiography (PVRecho) enables the non-invasive assessment of PVR in patients with PH. This study aimed to evaluate the clinical utility of PVRecho in dogs with MMVD, PH probability, and right-sided congestive heart failure (R-CHF). Dogs with MMVD and detectable tricuspid valve regurgitation were included in the study. Dogs were classified into three PH probability groups (low/intermediate/high) and according to the presence or absence of R-CHF. All dogs underwent echocardiographic measurements for right ventricular (RV) morphology and function. PVRecho was calculated by two methods using tricuspid valve regurgitation velocity and velocity–time integral of the pulmonary artery flow (PVRecho and PVRecho2). RV size indicators were significantly higher with a higher probability of PH. RV strain and velocity–time integral of the pulmonary artery flow in the high probability group were significantly lower than those in the other groups. Tricuspid valve regurgitation velocity, PVRecho, and PVRecho2 were significantly higher with an increase in PH probability. Logistic regression analysis revealed a significant association between the presence of R-CHF and increased PVRecho2 and end-diastolic RV internal dimension normalized by body weight. PVRecho and PVRecho2 showed significant differences among the PH probability groups. These non-invasive variables may be useful for the diagnosis and stratification of PH and the determination of the presence of R-CHF in dogs with MMVD.

O006 Early vascular ageing in children with sleep disordered breathing: evidence of vascular hypertrophy and hyperplasia

Children with sleep disordered breathing (SDB) have evidence of increased blood flow velocity and sympathetic overactivity. Sympathetic overactivity leads to peripheral vasoconstriction, increased vascular resistance and consequently, increases blood flow velocity. Early vascular ageing involves premature arterial thickening and stiffening that leads to changes in vascular function. Both increased blood flow velocity and sympathetic overactivity are promoters of arterial remodelling and hence, early vascular ageing. No studies have directly histologically investigated arterial wall structure in children with SDB and how it relates to vascular function. Thirty-six children scheduled for tonsillectomy underwent polysomnography to determine SDB severity and resting brachial artery blood flow velocity (velocity time integral and peak systolic velocity) using Doppler ultrasound. The dorsal lingual artery (tonsil) was stained using hematoxylin and eosin techniques to examine arterial wall structures. Increased velocity time integral correlated with increased arterial medial thickness (r = 0.50, P<0.01), arterial smooth muscle cells (r =0.43, P<0.05) and arterial smooth muscle layers (r=0.45, P<0.01). These relationships remained significant after controlling for body-mass index (BMI). Increased BMI was associated with increased velocity time integral (r=0.61, P<0.01), arterial medial thickness (r=0.37, P<0.05) and arterial medial area (r=0.36, P<0.05). SpO2nadir (TST/REM) was inversely associated with arterial medial area (r=-0.35; r=-0.38, P<0.05). These results demonstrate that increased blood flow velocity is associated with changes in arterial wall composition in children with SDB. This suggests that paediatric SDB, a treatable disorder, is potentially a modifiable risk factor for early vascular ageing and resultant cardiovascular disease in adulthood.

An electrographic AV optimization for the maximum integrative atrioventricular and ventricular resynchronization in CRT

Background Atrioventricular (AV) delay could affect AV and ventricular synchrony in cardiac resynchronization therapy (CRT). Strategies to optimize AV delay according to optimal AV synchrony (AVopt-AV) or ventricular synchrony (AVopt-V) would potentially be discordant. This study aimed to explore a new AV delay optimization algorithm guided by electrograms to obtain the maximum integrative effects of AV and ventricular resynchronization (opt-AV). Methods Forty-nine patients with CRT were enrolled. AVopt-AV was measured through the Ritter method. AVopt-V was obtained by yielding the narrowest QRS. The opt-AV was considered to be AVopt-AV or AVopt-V when their difference was < 20 ms, and to be the AV delay with the maximal aortic velocity–time integral between AVopt-AV and AVopt-V when their difference was > 20 ms. Results The results showed that sensing/pacing AVopt-AV (SAVopt-AV/PAVopt-AV) were correlated with atrial activation time (Pend-As/Pend-Ap) (P < 0.05). Sensing/pacing AVopt-V (SAVopt-V/PAVopt-V) was correlated with the intrinsic AV conduction time (As-Vs/Ap-Vs) (P < 0.01). The percentages of patients with more than 20 ms differences between SAVopt-AV/PAVopt-AV and SAVopt-V/PAVopt-V were 62.9% and 57.1%, respectively. Among them, opt-AV was linearly correlated with SAVopt-AV/PAVopt-AV and SAVopt-V/PAVopt-V. The sensing opt-AV (opt-SAV) = 0.1 × SAVopt-AV + 0.4 × SAVopt-V + 70 ms (R2 = 0.665, P < 0.01) and the pacing opt-AV (opt-PAV) = 0.25 × PAVopt-AV + 0.5 × PAVopt-V + 30 ms (R2 = 0.560, P < 0.01). Conclusion The SAVopt-AV/PAVopt-AV and SAVopt-V/PAVopt-V were correlated with the atrial activation time and the intrinsic AV conduction interval respectively. Almost half of the patients had a > 20 ms difference between SAVopt-AV/PAVopt-AV and SAVopt-V/PAVopt-V. The opt-AV could be estimated based on electrogram parameters.

An electrographic AV optimization for the maximum integrative atrioventricular and ventricular resynchronization in CRT

Background:Atrioventricular (AV) delay could affect AV and ventricular synchrony in cardiac resynchronization therapy (CRT). Strategies to optimize AV delay according to optimal AV synchrony (AVopt-AV) or ventricular synchrony (AVopt-V) would potentially be in discordant. This study aimed to explore a new AV delay optimization algorithm guided by electrograms to get the maximum integrative effects of AV and ventricular resynchronization (opt-AV).Methods:Forty-nine patients with CRT were enrolled. AVopt-AV was measured through the Ritter method. AVopt-V was obtained by yielding the narrowest QRS. The opt-AV was considered to be AVopt-AV or AVopt-V when their difference was <20ms, and to be the AV delay with the maximal aortic velocity-time integral between AVopt-AV and AVopt-V when their difference was >20ms.Results:The results showed sensing/pacing AVopt-AV (SAVopt-AV/PAVopt-AV) were correlated with atrial activation time (Pend-As/ Pend-Ap)( P＜0.05 ). Sensing/pacing AVopt-V (SAVopt-V/PAVopt-V) were correlated with the intrinsic AV conduction time (As-Vs/Ap-Vs) (P＜0.01). The percentages of patients with more than 20ms differences between SAVopt-AV/PAVopt-AV and SAVopt-V/PAVopt-V were 62.9% and 57.1%, respectively. Among them, the opt-AV were linearly correlated with SAVopt-AV/PAVopt-AV and SAVopt-V/PAVopt-V. The sensing opt-AV (opt-SAV)=0.1×SAVopt-AV+0.4×SAVopt-V+70ms (R2=0.665, P<0.01) and the pacing opt-AV (opt-PAV)=0.25×PAVopt-AV+0.5×PAVopt-V+30ms (R2=0.560, P<0.01).Conclusion:The SAVopt-AV/PAVopt-AV and SAVopt-V/PAVopt-V were correlated with the atrial activation time and the intrinsic AV conduction interval respectively. Almost half of patients had a >20ms difference between SAVopt-AV/PAVopt-AV and SAVopt-V/PAVopt-V. The opt-AV could be estimated based on electrogram parameters.

Studies on Pulsed-wave Doppler Echocardiographic Parameters of Blood Flow through Mitral, Tricuspid and Aortic Valves in Healthy Indian Spitz Dogs

Background: Pulsed-wave Doppler measures blood flow at specific point and provides information on velocity, direction and uniformity of blood flow throughout cardiac cycle. Till date, there is no published data on study of cardiac parameters using pulsed-wave Doppler echocardiography in Indian Spitz dogs.Methods: Twenty-four clinically normal Indian Spitz dogs were subjected to pulsed-wave Doppler echocardiography to determine the reference intervals for Doppler parameters of blood flow through mitral, tricuspid and aortic valves. Mitral peak E and A-wave velocities, E/A ratio, deceleration time, isovolumic relaxation time, E and A-wave velocity time integral, E duration and A duration were 0.69±0.09 m/s, 0.43±0.12 m/s, 1.69±0.45, 111.25±35.94 ms, 48.50±24.77 ms, 0.07±0.01 m and 0.04±0.02 m, 196.88±44.38 ms and 181.25±64.89 ms, respectively. Tricuspid peak E and A-wave velocities, E/A ratio and E and A-wave velocity time integral were 0.57±0.11 m/s, 0.38±0.08 m/s, 1.56±0.32 and 0.07±0.02 m and 0.05±0.01 m, respectively. Aortic peak velocity, velocity time integral and ejection time were 0.87±0.07 m/s, 0.11±0.02 m and 0.25±0.04 s, respectively. Conclusion: The reference values of flow parameters across mitral, tricuspid and aortic valves using pulsed-wave Doppler echocardiography were determined. Mitral, tricuspid and aortic valve flow variables were unaffected by gender whereas isovolumic relaxation correlated positively with body weight.