The Forgotten Variable of Shear Stress in Mitral Annular Calcification: Whole Blood Viscosity

The Impact of Prior Antithrombotic Use on Blood Viscosity in Cardioembolic Stroke with Non-Valvular Atrial Fibrillation

Although clinical studies have demonstrated that prior use of antiplatelets was associated with decreased blood viscosity (BV) in patients with acute ischemic stroke, the impact of previous anticoagulant use on blood viscosity in cardioembolic stroke with non-valvular AF (NVAF) has not yet been clearly studied. This single-center retrospective observational study aimed to determine the impact of prior antithrombotic (antiplatelet and anticoagulant) use on BV in patients with cardioembolic stroke (CES) due to NVAF. Patients with CES and NVAF were analyzed with the following inclusion criteria: (1) patients over 20 years of age admitted within five days of stroke onset; (2) ischemic stroke presumably due to an NVAF-derived embolus; (3) compatible cortical/subcortical lesion on brain computed tomography or magnetic resonance imaging; (4) hemoglobin level of 10-18 mg/dL; and (5) receiving antiplatelets within five days or anticoagulants within two days if previously medicated. From the screening of 195 patients (22% of the total stroke population during the study period) who had experienced ischemic stroke with AF, 160 were included for the final analysis. Eighty-nine patients (56%) were taking antithrombotics (antiplatelet, 57%; warfarin, 13%; NOACs, 30%) regularly. Compared to patients without previous antithrombotic use, those with previous antithrombotic use (antiplatelets, warfarin, and NOACs) were significantly associated with decreased systolic BV (SBV) and diastolic BV (DBV) (p < 0.036). In multiple linear regression analysis, hematocrit (Hct) level and prior antithrombotic use were significantly associated with decreased SBV and DBV. Hct was positively correlated with increased SBV and DBV. In Hct-adjusted partial correlation analysis, prior uses of any antithrombotic agents were associated with decreased SBV (r < -0.270, p < 0.015) and DBV (r < -0.183, p < 0.044). In conclusion, this study showed that prior antithrombotic use (antiplatelets, VKAs, and NOACs) was associated with decreased SBV and DBV in patients presenting with acute CES secondary to NVAF. Our results indicated that previous use of NOACs may be a useful hemorheological parameter in patients with acute CES due to NVAF. Accumulation of clinical data from a large number of patients with the risk of stroke occurrence, initial stroke severity, and functional outcome is necessary to assess the usefulness of BV.

Increased whole blood viscosity is associated with primary idiopathic complete atrioventricular block and poor clinical outcomes in these patients

BACKGROUND

Complete atrioventricular block is most commonly caused by age-related degeneration and fibrosis in the cardiac conduction system and is called primary idiopathic complete atrioventricular (iCAVB). Although many factors affect this situation, which increases with age in the cardiac conduction system, the relationship between whole blood viscosity (WBV) and iCAVB has not been clarified until now. In this study, we aim to reveal the relationship between iCAVB and WBV.

METHODS AND RESULTS

141 patients with dual-chamber permanent pacemaker implanted for iCAVB and 140 age- and sex-matched subjects were included in this study. The WBV values of the study groups were compared in both high shear rate (HSR) and low shear rate (LSR). Both WBV at HSR and WBV at LSR were significantly higher in the iCAVB group compared to the control group (16.11 [15.14-16.89] vs 14.40 [13.62-15.58]; 39.82 [17.43-55.23] vs 1.38 [-13.14-26.73]; p < 0.001, respectively). The patient population was followed up for an median of 38 months for all-cause mortality. Higher mortality rates were found in higher WBV at HSR and WBV at LSR (p < 0.001,for both).

CONCLUSIONS

In this study, WBV was found to be an independent predictor for iCAVB, and in these patients WBV was associated with poor clinical outcomes.

Drop-of-sample rheometry of biological fluids by noncontact acoustic tweezing spectroscopy

Knowledge of rheological properties, such as viscosity and elasticity, is necessary for efficient material processing and transportation as well as biological analysis. Existing rheometers operate with large sample volume and induce sample contact with container or device walls, which are inadequate for rheological analysis of sensitive fluids limited in availability. In this work, we introduce acoustic tweezing spectroscopy (ATS), a novel noncontact rheological technique that operates with a single 4-6 μl drop of fluid sample. In ATS, a sample drop is acoustically levitated and then exposed to a modulated acoustic signal to induce its forced oscillation. The time-dependent sample viscosity and elasticity are measured from the resulting drop response. The ATS measurements of polymeric solutions (dextran, xanthan gum, gelatin) agree well with previously reported data. The ATS predicts that the shear viscosity of blood plasma increases from 1.5 cP at 1.5 min of coagulation onset to 3.35 cP at 9 min, while its shear elastic modulus grows from a negligible value to 10.7 Pa between 3.5 min and 6.5 min. Coagulation increases whole blood viscosity from 5.4 cP to 20.7 cP and elasticity from 0.1 Pa to 19.2 Pa at 15 min. In summary, ATS provides the opportunity for sensitive small-volume rheological analysis in biomedical research and medical, pharmaceutical, and chemical industries.

Comparing of Frequency Shift and Impedance Analysis Method Based on QCM Sensor for Measuring the Blood Viscosity

Blood viscosity measurements are crucial for the diagnosis of cardiovascular and hematological diseases. Traditional blood viscosity measurements have obvious limitations because of their expensive equipment usage and large sample consumption. In this study, blood viscosity was measured by the oscillating circuit method and impedance analysis method based on single QCM. In addition, the effectiveness of two methods with high precision and less sample is proved by the experiments. Moreover, compared to the result from a standard rotational viscometer, the maximum relative errors of the proposed oscillating circuit method and impedance analysis method are ±5.2% and ±1.8%, respectively. A reliability test is performed by repeated measurement (N = 5), and the result shows that the standard deviation about 0.9% of impedance analysis is smaller than that of oscillating circuit method. Therefore, the impedance analysis method is superior. Further, the repeatability of impedance analysis method was evaluated by regression analysis method, and the correlation coefficient R2 > 0.965 demonstrated that it had excellent reproducibility.

Association of whole blood viscosity with thrombus presence in patients undergoing transoesophageal echocardiography

Whole blood viscosity (WBV) is considered as a reasonable proxy measure of blood flow, and it has been investigated in different cohort settings, including in patients with deep venous thrombosis, arterial thrombosis, acute stent thrombosis, and left ventricular apical thrombus formation following acute coronary syndrome. To determine the association between WBV and the presence of thrombus in the left atrium (LA) or left atrial appendage (LAA) in individuals who had transoesophageal echocardiography (TEE). The clinical data from 262 consecutive patients who had TEE at our facility were included in this retrospective cohort study. WBV was determined at both a high shear rate (HSR) and low shear rate (LSR) using hematocrit and total protein levels. In 22 cases (8.3%), the thrombus was detected. According to multivariable analyses, WBV at HSR and LSR were independently linked with thrombus detection in TEE. In a receiver operating characteristic (ROC) analysis, the area under curve (AUC) values of WBV at HSR and LSR were 0.77 and 0.76, respectively. To predict the presence of thrombus in TEE; the ideal value of WBV at HSR was > 16.6 with 81% sensitivity and 69% specificity and the ideal value of WBV at LSR was > 51.4 with 81% sensitivity and 70% specificity. This was the first study to indicate that significantly higher levels of WBV at both the HSR and LSR were linked to the presence of thrombus in the LA and LAA in cases who underwent TEE.

Whole blood viscosity in patients with aortic stenosis

Whole blood viscosity (WBV) may promote endothelial shear stress, inflammation, and can accelerate the atherosclerotic process. We aimed to evaluate the relationship between WBV and aortic stenosis. The study included 209 participants of whom 49 patients had severe aortic stenosis, 98 patients had mild-to-moderate aortic stenosis and 62 patients served as control. WBV values were significantly higher for high shear rate (HSR) (P = 0.001) and for low shear rate (LSR) (P = 0.002) in severe aortic stenosis group. HSR and LSR were correlated with mean systolic transaortic gradient (P < 0.001 and P < 0.001, respectively). WBV for both LSR and HSR were found to be independent predictors for the aortic stenosis severity (P = 0.034 and P = 0.049, respectively). We found a significant relationship between WBV and aortic stenosis.

Whole blood viscosity in microvascular angina and coronary artery disease: Significance and utility

INTRODUCTION AND OBJECTIVES

Whole blood viscosity (WBV) is the intrinsic resistance of blood flow in vessels, and when elevated induces endothelial shear stress and endothelial inflammation and can accelerate the atherosclerotic process. This study aims to compare WBV levels in patients with microvascular angina (MVA), patients with coronary artery disease (CAD), and normal controls, and to identify the relationship between WBV and high-sensitivity C-reactive protein as a marker of inflammation in MVA and CAD.

METHODS

A total of 573 patients were studied. The MVA group consisted of 189 subjects, the CAD group consisted of 203 subjects, and the control group consisted of 181 age- and gender-matched individuals. WBV was calculated from hematocrit and plasma protein concentration at a low shear rate (0.5 s^-1) and high shear rate (208 s^-1) by a validated equation.

RESULTS

Patients with CAD and MVA had significantly higher WBV at both low and high shear rates compared to the control group. Correlation analysis revealed a significant relationship between high-sensitivity C-reactive protein and WBV at low (r=0.556; p<0.001) and high shear rates (r=0.562) in the CAD group and at low (r=0.475) and high shear rates (r=0.493) in the MVA group.

CONCLUSIONS

Overall, this study demonstrated a significant and independent association between blood viscosity and the existence of endothelial inflammation and the atherosclerotic process.

Mitral Annular Calcification: Association with Atherosclerosis and Clinical Implications

PURPOSE OF REVIEW

This review summarizes the pathophysiology of mitral annular calcification (MAC) with recent findings and current strategies for diagnosis and treatment.

RECENT FINDINGS

Major factors in MAC development seem to be shear stress of the flow past the mitral valve, local inflammation, and dysregulation in regulators of mineral metabolism. MAC itself poses daunting technical challenges. Implanting a valve on top of the calcium bar might lead to paravalvular leak (PVL) that is less likely to heal. Annular decalcification allows for better valve seating and potentially better healing and less PVL. This, however, comes with the risk for catastrophic atrioventricular groove disruption. MAC can be sharply dissected with the scalpel; the annulus can be reconstructed with the autologous pericardium. Transcatheter mitral valve replacement is a promising approach in the treatment of patients who are deemed high-risk surgical candidates with severe MAC. MAC is a multifactorial disease that has some commonalities with atherosclerosis, mainly regarding lipid accumulation and calcium deposition. It is of great clinical importance, being a risk marker of cardiovascular events (including sudden death) and, with its progression, can have a negative impact on patients' lives.

Intraoperative changes in whole-blood viscosity in patients undergoing robot-assisted laparoscopic prostatectomy in the steep Trendelenburg position with pneumoperitoneum: a prospective nonrandomized observational cohort study

Background

The aim of this study was to investigate the effect of the steep Trendelenburg position (STP) with pneumoperitoneum on whole-blood viscosity (WBV) in patients undergoing robot-assisted laparoscopic prostatectomy (RALP). The study also analyzed the associations of clinical patient-specific and time-dependent variables with WBV and recorded postoperative outcomes.

Methods

Fifty-eight adult male patients (ASA physical status of I or II) undergoing elective RALP were prospectively analyzed in this study. WBV was intraoperatively measured three times: at the beginning of surgery in the supine position without pneumoperitoneum; after 30 min in the STP with pneumoperitoneum; and at the end of surgery in the supine position without pneumoperitoneum. The WBV at a high shear rate (300 s^− 1) was recorded as systolic blood viscosity (SBV) and that at a low shear rate (5 s^− 1) was recorded as diastolic blood viscosity (DBV). Systolic blood hyperviscosity was defined as > 13.0 cP at 300 s^− 1 and diastolic blood hyperviscosity was defined as > 4.1 cP at 5 s^− 1.

Results

The WBV and incidences of systolic and diastolic blood hyperviscosity significantly increased from the supine position without pneumoperitoneum to the STP with pneumoperitoneum. When RALP was performed in the STP with pneumoperitoneum, 12 patients (27.3%) who had normal SBV at the beginning of surgery and 11 patients (26.8%) who had normal DBV at the beginning of surgery developed new systolic and diastolic blood hyperviscosity, respectively. The degree of increase in WBV after positioning with the STP and pneumoperitoneum was higher in the patients with hyperviscosity than in those without hyperviscosity at the beginning of surgery. Higher preoperative body mass index (BMI) and hematocrit level were associated with the development of both systolic and diastolic blood hyperviscosity in the STP with pneumoperitoneum. All patients were postoperatively discharged without fatal complications.

Conclusions

Changes in surgical position may influence WBV, and higher preoperative BMI and hematocrit level are independent factors associated with the risk of hyperviscosity during RALP in the STP with pneumoperitoneum.

Trial registration

Clinical Research Information Service, Republic of Korea, approval number: KCT0003295 on October 25, 2018.

Usefulness of the whole blood viscosity to predict stent thrombosis in ST-elevation myocardial infarction

Aim: This study sought to investigate the predictive value of estimated whole blood viscosity (WBV) for stent thrombosis (ST) in ST-elevation myocardial infarction (STEMI) patients who underwent percutaneous coronary intervention. Materials & methods: A total of 1720 STEMI patients treated with primary percutaneous coronary intervention were followed up for median 36.0 months. WBV was calculated according to the Simone's formula. Results: During follow-up period, 119 patients were diagnosed as 'definite' ST. The rate of ST was significantly higher in the high WBV group. In multivariate analysis, adjusted for other factors, higher WBV significantly increased risk of ST at both shear rates. Conclusion: Being an easily accessible and costless parameter, WBV seems to be an emerging predictor of ST in patients with STEMI.

The Contribution of Whole Blood Viscosity to the Process of Aortic Valve Sclerosis

OBJECTIVE

We aimed to investigate whether increased whole blood viscosity (WBV) could be an important factor for the occurrence of aortic valve sclerosis (AVS).

SUBJECTS AND METHODS

A total of 209 patients were enrolled in the study. WBV was calculated using the hematocrit and total plasma protein at a low shear rate (LSR) and a high shear rate (HSR). AVS was defined as irregular valve thickening and calcification (without evidence of outflow obstruction) documented by a peak transvalvular velocity < 2.5 m/s on echocardiographic examination. The patient group consisted of 109 patients with AVS (77 females, 32 males), and 100 subjects without AVS (65 females, 35 males) were assigned to the control group.

RESULTS

In the AVS group, WBV values were significantly higher for HSR (17.4 ± 0.5 vs. 17.1 ± 0.7 208 s-1, p < 0.001) and LSR (65.9 ± 12.5 vs. 59.7 ± 16.7 0.5 s-1, p = 0.002). In multivariate logistic regression analysis, WBV at HSR and LSR were independent predictors of AVS (odds ratio, OR: 2.24, 95% confidence interval, CI: 1.38-3.64, p = 0.001; OR: 1.026, 95% CI: 1.006-1.046, p = 0.01, respectively). Receiver-operating characteristic (ROC) curve analysis indicated that a WBV cutoff value of 65.4 at LSR had a sensitivity of 46.8% and a specificity of 60.0% (area under the ROC curve, AUC: 0.615, 95% CI: 0.535-0.696, p = 0.004), and a WBV cutoff value of 17.1 at HSR had a sensitivity of 61.5% and specificity of 53% (AUC: 0.648, 95% CI: 0.571-0.725, p < 0.001) for the prediction of AVS.

CONCLUSION

This study demonstrated that WBV was independently associated with AVS. WBV could be an indicator of inflammation and vessel remodeling without evidence of outflow obstruction.

Evaluation of Whole Blood Viscosity in Patients with Aortic Sclerosis

Background: Blood viscosity and aortic sclerosis (AS) are strong predictors of cardiovascular events. The effects of blood viscosity on AS have not been studied adequately. We aimed to investigate the potential connection between whole blood viscosity (WBV) and AS. Methods: AS was detected by transthoracic echocardiography. The estimation of WBV was carried out at both high shear rate (HSR) (208/s) and low shear rate (LSR) (0.5/s) by previously validated formulae using hematocrit (HcT) and total protein (TP) in g/L. WBV at HSR (208/s) is: (0.12 × HcT) + 0.17 (TP - 2.07) and WBV at LSR (0.5/s) is: (1.89 × HcT) + 3.76 (TP - 78.42). Comparisons of WBV at both HSR and LSR were made between patients with and without AS. Results: We included 94 patients with AS (male = 30.9%, mean age = 67.5 y) and 97 control subjects without AS (male =26.6%, mean age = 69.1 y). Almost all of the clinical, echocardiographic, and biochemical characteristics were similar, but TP values were significantly higher in the AS group than in the control group (72.9 ± 5 g/L vs. 75.8 ± 6.1 g/L; p value < 0.001). Hemoglobin and HcT levels were similar (p value = 0.604 and p value = 0.431, respectively). In the AS group, WBV at LSR and HSR was higher than that in the control group (p value = 0.001 for both LSR and HSR). In multiple stepwise logistic regression analysis, WBV was an independent predictor of AS (p value < 0.001). Conclusion: We found higher WBV in patients with AS than in patients without AS at both LSR (0.5/s) and HSR (208/s). WBV at both LSR and HSR was independently associated with AS.

Prognostic significance of whole blood viscosity estimated by de Simone’s formula in ST-elevation myocardial infarction

Background: We assessed the predictive value of estimated whole blood viscosity (WBV) in-hospital and long-term cardiovascular outcomes in patients with ST-elevation myocardial infarction (STEMI). Materials & methods: One thousand eight hundred and thirty-five STEMI patients were followed up for median 34.6 months. WBV was calculated consistent with the de Simone’s formula. Results: In-hospital and long-term major adverse cardiovascular events (MACE) demonstrated an incremental trend in ascending order of WBV tertiles at low and high shear rate. Kaplan–Meier analysis showed a higher occurrence of long-term MACE in third WBV tertiles compared with other tertiles. Conclusion: WBV seems to be a feasible prognostic indicator of short- and long-term cardiovascular adverse events in patients with STEMI. As an easily available parameter, WBV may be utilized in identifying high-risk patients for subsequent MACE.

An overlooked parameter in coronary slow flow phenomenon: whole blood viscosity

Aims: We aimed to assess the relationship between coronary slow flow phenomenon (CSFP) and whole blood viscosity (WBV). Materials & methods: Two hundred patients with CSFP and 200 subjects with normal coronary arteries as control group were enrolled. WBV was calculated from hematocrit and plasma protein concentration at low shear rate (LSR) (0.5 s-1) and high shear rate (HSR) (208 s-1) by a validated equation. Results: CSFP patients had significantly higher WBV for LSR and HSR. The mean corrected TIMI frame count was highest in the highest tertile group for both shear rates. Corrected TIMI frame count revealed a significant relationship with WBV for LSR (r = 0.562) and HSR (r = 0.611). At multivariate analysis, WBV at LSR and HSR were independent predictors of CSFP. Conclusion: WBV seemed to have a significant and an independent predictor of CSFP.