Fingertip digital thermal monitoring: a fingerprint for cardiovascular disease?

Digital thermography and vascular involvement in β-thalassemia intermedia

Beta-thalassemia intermedia (β-TI) is associated with vascular dysfunction. We used digital thermal monitoring (DTM), a non-invasive tool that evaluates vascular function based on changes in fingertip temperature during and after cuff occlusion on β-TI patients. Thirty-three patients (18 years and older) were recruited in this study and divided into 3 groups: thalassemia, anemic controls, and healthy controls. Exclusion criteria included factors that are known to be associated with vascular damage. Patients underwent DTM and results were extracted as vascular reactivity index (VRI), a measure of how well the circulatory system responds to stimuli that require adjustments of blood flow. One-way analysis of variance (ANOVA) was used to test the mean difference in VRI between the 3 groups. A multiple linear regression was also carried out with VRI as the outcome of interest and a function of covariates that were thought to be of clinical relevance to VRI. The frequency, mean VRI ± standard error (SE) for the thalassemic group were (N = 16), mean = 2.243 ± 0.111; for anemic controls (N = 9), mean = 2.374 ± 0.162; and for the controls (N = 8), mean = 2.338 ± 0.092. ANOVA test indicated a non-significant difference in mean VRI between the three groups (P value = 0.731). Multiple linear regression couldn't detect any significant association between VRI and any of the predictors including the groups. Our study did not show a significant difference in VRI between the 3 study groups. Prospective studies of larger sample size are warranted to establish DTM as a possible non-invasive tool used to evaluate vascular function in β-TI patients.

Non-invasive assessment of endothelial dysfunction: A novel method to predict severe COVID-19?

The COVID-19 pandemic caused by the SARS-CoV-2 virus has infected millions and overburdened the healthcare infrastructure globally. Recent studies show that the endothelial dysfunction caused by the virus contributes to its high morbidity and mortality. A parameter that can identify patients who will develop complications early will be valuable in patient management and reducing the burden on medical resources. An emerging technology is currently being tested to predict the cardiovascular risk via non-invasively measuring the endothelial dysfunction. This paper reviews how the assessment of endothelial dysfunction using this technology can be used as a potential parameter in the prognostication and management of COVID-19 patients.

Differential regulation of nitric oxide synthase function in aorta and tail artery from 5/6 nephrectomized rats

Chronic renal failure (CRF) is associated with hypertension and concomitant endothelial dysfunction, enhanced vasoconstriction, and nitric oxide synthase (NOS) dysfunction. Vascular function in patients is assessed in peripheral extremity arteries like the finger arteries, whereas animal studies often use the centrally located aorta. Therefore, we examined whether peripheral tail artery and aortic NOS function are differentially regulated by blood pressure in rats with CRF. Using wire myography, arterial function was assessed in 16-week-old Sprague-Dawley rats that were subjected to 5/6 nephrectomy (Nx; arterial ligation model) 8 weeks earlier or non-Nx (control) rats. In aortas from Nx rats, endothelial-dependent vasorelaxation response to acetylcholine (ACh) was blunted and there was enhancement of phenylephrine (PE)-mediated vasoconstriction. Inversely, tail arteries from Nx rats had no change in endothelial function and reduced response to PE. Studies where arterial segments were incubated with the nonspecific NOS inhibitor, L-NAME, showed that Nx reduced NOS function in the aorta but increased NOS function in tail artery for both ACh and PE responses. Furthermore, the observed alterations in NOS function in both aorta and tail artery were abolished when mean arterial blood pressure, as assessed by telemetry, was maintained at normal levels in the 5/6 Nx rats using triple therapy: hydralazine (30 mg/kg per day), hydrochlorothiazide (10 mg/kg per day), and reserpine (0.5 mg/kg per day). In conclusion, differential changes of NOS function in central versus peripheral arteries in CRF are dependent upon hypertension.

A novel technique for the assessment of preoperative cardiovascular risk: reactive hyperemic response to short-term exercise

BACKGROUND

Perioperative vascular function has been widely studied using noninvasive techniques that measure reactive hyperemia as a surrogate marker of vascular function. However, studies are limited to a static setting with patients tested at rest. We hypothesized that exercise would increase reactive hyperemia as measured by digital thermal monitoring (DTM) in association to patients' cardiometabolic risk.

METHODS

Thirty patients (58 ± 9 years) scheduled for noncardiac surgery were studied prospectively. Preoperatively, temperature rebound (TR) following upper arm cuff occlusion was measured before and 10 minutes after exercise. Data are presented as means ± SD. Statistical analysis utilized ANOVA and Fisher's exact test, with P values <0.05 regarded as significant.

RESULTS

Following exercise, TR-derived parameters increased significantly (absolute: 0.53 ± 0.95 versus 0.04 ± 0.42°C, P=0.04, and % change: 1.78 ± 3.29 versus 0.14 ± 1.27 %, P=0.03). All patients with preoperative cardiac risk factors had a change in TR (after/before exercise, ΔTR) with values falling in the lower two tertiles of the study population (ΔTR <1.1%).

CONCLUSION

Exercise increased the reactive hyperemic response to ischemia. This dynamic response was blunted in patients with cardiac risk factors. The usability of this short-term effect for the preoperative assessment of endothelial function warrants further study.