The right-to-left shunt of crocodilians serves digestion

Abstract All amniotes except birds and mammals have the ability to shunt blood past the lungs, but the physiological function of this ability is poorly understood. We studied the role of the shunt in digestion in juvenile American alligators in the following ways. First, we characterized the shunt in fasting and postprandial animals and found that blood was shunted past the lungs during digestion. Second, we disabled the shunt by surgically sealing the left aortic orifice in one group of animals, and we performed a sham surgery in another. We then compared postprandial rates of gastric acid secretion at body temperatures of 19 degrees and 27 degrees C and rates of digestion of bone at 27 degrees C. Twelve hours after eating, maximal rates of gastric acid secretion when measured at 19 degrees and 27 degrees C were significantly less in the disabled group than in sham-operated animals. Twenty-four hours postprandial, a significant decrease was found at 27 degrees C but not at 19 degrees C. For the first half of digestion, dissolution of cortical bone was significantly slower in the disabled animals. These data suggest the right-to-left shunt serves to retain carbon dioxide in the body so that it can be used by the gastrointestinal system. We hypothesize that the foramen of Panizza functions to enrich with oxygen blood that is destined for the gastrointestinal system to power proton pumps and other energy-demanding processes of digestion and that the right-to-left shunt serves to provide carbon dioxide to gastrointestinal organs besides the stomach, such as the pancreas, spleen, upper small intestine, and liver.     

Patient radiation biological risk in computed tomography angiography procedure

Computed tomography angiography (CTA) has become the most valuable imaging modality for the diagnosis of blood vessel diseases; however, patients are exposed to high radiation doses and the probability of cancer and other biological effects is increased. The objectives of this study were to measure the patient radiation dose during a CTA procedure and to estimate the radiation dose and biological effects.The study was conducted in two radiology departments equipped with 64-slice CT machines (Aquilion) calibrated according to international protocols. A total of 152 patients underwent brain, lower limb, chest, abdomen, and pelvis examinations. The effective radiation dose was estimated using ImPACT scan software. Cancer and biological risks were estimated using the International Commission on Radiological Protection (ICRP) conversion factors.The mean patient dose value per procedure (dose length product [DLP], mGy·cm) for all examinations was 437.8 ± 166, 568.8 ± 194, 516.0 ± 228, 581.8 ± 175, and 1082.9 ± 290 for the lower limbs, pelvis, abdomen, chest, and cerebral, respectively. The lens of the eye, uterus, and ovaries received high radiation doses compared to thyroid and testis. The overall patient risk per CTA procedure ranged between 15 and 36 cancer risks per 1 million procedures. Patient risk from CTA procedures is high during neck and abdomen procedures. Special concern should be provided to the lens of the eye and thyroid during brain CTA procedures. Patient dose reduction is an important consideration; thus, staff should optimize the radiation dose during CTA procedures.     

Coronary artery anomalies, detection by dual-source computed tomography angiography

In the current issue of the Netherlands Heart Journal, Zhang et al. describe the incidence of anomalous origins of the coronary arteries, demonstrated by dual-source computed tomography angiography (DSCT), in 1879 Chinese adults.     

Volumetric dynamic computed tomography angiography in the topical diagnosis of sporadic insulinomas

The authors analyzed the data of contrast-enhanced multislice spiral computed tomography (MSCT) angiography versus those of volumetric dynamic computed tomography, percutaneous and endoscopic ultrasonography, selective angiography, and arterial stimulation blood sampling in the diagnosis of sporadic insulinomas depending on the size and site of the tumor. Forty-five patients (25 women and 20 men) aged 20 to 55 years (mean age, 43.4 +/- 2.8 years) with characteristic clinical symptoms and Whipple's triad, were examined. These were found to have 45 sporadic insulinomas that were located in the head and isthmus (n = 13 (28.9%)), body (n = 19 (42.2%)), and tail (n = 13 (28.9%)). The insulinomas measured 4.0 to 10.0 mm (mean size, 6.5 +/- 2.1 mm) (n = 9), 11.0 to 20.0 mm (mean size, 13.2 +/- 2.5 mm) (n = 23), and 21.0 to 25.0 mm (mean size, 22.6 +/- 2.8 mm) (n = 13). Volumetric dynamic CT angiography increases detection rates for tumors less than 1.0 cm in size to 77.8%. It enabled insulinomas to be localized in 82.2% of cases.     

Adaptive bolus chasing computed tomography angiography: Control scheme and experimental results

In this paper, a new adaptive bolus-chasing control scheme is proposed to synchronize the bolus peak in a patient's vascular system and the imaging aperture of a computed tomography (CT) scanner. The proposed control scheme is theoretically evaluated and experimentally tested on a modified Siemens SOMATOM Volume Zoom CT scanner. The first set of experimental results is reported on bolus-chasing CT angiography using realistic bolus dynamics, real-time CT imaging and adaptive table control with physical vasculature phantoms. The data demonstrate that the proposed control approach tracks the bolus propagation well, and clearly outperforms the constant-speed scheme that is the current clinical standard.     

Semi-automatic 3D segmentation of carotid lumen in contrast-enhanced computed tomography angiography images

The atherosclerosis disease is one of the major causes of the death in the world. Atherosclerosis refers to the hardening and narrowing of the arteries by plaques. Carotid stenosis is a narrowing or constriction of carotid artery lumen usually caused by atherosclerosis. Carotid artery stenosis can increase risk of brain stroke. Contrast-enhanced Computed Tomography Angiography (CTA) is a minimally invasive method for imaging and quantification of the carotid plaques. Manual segmentation of carotid lumen in CTA images is a tedious and time consuming procedure which is subjected to observer variability. As a result, there is a strong and growing demand for developing computer-aided carotid segmentation procedures. In this study, a novel method is presented for carotid artery lumen segmentation in CTA data. First, the mean shift smoothing is used for uniformity enhancement of gray levels. Then with the help of three seed points, the centerlines of the arteries are extracted by a 3D Hessian based fast marching shortest path algorithm. Finally, a 3D Level set function is performed for segmentation. Results on 14 CTA volumes data show 85% of Dice similarity and 0.42 mm of mean absolute surface distance measures. Evaluation shows that the proposed method requires minimal user intervention, low dependence to gray levels changes in artery path, resistance to extreme changes in carotid diameter and carotid branch locations. The proposed method has high accuracy and can be used in qualitative and quantitative evaluation.     

Effects of chronic right-to-left cardiac shunt on hypoxic sensitivity of mongrel dogs

Resting ventilation (VI), blood gases, hypoxic sensitivity, and the ventilatory responses to intravenous sodium cyanide (NaCN, 100 micrograms/kg), doxapram (DOX, 500 micrograms/kg), and dopamine (DOPA, 20 micrograms/kg) were analyzed in four normal mongrel dogs (group I-N) and seven mongrel dogs with chronic (5-11 yr) right-to-left cardiac shunt (group II). The group I-N animals were also studied during steady-state isocapnic hypoxia (group I-H). The shunt procedure used for these studies produced a model for ventilatory studies during chronic shunt hypoxemia. The increases in VI per percent decrease in O2 saturation, which occurred during a four-breath N2 test, were 30, 43, and 13 ml X kg-1 X min-1 in groups I-N, I-H, and II, respectively. The decrease in hypoxic sensitivity of the group II animals, compared with groups I-N and I-H, occurred in the presence of an increase in PaCO2 from 21.9 to 26.0 Torr during the four-breath N2 test. A decrease in PaCO2 from 34.7 to 30.0 and from 33.6 to 30.4 Torr was observed in groups I-N and I-H. The response to DOX, a general analeptic agent, was greatest in group II and least in group I-N. However, the ventilatory responses to NaCN and DOPA were not sufficiently different among the three groups to suggest a difference in carotid body function as assessed by these drugs.     

Presence and extent of cardiac computed tomography angiography defined coronary artery disease in patients presenting with syncope

Background

In syncope patients, presence of coronary artery disease (CAD) is associated with poor prognosis. However, data concerning CAD prevalence in syncope patients without known cardiovascular disease are lacking. Therefore, the aim of this study was to investigate presence and extent of CAD in syncope patients.

Methods

We included 142 consecutive patients presenting with syncope at the outpatient cardiology clinic who underwent coronary computed tomography (CT) angiography. Syncope type was ascertained by two reviewers, blinded for coronary CT angiography results. Of the patients, 49 had cardiac syncope (arrhythmia or structural cardiopulmonary disease) and 93 had non-cardiac syncope (reflex [neurally-mediated], orthostatic or of unknown cause). Cardiac syncope patients were compared with matched stable chest pain patients regarding age, gender, smoking status, diabetes mellitus type 2 and systolic blood pressure.

Results

Distribution of CAD presence and extent in cardiac and non-cardiac syncope patients was as follows: 72% versus 48% any CAD; 31% versus 26% mild, 8% versus 14% moderate and 33% versus 7% severe CAD.Compared with non-cardiac syncope, patients with cardiac syncope had a significantly higher CAD presence and extent (p = 0.001). Coronary calcium score, segment involvement and stenosis score were also higher in cardiac syncope patients (p-values ≤0.004). Compared to the chest pain control group, patients with cardiac syncope showed a higher, however, non-significant, prevalence of any CAD (72% versus 63%) and severe CAD (33% versus 19%).

Conclusion

Patients with cardiac syncope show a high presence and extent of CAD in contrast to non-cardiac syncope patients. These results suggest that CAD may play an important role in the occurrence of cardiac syncope.

     

Short versus conventional hydration for prevention of kidney injury during pre-TAVI computed tomography angiography

Background

Computed tomography angiography (CTA) is required in the work-up for transcatheter aortic valve implantation (TAVI). However, CTA may cause contrast-induced acute kidney injury (CI-AKI). We hypothesised that a short (1?h, 3?ml/kg/h sodium bicarbonate) hydration protocol is not inferior to conventional (24?h, 1?ml/kg/h saline) hydration in avoiding a decline in renal function in patients with impaired renal function.

Methods and results

Single-centre randomised non-inferiority trial in patients with impaired renal function who underwent pre-TAVI CTA. Patients were randomised on a 1:1 ratio to short hydration (SHORT; 1?h sodium bicarbonate, 3?ml/kg/h) or conventional hydration (CONV; 24?h saline, 1?ml/kg/h). Outcomes included percentage change in serum creatinine until 2–6 days after CTA with a non-inferiority margin of 10% and an increase on the Borg dyspnoea scale ≥1 point. Seventy-four patients were included. Increase in creatinine was 6?µmol/l (95% CI 2.5–9.3) in the SHORT versus 2?µmol/l (95% CI-1.4 to 6.3) in the CONV arm (p?=?0.167). The percentage change was 4.6% (95% CI 2.0–7.3%) in the SHORT arm versus 2.5% (95% CI: 0.8 to 5.8%) in the CONV arm. The difference in percentage increase in creatinine between the two arms was 2.1% (95% CI: 2.0–6.2%; p-value non-inferiority: <0.001). CI-AKI and a need for dialysis were not observed. An increase of ≥1 point on the Borg scale (dyspnoea scale ranging from 1 (lowest) to 10 (highest)) was seen in 1 patient in the SHORT arm versus 5 patients in the CONV arm (2.9% vs 16.1%, p?=?0.091).

Conclusion

For patients with impaired renal function undergoing pre-TAVI CTA, a short 1?h, low-volume hydration protocol with sodium bicarbonate is not inferior to conventional 24-h, high-volume saline hydration.

     

Personalized application of three different concentrations of iodinated contrast media in coronary computed tomography angiography

No study has evaluated the impact of different iodinated contrast media on coronary contrast enhancement, using an injection protocol according to body surface area (BSA). Thus, the present study aimed to examine the usefulness and safety of personalized application of different iodine concentrations of contrast media in coronary computed tomographic (CT) angiography with a 2nd dual-source CT scanner in eliminating differences in coronary contrast enhancement based on a BSA-adapted injection protocol of contrast media. A total of 270 enrolled participants were randomly assigned to three groups: ioversol 320, ioversol 350 and iopromide 370 (n = 90 per group). The three groups were administered contrast media at a BSA-adjusted volume and flow rate with a fixed injection time of 15 seconds, and they subsequently received a 30-mL saline flush. All patients were scanned with a prospective electrocardiogram-gated protocol in a craniocaudal direction using a second-generation 128-slice dual-source CT system. The three iodinated contrast media used in coronary CT angiography exhibited similar diagnostic quality and safety. No significant differences were found in the contrast enhancement degrees, image quality scores, radiation doses and incidences of adverse effects among the three groups. The three contrast media used in coronary CT angiography with 320, 350 and 370 mg/mL iodine, respectively, have comparable diagnostic quality and safety. However, more large-scale, multinational, multi-centre and prospective trials are warranted.     

Reproducibility of right-to-left shunt quantification using transthoracic contrast echocardiography in hereditary haemorrhagic telangiectasia

Aim

Transthoracic contrast echocardiography (TTCE) is recommended for screening of pulmonary arteriovenous malformations (PAVMs) in hereditary haemorrhagic telangiectasia. Shunt quantification is used to find treatable PAVMs. So far, there has been no study investigating the reproducibility of this diagnostic test. Therefore, this study aimed to describe inter-observer and inter-injection variability of TTCE.

Methods

We conducted a prospective single centre study. We included all consecutive persons screened for presence of PAVMs in association with hereditary haemorrhagic telangiectasia in 2015. The videos of two contrast injections per patient were divided and reviewed by two cardiologists blinded for patient data. Pulmonary right-to-left shunts were graded using a three-grade scale. Inter-observer and inter-injection agreement was calculated with κ statistics for the presence and grade of pulmonary right-to-left shunts.

Results

We included 107 persons (accounting for 214 injections) (49.5% male, mean age 45.0?±?16.6 years). A pulmonary right-to-left shunt was present in 136 (63.6%) and 131 (61.2%) injections for observer 1 and 2, respectively. Inter-injection agreement for the presence of pulmonary right-to-left shunts was 0.96 (95% confidence interval (CI) 0.9–1.0) and 0.98 (95% CI 0.94–1.00) for observer 1 and 2, respectively. Inter-injection agreement for pulmonary right-to-left shunt grade was 0.96 (95% CI 0.93–0.99) and 0.95 (95% CI 0.92–0.98) respectively. There was disagreement in right-to-left shunt grade between the contrast injections in 11 patients (10.3%). Inter-observer variability for presence and grade of the pulmonary right-to-left shunt was 0.95 (95% CI 0.91–0.99) and 0.97 (95% CI 0.95–0.99) respectively.

Conclusion

TTCE has an excellent inter-injection and inter-observer agreement for both the presence and grade of pulmonary right-to-left shunts.

     

Visualisation of coronary venous anatomy by computed tomography angiography prior to cardiac resynchronisation therapy implantation

Background

The purpose of this study was to illustrate the additive value of computed tomography angiography (CTA) for visualisation of the coronary venous anatomy prior to cardiac resynchronisation therapy (CRT) implantation.

Methods

Eighteen patients planned for CRT implantation were prospectively included. A specific CTA protocol designed for visualisation of the coronary veins was carried out on a third-generation dual-source CT platform. Coronary veins were semi-automatically segmented to construct a 3D model. CTA-derived coronary venous anatomy was compared with intra-procedural fluoroscopic angiography (FA) in right and left anterior oblique views.

Results

Coronary venous CTA was successfully performed in all 18 patients. CRT implantation and FA were performed in 15 patients. A total of 62 veins were visualised; the number of veins per patient was 3.8 (range: 2–5). Eighty-five per cent (53/62) of the veins were visualised on both CTA and FA, while 10% (6/62) were visualised on CTA only, and 5% (3/62) on FA only. Twenty-two veins were present on the lateral or inferolateral wall; of these, 95% (21/22) were visualised by CTA. A left-sided implantation was performed in 13 patients, while a right-sided implantation was performed in the remaining 2 patients because of a persistent left-sided superior vena cava with no left innominate vein on CTA.

Conclusion

Imaging of the coronary veins by CTA using a designated protocol is technically feasible and facilitates the CRT implantation approach, potentially improving the outcome.