Evaluation of Staged TCAR and Cardiac Surgery or Structural Heart Intervention

Introduction: The optimal treatment strategy for patients with concomitant carotid and cardiac disease remains controversial. Transcarotid artery revascularization stenting with reversed flow protection (TCAR) has achieved results equivalent to carotid endarterectomy (CEA) in high risk patients. Methods: A retrospective review of all patients at a single center who received staged TCAR prior to cardiac intervention was performed. Results: 37 patients underwent 42 TCAR procedures prior to cardiac intervention (25 requiring open cardiac surgery and 12 requiring percutaneous intervention). There were no myocardial or neurological complications following TCAR prior to cardiac intervention. Three patients (8%) developed a neck hematoma which required evacuation. Conclusion: A staged approach to combined carotid and cardiac pathology with TCAR prior to cardiac intervention appears to be a safe and effective strategy.

Metastases can occur in cirrhotic livers with patent portal veins

Objectives Metastases are common in non-cirrhotic livers but are considered unlikely in the setting of cirrhosis. However, the degree of fibrosis in cirrhosis may vary; thus metastases may still access the liver vasculature and present as a mass in cirrhotic livers. This possibility may affect pathologists’ diagnostic algorithms when faced with a liver mass biopsy. Methods We hypothesized that metastases can occur in cirrhotic livers if fibrous remodeling is not severe or abnormal veno-arterial shunting exists to override an obstructed portal system. We searched departmental archives for cirrhotic livers with masses, categorizing fibrosis by Laennec staging: 4A = mild cirrhosis, 4B = moderate, 4 C = severe. Results Of 1453 cirrhotic livers with masses, 1429 were primary tumors and 24 were metastases (1.7 %). Of livers with metastases, most had 4A or 4B cirrhosis by Laennec staging (n = 17; 71 %). Eleven patients were evaluated by ultrasound Doppler; 2 of 5 with Laennec 4 C had reversal of portal vein flow, but all 4A & 4B patients had patent portal veins without reversed flow. Echocardiograms (13 patients) showed no ventricular or atrial septal defects or arteriovenous shunts. Conclusions Metastases are uncommon in cirrhotic livers, accounting for 1.7 % of masses. Most involved livers had mild or moderate cirrhosis (Laennec 4A/4B) and patent portal veins; however, as some Laennec 4 C cases also contained metastases, obstructed portal access may not be enough to deter metastatic access.

Numerical modeling of blood flow in the internal jugular vein with the use of computational fluid mechanics software

Objectives To determine the site and nature of altered hemodynamics in pathological internal jugular veins. Method With the use of computational fluid mechanics software we simulated blood flow in 3 D models of the internal jugular veins that exhibited different morphologies, including nozzle-like strictures in their upper parts and valves in the lower parts. Results In a majority of models with nozzle-like strictures, especially those positioned asymmetrically, abnormal flow pattern was revealed, with significant flow separation and regions with reversed flow. Abnormal valves had no significant impact on flow in a case of already altered flow evoked by stricture in upper part of the vein. Conclusions In our jugular model, cranially-located stenoses, which in clinical practice are primarily caused by external compression, cause more significant outflow impact respect to endoluminal defects and pathological valves located more caudally.

Impact of Rotational Speed on Turbocharger Compressor Surge Through Particle Image Velocimetry1

Stereoscopic particle image velocimetry is used to characterize the variation of the turbocharger compressor inlet velocity field as a function of rotational speed, with an emphasis on surge. While the velocity magnitudes at choke or mild surge increased with rotational speed, the velocity profiles remained qualitatively similar. The variation in deep surge flow field with shaft speed, however, was more substantial. At 80 krpm, the overall flow field was comparable at different time instances (at different points on the surge cycle): the core flow near the duct center was always directed into the impeller, whereas reversed flow occupied an annular region near the periphery in nearly all time instances. However, at 140 krpm, while the negative flow rate (cross-sectional average flow is directed out of the inducer back into the inlet duct) portion of the surge cycle was still similar to the overall surge flow field at 80 krpm, over a substantial part of the positive flow rate (cross-sectional average flow is directed into the impeller) portion of the surge cycle, there was no sign of reversed flow within the visualization domain. As the rotational speed was increased, the surge loop (obtained by combining the particle image velocimetry (PIV) and pressure transducer data) extended over a wider portion of the compressor map with higher maximum (positive) and minimum (negative) flow rates, along with higher amplitude pressure fluctuations. The mean amplitude of mass flow rate and pressure ratio fluctuations at deep surge increased in nearly a quadratic fashion with rotational speed.

Particle Image Velocimetry As Applied to Inlet Flow Field of a Turbocharger Compressor at Varying Rotational Speeds With Emphasis on Surge

Turbocharger surge remains an area of concern for the automotive industry as it limits the permissible operating range on the compressor map, while also adversely impacting the compressor’s pressure rise, efficiency, and acoustics. The present study uses Stereoscopic Particle Image Velocimetry (SPIV) to investigate the flow field at the inlet of an automotive turbocharger compressor without a recirculating channel. Experiments were carried out at four different speeds, including 80, 100, 120, and 140 krpm, which represent a substantial portion of the compressor map. The mass flow rates investigated ranged from choke to deep surge, thus spanning the entire mass flow regime at each rotational speed. The current work aims to characterize how the compressor inlet velocity field varies with rotational speed, with a specific emphasis on surge. The qualitative nature of the flow field (radial dependence of axial and tangential velocity profiles), over the choke to mild surge range, was observed to be nearly independent of rotational speed for comparable operating conditions (for example, comparison of mild surge at different rotational speeds). A quantitative comparison of the velocity profiles at the choke or mild surge operating points showed an increase in the velocity magnitudes with increasing rotational speed. The flow field at deep surge, however, was observed to change substantially from 80 krpm to 140 krpm. At 80 krpm, the character of the flow field at different times (at different points on the surge cycle) was observed to be similar: the core flow near the center of the duct was always directed into the impeller, whereas the reversed flow occupied an annular region near the periphery in nearly all time instances. However, as the rotational speed was increased to 140 krpm, the variation in the flow field at different instances within a deep surge cycle increased. At 140 krpm, the negative flow rate (where the cross-sectional average flow is directed out of the inducer back into the inlet duct) portion of the surge cycle was still similar to the overall surge flow field at 80 krpm, but over a substantial part of the positive flow rate (cross-sectional average flow is directed into the impeller) portion of the surge cycle, there was no sign of reversed flow within the visualization domain. As the rotational speed was increased, the surge loop (obtained by combining the PIV and pressure transducer data) extended over a wider portion of the compressor map with higher maximum (positive) and minimum (negative) flow rates, along with higher amplitude pressure fluctuations. The mean amplitude of mass flow rate and pressure ratio fluctuations at deep surge increased in nearly a quadratic fashion with rotational speed. The deep surge frequency did not change substantially over the range of rotational speeds examined in this study.

Anastomosis of dual renal transplant veins

As there is usually considerable overlap in the renal venous drainage, it is often possible to ligate supernumerary transplant renal veins in order to simplify the implantation procedure. Nonetheless, decisions about whether to implant multiple veins can be difficult and are usually made subjectively. Here, we describe the use of intraoperative Doppler ultrasound as an adjunct to decision-making when there are two renal veins and a novel technique for the sequential anastomosis of dual veins. The kidney was reperfused after anastomosis of the main renal vein with the second vein clamped. On-table Doppler ultrasound demonstrated reversed flow in diastole indicating that the second renal vein also needed to be anastomosed. By clamping the external iliac vein inferior to the first venous anastomosis it was possible to complete the lower polar renal vein anastomosis to the external iliac vein without interrupting the perfusion of the kidney.