Transit Time Flowmetry Research Articles

Impact of Suturing Techniques on Microvascular Anastomosis Maturation.

INTRODUCTION Microvascular anastomosis using interrupted suture is a widely accepted standard technique. Continuous suture is less common due to the presumption that its firmness can negatively affect anastomosis maturation. The purpose of this study was to determine whether the use of continuous suture allows maturation of the microanastomosis site. MATERIAL AND METHODS A rat common carotid artery (CCA) end-to-end microanastomosis model was utilized, with 19 Long-Evans rats in the interrupted sutures group and 13 in the continuous suture group. Immediate blood flow of the operated and contralateral intact CCAs was compared before clamping, at the completion of the anastomosis and after 14 days. Quantitative transit time flowmetry measurement and histological examination were employed. RESULTS Initial blood flow in both intact CCAs was similar across all animals (p = .004). In the interrupted suture group, median anastomosis blood flow was 88.9% of the contralateral CCA blod flow, with a median suture time of 46 minutes. After two weeks, blood flow increased to 96.1%. In the continuous suture group, median anastomosis blood flow was 88.3% of the contralateral CCA blood flow, with a median suture time of 30 minutes. After two weeks, blood flow increased to 100.0%. The reduction in suture time achieved with continuous suture was 34.8% (p < .001). Histological examination confirmed scar maturity. CONCLUSIONS The maturation rates of continuous and interrupted suture microanastomosis were comparable in our study, implying that concerns about the suture restricting maturation may be unwarranted. Additional finding is the potential for a reduction in microanastomosis time when using the continuous suture technique.

EARLY RESULTS OF MINIMALLY INVASIVE CORONARY ARTERY BYPASS GRAFTING

Abstract Coronary artery bypass grafting (CABG) is the benchmark in elective revascularization for Coronary Artery Disease (CAD), particularly for complex or multivessel CAD, left main coronary involvement, diabetes, or impaired heart function. Traditional CABG, via median sternotomy using cardiopulmonary bypass (CPB), has limitations like CPB–related morbidity and sternal complications. Alternatives like Minimally Invasive Cardiac Surgery (MICS CABG) and Hybrid Revascularization (HR) aim to address these drawbacks. We present a series of 215 consecutive patients (mean age 67±9 years, 27.9% females, EuroSCORE II 1.5±1.3%) between 2017–2023 who underwent elective minimally invasive surgical revascularization. Among the cohort, 164 (76.3%) had Minimally Invasive Direct Coronary Artery Bypass (MIDCAB) via anterolateral left mini–thoracotomy (ALMT) at the fifth intercostal space (IS), with 140 (85.4%) receiving a single left internal thoracic artery (LITA) graft to the left anterior descending (LAD) artery and 24 (14.6%) an additional distal anastomosis. Thirty–four (20.7%) had HR via percutaneous coronary intervention (PCI) on the right coronary artery (RCA). Of the total cohort, 35/215 patients (16.3%) underwent multivessel MICS CABG via ALMT, with mean 2.3±0.5 distal anastomoses using LITA, right ITA, radial artery, or saphenous vein. Heart manipulation was via a subxiphoid device. Four MICS CABG patients (11.4%) had HR. More than half of MICS CABG cases were performed with planned peripheral CPB, without cross–clamping the Aorta. Of the total cohort, 16/215 patients (7.4%) received MICS CABG in an endoscopic fashion, using 3D thoracoscopy for LITA and RITA harvesting via bilateral ports in the 2nd, 3rd, and 4th IS, employing peripheral CPB and aortic clamping by Chitwood clamp at the second IS, with cardioplegia delivery via a 4 cm right anterior MT. Distal anastomoses were performed via left anterior MT, with easy subxiphoid manipulation of the emptied heart. Transit time flowmetry was used in all cases. Conversion to sternotomy was needed in 3 cases, all were MIDCAB. Thirty–day mortality was 1.4%, median ventilation was 4 [2–5] hours, and Intensive Care Unit–stay was 1 [1–2] days. All patients received graft evaluation via computerized tomography before hospital discharge. Mean follow–up was 2.9±1.9 years (max 5 years), with no deaths and 4 (1.9%) requiring follow–up PCI. MICS CABG is a promising future technique for heart revascularization by dedicated teams.

Intraoperative Blood Flow Analysis of Free Flaps with Arteriovenous Loops for Autologous Microsurgical Reconstruction

Background: Arteriovenous (AV) loops help to overcome absent or poor-quality recipient vessels in highly complex microvascular free flap reconstruction cases. There are no studies on blood flow and perfusion patterns. The purpose of this study was to evaluate and compare intraoperative hemodynamic characteristics of AV loops followed by free tissue transfer for thoracic wall and lower extremity reconstruction. Methods: this prospective clinical study combined Transit-Time Flowmetry and microvascular Indocyanine Green Angiography for the assessment of blood flow volume, arterial vascular resistance and intrinsic transit time at the time of AV loop construction and on the day of free flap transfer. Results: A total of 11 patients underwent AV loop creation, of whom five required chest wall reconstruction and six required reconstruction of the lower extremities. In seven of these cases, the latissimus dorsi flap and in four cases the vertical rectus abdominis myocutaneous (VRAM) flap was used as a free flap. At the time of loop construction, the blood flow volume of AV loops was 466 ± 180 mL/min, which increased to 698 ± 464 mL/min on the day of free tissue transfer (p &gt; 0.1). After free flap anastomosis, the blood flow volume significantly decreased to 18.5 ± 8.3 mL/min (p &lt; 0.001). There was no significant difference in blood flow volume or arterial vascular resistance between latissimus dorsi and VRAM flaps, nor between thoracic wall and lower extremity reconstruction. However, a significant correlation between the flap weight and the blood flow volume, as well as to the arterial vascular resistance, was found (p &lt; 0.05). Conclusion: This is the first study to perform intraoperative blood flow and hemodynamic measurements of AV loops followed by free tissue transfer. Our results show hemodynamic differences and contribute to deeper understanding of the properties of AV loops for free flap reconstruction.

Transit-time flowmetry measurement features of coronary bypass grafts after multiple percutaneous coronary interventions

The functionality of coronary bypass grafts after surgical myocardial revascularization in patients with coronary heart disease directly depends on the state of the target coronary arteries. In the presence of widespread and diff use atherosclerotic lesions or microcirculatory dysfunctions, a high frequency of coronary bypass dysfunctions is noted in the near future. In some cases, shunt dysfunction can lead to severe hemodynamic instability, accompanied by acute circulatory disorders.Aim: To assess the function of coronary bypass grafts during myocardial revascularization using the method of ultrasonic flowmetry in patients with and without a history of multiple percutaneous coronary interventions (PCI).Material and methods. The retrospective study included 47 patients who underwent coronary artery bypass surgery. A total of 145 coronary bypass grafts were performed. All patients were divided into 2 groups. Group 1 (PCI group) included patients after multiple previous PCI (n = 25; 74 coronary bypass grafts), group 2 (without PCI) included patients without previous PCI (n = 22; 71 coronary bypass grafts). All patients underwent intraoperative ultrasonic flowmetry of coronary bypass grafts using the VeriQ system (Medistim, Norway).Results. When analyzing the status of coronary bypass grafts in patients after multiple PCI, a significantly low mean volumetric blood flow rate was noted (29.5 ± 8.3 ml/min and 48.2 ± 11.6 ml/min, respectively, p = 0.0001) and lower diastolic filling (55.2 ± 8.2% and 71.9 ± 7.1%, p = 0.0001). Also in the group of patients after multiple PCI, there were 2 (2.7%) cases of revision of the distal anastomosis due to a high pulsatile index and low volumetric blood flow velocity. However, no such events were noted in the group without PCI.Conclusions. Previous percutaneous coronary interventions are compromising factors for the state of the coronary bed, which reduces the functional status of coronary bypass grafts and may increase the perioperative risk of surgical myocardial revascularization.

Norepinephrine preserved flap blood flow compared to phenylephrine in free transverse rectus abdominis myocutaneous flap breast reconstruction surgery: A randomized pilot study

Vasopressors are used in up to 85% of cases during free flap surgery. However, their use is still debated with concerns of vasoconstriction-related complications, with rates up to 53% in minor cases. We investigated the effects of vasopressors on flap blood flow during free flap breast reconstruction surgery. We hypothesized that norepinephrine may preserve flap perfusion better than phenylephrine during free flap transfer. A randomized pilot study was performed in patients undergoing free transverse rectus abdominis myocutaneous (TRAM) flap breast reconstruction. Patients with peripheral artery disease, allergies to study drugs, previous abdominal operations, left ventricular dysfunction, or uncontrolled arrhythmias were excluded. Twenty patients were randomized to receive either norepinephrine (0.03-0.10µg/kg/min) or phenylephrine (0.42-1.25µg/kg/min) (each n=10) to maintain a mean arterial pressure of 65-80mmHg. The primary outcome was differences in mean blood flow (MBF) and pulsatility index (PI) of flap vessels after anastomosis measured using transit time flowmetry in the two groups. Secondary outcomes included flap loss, necrosis, thrombosis, wound infection, and reoperation within 7 days postoperatively. After anastomosis, MBF showed no significant change in the norepinephrine group (mean difference, -9.4±14.2mL/min; p=0.082), whereas it was reduced in the phenylephrine group (-7.9±8.2mL/min; p=0.021). PI did not change in either group (0.4±1.0 and 1.3±3.1 in the norepinephrine and phenylephrine groups; p=0.285 and 0.252, respectively). There were no differences in secondary outcomes between the groups. During free TRAM flap breast reconstruction, norepinephrine seems to preserve flap perfusion compared to phenylephrine. However, further validation studies are required.

Blood flow characteristics of the bilateral internal thoracic artery: implications of optimal graft configuration for coronary artery bypass grafting to maximize blood supply.

There is controversy regarding which internal thoracic artery (ITA) should be anastomosed to the left anterior descending artery (LAD). Here, we propose an optimal graft design based on measurement of blood flow in the ITA. Sixty-one patients (53 men, median age 68 [62-75] years) undergoing first elective coronary artery bypass grafting were enrolled. Fifty-seven left ITAs (LITAs) and 28 right ITAs (RITAs) were harvested in either a semi-skeletonized manner using a harmonic scalpel covered with papaverine-soaked gauze (group-A, n = 45) or a fully skeletonized manner using electrocautery with intraluminal papaverine injection (group-B, n = 41). Free flow of 33 ITAs was measured after pharmacological dilatation and in situ ITA-LAD flow was measured in 59 patients by transit-time flowmetry. RITA and LITA free flow were 147.0 [87.8-213.0] mL/min and 108.0 [90.0-144.0] mL/min, respectively (P = 0.199). The group-B had significantly higher ITA free flow (135.0 [102.0-171.0] mL/min) than group-A (63.0 [36.0-96.0] mL/min, P = 0.009). In 13 patients with bilateral ITA harvesting, free flow of the RITA (138.0 [79.5-204.0] mL/min) was also significantly higher than the LITA (102.0 [81.0-138.0] mL/min, P = 0.046). There was no significant difference between RITA and LITA flow anastomosed to the LAD. The group-B had significantly higher ITA-LAD flow (56.5 [32.3-73.6] mL/min) than group-A (40.9 [20.1-53.7] mL/min, P = 0.023). RITA provides significantly higher free flow than LITA but similar blood flow to the LAD. Full skeletonization with intraluminal papaverine injection maximizes both free flow and ITA-LAD flow.

Personalized surgical planning for coronary bypass graft configurations using patient-specific computational modeling to avoid flow competition in arterial grafts.

Flow competition between coronary artery bypass grafts (CABG) and native coronary arteries is a significant problem affecting arterial graft patency. The objectives of this study were to compare the predictive hemodynamic flow resulting from various total arterial grafting configurations and to evaluate whether the use of computational fluid dynamics (CFD) models capable of predicting flow can assist surgeons to make better decisions for individual patients by avoiding poorly functioning grafts. Sixteen cardiac surgeons declared their preferred CABG configuration using bilateral internal mammary and radial arteries for each of 5 patients who had differing degrees of severe triple vessel coronary disease. Surgeons selected both a preferred 'aortic' strategy, with at least one graft arising from the ascending aorta, and a preferred "anaortic" strategy which could be performed as a "no-aortic touch" operation. CT coronary angiograms of the 5 patients were coupled to CFD models using a novel flow solver "COMCAB." Twelve different CABG configurations were compared for each patient of which 4 were "aortic" and 8 were "anaortic." Surgeons then selected their preferred grafting configurations after being shown predictive hemodynamic metrics including functional assessment of stenoses (instantaneous wave-free ratio; fractional flow reserve), transit time flowmetry graft parameters (mean graft flow; pulsatility index) and myocardial perfusion. A total of 87.5% (7/8) of "anaortic" configurations compared to 25% (1/4) of "aortic" configurations led to unsatisfactory grafts in at least 1 of the 5 patients (P = 0.038). The use of the computational models led to a significant decrease in the selection of unsatisfactory grafting configurations when surgeons employed "anaortic" (21.25% (17/80) vs. 1.25% (1/80), P < 0.001) but not "aortic" techniques (5% (4/80) vs. 0% (0/80), P = 0.64). Similarly, there was an increase in the selection of ideal configurations for "anaortic" (6.25% (5/80) vs. 28.75% (23/80), P < 0.001) but not "aortic" techniques (65% (52/80) vs. 61.25% (49/80), P = 0.74). Furthermore, surgeons who planned to use more than one unique "anaortic" configuration across all 5 patients increased (12.5% (2/16) vs. 87.5% (14/16), P<0.001). "COMCAB" is a promising tool to improve personalized surgical planning particularly for CABG configurations involving composite or sequential grafts which are used more frequently in anaortic operations.

Evaluation of anastomosis quality with intraoperative transit time flowmeter in minimally invasive multi-vessel coronary artery bypass grafting via left anterior mini-thoracotomy.

In this study, we aimed to describe our intraoperative transit-time flow measurement results as an integral component of the operation and evaluate the graft patency and anastomosis quality in patients who underwent minimally invasive multi-vessel coronary artery bypass grafting via mini-thoracotomy. Between May 2020 and September 2021, a total of 45 consecutive patients (32 males, 13 females; mean age: 51.2±8.6 years; range, 41 to 72 years) who underwent minimally invasive multi-vessel coronary artery bypass grafting via left anterior mini-thoracotomy were retrospectively analyzed. We used the technique of intraoperative transit-time flowmetry in all patients. The patients were operated under cardiopulmonary bypass. A saphenous vein graft was used in all anastomoses, except for the left internal thoracic artery. The mean left internal mammary artery flow rate was 36.2±14.1 mL/min, mean flow rate of the diagonal grafts was 48.2±13.1 mL/min, mean flow rate of the circumflex grafts was 41.2±21.1 mL/min, and mean flow rate of the right coronary artery grafts was 52.2±11.3 mL/min. Wave patterns and flow parameters of all grafts were normal in the intraoperative measurements, since the pulsatility index values in all anastomoses were within normal limits. The operation was completed after anastomotic openings and graft patency were ensured. The use of an intraoperative flowmeter to show the graft patency and anastomosis quality gives confidence both to the surgeon and the patient. In multi-vessel coronary artery bypass grafting via mini-thoracotomy, anastomosis quality can be evaluated well with this technique.

Validity of Ipsilateral Internal Mammary Coronary Artery Bypass Graft of Arteriovenous Fistula

In coronary artery bypass grafting (CABG) for haemodialysis patients, arteriovenous fistula can reduce blood flow from the internal mammary artery (IMA) graft. The purpose of this study was to delineate the rationale of ipsilateral IMA grafting to the arteriovenous fistula by assessing graft flow and patency. The clinical records of 139 haemodialysis patients who underwent off-pump CABG, including IMA grafting to the left anterior descending artery (LAD) between April 2007 and December 2018, were retrospectively reviewed. Clinical outcomes and transit-time flowmetry results of IMA to LAD bypass grafts during off-pump CABG and postoperative angiography were examined. An ipsilateral IMA to the arteriovenous fistula (Ipsi-IMA) was used in 89 patients, and a contralateral IMA to the arteriovenous fistula (Contra-IMA) was used in 50 patients and no hospital deaths occurred. The mean graft flow and angiographic patency rate did not differ between the Ipsi-IMA and Contra-IMA groups. In patients with 51 to 90% stenosis of LAD, there was no significant difference in the mean graft flow. In comparison, in the patients with 91 to 100% stenosis of LAD, the mean graft flow in the Ipsi-IMA group was significantly lower than that in the Contra-IMA group (p=0.03). Kaplan-Meier analyses showed a 5-year survival rate of 57.6% for Ipsi-IMA and 64.8% for Contra-IMA (p=0.47). In the revascularisation of the LAD, the graft patency rate of the Ipsi-IMA was not inferior to that of the Contra-IMA. However, when the LAD has 91 to 100% stenosis, a Contra-IMA to arteriovenous fistula may be beneficial in terms of sufficient flow capacity.

Assessment of liver blood flow regulation mechanism by ultrasound

The constancy of hepatic blood flow is important for several homeostatic roles. This paper reviews studies related to liver blood flow regulation mechanism. The liver has mechanism maintain a constant hepatic blood flow and compensate for portal flow changes. A reduction in portal flow leads to reduced intrahepatic distending pressure, resulting the hepatic arterial buffer response causes dilation of the hepatic artery, thus buffering the Portal flow change. This mechanism is exclusive to this specific vascular bed and offer a great illustration of multiple integrative regulation of a significant homeostatic organ. Ultrasound provides noninvasive accurate information on the liver hemodynamic and assess the flow in the hepatic artery and the portal vein specially diameter of vessels. Aim: The aim of this study was to evaluate the dual hepatic blood supply in normal individual and compared altered in the hepatic artery buffer response with chronic hepatic diseases. Materials and methods: The current review focuses on researches that evaluate the mechanisms involved in maintaining a steady hepatic arterial buffer response (HBF), such as the impact of portal blood flow on hepatic artery flow, or assessing the intrinsic regulation of hepatic arterial blood flow by measure the hepatic arterial buffer response intraoperative in patients with or without cirrhosis using an ultrasound transit-time flowmetry, or by duplex ultrasound, Moreover studies to understand the role of hepatic flow in liver atrophy.

Abstract P1017: Tissue Engineered Human Acellular Blood Vessels For Coronary Artery Bypass Grafting

Objective: Conduit for coronary artery bypass grafting (CABG) can be limited due to poor quality or prior removal of saphenous veins. A human acellular vessel (HAV) bioengineered from vascular cells and then decellularized for implantation may provide a readily available, off-the-shelf conduit for CABG. Here we evaluate the use of small diameter HAV for CABG in a non-human primate model. Methods: Adult male baboons (n=7; 26.8 - 37.0 kg) were imaged by left heart catheterization and computed tomography angiography. CABG was performed using a 3.5 mm diameter HAV to the left anterior descending (LAD) or right coronary artery (RCA) via sternotomy with cardiopulmonary bypass. The proximal coronary artery was ligated to prevent competitive flow and graft transit time flowmetry (TTFM) was assessed after implant. Angiography at 2 weeks, 1, 3, and 6 months evaluated graft patency and heart function. HAVs explanted at 6 months were assessed by immunohistochemistry for host cellular response and remodeling. Results and Conclusion: Baboons underwent CABG using a 3.5 mm HAV from the ascending aorta to the LAD (n=2) or RCA (n=5). The diminutive LAD led to early graft loss due to size mismatch and poor runoff. HAV bypass to the dominant RCA (TTFM: 22 ± 7.7 mL/min) resulted in sustained graft patency for up to 6 months post-implantation. HAV explant histology revealed infiltration of multiple host cell populations with formation of a neoadventitial layer and evidence of luminal endothelization. HAV conduits retained structural integrity with no evidence of mechanical failure throughout the study. These results demonstrate that tissue-engineered HAVs may provide an off-the-shelf conduit for CABG.

Transit-Time Flow Measurement and Outcomes in Coronary Artery Bypass Graft Patients

Transit-time flowmetry (TTFM) is commonly used during coronary artery bypass grafting for intraoperative graft assessment. This study aimed to investigate whether TTFM values were predictive of graft failure and major adverse cardiac and cerebrovascular events (MACCEs). Between 2011 and 2018, 1933 patients with 3-vessel coronary artery disease who underwent off-pump coronary artery bypass were retrospectively analyzed. Among them, 1288 sequential venous grafts in 538 consecutive patients were measured using TTFM's 2 parameters, pulsatility index (PI) and flow (mL/min). The anastomoses were divided in the 3 groups depending on the anastomotic site: group A, first side-to-side anastomoses (n=538), group B; second side-to-side (n=212), group C; end-to-side (n=538). MACCEs were related to TTFM. The mean clinical follow-up time was 64.8 ± 21.2 months. Postoperative graft patency was confirmed with multi-slice computed tomography or coronary angiography (follow-up interval: 64.8 ± 50.4 and 27.8 ± 20.5 months based on the date of examination). The 5-year survival rate was 93.7%. The mean graft flow was 59.1 ± 31.3, 41.0 ± 25.2, and 38.9 ± 22.8 mL/minute, and the PI was 2.2 ± 1.3, 2.5 ± 3.4, and 2.4 ± 2.5, in groups A, B, and C, respectively. Graft failure occurred in 23/1055 (2.2%) anastomoses. The 5-year MACCE rate was 6.9% (37/538 patients). Kaplan-Meier analysis revealed that graft patency was significantly lower in low MGF (p=0.044) and high PI (p < 0.001). Multivariable logistic analysis showed that high PI (>5; HR 2.276; 95%CI 2.188-2.406, p < 0.001) was an independent risk factor for MACCEs. The cutoff values for PI of sequential grafts were 3.65, 3.55, and 3.17 in groups A, B, and C, respectively for the prediction of MACCE. A high PI predicts more predictive poor outcomes of sequential venous grafts after surgery than the low mean graft blood flow.

Intraoperative Blood Flow Analysis of DIEP vs. ms-TRAM Flap Breast Reconstruction Combining Transit-Time Flowmetry and Microvascular Indocyanine Green Angiography.

Background: Vascular patency is the key element for high flap survival rates. The purpose of this study was to assess and compare the blood flow characteristics of deep inferior epigastric perforator (DIEP) and muscle-sparing transverse rectus abdominis musculocutaneous (ms-TRAM) flaps for autologous breast reconstruction. Methods: This prospective clinical study combined Transit-Time Flowmetry and microvascular Indocyanine Green Angiography for the measurement of blood flow volume, vascular resistance, and intrinsic transit time. Results: Twenty female patients (mean age, 52 years) received 24 free flaps (14 DIEP and 10 ms-TRAM flaps). The mean arterial blood flow of the flap in situ was 7.2 ± 1.9 mL/min in DIEP flaps and 11.5 ± 4.8 mL/min in ms-TRAM flaps (p < 0.05). After anastomosis, the mean arterial blood flow was 9.7 ± 5.6 mL/min in DIEP flaps and 13.5 ± 4.2 mL/min in ms-TRAM flaps (p = 0.07). The arterial vascular resistance of DIEP flaps was significantly higher than that of ms-TRAM flaps. The intrinsic transit time of DIEP flaps was 52 ± 18 s, and that of ms-TRAM flaps was 33 ± 11 s (p < 0.05). The flap survival rate was 100%. One DIEP flap with the highest intrinsic transit time (77 s) required surgical revision due to arterial thrombosis. Conclusion: In this study, we established the blood flow characteristics of free DIEP and ms-TRAM flaps showing different blood flow rates, vascular resistances, and intrinsic transit times. These standard values will help to determine the predictive values for vascular compromise, hence improving the safety of autologous breast reconstruction procedures.

Intraoperative Assessment of Coronary Resistances: A New Quality Marker and Potential Tool to Predict Early Graft Failure after Coronary Artery Bypass Grafting?

Intraoperative assessment of graft patency is pivotal for successful coronary revascularization. In the present study we aimed to propose a new, easy to perform tool to assess anastomotic quality intraoperatively, and to investigate its potential reliability in predicting early graft failure. Intraoperative graft flowmetry of 63 consecutive patients undergoing CABG were prospectively collected. Transit time flowmetry and its derivatives were recorded. Coronary resistances were calculated according to Hagen–Poiseuille equation both during cardioplegic arrest and after withdrawal from cardiopulmonary bypass. Angiographic evidence of graft occlusion at follow-up was cross-checked with intraoperative recordings. After a mean follow-up of 10.4 ± 6.0 months, 22 grafts were studied, and occlusion was documented in five (22.7%). Occluded grafts showed lower flows and higher resistances recorded during aortic cross-clamping. Coronary resistances, recorded during aortic cross-clamping, greater than 2.0 mmHg/mL/min, showed a sensitivity of 80% and a specificity of 100% to predict graft failure. We propose the routine recording of coronary resistances during aortic cross-clamping as an additional tool to overcome the acknowledged limitation of TTF to predict graft occlusion at 1 year.

Importance of Intraoperative Detection of Graft Patency by Using Transit Time Flowmetry and Its Impact on Revascularization of the Myocardium

Abstract Background Coronary artery bypass surgery (CABG) has contributed to an increase in survival, quality of life and life expectancy. The anastomotic quality and graft patency is directly associated with both early and long-term clinical results after CABG. It is a complication that can lead to refractory angina, myocardial infarction, arrhythmias, and even mortality. Objectives This study was aiming to evaluate the effect of use of TTFM on the outcome of CABG operations and it was carried out on 100 patients and examined 282 grafts, we use inotropic agents to maintain the systolic pressure at 90- 100 mmHg if the blood pressure was lower than that limit. Patients and Methods An observational exploratory study was carried on 100 patients operated in Police authority hospitals, cardiothoracic surgery department. The study period of the study was 6 months, study population: The included population will be patients with Coronary Artery Disease (CAD) undergoing Coronary Artery Bypass Grafting (CABG) surgery. Results TTFM data was described as two main readings which are MF in ml/min (mean flow), PI (pulsatility index) and it was measured for the all types of the grafts. In MF it was the highest in AO-OM system (34.5 ± 18.46) followed by LIMA- LAD system (33.0 ± 19.65) then AO-Diagonal (31.0 ± 26.38) and lastly AO-RCA(29.50 ± 32.22). For the PI the lowest measurements was 0.8 and it was for both LIMA to LAD and then 1.2 for AO-OM system and 1.4 for AO-DIAG system and 1.8 for AO-RCA system. The most important finding in this study which represents the usefulness of the usage of TTFM is how much grafts needed to be revised according to the grafts measurements and it was 14 grafts in 14 patients (one grafts for each patient) among 100 patients which account for 14%. Conclusion Regarding the other studies that compare the TTEM with other ways for detection of graft patency, they prefer the TTFM due to: TTFM is easy to use, accurate and relatively inexpensive, TTFM helps prevent missed technical surgical errors in distal and proximal anastomosis, it has shown that TTFM improved outcome in many situations, TTFM provides excellent documentation of the surgical outcome and allows for better understanding of procedural complications.

Reduction in Hindquarter Vascular Resistance Supports 5-HT7 Receptor Mediated Hypotension.

The 5-HT7 receptor is the primary mediator of both the acute (<hours) and chronic (day-week) decreases in mean arterial pressure (MAP) during low dose 5-HT infusion in rats. Previous data show the hypotensive response during chronic 5-HT infusion is due to a decrease total peripheral resistance (TPR) and specifically splanchnic vascular resistance. We hypothesized that changes in vascular resistance in both the splanchnic and skeletal muscle vascular beds are critical to the cardiovascular effects mediated by the 5-HT7 receptor. Systemic and regional hemodynamic data were collected in conscious and anesthetized male rats using radiotelemetry, vascular catheters and transit-time flowmetry. Reversible antagonism of the 5-HT7 receptor was achieved with the selective antagonist SB269970 (33 μg/kg, iv). From the very beginning and throughout the duration (up to 5 days) of a low dose (25 μg/kg) infusion of 5-HT, TPR, and MAP were decreased while cardiac output (CO) was increased. In a separate group of rats, the contribution of the 5-HT7 receptor to the regional hemodynamic response was tested during 5-HT-induced hypertension. The decrease in MAP after 24 h of 5-HT (saline 83 ± 3 vs. 5-HT 72 ± 3 mmHg) was associated with a significant decrease in skeletal muscle vascular resistance (saline 6 ± 0.2 vs. 5-HT 4 ± 0.4 mmHg/min/mL) while splanchnic vascular resistance was similar in 5-HT and saline-treated rats. When SB269970 was administered acutely, MAP and skeletal muscle vascular resistance rapidly increased, whereas splanchnic resistance was unaffected. Our work suggests the most prominent regional hemodynamic response to 5-HT7 receptor activation paralleling the fall in MAP is a decrease in skeletal muscle vascular resistance.

Transit Time Flowmetry and Vein Size Are Predictive of Arteriovenous Fistula Maturation

BackgroundThis study aimed to assess the effect of vessel size and flow characteristics on the maturation of autogenous radiocephalic arteriovenous fistulae (RCAVFs).MethodsWe retrospectively reviewed records of patients undergoing RCAVF creation at a single medical center from January 2013 to December 2019. Operative variables were compared between patients whose fistulae matured and those whose fistulae failed to mature.ResultsOverall, 152 patients (33 of whom were women) with a mean age of 62.6±13.6 years underwent RCAVF creation; functional maturation was achieved in 123. No statistically significant differences were observed between patients in whom maturation was or was not achieved in terms of the following variables: female sex (20.3% vs. 25.0%), radial artery size (2.5 vs. 2.4 mm), and pulsatility index (0.69 vs. 0.62). Low intraoperative transit time flowmetry (TTF; 150.4 vs. 98.1 mL/min) and small vein size (2.4 vs. 2.0 mm) were associated with failure of maturation. The best cutoff diameter for RCAVF TTF and cephalic vein size were 105 mL/min and 2.45 mm, respectively.ConclusionIn patients who undergo RCAVF creation, vein diameter on preoperative ultrasonography and intraoperative TTF are predictors of functional maturation. We identified an intraoperative TTF cutoff value that can be used for intraoperative decision-making.

Clinical and Radiological Outcomes of Intracranial Aneurysm Clipping Aided by Transit Time Flowmetry

Since the International Subarachnoid Aneurysm Trial, coiling has been favored over clipping for intracranial aneurysms, resulting in selection of increasingly complex aneurysm configurations for clipping. We present the outcomes of clipping of aneurysms not suitable for coiling, with transit time flowmetry technology to aid monitoring of intraoperative flow. All consecutive patients surgically treated for intracranial aneurysms were included. We assessed intraoperative arterial blood flow in relation to postoperative ischemia and unfavorable outcome (modified Rankin Scale score 3-6), along with radiological occlusion rate, at 6 months and 1 year after surgery. Mortality at 1 year was 7.9%, with a 21.6% rate of an unfavorable outcome. Almost all (96.1%) of patients with unruptured aneurysms had an favorable outcome at 1 year, compared with 71.9% of patients with aneurysmal subarachnoid hemorrhage. Postoperative computed tomography imaging showed an 86.7% occlusion rate and a 7.5% rate of clip-related ischemia. Flow <40% of baseline significantly predicted clip-related ischemia (odds ratio [OR], 5.14; 95% confidence interval [CI], 1.41-8.4; P= 0.012). Clip reposition aided by transit time flowmetry resulted in restored flow >50% above baseline flow in 85.7% of aneurysms. Less than 50% flow from baseline was an independent predictor of unfavorable outcome (OR, 3.85; 95% CI, 1.6-9.0; P= 0.001), along other risk factors. In this study of clinical and radiological outcomes of surgically treated cerebral aneurysms not suitable for unassisted coiling, we showed positive results for these challenging aneurysms, aided by transit time flowmetry as a valuable tool, providingquantitative measurements of arterial blood flow to help achieve optimal clip placement and minimizing aneurysm residuals that may be sites of rebleeding. Adequate flow, defined as ≥50% of baseline, greatly reduces the risk of unfavorable outcome.

Prediction of the Cerebral Hyperperfusion Phenomenon after Carotid Endarterectomy Using a Transit Time Flowmeter.

The purpose of this study was to investigate the relationship between the cerebral hyperperfusion phenomenon (CHP) and carotid artery flow volume as measured by a transit time flowmeter during carotid endarterectomy (CEA). We retrospectively investigated 74 patients who underwent both transit time flowmetry and single photon emission computed tomography (SPECT). The flow volumes of the internal carotid artery (ICA) before and after the endarterectomy were recorded during surgery as the pre- and the post-ICA (mL/min), respectively. We defined the difference between the pre- and the post-ICA as the ΔIC (mL/min). Two independent board-certified neurosurgeons analyzed the asymmetry index (affected side/contralateral side) of regional qualitative cerebral blood flow before and after the CEA respectively. We defined the CHP as an excessive increase in this asymmetry index between preoperative and postoperative SPECT. The CHP was observed in five of the 74 patients (6.8%). The pre-ICA of the CHP cases was significantly lower than that of the non-CHP cases (in mL/min, median 29 vs. 97; P = 0.01). The ΔIC of the CHP cases was significantly higher than that of the non-CHP cases (in mL/min, median 154 vs. 50; P = 0.002). The cut-off value of the ΔIC was 81 mL/min (sensitivity 100%, specificity 78.3%, area under the curve 0.912). The findings of this study suggest that the ΔIC is associated with the CHP. The transit time flowmeter is useful to predict the CHP during surgery.

Beyond patency: Functional assessment of adequacy using internal mammary artery grafting to the left anterior descending artery

Arterial graft physiology influences the long-term outcome of coronary artery bypass grafting (CABG). We studied factors that can affect the overall resistance to flow using internal mammary artery grafting to the left anterior descending artery. This was a prospective, nonrandomized observational study of 100 consecutive patients who underwent elective on-pump isolated or combined valve surgery and CABG. Coronary stenoses were assessed using conventional and quantitative coronary angiography assessment. The flow and pulsatility index (PI) of the grafts were assessed by transit-time flowmetry during cardioplegic arrest and at the end of the operation. Fractional polynomials were used to explore linearity, followed by multivariable regression analysis. Univariate analysis demonstrated higher flows at the end of the operation in patients who had higher flows with the cross-clamp on (P < .001), in males (P = .004), in patients with a low PI at the end of the operation (P = .04), and in patients with a larger size of the recipient artery (P = .005). Multivariable regression analysis showed that the graft flow at the end of the operation was significantly associated with the mean flow with the cross-clamp on (P < .001), sex (P = .003), and PI at the end of the operation (P = .003). Concomitant valve surgery did not influence flows. Male patients had 18 mL/min higher flow. The graft flow at the end of the operation can be determined by the flow with the cross-clamp on, the PI with the cross-clamp off and coronary artery. We reported differences in the graft flows between sexes, and for first the time, we introduced the concepts of "adequate flow" and "resistance-to-forward-flow" for patent coronary grafts.