Can a Peritoneal Conduit Become an Artery?

OBJECTIVE: Current vascular grafts all have limitations. This study examined peritoneum as a potential graft material and the in vivo transfer of peritoneum into a functional artery like conduit after end to end anastomosis into the common carotid artery of sheep. The aim was to investigate whether implantation of a peritoneal tube into the arterial tree results in a structure with function, histological findings, and gene expression like an artery, and whether such arterialisation occurs through a conversion of the phenotype of peritoneal cells or from host cell migration into the implant. METHODS: Peritoneum with adherent rectus aponeurosis from sheep was used to form tubular vascular grafts that were implanted into the common carotid artery of six sheep, then removed after five months. Two sheep received allogenic peritoneal grafts and four sheep received autologous peritoneal grafts. RESULTS: One sheep died shortly after implantation, so five of the six sheep were followed. Five months after implantation, four of the five remaining grafts were patent. Three of four patent grafts were aneurysmal. The four patent grafts had developed an endothelial layer indistinguishable from that of the adjacent normal artery, and a medial layer with smooth muscle cells with a surrounding adventitia. The new conduit displayed vasomotor function not present at the time of implantation. DNA genotyping showed that the media in the new conduit consisted of recipient smooth muscle cells. Little difference in mRNA expression was demonstrated between the post-implantation conduit and normal artery. CONCLUSION: During a five month implantation period in the arterial system, peritoneum converted into a tissue that histologically and functionally resembled a normal artery, with a functional genetic expression that resembled that of an artery. Single nucleotide polymorphism analysis indicated that this conversion occurs through host cell migration into the graft.

Upper arm venous compliance and fitness in stable coronary artery disease patients and healthy controls.

OBJECTIVES: Arteries have been examined extensively in coronary artery disease (CAD), while less attention has been paid to veins. AIMS: (1) To determine whether venous compliance or venous outflow in the upper arm is reduced in CAD patients compared to healthy age- and fitness-matched controls; and (2) to examine the association between upper arm venous compliance and total blood volume. DESIGN: Fifteen patients with stable CAD (age 62·1 ± 5·7 years, body mass index 26·5 ± 3·2 kg·m2 , fat-free mass 59·3 ± 7·6 kg, mean arterial pressure 98·9 ± 8·0 mmHg, VO2peak : 2·92 ± 0·53 l min-1 ) were compared to twelve healthy age- and fitness-matched controls (age 62·2 ± 3·7 years, body mass index 26·2 ± 2·3 kg m2 , fat-free mass 61·0 ± 9·2 kg, mean arterial pressure 96·5 ± 9·1 mmHg, VO2peak : 3·24 ± 0·48 l min-1 ). Venous compliance was examined using high-resolution ultrasound and Doppler in the basilic vein. Blood volumes were measured by the optimized CO rebreathing method. RESULTS: Equal upper arm venous compliance normalized to blood volume (patients: 0·28 ± 0·26 mm3  mmHg-1  l-1 , healthy controls: 0·16 ± 0·11 mm3 mmHg-1  l-1 ) and peak venous outflow normalized to blood volume (patients: 10·4 ± 3·9 cm s-1  l-1 , healthy controls: 8·3 ± 0·8 cm s-1  l-1 ) were found in patients with CAD and healthy age- and fitness-matched controls. Additionally, no difference was found in blood volume (patients: 6·06 ± 0·79 l, healthy controls: 6·68 ± 1·27 l) or VO2peak . CONCLUSION: Comparable upper arm venous compliance and venous outflow in CAD patients and healthy age- and fitness-matched controls might indicate that high VO2peak and blood volume could prevent possible disease-induced reductions in venous compliance in CAD.

Comparison of Three Popular Exercise Modalities on V˙O2max in Overweight and Obese.

INTRODUCTION: In this prospective randomized trial, we examined the effect of three popular exercise training modalities on maximal oxygen uptake (V˙O2max) in overweight and obese individuals. In addition, we examined possible concomitant adaptations in endurance exercise performance (time to exhaustion (TTE)), citrate synthase (CS) activity, venous and arterial function, blood volume, and calculated stroke volume (SV). METHODS: Thirty subjects were recruited (age, 41 ± 9 yr; weight, 91 ± 14 kg; height, 173 ± 8 cm; body mass index, 30 ± 4 kg·m(-2)) and randomized to either 6 wk of 4 × 4-min high-intensity interval training (4HIIT) at 85%-95% of HRmax, 10 × 1-min HIIT (1HIIT) at V˙O2max load, or 45-min moderate-intensity continuous training (MICT) at 70% of HRmax. V˙O2max, TTE, CS activity, venous and arterial function, as well as blood volume were measured before and after the training period. O2 pulse was calculated and used to estimate SV. Analysis was conducted per protocol. RESULTS: Only 4HIIT increased V˙O2max (P < 0.01) and significantly more compared with 1HIIT (P = 0.04) and MICT (P = 0.03) (4HIIT, 10%; 1HIIT, 3.3%; and MICT, 3.1%). All groups increased TTE (4HIIT, 198%; 1HIIT, 116%; MICT, 52%), with a higher increase after 4HIIT compared with that after MICT (P = 0.02). Calculated SV increased only after 4HIIT (14.4%). Plasma volume and hemoglobin mass increased after 1HIIT only (5.6% and 6.5%); however, no group differences were found. All groups increased CS activity (4HIIT, 35%; 1HIIT, 35%; MICT, 56%), with no group differences. Arterial inflow (15.7%) and venous outflow (22.7%) decreased after MICT, but there were no group differences. CONCLUSIONS: 4HIIT was superior to 1HIIT and MICT in improving V˙O2max likely because of an increased SV.

Safety of the CO-Rebreathing Method in Patients with Coronary Artery Disease.

PURPOSE: To address and study the safety concerns with the improved carbon monoxide (CO) rebreathing method for measuring total blood volume in patients with coronary artery disease to implement the use of the methodology in this patient group. METHODS: Eighteen patients with stable coronary artery disease (age 62 ± 7 yr, 24 ± 5 months since diagnosis) were investigated using the improved CO-rebreathing test. Before, during, and up to 2 h after the test, ECG, blood pressure, arterial oxygen saturation, carbon monoxide bound to hemoglobin (HbCO%), and cardiac function were measured. At 24 h, HbCO% and troponin-T were measured. DESIGN: Cross-over. RESULTS: Six minutes after the CO-rebreathing test, HbCO increased from 1.5% ± 0.4% to 6.0% ± 0.6%, with a subsequent decrease to 4.5% ± 0.4% and 1.4% ± 0.4% at 2 h and 24 h after the test, respectively. Resting heart rate, stroke volume, cardiac output, and ejection fraction were 64 ± 11 bpm, 93.9 ± 16.5 mL per beat, 5.84 ± 0.99 L, and 48.5% ± 5.7% and remained unchanged during and 10 min after the rebreathing. All patients were in sinus rhythm during the 2-h observation period, without ST- or T-wave changes, with low numbers of premature beats and normal rate variability. Systolic and diastolic blood pressure gradually decreased during the observation period. Troponin-T was below the 99th percentile for all the participants 24 h after the test. CONCLUSION: Cardiovascular function and safety indices remained unchanged after exposure to approximately 6% HbCO, indicating that the method is safe to perform in patients with stable coronary artery disease.

How to Be 80 Year Old and Have a VO2max of a 35 Year Old.

UNLABELLED: Background. To discuss the cardiovascular and pulmonary physiology and common risk factors of an 80-year-old man with a world record maximal oxygen uptake of 50 mL·kg(-1)·min(-1). Methods. CASE REPORT: Results. His maximal oxygen uptake of 3.31 L·min(-1), maximal heart rate of 175 beats·min(-1), and maximal oxygen pulse of 19 mL·beats(-1) are high. He is lean (66.6 kg) and muscular (49% skeletal muscle mass). His echo parameters of mitral flow (left ventricular filling, E = 82 cm·s(-1) and E/A = 1.2) were normal for 40- to 60-year-old men. Systolic and diastolic function increased adequately during exercise, with no increase in left ventricular filling pressure. He has excellent pulmonary function (FVC = 4.31 L, FEV1 = 3.41, FEV1/FVC = 0.79, and DLCO = 12.0 Si(1)) and normal FMD and blood volumes (5.8 L). He has a high level of daily activity (10,900 steps·day(-1) and 2:51 hours·day(-1) of physical activity) and a lifelong history of physical activity. Conclusion. The man is in excellent cardiopulmonary fitness and is highly physically active. His cardiac and pulmonary functions are above expectations for his age, and his VO2max is comparable to that of an inactive 25-year-old and of a normal, active 35-year-old Norwegian man.

Low- and high-volume of intensive endurance training significantly improves maximal oxygen uptake after 10-weeks of training in healthy men.

UNLABELLED: Regular exercise training improves maximal oxygen uptake (VO2max), but the optimal intensity and volume necessary to obtain maximal benefit remains to be defined. A growing body of evidence suggests that exercise training with low-volume but high-intensity may be a time-efficient means to achieve health benefits. In the present study, we measured changes in VO2max and traditional cardiovascular risk factors after a 10 wk. training protocol that involved three weekly high-intensity interval sessions. One group followed a protocol which consisted of 4×4 min at 90% of maximal heart rate (HRmax) interspersed with 3 min active recovery at 70% HRmax (4-AIT), the other group performed a single bout protocol that consisted of 1×4 min at 90% HRmax (1-AIT). Twenty-six inactive but otherwise healthy overweight men (BMI: 25-30, age: 35-45 y) were randomized to either 1-AIT (n = 11) or 4-AIT (n = 13). After training, VO2max increased by 10% (∼5.0 mL⋅kg(-1)⋅min(-1)) and 13% (∼6.5 mL⋅kg(-1)⋅min(-1)) after 1-AIT and 4-AIT, respectively (group difference, p = 0.08). Oxygen cost during running at a sub-maximal workload was reduced by 14% and 13% after 1-AIT and 4-AIT, respectively. Systolic blood pressure decreased by 7.1 and 2.6 mmHg after 1-AIT and 4-AIT respectively, while diastolic pressure decreased by 7.7 and 6.1 mmHg (group difference, p = 0.84). Both groups had a similar ∼5% decrease in fasting glucose. Body fat, total cholesterol, LDL-cholesterol, and ox-LDL cholesterol only were significantly reduced after 4-AIT. Our data suggest that a single bout of AIT performed three times per week may be a time-efficient strategy to improve VO2max and reduce blood pressure and fasting glucose in previously inactive but otherwise healthy middle-aged individuals. The 1-AIT type of exercise training may be readily implemented as part of activities of daily living and could easily be translated into programs designed to improve public health. TRIAL REGISTRATION: ClinicalTrials.govNCT00839579.