1 The Copenhagen Muscle Research Centre, University
Hospital, DK-2100 Copenhagen, Denmark; and the Departments of
2 Cardiology and
3 Physiology-Pharmacology, Karolinska Institute, ...171 77 Stockholm, Sweden
To
study the role of muscle mass and muscle activity on lactate and energy
kinetics during exercise, whole body and limb lactate, glucose, and
fatty acid fluxes were determined in six elite cross-country skiers
during roller-skiing for 40 min with the diagonal stride (Continuous
Arm + Leg) followed by 10 min of double poling and diagonal stride at
72-76% maximal O 2 uptake. A high lactate appearance rate (R a , 184 ± 17 µmol · kg 1 · min 1 )
but a low arterial lactate concentration (~2.5 mmol/l) were observed
during Continuous Arm + Leg despite a substantial net lactate release
by the arm of ~2.1 mmol/min, which was balanced by a similar net
lactate uptake by the leg. Whole body and limb lactate oxidation during
Continuous Arm + Leg was ~45% at rest and ~95% of disappearance
rate and limb lactate uptake, respectively. Limb lactate kinetics
changed multiple times when exercise mode was changed. Whole body
glucose and glycerol turnover was unchanged during the different skiing
modes; however, limb net glucose uptake changed severalfold. In
conclusion, the arterial lactate concentration can be maintained at a
relatively low level despite high lactate R a during
exercise with a large muscle mass because of the large capacity of
active skeletal muscle to take up lactate, which is tightly correlated
with lactate delivery. The limb lactate uptake during exercise is
oxidized at rates far above resting oxygen consumption, implying that
lactate uptake and subsequent oxidation are also dependent on an
elevated metabolic rate. The relative contribution of whole body and
limb lactate oxidation is between 20 and 30% of total carbohydrate
oxidation at rest and during exercise under the various conditions.
Skeletal muscle can change its limb net glucose uptake severalfold
within minutes, causing a redistribution of the available glucose
because whole body glucose turnover was unchanged.
lactate dehydrogenase; cross-country skiing; tracers
Catheter ablation is effective in reducing atrial fibrillation (AF), but the association of ablation for AF with quality of life is unclear.
To evaluate whether the procedural outcome of ablation for ...AF is associated with quality of life (QOL) measures.
This was a prespecified secondary analysis of the Substrate and Trigger Ablation for Reduction of Atrial Fibrillation-Part II (STAR AF II) prospective randomized clinical trial, which compared 3 strategies for ablation of persistent AF. This analysis included 549 of the 589 patients enrolled in the trial who underwent ablation. Enrollment occurred at 35 centers in Europe, Canada, Australia, China, and Korea from November 2010 to July 2012. Data for the current study were analyzed on December 11, 2019.
Patients underwent AF ablation with 1 of 3 ablation strategies: (1) pulmonary vein isolation (PVI), (2) PVI plus complex fractionated electrograms, or (3) PVI plus linear lesions.
Quality of life was assessed at baseline and at 6, 12, and 18 months after ablation for AF using the 36-Item Short Form Health Survey and the EuroQol Health-Related Quality of Life 5-Dimension 3-Level questionnaire. Scores were also converted to a physical health component score (PCS) and a mental health component score (MCS). Individual AF burden was calculated by the total time with AF from Holter monitors and the percentage of transtelephonic monitor recordings showing AF.
Among the 549 patients included in this secondary analysis, QOL was assessed in 466 (85%) at baseline and at 6, 12, and 18 months after ablation for AF. The mean (SD) age of the study population was 60 (9) years; 434 (79%) individuals were men, and 417 (76%) had continuous AF for 6 months or more before ablation. The AF burden significantly decreased from a mean (SD) of 82% (36%) before ablation to 6.6% (23%) after ablation (P < .001). Significant improvements in mean (SD) PCS (68.3 20.7 to 82.5 18.6) and MCS (35.3 8.6 to 37.5 7.6) occurred 18 months after ablation (P < .05 for both). Significant QOL improvement occurred in all 3 study arms and regardless of AF recurrence, defined as AF episodes lasting more than 30 seconds: for no recurrence, mean (SD) PCS increased from 66.5 (20.9) to 79.1 (19.4) and MCS from 35.3 (8.7) to 37.7 (7.7); for recurrence, mean (SD) PCS increased from 70.2 (20.4) to 86.4 (16.8) and MCS from 35.3 (8.6) to 37.1 (7.4) (P < .05 for all). When outcome was defined by AF burden reduction, in patients with less than 70% reduction in AF burden, the increase in PCS was significantly less than in those with greater than 70% reduction, and only 3 of 8 subscales showed significant improvement.
In this secondary analysis, decreases in AF burden after ablation for AF were significantly associated with improvements in QOL. Quality of life changes were significantly associated with the percentage of AF burden reduction after ablation.
ClinicalTrials.gov Identifier: NCT01203748.
Objectives. Cryoablation (CRYO) is an alternative to radiofrequency (RF) for catheter ablation of cavotricuspid isthmus (CTI)-dependent atrial flutter (AFL). We aimed to study whether different CTI ...morphologies had different impacts on procedural success for CRYO and RF. Design. This study randomized 153 patients with CTI-dependent AFL (median age 65 years; range 34-82) to RF or CRYO (78 CRYO; 75 RF). Biplane angiography (RAO 30° and LAO 60°) was done before the ablation procedure and isthmuses were classified as straight (n = 81), concave (n = 43) or pouch-like (n = 29). RF was performed with a 3.5-mm open-irrigated tip catheter and CRYO was performed with a 9 F, 8-mm tip catheter. The ablation endpoint was bidirectional block of CTI. Results. Acute procedural success was achieved in 70/75 patients in the RF group and in 72/78 patients in the CRYO group. With regard to CRYO or RF, acute procedural success rates were similar between the three isthmus types: straight: CRYO (92%) and RF (96%); concave: CRYO (92%) and RF (94%); and pouch-like: CRYO (94%) and RF (85%). There were no significant differences regarding success rate between the different morphologies in the CRYO or the RF group. The CTI was longer in patients with acute failure compared to the patients with acute success (38 ± 7 mm versus 33 ± 6 mm, p = 0.045). Conclusion. The CTI morphology did not influence the acute success rate for either the CRYO or the RF ablation of CTI-dependent AFL. A longer CTI was associated with a lower success rate regardless of energy source.
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To elucidate the mechanisms of lactate formation during submaximal exercise, eight men were studied during one- (1-LE) and two-leg (2-LE) exercise (approximately 11-min cycling) using the ...catheterization technique and muscle biopsies (quadriceps femoris muscle). The absolute exercise intensity and thus the energy demand for the exercising limb was the same mean 114 (SEM 7) W during both 1-LE and 2-LE. At the end of exercise partial pressure of O2 and O2 saturation in femoral venous blood were lower and arterial adrenaline and noradrenaline were higher during 2-LE than during 1-LE. Mean arterial blood lactate concentration increased to 10.8 (SEM 0.8) (2-LE) and 5.2 (SEM 0.4) mmol.l-1 (1-LE) after 10 min of exercise. The intramuscular metabolic response to exercise was attenuated during 1-LE mean, lactate = 49 (SEM 9); glucose 6-P = 3.3 (SEM 0.3); nicotinamide adenine dinucleotide, reduced = 0.17 (SEM 0.02); adenosine 5'-diphosphate 2.7 (SEM 0.1) mmol.kg dry mass-1 compared to 2-LE 76 (SEM 6); 6.1 (SEM 0.7); 0.21 (SEM 0.02); 3.0 (SEM 0.1) mmol.kg dry mass-1, respectively. To elucidate whether the lower plasma adrenaline concentration could contribute to the attenuated metabolic response, additional experiments were performed on four of the eight subjects with infusion of adrenaline during 1-LE (1-LEE). Average plasma adrenaline concentration was increased during 1-LEE and reached 2-4 times higher levels than during 2-LE. Post-exercise muscle lactate and glucose 6-P contents were higher during 1-LEE than during 1-LE and were similar to those during 2-LE.
We investigated whether, in a randomly selected population of 55-year-old men and women, there is a relationship between common carotid artery (CCA) diameter and intima-media (IM) thickness and ...conventional risk factors for cardiovascular disease such as gender, smoking, elevated blood lipids, and high blood pressure.
CCA diameter and IM thickness of the distal right and left CCAs were measured by high-frequency ultrasound methods. Fifty-seven men (73% of the invited men) and 47 women (62% of the invited women) participated.
In the whole group the CCA diameter was correlated with gender (P<0.001), cholesterol (P=0.007), triglycerides (P<0.001), apoB (P<0.001), apoB/A-1 (P<0.001), systolic blood pressure (P=0. 001), and glucose (P=0.006). HDL was inversely correlated with mean CCA diameter (P=0.003). In men the CCA diameter was correlated with a combined risk factor score (P=0.005), systolic blood pressure (P=0. 011), platelet count (P=0.033), apoB (P=0.025), and occurrence of plaque (P=0.003). In women the CCA diameter was correlated with a combined risk factor score (P=0.010), systolic blood pressure (P=0. 033), body mass index (P<0.001), cholesterol (P=0.009), triglycerides (P=0.14), apoB (P=0.002), and apoB/A1 (P=0.003). IM thickness was correlated with systolic blood pressure (P<0.001).
There are correlations between risk factors for cardiovascular disease and carotid artery diameter and IM thickness in both women and men in a population of 55-year-old subjects. The increased vessel diameter in subjects with cardiovascular risk factors may be a sign of attenuated vasoregulation, which could be an important factor during the development of atherosclerosis.
Aims
The purpose of this study was to evaluate the safety and efficacy of cryoablation in a large series of patients with typical (slow-fast) atrioventricular nodal reentrant tachycardia (AVNRT).
...Methods and results
Between 2003 and 2007, 312 patients with typical AVNRT-median age of 53 years (range 10-92), 200 women (64%)-underwent cryoablation, using exclusively a 6 mm tip catheter tip. Acute success was achieved in 309 of 312 patients (99%). The overall recurrence rate was 18 of 309 (5.8%) during a mean follow-up of 673 ± 381 days. Sixteen of these patients (89%) were successfully reablated. The recurrence rate was 9% in patients with residual dual atrioventricular (AV) nodal pathway post-ablation compared with 4% in those with complete elimination of slow pathway conduction (P = 0.05). No patient developed permanent AV block.
Conclusion
Cryoablation of AVNRT can be achieved with a high acute success rate and a reasonable recurrence rate at long-term follow-up. Complete abolition of slow pathway conduction seems to predict better late outcome.
Radiofrequency (RF) catheter ablation in the septum close to the atrioventricular (AV) node or His bundle has an increased risk of irreversible complications. Cryothermal energy has the advantages of ...reversible cryomapping and increased catheter stability. This study evaluates the usefulness of cryoablation in superoparaseptal and septal accessory pathways (APs).
Twenty-seven consecutive patients (16 men, 11 women, median age 29 years, range 15-65) underwent cryoablation for APs either located in the superoparaseptal (n=18) or septal (n=9) area. Cryomapping, using exclusively a 6 mm tip catheter, at -30 degrees C was performed before ablation with a goal temperature of -80 degrees C for 240 s. Acute success was achieved in 26 out of 27 patients (96%). Total procedure and fluoroscopy time was 163+/-61 and 30+/-22 min, respectively. During a follow-up for a mean of 996+/-511 days, seven patients (27%) had recurrences of arrhythmia. Five out of these seven underwent a second cryoablation with successful results, giving a total success rate of 89%. Two patients developed transient second degree AV block during cryoablation; however, no permanent AV block was observed. The recurrence rate was significantly higher in patients with procedure-related transient mechanical AP block (6/7; 86%) due to catheter trauma compared with those without mechanical block (5/20; 25%; P=0.006).
Cryoablation of the superoparaseptal and septal APs is a safe and effective alternative to RF therapy. Procedure-related transient mechanical AP block predicts worse late outcome.
The aim of this study was to: (1) compare the usefulness, in clinical practice, of different echocardiographic methods of left ventricular (LV) function determination in patients with a recent ...thrombolytic-treated acute myocardial infarction (AMI); (2) compare these measurements with the reference method radionuclide imaging; and (3) evaluate the reproducibility of visual estimation of the LV ejection fraction (EF) and the use of the biplane method of discs (Simpson’s rule) in clinical practice. Echocardiography and radionuclide imaging were performed within 2 hours of each another, 5 to 8 days after hospital admission. Ninety-six patients (70 men and 26 women) age 64 ± 9 years (range 45 to 75) were studied. The echocardiographic study was performed by 2 experienced physicians, independently of each another. LV wall motion score index and visual estimation of the EF correlated best with the radionuclide EF (r = 0.72 and r = 0.71), thereafter simply counting the number of affected LV segments (r = 0.67) or atrioventricular plane measurements (r = 0.64). Simpson’s rule had low correlation to the radionuclide EF (r = 0.45 to 0.51) and could not be used in approximately half of the patients due to poor identification of endocardial borders. The interobserver coefficient of variation for independent visual echocardiographic estimation of the EF was 10%, for Simpson’s rule 18%, and for the radionuclide EF 5%. We conclude that the EF estimated from quantitative echocardiographic volume calculations (Simpson’s rule) may differ substantially from radionuclide methods of measuring the EF. However, with experienced sonographers, the LV wall motion score index or visual estimation of the EF had reasonable agreement with the radionuclide EF in most of the patients. Atrioventricular plane measurement is an acceptable alternative.
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