Aortic Regurgitation, Time to Aortic Valve Reintervention, and Mortality in Degenerated Trifecta Versus Non-Trifecta Bioprosthesis.

On July 31, 2023, the Trifecta valve was withdrawn from the market after concerns regarding early (≤5 years) structural valve deterioration (SVD), mainly as aortic regurgitation (AR). Our aim was to determine the timing, mechanism, and impact of bioprosthetic SVD in patients who underwent redo aortic valve replacement (redo-AVR) with either redo-SAVR or valve-in-valve transcatheter aortic valve replacement (TAVR) using Trifecta versus other bioprosthetic valves. Patients who underwent redo-AVR for SVD at our institution were categorized into 2 groups based on the valve type: Trifecta versus non-Trifecta. Multivariate Cox proportional hazard model and Kaplan-Meier curves were used to compare mortality. A total of 171 patients were included; 58 (34%) had previous SAVR with a Trifecta valve and 113 (66%) with non-Trifecta valve. A total of 103 patients (60%) underwent valve-in-valve TAVR and 68 redo-SAVR (40%). The age, gender, and Society of Thoracic Surgeons score were similar between Trifecta and non-Trifecta groups. In patients with bioprosthetic valves requiring redo-AVR, Trifecta valves had an earlier onset of greater than moderate AR (4.5 vs 11.9 years, p <0.001) and earlier time to redo-AVR (5.5 vs 12 years, p <0.001). AR was more common as the mechanism of SVD in Trifecta versus non-Trifecta valves (55.2% vs 30.1%, p = 0.006). All-cause adjusted mortality from index SAVR was higher in the Trifecta than in non-Trifecta group (hazard ratio 4.1, 95% confidence interval 1.5 to 11.5, p = 0.007). In conclusion, compared with non-Trifecta valves, Trifecta valves exhibit early SVD primarily as AR and progress rapidly to significant SVD requiring redo-AVR. Mortality is significantly higher with Trifecta than in non-Trifecta valves, potentially impacting the results of SAVR versus TAVR studies.

Clinical outcomes of intravenous iron therapy in patients with heart failure and iron deficiency: Meta-analysis and trial sequential analysis of randomized clinical trials.

BACKGROUND: Iron deficiency in patients with heart failure (HF) is underdiagnosed and undertreated. The role of intravenous (IV) iron is well-established to improve quality of life measures. Emerging evidence also supports its role in preventing cardiovascular events in patients with HF. METHODOLOGY: We conducted a literature search of multiple electronic databases. Randomized controlled trials that compared IV iron to usual care among patients with HF and reported cardiovascular (CV) outcomes were included. Primary outcome was the composite of first heart failure hospitalization (HFH) or CV death. Secondary outcomes included HFH (first or recurrent), CV death, all-cause mortality, hospitalization for any cause, gastrointestinal (GI) side effects, or any infection. We performed trial sequential and cumulative meta-analyses to evaluate the effect of IV iron on the primary endpoint, and on HFH. RESULTS: Nine trials enrolling 3337 patients were included. Adding IV iron to usual care significantly reduced the risk of first HFH or CV death [risk ratio (RR) 0.84; 95 % confidence interval (CI) 0.75-0.93; I2 = 0 %; number needed to treat (NNT) 18], which was primarily driven by a reduction in the risk of HFH of 25 %. IV iron also reduced the risk of the composite of hospitalization for any cause or death (RR 0.92; 95 % CI 0.85-0.99; I2 = 0 %; NNT 19). There was no significant difference in the risk of CV death, all-cause mortality, adverse GI events, or any infection among patients receiving IV iron compared to usual care. The observed benefits of IV iron were directionally consistent across trials and crossed both the statistical and trial sequential boundaries of benefit. CONCLUSION: In patients with HF and iron deficiency, the addition of IV iron to usual care reduces the risk of HFH without affecting the risk of CV or all-cause mortality.

Left Ventricular Unloading With Impella Versus IABP in Patients With VA-ECMO: A Systematic Review and Meta-Analysis.

Venoarterial extracorporeal membrane oxygenation (VA-ECMO) use for circulatory support in cardiogenic shock results in increased left ventricular (LV) afterload. The use of concomitant Impella or intra-aortic balloon pump (IABP) have been proposed as adjunct devices for LV unloading. The authors sought to compare head-to-head efficacy and safety outcomes between the 2 LV unloading strategies. We conducted a search of Medline, EMBASE, and Cochrane databases to identify studies comparing the use of Impella to IABP in patients on VA-ECMO. The primary outcome of interest was in-hospital mortality. The secondary outcomes included transition to durable LV assist devices/cardiac transplantation, stroke, limb ischemia, need for continuous renal replacement therapy, major bleeding, and hemolysis. Pooled risk ratios (RRs) with 95% confidence interval and heterogeneity statistic I2 were calculated using a random-effects model. A total of 7 observational studies with 698 patients were included. Patients on VA-ECMO unloaded with Impella vs IABP had similar risk of short-term all-cause mortality, defined as either 30-day or in-hospital mortality- 60.8% vs 64.9% (RR 0.93 [0.71 to 1.21], I2 = 71%). No significant difference was observed in transition to durable LV assist devices/cardiac transplantation, continuous renal replacement therapy initiation, stroke, or limb ischemia between the 2 strategies. However, the use of VA-ECMO with Impella was associated with increased risk of major bleeding (57.2% vs 39.7%) (RR 1.66 [1.12 to 2.44], I2 = 82%) and hemolysis (31% vs 7%) (RR 4.61 [1.24 to 17.17], I2 = 66%) compared with VA-ECMO, along with IABP. In conclusion, in patients requiring VA-ECMO for circulatory support, the concomitant use of Impella or IABP had comparable short-term mortality. However, Impella use was associated with increased risk of major bleeding and hemolysis.

Refractory Lactic Acidosis and Hypoglycemia in a Patient With Metastatic Esophageal Cancer Due to the Warburg Effect.

The Warburg effect describes a phenomenon in which tumor cells switch their metabolic machinery towards a glycolytic state even in the presence of normal oxygen concentration, resulting in excess lactate production. Lactic acidosis due to the Warburg effect in malignancy is a rare but potentially life-threatening emergency mainly described in hematological malignancies but can occur in non-hematological solid malignancies. To our knowledge, we present the first reported case of lactic acidosis due to the Warburg effect in metastatic esophageal cancer. A 44-year-old male was found to have an esophageal mass and likely hepatic metastases during his hospitalization for altered mental status due to severe hypercalcemia. He was re-admitted two days after discharge for persistent vomiting and an inability to tolerate an oral diet. The lab revealed elevated lactate levels (5.2 mmol/L), metabolic acidosis (pH 7.23), and hypoglycemia (48 mg/dL), all of which were persistent throughout hospitalization despite treatment with intravenous (IV) infusions of dextrose in sodium bicarbonate, IV boluses of dextrose, and IV thiamine. An esophagogastroduodenoscopy with a biopsy of the esophageal mass revealed squamous cell carcinoma of the esophagus. Given the presence of stage IV disease and poor functional status, the patient opted for in-patient hospice, where he passed away. Since prompt diagnosis and initiation of chemotherapy, if possible, are the only effective interventions for this potentially fatal complication, it is important to increase awareness of this underrecognized metabolic and oncologic emergency among physicians.

UBC-Nepal expedition: phenotypical evidence for evolutionary adaptation in the control of cerebral blood flow and oxygen delivery at high altitude.

KEY POINTS: Sherpa have lived in the Nepal Himalaya for 25-40 thousand years and display positive physiological adaptations to hypoxia. Sherpa have previously been demonstrated to suffer less negative cerebral side effects of ascent to extreme altitude, yet little is known as to whether or not they display differential regulation of oxygen delivery to the brain compared to lowland natives. We demonstrate that Sherpa have lower brain blood flow during ascent to and acclimatization at high altitude compared to lowlanders and that this difference in flow is not attributable to factors such as mean arterial pressure, blood viscosity and pH. The observed lower cerebral oxygen delivery in Sherpa likely represents a positive adaptation that may indicate a cerebral hypometabolic conservation of energy at altitude and/or decreased risk of other cerebral consequences such as vasogenic oedema. ABSTRACT: Debilitating side effects of hypoxia manifest within the central nervous system; however, high-altitude natives of the Tibetan plateau, the Sherpa, experience negligible cerebral effects compared to lowland natives at extreme altitude. Phenotypical optimization of the oxygen cascade has been demonstrated in the systemic circulation of Tibetans and Sherpa, likely underscoring their adapted capacity to thrive at altitude. Yet, little is known as to how the cerebral circulation of Sherpa may be adapted. To examine potential differences in cerebral oxygen delivery in Sherpa compared to lowlanders we measured arterial blood gases and global cerebral blood flow (duplex ultrasound) during a 9 day ascent to 5050 m. Although cerebral oxygen delivery was maintained during ascent in lowlanders, it was significantly reduced in the Sherpa at 3400 m (-30.3 ± 21.6%; P < 0.01) and 4371 m (-14.2 ± 10.7%; P = 0.03). Furthermore, linear mixed effects modelling indicated that independent of differences in mean arterial pressure, pH and blood viscosity, race accounts for an approximately 100 mL min-1 (∼17-34%) lower cerebral blood flow in Sherpa compared to lowlanders across ascent to altitude (P = 0.046). To ascertain the role of chronic hypoxia independent of the ascent, Sherpa who had not recently descended were also examined at 5050 m. In these Sherpa, cerebral oxygen delivery was also lower compared to lowlanders (∼22% lower; P < 0.01). We highlight new information about the influence of race and genetic adaptation in the regulation of cerebral oxygen delivery. The lower cerebral oxygen delivery in the Sherpa potentially represents a positive adaptation considering Sherpa endure less deleterious cerebral consequences than lowlanders at altitude.

UBC-Nepal Expedition: Cerebrovascular Responses to Exercise in Sherpa Children Residing at High Altitude.

Understanding the process of successful adaptation to high altitude provides valuable insight into the pathogenesis of conditions associated with impaired oxygen uptake and utilization. Prepubertal children residing at low altitude show a reduced cerebrovascular response to exercise in comparison to adults, and a transient uncoupling of cerebral blood flow to changes in the partial pressure of end-tidal CO2 (PETCO2); however, little is known about the cerebrovascular response to exercise in high-altitude native children. We sought to compare the cerebral hemodynamic response to acute exercise between prepubertal children residing at high and low altitude. Prepubertal children (n = 32; 17 female) of Sherpa descent (Sherpa children [SC]) at high altitude (3800 m, Nepal) and maturational-matched (n = 32; 20 female) children (lowland children [LLC]) residing at low altitude (342 m, Canada). Ventilation, peripheral oxygen saturation (SpO2), PETCO2, and blood velocity in the middle and posterior cerebral arteries (MCAv and PCAv) were continuously measured during a graded cycling exercise test to exhaustion. At baseline (BL), PETCO2 (-19 ± 4 mmHg, p < 0.001), SpO2 (-6.0% ± 2.1%, p < 0.001), MCAv (-12% ± 5%, p = 0.02), and PCAv (-12% ± 6%, p = 0.04) were lower in SC when compared with LLC. Despite this, the relative change in MCAv and PCAv during exercise was similar between the two groups (p = 0.99). Linear regression analysis demonstrated a positive relationship between changes in PETCO2 with MCAv in SC (R2 = 0.13, p > 0.001), but not in LLC (R2 = 0.03, p = 0.10). Our findings demonstrate a similar increase in intra-cranial perfusion during exercise in prepubertal SC, despite differential BL values and changes in PETCO2 and SpO2.

UBC-Nepal Expedition: An experimental overview of the 2016 University of British Columbia Scientific Expedition to Nepal Himalaya.

The University of British Columbia Nepal Expedition took place over several months in the fall of 2016 and was comprised of an international team of 37 researchers. This paper describes the objectives, study characteristics, organization and management of this expedition, and presents novel blood gas data during acclimatization in both lowlanders and Sherpa. An overview and framework for the forthcoming publications is provided. The expedition conducted 17 major studies with two principal goals-to identify physiological differences in: 1) acclimatization; and 2) responses to sustained high-altitude exposure between lowland natives and people of Tibetan descent. We performed observational cohort studies of human responses to progressive hypobaric hypoxia (during ascent), and to sustained exposure to 5050 m over 3 weeks comparing lowlander adults (n = 30) with Sherpa adults (n = 24). Sherpa were tested both with (n = 12) and without (n = 12) descent to Kathmandu. Data collected from lowlander children (n = 30) in Canada were compared with those collected from Sherpa children (n = 57; 3400-3900m). Studies were conducted in Canada (344m) and the following locations in Nepal: Kathmandu (1400m), Namche Bazaar (3440m), Kunde Hospital (3480m), Pheriche (4371m) and the Ev-K2-CNR Research Pyramid Laboratory (5050m). The core studies focused on the mechanisms of cerebral blood flow regulation, the role of iron in cardiopulmonary regulation, pulmonary pressures, intra-ocular pressures, cardiac function, neuromuscular fatigue and function, blood volume regulation, autonomic control, and micro and macro vascular function. A total of 335 study sessions were conducted over three weeks at 5050m. In addition to an overview of this expedition and arterial blood gas data from Sherpa, suggestions for scientists aiming to perform field-based altitude research are also presented. Together, these findings will contribute to our understanding of human acclimatization and adaptation to the stress of residence at high-altitude.

UBC-Nepal expedition: markedly lower cerebral blood flow in high-altitude Sherpa children compared with children residing at sea level.

Developmental cerebral hemodynamic adaptations to chronic high-altitude exposure, such as in the Sherpa population, are largely unknown. To examine hemodynamic adaptations in the developing human brain, we assessed common carotid (CCA), internal carotid (ICA), and vertebral artery (VA) flow and middle cerebral artery (MCA) velocity in 25 (9.6 ± 1.0 yr old, 129 ± 9 cm, 27 ± 8 kg, 14 girls) Sherpa children (3,800 m, Nepal) and 25 (9.9 ± 0.7 yr old, 143 ± 7 cm, 34 ± 6 kg, 14 girls) age-matched sea level children (344 m, Canada) during supine rest. Resting gas exchange, blood pressure, oxygen saturation and heart rate were assessed. Despite comparable age, height and weight were lower (both P < 0.01) in Sherpa compared with sea level children. Mean arterial pressure, heart rate, and ventilation were similar, whereas oxygen saturation (95 ± 2 vs. 99 ± 1%, P < 0.01) and end-tidal Pco2 (24 ± 3 vs. 36 ± 3 Torr, P < 0.01) were lower in Sherpa children. Global cerebral blood flow was ∼30% lower in Sherpa compared with sea level children. This was reflected in a lower ICA flow (283 ± 108 vs. 333 ± 56 ml/min, P = 0.05), VA flow (78 ± 26 vs. 118 ± 35 ml/min, P < 0.05), and MCA velocity (72 ± 14 vs. 88 ± 14 cm/s, P < 0.01). CCA flow was similar between Sherpa and sea level children (425 ± 92 vs. 441 ± 81 ml/min, P = 0.52). Scaling flow and oxygen uptake for differences in vessel diameter and body size, respectively, led to the same findings. A lower cerebral blood flow in Sherpa children may reflect specific cerebral hemodynamic adaptations to chronic hypoxia.NEW & NOTEWORTHY Cerebral blood flow is lower in Sherpa children compared with children residing at sea level; this may reflect a cerebral hemodynamic pattern, potentially due to adaptation to a hypoxic environment.