Tag: Systrom

Acute effect of pyridostigmine in exertional intolerance in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS): A randomized placebo-controlled clinical trial

Rationale: One third of patients with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) have evidence of small fiber neuropathy (SFN). Neurovascular dysregulation during upright exercise may be associated with impaired venoconstriction resulting in low biventricular filling pressures and impaired arteriolar constriction resulting in a mismatch between perfusion and skeletal muscle metabolism. We hypothesize that pyridostigmine, a reversible acetylcholinesterase inhibitor, may improve vascular regulation and exercise tolerance in ME/CFS by increasing sympathetic outflow.

Methods: 45 subjects (39 women, 6 men) with ME/CFS were assessed. A baseline invasive cardiopulmonary exercise test (iCPET) was performed to confirm presence of low peak exercise RAP (<6.5mmHg). Eligible subjects were blindly administered placebo (n=22) or 60mg pyridostigmine (n=23) at a 1:1 ratio. A second iCPET was performed following a 50 minute combined rest and dosing period. Serial iCPET results were compared to assess changes in oxygen uptake at peak exercise (VO2 max). Secondary outcomes included subject ventilatory efficiency (VE/VCO2), peak hemodynamic response (RAP, PCWP, SV, Qt), systemic gas exchange (Ca-vO2/Hgb), and subjective reporting of dyspnea and fatigue. Results: 39 subjects (all women) were considered in data analysis. There was a significant increase in VO2 max between iCPET 1 and iCPET 2 in the treatment group when compared with the placebo group (p = 0.043).

There was a significant decrease in the placebo group and a significant increase in the treatment group in VO2 (p = 0.008), Qt (p = 0.039), and RAP (p = 0.045) when comparing iCPET 1 peak – rest and iCPET 2 peak – rest between groups. There were no significant differences in peak arteriovenous oxygen content difference (Ca-vO2/Hgb). 38% of subjects had objective evidence of SFN with no statistically significant difference between groups.

Conclusion: Using pyridostigmine as an investigative tool, this study suggests that neurovascular dysregulation underlies acute exercise intolerance in ME/CFS. Additionally, we have new evidence that worsening vascular dysregulation results from prior exercise, which sheds insight into the post exertional malaise that is a hallmark of this syndrome.

Source: M. Stovall, P. Joseph, R. Pari, A. Warren, S. Miller, J. Squires, W. Xiao, A.B. Waxman, D.M. Systrom. Acute effect of pyridostigmine in exertional intolerance in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS): A randomized placebo-controlled clinical trial. American Journal of Respiratory and Clinical Care Medicine, Vol 205, p A2063, May 2022. https://www.atsjournals.org/doi/pdf/10.1164/ajrccm-conference.2022.205.1_MeetingAbstracts.A2063

Persistent Exertional Intolerance After COVID-19: Insights From Invasive Cardiopulmonary Exercise Testing

Abstract:

Background: Some patients with COVID-19 who have recovered from the acute infection after experiencing only mild symptoms continue to exhibit persistent exertional limitation that often is unexplained by conventional investigative studies.

Research question: What is the pathophysiologic mechanism of exercise intolerance that underlies the post-COVID-19 long-haul syndrome in patients without cardiopulmonary disease?

Study design and methods: This study examined the systemic and pulmonary hemodynamics, ventilation, and gas exchange in 10 patients who recovered from COVID-19 and were without cardiopulmonary disease during invasive cardiopulmonary exercise testing (iCPET) and compared the results with those from 10 age- and sex-matched control participants. These data then were used to define potential reasons for exertional limitation in the cohort of patients who had recovered from COVID-19.

Results: The patients who had recovered from COVID-19 exhibited markedly reduced peak exercise aerobic capacity (oxygen consumption [VO2]) compared with control participants (70 ± 11% predicted vs 131 ± 45% predicted; P < .0001). This reduction in peak VO2 was associated with impaired systemic oxygen extraction (ie, narrow arterial-mixed venous oxygen content difference to arterial oxygen content ratio) compared with control participants (0.49 ± 0.1 vs 0.78 ± 0.1; P < .0001), despite a preserved peak cardiac index (7.8 ± 3.1 L/min vs 8.4±2.3 L/min; P > .05). Additionally, patients who had recovered from COVID-19 demonstrated greater ventilatory inefficiency (ie, abnormal ventilatory efficiency [VE/VCO2] slope: 35 ± 5 vs 27 ± 5; P = .01) compared with control participants without an increase in dead space ventilation.

Interpretation: Patients who have recovered from COVID-19 without cardiopulmonary disease demonstrate a marked reduction in peak VO2 from a peripheral rather than a central cardiac limit, along with an exaggerated hyperventilatory response during exercise.

Source: Singh I, Joseph P, Heerdt PM, Cullinan M, Lutchmansingh DD, Gulati M, Possick JD, Systrom DM, Waxman AB. Persistent Exertional Intolerance After COVID-19: Insights From Invasive Cardiopulmonary Exercise Testing. Chest. 2022 Jan;161(1):54-63. doi: 10.1016/j.chest.2021.08.010. Epub 2021 Aug 11. PMID: 34389297; PMCID: PMC8354807.  https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8354807/ (Full text)

Multisystem Involvement in Post-acute Sequelae of COVID-19 (PASC)

Abstract:

Objective: To describe cerebrovascular, neuropathic and autonomic features of post-acute sequelae of COVID-19 (PASC).

Methods: This retrospective study evaluated consecutive patients with chronic fatigue, brain fog and orthostatic intolerance consistent with PASC. Controls included postural tachycardia syndrome patients (POTS) and healthy participants. Analyzed data included surveys and autonomic (Valsalva maneuver, deep breathing, sudomotor and tilt tests), cerebrovascular (cerebral blood flow velocity (CBFv) monitoring in middle cerebral artery), respiratory (capnography monitoring) and neuropathic (skin biopsies for assessment of small fiber neuropathy) testing and inflammatory/autoimmune markers.

Results: Nine PASC patients were evaluated 0.7±0.3 years after a mild COVID-19 infection, treated as home observations. Autonomic, pain, brain fog, fatigue and dyspnea surveys were abnormal in PASC and POTS (n=10), compared to controls (n=15). Tilt table test reproduced the majority of PASC symptoms. Orthostatic CBFv declined in PASC (-20.0±13.4%) and POTS (-20.3±15.1%), compared to controls (-3.0±7.5%,p=0.001) and was independent of end-tidal carbon dioxide in PASC, but caused by hyperventilation in POTS. Reduced orthostatic CBFv in PASC included both subjects without (n=6) and with (n=3) orthostatic tachycardia. Dysautonomia was frequent (100% in both PASC and POTS) but was milder in PASC (p=0.013). PASC and POTS cohorts diverged in frequency of small fiber neuropathy (89% vs. 60%) but not in inflammatory markers (67% vs. 70%). Supine and orthostatic hypocapnia was observed in PASC.

Interpretation: PASC following mild COVID-19 infection is associated with multisystem involvement including: 1) cerebrovascular dysregulation with persistent cerebral arteriolar vasoconstriction; 2) small fiber neuropathy and related dysautonomia; 3) respiratory dysregulation; 4) chronic inflammation.

Source: Novak P, Mukerji SS, Alabsi HS, Systrom D, Marciano SP, Felsenstein D, Mullally WJ, Pilgrim DM. Multisystem Involvement in Post-acute Sequelae of COVID-19 (PASC). Ann Neurol. 2021 Dec 24. doi: 10.1002/ana.26286. Epub ahead of print. PMID: 34952975. https://pubmed.ncbi.nlm.nih.gov/34952975/

Persistent Exertional Intolerance After COVID-19

Abstract:

Background: Some patients with COVID-19 who have recovered from the acute infection after experiencing only mild symptoms continue to exhibit persistent exertional limitation that often is unexplained by conventional investigative studies.

Research question: What is the pathophysiologic mechanism of exercise intolerance that underlies the post-COVID-19 long-haul syndrome after COVID-19 in patients without cardiopulmonary disease?

Study design and methods: This study examined the systemic and pulmonary hemodynamics, ventilation, and gas exchange in 10 patients who recovered from COVID-19 and were without cardiopulmonary disease during invasive cardiopulmonary exercise testing (iCPET) and compared the results with those from 10 age- and sex-matched control participants. These data then were used to define potential reasons for exertional limitation in the cohort of patients who had recovered from COVID-19.

Results: The patients who had recovered from COVID-19 exhibited markedly reduced peak exercise aerobic capacity (oxygen consumption [VO2]) compared with control participants (70 ± 11% predicted vs 131 ± 45% predicted; P < .0001). This reduction in peak VO2 was associated with impaired systemic oxygen extraction (ie, narrow arterial-mixed venous oxygen content difference to arterial oxygen content ratio) compared with control participants (0.49 ± 0.1 vs 0.78 ± 0.1; P < .0001), despite a preserved peak cardiac index (7.8 ± 3.1 L/min vs 8.4±2.3 L/min; P > .05). Additionally, patients who had recovered from COVID-19 demonstrated greater ventilatory inefficiency (ie, abnormal ventilatory efficiency [VE/VCO2] slope: 35 ± 5 vs 27 ± 5; P = .01) compared with control participants without an increase in dead space ventilation.

Interpretation: Patients who have recovered from COVID-19 without cardiopulmonary disease demonstrate a marked reduction in peak VO2 from a peripheral rather than a central cardiac limit, along with an exaggerated hyperventilatory response during exercise.

Source: Singh I, Joseph P, Heerdt PM, Cullinan M, Lutchmansingh DD, Gulati M, Possick JD, Systrom DM, Waxman AB. Persistent Exertional Intolerance After COVID-19: Insights From Invasive Cardiopulmonary Exercise Testing. Chest. 2021 Aug 11:S0012-3692(21)03635-7. doi: 10.1016/j.chest.2021.08.010. Epub ahead of print. PMID: 34389297; PMCID: PMC8354807. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8354807/  (Full text)

Insights from Invasive Cardiopulmonary Exercise Testing of Patients with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome

Abstract:

Background

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) affects tens of millions worldwide; the causes of exertional intolerance are poorly understood. The ME/CFS label overlaps with postural orthostatic tachycardia (POTS) and fibromyalgia, and objective evidence of small fiber neuropathy (SFN) is reported in ∼50% of POTS and fibromyalgia patients.

Research Question

Can invasive cardiopulmonary exercise testing (iCPET) and PGP9.5-immunolabeled lower-leg skin biopsies inform the pathophysiology of ME/CFS exertional intolerance and potential relationships with SFN?

Study Design and Methods

We analyzed 1516 upright invasive iCPETs performed to investigate exertional intolerance. After excluding patients with intrinsic heart or lung disease and selecting those with right atrial pressures (RAP) <6.5 mmHg, results from 160 patients meeting ME/CFS criteria who had skin-biopsy test results were compared to 36 controls. Rest-to-peak changes in cardiac output (Qc) were compared to oxygen uptake (Qc/VO 2 slope) to identify participants with low, normal, or high pulmonary blood flow by Qc/VO 2 tertiles.

Results

During exercise, the 160 ME/CFS patients averaged lower RAP (1.9±2 vs. 8.3±1.5; P<0.0001) and peak VO 2 (80%±21 vs. 101.4%±17; P<0.0001) than controls. The low-flow tertile had lower peak Qc than the normal and high-flow tertiles (88.4±19% vs. 99.5±23.8% vs. 99.9±19.5% predicted; P<0.01). In contrast, systemic oxygen extraction was impaired in high-flow versus low and normal-flow participants (0.74±0.1% vs. 0.88±0.11 vs. 0.86±0.1; P<0.0001) in association with peripheral left-to-right shunting. Among the 160 ME/CFS patient biopsies, 31% was consistent with SFN (epidermal innervation ≤5.0% of predicted; P < 0.0001). Denervation severity did not correlate with exertional measures.

Interpretation

These results identify two types of peripheral neurovascular dysregulation that are biologically plausible contributors to ME/CFS exertional intolerance–depressed Qc from impaired venous return, and impaired peripheral oxygen extraction. In patients with small-fiber pathology, neuropathic dysregulation causing microvascular dilation may limit exertion by shunting oxygenated blood from capillary beds and reducing cardiac return.

Abbreviation:

Ca-vO2/[Hb] ( Arterial–mixed venous oxygen content difference/hemoglobin concentration), iCPET ( Invasive cardiopulmonary exercise test), NAM ( National Academy of Medicine, formerly the Institute of Medicine), ME/CFS ( Myalgic encephalomyelitis/chronic fatigue syndrome), MM ( Mitochondrial myopathy), mPAP ( Mean pulmonary artery pressure), PAWP ( Pulmonary arterial wedge pressure), PLF ( Preload failure), POTS ( Postural orthostatic tachycardia syndrome), PVR ( Pulmonary vascular resistance), RAP ( Right atrial pressure), Qc ( Cardiac output), SFN ( Small fiber neuropathy), VO2 ( Oxygen uptake), vPO2 ( Venous oxygen tension)

Source: Phillip Joseph, MD, Carlo Arevalo, MD, Rudolf K.F. Oliveira, MD, PhD, Donna Felsenstein, MD, Anne Louise Oaklander, MD, PhD, David M. Systrom, MD. Insights from Invasive Cardiopulmonary Exercise Testing of Patients with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome. February 09, 2021. DOI:https://doi.org/10.1016/j.chest.2021.01.082 https://journal.chestnet.org/article/S0012-3692(21)00256-7/fulltext

Unexplained exertional intolerance associated with impaired systemic oxygen extraction

Abstract:

PURPOSE: The clinical investigation of exertional intolerance generally focuses on cardiopulmonary diseases, while peripheral factors are often overlooked. We hypothesize that a subset of patients exists whose predominant exercise limitation is due to abnormal systemic oxygen extraction (SOE).

METHODS: We reviewed invasive cardiopulmonary exercise test (iCPET) results of 313 consecutive patients presenting with unexplained exertional intolerance. An exercise limit due to poor SOE was defined as peak exercise (Ca-vO2)/[Hb] ≤ 0.8 and VO2max < 80% predicted in the absence of a cardiac or pulmonary mechanical limit. Those with peak (Ca-vO2)/[Hb] > 0.8, VO2max ≥ 80%, and no cardiac or pulmonary limit were considered otherwise normal. The otherwise normal group was divided into hyperventilators (HV) and normals (NL). Hyperventilation was defined as peak PaCO2 < [1.5 × HCO3 + 6].

RESULTS: Prevalence of impaired SOE as the sole cause of exertional intolerance was 12.5% (32/257). At peak exercise, poor SOE and HV had less acidemic arterial blood compared to NL (pHa = 7.39 ± 0.05 vs. 7.38 ± 0.05 vs. 7.32 ± 0.02, p < 0.001), which was explained by relative hypocapnia (PaCO2 = 29.9 ± 5.4 mmHg vs. 31.6 ± 5.4 vs. 37.5 ± 3.4, p < 0.001). For a subset of poor SOE, this relative alkalemia, also seen in mixed venous blood, was associated with a normal PvO2 nadir (28 ± 2 mmHg vs. 26 ± 4, p = 0.627) but increased SvO2 at peak exercise (44.1 ± 5.2% vs. 31.4 ± 7.0, p < 0.001).

CONCLUSIONS: We identified a cohort of patients whose exercise limitation is due only to systemic oxygen extraction, due to either an intrinsic abnormality of skeletal muscle mitochondrion, limb muscle microcirculatory dysregulation, or hyperventilation and left shift the oxyhemoglobin dissociation curve.

Source: Melamed KH, Santos M, Oliveira RKF, Urbina MF, Felsenstein D, Opotowsky AR, Waxman AB, Systrom DM. Unexplained exertional intolerance associated with impaired systemic oxygen extraction. Eur J Appl Physiol. 2019 Sep 6. doi: 10.1007/s00421-019-04222-6. [Epub ahead of print] https://www.ncbi.nlm.nih.gov/pubmed/31493035