Managing hematological cancer patients during the COVID-19 pandemic: an ESMO-EHA Interdisciplinary Expert Consensus

BACKGROUND

The COVID-19 pandemic has created enormous challenges for the clinical management of patients with hematological malignancies (HMs), raising questions about the optimal care of this patient group.

METHODS

This consensus manuscript aims at discussing clinical evidence and providing expert advice on statements related to the management of HMs in the COVID-19 pandemic. For this purpose, an international consortium was established including a steering committee, which prepared six working packages addressing significant clinical questions from the COVID-19 diagnosis, treatment, and mitigation strategies to specific HMs management in the pandemic. During a virtual consensus meeting, including global experts and lead by the European Society for Medical Oncology and the European Hematology Association, statements were discussed and voted upon. When a consensus could not be reached, the panel revised statements to develop consensual clinical guidance.

RESULTS AND CONCLUSION

The expert panel agreed on 33 statements, reflecting a consensus, which will guide clinical decision making for patients with hematological neoplasms during the COVID-19 pandemic.

From hepatitis C virus infection to B-cell lymphoma

In addition to liver disorders, hepatitis C virus (HCV) is also associated with extrahepatic immune manifestations and B-cell non-Hodgkin lymphoma (NHL), especially marginal zone lymphoma, de novo or transformed diffuse large B-cell lymphoma and to a lesser extent, follicular lymphoma. Epidemiological data and clinical observations argue for an association between HCV and lymphoproliferative disorders. The causative role of HCV in NHL has been further supported by the response to antiviral therapy. Pathophysiological processes at stake leading from HCV infection to overt lymphoma still need to be further elucidated. Based on reported biological studies, several mechanisms of transformation seem however to emerge. A strong body of evidence supports the hypothesis of an indirect transformation mechanism by which sustained antigenic stimulation leads from oligoclonal to monoclonal expansion and sometimes to frank lymphoma, mostly of marginal zone subtype. By infecting lymphocytes, HCV could play a direct role in cellular transformation, particularly in de novo large B-cell lymphoma. Finally, HCV is associated with follicular lymphoma in a subset of patients. In this setting, it may be hypothesized that inflammatory cytokines stimulate proliferation and transformation of IgH-BCL2 clones that are increased during chronic HCV infection. Unraveling the pathogenesis of HCV-related B-cell lymphoproliferation is of prime importance to optimize therapeutic strategies, especially with the recent development of new direct-acting antiviral drugs.

Dental Elements in Mature Teratomas of the Ovary: Scanning Electron Microscope Ultrastructure

Seventy-two teeth from 10 ovarian mature teratomas and 12 unerupted and erupted teeth from subjects aged 8 to 21 years were examined at the scanning electron microscope to evaluate the morphologic and histogenetic differences. The ultrastructure of the teratomatous teeth was similar to that of the corresponding orthotopic tissues. Despite this similarity the morphology of the teratomatous teeth was much less well defined, attesting to the inductive effect of the contiguous tissues that are normally present in the oral cavity.

The anti-lymphoma activity of antiviral therapy in HCV-associated B-cell non-Hodgkin lymphomas: a meta-analysis

Many epidemiological studies provide solid evidence for an association of chronic hepatitis C virus (HCV) infection with B-cell non-Hodgkin's lymphoma (B-NHL). However, the most convincing evidence for a causal relationship between HCV infection and lymphoma development is the observation of B-NHL regression after HCV eradication by antiviral therapy (AVT). We conducted a literature search to identify studies that included patients with HCV-associated B-NHL (HCV-NHL) who received AVT, with the intention to treat lymphoma and viral disease at the same time. The primary end point was the correlation of sustained virological response (SVR) under AVT with lymphoma response. Secondary end points were overall lymphoma response rates and HCV-NHL response in correlation with lymphoma subtypes. We included 20 studies that evaluated the efficacy of AVT in HCV-NHL (n = 254 patients). Overall lymphoma response rate through AVT was 73% [95%>confidence interval, (CI) 67-78%]. Throughout studies there was a strong association between SVR and lymphoma response (83% response rate, 95%>CI, 76-88%) compared to a failure in achieving SVR (53% response rate, 95%>CI, 39-67%, P = 0.0002). There was a trend towards favourable response for AVT in HCV-associated marginal zone lymphomas (response rate 81%, 95%>CI, 74-87%) compared to nonmarginal zone origin (response rate 71%, 95%>CI, 61-79%, P = 0.07). In conclusion, in the current meta-analysis, the overall response rate of HCV-NHL under AVT justifies the recommendation for AVT as first-line treatment in patients who do not need immediate conventional treatment. The strong correlation of SVR and lymphoma regression supports the hypothesis of a causal relationship of HCV and lymphomagenesis.

Antiviral treatment in patients with indolent B-cell lymphomas associated with HCV infection: a study of the Fondazione Italiana Linfomi

BACKGROUND

Tumor regression after antiviral therapy (AT) is in favor of an etiological role of hepatitis C virus (HCV) in non-Hodgkin's B-cell lymphomas (NHL).

PATIENTS AND METHODS

We carried out a cohort study of 704 consecutive HIV-negative, HCV-positive patients with indolent NHL diagnosed and treated from 1993 to 2009 in 39 centers of the Fondazione Italiana Linfomi; 134 patients were managed with AT for lymphoma control.

RESULTS

For entire cohort, 5-year overall survival (OS) was 78% [95% confidence interval (CI): 74%-82%] and 5-year progression-free survival (PFS) was 48% (95% CI: 44%-53%). In multivariate analysis, the use of AT during the patients' life had positive impact on OS. Forty-four of the 100 patients treated with first-line AT achieved a complete remission (CR) and 33 a partial response (PR). HCV-RNA clearance was achieved in 80 patients and was related to lymphoma response. At a median follow-up of 3.6 years, 5-year PFS was 63% (95% CI: 50%-73%). CR + PR rate was 85% with AT as second-line treatment.

CONCLUSION

AT produces HCV-RNA clearance and consequent tumor regression in most patients with HCV-related indolent NHL. AT used at any time is associated with improved OS. Consequently, AT can be considered an option for patients with indolent lymphomas who do not need immediate cytoreductive treatment.

ESMO Consensus conferences: guidelines on malignant lymphoma. part 2: marginal zone lymphoma, mantle cell lymphoma, peripheral T-cell lymphoma

To complement the existing treatment guidelines for all tumour types, ESMO organizes consensus conferences to focus on specific issues in each type of tumour. In this setting, a consensus conference on the management of lymphoma was held on 18 June 2011 in Lugano, next to the 11th International Conference on Malignant Lymphoma. The conference convened ∼30 experts from all around Europe, and selected six lymphoma entities to be addressed; for each of them, three to five open questions were to be addressed by the experts. For each question, a recommendation should be given by the panel, referring to the strength of the recommendation based on the level of evidence. This consensus report focuses on the three less common lymphoproliferative malignancies: marginal zone lymphoma, mantle cell lymphoma, and peripheral T-cell lymphomas. A first report had focused on diffuse large B-cell lymphoma, follicular lymphoma, and chronic lymphocytic leukaemia.

Mycosis fungoides: disease evolution of the "lion queen" revisited

Mycosis fungoides (MF), which represents the most common subtype of primary cutaneous T-cell lymphoma (CTCL), is an epidermotropic lymphoma included as an indolent form in the recent WHO/EORTC classification. From a clinical point of view, the classic disease progression usually is slow and takes over years or even decades, and characterized by the evolution from patches to more infiltrated plaques and eventually to tumours or erythroderma. However, the analysis of the MF disease course has been greatly impaired by the rarity of the disease, thus data about the time course of disease progression and pattern of relapse during time are not well known. In this review, a summary of published data on MF large patients cohorts will be presented, together with the results obtained by a retrospective analysis of clinical features and follow-up data of 1,422 MF patients diagnosed and followed-up from 1975 to 2010 in 27 Italian Centres (Italian Study Group for Cutaneous Lymphoma). From a clinical perspective, the amount of data support the relevance of a stage-tailored, differentiated follow-up strategy, in as much as the TNMB staging appears not only to be associated with different progression rates, but also shows as a new finding a relationship with different patterns of disease progression. From a biological point of view, there is the need to understand the molecular basis of the different clinical pathways of disease progression, to be able to potentially identify at an earlier phase of disease evolution, the patients who are more likely to develop erythroderma or tumour-stage progression. In conclusion, if MF is indeed a true "lion queen", as dermatologists we need to be expert and wise tamers to keep it under control.

A prospective study of 338 patients with polycythemia vera: the impact of JAK2 (V617F) allele burden and leukocytosis on fibrotic or leukemic disease transformation and vascular complications

We studied the relationship between JAK2 (V617F) mutant allele burden and clinical phenotype, disease progression and survival in patients with polycythemia vera (PV). The percentage of granulocyte mutant alleles was evaluated using a quantitative real-time polymerase chain reaction-based allelic discrimination assay. Of the 338 patients enrolled in this prospective study, 320 (94.7%) carried the JAK2 (V617F) mutation. Direct relationships were found between mutant allele burden and hemoglobin concentration (P=0.001), white blood cell count (P=0.001), spleen size (P=0.001) and age-adjusted bone marrow cellularity (P=0.002), while an inverse relationship was found with platelet count (P<0.001). During the study period, eight patients progressed to post-PV myelofibrosis (MF) (all carrying >50% mutant alleles), while 10 patients developed acute myeloid leukemia (AML). The mutant allele burden was significantly related to the risk of developing myelofibrosis (P=0.029) and retained its significant effect also in multivariable analysis (P=0.03). By contrast, the risk of developing AML as well as that of thrombosis was not significantly related to mutant allele burden. Leukocytosis did not affect thrombosis, MF, leukemia or survival. In conclusion, a JAK2 (V617F) allele burden >50% represents a risk factor for progression to MF in PV.

Platelet size distinguishes between inherited macrothrombocytopenias and immune thrombocytopenia

BACKGROUND

Distinguishing inherited thrombocytopenias from immune thrombocytopenia (ITP) can be difficult, and patients are therefore at risk of misdiagnosis and inappropriate treatments. Although it is known that the most common inherited forms of thrombocytopenia are characterized by increased platelet size, the diagnostic power of this feature has never been investigated.

OBJECTIVES

The aim of this study was to test the hypothesis that platelet size can be used to differentiate ITP from inherited macrothrombocytopenias.

PATIENTS/METHODS

We measured mean platelet volume (MPV) and mean platelet diameter (MPD), within 2 h of blood sampling, in 35 patients with inherited macrothrombocytopenias [15 MYH9-related disease (MYH9-RD), three biallelic and 17 monoallelic Bernard-Soulier syndrome (BSS)], and 56 with ITP. Using receiving operating characteristic analysis, we searched for the best cut-off values to differentiate between these conditions.

RESULTS

As expected, platelets were larger in inherited macrothrombocytopenias than in ITP. An MPD larger than 3.3 mum differentiated MYH9-RD and BSS from ITP with 0.89 sensitivity and 0.88 specificity, and an MPV larger than 12.4 fL had 0.83 sensitivity and 0.89 specificity. Combining MPD with MPV increased sensitivity and specificity to 0.97 and 0.89, respectively.

CONCLUSION

Platelet size evaluation by both an appropriate cell counter and blood film examination is useful for differentiating inherited macrothrombocytopenias from ITP.

Subcutaneous 'lipoma-like' B-cell lymphoma associated with HCV infection: a new presentation of primary extranodal marginal zone B-cell lymphoma of MALT

BACKGROUND

Hepatitis C virus (HCV) infection has been linked to lymphoproliferative disorders. Marginal zone B-cell lymphoma (MZL) represents one of the most frequent lymphoma subtypes associated with HCV infection. We describe an unusual subset of HCV-associated MZL characterized by subcutaneous presentation.

MATERIALS AND METHODS

A series of 12 HCV-positive patients presenting with subcutaneous nodules that revealed lymphoma infiltration at biopsy. Molecular analysis of immunoglobulin heavy chain (IGH) gene rearrangement and FISH investigations for t(11;18)(q21;q21) and t(14;18)(q32;q21) were carried out in nine patients.

RESULTS

The 12 patients (median age 69.5 years), all with positive HCV serology, presented with single or multiple subcutaneous nodules resembling lipomas. Histologically the lesions showed lymphoid infiltrates, consistent with extranodal MZL of mucosa-associated lymphoid tissue (MALT). Functional IGH gene rearrangements were identified in nine tested patients, with somatic mutations in 82%, indicating a histogenesis from germinal center-experienced B cells. The t(11;18) was found in two of nine cases. Staging did not show any other lymphoma localization. In two patients, a response was achieved with antiviral treatment. Extracutaneous spread to MALT sites occurred in a case.

CONCLUSIONS

Our observations expand the spectrum of HCV-associated lymphomas to include a subset of extranodal MZL characterized by a novel primary 'lipoma-like' subcutaneous presentation and indolent clinical course.

Blood p50 evaluation enhances diagnostic definition of isolated erythrocytosis

BACKGROUND

High oxygen-affinity haemoglobin variants and 2,3-diphosphoglycerate (2,3-DPG) deficiency are inherited diseases generating low tissue oxygen tension and erythropoietin-driven erythrocytosis, that characterizes the clinical phenotype of patients. Level of blood p50 (the oxygen tension at which haemoglobin is 50% saturated) is used to recognize these conditions.

OBJECTIVES

To define the clinical utility of blood p50 measurement in the diagnosis of isolated erythrocytosis.

SUBJECTS AND DESIGN

Venous blood p50 measurement was included in the diagnostic work-up of 102 consecutive patients with isolated erythrocytosis besides blood cell count, arterial oxygen saturation, serum erythropoietin measurement and screening for JAK2 mutations.

SETTING

Haematological Outpatient Section at University Hospital.

RESULTS

Seven patients had relative erythrocytosis. Among 95 patients with absolute erythrocytosis, 4 (4.2%) had decreased p50 level. The extended study of family members revealed a familial inheritance. Two families had haemoglobin variants already described as Haemoglobin Malmö and Haemoglobin San Diego. In one family, the proband had a new high oxygen-affinity haemoglobin variant (Haemoglobin Safi) resulting from the transversion C-->A at codon 81 of the alpha2-globin gene. In the last family, a deficiency of 2,3-DPG was found. Within the 91 patients with normal p50 values, 46 (51%) had secondary erythrocytosis, 13 (14%) polycythemia vera and 32 (35%) idiopathic erythrocytosis.

CONCLUSIONS

This study suggests that the investigation of blood p50 level may be useful to define diagnosis in patients with isolated erythrocytosis.

Immunochemotherapy with in vivo purging and autotransplant induces long clinical and molecular remission in advanced relapsed and refractory follicular lymphoma

BACKGROUND

To evaluate the clinical outcome of patients with relapsed or refractory follicular lymphoma treated with immunochemotherapy, in vivo purging and high-dose therapy with autotransplant.

PATIENTS AND METHODS

Sixty-four patients were enrolled in the trial. Primary end point was progression-free survival (PFS). Secondary end points were the in vivo purging effect on stem-cell harvest and the impact of molecular response on the outcome.

RESULTS

At enrollment, 59% of patients were PCR+ for bcl-2 rearrangement in bone marrow (PCR-informative). After the immunochemotherapy, before mobilization, 97% obtained complete response or partial response and 87% of patients informative for bcl-2 were molecularly negative. Sixty-one patients proceeded to in vivo purging and peripheral blood stem cell (PBSC) mobilization with rituximab and high-dose AraC. The median number of CD34+ cells collected was 16.6 x 10(6)/kg. Of 33 PCR-informative patients, the harvests resulted in PCR- in all. Fifty-eight patients received high-dose therapy and autotransplant of in vivo purged PBSC. After a median follow-up of 3.5 years, 41 patients are in complete remission. Five-year PFS is 59%.

CONCLUSION

This study demonstrates that patients with advanced relapsed or refractory follicular lymphoma treated with immunochemotherapy, in vivo purging and autotransplant may obtain long-lasting PFS. In bcl-2-positive patients, in vivo purging allows the harvest of lymphoma-free PBSC. Absence of the bcl-2 rearrangement after autotransplant is associated with persistent clinical remission.

Prevalence of HCV infection in nongastric marginal zone B-cell lymphoma of MALT

BACKGROUND

Hepatitis C virus (HCV) infection is frequently associated with B-cell non-Hodgkin's lymphomas. We investigated the prevalence of HCV infection in nongastric marginal zone lymphomas of mucosa-associated lymphoid tissue (MALT) in order to define the relationship between the viral infection and the presenting features, treatment, and outcome.

METHODS

We retrospectively studied 172 patients with a histological diagnosis of marginal zone B-cell lymphoma of MALT, except for stomach, and with available HCV serology, among a series of 208 patients.

RESULTS

HCV infection was documented in 60 patients (35%). Most HCV-positive patients (97%) showed a single MALT organ involvement. HCV-positive patients showed a more frequent involvement of skin (35%), salivary glands (25%), and orbit (15%). The majority of stage IV HCV-positive patients (71%) had a single MALT site with bone marrow involvement. The overall response rate was similar in HCV-positive (93%) and HCV-negative patients (87%). Overall survival (OS) and event-free survival (EFS) did not differ according to HCV infection. In multivariate analysis, advanced disease (stage III-IV) was associated with a poorer OS (P = 0.0001), irrespective of HCV serostatus.

CONCLUSIONS

This study shows that nongastric marginal zone lymphomas are characterized by a high prevalence of HCV infection. Patients with involvement of a single MALT site have the highest prevalence of HCV. HCV-positive nongastric lymphomas of MALT show an indolent course similar to HCV-negative patients and seem an ideal target for exploiting the antilymphoma activity of antiviral treatments.

Distinctive natural history in hepatitis C virus positive diffuse large B-cell lymphoma: analysis of 156 patients from northern Italy

BACKGROUND

Diffuse large B-cell lymphoma (DLBCL) has been correlated to hepatitis C virus (HCV) infection in few series, but characteristics and outcome of these patients remain undefined.

PATIENTS AND METHODS

We analyzed 156 previously untreated consecutive HCV-positive patients with DLBCL observed between 1994 and 2004 in three major institutions from northern Italy.

RESULTS

Median age at presentation was 63 years and 8% of patients had DLBCL transformed from low-grade lymphomas. Spleen was the most frequently involved extranodal site, followed by liver and stomach. Treatment was delivered with cure-intent in 132 patients, while the remaining 24 patients received monochemotherapy or radiotherapy alone due to old age or seriously impaired hepatic function. Only five patients (4%) had to discontinue chemotherapy due to severe liver function impairment. The addition of rituximab did not seem to affect patients' tolerance to treatment. Five-year overall survival of the entire cohort was 72%, while 5-year progression-free survival (PFS) of the 132 patients treated with cure-intent was 51%. Hepatitis B virus co-infection, advanced Ann Arbor stage and nodal origin of the tumor resulted the strongest adverse prognostic factors.

CONCLUSIONS

Patients with HCV-positive DLBCL share distinctive clinical features. Future studies should prospectively evaluate the association between HCV and aggressive lymphomas.

A model of in vivo purging with Rituximab and high-dose AraC in follicular and mantle cell lymphoma

We studied a model of in vivo purging with Rituximab and high-dose (HD) cytarabine in 14 patients with relapsed/refractory follicular lymphoma and two with refractory mantle cell lymphoma enrolled in a program of HD chemotherapy and autotransplant. After two courses of debulking immunochemotherapy with Rituximab, Vincristine and Cyclophosphamide, we used a combination of Rituximab, HD cytarabine and granulocyte colony-stimulating factor for peripheral blood stem cells (PBSC) mobilization. The median number of CD34+ cells collected was 14.69 x 10(6)/kg (range 5.74-73.2). Monitoring of peripheral CD19+ and CD20+ B cells prior to and throughout the purging period showed that a treatment with Rituximab, Vincristine and Cyclophosphamide results in a profound depletion of B cells in peripheral blood. B-cell depletion persists during mobilization with Rituximab and HD cytarabine allowing a collection of PBSC free of B cells (median CD19+ and CD20+ cells counts 0%). Of nine patients PCR positive for bcl-2 or bcl-1 in blood and marrow at the start of immunochemotherapy, all showed PCR-negative PBSC. In conclusion, in patients with indolent lymphoma, the concurrent administration of Rituximab and HD cytarabine is a safe and efficient method to obtain in vivo purged PBSC. Immunochemotherapy prior to mobilization produces B-cell depletion and seems to be a useful preparative step.

A sequence of immuno-chemotherapy with Rituximab, mobilization of in vivo purged stem cells, high-dose chemotherapy and autotransplant is an effective and non-toxic treatment for advanced follicular and mantle cell lymphoma

Options for relapsed/refractory indolent lymphoma include chemotherapy, immunotherapy and high-dose therapy with autologous support. The best combination of these approaches, however, is not defined. We treated 10 patients with relapsed/refractory follicular (n = 7) or mantle cell lymphoma (n = 3) using chemotherapy, immunotherapy, high-dose therapy and autotransplant in a sequence of four phases, each designed to play a specific role in tumour eradication. After the debulking with VACOP-B (doxorubicin, cyclophosphamide, etoposide, vincristine, prednisone, bleomycin) (phase 1), 9/10 patients responded but none achieved a molecular response. After the immuno-chemotherapy phase, which combined Rituximab with vincristine and cyclophosphamide, seven patients were in complete response (CR) and three in good partial response (PR), and all those with a molecular marker of disease showed a disappearance of the signal from marrow and blood. Phase 3, which coupled high-dose cytarabine with Rituximab, was effective in mobilizing an adequate number of progenitor cells that were polymerase chain reaction negative in all informative cases. Phase 4 consisted of high-dose therapy with autologous support followed by two doses of Rituximab. Autograft was performed in nine patients. The haematopoietic recovery was as expected. This sequence of chemotherapy, immuno-chemotherapy, stem cell mobilization with in vivo purging and autotransplant, organized in four blocks of treatment, was simple to administer and devoid of toxic effects. It permits rapid attainment of clinical and molecular response and enables the harvest of lymphoma-free peripheral blood progenitor cells even in heavily pretreated patients with relapsed or refractory disease.

Biochemical markers of bone disease in asymptomatic early stage multiple myeloma. A study on their role in identifying high risk patients

BACKGROUND AND OBJECTIVES

Skeletal involvement is typical of multiple myeloma (MM) and its occurrence increases with the progression of the disease. We performed a study to evaluate the clinical importance of osteocalcin (bone gla-protein, BGP) and bone alkaline phosphatase (b-AP) as indices of osteoblastic activity, and deoxypyridoline (DPD) as a marker of bone resorption.

DESIGN AND METHODS

Fifty-two MM patients, 39 patients with monoclonal gammopathy of undetermined significance (MGUS), and 30 normal controls entered the study. Of the 52 MM patients, 10 showed lytic lesions at standard X-rays and 42 did not; 21 were untreated and 31 had been treated with chemotherapy (combined with bisphophonates in 15). Of these last, 12 had progressive disease and 19 were in plateau phase.

RESULTS

DPD levels were higher in MM patients than in patients with MGUS or healthy controls (p = 0.0001 and p = 0.0008, respectively). No statistical differences were seen between patients with MGUS and healthy controls. BGP serum levels were significantly lower in MM patients than in MGUS patients (p = 0.001) or healthy controls (p = 0.001). b-AP was significantly higher in MGUS patients than in MM patients (p = 0.04). Biochemical parameters were analyzed in a continuous fashion and after dichotomization into low and high values with respect to normal ones. Abnormal high values of DPD showed statistically significant correlations with presence of osteolysis (p = 0.008), advanced stage (p = 0.03) and abnormal beta2-microglobulin (beta2M) values (p = 0.03), while DPD as a continuous variable correlated significantly only with the presence of osteolysis (p = 0.02). In contrast, neither BGP nor b-AP showed statistical correlations with the presence of lytic lesions, or with other clinical or laboratory parameters. In 15 patients followed with serial controls, modifications of DPD levels reflected bone disease status well. Of the 42 patients without radiologic evidence of skeletal lesions, 15 had abnormal DPD values. Spinal magnetic resonance imaging (MRI) showed initial lytic lesions in 10 of them.

INTERPRETATION AND CONCLUSIONS

Biochemical markers of bone metabolism are useful in evaluating and monitoring skeletal involvement in MM patients. They may help clinicians to identify: 1) from among patients without radiologic evidence of lytic lesions, those who deserve more accurate radiologic examinations (namely MRI); 2) from among asymptomatic patients, and in association with spinal MRI, those patients at higher risk of progression who might benefit from early treatment.

Peripheral arterial vascular function at altitude: sea-level natives versus Himalayan high-altitude natives

OBJECTIVES

Regulation of the vascular system may limit physical performance and contribute to adaptation to high altitude. We evaluated vascular function in 10 Himalayan high-altitude natives and 10 recently acclimatized sea-level natives at an altitude of 5,050 m.

METHODS

We registered electrocardiogram, blood flow velocity in the common femoral artery, and blood pressure in the radial artery using non-invasive methods under baseline conditions, and during maximal vasodilation after 2 min leg occlusion. Vascular mechanics were characterized by estimating pulse wave velocity and input impedance.

RESULTS

Pulse wave velocity and parameters of input impedance did not differ between groups under baseline conditions. In the post-ischemic period, the ratio between maximal hyperemic and baseline blood flow velocity was significantly higher in the high-altitude than in the sea-level natives (5.7 +/- 2.5 versus 3.8 +/- 1.2, P < 0.05). The leg vascular resistance decreased in the post-occlusive period without differences between groups. Characteristic impedance decreased in the post-ischemic period by about one third of the baseline level without differences between groups. The post-ischemic decrease of input impedance modulus was more marked in the high-altitude than in the sea-level natives at low frequencies (28 +/- 12 versus 6.4 +/- 20% at 2 Hz, P < 0.01).

CONCLUSIONS

Our results demonstrate a superior ability to increase blood flow velocity as a response to muscular ischemia in high-altitude natives compared to sea-level natives. This phenomenon may be associated with a more effective coupling between blood pressure and blood flow which is probably caused by differences in conduit vessel function.