Acute effects of exercise with blood flow restriction on endothelial function in healthy young and older populations: a systematic review / Efeitos agudos do exercício com restrição do fluxo sanguíneo na função endotelial de jovens e idosos saudáveis: uma revisão sistemática

The objective of this review is to identify the acute effects of blood flow restriction (BFR) with vs without exercise on endothelial function in healthy individuals and the changes in endothelial function in young and older adults following different levels of exclusive BFR vs free flow. Systematic searches were performed in the following databases: PubMed, Web of Science, Scopus, and Cochrane Library, from inception to July 17, 2021. The studies included healthy individuals who underwent assessments of endothelial function before and after experimental protocols through endothelium-dependent flow-mediated dilatation. In total, 4890 studies were screened, and 6 studies of moderate-to-high methodological quality (Physiotherapy Evidence Database scores 6 ­ 10) including 82 subjects (aged 24 ­ 68 years) were eligible. Overall, flow-mediated dilatation increased in the non-cuffed arm immediately and 15 minutes after exercise, with no change in the cuffed arm (BFR of 60 ­ 80 mmHg). In protocols without exercise, cuff pressures of 25 ­ 30 mmHg applied for 30 minutes did not promote changes in the endothelial function, while those > 50 mmHg induced a dose-dependent attenuation of flow-mediated dilatation only in young individuals. A moderate level of BFR appears to have no effect on endothelial function after acute exercise. In non-exercise conditions, reductions in flow-mediated dilatation seem to result from increased retrograde shear provoked by cuff pressures ≥ 50 mmHg in young but not in older adults. An exercise-related increase in antegrade shear rate leads to a greater nitric oxide-mediated vasodilator response. However, BFR appears to attenuate this effect in young but not in older individuals. (AU)

O objetivo desta revisão foi identificar os efeitos agudos da restrição do fluxo sanguíneo (RFS) com vs. sem exercício na função endotelial de indivíduos saudáveis, bem como as alterações na função endotelial em jovens e idosos após diferentes níveis de RFS vs. fluxo livre. Pesquisas sistemáticas foram realizadas nas bases United States National Library of Medicine (PubMed), Web of Science, Scopus e Cochrane Library até 17 de julho de 2021. Os estudos incluíram indivíduos saudáveis que avaliaram a função endotelial antes e após protocolos experimentais, por meio da dilatação mediada por fluxo. Foi selecionado o total de 4.890 estudos, e foram elegíveis seis de moderada a alta qualidade metodológica (Physioterapy Evidence Database 6 ­ 10 pontos), incluindo 82 indivíduos (24 ­ 68 anos). No geral, a dilatação mediada por fluxo aumentou no braço sem manguito, imediatamente e 15 minutos após o exercício, sem alteração no braço com manguito (RFS de 60 ­ 80 mmHg). Em protocolos sem exercício, pressões do manguito de 25 ­ 30 mmHg aplicadas por 30 minutos não promoveram alterações na função endotelial, enquanto aquelas > 50 mmHg induziram uma atenuação dose-dependente da dilatação mediada por fluxo em indivíduos jovens. Um nível moderado de RFS parece não ter efeito na função endotelial após uma sessão de exercício. Em condições sem exercício, as reduções na dilatação mediada por fluxo parecem resultar do aumento do cisalhamento retrógrado provocado por pressões do manguito ≥ 50 mmHg em jovens, mas não em idosos. O aumento da taxa de cisalhamento anterógrado relacionada ao exercício leva a maior resposta vasodilatadora mediada pelo óxido nítrico. No entanto, a RFS parece atenuar esse efeito em jovens, mas não em . (AU)

INOCA: Evaluación no invasiva de los mecanismos fisiopatológicos mediante CZT-SPECT / INOCA: Non-Invasive Assessment of the Pathophysological Mechanisms Using CZT-SPECT

RESUMEN Introducción: Una de las causas propuestas del síndrome INOCA (por sus siglas en inglés: Ischemia with Non-Obstructive Coronary Arteries) es la disfunción microvascular (DMV), la cual puede evaluarse en forma no invasiva, mediante la cuantificación del flujo sanguíneo miocárdico (FSM) y la reserva de flujo miocárdica (RFM). Las imágenes de perfusión miocárdica (IPM) y dinámicas con CZT-SPECT en reposo - dipiridamol - y prueba de frio (PF), permiten establecer la presencia de DMV evaluando diferentes mecanismos fisiopatológicos: endotelio independiente o dependiente, respectivamente. Objetivos: Evaluar la utilidad de CZT-SPECT en el diagnóstico de DMV y los diferentes mecanismos patológicos involucrados, en pacientes con diagnóstico de INOCA. Material y métodos: Se incluyeron en forma prospectiva 93 pacientes consecutivos con diagnóstico de INOCA, a los que se les realizó IPM e imágenes dinámicas con CZT-SPECT en reposo-dipiridamol-PF. El FSM se cuantificó con el software 4DM. Se consideró respuesta anormal al dipiridamol una RFM menor a 2 y a la variación del FSM (∆FSM) menor a 1,5 con PF. Se definió DMV a la presencia de una o ambas respuestas anormales. Resultados: El CZT-SPECT detectó DMV en un 85% (n=79) de los pacientes con INOCA. El 42% tuvo respuesta anormal con ambos apremios mientras que el 43% restante, mostró una respuesta alterada del FSM sólo con PF. Conclusiones: El uso de CZT-SPECT empleando ambos apremios, permitió evaluar diferentes mecanismos fisiopatológicos que causan DMV presente en la mayoría de los pacientes con INOCA.

ABSTRACT Background: One of the causes of INOCA (Ischemia with Non- Obstructive Coronary Arteries) is microvascular dysfunction (MVD), which can be noninvasively assessed through the quantification of myocardial blood flow (MBF) and myocardial flow reserve (MFR). Dynamic myocardial perfusion imaging (MPI) by CZT-SPECT at rest, with dipyridamole stress test and cold pressor test (CPT) can establish the presence of two different pathophysiological mechanisms of MVD: endothelium-independent or endothelium-dependent, respectively. Objectives: The aim of this study was to evaluate the usefulness of CZT-SPECT for the diagnosis of MVD and the different mechanisms involved in patients with INOCA. Materials and Methods : A total of 93 consecutive INOCA patients were prospectively included and underwent dynamic MPI with CZT-SPECT at rest and with dipyridamole stress test and CPT. THe MBF was quantified using 4DM® software. A MFR response to dipyridamole <2, and changes in MBF (∆MBF) <1.5 with CPT were considered abnormal responses. MVD was defined in the presence of one abnormal response or both. Results: CZT-SPECT detected MVD in 85% (n=79) of the patients with INOCA. Forty-two percent had an abnormal response to both stressors while 43% presented an abnormal response of MBF only with CPT. Conclusion: The use of CZT-SPECT with both stress tests allowed the evaluation of different possible pathophysiological mechanisms of MVD present in most patients with INOCA.