Objectives: The Cardio-vascular reserve index (CVRI) had been empirically validated in diverse morbidities as a quantitative estimate of the reserve assumed by the cardiovascular reserve hypothesis. This work evaluates whether CVRI during exercise complies with the cardiovascular reserve hypothesis.
Design: Retrospective study based on a database of patients who underwent cardio-pulmonary exercise testing (CPX) for diverse indications.
Methods: Patient's physiological measurements were retrieved at four predefined CPX stages (rest, anaerobic threshold, peak exercise and after 2min of recovery). CVRI was individually calculated retrospectively at each stage.
Results: Mean CVRI at rest was 0.81, significantly higher (p<0.001) than at all other stages. CVRI decreased with exercise, reaching an average at peak exercise of 0.35, significant lower than at other stages (p<0.001) and very similar regardless of exercise capacity (mean CVRI 0.33-0.37 in 4 groups classified by exercise capacity, p>0.05). CVRI after 2min of recovery rose considerably, most in the group with the best exercise capacity and least in those with the lowest exercise capacity.
Conclusions: CVRI during exercise fits the pattern predicted by the cardiovascular reserve hypothesis. CVRI decreased with exercise reaching a minimum at peak exercise and rising with recovery. The CVRI nadir at peak exercise, similar across groups classified by exercise capacity, complies with the assumed exhaustion threshold. The clinical utility of CVRI should be further evaluated.
Keywords: Anaerobic threshold; Cardio-pulmonary exercise testing (CPX); Cardio-vascular reserve hypothesis; Cardio-vascular reserve index (CVRI); Exercise capacity; Peak exercise.
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